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I'm Jim Al-Khalili, a professor of
theoretical physics.

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But today, my brain isn't pondering
equations -

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it's being scanned.

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- You have about 160,000 kilometres of
wiring

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in about a kilo-and-a-half.

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So, enough to wrap around the Earth
four times,

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or take you halfway to the moon.
- Goodness me.

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Like everybody else's, my brain
contains about 100 billion neurons,

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and over 100 trillion connections.

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That's more than the stars in the
Milky Way.

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- This is what your head looks like
inside.

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- So, how did something so complex
actually evolve?

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Spanning hundreds of millions of
years,

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this story takes in the strangest of
creatures.

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So, there's a tiny brain?

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- Yes, exactly.

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- Now, thanks to the latest scientific
breakthroughs,

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we can tell the brain's extraordinary
story

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like never before.

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- That's the first whisper of a
revolution,

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a cognitive revolution.

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- MONKEY MAKES HIGH PITCHED CALL

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It's an epic tale...

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EXPLOSION

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..with amazing twists and turns.

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- Look how quick!
- Oh, my word!

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As we build artificial intelligence
vying to overtake our brains,

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I want to find out what makes the
thing in our skulls so special.

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This is my brain,

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and this is its 600 million year
story.

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To try to understand the beginning of
my brain's story...

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..I'm snorkelling off the west coast
of Italy.

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MUSIC: Concerto No.2 in G Minor by
Vivaldi

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This is home to some very
strange-looking animals.

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But go back some 560 million years,

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and you'd encounter the common
ancestor of us

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and many of these creatures.

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It had a rather special shape,

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probably a bit like this worm with a
head and tail,

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and left-right symmetry.

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This animal was, like us, bilateral,

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but it had something else too.

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Many scientists now believe that this
was the first animal

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to possess the basic building blocks
of the brain.

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It was in an epoch known as the
Ediacaran

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that these Bilateria first emerged.

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ENGINE RUMBLES

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To find out more about their early
brains,

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I've come to meet some scientists who
are working in these waters.

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- OK, pull up now and we will collect
everything.

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- They're pumping out the water from a
depth of ten metres,

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up through this filter, which lets
through all the tiny organisms

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that they don't want to catch,

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and it captures all the ones they want
to study.

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They're looking for zooplankton -

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animals like tiny worms that drift in
water.

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- So, this in here, it's hard to see,

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but this is zooplankton.

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We can analyse this under the
microscope.

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Small algae will go through, and the
zooplankton will stay in the filter.

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- Why is it studying this tiny worm
helps us understand

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the ancient early evolution of the
brain?

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- We have chosen to work on this worm,
because we were convinced

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that it has ancestral features, so
that it would show us,

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for example, characteristics of the
brain

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that are old, that have always been
existing in animals.

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- Like the first Bilateria, these
zooplankton

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have a tiny cluster of nerve cells in
their heads

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and a strand running down their
bodies.

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These cells co-ordinate muscle
movement and other organ behaviour.

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And, crucially, as well as
coordinating,

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early brains evolved ways of sensing

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and responding to their environment.

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- And so it was. So, the first thing
we found about this worm

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is that it uses light-sensitive cells,
photoreceptor cells,

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that it has in its brain.

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And these cells are the same to the
ones that we have in our retina,

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the rods and cones.

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And this was a big surprise, a big
finding

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that these are the same photoreceptor
cells.

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- So, these are cells that are
activated,

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that send signals to the brain, when
light impacts on them?

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- Exactly. We have these in our eyes.

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So, whenever we see light, these cells
are activated

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and signal to the brain that there is
light.

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And the very same cells exist in this
worm.

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- Back on dry land, another member of
the team shows me

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what these worms can tell us about
early brains.

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Aha!

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- Here it is.

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So, this is a young juvenile.

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- Right. So, how big is this?

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Is it like, maybe, a millimetre or
two?

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- This is two millimetres.
- OK.

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- And it has, on the front, a nice
head.

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You can see the fangs of the animal,

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where they take up food.

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You can even see some movement

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inside, these little dark dots, which
are the eyes.

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- So, it has four eyes?

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- It has four eyes.

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And you can see these dark speckles,

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these are the pigments of the eye.

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- Inside these simple eyes are
molecules called opsins.

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When light hits opsins,

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they trigger an electrical signal,

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which can make the worm move.

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Can you show me how they react to
light, then?

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- Yes. So, here you see the larvae
swimming.

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And then we switch on a directional
light stimulus

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on this side of the chamber.

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You see when the light comes on,

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and they start to move to the light.

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- Oh, I see. You're replacing sunlight
with your artificial light,

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and having the worm move towards it?

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- Yes. We provide this directional
light cue here, from the side.

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- The worm isn't seeing, thinking,

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or responding like we do, though.

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It has a simple nervous system,

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that makes it move when light strikes
its opsins.

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What does that tell us about the early
evolution

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of vision?

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- We think that the first eyes were
just, in fact, very simple -

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a few cells, able to tell the
direction of light.

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And this kind of mechanism was
probably there already

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in the common ancestor, last common
ancestor of the Bilateria animals,

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around 540 million years ago.

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- At about the same time,

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other senses developed too.

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For instance, cells that could respond
to nutrients -

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the forerunners of smell and taste.

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But these first bilateral animals

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also needed a way of sending sensory
signals

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around their bodies to control muscles
and organs.

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For that, they used a special type of
cell -

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the animal world's fibreoptic cable, a
nerve cell,

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or neuron.

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It's taken over 100 years for
scientists to understand the neuron.

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Much of that story happened just down
the coast here in Italy,

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at a true landmark in the history of
science.

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This is the Stazione Zoologica in
Naples.

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It was founded in the 1870s by
zoologist Anton Dohrn.

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Anton Dohrn was an early and
passionate adopter

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of Charles Darwin's theory of
evolution by natural selection,

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and that passion drove him to create a
station for scientists

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to study marine life.

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For his location, he chose Naples,
because...

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Well, Naples.

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Dohrn built this impressive laboratory
right on the beach

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with easy access to the Mediterranean,

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and facilities to study all kinds of
sea creatures.

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To explore how neurons and nervous
systems worked,

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he had his team make some exquisitely
detailed

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and beautiful illustrations.

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Dr Graziano Fiorito showed me some
examples.

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- There was a strong tradition

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by...by Dohrn

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of supporting the study

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of various organisms.

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- Wonderful. So, these are
illustrations made for

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this journal, which is...

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..Fauna und Flora.

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1896.

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- They were interested not only in the
shape of the animal, the organs,

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but in the nervous system,

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how the nervous system is organised.

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- Then, in 1932, here at the Stazione,

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a British scientist called John
Zachary Young, or JZ,

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made a breakthrough in understanding
how the neuron works.

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Scientists had previously suspected
electricity was involved

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in neuron signals,

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but these cells were always too small
and thin to really study.

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Then JZ found an exception -

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squid possesses neurons so long and
thick,

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they're actually visible to the naked
eye.

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- This is a classic video, where JZ
was showing how to dissect a squid.

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He's now removing some part of the
organs, the gills,

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in order to reveal this network.

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You see?
- Right.

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JZ realised that because these neurons
were so large,

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he could isolate one with the correct
dissection techniques.

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So, these are all nerves, each one of
those lines?

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- Nerves. Yeah. And finally, this is
the giant single nerve.

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- Scientists used electrodes

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to measure what was happening inside
the neuron,

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and this led to the discovery of
precisely how electrical signals

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travelled along it.

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Would you say this was the beginning
of

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modern neuroscience?
- Yes.

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JZ Young published this paper in 1939.

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And this was the emergence, I would
say, of neuroscience.

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- We now understand that nerve cells,
or neurons,

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are the building blocks of all brains.

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Neurons take signals from molecules
like light-sensitive opsins,

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and transmit them through the body as
electrical pulses.

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But how exactly do they do that?

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Most neurons consist of three basic
parts.

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Dendrites, these branching filaments
that pick up the signals,

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a cell body that processes the signal

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and a long strand called an axon

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that carries the signal to other
cells.

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But what's really incredible is just
how fast the signal can move.

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Let me show you the patella reflex,

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or the knee jerk reaction.

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My director, Tim, has kindly
volunteered here.

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So, look what happens when I do this.

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Hitting the tendon triggers a nerve in
the thigh,

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and a signal travels to the spine and
back,

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and the thigh muscles jerks.

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Watch how fast it is.

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It takes about 18 milliseconds,

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which means the signal is travelling
at about 200km an hour.

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Electricity doesn't flow along the
whole length of an axon,

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as it might do in a copper wire.

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Instead, the signal starts when a tiny
channel

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at the beginning of the axon opens,

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allowing electrically-charged
particles to flow through it.

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This then triggers other channels to
open a little further along.

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It's rather like a domino effect.

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Each tile moves very little,

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but the ripple effect travels rapidly.

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Same in the axon - the charged
particles themselves hardly move,

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but the signal races down.

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Ultimately, what we see is a pulse of
electricity

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passing from one end to the other,

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and it all happens in the blink of an
eye.

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But what makes the brain and nervous
system so flexible

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is that neurons signal other neurons,

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creating a complex network.

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They communicate across a tiny gap
called a synapse.

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Here, the electrical signal triggers
the release of a chemical

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called a neurotransmitter,

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which crosses from one neuron to
another.

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In this way, signals can cascade
through your brain and body.

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And new technology means scientists
can see and hear neurons at work.

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In Boston Harbour, on the Eastern
Seaboard of the United States,

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a fresh haul of tasty crabs is just
in.

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But before they reach the plate of a
hungry diner,

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some of these crabs are being diverted
for scientific research.

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- So, what Kyra's doing now is,

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she's putting out the stomatogastric
nervous system.

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- Professor Eve Marder runs this lab
at Brandeis University near Boston.

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- Once it's pinned down flat,

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she'll place recording electrodes on
the nerves that will allow her

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to identify the neurons and record the
motor patterns.

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- Eve's team are measuring electrical
activity in the neurons.

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- These very fine white lines are the
nerves themselves,

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and you can see how delicate they are.

249
00:15:31,300 --> 00:15:33,700
- LOW CHIRRUPING

250
00:15:33,700 --> 00:15:38,860
And the technology here means those
signals are converted into sound.

251
00:15:38,860 --> 00:15:42,420
CHIRRUPING CONTINUES

252
00:15:42,420 --> 00:15:46,620
- So, using the electrodes to record
the activity of the nerves,

253
00:15:46,620 --> 00:15:49,460
and you can hear that the rhythm is
going pretty fast right now.

254
00:15:49,460 --> 00:15:52,660
You're hearing that nice rhythm of
bah-dub, bah-dub, bah-dub, bah-dub.

255
00:15:52,660 --> 00:15:56,260
It's the circuit doing its thing.

256
00:15:59,140 --> 00:16:03,740
- This is a real-time representation
of the crab's nervous system

257
00:16:03,740 --> 00:16:06,100
actually sending messages,

258
00:16:06,100 --> 00:16:09,140
much like the ones that control our
bodily functions.

259
00:16:11,020 --> 00:16:14,620
But in an era of fear about climate
change,

260
00:16:14,620 --> 00:16:16,860
with temperatures set to rise,

261
00:16:16,860 --> 00:16:19,700
the discovery also has a worrying
aspect -

262
00:16:19,700 --> 00:16:24,620
neurons are prone to fail as their
surroundings warm up.

263
00:16:24,620 --> 00:16:27,340
- Every human neurological disorder

264
00:16:27,340 --> 00:16:30,060
is exacerbated by high temperature.

265
00:16:30,060 --> 00:16:34,420
The fact that poor people and ill
people

266
00:16:34,420 --> 00:16:39,780
are less likely to be in environments
where they can regulate

267
00:16:39,780 --> 00:16:44,060
their room temperatures, and therefore
their body temperatures,

268
00:16:44,060 --> 00:16:47,780
means that we're potentially heading
into a major health crisis.

269
00:16:49,460 --> 00:16:54,060
- This fragility means we should never
take neurons for granted.

270
00:16:54,060 --> 00:16:58,020
After all, these cells carrying
billions of pulses

271
00:16:58,020 --> 00:17:01,340
around our brains and bodies every
second

272
00:17:01,340 --> 00:17:04,900
arguably make us who we are.

273
00:17:04,900 --> 00:17:10,260
All the thoughts and all the dreams of
the entire human race

274
00:17:10,260 --> 00:17:14,140
are just made up of these tiny
electric signals

275
00:17:14,140 --> 00:17:16,220
racing along neurons.

276
00:17:16,220 --> 00:17:17,900
It's mind-boggling.

277
00:17:20,580 --> 00:17:23,100
For neurons to become really
effective,

278
00:17:23,100 --> 00:17:25,540
and lead to brains like ours,

279
00:17:25,540 --> 00:17:28,980
they had to do more than simply carry
signals.

280
00:17:28,980 --> 00:17:31,980
They had to take context into account
-

281
00:17:31,980 --> 00:17:35,740
respond to stimuli in much more
nuanced ways.

282
00:17:37,420 --> 00:17:41,460
To do that, evolution picked a group
of ancient proteins

283
00:17:41,460 --> 00:17:44,100
and found a new use for them -

284
00:17:44,100 --> 00:17:46,660
neuropeptides.

285
00:17:46,660 --> 00:17:50,340
Let me give you a sense of the rather
subtle ways these work.

286
00:17:52,860 --> 00:17:55,060
You see, depending on circumstances,

287
00:17:55,060 --> 00:17:59,500
the same thing could be either good or
to be avoided.

288
00:17:59,500 --> 00:18:02,700
Let me give you an example of how
important this is, even now.

289
00:18:05,020 --> 00:18:08,700
Think about how you might respond to a
delicious-looking cake.

290
00:18:09,780 --> 00:18:12,980
If I haven't eaten for a while, then I
really just want to tuck in.

291
00:18:13,980 --> 00:18:16,740
But if I've just had a big meal,

292
00:18:16,740 --> 00:18:19,380
then it looks a whole lot less
appetising.

293
00:18:20,700 --> 00:18:23,020
And if I've just been sick from food
poisoning,

294
00:18:23,020 --> 00:18:24,980
then the same cake can look repulsive.

295
00:18:26,140 --> 00:18:29,620
Our brains have a way of adapting our
behaviour

296
00:18:29,620 --> 00:18:33,180
by reprogramming what the neurons tell
us to do.

297
00:18:33,180 --> 00:18:39,140
These subtle alterations of when and
why neurons fire

298
00:18:39,140 --> 00:18:41,340
are controlled by neuropeptides.

299
00:18:42,820 --> 00:18:44,780
For instance, they change our
behaviour

300
00:18:44,780 --> 00:18:47,940
when we're with friends rather than
strangers,

301
00:18:47,940 --> 00:18:51,740
or how a mother acts when she's with
her new baby.

302
00:18:51,740 --> 00:18:55,900
All these new behaviours happen
slowly, over minutes or hours,

303
00:18:55,900 --> 00:18:59,700
and are very different from the rapid
response to, say,

304
00:18:59,700 --> 00:19:01,460
touching something hot.

305
00:19:04,060 --> 00:19:08,980
Professor Cori Bargmann, at
Rockefeller University in New York,

306
00:19:08,980 --> 00:19:15,060
has made it her life's work to study
how neuropeptides alter behaviour,

307
00:19:15,060 --> 00:19:18,140
and to understand how they evolved.

308
00:19:18,140 --> 00:19:20,580
- The neuropeptides are very old.

309
00:19:20,580 --> 00:19:23,780
This system is one of the first ways
that the nervous system functioned,

310
00:19:23,780 --> 00:19:26,660
even before there was sort of a
centralised brain,

311
00:19:26,660 --> 00:19:29,700
while it was still kind of fuzzy and
distributed.

312
00:19:29,700 --> 00:19:32,340
- To understand neuropeptides,

313
00:19:32,340 --> 00:19:36,340
Cori studied a tiny worm known as C.
elegans.

314
00:19:37,740 --> 00:19:40,500
- This is a single adult C. elegans,

315
00:19:40,500 --> 00:19:42,860
and here's a little adolescent next to
her,

316
00:19:42,860 --> 00:19:45,060
moving around in real-time.

317
00:19:45,060 --> 00:19:48,140
Because she's transparent, under the
right circumstances,

318
00:19:48,140 --> 00:19:50,420
you can see every neuron in her
nervous system.

319
00:19:53,300 --> 00:19:57,900
- C. elegans has precisely 302
neurons,

320
00:19:57,900 --> 00:20:01,980
and scientists have now mapped exactly
how each one

321
00:20:01,980 --> 00:20:03,580
connects to the others.

322
00:20:05,260 --> 00:20:09,260
Cori's research examines how
neuropeptides influence

323
00:20:09,260 --> 00:20:11,580
this basic nervous system

324
00:20:11,580 --> 00:20:15,100
and enable the worms to have complex
behaviours,

325
00:20:15,100 --> 00:20:17,740
like socialising or courting.

326
00:20:19,460 --> 00:20:22,460
- Some of the worms were very
interested in associating

327
00:20:22,460 --> 00:20:25,620
with other worms, and we can actually
see these behaviours

328
00:20:25,620 --> 00:20:26,900
here in this movie.

329
00:20:26,900 --> 00:20:30,140
And what you can see is that they're
tending to hang out together

330
00:20:30,140 --> 00:20:33,100
in these little groups, and this is an
aggregation behaviour.

331
00:20:33,100 --> 00:20:35,900
Aggregation behaviour is very common
in animals.

332
00:20:35,900 --> 00:20:39,220
Animals often associate with other
animals in their same species.

333
00:20:39,220 --> 00:20:42,940
That could be called herding behaviour
in...in sheep,

334
00:20:42,940 --> 00:20:45,660
or it could be called schooling
behaviour in fish.

335
00:20:45,660 --> 00:20:48,500
And we see exactly this, even in these
very simple worms.

336
00:20:52,500 --> 00:20:56,460
- Normally, when worms bump into
things, they move away.

337
00:20:56,460 --> 00:21:01,660
But Cori found that sometimes,
something very different happened.

338
00:21:01,660 --> 00:21:06,740
A neuropeptide you might have heard
of, called oxytocin, was released,

339
00:21:06,740 --> 00:21:09,580
which changed how the neurons work

340
00:21:09,580 --> 00:21:12,020
and how the worms behave.

341
00:21:13,900 --> 00:21:18,500
- Oxytocin is required for mating
behaviours in C. elegans.

342
00:21:18,500 --> 00:21:22,580
I'm showing you here a mating pair of
a male C. elegans

343
00:21:22,580 --> 00:21:24,740
and its female-like partner.

344
00:21:24,740 --> 00:21:28,340
And in the male, there's a single
neuron,

345
00:21:28,340 --> 00:21:31,220
it's this bright spot here that looks
almost like an eye,

346
00:21:31,220 --> 00:21:35,380
that's the neuron that's making
oxytocin when the animal was mating.

347
00:21:35,380 --> 00:21:38,060
And so, this male is resending his
behaviours,

348
00:21:38,060 --> 00:21:40,380
so that in the presence of a mating
partner,

349
00:21:40,380 --> 00:21:44,540
he'll respond appropriately for this,
for the next five minutes.

350
00:21:44,540 --> 00:21:47,740
And then, once she disappears again,
he'll go back to the other kinds

351
00:21:47,740 --> 00:21:49,860
of exploratory behaviours that he's
doing.

352
00:21:51,580 --> 00:21:54,100
- But what really surprised Cori

353
00:21:54,100 --> 00:21:58,740
was how neuropeptides like oxytocin
changed behaviour

354
00:21:58,740 --> 00:22:02,020
in almost all living things.

355
00:22:02,020 --> 00:22:04,180
- We found that there was an oxytocin
in ants,

356
00:22:04,180 --> 00:22:06,020
which of course are a social species,

357
00:22:06,020 --> 00:22:09,060
and it's involved in some of their
social behaviours as well.

358
00:22:09,060 --> 00:22:11,300
- And in mammals like us,

359
00:22:11,300 --> 00:22:14,380
oxytocin has developed a crucial role.

360
00:22:14,380 --> 00:22:18,620
- Oxytocin is released when a female
mammal gives birth.

361
00:22:18,620 --> 00:22:20,540
It helps to rewire the mother's brain,

362
00:22:20,540 --> 00:22:23,940
to stimulate bonding between the
mother and her offspring.

363
00:22:23,940 --> 00:22:26,500
It's being able to flip from one state
into another.

364
00:22:26,500 --> 00:22:29,580
And we all know that experience in our
own lives,

365
00:22:29,580 --> 00:22:32,260
we all know how emotional states are
changing our behaviours

366
00:22:32,260 --> 00:22:33,620
on a moment-to-moment basis.

367
00:22:36,900 --> 00:22:40,460
- In our brains, neuropeptides control
our moods -

368
00:22:40,460 --> 00:22:43,420
bonding, love, anger, sex.

369
00:22:43,420 --> 00:22:47,500
In fact, modern drugs like Ozempic,
which is set to revolutionise

370
00:22:47,500 --> 00:22:52,020
obesity, is linked to the action of
the neuropeptide GLP-1,

371
00:22:52,020 --> 00:22:54,340
which controls appetite.

372
00:22:54,340 --> 00:22:58,740
It's quite incredible that so much of
our behaviour

373
00:22:58,740 --> 00:23:02,220
is based on these proteins inside our
brains

374
00:23:02,220 --> 00:23:05,740
that evolved hundreds of millions of
years ago.

375
00:23:08,860 --> 00:23:11,900
The next huge leap in the brain's
development

376
00:23:11,900 --> 00:23:15,540
happened about 530 million years ago,

377
00:23:15,540 --> 00:23:19,700
in what's known as the Cambrian
Explosion.

378
00:23:19,700 --> 00:23:23,580
Evolution went into overdrive.

379
00:23:23,580 --> 00:23:28,020
There was a huge burst of new,
strange-looking species,

380
00:23:28,020 --> 00:23:30,860
big creatures with shells,

381
00:23:30,860 --> 00:23:34,700
thorns, fierce claws and hooks.

382
00:23:36,660 --> 00:23:41,620
And one particular adaptation that
would have far-reaching consequences

383
00:23:41,620 --> 00:23:43,540
for our brains.

384
00:23:45,100 --> 00:23:47,780
I'm about to show you something really
exciting.

385
00:23:47,780 --> 00:23:50,380
Hi, Filomena.
- Hi.

386
00:23:50,380 --> 00:23:53,340
- Can I have a look at...
- Yes.
- ..what's in that dish?

387
00:23:53,340 --> 00:23:56,980
Thank you. I'll put it on this dark
background.

388
00:23:59,100 --> 00:24:01,380
What's inside here is really rare.

389
00:24:02,740 --> 00:24:04,940
These long creatures,

390
00:24:04,940 --> 00:24:07,540
that's called amphioxus.

391
00:24:07,540 --> 00:24:12,140
It's regarded to be very similar to
the earliest common ancestor,

392
00:24:12,140 --> 00:24:14,220
about 500 million years ago,

393
00:24:14,220 --> 00:24:17,420
that marked the transition to the
first vertebrates.

394
00:24:18,820 --> 00:24:22,900
Maybe we can have a closer look...
- Yes.
- ..under the microscope?

395
00:24:28,580 --> 00:24:31,500
- Here, we have the adult amphioxus.

396
00:24:31,500 --> 00:24:35,540
Here, we can see the anterior part,
the head.

397
00:24:35,540 --> 00:24:38,100
Here, the posterior part, the tail.

398
00:24:39,260 --> 00:24:43,140
- And from head to tail, the nerve
cord has been supplemented

399
00:24:43,140 --> 00:24:46,700
with a string of cartilage and bone -

400
00:24:46,700 --> 00:24:48,900
a primitive spine.

401
00:24:48,900 --> 00:24:52,740
This gave the ancient version of
amphioxus an advantage

402
00:24:52,740 --> 00:24:54,740
over earlier Bilateria -

403
00:24:54,740 --> 00:24:58,260
it would allow brains to get bigger.

404
00:24:58,260 --> 00:25:01,140
So, there's a tiny brain?

405
00:25:01,140 --> 00:25:02,500
- Yes, exactly.

406
00:25:02,500 --> 00:25:04,940
If we go more in...

407
00:25:06,500 --> 00:25:07,900
..we can see.

408
00:25:09,100 --> 00:25:13,620
Here, we have this enlargement.

409
00:25:13,620 --> 00:25:16,540
And here, there is the brain of
amphioxus.

410
00:25:19,420 --> 00:25:23,660
- The rigidity of spinal cords and
early skeletons

411
00:25:23,660 --> 00:25:28,500
allowed vertebrates and their brains
to grow.

412
00:25:28,500 --> 00:25:31,540
Amphioxi have 20,000 neurons.

413
00:25:34,300 --> 00:25:38,380
You can get a sense of the advantages
of having a smarter brain

414
00:25:38,380 --> 00:25:42,820
and internal spine and skeleton by
watching this fish tank.

415
00:25:45,660 --> 00:25:49,100
Right now, this looks like a perfectly
peaceful habitat.

416
00:25:49,100 --> 00:25:53,500
Fish gently moving about, calmly,
harmoniously

417
00:25:53,500 --> 00:25:56,380
but that's because they're not
thinking about their lunch.

418
00:25:57,620 --> 00:25:59,940
Let the feeding commence.

419
00:26:01,540 --> 00:26:02,980
Vertebrates of all kinds

420
00:26:02,980 --> 00:26:06,020
proliferated in the Cambrian
Explosion.

421
00:26:06,020 --> 00:26:08,820
Thanks to their speed and
manoeuvrability,

422
00:26:08,820 --> 00:26:11,420
the ones with spines and bigger brains

423
00:26:11,420 --> 00:26:14,700
were great at both hunting and
escaping.

424
00:26:18,220 --> 00:26:19,900
- The main scan is basically ready.

425
00:26:21,180 --> 00:26:24,500
- At the MRI scanner at University
College London,

426
00:26:24,500 --> 00:26:27,500
I'm being shown the debt my brain owes

427
00:26:27,500 --> 00:26:30,340
to my early vertebrate ancestors.

428
00:26:31,860 --> 00:26:36,220
- That's your spinal cord, coming up
into your brain stem.

429
00:26:36,220 --> 00:26:39,620
Brain stem is one of the sort of
evolutionarily older parts

430
00:26:39,620 --> 00:26:42,220
of the brain that keeps your heart
beating, your lungs pumping,

431
00:26:42,220 --> 00:26:43,620
moves your eyes around.

432
00:26:43,620 --> 00:26:45,500
So, lots of important things.

433
00:26:46,540 --> 00:26:49,660
- Another crucial component of
vertebrate brains

434
00:26:49,660 --> 00:26:54,180
is the hippocampus, which we use for
memory formation.

435
00:26:54,180 --> 00:26:59,340
- The hippocampus is a little C-like
structure that shows up here.

436
00:26:59,340 --> 00:27:02,260
I can see it because I'm used to
looking at hippocampi,

437
00:27:02,260 --> 00:27:03,860
but it may be a little bit
challenging.

438
00:27:03,860 --> 00:27:06,660
It's sitting just below your amygdala,

439
00:27:06,660 --> 00:27:09,740
which is part of the brain that's sort
of an emotional centre.

440
00:27:11,100 --> 00:27:13,620
- This new, large vertebrate brain

441
00:27:13,620 --> 00:27:18,540
was matched by an increase in body
complexity and size too,

442
00:27:18,540 --> 00:27:22,500
and this meant the brain and body
needed more sophisticated

443
00:27:22,500 --> 00:27:24,500
internal communication.

444
00:27:26,300 --> 00:27:29,820
Brains not only had to get better and
better at sensing

445
00:27:29,820 --> 00:27:32,460
what was going on in the world
outside,

446
00:27:32,460 --> 00:27:35,700
but also what was going on inside the
body.

447
00:27:35,700 --> 00:27:39,300
And one very important way they do
this is fascinating.

448
00:27:39,300 --> 00:27:44,060
They use a molecule that works a bit
like a telegraph key

449
00:27:44,060 --> 00:27:45,700
sending Morse Code.

450
00:27:45,700 --> 00:27:48,060
MACHINE BEEPS

451
00:27:48,060 --> 00:27:50,540
A telegraph key is pretty simple.

452
00:27:50,540 --> 00:27:55,500
A battery connects across a lever arm
and a contact below.

453
00:27:55,500 --> 00:27:58,020
So, when I press down on the arm,

454
00:27:58,020 --> 00:28:01,780
I complete the circuit and a current
flows through the wire,

455
00:28:01,780 --> 00:28:03,820
enabling me to send a message.

456
00:28:03,820 --> 00:28:06,060
BEEPING

457
00:28:06,060 --> 00:28:08,260
In essence, a mechanical force,

458
00:28:08,260 --> 00:28:10,780
in this case the pressure of my
finger,

459
00:28:10,780 --> 00:28:13,300
is triggering an electrical signal.

460
00:28:13,300 --> 00:28:15,300
MACHINE BEEPS

461
00:28:15,300 --> 00:28:18,860
For years, scientists suspected
something similar was happening

462
00:28:18,860 --> 00:28:21,260
in our nervous system.

463
00:28:21,260 --> 00:28:24,620
Something was transforming mechanical
force

464
00:28:24,620 --> 00:28:27,700
into some sort of signal to the brain.

465
00:28:27,700 --> 00:28:32,060
For instance, as a stomach fills, its
walls stretch,

466
00:28:32,060 --> 00:28:36,260
and somehow the animal knew it didn't
need to eat for a while.

467
00:28:36,260 --> 00:28:38,620
But how did this actually work?

468
00:28:40,540 --> 00:28:46,860
The answer was finally discovered in
2010 by Professor Ardem Patapoutian,

469
00:28:46,860 --> 00:28:50,700
at Scripps Research Institute in
Southern California.

470
00:28:50,700 --> 00:28:55,540
- We're used to thinking about taste
and smell, sensing chemicals.

471
00:28:55,540 --> 00:28:58,140
But this is actually sensing physics,
right?

472
00:28:58,140 --> 00:29:00,580
It's mechanical forces, pressure.

473
00:29:00,580 --> 00:29:03,500
You have to turn this physical
stimulus into an electrical

474
00:29:03,500 --> 00:29:08,300
or chemical signal that neurons would
understand,

475
00:29:08,300 --> 00:29:12,020
and this transformation has been a big
mystery.

476
00:29:12,020 --> 00:29:13,740
- BEEPING

477
00:29:13,740 --> 00:29:17,940
The challenge was to find a molecule
that, like a telegraph key,

478
00:29:17,940 --> 00:29:20,820
was triggered by mechanical pressure

479
00:29:20,820 --> 00:29:23,020
to send an electrical signal.

480
00:29:23,020 --> 00:29:28,700
So, Ardem's team built an ingenious
probe that gently applied pressure

481
00:29:28,700 --> 00:29:32,660
to cells just a few thousandths of a
millimetre across.

482
00:29:34,220 --> 00:29:36,740
- We have a video here of the cell
poking assay

483
00:29:36,740 --> 00:29:38,420
under high magnification.

484
00:29:38,420 --> 00:29:41,460
And so, what we're doing here is,
using that to deliver

485
00:29:41,460 --> 00:29:45,580
sub-micron - so very, very small
fractions of a millimetre -

486
00:29:45,580 --> 00:29:49,540
indentations to this cell that's
sitting on the dish right here.

487
00:29:52,260 --> 00:29:55,540
- After nearly a year of poking and
prodding...

488
00:29:57,300 --> 00:30:02,060
..they finally found a single molecule
on the cell's membrane,

489
00:30:02,060 --> 00:30:06,300
which triggered a tiny electric
current when pressed.

490
00:30:07,940 --> 00:30:12,060
- So, when we poke very far into the
cell, we see a very large current.

491
00:30:12,060 --> 00:30:14,580
And when we only poke the cell a
little bit,

492
00:30:14,580 --> 00:30:17,500
we see a very small current or none at
all, and this tells us

493
00:30:17,500 --> 00:30:21,820
that the cells are really exquisite
centres of mechanical force.

494
00:30:23,500 --> 00:30:26,820
- They called this molecule Piezo.

495
00:30:27,940 --> 00:30:30,580
This is a model of one of the
molecules

496
00:30:30,580 --> 00:30:32,780
that Ardem and his team discovered -

497
00:30:32,780 --> 00:30:35,340
the biological world's telegraph key.

498
00:30:35,340 --> 00:30:39,980
It's embedded in the surface membrane
of cells like the neuron.

499
00:30:39,980 --> 00:30:42,460
And it's tiny -

500
00:30:42,460 --> 00:30:46,300
just a few millionths of a millimetre
across.

501
00:30:46,300 --> 00:30:49,580
But despite that, it's a really
complicated molecule.

502
00:30:49,580 --> 00:30:53,980
It's a single protein, made up of
roughly 50,000 atoms

503
00:30:53,980 --> 00:30:56,500
arranged in this intricate shape,

504
00:30:56,500 --> 00:31:00,220
with three spiral arms and a cap in
the middle.

505
00:31:00,220 --> 00:31:02,620
The shape of the protein is crucial.

506
00:31:02,620 --> 00:31:06,900
When the cell wall stretches, the
whole structure flattens out,

507
00:31:06,900 --> 00:31:10,860
and the centre opens up, creating a
channel

508
00:31:10,860 --> 00:31:14,820
through which charged particles can
flow into the cell.

509
00:31:14,820 --> 00:31:18,220
This is analogous to pressing the
telegraph key,

510
00:31:18,220 --> 00:31:20,460
allowing electric current to flow.

511
00:31:23,460 --> 00:31:27,060
We now know there are hundreds of
thousands of Piezo molecules

512
00:31:27,060 --> 00:31:29,140
throughout our bodies,

513
00:31:29,140 --> 00:31:31,220
signalling our brains.

514
00:31:31,220 --> 00:31:35,300
They can monitor our blood pressure,
appetite,

515
00:31:35,300 --> 00:31:38,900
the need to wee, the timing of our
heartbeat,

516
00:31:38,900 --> 00:31:41,580
and even regulate our breathing.

517
00:31:46,820 --> 00:31:49,660
And because hundreds of thousands of
Piezos

518
00:31:49,660 --> 00:31:52,180
are embedded in our skin too,

519
00:31:52,180 --> 00:31:56,700
they enable the most exquisite and
underrated of all senses -

520
00:31:56,700 --> 00:31:59,780
the sense of touch.

521
00:31:59,780 --> 00:32:04,340
Think about it - our ability to touch
is amazing.

522
00:32:05,980 --> 00:32:09,980
We can feel the tiniest breath on our
fingertips,

523
00:32:09,980 --> 00:32:14,860
or the feel of a single grain of
sugar,

524
00:32:14,860 --> 00:32:19,140
or the gentlest brush of a feather.

525
00:32:19,140 --> 00:32:22,700
Scientists say we can sense something
on our fingertips

526
00:32:22,700 --> 00:32:27,300
that's just one 500th of the width of
a human hair.

527
00:32:29,340 --> 00:32:31,620
Having discovered Piezo molecules,

528
00:32:31,620 --> 00:32:35,740
Ardem Patapoutian's team then looked
at where evolution

529
00:32:35,740 --> 00:32:39,900
had used them, and what they
discovered was astonishing.

530
00:32:39,900 --> 00:32:43,460
- They seem to be really conserved
across evolution.

531
00:32:43,460 --> 00:32:47,060
So, we don't see them in bacteria, but
in anything that has a nucleus.

532
00:32:47,060 --> 00:32:49,340
Even unicellular organisms have them.

533
00:32:49,340 --> 00:32:53,220
We have seen them in flies, in worms.

534
00:32:54,700 --> 00:32:57,660
Plants, of course, have to sense
mechanosensation as well.

535
00:32:57,660 --> 00:33:02,340
Roots, as they navigate through the
soil and hit a harder surface,

536
00:33:02,340 --> 00:33:04,140
they have to decide to go through it,

537
00:33:04,140 --> 00:33:06,900
or, if it's too hard, go around it.

538
00:33:09,660 --> 00:33:14,260
- The fact Piezo molecules can be
found across such a wide variety

539
00:33:14,260 --> 00:33:18,660
of life tells us they evolved a long
time ago.

540
00:33:20,980 --> 00:33:23,220
- Our sense of pressure sensing,

541
00:33:23,220 --> 00:33:25,820
that we mainly think of as a sense of
touch,

542
00:33:25,820 --> 00:33:29,660
was present hundreds of millions of
years ago in organisms

543
00:33:29,660 --> 00:33:32,580
that were just maybe swimming in the
ocean

544
00:33:32,580 --> 00:33:34,460
and bumping into different things,

545
00:33:34,460 --> 00:33:37,420
and needed to know what they were
bumping against.

546
00:33:41,540 --> 00:33:47,300
- Up to this point, all life on Earth
had lived and died in one place...

547
00:33:48,300 --> 00:33:49,500
..in the oceans.

548
00:33:51,420 --> 00:33:53,980
The land was sterile and empty.

549
00:33:55,060 --> 00:33:57,180
But then, things changed.

550
00:34:00,540 --> 00:34:02,700
Towards the end of the Cambrian
Explosion,

551
00:34:02,700 --> 00:34:06,220
about 500 million years ago,

552
00:34:06,220 --> 00:34:11,180
we think the first complex life began
to creep out of the sea

553
00:34:11,180 --> 00:34:13,580
and onto the land.

554
00:34:13,580 --> 00:34:16,820
Those first things that colonised the
land

555
00:34:16,820 --> 00:34:21,300
were algae, mosses, basic bacteria.

556
00:34:21,300 --> 00:34:26,140
But then, larger, more structured
organisms began to emerge.

557
00:34:33,900 --> 00:34:38,140
Plants evolved root systems that went
underground.

558
00:34:38,140 --> 00:34:42,220
Tall grasses emerged, and eventually
trees.

559
00:34:45,820 --> 00:34:50,060
Following them out of the water were
early insects too,

560
00:34:50,060 --> 00:34:53,500
crawling and burrowing and wriggling
things.

561
00:34:56,020 --> 00:34:58,820
For sea creatures that lived close to
the shoreline,

562
00:34:58,820 --> 00:35:01,180
the land now represented a new

563
00:35:01,180 --> 00:35:04,940
and potentially resource-rich
environment.

564
00:35:04,940 --> 00:35:08,620
But, of course, these animals would
have to evolve considerably

565
00:35:08,620 --> 00:35:11,140
if they were going to survive above
water.

566
00:35:11,140 --> 00:35:13,540
The process took millions of years.

567
00:35:18,860 --> 00:35:23,260
You have to jump forward to 375
million years ago,

568
00:35:23,260 --> 00:35:25,660
to see the first vertebrates

569
00:35:25,660 --> 00:35:28,900
starting to venture onto terra firma.

570
00:35:30,820 --> 00:35:32,940
This is a mud skipper.

571
00:35:32,940 --> 00:35:36,900
It's similar to the kind of animals
that were beginning to evolve

572
00:35:36,900 --> 00:35:38,220
at this time.

573
00:35:39,700 --> 00:35:42,460
Their eyes have moved upwards on their
heads,

574
00:35:42,460 --> 00:35:45,380
instead of on each side with most
fish.

575
00:35:46,500 --> 00:35:50,580
Many scientists now believe that the
way eyes worked out of the water

576
00:35:50,580 --> 00:35:53,420
led to one of the most significant
turning points

577
00:35:53,420 --> 00:35:55,740
in the evolution of the brain.

578
00:35:55,740 --> 00:35:59,980
Professors Malcolm MacIver and Dan
Dombeck, at Northwestern University

579
00:35:59,980 --> 00:36:03,940
in the States, have been studying this
critical moment in evolution.

580
00:36:04,980 --> 00:36:08,700
- With just their rising of the
eyeball out of the water,

581
00:36:08,700 --> 00:36:13,820
you go from a medium which absorbs
light so intensely

582
00:36:13,820 --> 00:36:15,940
that you only see a body length in
front of you

583
00:36:15,940 --> 00:36:18,740
to essentially a perfectly transparent
medium.

584
00:36:18,740 --> 00:36:22,820
That gives you a huge multiplication
in your visual range.

585
00:36:28,180 --> 00:36:30,580
- Now, the key reason for that is to
do with physics,

586
00:36:30,580 --> 00:36:33,460
or more specifically, the physics of
light.

587
00:36:33,460 --> 00:36:35,700
You see, light travels far better
through air

588
00:36:35,700 --> 00:36:37,100
than it does through water.

589
00:36:37,100 --> 00:36:39,780
That might sound rather obvious, but
let me show you.

590
00:36:40,740 --> 00:36:42,580
Safety goggles on.

591
00:36:42,580 --> 00:36:45,140
What I have here is a tank full of sea
water

592
00:36:45,140 --> 00:36:48,940
and a laser pointer that shines light
through the water,

593
00:36:48,940 --> 00:36:52,660
to be picked up by a detector on the
other side, which I can read here.

594
00:36:54,980 --> 00:36:58,300
When I turn on the laser, the light
metre reading doubles

595
00:36:58,300 --> 00:37:01,900
from 25,000 to 50,000 lux.

596
00:37:01,900 --> 00:37:05,460
That's how much light is getting
through the sea water

597
00:37:05,460 --> 00:37:07,740
to the other side. Guys, give me a
hand here.

598
00:37:10,180 --> 00:37:11,740
OK, thanks, guys.

599
00:37:13,340 --> 00:37:15,980
Right, now we do this again.

600
00:37:17,380 --> 00:37:20,060
We'll repeat the test, but with an
empty tank.

601
00:37:22,940 --> 00:37:27,660
And the reading has jumped to over
100,000 lux.

602
00:37:27,660 --> 00:37:32,700
Air is at least 20 times more
transparent than sea water.

603
00:37:32,700 --> 00:37:35,900
You can clearly see this, when you
swim in the sea.

604
00:37:35,900 --> 00:37:38,980
You just can't see very far
underwater.

605
00:37:38,980 --> 00:37:43,500
That's because water is denser than
air and often murkier too,

606
00:37:43,500 --> 00:37:45,780
because of mud or sea life.

607
00:37:47,420 --> 00:37:50,740
And this had huge implications.

608
00:37:50,740 --> 00:37:54,060
As animals moved out of the sea and
onto the land,

609
00:37:54,060 --> 00:37:57,580
the amount of raw visual information
they could receive

610
00:37:57,580 --> 00:37:59,780
increased enormously,

611
00:37:59,780 --> 00:38:02,700
and their brains had to evolve to keep
up.

612
00:38:06,620 --> 00:38:10,380
- How are you going to process all of
that visual input

613
00:38:10,380 --> 00:38:14,060
to survive threats that are coming at
you,

614
00:38:14,060 --> 00:38:17,700
or to find food that might be trying
to escape from you

615
00:38:17,700 --> 00:38:20,580
some distance away? So, you need to
have...

616
00:38:20,580 --> 00:38:23,500
You're going to have to up your
computational brain,

617
00:38:23,500 --> 00:38:26,340
in order to process all that
information.

618
00:38:26,340 --> 00:38:31,100
- Malcolm and Dan believe that moving
from sea to land

619
00:38:31,100 --> 00:38:35,260
led to a massive growth in size and
power of the brain.

620
00:38:36,460 --> 00:38:39,020
- I want to demonstrate with these two
skeletons

621
00:38:39,020 --> 00:38:43,060
just how big a change it was in
relative brain size

622
00:38:43,060 --> 00:38:47,260
between ancestral fish and mammals.

623
00:38:47,260 --> 00:38:51,180
And so, here is a fish

624
00:38:51,180 --> 00:38:54,260
that's in real life about this big

625
00:38:54,260 --> 00:38:56,300
and its body mass, a bit larger,

626
00:38:56,300 --> 00:38:59,060
but it's approximately similar to what
a cat is.

627
00:38:59,060 --> 00:39:03,100
And yet the total volume of this
animal's brain

628
00:39:03,100 --> 00:39:05,500
is about two teaspoons,

629
00:39:05,500 --> 00:39:09,580
and it's a factor of ten larger brain

630
00:39:09,580 --> 00:39:12,700
in mammals, compared to fish.

631
00:39:14,660 --> 00:39:20,020
- The consequences of the move to land
are stamped all over our brains.

632
00:39:20,020 --> 00:39:24,300
Significant regions of the brain have
evolved to make sense

633
00:39:24,300 --> 00:39:28,380
of the mass of visual data pouring in
via optic nerves

634
00:39:28,380 --> 00:39:30,380
connected to our retinas.

635
00:39:30,380 --> 00:39:34,740
Regions like the primary and secondary
visual cortex,

636
00:39:34,740 --> 00:39:37,860
the posterior parietal lobe,

637
00:39:37,860 --> 00:39:40,380
and the fusiform gyrus.

638
00:39:41,700 --> 00:39:45,220
But though the move to land put down
the foundations

639
00:39:45,220 --> 00:39:47,300
of these parts of my brain,

640
00:39:47,300 --> 00:39:50,060
it very nearly never got going.

641
00:39:50,060 --> 00:39:53,540
Because around 250 million years ago,

642
00:39:53,540 --> 00:39:55,940
catastrophe struck.

643
00:39:55,940 --> 00:39:58,380
LOUD BOOM

644
00:39:58,380 --> 00:40:02,140
A massive series of volcanoes erupted
in Siberia.

645
00:40:04,820 --> 00:40:08,380
The cataclysm exposed a huge
geological fault,

646
00:40:08,380 --> 00:40:10,780
stretching for hundreds of miles.

647
00:40:14,500 --> 00:40:19,100
And from this gash poured billions of
tonnes of hot lava.

648
00:40:19,100 --> 00:40:22,820
Some suggest this flooded the plains
below

649
00:40:22,820 --> 00:40:28,060
and came into contact with one the
largest exposed coal deposits

650
00:40:28,060 --> 00:40:30,220
in the world.

651
00:40:31,820 --> 00:40:36,020
Picture the scene - 252 million years
ago,

652
00:40:36,020 --> 00:40:39,340
billions of tonnes of red hot lava,

653
00:40:39,340 --> 00:40:43,060
billions of tonnes of thick, black,
dirty coal deposits.

654
00:40:43,060 --> 00:40:47,700
The result was a toxic gas release on
a catastrophic scale.

655
00:40:47,700 --> 00:40:49,820
Poisons like sulphur dioxide,

656
00:40:49,820 --> 00:40:53,420
nitrogen sulphide and methanes filled
the atmosphere.

657
00:40:53,420 --> 00:40:58,540
They then mixed with moisture in the
air to create powerful acids,

658
00:40:58,540 --> 00:41:00,780
which then rained down,

659
00:41:00,780 --> 00:41:04,700
wiping out nearly all life from the
face of the Earth.

660
00:41:05,860 --> 00:41:10,020
As well as this, the volcanoes belched
carbon dioxide

661
00:41:10,020 --> 00:41:12,300
from deep inside the Earth.

662
00:41:12,300 --> 00:41:17,620
Trillions of tonnes suffocating almost
all plants and animals.

663
00:41:18,940 --> 00:41:21,660
Today, we consider the world to be on
the brink

664
00:41:21,660 --> 00:41:24,300
of a carbon dioxide catastrophe.

665
00:41:24,300 --> 00:41:28,660
There are 420 parts per million of
carbon dioxide in the atmosphere,

666
00:41:28,660 --> 00:41:30,660
and rising.

667
00:41:30,660 --> 00:41:34,460
But 250 million years ago, the
Siberian volcanoes

668
00:41:34,460 --> 00:41:37,940
released 5,000 parts per million -

669
00:41:37,940 --> 00:41:39,620
over ten times more.

670
00:41:39,620 --> 00:41:41,700
There was total devastation.

671
00:41:41,700 --> 00:41:45,420
95% of all species were wiped out.

672
00:41:45,420 --> 00:41:47,460
In the whole history of life on Earth,

673
00:41:47,460 --> 00:41:50,740
it's the closest we've come to total
extinction.

674
00:41:53,060 --> 00:41:55,540
But, of course, it wasn't the end.

675
00:41:55,540 --> 00:41:58,420
Some things did make it through.

676
00:41:58,420 --> 00:42:02,380
The survivors were smaller animals
that could hide away.

677
00:42:02,380 --> 00:42:05,700
They could burrow underground, they
could crawl into crevices

678
00:42:05,700 --> 00:42:07,820
or slither into the mud.

679
00:42:07,820 --> 00:42:09,860
They could survive on less oxygen,

680
00:42:09,860 --> 00:42:12,580
they could cope with the heat, the
darkness

681
00:42:12,580 --> 00:42:15,380
and the toxic chemical mix.

682
00:42:15,380 --> 00:42:20,860
The scene was now set for one of
life's most incredible comebacks,

683
00:42:20,860 --> 00:42:25,460
and one of the most profound moments
in the story of our brains.

684
00:42:28,700 --> 00:42:31,700
This is the Vale of Glamorgan in
Wales.

685
00:42:31,700 --> 00:42:34,660
After the massive extinction event,

686
00:42:34,660 --> 00:42:40,700
this whole area was an archipelago of
small, low-lying, linked islands,

687
00:42:40,700 --> 00:42:44,740
which makes it particularly
interesting to palaeontologist

688
00:42:44,740 --> 00:42:46,540
Dr Elis Newham.

689
00:42:46,540 --> 00:42:48,820
What was this place like back then?

690
00:42:48,820 --> 00:42:52,060
- It's 50 million years after the
end-Permian mass extinction,

691
00:42:52,060 --> 00:42:53,420
the Great Dying.

692
00:42:53,420 --> 00:42:55,260
So, life is bouncing back by then.

693
00:42:56,740 --> 00:43:01,140
- We're now firmly in the era of the
first dinosaurs,

694
00:43:01,140 --> 00:43:04,460
the gigantic creatures that were
coming to dominate the world.

695
00:43:07,580 --> 00:43:12,540
But Elis is more interested in a much,
much tinier creature -

696
00:43:12,540 --> 00:43:15,940
one whose remains literally fell
through the cracks.

697
00:43:17,220 --> 00:43:19,660
- Within these islands, there were
cracks and fissures

698
00:43:19,660 --> 00:43:22,300
that naturally developed. And so, any
animal that died,

699
00:43:22,300 --> 00:43:24,140
their remains would have got washed
in.

700
00:43:24,140 --> 00:43:27,180
And so, this gives us an amazing
snapshot onto what life

701
00:43:27,180 --> 00:43:30,340
would have been like on those islands
200 million years ago.

702
00:43:31,420 --> 00:43:34,820
- And what Elis and his colleagues
found deep in these rocks

703
00:43:34,820 --> 00:43:39,180
were new clues to how our brains were
actually formed.

704
00:43:40,420 --> 00:43:45,340
Bones from a tiny, rat-like creature
called Morganucodon,

705
00:43:45,340 --> 00:43:47,460
or Morgie.

706
00:43:47,460 --> 00:43:52,540
- We found thousands of isolated
teeth, jaws and bones.

707
00:43:53,780 --> 00:43:56,260
And I've brought one here with me to
show you.

708
00:43:56,260 --> 00:43:57,860
- I mean, it's tiny.

709
00:43:57,860 --> 00:43:59,420
This ain't no T. Rex.

710
00:43:59,420 --> 00:44:01,660
So, what did this creature look like?

711
00:44:01,660 --> 00:44:03,660
- It was about the size of a shrew.

712
00:44:03,660 --> 00:44:06,220
It might have been furry, it probably
had whiskers,

713
00:44:06,220 --> 00:44:09,100
and it was kind of scrabbling around
the undergrowth

714
00:44:09,100 --> 00:44:11,500
in what is now South Wales.
- Right.

715
00:44:11,500 --> 00:44:13,580
- So, it was definitely insectivorous.

716
00:44:13,580 --> 00:44:16,620
It fed on beetles, and kind of gnat
wings and things like that,

717
00:44:16,620 --> 00:44:18,940
that were living with it at the time.

718
00:44:18,940 --> 00:44:22,380
- But what no-one expected is what
they saw

719
00:44:22,380 --> 00:44:26,340
when they started looking inside
Morgie's skull.

720
00:44:26,340 --> 00:44:29,460
- Colleagues CT scanned one of these
skulls,

721
00:44:29,460 --> 00:44:32,900
and what they found was pretty
amazing.

722
00:44:32,900 --> 00:44:36,060
So, this is a cast, a 3D print, of a
model

723
00:44:36,060 --> 00:44:39,300
that they created of the brain of
Morganucodon.
- Wow!

724
00:44:41,460 --> 00:44:43,220
Very tiny.
- Absolutely tiny.

725
00:44:43,220 --> 00:44:46,020
Maybe I'll get a scaled version for
you.

726
00:44:47,300 --> 00:44:49,140
- Right.
- So, here we go.

727
00:44:49,140 --> 00:44:51,860
- On top of Morgie's brain,

728
00:44:51,860 --> 00:44:55,420
they noticed an intriguing new
development.

729
00:44:55,420 --> 00:44:57,340
- We started noticing with this thing.

730
00:44:57,340 --> 00:44:59,660
You can see this lumpy bit here?

731
00:44:59,660 --> 00:45:01,620
- And so, the brains of other
creatures

732
00:45:01,620 --> 00:45:03,860
that lived around that time didn't
have this bump?

733
00:45:03,860 --> 00:45:05,140
- As far as we know.

734
00:45:05,140 --> 00:45:07,180
So, Morgie shows a kind of, a
jump-step

735
00:45:07,180 --> 00:45:08,980
in the development of the brain.

736
00:45:08,980 --> 00:45:11,220
The brain size, and also the brain
complexity.

737
00:45:13,460 --> 00:45:18,540
- This bump is a new part of the brain
called the neocortex,

738
00:45:18,540 --> 00:45:22,140
and it's what sets creatures like
Morgie apart

739
00:45:22,140 --> 00:45:24,100
from other animals of the time.

740
00:45:26,420 --> 00:45:29,780
It's a small bump with huge
implications,

741
00:45:29,780 --> 00:45:33,740
because it's the bump that makes our
brains so unique.

742
00:45:34,940 --> 00:45:36,900
So, where did it come from?

743
00:45:41,020 --> 00:45:44,020
To find out more about the neocortex,

744
00:45:44,020 --> 00:45:46,860
I've come to meet Professor Steve
Brusatte,

745
00:45:46,860 --> 00:45:50,420
an expert in palaeontology and
evolution.

746
00:45:50,420 --> 00:45:53,460
- This is Morgie's brain.

747
00:45:53,460 --> 00:45:56,180
This is a digital model from a CAT
scan.

748
00:45:56,180 --> 00:45:59,340
And just to orient ourselves, this bit
here at the front,

749
00:45:59,340 --> 00:46:00,780
that's the olfactory bulb,

750
00:46:00,780 --> 00:46:03,380
that's the part that controls our
sense of smell.

751
00:46:03,380 --> 00:46:07,460
Back here is the cerebrum, one of the
main components of the brain.

752
00:46:07,460 --> 00:46:11,540
And up there, on the top, is that
curious little bump.

753
00:46:11,540 --> 00:46:13,140
- And that's what I'm interested in.

754
00:46:13,140 --> 00:46:14,940
So, where did that come from?

755
00:46:14,940 --> 00:46:19,980
- We have a few clues that we think
helps tell that story.

756
00:46:19,980 --> 00:46:24,660
And the first one of those is if we
look at the bones of Morgie.

757
00:46:25,820 --> 00:46:29,500
- Unlike any animals before this time,
the microscope reveals

758
00:46:29,500 --> 00:46:33,620
Morgie's bones are honeycombed by tiny
holes -

759
00:46:33,620 --> 00:46:37,580
evidence of a massive step-change in
blood flow.

760
00:46:37,580 --> 00:46:42,780
- Those are just digital renderings of
the channels for blood vessels.

761
00:46:42,780 --> 00:46:46,820
And the key thing is that their bones,
their skeletons

762
00:46:46,820 --> 00:46:52,180
were becoming much more full of blood
and blood vessels,

763
00:46:52,180 --> 00:46:56,020
and that means that they could have
higher metabolic rates.

764
00:46:56,020 --> 00:46:58,700
- So, their bodies were just working
harder?

765
00:46:58,700 --> 00:47:01,740
- Their bodies were working harder,
they could grow faster,

766
00:47:01,740 --> 00:47:04,060
their metabolism was increasing.

767
00:47:04,060 --> 00:47:07,300
That's part of the story, but there's
a second clue

768
00:47:07,300 --> 00:47:11,020
to this as well, which we'll have to
take a look over here.
- OK.

769
00:47:13,340 --> 00:47:16,020
- And this is a little fossil...

770
00:47:17,340 --> 00:47:20,420
..discovered about a decade ago by
teams from here

771
00:47:20,420 --> 00:47:22,980
at the National Museum of Scotland,
out on the Isle of Skye.

772
00:47:24,340 --> 00:47:26,860
And if we put it under the scope,

773
00:47:26,860 --> 00:47:28,940
you can see what it is.

774
00:47:31,500 --> 00:47:35,220
The bit sticking up from the top, that
tells us what this fossil is.

775
00:47:35,220 --> 00:47:36,980
And those things are teeth.

776
00:47:36,980 --> 00:47:38,740
So, this is a jawbone.

777
00:47:38,740 --> 00:47:41,700
But when you blow it up in size, you
3D print it,

778
00:47:41,700 --> 00:47:45,380
you can see all of these teeth here
and it's in these teeth

779
00:47:45,380 --> 00:47:49,180
that tell us the importance of these
fossils,

780
00:47:49,180 --> 00:47:50,700
and they tell us a few things.

781
00:47:50,700 --> 00:47:53,540
These teeth, they're really sharp,
there's lots of little points.

782
00:47:53,540 --> 00:47:57,020
And when the teeth came together, all
those points would interlock,

783
00:47:57,020 --> 00:48:00,660
and they would bite really strongly,
be able to chew the food.

784
00:48:00,660 --> 00:48:03,340
But the other thing is, the babies did
something different.

785
00:48:03,340 --> 00:48:06,100
We can tell that these animals had one
set of baby teeth,

786
00:48:06,100 --> 00:48:07,620
one set of adult teeth,

787
00:48:07,620 --> 00:48:11,260
and that means that the babies were
drinking milk.

788
00:48:11,260 --> 00:48:12,500
- OK.

789
00:48:12,500 --> 00:48:14,220
What does that tell us?

790
00:48:14,220 --> 00:48:18,100
- So, these, of course, are mammals,
just like us.

791
00:48:18,100 --> 00:48:20,020
These are early ancestors of ours.

792
00:48:20,020 --> 00:48:22,820
What we see with these fossils at this
time,

793
00:48:22,820 --> 00:48:26,740
these mammals were entering an age of
gluttony.

794
00:48:26,740 --> 00:48:29,620
- So, these mammals ate more,

795
00:48:29,620 --> 00:48:32,140
their offspring drank milk,

796
00:48:32,140 --> 00:48:35,780
and they had more blood flow in their
bones.

797
00:48:35,780 --> 00:48:38,780
This wasn't just the start of mammals,

798
00:48:38,780 --> 00:48:40,740
it was a new way of being.

799
00:48:41,900 --> 00:48:45,380
- That tells us the big reveal here,

800
00:48:45,380 --> 00:48:50,780
and that is that we think that these
mammals were becoming warm-blooded.

801
00:48:50,780 --> 00:48:53,460
And that means you have a constant
body temperature,

802
00:48:53,460 --> 00:48:55,900
a high body temperature,

803
00:48:55,900 --> 00:48:58,260
and your body temperature is high and
constant

804
00:48:58,260 --> 00:49:01,060
regardless of the season, regardless
of the time of day,

805
00:49:01,060 --> 00:49:03,020
regardless of where you live.

806
00:49:03,020 --> 00:49:05,540
And that's a very special superpower,
that's what we have.

807
00:49:07,460 --> 00:49:12,340
- Warm-bloodedness enabled animals to
exploit new niches -

808
00:49:12,340 --> 00:49:14,780
hunting at night and in the cold.

809
00:49:17,340 --> 00:49:19,420
So, it takes resources to be
warm-blooded.

810
00:49:19,420 --> 00:49:22,420
If you think about the cost of heating
our homes, it's expensive.

811
00:49:22,420 --> 00:49:25,980
- A mammal needs to eat about eight
times, give or take,

812
00:49:25,980 --> 00:49:29,940
as much food as a cold-blooded animal
of a similar size.

813
00:49:29,940 --> 00:49:33,740
- So, brining this back to the
beginning, how do all these changes

814
00:49:33,740 --> 00:49:36,860
affect the brain of Morganucodon?

815
00:49:36,860 --> 00:49:41,180
- That's where that bump on the brain
comes in - that's the neocortex.

816
00:49:41,180 --> 00:49:43,540
It's clearly getting larger.

817
00:49:43,540 --> 00:49:46,180
That's the expansion of the brain

818
00:49:46,180 --> 00:49:50,020
that's happening at the exact same
time in evolution

819
00:49:50,020 --> 00:49:52,420
as these changes to the teeth, changes
to the diet,

820
00:49:52,420 --> 00:49:54,420
changes to the metabolism.

821
00:49:54,420 --> 00:49:57,100
- So, you have the evidence, the
bones, the teeth,

822
00:49:57,100 --> 00:50:01,220
suggesting they are eating more,
they're metabolising more,

823
00:50:01,220 --> 00:50:03,860
er, they have to find food more...

824
00:50:05,260 --> 00:50:08,860
..often, and to do that, they need
bigger brains.

825
00:50:08,860 --> 00:50:10,700
- That's it, that's the story.

826
00:50:10,700 --> 00:50:13,660
And it's a huge story and it's one of
the biggest changes

827
00:50:13,660 --> 00:50:16,060
that we see in the evolution of
animals.

828
00:50:19,220 --> 00:50:24,540
- So, what did these new parts of the
brain allow animals to do?

829
00:50:24,540 --> 00:50:28,620
It seems to have led to the
development of a remarkable

830
00:50:28,620 --> 00:50:31,900
new ability, a true superpower.

831
00:50:33,340 --> 00:50:37,460
That superpower is what we might
loosely call imagination -

832
00:50:37,460 --> 00:50:41,660
our remarkable ability to remember
scenes from our past,

833
00:50:41,660 --> 00:50:44,940
or to conjure up ones in our future.

834
00:50:46,260 --> 00:50:49,140
Cast your mind back to when you were a
young child.

835
00:50:51,660 --> 00:50:54,580
Try to remember what it was like.

836
00:50:54,580 --> 00:50:59,700
Now, conjure up your next Christmas or
family gathering.

837
00:51:00,780 --> 00:51:04,300
Can you see in your mind's eye what it
will be like?

838
00:51:04,300 --> 00:51:09,220
What's amazing is how effective this
internal visualisation can be,

839
00:51:09,220 --> 00:51:14,020
our ability to see the past or imagine
the future.

840
00:51:14,020 --> 00:51:16,460
We can link it to smell and even to
our emotions.

841
00:51:18,860 --> 00:51:22,500
To investigate the mammalian origins
of imagination,

842
00:51:22,500 --> 00:51:26,180
Malcolm MacIver and Dan Dombeck built
this -

843
00:51:26,180 --> 00:51:30,780
an open maze with food at several
reward ports.

844
00:51:30,780 --> 00:51:34,500
And because genuine early mammals no
longer exist,

845
00:51:34,500 --> 00:51:40,100
his team use mice to see how they
visualise the world around them.

846
00:51:40,100 --> 00:51:43,580
And to help motivate the mouse, an
unusual predator.

847
00:51:45,140 --> 00:51:46,580
- We came up with a large arena,

848
00:51:46,580 --> 00:51:51,340
where we could essentially run a
predator-prey scenario,

849
00:51:51,340 --> 00:51:54,620
but with the predator being an
autonomous robot

850
00:51:54,620 --> 00:51:56,380
that we have designed and developed.

851
00:51:57,740 --> 00:52:02,060
The robot doesn't physically attack
the rodent in the space,

852
00:52:02,060 --> 00:52:05,540
it simply puffs it an intense blast of
air

853
00:52:05,540 --> 00:52:09,420
and rodents really dislike that, so
they avoid the robot.

854
00:52:11,260 --> 00:52:15,780
- The team then attached probes into
the mouse's hippocampus,

855
00:52:15,780 --> 00:52:20,500
which processes location information
from the mammalian neocortex.

856
00:52:23,740 --> 00:52:27,780
- And we asked, "What exactly is going
through the mind of the mouse?

857
00:52:27,780 --> 00:52:31,500
"Is it imagining a future position of
the robot?

858
00:52:31,500 --> 00:52:33,980
"Is it imagining a future position of
itself?"

859
00:52:36,900 --> 00:52:40,060
- They put the mice through the maze
thousands of times,

860
00:52:40,060 --> 00:52:44,980
an environment specially designed to
make them think ahead.

861
00:52:44,980 --> 00:52:48,140
They then took data from the probes

862
00:52:48,140 --> 00:52:52,140
to get a sense of what was happening
inside their brains.

863
00:52:54,860 --> 00:52:57,660
- So, here's the experiment that you
saw earlier.

864
00:52:57,660 --> 00:53:00,380
We've also included neural data.

865
00:53:00,380 --> 00:53:04,260
- The blue dot represents where the
mouse actually is,

866
00:53:04,260 --> 00:53:07,900
and the red dot is where the robot is.

867
00:53:07,900 --> 00:53:12,300
But incredibly, by reading the signals
from the mouse's neurons,

868
00:53:12,300 --> 00:53:16,740
the team could tell where the mouse
was planning to go.

869
00:53:16,740 --> 00:53:20,020
That's the pixellated blue blob.

870
00:53:20,020 --> 00:53:23,420
Malcolm believes this reveals
important clues

871
00:53:23,420 --> 00:53:25,820
about the mouse's imagination.

872
00:53:27,780 --> 00:53:32,420
- You can see that, essentially, we
have the mouse thinking about

873
00:53:32,420 --> 00:53:34,700
where it's getting to in the next
little bit.

874
00:53:34,700 --> 00:53:37,820
It's actually here, and this is where
it's going to be soon,

875
00:53:37,820 --> 00:53:41,060
and it seems to be thinking about
where it might be in the future.

876
00:53:41,060 --> 00:53:46,180
So, right now, the mouse's imagination
of its location

877
00:53:46,180 --> 00:53:48,860
and its actual location are very
close.

878
00:53:48,860 --> 00:53:51,380
- But then something remarkable
happens.

879
00:53:51,380 --> 00:53:54,060
The pixellated blue blob

880
00:53:54,060 --> 00:53:56,860
moves away from the blue dot.

881
00:53:56,860 --> 00:53:59,900
This suggests that the mouse is
thinking

882
00:53:59,900 --> 00:54:03,780
of where to go next to find food.

883
00:54:03,780 --> 00:54:06,380
- Right here, it skips over to here,

884
00:54:06,380 --> 00:54:09,020
and it starts to coalesce

885
00:54:09,020 --> 00:54:11,820
around this next reward port

886
00:54:11,820 --> 00:54:13,380
which, you'll see in a second,

887
00:54:13,380 --> 00:54:15,180
is where it's going to go to next.

888
00:54:15,180 --> 00:54:17,740
So, it appears to be thinking about...

889
00:54:17,740 --> 00:54:20,820
This is a reward port, and it appears
to be thinking about

890
00:54:20,820 --> 00:54:23,380
the next reward port it's going to be
visiting.

891
00:54:23,380 --> 00:54:25,780
And that is really interesting,

892
00:54:25,780 --> 00:54:30,060
because watch what happens after the
mouse leaves this position,

893
00:54:30,060 --> 00:54:33,900
after it's checked that reward port,
it actually goes over

894
00:54:33,900 --> 00:54:37,780
to exactly the location it seems to
have been thinking about.

895
00:54:37,780 --> 00:54:39,180
So, it's thinking of the future,

896
00:54:39,180 --> 00:54:42,580
it's imagining the future, which is
exactly what we'd hoped to see with

897
00:54:42,580 --> 00:54:47,060
these more sophisticated behaviours
that the arena is exhibiting.

898
00:54:54,420 --> 00:54:57,340
- This is a bold claim -

899
00:54:57,340 --> 00:55:01,820
that leaving water for land, where
long-range vision makes planning

900
00:55:01,820 --> 00:55:04,380
a matter of life or death,

901
00:55:04,380 --> 00:55:07,460
may have led to the ability to
imagine.

902
00:55:08,940 --> 00:55:11,540
- If you're going to do the more
complicated thing,

903
00:55:11,540 --> 00:55:15,100
which is essentially representing the
future and future opportunities

904
00:55:15,100 --> 00:55:18,460
and threats, that requires a lot of
neural power.

905
00:55:18,460 --> 00:55:20,860
It's a massively intensive task.

906
00:55:20,860 --> 00:55:24,700
So, this is one of the demands on the
nervous system

907
00:55:24,700 --> 00:55:30,180
that presumably feeds into this huge
10x increase in brain size

908
00:55:30,180 --> 00:55:32,860
in the mammals and in the birds,

909
00:55:32,860 --> 00:55:36,060
relative to ancestral aquatic
organisms.

910
00:55:37,500 --> 00:55:42,780
- Being able to visualise the future,
to plan and solve problems,

911
00:55:42,780 --> 00:55:45,900
powers enabled by the burgeoning
neocortex,

912
00:55:45,900 --> 00:55:49,180
would eventually come to give mammals

913
00:55:49,180 --> 00:55:51,580
a huge evolutionary advantage.

914
00:55:52,780 --> 00:55:57,700
- They survive, probably in large part
because of their large brains,

915
00:55:57,700 --> 00:56:00,620
their high intelligence, their ability
to solve problems.

916
00:56:00,620 --> 00:56:02,420
Within a few hundred thousand years,

917
00:56:02,420 --> 00:56:04,420
we start seeing mammals the size of
pigs.

918
00:56:04,420 --> 00:56:05,900
Within about a million years,

919
00:56:05,900 --> 00:56:08,380
we start to see mammals the size of
cows.

920
00:56:08,380 --> 00:56:12,340
So, as these mammals themselves are
getting larger,

921
00:56:12,340 --> 00:56:16,700
the brains are getting larger, but you
can see it better on CAT scans.

922
00:56:16,700 --> 00:56:19,660
These are the brains, you can kind of
see them getting bigger.

923
00:56:19,660 --> 00:56:21,900
And that grey bit at the top,

924
00:56:21,900 --> 00:56:26,420
that's the same thing as the bump in
Morganucodon, that's the neocortex,

925
00:56:26,420 --> 00:56:30,900
but you can see it's getting bigger
and bigger and bigger.

926
00:56:30,900 --> 00:56:33,900
And as mammals continue to adapt

927
00:56:33,900 --> 00:56:38,460
and evolve into dogs and cats and
bats, whales, elephants, kangaroos,

928
00:56:38,460 --> 00:56:41,660
all the mammals that we know, monkeys,
apes,

929
00:56:41,660 --> 00:56:45,380
and eventually humans, you know, that
neocortex,

930
00:56:45,380 --> 00:56:49,380
it came to envelop the surface of the
brain.

931
00:56:49,380 --> 00:56:52,260
- And so, most of what we regard as
the brains of humans

932
00:56:52,260 --> 00:56:55,940
actually emerged from that bump in
Morgie?

933
00:56:55,940 --> 00:56:58,740
- Exactly. That's the first whisper of
a revolution,

934
00:56:58,740 --> 00:57:04,340
a cognitive revolution, and we see in
ourselves that same structure,

935
00:57:04,340 --> 00:57:06,220
but a just much grander scale.

936
00:57:06,220 --> 00:57:08,740
- So, how important, would you say,
was the emergence

937
00:57:08,740 --> 00:57:12,900
of warm-blooded animals in the
evolution of the brain?

938
00:57:12,900 --> 00:57:17,420
- To me, that was the single biggest,
Big Bang instance

939
00:57:17,420 --> 00:57:19,540
in the history of brain evolution.

940
00:57:19,540 --> 00:57:22,260
So much about the brains that we have
today were shaped

941
00:57:22,260 --> 00:57:26,860
by our metabolism being evolved by our
fossil ancestors.

942
00:57:29,940 --> 00:57:34,060
- If Malcolm MacIver, Dan Dombeck and
Steve Brusatte are right,

943
00:57:34,060 --> 00:57:38,540
then the movement to land and the
development of warm-bloodedness

944
00:57:38,540 --> 00:57:42,540
are responsible for the single largest
neural growth spurt

945
00:57:42,540 --> 00:57:45,020
in 600 million years.

946
00:57:46,940 --> 00:57:49,100
It gave us the greatest gift of all...

947
00:57:50,180 --> 00:57:51,340
..the brain.

948
00:57:54,540 --> 00:57:56,100
Next time -

949
00:57:56,100 --> 00:58:00,780
foraging, tool-building,
child-rearing, and relationships.

950
00:58:00,780 --> 00:58:04,220
How our social lives have shaped the
human brain.

951
00:58:07,620 --> 00:58:12,780
Curious about how MRI technology can
reveal the secrets of your brain?

952
00:58:12,780 --> 00:58:16,300
To watch the Open University's new
animation

953
00:58:16,300 --> 00:58:20,220
exploring how an MRI works and what it
reveals,

954
00:58:20,220 --> 00:58:27,020
scan the QR code, or go to...

955
00:58:27,020 --> 00:58:30,100
..and follow the links to the Open University.

956
00:59:08,960 --> 00:59:12,240
I'm Jim Al-Khalili, a professor of
theoretical physics,

957
00:59:12,240 --> 00:59:16,000
and I'm exploring how the most complex
objects

958
00:59:16,000 --> 00:59:20,200
we know of in the universe
- our brains - evolved.

959
00:59:20,200 --> 00:59:22,080
- This is what your head looks like
inside.

960
00:59:22,080 --> 00:59:23,200
- JIM LAUGHS

961
00:59:29,240 --> 00:59:32,440
In the last episode, we went from the
first neurons

962
00:59:32,440 --> 00:59:34,240
to the early mammal brain.

963
00:59:34,240 --> 00:59:35,360
Wow!

964
00:59:36,960 --> 00:59:38,480
GIBBON SHRIEKS

965
00:59:38,480 --> 00:59:42,520
In this episode, I learn how life in
the forests shaped our brains...

966
00:59:44,720 --> 00:59:50,440
..and how our primate ancestors solved
problems to survive.

967
00:59:50,440 --> 00:59:52,800
- Look how quick!
- Oh, my word!

968
00:59:54,720 --> 00:59:59,280
With my wife, I investigate how
relationships made us intelligent...

969
00:59:59,280 --> 01:00:01,000
You're not a show-off like me.

970
01:00:01,000 --> 01:00:03,720
- No, I'm not a show-off like you. Not
many people are.

971
01:00:03,720 --> 01:00:06,720
- ..and how our brains are wired to be
social.

972
01:00:06,720 --> 01:00:09,240
- The single best predictor

973
01:00:09,240 --> 01:00:11,960
of how long you're going to live into
the future,

974
01:00:11,960 --> 01:00:14,880
it's simply the number and quality of
close friendships.

975
01:00:16,960 --> 01:00:21,720
- As we build artificial intelligence,
vying to overtake our brains...

976
01:00:22,720 --> 01:00:27,680
..I want to find out what makes the
thing in our skulls so special.

977
01:00:28,680 --> 01:00:30,720
This is my brain,

978
01:00:30,720 --> 01:00:34,720
and this is its 600 million-year
story.

979
01:00:46,240 --> 01:00:51,720
66 million years ago, the Earth lay in
desolation and darkness.

980
01:00:51,720 --> 01:00:55,320
An asteroid smashed into the surface
of the planet...

981
01:00:56,320 --> 01:01:00,960
..soot and ash and vaporised bedrock
dimming the sun.

982
01:01:00,960 --> 01:01:04,960
Perhaps three-quarters of all life on
Earth was wiped out...

983
01:01:07,960 --> 01:01:11,720
..including the gigantic dinosaurs,
which had ruled the world.

984
01:01:12,720 --> 01:01:16,320
But as the Earth slowly recovered,
forests returned

985
01:01:16,320 --> 01:01:18,560
and spread across the land.

986
01:01:19,560 --> 01:01:21,920
And with the dinosaurs gone,

987
01:01:21,920 --> 01:01:25,720
small creatures colonised this new
habitat.

988
01:01:25,720 --> 01:01:28,240
Among them were our ancestors.

989
01:01:28,240 --> 01:01:32,480
Now, here's the mystery, how did they
survive this catastrophe?

990
01:01:38,480 --> 01:01:42,960
Dr Ornella Bertrand studies the
extremely limited evidence

991
01:01:42,960 --> 01:01:46,960
that survives from this dark period in
the Earth's history.

992
01:01:47,960 --> 01:01:49,440
That is not an easy job.

993
01:01:49,440 --> 01:01:52,840
You've drawn the short straw when it
comes to palaeontology, right?

994
01:01:52,840 --> 01:01:55,240
- Definitely, because it's very
difficult.

995
01:01:55,240 --> 01:01:57,120
There's just not that many fossils.

996
01:01:57,120 --> 01:01:59,760
We find teeth, we find, like, a bit of
bone sometimes.

997
01:01:59,760 --> 01:02:02,640
One group that I'm really interested
in understanding

998
01:02:02,640 --> 01:02:05,240
is a group called plesiadapiforms.

999
01:02:05,240 --> 01:02:08,120
They were little, like, warm-blooded
mammals.

1000
01:02:09,720 --> 01:02:13,480
- Plesiadapiforms resembled modern
shrews.

1001
01:02:13,480 --> 01:02:16,240
It's thought they used their sharp
claws

1002
01:02:16,240 --> 01:02:20,960
to cling onto the branches of trees in
the primeval forest.

1003
01:02:20,960 --> 01:02:23,680
They're the closest we've found to the
predecessors

1004
01:02:23,680 --> 01:02:26,880
of all today's primates, including us.

1005
01:02:27,880 --> 01:02:32,720
Ornella studies their skulls, but she
doesn't have many to work with.

1006
01:02:32,720 --> 01:02:35,640
- We only have, like, six good
specimens so far.

1007
01:02:35,640 --> 01:02:40,320
- Six specimens in total...
- In total.
- ..of these creatures?
- Yeah, yeah.

1008
01:02:40,320 --> 01:02:43,120
So that's very little, but we can
learn so much

1009
01:02:43,120 --> 01:02:45,120
just from those different skulls.

1010
01:02:45,120 --> 01:02:49,720
- Ornella has a 3D print of the skull
of a specimen

1011
01:02:49,720 --> 01:02:55,560
called Ignacius graybullianus,
upscaled so we can see the details.

1012
01:02:55,560 --> 01:02:58,720
By scanning the cavity inside the
skull,

1013
01:02:58,720 --> 01:03:02,240
she's been able to produce a cast of
the missing brain.

1014
01:03:02,240 --> 01:03:05,200
- Ta-dah! It's amazing, isn't it?
- That is incredible.

1015
01:03:05,200 --> 01:03:08,240
- It gives us, like, so much
information about

1016
01:03:08,240 --> 01:03:10,720
what actually those animals were able
to do.

1017
01:03:10,720 --> 01:03:13,160
For example, these structures in
front.

1018
01:03:13,160 --> 01:03:14,880
- I was just going to ask you.

1019
01:03:14,880 --> 01:03:17,480
They're funny little knobbly bits at
the front.
- Yes!

1020
01:03:17,480 --> 01:03:20,560
We still have that structure, the
olfactory bulbs, in humans.

1021
01:03:20,560 --> 01:03:23,040
- They're olfactory? OK. So that's for
smell?

1022
01:03:23,040 --> 01:03:24,720
- Yeah, yeah, exactly.

1023
01:03:25,720 --> 01:03:30,600
- Plesiadapiforms had very large
smell-processing systems.

1024
01:03:31,600 --> 01:03:35,480
Ornella believes they may have
scavenged at dusk and at night,

1025
01:03:35,480 --> 01:03:38,640
when a strong sense of smell is very
useful.

1026
01:03:39,640 --> 01:03:43,000
- I imagine them being, like, quietly
moving among the branches.

1027
01:03:43,000 --> 01:03:45,360
That's kind of, yeah, how I see them.

1028
01:03:45,360 --> 01:03:49,840
- For this documentary, I've had my
brain scanned.

1029
01:03:49,840 --> 01:03:52,320
I've been carrying around...

1030
01:03:53,320 --> 01:03:56,480
..a 3D-printed version of my brain.
- Wow!

1031
01:03:56,480 --> 01:04:00,200
- Which is here, which I'm very proud
of.
- I would be. That's amazing!

1032
01:04:00,200 --> 01:04:02,120
- Which we can put alongside Ignacius.

1033
01:04:02,120 --> 01:04:05,160
Look, I'm not boasting - there's been
some evolution.

1034
01:04:05,160 --> 01:04:07,480
- SHE CHUCKLES
- Some... Just a little bit!

1035
01:04:08,480 --> 01:04:11,480
I'm interested in a particular part of
the brain -

1036
01:04:11,480 --> 01:04:13,240
the neocortex.

1037
01:04:14,240 --> 01:04:16,880
- So, here we have the neocortex of
Ignacius.

1038
01:04:16,880 --> 01:04:20,120
It's very small. It's actually just
this part of the brain.

1039
01:04:20,120 --> 01:04:24,720
- In Ignacius, it covers about 20% of
the top of the brain.

1040
01:04:24,720 --> 01:04:27,480
That's very different in a human
brain, isn't it?

1041
01:04:27,480 --> 01:04:30,720
- Very, very different. You can see,
like, the neocortex in humans

1042
01:04:30,720 --> 01:04:33,200
actually is covering the entire rest
of the brain.

1043
01:04:33,200 --> 01:04:36,200
This is amazing, how big that it got
in humans.

1044
01:04:38,720 --> 01:04:42,120
- A rudimentary neocortex helped early
mammals

1045
01:04:42,120 --> 01:04:46,160
analyse the world around them and
respond to it.

1046
01:04:46,160 --> 01:04:49,720
For humans, it's become the seat of
advanced thinking,

1047
01:04:49,720 --> 01:04:52,240
reasoning and perception.

1048
01:04:52,240 --> 01:04:56,920
But the mystery is, why did our
neocortex grow so large

1049
01:04:56,920 --> 01:04:59,480
compared to any other mammal?

1050
01:04:59,480 --> 01:05:04,240
There's a compelling theory and it's
to do with climate change.

1051
01:05:05,240 --> 01:05:07,560
About 56 million years ago,

1052
01:05:07,560 --> 01:05:09,240
greenhouse gases,

1053
01:05:09,240 --> 01:05:11,480
released by volcanic activity,

1054
01:05:11,480 --> 01:05:13,920
caused sudden global warming

1055
01:05:13,920 --> 01:05:15,720
of up to five degrees.

1056
01:05:18,480 --> 01:05:21,640
It was the beginning of the Eocene Era
-

1057
01:05:21,640 --> 01:05:24,040
a time of astonishing changes.

1058
01:05:25,480 --> 01:05:28,560
In the hothouse environment of the
Eocene,

1059
01:05:28,560 --> 01:05:31,720
dense rainforests spread around the
world.

1060
01:05:31,720 --> 01:05:33,960
They even reached high enough
latitudes

1061
01:05:33,960 --> 01:05:36,560
to be within what is today the Arctic
Circle.

1062
01:05:36,560 --> 01:05:41,240
And, as with the rainforests of today,
life proliferated.

1063
01:05:42,720 --> 01:05:46,720
Just look at these extraordinary
fossils, found near Frankfurt

1064
01:05:46,720 --> 01:05:50,720
in Germany, dating nearly 50 million
years ago.

1065
01:05:50,720 --> 01:05:54,240
They give us an incredible insight
into the competition

1066
01:05:54,240 --> 01:05:57,480
which raged in the forests of the
early Eocene.

1067
01:06:00,240 --> 01:06:04,800
There were birds and agile,
tree-dwelling rodents.

1068
01:06:04,800 --> 01:06:07,720
There were highly-dangerous predators,
too.

1069
01:06:07,720 --> 01:06:11,960
All of this meant fierce competition
for food and resources

1070
01:06:11,960 --> 01:06:14,480
and, with all these new predators
around,

1071
01:06:14,480 --> 01:06:16,720
it was much more dangerous, too.

1072
01:06:16,720 --> 01:06:20,240
Only those creatures able to adapt
would survive.

1073
01:06:23,720 --> 01:06:26,120
In these changed circumstances,

1074
01:06:26,120 --> 01:06:30,720
simply staying alive would take brains
as well as brawn.

1075
01:06:35,200 --> 01:06:37,680
As I'm very quickly finding out,

1076
01:06:37,680 --> 01:06:40,480
a tree is a tricky place to call home.

1077
01:06:40,480 --> 01:06:43,480
It's actually quite difficult, moving
around up here.

1078
01:06:43,480 --> 01:06:45,960
It doesn't just take physical
strength,

1079
01:06:45,960 --> 01:06:48,960
you need judgment, you need to decide
whether a branch

1080
01:06:48,960 --> 01:06:51,040
is strong enough to hold your weight,

1081
01:06:51,040 --> 01:06:54,880
whether it's too wobbly, you need to
plan a route through the trees.

1082
01:06:54,880 --> 01:06:58,240
On top of the physical and mental
agility you need,

1083
01:06:58,240 --> 01:07:01,480
coping with the incredibly complex
visual field

1084
01:07:01,480 --> 01:07:05,240
of a canopy of leaves poses yet more
problems.

1085
01:07:05,240 --> 01:07:07,280
I'm finding it really difficult,

1086
01:07:07,280 --> 01:07:09,760
peering through the leaves and twigs
and branches.

1087
01:07:09,760 --> 01:07:13,560
Keeping an eye out for predators, as
well as foraging for food,

1088
01:07:13,560 --> 01:07:15,320
must have been a real challenge.

1089
01:07:16,960 --> 01:07:19,880
In the face of these evolutionary
pressures,

1090
01:07:19,880 --> 01:07:24,720
a new kind of creature appears in the
fossil record of the Eocene.

1091
01:07:26,240 --> 01:07:29,480
They're called crown primates - the
forerunners

1092
01:07:29,480 --> 01:07:32,960
of all today's primates - including,
of course, us.

1093
01:07:39,360 --> 01:07:41,280
Is this the way we sit?

1094
01:07:41,280 --> 01:07:43,320
Like this?

1095
01:07:43,320 --> 01:07:47,760
Early primates were well-adapted to
life in the trees.

1096
01:07:47,760 --> 01:07:52,600
What's interesting is the way he's
grasping the branch.

1097
01:07:56,240 --> 01:08:01,560
During the Eocene, primates evolved
gripping hands and feet with nails.

1098
01:08:09,960 --> 01:08:11,840
They're much more dextrous.

1099
01:08:11,840 --> 01:08:14,480
They're able to hold on to this
branch.

1100
01:08:14,480 --> 01:08:17,720
It also means they can use these hands
to find food,

1101
01:08:17,720 --> 01:08:21,040
to forage, to manipulate objects much
more easily.

1102
01:08:25,960 --> 01:08:28,720
The other thing to notice is that they
have eyes

1103
01:08:28,720 --> 01:08:31,560
at the front of their heads, not on
the side.

1104
01:08:32,560 --> 01:08:35,240
Animals with eyes on the side of their
heads

1105
01:08:35,240 --> 01:08:38,960
have a wider field of view and can
spot predators better.

1106
01:08:40,960 --> 01:08:44,320
But eyes at the front help with what's
ahead of you,

1107
01:08:44,320 --> 01:08:48,240
judging the distance to the next
branch or locating food.

1108
01:08:53,920 --> 01:08:57,640
The effect of millions of years of
tree-dwelling is clear

1109
01:08:57,640 --> 01:08:59,880
when we look at the fossil record.

1110
01:08:59,880 --> 01:09:04,240
This is the brain cast of Ignacius,
the plesiadapiform

1111
01:09:04,240 --> 01:09:07,120
we've already seen clambering around
the forest

1112
01:09:07,120 --> 01:09:10,240
in the years after the dinosaur
extinction.

1113
01:09:10,240 --> 01:09:15,240
And this is the brain cast of a
primate called Rooneyia.

1114
01:09:15,240 --> 01:09:19,240
It evolved around 20 million years
after Ignacius.

1115
01:09:20,240 --> 01:09:24,880
With Ignacius, the neocortex covered
20% of its brain.

1116
01:09:24,880 --> 01:09:28,960
With Rooneyia, it now covers half its
brain.

1117
01:09:32,240 --> 01:09:35,760
The neocortex analyses visual data...

1118
01:09:38,560 --> 01:09:41,440
..and it has many other functions
besides.

1119
01:09:42,440 --> 01:09:45,480
It works in extraordinarily complex
ways,

1120
01:09:45,480 --> 01:09:48,960
which we take for granted in our
everyday lives.

1121
01:09:50,480 --> 01:09:53,800
Take, for instance, what happens
inside our brains

1122
01:09:53,800 --> 01:09:56,480
when we do something as deceptively
simple

1123
01:09:56,480 --> 01:09:59,120
as reaching out and grabbing an apple.

1124
01:09:59,120 --> 01:10:02,240
It's actually far more complicated
than you might think.

1125
01:10:07,960 --> 01:10:11,480
I'm getting an extraordinary insight
into what's involved

1126
01:10:11,480 --> 01:10:14,280
when we reach out and grab something.

1127
01:10:15,280 --> 01:10:18,720
Dr David Pitcher at the University of
York has carried out

1128
01:10:18,720 --> 01:10:23,480
a functional MRI, which measures the
way the blood flows in my brain...

1129
01:10:24,560 --> 01:10:27,640
- OK, Jim, this is going to be an
eight-minute scan.

1130
01:10:27,640 --> 01:10:31,960
- ..while he plays me videos of
reaching out and grasping an apple.

1131
01:10:33,720 --> 01:10:37,120
- My colleague, Amelle, is going to
put this...
- Hello. Right.

1132
01:10:37,120 --> 01:10:38,720
- ..on your head.

1133
01:10:38,720 --> 01:10:41,680
- Then he uploads my results to this
machine...

1134
01:10:43,240 --> 01:10:46,480
..which uses spatial recognition
technology

1135
01:10:46,480 --> 01:10:49,400
to guide me around my own brain.

1136
01:10:49,400 --> 01:10:53,120
- Now where she points to with that
pointer...
- Ah!

1137
01:10:53,120 --> 01:10:55,480
- This is what your head looks like
inside.

1138
01:10:55,480 --> 01:10:58,240
- JIM LAUGHS Lovely death mask well,
isn't it?

1139
01:10:58,240 --> 01:11:01,160
- Oh, I can rotate that for you as
well, so we can see.

1140
01:11:01,160 --> 01:11:02,880
- DAVID LAUGHS

1141
01:11:02,880 --> 01:11:07,960
My scan shows astonishing activity
across my cerebral cortex

1142
01:11:07,960 --> 01:11:09,960
as I watch the video.

1143
01:11:09,960 --> 01:11:14,240
First, David shows me how my visual
processing works -

1144
01:11:14,240 --> 01:11:17,720
a complex system which really started
to develop

1145
01:11:17,720 --> 01:11:20,040
with those early primates.

1146
01:11:20,040 --> 01:11:22,240
- Light hits your eyeball,

1147
01:11:22,240 --> 01:11:25,120
that's then converted into neural
signalling.

1148
01:11:25,120 --> 01:11:28,240
That information is then sent down the
optic nerve,

1149
01:11:28,240 --> 01:11:30,480
all the way to primary visual cortex,

1150
01:11:30,480 --> 01:11:33,280
which, in humans, is right at the back
of your head.

1151
01:11:33,280 --> 01:11:37,720
- As I was looking at the apple, my
visual cortex connected

1152
01:11:37,720 --> 01:11:42,560
with another part of my brain which
helps us recognise objects.

1153
01:11:42,560 --> 01:11:44,720
- You see this pathway that lights up?

1154
01:11:44,720 --> 01:11:47,240
This is the ventral object recognition
pathway.

1155
01:11:47,240 --> 01:11:49,880
- And that pathway leads to the bit of
the brain

1156
01:11:49,880 --> 01:11:53,520
where I'm storing information of what
apples look like?
- Yeah.

1157
01:11:53,520 --> 01:11:57,120
- The hard drive of my brain.
- It's where we store everything,
yeah.

1158
01:11:57,120 --> 01:12:00,720
- Then a second connection activates
from the visual cortex

1159
01:12:00,720 --> 01:12:03,720
at the back of the brain to the
parietal lobe.

1160
01:12:03,720 --> 01:12:07,720
The parietal lobe judges where things
are in space around us

1161
01:12:07,720 --> 01:12:10,160
and where our body is positioned.

1162
01:12:10,160 --> 01:12:13,320
But to issue the orders to the body to
move,

1163
01:12:13,320 --> 01:12:15,760
you need a third part of the neocortex
-

1164
01:12:15,760 --> 01:12:18,240
the primary motor cortex.

1165
01:12:19,240 --> 01:12:21,400
- This is your motor cortex,

1166
01:12:21,400 --> 01:12:24,720
and there's parts that control all the
motor function in your body.

1167
01:12:24,720 --> 01:12:27,720
And if Amelle moves the pen down the
side of your head,

1168
01:12:27,720 --> 01:12:31,680
we're sort of tracking through
different parts of the motor cortex.

1169
01:12:31,680 --> 01:12:34,240
And where we come to...

1170
01:12:34,240 --> 01:12:36,960
..sort of roughly where Amelle is now,

1171
01:12:36,960 --> 01:12:39,120
that's roughly where the hand area is.

1172
01:12:39,120 --> 01:12:42,240
So that's the...
- So different parts of the motor
cortex

1173
01:12:42,240 --> 01:12:47,200
physically relate to different parts
of my body?
- Exactly.

1174
01:12:47,200 --> 01:12:50,720
- The visual, parietal and motor
cortex

1175
01:12:50,720 --> 01:12:53,960
all developed in our primate
ancestors,

1176
01:12:53,960 --> 01:12:58,720
and a new area of the neocortex was
also beginning to evolve.

1177
01:12:58,720 --> 01:13:01,480
It would become the most sophisticated

1178
01:13:01,480 --> 01:13:04,240
cognitive area of our brains.

1179
01:13:04,240 --> 01:13:06,040
- The other thing you have to do

1180
01:13:06,040 --> 01:13:08,720
is be able to plan and control the
motor action,

1181
01:13:08,720 --> 01:13:11,600
so if Amelle brings the pointer
forward a little bit,

1182
01:13:11,600 --> 01:13:14,720
is the prefrontal cortex. It's where
we do all our thinking,

1183
01:13:14,720 --> 01:13:18,000
it's where cognitive control happens
- the voice inside your head.

1184
01:13:20,240 --> 01:13:24,240
- So, just picking up an apple means
the visual cortex,

1185
01:13:24,240 --> 01:13:29,720
the parietal lobe, the motor cortex,
and the prefrontal cortex

1186
01:13:29,720 --> 01:13:32,240
all have to work together.

1187
01:13:33,720 --> 01:13:37,240
So four different parts of the brain

1188
01:13:37,240 --> 01:13:39,960
are all involved in the simple action

1189
01:13:39,960 --> 01:13:42,240
of reaching out and picking up an
apple -

1190
01:13:42,240 --> 01:13:47,040
visual cortex, parietal lobe, motor
cortex, frontal cortex.

1191
01:13:50,240 --> 01:13:52,240
From 40 million years ago,

1192
01:13:52,240 --> 01:13:54,760
the creatures we now call monkeys

1193
01:13:54,760 --> 01:13:55,960
were evolving.

1194
01:13:55,960 --> 01:13:58,640
Their neocortex was becoming bigger

1195
01:13:58,640 --> 01:14:00,960
and more complex in structure.

1196
01:14:01,960 --> 01:14:03,320
In today's primates,

1197
01:14:03,320 --> 01:14:04,720
the larger the brain,

1198
01:14:04,720 --> 01:14:07,960
the denser and more closely packed the
neurons,

1199
01:14:07,960 --> 01:14:11,960
the more networks they develop, the
cleverer they become.

1200
01:14:14,840 --> 01:14:17,640
So what were the driving factors

1201
01:14:17,640 --> 01:14:22,280
which caused some primates to evolve
differently from others?

1202
01:14:22,280 --> 01:14:25,480
And why did humans evolve the most
intelligence?

1203
01:14:25,480 --> 01:14:29,240
One theory has to do with the ability
to find the best,

1204
01:14:29,240 --> 01:14:32,720
most calorific food, and is something
we can study

1205
01:14:32,720 --> 01:14:37,120
by looking at two species of modern
monkeys side-by-side.

1206
01:14:37,120 --> 01:14:40,320
- So, this is the viewing deck, and
here we can see both species -

1207
01:14:40,320 --> 01:14:43,040
the capuchins and the squirrel
monkeys.

1208
01:14:44,560 --> 01:14:47,240
They're our relatives, but if we study
enough

1209
01:14:47,240 --> 01:14:50,240
of our primate relatives, we can start
to make inferences

1210
01:14:50,240 --> 01:14:53,480
about what our ancestors - our primate
ancestors -

1211
01:14:53,480 --> 01:14:55,040
might have been like.

1212
01:14:56,040 --> 01:14:59,880
- This is The Living Link Centre at
Edinburgh Zoo.

1213
01:14:59,880 --> 01:15:04,560
Professor Amanda Seed studies these
species side-by-side

1214
01:15:04,560 --> 01:15:08,120
to try to understand the story of our
own brains.

1215
01:15:08,120 --> 01:15:11,400
- The capuchin monkeys are our larger
monkeys, they're more robust.

1216
01:15:11,400 --> 01:15:15,120
They have this characteristic dark
colouring on their head

1217
01:15:15,120 --> 01:15:17,960
and a little tuft at the front. The
squirrel monkeys,

1218
01:15:17,960 --> 01:15:21,080
on the other hand, they're smaller,
they're more slender.

1219
01:15:21,080 --> 01:15:23,960
They look a little bit like they've
been dipped in chocolate.

1220
01:15:23,960 --> 01:15:27,040
- Capuchin monkeys and squirrel
monkeys evolved together

1221
01:15:27,040 --> 01:15:29,960
in the same place - the forests of the
new world,

1222
01:15:29,960 --> 01:15:33,960
and yet capuchins have a much larger
neocortex

1223
01:15:33,960 --> 01:15:38,720
compared to their body size and
exhibit greater intelligence.

1224
01:15:38,720 --> 01:15:40,720
The question is, why?

1225
01:15:40,720 --> 01:15:44,880
And what might that tell us about the
evolution of our own brains?

1226
01:15:44,880 --> 01:15:48,120
Amanda and her staff have devised a
challenge

1227
01:15:48,120 --> 01:15:50,960
these monkeys haven't encountered
before.

1228
01:15:50,960 --> 01:15:54,720
They've hidden food in papier mache
boxes.

1229
01:15:54,720 --> 01:15:58,000
The challenge is, which species will
figure out

1230
01:15:58,000 --> 01:16:00,960
that there's food inside and manage to
get it?

1231
01:16:05,240 --> 01:16:07,640
- Straight in.
- "Thank you very much."

1232
01:16:11,720 --> 01:16:14,600
- Straight away, the capuchins have
come out.

1233
01:16:16,520 --> 01:16:19,720
They're very, very curious and their
first thought is,

1234
01:16:19,720 --> 01:16:22,000
"Can I break it? Is there food
inside?"

1235
01:16:25,720 --> 01:16:29,640
- Meanwhile, the squirrel monkeys hang
around on the sides,

1236
01:16:29,640 --> 01:16:32,520
and not one of them looks inside a
box.

1237
01:16:32,520 --> 01:16:36,040
Instead, they wait for the capuchins
to finish feasting

1238
01:16:36,040 --> 01:16:39,040
and they pick up scraps from their
table.

1239
01:16:40,720 --> 01:16:45,040
Amanda believes today's test has
helped confirm a theory

1240
01:16:45,040 --> 01:16:47,720
which links intelligence to diet.

1241
01:16:47,720 --> 01:16:51,720
- The capuchins rely on fruit to a
much greater extent

1242
01:16:51,720 --> 01:16:54,400
than the squirrel monkeys. The
squirrel monkeys

1243
01:16:54,400 --> 01:16:58,000
eat fruit as well, but their diet is
largely comprised of insects.

1244
01:16:58,000 --> 01:17:01,480
- The squirrel monkeys just have to
wait for an insect to come along

1245
01:17:01,480 --> 01:17:04,480
and grab it, and that happens a lot,

1246
01:17:04,480 --> 01:17:08,240
but fruit only appears a few months
every year.

1247
01:17:08,240 --> 01:17:10,880
It's found around the forest in
patches,

1248
01:17:10,880 --> 01:17:13,480
in often hard-to-find places.

1249
01:17:13,480 --> 01:17:18,240
So, in order to find it, you have to
remember and plan ahead.

1250
01:17:19,240 --> 01:17:22,720
- An ability to map your environment
and space,

1251
01:17:22,720 --> 01:17:26,240
and even time, to be able to predict
when those resources

1252
01:17:26,240 --> 01:17:29,240
are going to become available now
becomes useful,

1253
01:17:29,240 --> 01:17:31,720
and so now we have more selective
pressure

1254
01:17:31,720 --> 01:17:34,360
for areas of the brain that can deal
with that.

1255
01:17:34,360 --> 01:17:37,480
- The penny's starting to drop for me
now, that it's not so much

1256
01:17:37,480 --> 01:17:40,960
that they have larger brains, they're
smarter, therefore they're

1257
01:17:40,960 --> 01:17:44,160
able to figure out things like, you
know, how to find food.

1258
01:17:44,160 --> 01:17:47,120
The need to look for food has
stimulated the growth

1259
01:17:47,120 --> 01:17:50,560
of a larger brain over millions of
years.
- Over millions of years.

1260
01:17:51,880 --> 01:17:55,320
- So it may be that at some point in
our evolution,

1261
01:17:55,320 --> 01:17:58,240
our ancestors were like the capuchins,

1262
01:17:58,240 --> 01:18:01,560
they concentrated more and more on
fruit -

1263
01:18:01,560 --> 01:18:04,720
high-calorie fuel for growing brains -

1264
01:18:04,720 --> 01:18:07,720
but it takes more intelligence to
find.

1265
01:18:09,480 --> 01:18:11,600
By 25 million years ago,

1266
01:18:11,600 --> 01:18:14,240
the first apes were evolving.

1267
01:18:14,240 --> 01:18:15,880
Ape brains are generally

1268
01:18:15,880 --> 01:18:17,240
larger than monkeys

1269
01:18:17,240 --> 01:18:19,080
and they have more complex

1270
01:18:19,080 --> 01:18:20,960
structures and networks.

1271
01:18:24,480 --> 01:18:27,240
It's now thought that around this
time,

1272
01:18:27,240 --> 01:18:30,240
our ancestors took their first baby
steps

1273
01:18:30,240 --> 01:18:34,040
towards one of our most important
cognitive abilities -

1274
01:18:34,040 --> 01:18:36,640
complex spoken language.

1275
01:18:42,240 --> 01:18:45,240
I've come to see something very
unexpected,

1276
01:18:45,240 --> 01:18:47,960
which might provide a vital clue.

1277
01:18:50,240 --> 01:18:54,440
These gorillas live at Port Lympne
Safari Park in Kent.

1278
01:18:55,440 --> 01:18:58,040
I'm with Professor Gillian Forrester,

1279
01:18:58,040 --> 01:19:01,720
who's been studying the primates at
this sanctuary for 20 years.

1280
01:19:01,720 --> 01:19:04,480
- I really like working here at Port
Lympne,

1281
01:19:04,480 --> 01:19:09,240
because it feels like more of a
collaboration with the gorillas.

1282
01:19:09,240 --> 01:19:13,480
We work together, but they're in an
environment that really suits them.

1283
01:19:13,480 --> 01:19:17,680
The enclosure was made for them, not
for people to view them.
- Right.

1284
01:19:21,240 --> 01:19:25,240
It's lunchtime, and the gorillas have
an unusual treat.

1285
01:19:29,240 --> 01:19:32,480
Nettles - which they find very tasty.

1286
01:19:35,240 --> 01:19:39,480
They've found a clever strategy to
deal with their stinging leaves.

1287
01:19:42,240 --> 01:19:45,960
They strip the nettles off the stem in
one direction -

1288
01:19:45,960 --> 01:19:48,720
a direction which doesn't trigger the
spines,

1289
01:19:48,720 --> 01:19:50,240
so they don't get stung.

1290
01:19:51,480 --> 01:19:55,280
One gorilla decides to literally walk
away with her spoils.

1291
01:19:55,280 --> 01:19:58,240
"These are mine."
- Look at her go!
- Fantastic!

1292
01:19:59,240 --> 01:20:02,240
We follow this gorilla to the inside
area,

1293
01:20:02,240 --> 01:20:07,480
where we catch a glimpse of a more
complex form of nettle preparation.

1294
01:20:08,480 --> 01:20:13,240
Rolling the leaves into a ball to
crush the stinging spines.

1295
01:20:13,240 --> 01:20:16,720
This method of preparing nettles has
been recorded

1296
01:20:16,720 --> 01:20:18,960
in many different gorilla groups.

1297
01:20:24,880 --> 01:20:27,480
And you want me to try this, don't
you?
- Yeah.

1298
01:20:27,480 --> 01:20:30,560
- OK, right, let's see how we go.
- Let's see.

1299
01:20:30,560 --> 01:20:33,120
- Ah! Well, OK, there we go.

1300
01:20:33,120 --> 01:20:36,840
I was so careful not to get stung,
which I think I've survived,

1301
01:20:36,840 --> 01:20:40,120
but I've dropped the leaves.
- Dropped the leaves, yeah.

1302
01:20:42,560 --> 01:20:45,760
Not as delicate as you.
- No, but...
- But nearly there.
- Yeah.

1303
01:20:45,760 --> 01:20:50,240
- I think it's interesting because
eating the nettles requires

1304
01:20:50,240 --> 01:20:54,960
the gorillas to take certain actions
in order to not get stung.
- OK.

1305
01:20:54,960 --> 01:20:57,560
- We could think of that as almost
like

1306
01:20:57,560 --> 01:21:00,200
what we'd call a syntax in language.

1307
01:21:00,200 --> 01:21:04,240
When I speak, these are motor action
sequences.

1308
01:21:04,240 --> 01:21:08,320
So my mouth has to make the right
words at the right time

1309
01:21:08,320 --> 01:21:11,160
in order for you to understand what
I'm saying.

1310
01:21:11,160 --> 01:21:13,240
This is a syntax in language,

1311
01:21:13,240 --> 01:21:16,400
and this is a syntax in its physical
form.

1312
01:21:17,400 --> 01:21:20,240
- Gillian has created some puzzle
boards,

1313
01:21:20,240 --> 01:21:24,240
which require an understanding of more
complicated syntax

1314
01:21:24,240 --> 01:21:26,120
than nettle-stripping.

1315
01:21:26,120 --> 01:21:29,040
The boards have a series of cogs.

1316
01:21:29,040 --> 01:21:33,480
The question is, can great apes turn
them in the right direction,

1317
01:21:33,480 --> 01:21:36,080
in the right order, to solve the
puzzles?

1318
01:21:36,080 --> 01:21:38,800
- Sorry, Jim, but you've got that the
wrong way 'round.

1319
01:21:38,800 --> 01:21:40,600
- Argh!

1320
01:21:40,600 --> 01:21:42,000
GILLIAN LAUGHS

1321
01:21:42,000 --> 01:21:46,040
We're trying out her puzzle boards on
two orangutan brothers -

1322
01:21:46,040 --> 01:21:47,840
Malu and Haddy.

1323
01:21:47,840 --> 01:21:49,560
- Oh, here they are.

1324
01:21:54,720 --> 01:21:57,960
- Oh, look at that.
- Oh, they're right in there.
- Straight away.

1325
01:21:57,960 --> 01:22:00,760
They've spotted the nuts, which
Gillian has put

1326
01:22:00,760 --> 01:22:02,960
at the top of the puzzle boards.

1327
01:22:02,960 --> 01:22:04,720
But, to get them out,

1328
01:22:04,720 --> 01:22:08,120
they'll have to manoeuvre the nuts to
the bottom of the board.

1329
01:22:09,120 --> 01:22:12,880
On his board, Haddy tries using a twig
as a tool,

1330
01:22:12,880 --> 01:22:14,960
but that's not going to work.

1331
01:22:16,480 --> 01:22:20,880
Over on the other board, Malu lands on
the correct solution.

1332
01:22:20,880 --> 01:22:25,040
Oh, look at that.
- OK, that's Malu.
- Wow.
- Malu's worked that out.

1333
01:22:25,040 --> 01:22:26,960
- Well done.
- Here we go.

1334
01:22:27,960 --> 01:22:32,120
Malu's got into the second set of
cogs, and now he...

1335
01:22:32,120 --> 01:22:35,240
Oh, look how quick!
- Oh, my word!

1336
01:22:36,240 --> 01:22:39,560
- I can't believe how fluid his
movements are.

1337
01:22:43,720 --> 01:22:45,960
He's getting to the last stage now.

1338
01:22:45,960 --> 01:22:48,120
This is the double cog, the exciting
bit.

1339
01:22:48,120 --> 01:22:51,480
Will he think about...? Yes, he's
thought about which way to turn it.

1340
01:22:51,480 --> 01:22:53,720
- Ah!
- He's gone to the access point.

1341
01:22:53,720 --> 01:22:55,880
This could be the solution.

1342
01:22:57,720 --> 01:23:00,560
OK, he's been...
- I mean, the last...

1343
01:23:00,560 --> 01:23:04,720
Oh, look, at the last stage...
- No!
- ..and big brother has taken over.

1344
01:23:04,720 --> 01:23:08,960
- Big brother's taken over and Haddy
is going to get the reward.

1345
01:23:12,240 --> 01:23:16,440
- But between them, they've solved it.
- Yes, it was a collaboration!

1346
01:23:16,440 --> 01:23:18,120
- GILLIAN LAUGHS

1347
01:23:18,120 --> 01:23:21,240
Gillian is convinced that our ape
ancestors

1348
01:23:21,240 --> 01:23:25,280
developed the ability to solve ever
more complicated

1349
01:23:25,280 --> 01:23:29,720
physical syntax problems and were
unknowingly building

1350
01:23:29,720 --> 01:23:34,480
the foundations of what would one day
become language.

1351
01:23:35,960 --> 01:23:38,880
Our ancestors split from orangutans

1352
01:23:38,880 --> 01:23:41,120
around 17 million years ago

1353
01:23:41,120 --> 01:23:42,400
and from gorillas

1354
01:23:42,400 --> 01:23:44,440
about ten million years ago.

1355
01:23:45,440 --> 01:23:49,720
Again, climate change was bringing new
threats.

1356
01:23:49,720 --> 01:23:53,240
Millions of years of slow global
cooling

1357
01:23:53,240 --> 01:23:55,720
meant that rainforests were
retreating,

1358
01:23:55,720 --> 01:23:59,440
to be replaced by open grasslands and
woodland.

1359
01:23:59,440 --> 01:24:04,240
Competition for the most nutritious
and calorific foods

1360
01:24:04,240 --> 01:24:07,720
in the rainforest was becoming ever
more intense.

1361
01:24:07,720 --> 01:24:12,120
Life for our primate ancestors was
getting harder and harder.

1362
01:24:14,480 --> 01:24:19,120
Survival would now depend on making
finely-balanced judgments

1363
01:24:19,120 --> 01:24:22,920
based on limited information about
where to find food.

1364
01:24:24,720 --> 01:24:28,240
To find out what mark climate change
made on our brains,

1365
01:24:28,240 --> 01:24:30,240
I'm visiting the chimpanzees

1366
01:24:30,240 --> 01:24:33,640
who live at Budongo Research Unit at
Edinburgh Zoo.

1367
01:24:34,640 --> 01:24:38,360
Along with bonobos, they're our
closest primate relatives.

1368
01:24:39,360 --> 01:24:41,720
I've been told I can play a game with
them

1369
01:24:41,720 --> 01:24:43,800
to test their cognitive powers...

1370
01:24:43,800 --> 01:24:46,320
Not one of you has said thank you yet.

1371
01:24:46,320 --> 01:24:50,480
..so I head to the indoor part of
their living quarters.

1372
01:24:50,480 --> 01:24:55,280
When the chimps start making their
noises, it is really loud in here.

1373
01:24:55,280 --> 01:24:57,760
CHIMPANZEES SCREECH

1374
01:24:58,760 --> 01:25:03,280
The chimpanzees have complete freedom
to do as they like here,

1375
01:25:03,280 --> 01:25:06,720
so I have to wait to see if one of
them wants to join me.

1376
01:25:06,720 --> 01:25:08,720
CHIMPANZEE GRUNTS

1377
01:25:12,480 --> 01:25:17,040
Eventually, four-year-old Masindi
decides she wants to play.

1378
01:25:17,040 --> 01:25:19,040
Masindi, look.

1379
01:25:19,040 --> 01:25:22,760
To get the game started, I show her
two empty cups.

1380
01:25:22,760 --> 01:25:24,400
Nothing.

1381
01:25:24,400 --> 01:25:27,240
Then I cover them with a screen...

1382
01:25:27,240 --> 01:25:29,800
..and put a grape under one of them.

1383
01:25:29,800 --> 01:25:31,560
Do you feel lucky?

1384
01:25:31,560 --> 01:25:35,760
I'll put it under this one, pretend to
put it under this one.

1385
01:25:35,760 --> 01:25:39,240
She doesn't know which cup has the
grape,

1386
01:25:39,240 --> 01:25:41,640
so she guesses the cup on the left.

1387
01:25:41,640 --> 01:25:43,320
That one? OK.

1388
01:25:43,320 --> 01:25:45,680
But now I complicate things.

1389
01:25:45,680 --> 01:25:47,560
I move this cup back?
- Yeah.

1390
01:25:47,560 --> 01:25:52,120
- I remove the cup she doesn't want
and offer her an alternative -

1391
01:25:52,120 --> 01:25:53,720
a half-grape.

1392
01:25:53,720 --> 01:25:55,600
Now what do you want?

1393
01:25:55,600 --> 01:25:57,480
So now she has a choice -

1394
01:25:57,480 --> 01:26:00,720
pick up a cup which may or may not
have a grape under it,

1395
01:26:00,720 --> 01:26:03,960
or settle for a guaranteed half-grape.

1396
01:26:04,960 --> 01:26:06,480
This one?

1397
01:26:06,480 --> 01:26:08,240
That one, you want?

1398
01:26:08,240 --> 01:26:10,960
OK, well, look... Look what you could
have won.

1399
01:26:10,960 --> 01:26:13,240
But, unfortunately, you have a half.

1400
01:26:13,240 --> 01:26:15,120
She's chosen the half-grape.

1401
01:26:15,120 --> 01:26:16,960
It's a safe decision,

1402
01:26:16,960 --> 01:26:20,240
but she's missed the chance of winning
a full one.

1403
01:26:21,240 --> 01:26:24,480
And that's the choice they have to
make - whether they want

1404
01:26:24,480 --> 01:26:28,760
half a grape for sure or a whole grape
half of the time.

1405
01:26:28,760 --> 01:26:32,880
We play the game again, and this time,
she sticks with the cup.

1406
01:26:34,240 --> 01:26:36,960
You're going for it, are you? Are you
confident?

1407
01:26:38,240 --> 01:26:39,640
Clever!

1408
01:26:39,640 --> 01:26:43,240
Of course, Masindi's having to guess
if the cup has a grape under it.

1409
01:26:43,240 --> 01:26:47,800
But now, what happens if I give her
more information to act on?

1410
01:26:49,480 --> 01:26:53,320
I offer her two cups with one grape,
as usual,

1411
01:26:53,320 --> 01:26:57,200
but this time I show her that one of
them is empty.

1412
01:27:01,520 --> 01:27:04,240
Let's see. This is... This is going to
be the clincher.

1413
01:27:04,240 --> 01:27:05,880
What are you going to...?

1414
01:27:05,880 --> 01:27:07,960
Good girl! You... Yes!

1415
01:27:07,960 --> 01:27:10,560
You've got it. Well done!

1416
01:27:10,560 --> 01:27:14,560
She immediately realises that the
other cup must be hiding the grape.

1417
01:27:14,560 --> 01:27:17,120
She knew there was definitely a grape
under this one,

1418
01:27:17,120 --> 01:27:19,480
so a choice between that and the
half-grape,

1419
01:27:19,480 --> 01:27:22,760
she's sticking with the cup because
she knows there's a grape under it.

1420
01:27:23,760 --> 01:27:26,240
The chimps also play video games...

1421
01:27:27,480 --> 01:27:31,240
..which simulate complicated foraging
tasks...

1422
01:27:33,240 --> 01:27:37,240
..looking for hidden fruit scattered
around a complex landscape.

1423
01:27:41,240 --> 01:27:43,960
The game is helping investigate the
theory

1424
01:27:43,960 --> 01:27:49,040
that as the rainforests retreated, the
need to find scarcer food

1425
01:27:49,040 --> 01:27:53,560
required greater brain power, memory
and planning ahead.

1426
01:27:58,240 --> 01:28:01,240
These games are posing a vital
question -

1427
01:28:01,240 --> 01:28:05,880
are the chimps able to keep track of
their own awareness of the world?

1428
01:28:06,960 --> 01:28:10,240
What they know and what they don't
know.

1429
01:28:12,480 --> 01:28:16,240
The ability to keep track of what you
know and don't know

1430
01:28:16,240 --> 01:28:20,240
is a vital and mysterious part of
human intelligence

1431
01:28:20,240 --> 01:28:22,720
known as metacognition.

1432
01:28:22,720 --> 01:28:25,480
It's something which particularly
interests

1433
01:28:25,480 --> 01:28:28,720
the head of the research unit,
Professor Josep Call.

1434
01:28:28,720 --> 01:28:31,080
- Metacognition is the ability

1435
01:28:31,080 --> 01:28:35,480
to monitor and control your own
thought processes,

1436
01:28:35,480 --> 01:28:37,720
your own mental content.

1437
01:28:37,720 --> 01:28:40,240
There is a thing called - in
metacognition -

1438
01:28:40,240 --> 01:28:43,280
that is called the tip-of-the-tongue
phenomenon.

1439
01:28:43,280 --> 01:28:45,560
When somebody asks you a question, and
you say,

1440
01:28:45,560 --> 01:28:49,120
"I cannot give you the answer, but I
know that I know this answer"...

1441
01:28:49,120 --> 01:28:51,800
- It happens all the time.
- Yes, there you go.

1442
01:28:51,800 --> 01:28:54,880
This is metacognition, where even
though you cannot

1443
01:28:54,880 --> 01:28:58,960
produce the answer, you know that you
know the answer.

1444
01:28:59,960 --> 01:29:03,720
- One theory states that our ancestors
developed metacognition

1445
01:29:03,720 --> 01:29:07,120
as they solved problems posed by the
environment,

1446
01:29:07,120 --> 01:29:10,400
such as finding fruit in changing
landscapes.

1447
01:29:10,400 --> 01:29:15,720
It's thought this led to what's known
as the Theory of Mind -

1448
01:29:15,720 --> 01:29:20,960
the awareness not just of your own
mind, but others' minds, too.

1449
01:29:23,480 --> 01:29:26,240
- It's about knowing about your own
processes

1450
01:29:26,240 --> 01:29:29,400
but also inputting processes to
others.

1451
01:29:29,400 --> 01:29:33,240
What others can see, what others want,

1452
01:29:33,240 --> 01:29:36,200
what others intend, what others
believe.

1453
01:29:39,960 --> 01:29:43,720
- Thinking about others is a crucial
step towards becoming

1454
01:29:43,720 --> 01:29:48,240
the socially-connected creatures which
human beings are today.

1455
01:29:51,720 --> 01:29:55,480
Our ancestors split from the lineage
of chimpanzees

1456
01:29:55,480 --> 01:29:58,640
around six to eight million years ago.

1457
01:29:58,640 --> 01:30:02,480
After that came a huge change in
lifestyle -

1458
01:30:02,480 --> 01:30:05,880
a change with astonishing
consequences.

1459
01:30:05,880 --> 01:30:10,240
No-one knows exactly how, why or when
it happened,

1460
01:30:10,240 --> 01:30:12,880
but at some point during the millions
of years

1461
01:30:12,880 --> 01:30:17,240
after our own lineage split from that
of chimpanzees and bonobos,

1462
01:30:17,240 --> 01:30:19,960
our ancestors left the forests

1463
01:30:19,960 --> 01:30:23,240
to make a new life out on the open
plains.

1464
01:30:23,240 --> 01:30:26,720
They become bipedal, walking up on two
legs,

1465
01:30:26,720 --> 01:30:31,520
so better able to adapt to different
terrains and environments.

1466
01:30:31,520 --> 01:30:33,320
Between two and three million

1467
01:30:33,320 --> 01:30:34,640
years ago,

1468
01:30:34,640 --> 01:30:36,960
homo habilis was evolving -

1469
01:30:36,960 --> 01:30:39,120
the first human species.

1470
01:30:40,920 --> 01:30:45,120
They were developing areas of the
neocortex involved in planning,

1471
01:30:45,120 --> 01:30:47,240
thinking, problem-solving,

1472
01:30:47,240 --> 01:30:53,080
and we start to see some astonishing
results of improved brainpower.

1473
01:30:54,960 --> 01:30:58,480
Dr Nada Khreisheh is an experimental
archaeologist.

1474
01:30:58,480 --> 01:31:02,720
She works at the Ancient Technology
Centre in Dorset.

1475
01:31:08,960 --> 01:31:12,240
I'm meeting up again with Gillian
Forrester.

1476
01:31:12,240 --> 01:31:17,360
She and Nada have both investigated
the fascinating links between tools

1477
01:31:17,360 --> 01:31:19,880
and the story of our brain.

1478
01:31:19,880 --> 01:31:22,960
- So, Jim, I'm really excited to
introduce you to Nada.

1479
01:31:22,960 --> 01:31:25,600
She works in this beautiful place,

1480
01:31:25,600 --> 01:31:30,120
and she actually teaches people how to
make these ancient toolsets.
- Wow.

1481
01:31:30,120 --> 01:31:31,400
OK, teach me.

1482
01:31:31,400 --> 01:31:34,320
- So, we'll just start with a brief
history

1483
01:31:34,320 --> 01:31:36,800
of some of the ancient types of stone
tool

1484
01:31:36,800 --> 01:31:39,240
that were made by our hominid
ancestors.

1485
01:31:39,240 --> 01:31:42,120
This is a core, a thin core, where
sharp pieces,

1486
01:31:42,120 --> 01:31:45,120
as you can see down on the floor here,
have been knocked off,

1487
01:31:45,120 --> 01:31:47,960
and these sharp pieces were used as
tools for cutting.

1488
01:31:47,960 --> 01:31:51,240
- I want to know how much brainpower
it takes

1489
01:31:51,240 --> 01:31:55,040
to create the kind of tools which our
ancestors made,

1490
01:31:55,040 --> 01:32:00,960
so Nada sets me a task to make this
half-finished hand axe thinner.

1491
01:32:03,600 --> 01:32:06,520
- So, yeah, you can see that that's...
- NADA LAUGHS

1492
01:32:06,520 --> 01:32:08,120
- ..not coming off.

1493
01:32:08,120 --> 01:32:11,720
- It's not brute force.
- It's not just brute force,
unfortunately.

1494
01:32:11,720 --> 01:32:14,160
Ooh. You're breaking the hammer stone.

1495
01:32:15,160 --> 01:32:19,040
- So he's actually broken the hammer
stone and not the actual flint.

1496
01:32:19,040 --> 01:32:21,240
- Which is quite an achievement,
really.

1497
01:32:21,240 --> 01:32:22,680
- LAUGHTER

1498
01:32:22,680 --> 01:32:25,320
- So, as you can see, just hitting it
as hard as you can

1499
01:32:25,320 --> 01:32:28,400
directly on the spot which you want to
remove...
- Isn't working.

1500
01:32:28,400 --> 01:32:31,000
- ..isn't the right approach, really.
- NADA CHUCKLES

1501
01:32:32,720 --> 01:32:36,240
Making the flint break in the
direction you want it to

1502
01:32:36,240 --> 01:32:39,240
turns out to be extremely complicated.

1503
01:32:39,240 --> 01:32:43,120
- It might seem counterintuitive, but
you actually have to hit it

1504
01:32:43,120 --> 01:32:46,760
from this side to be able to thin it
effectively.
- Ah.

1505
01:32:46,760 --> 01:32:50,320
- And before we do that even, we need
to prepare a place for us to hit,

1506
01:32:50,320 --> 01:32:52,960
to take a piece, which should travel
down there

1507
01:32:52,960 --> 01:32:55,480
and thin the flint, if I do it right.

1508
01:32:55,480 --> 01:32:58,160
I just need to do a few more
preparatory flakes.

1509
01:32:58,160 --> 01:33:03,240
- Only after a few minutes of careful
preparation can she do this.

1510
01:33:03,240 --> 01:33:06,960
- I'm going to hit on the top, and
that's taken a piece...
- Ooh.

1511
01:33:06,960 --> 01:33:10,480
- ..which hasn't travelled as far as I
want, but it's kind of isolated

1512
01:33:10,480 --> 01:33:13,200
this spot a bit more, so made it stick
out a bit more.
- Mmm.

1513
01:33:15,360 --> 01:33:18,400
- A lot of times, when people think of
stone tools, they're thinking

1514
01:33:18,400 --> 01:33:21,320
of cavemen, they're thinking of mighty
muscles - big, hard hit -

1515
01:33:21,320 --> 01:33:23,720
but it's also about planning and
thinking ahead.

1516
01:33:23,720 --> 01:33:26,960
- Gillian believes this supports the
theory that our ancestors

1517
01:33:26,960 --> 01:33:28,960
were using cognitive abilities

1518
01:33:28,960 --> 01:33:32,560
which had developed millions of years
beforehand.

1519
01:33:32,560 --> 01:33:35,960
As we've seen, our shared primate
ancestors

1520
01:33:35,960 --> 01:33:38,720
had likely already developed an
ability

1521
01:33:38,720 --> 01:33:41,320
to master syntactical problems.

1522
01:33:41,320 --> 01:33:44,960
- We've looked at nettle processing...
- Yeah.
- ..with the gorillas,

1523
01:33:44,960 --> 01:33:47,960
we've looked at puzzle-solving with
orangutans,

1524
01:33:47,960 --> 01:33:51,040
and now we're looking here at stone
toolmaking.

1525
01:33:51,040 --> 01:33:54,240
They might seem like very, very
different kinds of behaviours

1526
01:33:54,240 --> 01:33:58,000
on the surface, but they have a
commonality.

1527
01:33:58,000 --> 01:34:01,720
And that common point is that they
require us

1528
01:34:01,720 --> 01:34:06,120
to put actions in the right order, and
that's not different from

1529
01:34:06,120 --> 01:34:11,080
how we put words in the right order to
make meaning out of a sentence.

1530
01:34:14,480 --> 01:34:17,640
- Gillian believes that during our
evolution,

1531
01:34:17,640 --> 01:34:21,240
carrying out problem-solving actions
with our hands

1532
01:34:21,240 --> 01:34:24,920
led to our ability to produce spoken
language.

1533
01:34:28,480 --> 01:34:31,720
She has intriguing evidence from brain
scans,

1534
01:34:31,720 --> 01:34:35,880
which she explains to me using the 3D
model of my own brain.

1535
01:34:36,880 --> 01:34:39,080
- This is your brain, as you well
know.

1536
01:34:39,080 --> 01:34:41,960
We've got the back of it here and the
front of it here,

1537
01:34:41,960 --> 01:34:46,480
and running right down the middle,
here, is your motor cortex.

1538
01:34:46,480 --> 01:34:49,320
This is telling your body to move,
effectively.

1539
01:34:49,320 --> 01:34:51,240
The hand area and the mouth area,

1540
01:34:51,240 --> 01:34:53,520
they're really quite close to one
another,

1541
01:34:53,520 --> 01:34:55,880
and just in front of that area here

1542
01:34:55,880 --> 01:35:00,240
is a region that we call Broca's area,
or Broca's region.

1543
01:35:00,240 --> 01:35:05,120
It's always been thought to be a
language-specific region.

1544
01:35:05,120 --> 01:35:08,240
It is activated when we speak.

1545
01:35:08,240 --> 01:35:12,240
But, interestingly, it is also
activated

1546
01:35:12,240 --> 01:35:15,640
when a deaf signer signs their
language.

1547
01:35:15,640 --> 01:35:19,840
It doesn't seem to matter if you're
vocalising or gesturing.

1548
01:35:19,840 --> 01:35:21,880
It likes syntax.

1549
01:35:22,880 --> 01:35:25,960
- Broca's region is also activated
when we carry out

1550
01:35:25,960 --> 01:35:29,720
any sequential syntactic tasks with
our hands.

1551
01:35:32,960 --> 01:35:36,720
As part of an investigation into the
evolution of our brains,

1552
01:35:36,720 --> 01:35:40,240
Nada co-authored a huge study of
volunteers,

1553
01:35:40,240 --> 01:35:44,720
who did 100 hours of training in stone
knapping.

1554
01:35:44,720 --> 01:35:47,200
- So one before they'd done any flint
knapping

1555
01:35:47,200 --> 01:35:50,560
and one after almost 100 hours of
flint knapping,

1556
01:35:50,560 --> 01:35:54,240
and we could see activations in
Broca's area and changes -

1557
01:35:54,240 --> 01:35:56,360
so, development in that area as well.

1558
01:35:56,360 --> 01:35:58,040
- It's fascinating, isn't it?

1559
01:35:58,040 --> 01:36:02,960
This connection between language,
vocalisation and hand movements,

1560
01:36:02,960 --> 01:36:06,000
I'm doing it now as I talk, there is a
connection,

1561
01:36:06,000 --> 01:36:09,960
and it's the same part of the brain
that's controlling different actions

1562
01:36:09,960 --> 01:36:14,240
that I do with my hands and the words
that come out of my mouth.

1563
01:36:14,240 --> 01:36:18,760
- A lot of people's mouths will mimic
what their fingers are doing.

1564
01:36:18,760 --> 01:36:22,560
For example, if you were sewing and
you had to thread a needle...

1565
01:36:22,560 --> 01:36:24,760
- LAUGHTER
Exactly.

1566
01:36:24,760 --> 01:36:28,120
- You're going to purse your lips when
you've got a tight space

1567
01:36:28,120 --> 01:36:31,240
and you're going to maybe open your
lips more

1568
01:36:31,240 --> 01:36:34,120
when you're grabbing larger objects.

1569
01:36:34,120 --> 01:36:38,640
This could possibly date all the way
back to just feeding behaviour.

1570
01:36:38,640 --> 01:36:41,520
If you're going to pick up something
small and put it in.

1571
01:36:41,520 --> 01:36:44,960
If you're picking up something big,
you need to open your mouth wider.

1572
01:36:44,960 --> 01:36:49,240
We also have this evolutionary theory
that we might have been first

1573
01:36:49,240 --> 01:36:54,120
speaking with our hands, before
language moved to our mouths.

1574
01:36:54,120 --> 01:36:56,720
Only a small portion of the way we
communicate

1575
01:36:56,720 --> 01:36:59,120
is actually through our vocalisations.

1576
01:36:59,120 --> 01:37:02,240
We're still communicating a huge
amount about what we think

1577
01:37:02,240 --> 01:37:05,480
and feel and intend through our facial
expressions,

1578
01:37:05,480 --> 01:37:08,480
our body postures and the way we move.

1579
01:37:09,480 --> 01:37:13,880
- So the theory is that carrying out
complex tasks like toolmaking

1580
01:37:13,880 --> 01:37:17,240
helped put in place the final bit of
the brain

1581
01:37:17,240 --> 01:37:19,720
which would be needed for language.

1582
01:37:23,240 --> 01:37:25,720
Over the past two million years,

1583
01:37:25,720 --> 01:37:28,880
our ancestors' brains tripled in size.

1584
01:37:30,720 --> 01:37:33,720
Particularly in the advanced cognitive
areas,

1585
01:37:33,720 --> 01:37:35,880
such as the prefrontal cortex.

1586
01:37:37,480 --> 01:37:39,960
So, why did this happen?

1587
01:37:39,960 --> 01:37:43,360
One compelling theory lies in the
large groups

1588
01:37:43,360 --> 01:37:46,240
which hunter-gatherer societies formed

1589
01:37:46,240 --> 01:37:48,960
and which we've inherited today.

1590
01:37:48,960 --> 01:37:52,120
It's known as the Social Brain Theory,

1591
01:37:52,120 --> 01:37:56,000
and it's something I'm about to
explore in a very personal way.

1592
01:37:56,000 --> 01:37:58,080
I've been working on these
documentaries now

1593
01:37:58,080 --> 01:37:59,480
for nearly 20 years.

1594
01:37:59,480 --> 01:38:01,200
I've worked with all sorts of people.

1595
01:38:01,200 --> 01:38:04,160
This is the first time I'm working
with someone I know very well -

1596
01:38:04,160 --> 01:38:07,520
my wife Julie. We've been together for
over 40 years.

1597
01:38:07,520 --> 01:38:11,880
I was asked to bring along either a
good friend or my wife,

1598
01:38:11,880 --> 01:38:14,480
and I don't have any good friends. JIM
LAUGHS

1599
01:38:14,480 --> 01:38:18,840
- Yeah, not really.
- You weren't completely happy to come
along.

1600
01:38:18,840 --> 01:38:21,520
- It's not my kind of thing.
- You're not a show-off like me.

1601
01:38:21,520 --> 01:38:24,800
- No, I'm not a show-off like you. Not
many people are a show-off like you.

1602
01:38:24,800 --> 01:38:28,040
- Anyway, I hope you know what you're
letting yourself in for this time.

1603
01:38:28,040 --> 01:38:29,960
- Not really, but I might finally get
to find out

1604
01:38:29,960 --> 01:38:31,200
what you do on these shoots.

1605
01:38:31,200 --> 01:38:33,720
- Let's stay friendly and see what
happens.
- OK.

1606
01:38:36,240 --> 01:38:39,760
- Julie and I have been offered an
unusual opportunity.

1607
01:38:39,760 --> 01:38:43,960
We've been invited to drop in on a
major five-year exploration

1608
01:38:43,960 --> 01:38:47,720
of a unique aspect of the evolution of
the human brain.

1609
01:38:48,720 --> 01:38:51,480
Researchers from Nottingham Trent
University

1610
01:38:51,480 --> 01:38:53,960
have taken over an entire house.

1611
01:38:57,800 --> 01:39:00,120
Cameras have been placed everywhere.

1612
01:39:01,520 --> 01:39:06,480
And, while we're here, every move will
be filmed from different angles

1613
01:39:06,480 --> 01:39:09,480
and the footage will be analysed by
researchers

1614
01:39:09,480 --> 01:39:11,680
hidden away in a different room.

1615
01:39:11,680 --> 01:39:13,720
- Are you ready to play a game
together?
- Yeah.

1616
01:39:13,720 --> 01:39:17,720
- For months now, psychological and
behavioural tests

1617
01:39:17,720 --> 01:39:23,120
have been carried out here, with 120
pairs of best friends or couples.

1618
01:39:23,120 --> 01:39:26,280
- The game that you're going to play
is called Lost on the Moon.

1619
01:39:26,280 --> 01:39:28,880
- Lost on the Moon is a puzzle game.

1620
01:39:28,880 --> 01:39:31,040
- Do we need this?
- Well...

1621
01:39:31,040 --> 01:39:34,480
We've been asked to put these items in
order of importance

1622
01:39:34,480 --> 01:39:36,320
to help us survive on the Moon.

1623
01:39:36,320 --> 01:39:38,360
- Why would we need a box of matches?

1624
01:39:38,360 --> 01:39:40,800
- There's no atmosphere on the Moon,
so you can't...

1625
01:39:40,800 --> 01:39:42,480
- You can't...
- Light a fire.

1626
01:39:42,480 --> 01:39:44,040
I'm going to be hungry.

1627
01:39:44,040 --> 01:39:46,720
I'm saying I'm going to feel peckish
and thirsty.

1628
01:39:46,720 --> 01:39:48,840
- Yeah, but it's not just about you,
Jim.

1629
01:39:48,840 --> 01:39:51,320
- Well, you'll probably want a snack.

1630
01:39:51,320 --> 01:39:54,400
Yeah...
- What have you got?
- I've got the pistols.
- Pistols!

1631
01:39:54,400 --> 01:39:57,640
- What are we going to shoot?
- You.
- LAUGHTER

1632
01:39:57,640 --> 01:40:00,560
Apparently we're going to need the
pistol because if we run out

1633
01:40:00,560 --> 01:40:03,880
of food, Julie's going to get hungry
and she's going to want to shoot me.

1634
01:40:03,880 --> 01:40:06,720
- I'm not going to want to shoot you
because I might get hungry.

1635
01:40:06,720 --> 01:40:09,520
- Just because I'm getting on your
nerves.
- Yeah.
- Fine.

1636
01:40:09,520 --> 01:40:12,240
As far as we're concerned, this is all
about, you know,

1637
01:40:12,240 --> 01:40:15,680
whether we can survive on the Moon
until we're rescued,

1638
01:40:15,680 --> 01:40:19,120
but it's clearly about, actually,
whether we're cooperating.

1639
01:40:19,120 --> 01:40:22,480
- We're quite good at that.
- It might not seem like it all the
time,

1640
01:40:22,480 --> 01:40:25,840
but we actually do manage to
compromise and cooperate.

1641
01:40:25,840 --> 01:40:28,240
- What do you mean, doesn't seem like
that?

1642
01:40:28,240 --> 01:40:30,280
Sorry, dear.
- JULIE LAUGHS

1643
01:40:30,280 --> 01:40:32,520
While all this is happening,

1644
01:40:32,520 --> 01:40:35,240
our facial expressions are being
recorded

1645
01:40:35,240 --> 01:40:38,040
and a team of evolutionary
psychologists

1646
01:40:38,040 --> 01:40:40,240
are analysing our results.

1647
01:40:40,240 --> 01:40:43,160
Then they call us for a meeting.

1648
01:40:43,160 --> 01:40:46,720
- So we've been videoing you while
you've been doing all these tasks

1649
01:40:46,720 --> 01:40:49,720
and we've been measuring your facial
movement.

1650
01:40:49,720 --> 01:40:53,120
Whether you furrow your brow, whether
you raise your brow,

1651
01:40:53,120 --> 01:40:55,880
whether you smile, whether you wrinkle
your nose.

1652
01:40:55,880 --> 01:40:57,480
- Funny look, isn't it?

1653
01:40:57,480 --> 01:40:59,640
- Eyebrow raises.
- Eyebrow raises.

1654
01:40:59,640 --> 01:41:02,680
- So this gives a huge amount of very
detailed information,

1655
01:41:02,680 --> 01:41:05,040
behavioural information, that's
happening

1656
01:41:05,040 --> 01:41:06,720
during a normal conversation.

1657
01:41:06,720 --> 01:41:12,280
- Jim has a rate of approximately 127
muscle movements per minute.

1658
01:41:12,280 --> 01:41:14,040
- Woohoo! Is that good?

1659
01:41:14,040 --> 01:41:16,320
- That's very high.
- Quite high, yeah.

1660
01:41:16,320 --> 01:41:18,120
- The average is about 100.

1661
01:41:18,120 --> 01:41:21,920
- Julie had slightly less facial
movements than me,

1662
01:41:21,920 --> 01:41:25,480
but it might be because she tends to
play her cards close to her chest.

1663
01:41:25,480 --> 01:41:28,160
- I might just be one of those really
deadpan people.

1664
01:41:28,160 --> 01:41:31,080
The poker face.
- LAUGHTER

1665
01:41:31,080 --> 01:41:36,120
This project is investigating how much
we use our facial expressions

1666
01:41:36,120 --> 01:41:40,320
to bond with others, especially our
nearest and dearest,

1667
01:41:40,320 --> 01:41:43,720
and comparing it with other primates.

1668
01:41:43,720 --> 01:41:46,200
- Many primates have facial
expressions that are

1669
01:41:46,200 --> 01:41:49,120
similar to ours, but our faces are the
most expressive,

1670
01:41:49,120 --> 01:41:53,240
and we think this sort of complexity
is probably really important

1671
01:41:53,240 --> 01:41:55,000
to humans as a species

1672
01:41:55,000 --> 01:41:59,240
and how we manage these really...
- Mmm.
- ..complex, intense

1673
01:41:59,240 --> 01:42:01,720
social interactions we have with other
people.

1674
01:42:01,720 --> 01:42:04,160
- That's helped the evolution of our
brains,

1675
01:42:04,160 --> 01:42:07,240
the fact that we are able to
communicate with facial expressions?

1676
01:42:07,240 --> 01:42:10,120
- That's the basic idea behind the
Social Brain Theory -

1677
01:42:10,120 --> 01:42:13,240
that what is difficult is the social
stuff.

1678
01:42:13,240 --> 01:42:16,840
So, forming relationships,
understanding the signals of others,

1679
01:42:16,840 --> 01:42:20,240
understanding relationships between
other individuals,

1680
01:42:20,240 --> 01:42:22,240
maintaining your own relationships,

1681
01:42:22,240 --> 01:42:26,240
that's the stuff that's difficult to
do and that requires big brains.

1682
01:42:27,240 --> 01:42:31,720
- Proponents of the Social Brain
Theory believe there's a direct link

1683
01:42:31,720 --> 01:42:34,600
between the relative intelligence of
primates

1684
01:42:34,600 --> 01:42:37,960
and the social groups they can
sustain.

1685
01:42:37,960 --> 01:42:41,320
As our ancestors spread out across the
lands,

1686
01:42:41,320 --> 01:42:43,720
they formed bigger social groups.

1687
01:42:44,960 --> 01:42:47,720
This helped keep them safe from
predators,

1688
01:42:47,720 --> 01:42:50,320
but took more brain power.

1689
01:42:50,320 --> 01:42:54,440
- Living in groups has costs, but it
also has lots of advantages

1690
01:42:54,440 --> 01:42:57,680
in terms of access to mates, you can
monopolise resources,

1691
01:42:57,680 --> 01:43:00,240
and primates are very good at living
in groups.

1692
01:43:00,240 --> 01:43:03,480
I think it's important to think about
humans and what we're good at,

1693
01:43:03,480 --> 01:43:06,320
and what we're good at is intense
social interaction.

1694
01:43:07,320 --> 01:43:10,720
- For this programme, we decided to
conduct a little test

1695
01:43:10,720 --> 01:43:12,720
on the Social Brain Theory.

1696
01:43:13,960 --> 01:43:15,960
And what could be more appropriate

1697
01:43:15,960 --> 01:43:19,240
than a good old traditional British
pub quiz?

1698
01:43:20,560 --> 01:43:23,720
I've invited Professor Robin Dunbar to
take part.

1699
01:43:23,720 --> 01:43:26,800
What are we having?
- A whisky, Jim, I think.
- Whisky?

1700
01:43:26,800 --> 01:43:29,000
- JIM LAUGHS
- It's a long evening.

1701
01:43:29,000 --> 01:43:31,880
He's the person who came up with the
Social Brain Theory

1702
01:43:31,880 --> 01:43:34,120
after years studying primates.

1703
01:43:37,040 --> 01:43:39,240
I start with some easy questions.

1704
01:43:39,240 --> 01:43:42,640
The greatest science communicator of
all time

1705
01:43:42,640 --> 01:43:45,720
is widely acknowledged to be, A, Carl
Sagan,

1706
01:43:45,720 --> 01:43:49,680
B, Neil deGrasse Tyson, C, Brian Cox,

1707
01:43:49,680 --> 01:43:52,240
LAUGHTER
or, D, Jim Al-Khalili?

1708
01:43:53,240 --> 01:43:56,520
I set the questions, by the way.
LAUGHTER

1709
01:43:56,520 --> 01:43:59,720
According to the Social Brain Theory,

1710
01:43:59,720 --> 01:44:02,960
what is the number of meaningful
friendships

1711
01:44:02,960 --> 01:44:07,400
which the average human being is
capable of maintaining?

1712
01:44:12,240 --> 01:44:14,720
It's 150.

1713
01:44:15,720 --> 01:44:20,320
In fact, that's a very famous number -
the Dunbar Number.

1714
01:44:22,240 --> 01:44:24,560
CHEERING AND APPLAUSE

1715
01:44:25,560 --> 01:44:28,960
The Dunbar Number sets limits to the
number of friends

1716
01:44:28,960 --> 01:44:34,120
and family we're cognitively capable
of having proper relationships with.

1717
01:44:34,120 --> 01:44:36,080
- The Dunbar Number you have

1718
01:44:36,080 --> 01:44:40,000
reflects the cognitive demands of
managing relationships.

1719
01:44:41,600 --> 01:44:45,240
- In fact, it's a concentric circle of
numbers,

1720
01:44:45,240 --> 01:44:48,720
starting with your closest circle of
five people -

1721
01:44:48,720 --> 01:44:53,160
the people you think about most, and
feel most empathy for.

1722
01:44:53,160 --> 01:44:55,520
- The single best predictor...

1723
01:44:55,520 --> 01:44:59,720
..of your mental health and wellbeing,

1724
01:44:59,720 --> 01:45:01,640
your physical health and wellbeing,

1725
01:45:01,640 --> 01:45:05,080
even how long you're going to live
into the future from today,

1726
01:45:05,080 --> 01:45:08,640
it's simply the number and quality of
close friendships.

1727
01:45:08,640 --> 01:45:11,720
- An average of 50 people are good
friends

1728
01:45:11,720 --> 01:45:16,240
and 150 is the average limit for
meaningful friendships.

1729
01:45:16,240 --> 01:45:19,320
- Beyond the 150, there's a layer that
goes out to about 500,

1730
01:45:19,320 --> 01:45:20,800
of acquaintances.

1731
01:45:20,800 --> 01:45:23,240
You may spend quite a lot of time
chatting to them

1732
01:45:23,240 --> 01:45:25,720
but you're probably not going to
invite them home.

1733
01:45:25,720 --> 01:45:28,040
- Robin says many studies show this.

1734
01:45:28,040 --> 01:45:32,240
From the average size of a medieval
village - 150 -

1735
01:45:32,240 --> 01:45:35,160
to a huge study about the number of
people

1736
01:45:35,160 --> 01:45:37,960
we communicate with properly on social
media.

1737
01:45:39,240 --> 01:45:42,080
- The average is 149.

1738
01:45:43,080 --> 01:45:46,240
- I'm going to set our audience a
cognitive test,

1739
01:45:46,240 --> 01:45:50,480
which Robin believes helps prove the
Social Brain Theory.

1740
01:45:50,480 --> 01:45:52,960
See if you can solve it yourself.

1741
01:45:52,960 --> 01:45:58,720
Each card has a number on one side and
a colour on the other.

1742
01:45:58,720 --> 01:46:02,960
If a card has an even number on one
side,

1743
01:46:02,960 --> 01:46:06,480
then on the other side it has to be
blue.

1744
01:46:07,480 --> 01:46:12,640
Which card, or cards, do you have to
turn over

1745
01:46:12,640 --> 01:46:16,920
to find out if that statement is true
or not?

1746
01:46:17,920 --> 01:46:21,640
Now, if you find this difficult, don't
worry at all.

1747
01:46:21,640 --> 01:46:24,840
Up to 90% of people can't work it out.

1748
01:46:25,840 --> 01:46:27,480
I got it wrong.

1749
01:46:27,480 --> 01:46:28,920
THEY LAUGH

1750
01:46:28,920 --> 01:46:32,920
It's because it's deliberately phrased
in a complicated

1751
01:46:32,920 --> 01:46:34,920
and abstract way.

1752
01:46:34,920 --> 01:46:36,640
Here's the answer.

1753
01:46:36,640 --> 01:46:38,880
To find out if that statement is true,

1754
01:46:38,880 --> 01:46:41,720
you'd have to turn over two cards.

1755
01:46:41,720 --> 01:46:44,960
They are the number eight card

1756
01:46:44,960 --> 01:46:46,960
and the red card.

1757
01:46:46,960 --> 01:46:50,960
How many people got that right? Can I
have a show of hands?

1758
01:46:50,960 --> 01:46:54,040
Our audience tonight did pretty well,

1759
01:46:54,040 --> 01:46:56,680
but the majority didn't get it.

1760
01:46:57,680 --> 01:47:00,040
Now a second test.

1761
01:47:00,040 --> 01:47:04,920
Jane's going to put up on one side the
age of the person,

1762
01:47:04,920 --> 01:47:07,560
and on the other side what they're
drinking.

1763
01:47:08,560 --> 01:47:10,240
Beer...

1764
01:47:10,240 --> 01:47:12,000
..and lemonade.

1765
01:47:14,000 --> 01:47:18,240
Which card, or cards, do you have to
turn over

1766
01:47:18,240 --> 01:47:22,920
to see if there are any underage
drinkers in your pub?

1767
01:47:22,920 --> 01:47:26,480
This one just feels so much easier.

1768
01:47:26,480 --> 01:47:29,880
To check if anyone is an underage
drinker,

1769
01:47:29,880 --> 01:47:32,480
you just need to check the 16-year-old

1770
01:47:32,480 --> 01:47:34,480
to see what they're drinking

1771
01:47:34,480 --> 01:47:37,960
and the beer drinker to see how old
they are.

1772
01:47:37,960 --> 01:47:40,240
How many people got that right?

1773
01:47:40,240 --> 01:47:42,240
Oh, there you go!

1774
01:47:42,240 --> 01:47:44,880
Just about everyone.

1775
01:47:44,880 --> 01:47:49,240
How many people found the first test
easier than the second test?

1776
01:47:53,240 --> 01:47:54,720
No-one.

1777
01:47:54,720 --> 01:47:57,040
And that's the real point,

1778
01:47:57,040 --> 01:48:02,960
because, amazingly, these two tests
are actually the same test of logic.

1779
01:48:02,960 --> 01:48:05,880
The beer is equivalent to the red

1780
01:48:05,880 --> 01:48:08,720
and the underage card, the 16,

1781
01:48:08,720 --> 01:48:11,920
is equivalent to the even card, the
number eight.

1782
01:48:11,920 --> 01:48:17,320
But we humans nearly always find one
much harder than the other.

1783
01:48:17,320 --> 01:48:21,240
Somehow, phrasing it in that way, in
terms of social activities

1784
01:48:21,240 --> 01:48:23,760
that we're familiar with in everyday
life,

1785
01:48:23,760 --> 01:48:27,480
makes that logic test seem so much
easier,

1786
01:48:27,480 --> 01:48:30,240
and yet it's exactly the same.

1787
01:48:30,240 --> 01:48:34,240
- The argument is that's because the
brain is attuned

1788
01:48:34,240 --> 01:48:38,720
to constantly checking for people who
infringe on social rules.

1789
01:48:40,480 --> 01:48:44,880
- So we didn't evolve as abstract,
logical calculators.

1790
01:48:44,880 --> 01:48:49,240
We evolved to work out each other and
to solve social problems

1791
01:48:49,240 --> 01:48:53,960
and police social rules such as
spotting underage drinkers.

1792
01:48:57,720 --> 01:49:00,720
A rapidly-developing field of
neuroscience

1793
01:49:00,720 --> 01:49:04,960
is now making some intriguing
breakthroughs, revealing where

1794
01:49:04,960 --> 01:49:09,120
in our brains much of our social
processing takes place.

1795
01:49:11,480 --> 01:49:16,240
Professor Nancy Kanwisher runs a
laboratory at MIT in Massachusetts.

1796
01:49:16,240 --> 01:49:18,960
- This is a slice through the middle
of the brain, here.

1797
01:49:18,960 --> 01:49:21,040
So, you see, this is the front of the
head,

1798
01:49:21,040 --> 01:49:23,040
that's the nose, that's the back.

1799
01:49:23,040 --> 01:49:28,240
- She made a name for herself when she
tried to detect brain activity

1800
01:49:28,240 --> 01:49:30,480
when we look at each other.

1801
01:49:30,480 --> 01:49:34,000
- Faces are one of the most important
kinds of visual stimuli.

1802
01:49:34,000 --> 01:49:36,920
They are the first stimulus that an
infant wants to look at.

1803
01:49:36,920 --> 01:49:39,880
And for social primates like us, it's
absolutely critical

1804
01:49:39,880 --> 01:49:42,960
to be able to perceive faces and all
the rich information

1805
01:49:42,960 --> 01:49:44,960
they tell us about another person.

1806
01:49:44,960 --> 01:49:47,640
We popped people in the scanner - me,
to start
- -

1807
01:49:47,640 --> 01:49:50,920
- and I looked at pictures of faces
and pictures of objects.

1808
01:49:50,920 --> 01:49:54,320
And so the first time we did this, I
remember coming out of the scanner

1809
01:49:54,320 --> 01:49:56,880
and finding this little blob in my
brain,

1810
01:49:56,880 --> 01:49:59,720
and you could just see in the time
course of response

1811
01:49:59,720 --> 01:50:03,240
in the experiment, a big peak during
the times I was looking at faces,

1812
01:50:03,240 --> 01:50:06,240
and these little teeny bumps when I
was looking at objects.

1813
01:50:06,240 --> 01:50:08,880
And I just thought, "That's amazing."

1814
01:50:10,480 --> 01:50:14,720
- What Nancy had found is called the
fusiform face area -

1815
01:50:14,720 --> 01:50:17,720
a highly specialised location in the
brain.

1816
01:50:18,720 --> 01:50:21,600
- So the fusiform face area seems to
be involved

1817
01:50:21,600 --> 01:50:23,240
both in detecting a face -

1818
01:50:23,240 --> 01:50:25,720
like, "That thing I'm looking at,
that's a face" -

1819
01:50:25,720 --> 01:50:27,800
and in figuring out which face that is
-

1820
01:50:27,800 --> 01:50:29,680
"Is that Joe or Bob or Mary or Jay?"

1821
01:50:30,960 --> 01:50:36,720
- This is the scan of my own brain and
this is my fusiform face area,

1822
01:50:36,720 --> 01:50:40,240
activated when I looked at videos of
faces.

1823
01:50:43,480 --> 01:50:45,960
Nancy and her colleagues have
discovered

1824
01:50:45,960 --> 01:50:48,960
other specialised social areas of the
brain.

1825
01:50:51,240 --> 01:50:53,720
This network has recently been
discovered.

1826
01:50:53,720 --> 01:50:57,240
It's called the dynamic social
pathway.

1827
01:50:57,240 --> 01:51:02,120
It helps us analyse and identify
moving people and faces,

1828
01:51:02,120 --> 01:51:05,800
expressions, other people's intentions
and moods.

1829
01:51:08,280 --> 01:51:12,480
This area is activated when we look at
people's bodies.

1830
01:51:12,480 --> 01:51:17,240
We even have a spot of our brain
called the theory of mind area,

1831
01:51:17,240 --> 01:51:21,240
activated when we think about what
other people are thinking.

1832
01:51:22,240 --> 01:51:24,560
- You can think of all of this
apparatus

1833
01:51:24,560 --> 01:51:26,720
as part of our social mind.

1834
01:51:26,720 --> 01:51:28,960
This is how we function in society.

1835
01:51:28,960 --> 01:51:32,560
It's a very temping hypothesis to say,
"Look, it makes total sense

1836
01:51:32,560 --> 01:51:35,240
"for evolution to have built this
structure in us."

1837
01:51:35,240 --> 01:51:37,960
We are social primates, we care about
each other,

1838
01:51:37,960 --> 01:51:41,200
we need to detect and recognise each
other to survive,

1839
01:51:41,200 --> 01:51:44,240
and so it would make sense for
evolution to have crafted

1840
01:51:44,240 --> 01:51:46,640
a specialised face-processing machine

1841
01:51:46,640 --> 01:51:48,440
and built it into a brain.

1842
01:51:48,440 --> 01:51:50,320
But we have to be careful.

1843
01:51:51,320 --> 01:51:54,640
- This is still a fast-developing
field of science.

1844
01:51:54,640 --> 01:51:58,320
These social networks could have
developed in our infancy

1845
01:51:58,320 --> 01:52:00,560
as we became exposed to faces.

1846
01:52:00,560 --> 01:52:04,880
Or they may be part of our
evolutionary inheritance.

1847
01:52:05,880 --> 01:52:09,720
What's known for sure is that our
ability to bond together

1848
01:52:09,720 --> 01:52:12,560
as social creatures starts very early.

1849
01:52:12,560 --> 01:52:14,880
- I'm convinced he's already saying,
"Mama".

1850
01:52:16,480 --> 01:52:20,400
- Dr Georgina Donati collaborates with
Gillian Forrester

1851
01:52:20,400 --> 01:52:23,880
in studying brain evolution and
development.

1852
01:52:23,880 --> 01:52:27,720
Recently, she's brought into the world
her own test subject -

1853
01:52:27,720 --> 01:52:30,240
four month-old Elio.

1854
01:52:30,240 --> 01:52:33,440
- Raspberry is a new skill, isn't it?

1855
01:52:34,440 --> 01:52:35,760
Ah.

1856
01:52:35,760 --> 01:52:39,760
- Elio's social brain is already
starting to kick in.

1857
01:52:40,760 --> 01:52:43,720
- He's become very vocal recently.
He's talking a lot,

1858
01:52:43,720 --> 01:52:46,760
although when other people are
talking, he likes to listen.

1859
01:52:46,760 --> 01:52:49,720
But, I mean, there are all of these
incredible mechanisms

1860
01:52:49,720 --> 01:52:51,400
that we've developed.

1861
01:52:51,400 --> 01:52:54,800
You know, they come out screaming
their heads off, which makes us all

1862
01:52:54,800 --> 01:52:59,240
kind of run to them immediately, and
then they develop smiles and giggles

1863
01:52:59,240 --> 01:53:02,520
and these things which keep us there
and keep us interacting with them.

1864
01:53:02,520 --> 01:53:05,480
It creates this interaction, which the
babies need to learn.

1865
01:53:05,480 --> 01:53:08,040
- And humans have evolved that?
- This is something that

1866
01:53:08,040 --> 01:53:10,720
I think we're continuing to find out
and explore.

1867
01:53:10,720 --> 01:53:14,560
- How does this compare, humans
babies, with other primates,

1868
01:53:14,560 --> 01:53:16,720
for example, or indeed other animals?

1869
01:53:16,720 --> 01:53:19,480
- One of the special characteristics
of us humans

1870
01:53:19,480 --> 01:53:23,880
is that we're born relatively early
and underdeveloped

1871
01:53:23,880 --> 01:53:26,120
in comparison to other great apes.

1872
01:53:26,120 --> 01:53:29,800
Gorillas, when they're born, they can
grip onto their mums better.

1873
01:53:29,800 --> 01:53:33,240
They're not independent yet, but
they're not quite as vulnerable

1874
01:53:33,240 --> 01:53:34,960
as our human babies.

1875
01:53:34,960 --> 01:53:39,640
We've got a longer developmental
period and it's made us able

1876
01:53:39,640 --> 01:53:43,320
to learn things more socially from a
very young age.

1877
01:53:43,320 --> 01:53:45,280
Who's this?

1878
01:53:47,520 --> 01:53:49,040
- JIM LAUGHS

1879
01:53:49,040 --> 01:53:52,480
- Who's that?
- Of all the toys that he's been
introduced to,

1880
01:53:52,480 --> 01:53:56,440
this gorilla is definitely the one
that makes him happiest.

1881
01:53:56,440 --> 01:53:58,480
- CONTENTED MOANS

1882
01:53:59,720 --> 01:54:03,960
A long childhood gives us what's known
as high plasticity -

1883
01:54:03,960 --> 01:54:08,560
our brains can adapt according to the
different environments we're in.

1884
01:54:11,240 --> 01:54:14,400
But it means our ancestors had to look
after

1885
01:54:14,400 --> 01:54:17,480
a helpless infant for years in the
wild.

1886
01:54:17,480 --> 01:54:19,560
It poses a huge question.

1887
01:54:20,560 --> 01:54:22,480
How did we survive?

1888
01:54:22,480 --> 01:54:25,320
- Well... So, as you'll know, being a
parent,

1889
01:54:25,320 --> 01:54:28,120
it's a massive parental investment.

1890
01:54:28,120 --> 01:54:31,040
With modern humans, we've often got
two parents,

1891
01:54:31,040 --> 01:54:35,520
and we also have extended families
that help raise these babies,

1892
01:54:35,520 --> 01:54:39,240
not just to be fed, but to be socially
engaged

1893
01:54:39,240 --> 01:54:43,480
and to keep giving the stimulus and
the stimulation to the brain.

1894
01:54:43,480 --> 01:54:46,240
- Our brains carry on developing
through adolescence

1895
01:54:46,240 --> 01:54:48,480
and we think now that this is carrying
on

1896
01:54:48,480 --> 01:54:50,480
until we're sort of in our mid-20s.

1897
01:54:50,480 --> 01:54:53,480
Potentially, providing these very
nurturing environments

1898
01:54:53,480 --> 01:54:56,480
really just allows this plasticity,
this learning,

1899
01:54:56,480 --> 01:54:59,800
this flexibility, to continue for
longer and longer.

1900
01:55:01,480 --> 01:55:06,240
- So the lesson is, without loving,
self-sacrificing parents

1901
01:55:06,240 --> 01:55:08,560
and supportive social communities,

1902
01:55:08,560 --> 01:55:11,720
we'd never have survived the rigours
of the wild

1903
01:55:11,720 --> 01:55:14,480
and evolved the brains we have today.

1904
01:55:17,240 --> 01:55:20,960
The human brain has now started to
build machines

1905
01:55:20,960 --> 01:55:24,600
which can surpass it in so many ways.

1906
01:55:24,600 --> 01:55:28,720
We humans have used our cognitive
powers to astonishing effect,

1907
01:55:28,720 --> 01:55:32,880
from those very early stone tools to
devices like this.

1908
01:55:32,880 --> 01:55:36,240
A smartphone is basically a
pocket-sized super computer,

1909
01:55:36,240 --> 01:55:39,480
capable of processing vast amounts of
information,

1910
01:55:39,480 --> 01:55:42,040
carrying out operations much more
quickly

1911
01:55:42,040 --> 01:55:43,960
than our brains could ever do.

1912
01:55:43,960 --> 01:55:47,720
And today we're on the brink of a new
technological revolution.

1913
01:55:47,720 --> 01:55:52,480
Artificial intelligence is already
performing complex mental tasks,

1914
01:55:52,480 --> 01:55:55,680
from essay writing to composing music.

1915
01:55:59,240 --> 01:56:03,120
The future of AI - our most
extraordinary creation -

1916
01:56:03,120 --> 01:56:06,480
is still unknown, but what I've learnt
on my journey

1917
01:56:06,480 --> 01:56:11,040
has given me hope that being in a
community with others

1918
01:56:11,040 --> 01:56:15,840
was the crucial final step in the
evolution of our brains.

1919
01:56:17,960 --> 01:56:20,880
What has fundamentally shaped our
brains

1920
01:56:20,880 --> 01:56:23,240
is our relationships with each other.

1921
01:56:23,240 --> 01:56:26,240
It's the family and friendship groups
we form,

1922
01:56:26,240 --> 01:56:29,240
it's our shared histories, our shared
cultures,

1923
01:56:29,240 --> 01:56:31,720
our beliefs, our memories.

1924
01:56:31,720 --> 01:56:36,240
Ultimately, it's our capacity for
empathy,

1925
01:56:36,240 --> 01:56:39,120
for love, for self-sacrifice,

1926
01:56:39,120 --> 01:56:43,240
for thinking about each other, that
has made us who we are.

1927
01:56:45,360 --> 01:56:51,240
Curious about how MRI technology can
reveal the secrets of your brain?

1928
01:56:51,240 --> 01:56:54,240
To watch the Open University's new
animation

1929
01:56:54,240 --> 01:56:58,000
exploring how an MRI works and what it
reveals,

1930
01:56:58,000 --> 01:57:05,080
scan the QR code or go to
bbc.co.uk/secretsofthebrain

1931
01:57:05,080 --> 01:57:08,200
and follow the links to the Open University.