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In here I have some of your cousins.

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They are tiny, bioluminescent
single-celled organisms.

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And when I shake them, they glow.

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They spend their time
floating around and glowing.

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You spend your time going to school
and seeing your friends.

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And yet we are related.

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We're both part of the great
Tree of Life on this planet.

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But where do we fit
into this Tree of Life?

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Welcome to the Royal Institution
Christmas Lectures.

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I'm Professor Alice Roberts
and over the course of these three

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lectures, we are going to find
out who we really are.

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And we're going to do
that by comparing ourselves

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with each other, with
earlier types of humans,

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and even with other
animals as well.

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And we will be looking
for similarities and differences

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between us until we can really point
out what is unique about us

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as a species and what is unique
about each one of us as individuals.

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So, we can trace back our
evolutionary line until we get

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to a common ancestor
of everything alive today.

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And that common ancestor
was a single cell,

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a single-celled organism
perhaps in a deep sea vent,

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the bottom of the oceans,
or maybe in a warm, shallow pond.

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And that ancestor lived
four billion years ago.

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Now, that's a huge number
to think about,

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a massive number to try to conceive,
so we've got a bit of help.

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We are going to illustrate
just how big that is.

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This is my friend Fran,
and this is a ribbon

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which represents four billion years
of life on Earth.

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And our time on the planet
is represented

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by just that tiny little
black strip at the end there.

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So, that tiny black strip is
actually 300,000 years of modern
humans,

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Homo sapiens, our species
being alive on Earth.

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And then as we go back in time,

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we're going back through
mammal ancestors.

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And back and back and back.
It's going to take far too long.

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Fran, we need some more power,
we need some help here.

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Here is Mike with a leaf blower.
Yes!

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Back through mammal ancestors,
those are reptiles.

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Multicellular.

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The yellow's all
single celled animals.

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And you're helping us
go back in time,

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ribbons of time are
descending on you.

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All single cells are still going.

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It's such a huge amount of time.

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And there we go, right back
to the beginning

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and the end of the ribbon there.

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Give us back our time,
you're stealing our time.

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So that's four billion years
of life on Earth,

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but somewhere in amongst
all of that is our story,

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our thread.

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How do we find it?

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How do we go about tracking
back our own story through time?

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We use the science of life.

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We use biology.

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So we can start to look
for similarities and differences

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between different living animals.

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And the first living animal I want
to introduce you to this evening -

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and this is the first time we've had
a horse in the Royal Institution -

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is Leo. Leo is a beautiful horse.

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He's come in with Caroline
and Charles from Windsor.

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And Leo is going to show us
just how similar we are to horses.

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Now, I'm an anatomist,
so I am interested in him

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on the outside. He's beautiful.

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He has a beautiful mane,
beautiful coat, beautiful tail.

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If we turn him round, though,
Caroline,

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we can reveal some of Leo's insides.

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And now you can see
the horse skeleton painted

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on the outside of him.

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Now, he looks so different
from us, doesn't he?

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He's a very, very different
sort of animal.

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He's a mammal, so he must have some
things in common with us.

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And we can get at some
of those similarities by looking

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at anatomy like this.

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So, we are going to need
a human to compare him with.

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Here's someone we prepared earlier.

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This is Adam,
our living human skeleton.

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Adam, can I position you over here?

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Thank you very much.

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So, Adam has his skeleton
painted on his outside as well.

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And what I want to try to do
now is to find some

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of these similarities
between humans and horses,

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so can I have a volunteer
from the audience?

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Yes, do you want to come
down and have a go?

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What's your name?

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So, if you stand over here.

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Boyan.
B-O-Y-A-N.

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Boyan.
Yes.

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What I want you to do...

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Leo's just having a little look at
you. He's a very friendly horse.

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Do you want to turn
around and say hello to him,

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so that you've met
each other properly?

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So, what I want you to do
is to look at the bones

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in the horse's leg and then
to look at Adam and see

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if you can find the same ones.

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So, if I just stand you back here.
Is that all right?

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And, Adam, if we just move
you a little bit this way.

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That's brilliant. Now, I'm just
going to spin Adam round,

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if that's all right, Adam.

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The first bone I want you to find,
Boyan, is this one here,

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which is a scapula,
or shoulder blade.

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Can you find the shoulder
blade in the horse?

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Where do you think
that's going to be?

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It's still going
to be quite triangular.

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A bit higher, a bit higher...
What about this one here?

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Well, it is much bigger, so...
It is much bigger.

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He is much bigger, though, isn't he?

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So that's the scapula on the horse,
and it is equivalent

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to the scapula in the human.

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And it's what attaches
the horse's front leg

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onto its body, onto its chest.

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And it's doing exactly
the same thing in Adam,

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it's attaching
the upper limb, the arm.

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Adam, if I spin
you back around again.

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Now we can start
to go down the limb.

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So, you found the scapula.
Can you find the equivalent

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of this bone, the humerus,
in the horse?

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Well done. And then can you find the
equivalent of these two bones?

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This is the radius
and the ulna in the human.

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Can you find something which might
be equivalent to those?

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Here.
A little bit higher, look.

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Can you see the horse's elbow?
The equivalent there? Yes. Yeah.

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And then we've got a collection
of bones in the wrist here.

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Adam, can you hold your hand out
like that so we can see?

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So, in your wrist, you have got
this little collection

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of bones called carpal bones.

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Can you see a little cluster
of bones which might be equivalent

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to those bones there?
Can you see there?

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Yeah. So, that's its wrist.

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That's the equivalent
to the horse's wrist.

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Then you've got a long bone
which is this bone in the palm here.

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But you can see it down
there on the horse.

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And then you should have three
bones,

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because fingers have each
got three bones.

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If you look at your own fingers, you
will see you have got three bones

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in your fingers and you see one,
two, three bones there.

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Can you see three bones getting down
towards Leo's foot?

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Oh, yes, I can see one, two, three.

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Brilliant. So, we have got
the same pattern of bones -

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one, two, many -
in the human and the horse.

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You were great. Thank you very much,
Boyan. Thank you. Thank you.

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APPLAUSE

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Now, I'm going to keep Adam and Leo
here a little while longer

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while we introduce you
to some other guests,

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and we're going to carry on
looking for these similarities.

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So, this is Brutus.
Andy, if I stick you there.

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Yeah.
Isn't he wonderful?

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What is he?
Armadillo.

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He's an armadillo.
What type of armadillo is he?

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He is a large hairy armadillo.

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And he is large and hairy.
Armadillos are mammals as well.

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They're wonderful creatures.
Is he all right? Yeah, he's fine.

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He's got bony plates on his skull
and over his back here which helps

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protect him from predators, and also
he can crawl inside thorn bushes

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to run away from predators
and not get scratched.

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And he has got some other
amazing adaptations,

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including these fantastic paws
which are for digging.

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So, he's a digging mammal, he lives
in a burrow,

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he digs out grubs and ants
and termites to eat.

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There we go, we can see
his lovely paws there.

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And we can bring in a skeleton
of an armadillo

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to have a look
in a bit more detail.

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Now, in this skeleton
of an armadillo, you can see

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that we've got the same bones.

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We have quite a scapula,
or shoulder blade, up here.

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Then there is a humerus.

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Then there is a radius and an
ulna again, just like in Adam.

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Then there are carpal bones.

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Then there are these very chunky,
robust fingers

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which are absolutely great
for digging,

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for pushing
all of that soil out of the way.

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Is he OK to stay with us
for a minute, Andy?

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Yeah, yeah.
Thank you.

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I want to introduce you
to another guest now.

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This is a tiny little bat.

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This is Merlin the serotine,

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one of the largest bats in Britain.

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Could you show him to the
front row over there, perhaps?

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So, a tiny little bat there.

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So, again, this is a mammal,
so we will find some similarities,

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even though it's such
a different sort of animal.

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Can I bring you back over here and
we'll just have a look at his wings?

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Now, is he all right to show us
his wings? He's quite nervous.

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Is he waking up?
You might be able to stretch

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his wing out and have a look.
Might be able to open it.

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So, we can see his wing there
and you can see the way

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that his wing is made of skin
stretched over a bony framework.

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I think we can let him
put his wing away.

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Yes. And we can look at a bat's
skeleton alongside him.

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And when we bring out
the bat's skeleton,

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we start to see here
another similarity,

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another pattern of similarity
with all of these other animals

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that we've looked at.
So, looking at this bat skeleton,

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you've got a tiny little scapula,
a tiny little shoulder blade,

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attaching the wing to the thorax,
to the chest.

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Then a humerus.

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Then you have got those
forearm bones and wrist bones,

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just like in the human.

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And then the bones that actually
form the structure of the wing

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are the bat's fingers.

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So, again, they've got one, two,
three bones in each of those struts

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that are supporting the wing.

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So, we are finding some amazing
similarities between animals

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that look very,
very different on the surface.

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Now, before you do this,
I just want to say,

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please can you do it very quietly?

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00:10:34,720 --> 00:10:37,960
We're going to give a very gentle
round of applause to all of our

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00:10:37,960 --> 00:10:40,160
animal menagerie and their owners.

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Thank you. Thank you.

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00:10:47,520 --> 00:10:51,080
So, how amazing to find
all those hidden similarities

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00:10:51,080 --> 00:10:55,120
between the horse and the human
and the armadillo and the bat.

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00:10:55,120 --> 00:10:57,840
What's even more astounding
is that once you start looking

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00:10:57,840 --> 00:11:01,120
for these similarities,
you find them absolutely everywhere,

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00:11:01,120 --> 00:11:05,360
from the anatomy that we can see
with our eyes, like the skeleton,

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00:11:05,360 --> 00:11:09,440
right down to the level
of molecules inside our cells.

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00:11:09,440 --> 00:11:14,440
So, to take us down to that
level now, and to look at DNA

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00:11:14,840 --> 00:11:18,240
in ourselves, I want to introduce
you to somebody very special

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00:11:18,240 --> 00:11:21,520
from Trinity College, Dublin,
and The Genetics Society,

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00:11:21,520 --> 00:11:23,560
Professor Aoife McLysaght.

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00:11:26,920 --> 00:11:28,160
Thank you.

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00:11:28,160 --> 00:11:32,560
So, in order to do what Alice
says and to really get

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00:11:32,560 --> 00:11:36,200
down to a molecular level, the
first thing we have to do is imagine

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00:11:36,200 --> 00:11:38,560
this theatre as a cell.

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00:11:38,560 --> 00:11:40,080
Imagine we're inside a cell.

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00:11:40,080 --> 00:11:42,960
So, if we get some balloons
and just gently bounce them

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00:11:42,960 --> 00:11:45,960
around like they're
floating inside a cell.

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Yeah, so we can see
different things.

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00:11:47,560 --> 00:11:49,600
Like, we have mitochondria,

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00:11:49,600 --> 00:11:52,760
which are generating
the energy in the cell.

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00:11:52,760 --> 00:11:57,560
We have lysosomes, which are the
waste management plant in the cell.

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And lots of other bits and pieces.

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But, Alice, the thing that
I'm really interested in

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00:12:02,120 --> 00:12:03,440
is this big one here.

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00:12:03,440 --> 00:12:06,880
So, catch! No!
It's like a wrecking ball!

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00:12:06,880 --> 00:12:08,400
Yes.

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00:12:08,400 --> 00:12:09,880
So, this is the special one.

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00:12:09,880 --> 00:12:13,280
So, you've got lots of
other little balloons...

237
00:12:13,280 --> 00:12:16,080
Got lots of other little balloons,
but there's only one of these.

238
00:12:16,080 --> 00:12:20,000
This is the nucleus of the cell,
and this contains something

239
00:12:20,000 --> 00:12:23,040
very important and something
that I am especially interested

240
00:12:23,040 --> 00:12:25,640
in as a geneticist,
but we can't see it yet.

241
00:12:25,640 --> 00:12:28,440
And, Alice, I'd like you
to do the honours, please.

242
00:12:28,440 --> 00:12:31,720
So, Aoife has just handed me
a very, very sharp instrument.

243
00:12:31,720 --> 00:12:34,280
Yeah, I was carrying
that in my pocket until now,

244
00:12:34,280 --> 00:12:36,200
so that was a bit risky.
What's inside it?

245
00:12:36,200 --> 00:12:38,960
Well, we will see, let's see.
So, we will count from three.

246
00:12:38,960 --> 00:12:41,320
Three, two, one...

247
00:12:41,320 --> 00:12:42,880
Oh!

248
00:12:42,880 --> 00:12:47,680
So what we have here...is DNA.

249
00:12:47,680 --> 00:12:49,880
So, you've probably
heard of DNA before,

250
00:12:49,880 --> 00:12:54,120
and maybe you know that DNA is
really, really important for making

251
00:12:54,120 --> 00:12:56,840
you what you are. And look at this,
we have got two colours.

252
00:12:56,840 --> 00:12:58,960
We have got yellow and white.

253
00:12:58,960 --> 00:13:01,440
So, half of it is yellow,
half of it's white.

254
00:13:01,440 --> 00:13:05,040
So, this is half from your mum
and half from your dad.

255
00:13:05,040 --> 00:13:08,640
And if we were to...
We have 23 pairs of chromosomes.

256
00:13:08,640 --> 00:13:11,080
In the human genome, 23 pairs.

257
00:13:11,080 --> 00:13:14,520
And if we were to stretch
these out end to end,

258
00:13:14,520 --> 00:13:17,840
they would reach to two metres long,
which is basically this length

259
00:13:17,840 --> 00:13:19,640
I'm carrying here.

260
00:13:19,640 --> 00:13:21,640
But I don't mean two metres

261
00:13:21,640 --> 00:13:24,680
on the scale of this whole theatre
as a cell.

262
00:13:24,680 --> 00:13:26,920
I mean two metres in real life,

263
00:13:26,920 --> 00:13:29,640
two metres inside
the cells of your body.

264
00:13:29,640 --> 00:13:33,520
So, if we lined up all of the DNA
in our chromosomes,

265
00:13:33,520 --> 00:13:36,480
in a single cell,
it would be two metres long? Yes.

266
00:13:36,480 --> 00:13:38,440
But the thing is,
it's extremely thin,

267
00:13:38,440 --> 00:13:40,640
like, less than one of the threads
of this,

268
00:13:40,640 --> 00:13:43,200
and it's all scrunched up
really, really small.

269
00:13:43,200 --> 00:13:46,720
And it is packed into a tiny
space, just like that.

270
00:13:46,720 --> 00:13:48,920
So, DNA is really, really long.

271
00:13:48,920 --> 00:13:50,880
And so that is a lot of DNA.

272
00:13:50,880 --> 00:13:55,200
It is actually three billion letters
of the DNA that you have as a human.

273
00:13:55,200 --> 00:13:58,160
I presume you're all human, yeah?
I didn't check.

274
00:13:58,160 --> 00:13:59,840
But it's actually quite simple.

275
00:13:59,840 --> 00:14:03,400
It's only got four parts to it.
So, the four parts,

276
00:14:03,400 --> 00:14:06,720
we symbolise them with
the letters A, C, T and G.

277
00:14:06,720 --> 00:14:08,160
So, just four parts to DNA.

278
00:14:08,160 --> 00:14:12,400
And if you look at this bit here,
so we've made the letters big here,

279
00:14:12,400 --> 00:14:15,640
but you can see there's
a sequence of letters.

280
00:14:15,640 --> 00:14:20,720
We've got T-A-C-C-A-G-A-T-T-C-G.

281
00:14:20,960 --> 00:14:24,040
Right? You can read that
like I can read that?

282
00:14:24,040 --> 00:14:26,440
That's a DNA sequence.
That's all we mean when we talk

283
00:14:26,440 --> 00:14:28,680
about a DNA sequence.
It's a sequence of letters.

284
00:14:28,680 --> 00:14:31,960
And because you're all human,
you've got a human DNA sequence,

285
00:14:31,960 --> 00:14:34,960
and a horse has a horse DNA
sequence, and an armadillo

286
00:14:34,960 --> 00:14:36,720
has an armadillo DNA sequence.

287
00:14:36,720 --> 00:14:38,680
And we can actually compare them.

288
00:14:38,680 --> 00:14:40,200
And so look at this.

289
00:14:40,200 --> 00:14:42,960
This is a real piece
of DNA sequence.

290
00:14:42,960 --> 00:14:45,680
This is from the human genome,
so you all have this in you.

291
00:14:45,680 --> 00:14:49,800
This is actually
a little bit of a gene.

292
00:14:49,800 --> 00:14:53,880
And this gene is involved in the
development of your front limb.

293
00:14:53,880 --> 00:14:56,760
So, for you, that's an arm,
for the horse, it's a leg.

294
00:14:56,760 --> 00:14:59,440
And if we look at this little
bit in the sequence,

295
00:14:59,440 --> 00:15:01,320
we can read it across, it's easy.

296
00:15:01,320 --> 00:15:02,880
T-C-C-T-A-T-A-G-G, etc.

297
00:15:02,880 --> 00:15:04,520
Easy to read DNA sequences.

298
00:15:04,520 --> 00:15:07,880
And then you've got the armadillo,
the bat and the horse.

299
00:15:07,880 --> 00:15:10,200
And if you look at this,
you can see really quickly

300
00:15:10,200 --> 00:15:12,320
that the beginning is
the same in all of them,

301
00:15:12,320 --> 00:15:15,520
so they all have T-C-C-T-A,

302
00:15:15,520 --> 00:15:17,280
But then we've got
one difference here.

303
00:15:17,280 --> 00:15:19,920
So, this is something that happens
in humans but not in the others.

304
00:15:19,920 --> 00:15:22,920
We've got a T in human,
but we've got a C everywhere else.

305
00:15:22,920 --> 00:15:25,320
And if we look here,
we've got an A in horse

306
00:15:25,320 --> 00:15:26,760
and a G everywhere else.

307
00:15:26,760 --> 00:15:30,680
So, we all have similar genes,
a bit like Alice showed you,

308
00:15:30,680 --> 00:15:32,800
you have the same bones
in the different animals,

309
00:15:32,800 --> 00:15:34,680
but they're a slightly
different shape,

310
00:15:34,680 --> 00:15:36,720
but they're still
recognisably the same.

311
00:15:36,720 --> 00:15:38,720
So, they're slightly
different but the same,

312
00:15:38,720 --> 00:15:40,320
and we see that with the genes.

313
00:15:40,320 --> 00:15:43,840
I think it's just fascinating
that we've got these similarities

314
00:15:43,840 --> 00:15:46,880
when we look at anatomy,
when we look at skeletons,

315
00:15:46,880 --> 00:15:49,160
and it's there as well at the level
of the DNA sequences.

316
00:15:49,160 --> 00:15:51,720
At the DNA level, yeah.
That's brilliant. Thank you, Aoife.

317
00:15:51,720 --> 00:15:54,280
Yes. I'll see you later, Alice.
See you later.

318
00:15:54,280 --> 00:15:57,840
Now, biologists started
noticing these differences

319
00:15:57,840 --> 00:15:59,680
back in the 19th century.

320
00:15:59,680 --> 00:16:03,320
Not in DNA sequences, because
that science was yet to come,

321
00:16:03,320 --> 00:16:05,400
but they could look at skeletons.

322
00:16:05,400 --> 00:16:09,600
And there was one biologist
in particular who wrote about this,

323
00:16:09,600 --> 00:16:11,800
and his name was Richard Owen,

324
00:16:11,800 --> 00:16:14,320
and I've got a copy
of his book here.

325
00:16:14,320 --> 00:16:17,280
And this book is
nearly 170 years old.

326
00:16:17,280 --> 00:16:22,280
It was published in 1849, and it's
called On The Nature Of The Limbs.

327
00:16:22,840 --> 00:16:27,080
So, he looked at the bones
of a horse, and actually

328
00:16:27,080 --> 00:16:29,640
there's a really weird
similarity here when I compare

329
00:16:29,640 --> 00:16:33,520
that with the bones of a bat
and with the bones of...

330
00:16:33,520 --> 00:16:35,640
He used a mole.
We used an armadillo.

331
00:16:35,640 --> 00:16:39,680
And what Richard Owen said
was there's something deeply

332
00:16:39,680 --> 00:16:43,120
strange here, deeply weird,
because why do all these animals

333
00:16:43,120 --> 00:16:45,160
look the same under the skin?

334
00:16:45,160 --> 00:16:48,040
If their structure was
just about what they did,

335
00:16:48,040 --> 00:16:51,160
just about their function,
you wouldn't expect any underlying

336
00:16:51,160 --> 00:16:53,040
similarity between
something that flies

337
00:16:53,040 --> 00:16:55,320
and something that runs
fast and something that digs.

338
00:16:55,320 --> 00:16:57,000
So, there's something else going on.

339
00:16:57,000 --> 00:17:00,400
And it was a great puzzle to him
and he didn't crack it,

340
00:17:00,400 --> 00:17:01,840
he didn't work it out.

341
00:17:01,840 --> 00:17:05,960
He said, there's some kind
of abstract idea of mammalness,

342
00:17:05,960 --> 00:17:09,400
and all of these animals
are just variations on a theme.

343
00:17:09,400 --> 00:17:13,040
Ten years later,
Charles Darwin published his book,

344
00:17:13,040 --> 00:17:16,760
On The Origin Of Species,
and he nailed it.

345
00:17:16,760 --> 00:17:20,080
He said there is something
really important that links

346
00:17:20,080 --> 00:17:22,080
these animals together and explains

347
00:17:22,080 --> 00:17:24,200
all of these underlying
similarities.

348
00:17:24,200 --> 00:17:26,960
And it's not abstract at all.

349
00:17:26,960 --> 00:17:28,440
It's a real thing.

350
00:17:28,440 --> 00:17:32,720
And what it is is a shared ancestor.

351
00:17:32,720 --> 00:17:35,880
So, when you're looking
at the armadillo and the horse

352
00:17:35,880 --> 00:17:38,400
and the human and the bat,
the reason that they've got

353
00:17:38,400 --> 00:17:42,480
those similarities is that
if we trace their family trees back

354
00:17:42,480 --> 00:17:44,920
and back and back and back,
we get to a point where

355
00:17:44,920 --> 00:17:48,320
there's a shared ancestor,
an ancient mammal ancestor

356
00:17:48,320 --> 00:17:50,320
that had that pattern
of bones in its limb

357
00:17:50,320 --> 00:17:53,640
and all of these different
organisms, including us,

358
00:17:53,640 --> 00:17:55,520
have inherited that pattern from it.

359
00:17:55,520 --> 00:17:58,880
And we've got an idea
of what that mammal ancestor

360
00:17:58,880 --> 00:18:02,400
actually looked like,
and it is this.

361
00:18:02,400 --> 00:18:06,240
And she is called Juramaia,
which means Jurassic mother.

362
00:18:06,240 --> 00:18:10,440
She was around at the time
of the dinosaurs and she lived

363
00:18:10,440 --> 00:18:14,520
about 170 million years ago.

364
00:18:14,520 --> 00:18:18,480
So, we've inherited the pattern
of bones in our limbs

365
00:18:18,480 --> 00:18:21,280
from ancient ancestors like this.

366
00:18:21,280 --> 00:18:23,640
We've also, some of us,
inherited something else

367
00:18:23,640 --> 00:18:25,400
from ancient mammal ancestors.

368
00:18:25,400 --> 00:18:30,440
I wonder if anybody in the audience
can wiggle their ears?

369
00:18:30,440 --> 00:18:33,280
Something very important here
is that you have to make sure

370
00:18:33,280 --> 00:18:37,120
you're really wiggling your ears and
not just moving your whole scalp.

371
00:18:37,120 --> 00:18:39,600
You've got a muscle in the front
of your forehead here,

372
00:18:39,600 --> 00:18:42,320
called frontalis, and a muscle
at the back of your head,

373
00:18:42,320 --> 00:18:43,400
called occipitalis.

374
00:18:43,400 --> 00:18:48,240
And I can shift my whole scalp
backwards and forwards.

375
00:18:48,240 --> 00:18:50,880
It's a really important life skill.

376
00:18:50,880 --> 00:18:53,640
It's...taken me some
years to perfect.

377
00:18:53,640 --> 00:18:56,200
But what I can't do is wiggle my
ears independently of that.

378
00:18:56,200 --> 00:18:57,520
So I think there were some...

379
00:18:57,520 --> 00:18:59,320
Were there any ear wiggling
people here?

380
00:18:59,320 --> 00:19:01,840
So you think you can
wiggle your ears.

381
00:19:01,840 --> 00:19:04,280
What's your name?
Matt. Matt.

382
00:19:04,280 --> 00:19:07,760
Wiggle your ears.
I think he is...

383
00:19:07,760 --> 00:19:09,320
That's a pretty good ear wiggling.

384
00:19:09,320 --> 00:19:11,600
Well done.
Well done, Matt.

385
00:19:13,400 --> 00:19:17,960
So, Matt is able to voluntarily use
little muscles around the ear

386
00:19:17,960 --> 00:19:21,160
that all of us have, but only some
of us seem able to use them still.

387
00:19:21,160 --> 00:19:24,040
And this is left over from
ancient mammal ancestors

388
00:19:24,040 --> 00:19:26,080
who had much bigger ears than us.

389
00:19:26,080 --> 00:19:30,280
So, there are these interesting
remnants of ancient ancestors in us,

390
00:19:30,280 --> 00:19:33,360
and we can look at the fossil record
and we can find really ancient

391
00:19:33,360 --> 00:19:36,640
mammals like that Juramaia,
and we can date them,

392
00:19:36,640 --> 00:19:38,960
because we can date the rocks
that they're found in.

393
00:19:38,960 --> 00:19:42,200
But, actually, there's another,
completely different independent way

394
00:19:42,200 --> 00:19:46,400
of dating a common ancestor
of mammals,

395
00:19:46,400 --> 00:19:49,400
and that's by looking at genetics.

396
00:19:49,400 --> 00:19:50,840
Did you say genetics?

397
00:19:50,840 --> 00:19:52,880
I might have done.
That's my bit.

398
00:19:52,880 --> 00:19:55,520
So, yeah, it's true that we
can look at DNA sequences.

399
00:19:55,520 --> 00:19:58,720
As you just saw, we looked at some
DNA sequences and we saw

400
00:19:58,720 --> 00:20:00,440
a few differences, right?

401
00:20:00,440 --> 00:20:05,320
And we can look at this and we can
think about how those differences

402
00:20:05,320 --> 00:20:08,480
accumulate and think about it
with respect to time.

403
00:20:08,480 --> 00:20:12,240
And this is because every time
you have a new generation,

404
00:20:12,240 --> 00:20:16,120
the DNA has to get copied
to be passed on that new generation.

405
00:20:16,120 --> 00:20:19,400
And every time you copy DNA,
there's just a chance

406
00:20:19,400 --> 00:20:20,920
that there's mistake made.

407
00:20:20,920 --> 00:20:24,560
So, a mistake is a mutation,
when you're talking about DNA.

408
00:20:24,560 --> 00:20:28,440
And so sometimes those mutations
have some big effect and maybe

409
00:20:28,440 --> 00:20:30,520
there's something we can
see on the outside.

410
00:20:30,520 --> 00:20:33,440
And sometimes the mutations
really do nothing and so they're

411
00:20:33,440 --> 00:20:37,560
just gradually, over time,
getting more and more changes,

412
00:20:37,560 --> 00:20:39,840
which means that when we look at
the number of changes,

413
00:20:39,840 --> 00:20:41,840
we can actually figure
out the amount of time.

414
00:20:41,840 --> 00:20:45,040
But I am going to explain
this better with a little demo,

415
00:20:45,040 --> 00:20:47,240
and for this, I'm going
to need two volunteers.

416
00:20:47,240 --> 00:20:48,760
Wow, this is brilliant.

417
00:20:48,760 --> 00:20:51,560
OK, so, you there in
the lovely Christmas jumper.

418
00:20:51,560 --> 00:20:55,120
You come down. And, yes,
another Christmas jumper.

419
00:20:55,120 --> 00:20:57,720
Is that your little dachshund?
Lovely.

420
00:21:01,720 --> 00:21:03,320
OK, so, what is your name?
Dylan.

421
00:21:03,320 --> 00:21:04,560
Dylan.
And your name?

422
00:21:04,560 --> 00:21:06,400
OK. Can you go over there
with Alice?

423
00:21:06,400 --> 00:21:08,600
And Dylan, you just stand
there for a moment.

424
00:21:08,600 --> 00:21:11,400
So, what we have here
is we have two DNA sequences

425
00:21:11,400 --> 00:21:14,520
and everybody can see
at this point they're the same.

426
00:21:14,520 --> 00:21:17,160
So, they're lined up like they were
printed on the page earlier.

427
00:21:17,160 --> 00:21:18,360
So you can pair up and down.

428
00:21:18,360 --> 00:21:22,680
So we have got T-G-C-G-A-C-A...

429
00:21:22,680 --> 00:21:24,360
That's a DNA sequence.

430
00:21:24,360 --> 00:21:26,400
And these are actually identical

431
00:21:26,400 --> 00:21:29,360
because they have a very recent
common ancestor.

432
00:21:29,360 --> 00:21:32,400
So that's...they're sharing
ancestors very, very recently.

433
00:21:32,400 --> 00:21:35,880
What we're going to see what happens
when species get separated.

434
00:21:35,880 --> 00:21:39,160
So, I'm going to be this
species on the top,

435
00:21:39,160 --> 00:21:42,360
and, Alice, maybe you could take the
bottom one. Yeah. So, Alison and I

436
00:21:42,360 --> 00:21:44,360
at the moment
are identical to each other.

437
00:21:44,360 --> 00:21:46,920
But we get separated.
We have our reasons, I suppose,

438
00:21:46,920 --> 00:21:50,520
we've gone astray, but look,
there's this river in between us

439
00:21:50,520 --> 00:21:51,640
and we can't go back now.

440
00:21:51,640 --> 00:21:55,240
So, now we are separate
and our lineages can't mix any more.

441
00:21:55,240 --> 00:21:59,240
So, now, when we have generations
on this side in the Aoife lineage,

442
00:21:59,240 --> 00:22:02,000
those aren't going to get mixed,
those changes aren't going to get

443
00:22:02,000 --> 00:22:04,600
mixed up with what happens over
on Alice's side of the river.

444
00:22:04,600 --> 00:22:06,520
So, things are happening
independently

445
00:22:06,520 --> 00:22:08,160
on the two sides of the river.

446
00:22:08,160 --> 00:22:11,000
So, what we're going to get you
to do is we're going to imagine

447
00:22:11,000 --> 00:22:13,840
there is new generations happening
and there is mutations happening.

448
00:22:13,840 --> 00:22:16,920
So, what I am going to get you to do
is I'm going to ask you to flick

449
00:22:16,920 --> 00:22:18,280
one of these, but not just yet

450
00:22:18,280 --> 00:22:20,040
because we're going
to count together.

451
00:22:20,040 --> 00:22:21,960
And the same thing
for you over there.

452
00:22:21,960 --> 00:22:24,400
So, we're going to count
with the audience together

453
00:22:24,400 --> 00:22:27,040
and we're going to count down
from three each time and I want

454
00:22:27,040 --> 00:22:30,840
you to just randomly pick one
of them and flip it over. OK?

455
00:22:30,840 --> 00:22:34,560
So, we count together.
Three, two, one.

456
00:22:34,560 --> 00:22:37,360
Go. Flip it. Do one.
OK, brilliant.

457
00:22:37,360 --> 00:22:40,840
And again. Three, two, one.

458
00:22:40,840 --> 00:22:44,280
Choose another one.
Beautiful. And one more. Brilliant.

459
00:22:44,280 --> 00:22:47,160
Three, two, one.

460
00:22:48,840 --> 00:22:51,240
Lovely. Brilliant. We have got three
random mutations over here.

461
00:22:51,240 --> 00:22:53,880
Thank you so much. Thank you so
much. OK, so thank you so much.

462
00:22:53,880 --> 00:22:56,680
You can sit down again. Thank you
so much, both of you. Thank you.

463
00:22:57,960 --> 00:23:00,400
We'll put these back here now.

464
00:23:00,400 --> 00:23:02,440
Put these back here now
so we can compare them again

465
00:23:02,440 --> 00:23:04,080
and let's just see what happened.

466
00:23:04,080 --> 00:23:06,920
So, Alison and I have been
separated for three generations

467
00:23:06,920 --> 00:23:11,120
and our descendants now
are comparing their DNA.

468
00:23:11,120 --> 00:23:13,840
And so even though Alice
and I started out exactly the same,

469
00:23:13,840 --> 00:23:15,920
now our descendants
are slightly different.

470
00:23:15,920 --> 00:23:17,840
So, let's see if we can
find some changes.

471
00:23:17,840 --> 00:23:19,720
So, like, here we've
got a G and then a C.

472
00:23:19,720 --> 00:23:21,920
That is one change.
In another change.

473
00:23:21,920 --> 00:23:24,880
Two, three, four.

474
00:23:24,880 --> 00:23:26,440
I've got to line them up, Aoife.

475
00:23:26,440 --> 00:23:29,040
Yes, I know. You're helping me,
thank you so much. Five.

476
00:23:29,040 --> 00:23:30,440
Six differences.

477
00:23:30,440 --> 00:23:32,440
So, we had two sides of the river,

478
00:23:32,440 --> 00:23:35,560
so it's three differences
on each side of the river.

479
00:23:35,560 --> 00:23:39,760
And in our case, we know
that there was one change happening

480
00:23:39,760 --> 00:23:43,560
per generation, so we could say
even if we didn't know how much time

481
00:23:43,560 --> 00:23:47,080
had elapsed, we could count the
differences in the DNA sequences,

482
00:23:47,080 --> 00:23:50,120
and just from that on its own,
without having any other

483
00:23:50,120 --> 00:23:53,800
information, we could say
that these two species had a common

484
00:23:53,800 --> 00:23:56,680
ancestor three generations ago.

485
00:23:56,680 --> 00:23:59,960
So, this idea is called
a molecular clock.

486
00:23:59,960 --> 00:24:03,760
So, we can use the molecule,
look at the changes in the DNA

487
00:24:03,760 --> 00:24:07,720
molecule and use it to count
time, to measure time.

488
00:24:07,720 --> 00:24:09,920
So, you could do that
for two different animals...

489
00:24:09,920 --> 00:24:12,640
Like, a human and a bat, could you
do it for a human and a bat? Yes.

490
00:24:12,640 --> 00:24:15,080
So, we wouldn't do it for something
as small as this sequence.

491
00:24:15,080 --> 00:24:16,400
We'd do it for much, much more.

492
00:24:16,400 --> 00:24:18,640
So, for a human and a bat,
we can compare thousands

493
00:24:18,640 --> 00:24:22,200
and thousands and thousands
of genes, and when we do that,

494
00:24:22,200 --> 00:24:25,040
we can count up the differences
and estimate the time.

495
00:24:25,040 --> 00:24:28,680
And we say we get to 96 million
years ago, there was a common

496
00:24:28,680 --> 00:24:30,880
ancestor between humans and bats.

497
00:24:30,880 --> 00:24:32,800
That's quite a long time, isn't it?

498
00:24:32,800 --> 00:24:35,960
And what about for all placental
mammals, so mammals like us?

499
00:24:35,960 --> 00:24:40,320
Yes, so if we add in more species
and we look at deeper divergences,

500
00:24:40,320 --> 00:24:43,000
we get back to about
170 million years ago.

501
00:24:43,000 --> 00:24:46,720
So, this is amazing,
because that's a date based purely

502
00:24:46,720 --> 00:24:50,480
on the genetics of
living organisms... Yes.

503
00:24:50,480 --> 00:24:53,120
Working out how fast they
change over time and saying,

504
00:24:53,120 --> 00:24:55,880
"well, we must have had a common
ancestor with all those other

505
00:24:55,880 --> 00:25:00,160
"mammals going back 170 million
years ago" and then looking at the
fossil

506
00:25:00,160 --> 00:25:03,480
record, we find these really early
mammals 170 million years ago.

507
00:25:03,480 --> 00:25:06,200
So, we have got two completely
different branches of science

508
00:25:06,200 --> 00:25:08,520
agreeing with each other.
Totally in harmony.

509
00:25:08,520 --> 00:25:13,000
And it's time to put our
ancient mammal ancestor

510
00:25:13,000 --> 00:25:15,440
onto the Tree of Life.

511
00:25:15,440 --> 00:25:18,280
So, we have this beautiful tree,
Alice. Aw, this is our tree.

512
00:25:18,280 --> 00:25:21,600
This is how we reconstruct all of
those similarities and differences.

513
00:25:21,600 --> 00:25:23,280
It tells us how related we are

514
00:25:23,280 --> 00:25:25,720
to different organisms
on the planet today.

515
00:25:25,720 --> 00:25:28,240
And it's just like a family tree,
so, you know, you are connected

516
00:25:28,240 --> 00:25:31,360
to your siblings through your
parents and then to your cousins

517
00:25:31,360 --> 00:25:34,200
through your grandparents,
except we're doing it for species.

518
00:25:34,200 --> 00:25:36,720
So, we have, look,
we've got the human here

519
00:25:36,720 --> 00:25:40,120
and the animals we've just
been looking at, in fact...

520
00:25:40,120 --> 00:25:43,120
Yeah, the bat, the horse, the
armadillo. Yeah, yeah, yeah. So...

521
00:25:43,120 --> 00:25:45,080
So, a common ancestor
of all of those, then,

522
00:25:45,080 --> 00:25:48,120
going back 170 million years ago,
we've already met Juramaia,

523
00:25:48,120 --> 00:25:50,520
and here she is in origami form.

524
00:25:50,520 --> 00:25:52,600
And we're going to stick her on.

525
00:25:52,600 --> 00:25:56,000
So, we'll add her
to our Tree of Life.

526
00:25:56,000 --> 00:25:59,880
So, this is the branch, then,
that's the last meeting point

527
00:25:59,880 --> 00:26:01,880
of all of these different lineages.

528
00:26:01,880 --> 00:26:04,600
After that, they start going
their separate ways. Yeah, yeah.

529
00:26:04,600 --> 00:26:09,640
So, we're gradually accumulating
more cousins, more ancestors.

530
00:26:09,920 --> 00:26:14,920
Now we're going to go in search
of some slightly stranger cousins

531
00:26:21,320 --> 00:26:24,320
Thank you. So, this, ladies
and gentlemen, is an egg.

532
00:26:24,320 --> 00:26:25,640
It is not a hen's egg.

533
00:26:25,640 --> 00:26:27,960
This one actually came from an emu.

534
00:26:27,960 --> 00:26:31,240
And the egg is an amazing
biological phenomenon.

535
00:26:31,240 --> 00:26:34,920
If you think about it, it's got to
support the developing embryo

536
00:26:34,920 --> 00:26:37,320
inside it and give it
everything it needs

537
00:26:37,320 --> 00:26:41,160
before that chick eventually
breaks out of the egg

538
00:26:41,160 --> 00:26:44,640
and starts to live on its
own outside of the egg.

539
00:26:44,640 --> 00:26:47,440
So, I am going to...
They've given me a teaspoon.

540
00:26:47,440 --> 00:26:50,880
I can't believe this. I don't
think this is going to cut it.

541
00:26:50,880 --> 00:26:52,440
I'm going to need something

542
00:26:52,440 --> 00:26:54,880
a bit more effective
than a teaspoon, I think.

543
00:26:56,880 --> 00:26:59,000
So, this is Douglas,
who's the head of eggs

544
00:26:59,000 --> 00:27:00,880
from the Natural History Museum.

545
00:27:00,880 --> 00:27:02,680
Indeed. And what have you got,
an Army knife?

546
00:27:02,680 --> 00:27:05,640
Yeah. Lovely. So, what shall I...?
Shall I hold the egg there?

547
00:27:05,640 --> 00:27:08,360
If you could just hold it gently
there, that would be great.

548
00:27:08,360 --> 00:27:10,200
And... Just going
to put that in there.

549
00:27:10,200 --> 00:27:12,720
You've done this before,
haven't you, Douglas? I have.

550
00:27:12,720 --> 00:27:14,440
How many times have
you done it before?

551
00:27:14,440 --> 00:27:16,080
I have done this 18 years running.

552
00:27:16,080 --> 00:27:18,680
18 years of opening eggs.
There you go.

553
00:27:18,680 --> 00:27:20,960
And looking inside them.
So here we go.

554
00:27:22,800 --> 00:27:25,960
Just gently get that egg out.

555
00:27:29,360 --> 00:27:31,200
It's like a cookery show.

556
00:27:31,200 --> 00:27:33,760
Thank you, Douglas.
So, Joe, come and have a look.

557
00:27:33,760 --> 00:27:37,760
There's an enormous yolk
inside that emu egg,

558
00:27:37,760 --> 00:27:40,480
as you might have expected.
You've seen your yolks before.

559
00:27:40,480 --> 00:27:44,640
What the yolk is is a bag
of nutrients, a bag of food

560
00:27:44,640 --> 00:27:49,440
for the developing emu embryo, if
this egg had ever been fertilised.

561
00:27:49,440 --> 00:27:52,280
So, that's full of lovely,
rich nutrients.

562
00:27:52,280 --> 00:27:56,480
And there are other membranes
that develop inside the egg

563
00:27:56,480 --> 00:27:58,240
if an embryo grows in there.

564
00:27:58,240 --> 00:28:02,080
So, there's a membrane that lies
up against the inner surface

565
00:28:02,080 --> 00:28:05,240
of the egg shell and gases
can actually permeate

566
00:28:05,240 --> 00:28:07,920
through the egg shell,
so oxygen can get in,

567
00:28:07,920 --> 00:28:09,320
carbon dioxide can get out.

568
00:28:09,320 --> 00:28:12,760
So, the developing embryo
is exchanging oxygen and carbon

569
00:28:12,760 --> 00:28:14,920
dioxide with the atmosphere.

570
00:28:14,920 --> 00:28:17,520
And there's another
membrane that forms a bag

571
00:28:17,520 --> 00:28:19,680
around the developing embryo itself,

572
00:28:19,680 --> 00:28:22,120
and that is called
the amniotic membrane.

573
00:28:22,120 --> 00:28:25,880
So, the embryo develops
inside this bag of fluid,

574
00:28:25,880 --> 00:28:28,800
and that bag of fluid
is very important, because it

575
00:28:28,800 --> 00:28:33,080
protects the embryo from shocks
and it also means that the embryo

576
00:28:33,080 --> 00:28:37,000
can move its little developing limbs
and those limbs only form properly

577
00:28:37,000 --> 00:28:39,160
if it can do that.

578
00:28:39,160 --> 00:28:42,840
So, we're now going to meet some...

579
00:28:42,840 --> 00:28:47,840
Well, no longer embryos,
but chicks that have got too big

580
00:28:47,840 --> 00:28:50,840
for their amniotic sacs
and too big for their eggshells

581
00:28:50,840 --> 00:28:53,680
and are actually hatching out.

582
00:28:53,680 --> 00:28:57,440
So, these are quails
and we have timed it

583
00:28:57,440 --> 00:28:59,840
so that they are hatching out today.

584
00:28:59,840 --> 00:29:02,120
We've been incubating
these in the Royal Institution

585
00:29:02,120 --> 00:29:07,120
for 17 days, but they're just
popping out of their eggshells,

586
00:29:07,120 --> 00:29:09,880
so they've just reached
the end of their gestation,

587
00:29:09,880 --> 00:29:11,720
and out they come.

588
00:29:14,160 --> 00:29:17,800
And then this, of course, is another
type of animal that lays eggs.

589
00:29:17,800 --> 00:29:19,600
So, over here we have got a reptile.

590
00:29:19,600 --> 00:29:22,280
Does anybody recognise
what that reptile is? Yeah?

591
00:29:22,280 --> 00:29:24,880
A bearded lizard. Yeah,
it's a bearded dragon, yeah,

592
00:29:24,880 --> 00:29:26,760
it's a type of lizard,
a bearded dragon.

593
00:29:26,760 --> 00:29:28,000
He's absolutely wonderful.

594
00:29:28,000 --> 00:29:31,400
So, these reptiles
lay eggs as well, and...

595
00:29:31,400 --> 00:29:33,600
Their eggs are
a little bit different.

596
00:29:33,600 --> 00:29:38,600
Their eggs are leathery
on the outside, so their shells

597
00:29:41,840 --> 00:29:44,560
But they do the same thing -
they let the oxygen in,

598
00:29:44,560 --> 00:29:46,400
and the carbon dioxide out.

599
00:29:46,400 --> 00:29:50,080
Inside, you've got all the same life
support systems that the quails

600
00:29:50,080 --> 00:29:54,000
had inside their eggs
before they actually hatched out.

601
00:29:55,720 --> 00:30:00,760
But now, I want to introduce you to
somebody who hasn't hatched yet.

602
00:30:00,960 --> 00:30:04,720
So, we'll say goodbye to our bearded
dragon and our quails.

603
00:30:04,720 --> 00:30:07,640
And, we'll say hello
to somebody else.

604
00:30:07,640 --> 00:30:09,640
Hi, Rosie.
Hello.

605
00:30:09,640 --> 00:30:12,480
Rosie, you are going
to have a baby. Yes.

606
00:30:12,480 --> 00:30:16,000
And, Rosie is going to let us
have a look at her baby.

607
00:30:16,000 --> 00:30:18,800
So, how pregnant are you? How far
through your pregnancy are you?

608
00:30:18,800 --> 00:30:21,160
23 weeks, due in April.

609
00:30:21,160 --> 00:30:24,320
Wonderful.
So, that's just over halfway.

610
00:30:24,320 --> 00:30:27,560
Human babies are in their
mother's wombs for 40 weeks,

611
00:30:27,560 --> 00:30:29,440
on average, about nine months.

612
00:30:29,440 --> 00:30:31,240
If you hop up there, Rosie.

613
00:30:31,240 --> 00:30:36,200
This is Jill, who is a sonographer,
so she does ultrasound.

614
00:30:36,520 --> 00:30:41,440
Using ultrasound, we can actually
have a look inside Rosie's tummy,

615
00:30:41,440 --> 00:30:43,920
inside her belly,
and have a look at her baby

616
00:30:43,920 --> 00:30:47,080
which is developing inside the womb.

617
00:30:47,080 --> 00:30:50,320
Ultrasound just uses sound waves,
and those sound waves will pass

618
00:30:50,320 --> 00:30:52,840
in and they'll bounce back.

619
00:30:52,840 --> 00:30:54,720
So, it's a little bit like sonar,

620
00:30:54,720 --> 00:30:57,000
a little like submarines
using sonar.

621
00:30:57,000 --> 00:30:59,880
Those sound waves bounce back
and then we can start to see anatomy

622
00:30:59,880 --> 00:31:01,200
or we can see the baby.

623
00:31:01,200 --> 00:31:02,800
This is amazing.

624
00:31:02,800 --> 00:31:05,280
So, Jill, you can see the baby's
head there, can't you?

625
00:31:05,280 --> 00:31:09,880
At the moment, we're looking
at this baby in two dimensions,

626
00:31:09,880 --> 00:31:11,960
so, as though we're looking
right through the head.

627
00:31:11,960 --> 00:31:14,400
But you can do it in 3D
as well, can't you?

628
00:31:14,400 --> 00:31:17,960
I'm just trying. I think the baby's
moved into a difficult position now.

629
00:31:17,960 --> 00:31:21,120
And we call this 4D,
because it's 3D plus time,

630
00:31:21,120 --> 00:31:24,640
so you're actually seeing this baby
moving inside Rosie's womb.

631
00:31:24,640 --> 00:31:28,400
We're just having a little look
to see if we can see the baby's

632
00:31:28,400 --> 00:31:29,560
face peeking out.

633
00:31:29,560 --> 00:31:33,440
It's not behaving very well, but I
do have one that we got earlier.

634
00:31:33,440 --> 00:31:34,920
We can see the face.

635
00:31:37,560 --> 00:31:40,000
How do you feel, Rosie,
seeing your baby in there?

636
00:31:40,000 --> 00:31:41,880
Quite emotional, yeah.
It's amazing!

637
00:31:41,880 --> 00:31:45,600
It's utterly extraordinary to be
able to look at your little baby.

638
00:31:45,600 --> 00:31:47,320
You can see the nose,
you can see a mouth,

639
00:31:47,320 --> 00:31:48,920
a hand up by her face.

640
00:31:48,920 --> 00:31:50,720
She looks very much like my son.
Does she?

641
00:31:50,720 --> 00:31:52,080
When he was a newborn, yeah.

642
00:31:52,080 --> 00:31:54,760
Yeah, yeah.
This is absolutely wonderful.

643
00:31:54,760 --> 00:31:58,800
We can see around this baby
that there's space,

644
00:31:58,800 --> 00:32:01,280
but in fact, this is
fluid-filled space.

645
00:32:01,280 --> 00:32:05,560
We can see that the baby
is inside an amniotic sac.

646
00:32:05,560 --> 00:32:08,880
So, there's a membrane around it
and then this blackness

647
00:32:08,880 --> 00:32:10,960
is the fluid around the baby.

648
00:32:10,960 --> 00:32:14,480
So, just like the developing chick
and the developing reptile

649
00:32:14,480 --> 00:32:18,960
inside its egg,
a human baby starts growing

650
00:32:18,960 --> 00:32:23,560
inside a fluid-filled bag -
the amniotic sac.

651
00:32:23,560 --> 00:32:25,280
But there's something else as well

652
00:32:25,280 --> 00:32:27,880
that we can see here that's really
important. I think it's this.

653
00:32:27,880 --> 00:32:30,960
That's the placenta, isn't it, Jill?
It is, yeah.

654
00:32:30,960 --> 00:32:34,280
So, this big area of grey
here is an organ that is grown

655
00:32:34,280 --> 00:32:38,800
specially inside Rosie
to support her developing baby.

656
00:32:38,800 --> 00:32:42,640
So, this is the life-support system
for human babies in the womb.

657
00:32:42,640 --> 00:32:45,600
And the placenta is
an astonishing organ.

658
00:32:45,600 --> 00:32:50,560
It's allowing Rosie's baby to get
oxygen and nutrients from her blood.

659
00:32:52,120 --> 00:32:55,120
And it's allowing that baby
to get rid of things

660
00:32:55,120 --> 00:32:57,160
like carbon dioxide as well.

661
00:32:57,160 --> 00:33:01,440
So, that baby is being supported
while it's inside the womb,

662
00:33:01,440 --> 00:33:03,840
and it's exchanging gases

663
00:33:03,840 --> 00:33:05,560
and other sorts of compounds

664
00:33:05,560 --> 00:33:06,880
with Rosie's blood.

665
00:33:07,920 --> 00:33:09,720
That is amazing.

666
00:33:11,040 --> 00:33:12,320
Thank you very much.

667
00:33:12,320 --> 00:33:15,000
And let's say thank you again
to Rosie and Jill. Thank you.

668
00:33:23,560 --> 00:33:26,640
It's so amazing, and what an amazing
privilege to see that tiny person

669
00:33:26,640 --> 00:33:29,680
a few months before they actually
emerge into the world.

670
00:33:29,680 --> 00:33:31,800
And who knows?
In a few more years' time, maybe

671
00:33:31,800 --> 00:33:33,880
they'll be here watching
Christmas lectures.

672
00:33:33,880 --> 00:33:35,880
I think they'll have
to come back, won't they?

673
00:33:35,880 --> 00:33:38,360
They've been to the Christmas
lectures, they'll definitely

674
00:33:38,360 --> 00:33:40,200
have to come back to them.

675
00:33:40,200 --> 00:33:43,280
The placenta is
the most amazing organ.

676
00:33:43,280 --> 00:33:47,840
It's the doing all that important
work for that developing baby.

677
00:33:47,840 --> 00:33:51,000
But it does something else and
that's really important, as well.

678
00:33:51,000 --> 00:33:56,040
Because that developing baby is
a genetically distinct individual.

679
00:33:56,800 --> 00:34:01,240
That baby is not the same
as his or her mum.

680
00:34:01,240 --> 00:34:03,960
That baby is a new person.

681
00:34:03,960 --> 00:34:07,600
So, usually, your immune system
would seek out anything

682
00:34:07,600 --> 00:34:09,520
that wasn't you and get rid of it.

683
00:34:09,520 --> 00:34:12,960
That's what your immune system does,
doesn't it? It protects you.

684
00:34:12,960 --> 00:34:16,760
So, there has to be a barrier
between that developing baby

685
00:34:16,760 --> 00:34:18,640
and the mum's immune system,

686
00:34:18,640 --> 00:34:22,080
and the placenta is a really
important part of that.

687
00:34:22,080 --> 00:34:25,280
And then - a fantastic
clue as to how it does

688
00:34:25,280 --> 00:34:27,640
that comes from genetics.

689
00:34:27,640 --> 00:34:29,520
Did you say genetics?
I said it again.

690
00:34:29,520 --> 00:34:34,520
So, there's actually something
really special about placenta.

691
00:34:35,280 --> 00:34:38,680
And we can see that in something
really special about the genetics

692
00:34:38,680 --> 00:34:39,800
of the placenta.

693
00:34:39,800 --> 00:34:42,320
As Alice said,
it's a barrier in your body.

694
00:34:42,320 --> 00:34:45,840
It's a barrier between
the maternal and the foetal side.

695
00:34:45,840 --> 00:34:48,160
You actually have lots of other
places in your body

696
00:34:48,160 --> 00:34:50,560
where you have barriers -
the lining of your lungs,

697
00:34:50,560 --> 00:34:54,200
the lining of your intestine,
the lining of your blood vessels.

698
00:34:54,200 --> 00:34:56,280
Those barriers look a bit like this.

699
00:34:56,280 --> 00:34:58,400
So, these are cells, obviously.

700
00:34:58,400 --> 00:34:59,920
And this is a layer of cells.

701
00:34:59,920 --> 00:35:01,200
So, if you look at this -

702
00:35:01,200 --> 00:35:03,960
we have this layer
of cells and that's pretty good.

703
00:35:03,960 --> 00:35:06,520
It's good enough for most
of those parts of your body.

704
00:35:06,520 --> 00:35:10,000
But you can also see that there are
lots of holes there, there are gaps.

705
00:35:10,000 --> 00:35:13,240
Even if it's a nice,
tightly packed group of cells,

706
00:35:13,240 --> 00:35:15,720
there are gaps that
can get through there.

707
00:35:15,720 --> 00:35:18,640
So, things can still get through.
So, the placenta is a bit different.

708
00:35:18,640 --> 00:35:20,080
Alice, maybe you could help me?

709
00:35:20,080 --> 00:35:22,560
Because in the placenta,
the cells, the neighbouring

710
00:35:22,560 --> 00:35:24,000
cells, merge together.

711
00:35:24,000 --> 00:35:26,240
And it doesn't happen
like this, by the way,

712
00:35:26,240 --> 00:35:29,880
because the way it happens
in a placenta is that the cells,

713
00:35:29,880 --> 00:35:32,920
the neighbouring cells,
the membranes just join

714
00:35:32,920 --> 00:35:35,560
together like this.
It's not...

715
00:35:35,560 --> 00:35:36,760
This isn't a cooking show!

716
00:35:36,760 --> 00:35:39,360
This is the
Christmas lectures, Alice.

717
00:35:39,360 --> 00:35:41,320
But the neighbouring cells
join together.

718
00:35:41,320 --> 00:35:43,280
And this doesn't
just happen randomly.

719
00:35:43,280 --> 00:35:45,360
There's actually a special gene

720
00:35:45,360 --> 00:35:47,680
and it makes a protein
called syncytin

721
00:35:47,680 --> 00:35:48,960
that makes this happen.

722
00:35:48,960 --> 00:35:51,760
The neighbouring cells,
they join together and you get

723
00:35:51,760 --> 00:35:54,080
something that looks a bit
more like a pancake.

724
00:35:54,080 --> 00:35:56,920
When we look at the sequence
of these genes and try to see

725
00:35:56,920 --> 00:35:59,160
what else they look
like anywhere else,

726
00:35:59,160 --> 00:36:02,240
we find that they're just
like genes that make the outer

727
00:36:02,240 --> 00:36:04,560
coating of viruses.

728
00:36:04,560 --> 00:36:07,440
So, these genes are very,
very similar when we look

729
00:36:07,440 --> 00:36:08,600
at the sequence.

730
00:36:08,600 --> 00:36:11,440
And it makes sense,
because when a virus causes

731
00:36:11,440 --> 00:36:14,880
infection, what happens is the
virus comes along and it merges

732
00:36:14,880 --> 00:36:17,520
into the cell that it's infecting.

733
00:36:17,520 --> 00:36:20,640
And what we see in the placenta
is that the neighbouring cells

734
00:36:20,640 --> 00:36:21,640
are merging together.

735
00:36:21,640 --> 00:36:24,560
So, it actually makes sense
that the function is very,

736
00:36:24,560 --> 00:36:28,840
very similar in the virus and
here recycled into the placenta.

737
00:36:28,840 --> 00:36:31,200
So, how does a virus gene
get into...

738
00:36:31,200 --> 00:36:33,560
I mean, we're talking
about human DNA? Yes.

739
00:36:33,560 --> 00:36:35,560
Why is there a virus gene
in human DNA?

740
00:36:35,560 --> 00:36:37,560
Well, it's a bit weird, isn't it?

741
00:36:37,560 --> 00:36:41,720
But actually, in our ancestors,
they would have had viral infections

742
00:36:41,720 --> 00:36:43,800
all the time, like
I'm sure everybody here

743
00:36:43,800 --> 00:36:45,480
has had a virus at some point.

744
00:36:45,480 --> 00:36:49,200
When you get a viral infection,
it actually enters into the cell

745
00:36:49,200 --> 00:36:51,960
and releases its DNA into the cell.

746
00:36:51,960 --> 00:36:56,120
Sometimes when it does that,
the DNA actually integrates

747
00:36:56,120 --> 00:36:58,840
into the DNA of the person
that's being infected.

748
00:36:58,840 --> 00:37:02,240
If you can imagine some
ancient mammalian ancestors,

749
00:37:02,240 --> 00:37:05,320
they had lots of viral infections
every now and again -

750
00:37:05,320 --> 00:37:08,120
the virus, instead of just causing
an infection and then the infection

751
00:37:08,120 --> 00:37:10,840
ending, the DNA hung around.

752
00:37:10,840 --> 00:37:13,240
This is actually about 8%

753
00:37:13,240 --> 00:37:16,320
of what we call the
human genome.

754
00:37:16,320 --> 00:37:18,800
Looks like virus DNA. So that
tells you how many infections

755
00:37:18,800 --> 00:37:20,400
there have been over
the years as well.

756
00:37:20,400 --> 00:37:23,360
That's a huge proportion, as well.
A huge proportion, yeah.

757
00:37:23,360 --> 00:37:27,720
So, presumably, that viral DNA
then gets inserted into our DNA.

758
00:37:27,720 --> 00:37:30,640
We've dismantled it a bit,
we've taken bits out of it

759
00:37:30,640 --> 00:37:33,960
to stop it being pathological.
Yes. To stop it hurting us.

760
00:37:33,960 --> 00:37:36,640
But then what happened is
the evolution, kind of,

761
00:37:36,640 --> 00:37:39,320
stumbled across this
deactivated virus gene,

762
00:37:39,320 --> 00:37:41,480
and suddenly,
it became useful again.

763
00:37:41,480 --> 00:37:43,440
So it's like the scrap yard.

764
00:37:43,440 --> 00:37:45,400
There's all these pieces
that are left over,

765
00:37:45,400 --> 00:37:48,440
and they still kind of work a bit
but they're not quite working -

766
00:37:48,440 --> 00:37:51,560
they're a bit broken.
So, for the virus,

767
00:37:51,560 --> 00:37:54,040
this gene is helping the virus

768
00:37:54,040 --> 00:37:56,640
enter the cell by
merging into its membrane.

769
00:37:56,640 --> 00:37:57,960
And now in the placenta,

770
00:37:57,960 --> 00:38:00,920
it's helping the neighbouring cells
merge into each other.

771
00:38:00,920 --> 00:38:03,600
So, it's kind of recycling
the same function.

772
00:38:03,600 --> 00:38:06,120
It's a brilliant bit
of recycling, isn't it? Fabulous.

773
00:38:06,120 --> 00:38:11,120
So, this shows us an important clue
as to how the placenta came

774
00:38:11,480 --> 00:38:14,320
about in our ancient
mammal ancestors.

775
00:38:14,320 --> 00:38:17,880
But still, what we've discovered
is a connection going back even

776
00:38:17,880 --> 00:38:22,160
further than that with those
egg-laying relatives of ours.

777
00:38:22,160 --> 00:38:25,800
Because of that amniotic membrane
around the developing embryo

778
00:38:25,800 --> 00:38:30,280
in both humans and in reptiles
and birds as well.

779
00:38:30,280 --> 00:38:33,200
So, now we can put another relative,
another ancestor in fact,

780
00:38:33,200 --> 00:38:34,960
on the Tree of Life.
It's beautiful.

781
00:38:34,960 --> 00:38:37,600
This time, the ancestor
that we've got is a reptile.

782
00:38:37,600 --> 00:38:42,360
So this is a reptile
that was an egg-laying reptile.

783
00:38:42,360 --> 00:38:47,240
It's a mammal-like reptile and it
lived about 300 million years ago.

784
00:38:47,240 --> 00:38:48,880
So, we're going higher.
Yeah.

785
00:38:48,880 --> 00:38:51,400
So there is Juramaia,
we're having to go back here.

786
00:38:51,400 --> 00:38:53,360
We've got the egg-laying
things over here,

787
00:38:53,360 --> 00:38:56,080
so we've got a chicken and
maybe a crocodile and a lizard.

788
00:38:56,080 --> 00:38:58,880
So we follow the thread
up and we get to...

789
00:38:58,880 --> 00:39:02,240
Will I help you? I can help.
Thank you. There we go.

790
00:39:02,240 --> 00:39:05,240
So there is an ancient
mammal-like reptile,

791
00:39:05,240 --> 00:39:09,200
300 million years ago
on the Tree of Life.

792
00:39:09,200 --> 00:39:11,920
So as we're going up, we're just
going further back in time.

793
00:39:11,920 --> 00:39:16,960
Yeah. And discovering more
cousins and more ancestors -

794
00:39:17,080 --> 00:39:18,840
and egg-laying ancestors this time.

795
00:39:18,840 --> 00:39:20,840
So then we've got
an answer to the question,

796
00:39:20,840 --> 00:39:23,920
which came first,
the chicken or the egg? Oh.

797
00:39:23,920 --> 00:39:26,560
Biologists know
that eggs came first.

798
00:39:26,560 --> 00:39:30,920
This egg-laying reptile
was there ages before anything

799
00:39:30,920 --> 00:39:34,640
like a chicken evolved.
I know, I know! Oh, really?

800
00:39:34,640 --> 00:39:37,560
Just wanted to spoil the joke!

801
00:39:37,560 --> 00:39:42,280
So now I want to look at
these creatures over here.

802
00:39:42,280 --> 00:39:44,840
So here, we've got
some origami fish.

803
00:39:44,840 --> 00:39:47,800
So I want to find out
our connection with fish.

804
00:39:47,800 --> 00:39:49,480
I'm just going
to disappear out here,

805
00:39:49,480 --> 00:39:51,480
but you might be able
to see me on the other side.

806
00:39:51,480 --> 00:39:53,320
Hello.

807
00:39:53,320 --> 00:39:56,400
In this tank here,
we've got a type of shark.

808
00:39:56,400 --> 00:39:59,200
So, this is a type of dogfish.

809
00:40:00,360 --> 00:40:02,520
And this is another
relative of ours.

810
00:40:02,520 --> 00:40:05,960
So, another cousin
on the Tree of Life.

811
00:40:05,960 --> 00:40:08,520
And, you know, you might have been
persuaded that the horse

812
00:40:08,520 --> 00:40:11,160
was a relative of ours,
had the same bones in its legs.

813
00:40:11,160 --> 00:40:14,160
And, the armadillo and the bat. Am I
starting to stretch things now?

814
00:40:14,160 --> 00:40:18,080
Hmm. Maybe a little, but there
are still similarities here.

815
00:40:18,080 --> 00:40:19,560
There are certainly differences.

816
00:40:19,560 --> 00:40:22,200
This fish has got fins
rather than limbs.

817
00:40:22,200 --> 00:40:24,720
It lives in water -
it can extract oxygen

818
00:40:24,720 --> 00:40:26,680
from the water,
whereas I breathe air.

819
00:40:26,680 --> 00:40:30,960
But that fish has got a skull
and I've got a skull.

820
00:40:30,960 --> 00:40:32,320
And it's got a spine.

821
00:40:32,320 --> 00:40:34,600
So we are both vertebrates.

822
00:40:34,600 --> 00:40:37,560
It is getting more tricky
to see similarities, though.

823
00:40:37,560 --> 00:40:41,280
But, if we go back to an
earlier stage of development,

824
00:40:41,280 --> 00:40:44,120
there are many more
similarities to see.

825
00:40:45,760 --> 00:40:49,600
So, what I want to do now
is introduce you

826
00:40:49,600 --> 00:40:52,680
to a 3D-printed human embryo.

827
00:40:52,680 --> 00:40:56,600
So, this is a 3D print of
a human embryo

828
00:40:56,600 --> 00:41:00,560
at around four weeks of gestation.

829
00:41:00,560 --> 00:41:02,600
And this is about the size
you were then.

830
00:41:02,600 --> 00:41:05,480
And you're barely the size
of a fingernail clipping.

831
00:41:05,480 --> 00:41:07,240
But there are some
important clues here

832
00:41:07,240 --> 00:41:09,320
if we look at the anatomy
of an early embryo.

833
00:41:09,320 --> 00:41:14,360
We're not going to see them
in this tiny little 3D print.

834
00:41:14,360 --> 00:41:16,600
So I'm going to give you
that without sneezing.

835
00:41:16,600 --> 00:41:17,640
Thank you.

836
00:41:17,640 --> 00:41:22,640
What we've done is we've scaled
up the embryo to about 800 times

837
00:41:22,640 --> 00:41:27,680
its actual size at the end
of the fourth week of development.

838
00:41:28,240 --> 00:41:29,880
And I've got two embryos here.

839
00:41:29,880 --> 00:41:31,840
One of them's a fish,
one of them is a human.

840
00:41:31,840 --> 00:41:33,480
Which one do you think is which?

841
00:41:33,480 --> 00:41:36,760
Which one do you think is a human,
and which one you think is a fish?

842
00:41:36,760 --> 00:41:39,520
That one's a human. That one's
a fish. Yeah, you're right!

843
00:41:39,520 --> 00:41:41,600
I mean, look how similar they are.

844
00:41:41,600 --> 00:41:46,040
It is really shocking how similar
the fish and the human embryo

845
00:41:46,040 --> 00:41:48,200
are at this particular stage
of development.

846
00:41:48,200 --> 00:41:51,000
They've both got a head, they've
both got a developing eye,

847
00:41:51,000 --> 00:41:52,360
you can just see up there.

848
00:41:52,360 --> 00:41:55,640
They've both got tails,
so human embryos have tails.

849
00:41:55,640 --> 00:41:57,840
And then later on, they disappear,
so I don't think any

850
00:41:57,840 --> 00:41:59,760
of you have got tails particularly.

851
00:41:59,760 --> 00:42:03,040
You'll have a coccyx bone
but not an actual tail.

852
00:42:03,040 --> 00:42:06,600
But there are these strange,
strange things in the neck.

853
00:42:06,600 --> 00:42:09,000
So, this is the human embryo.

854
00:42:09,000 --> 00:42:12,280
You can see that the human embryo's
got odd bars,

855
00:42:12,280 --> 00:42:16,400
or ridges, in its neck
and the fish embryo has as well.

856
00:42:16,400 --> 00:42:21,280
Now, in the fish, those ridges
are going to develop into something

857
00:42:21,280 --> 00:42:23,040
which you can see in the adults.

858
00:42:23,040 --> 00:42:25,880
And I don't know whether
we'll be able to see it.

859
00:42:25,880 --> 00:42:28,280
Can we just about see?
Yes, we can.

860
00:42:28,280 --> 00:42:30,720
Can you see the gills opening
and closing on the side

861
00:42:30,720 --> 00:42:32,280
of our dogfish's neck?

862
00:42:33,280 --> 00:42:36,640
So, you're looking down towards
the base where the fin is joining,

863
00:42:36,640 --> 00:42:40,080
and you can just see those gills
opening and closing.

864
00:42:40,080 --> 00:42:44,360
So that's what those
developed into in the fish.

865
00:42:44,360 --> 00:42:46,800
And then you go - what?

866
00:42:46,800 --> 00:42:48,400
Why are there things
in the human embryo

867
00:42:48,400 --> 00:42:50,640
that look as though they're
going to develop into gills?

868
00:42:50,640 --> 00:42:52,880
Anyone in the room got gills?

869
00:42:52,880 --> 00:42:54,760
Anyone at all got gills?

870
00:42:54,760 --> 00:42:56,960
You haven't got gills!
You can't breathe underwater!

871
00:42:56,960 --> 00:42:58,200
I'd love to have gills,

872
00:42:58,200 --> 00:43:00,320
I'd love to be able
to be underwater. But,

873
00:43:00,320 --> 00:43:02,960
I'd to give up some
of the anatomy that I have got

874
00:43:02,960 --> 00:43:04,760
that's really, really useful to me.

875
00:43:04,760 --> 00:43:08,720
Because something very interesting
happens with these gill arches

876
00:43:08,720 --> 00:43:10,600
in the embryo.

877
00:43:10,600 --> 00:43:13,720
Some structures in embryology,
in embryonic development,

878
00:43:13,720 --> 00:43:16,400
appear and then disappear.
That's what happened to the tail.

879
00:43:16,400 --> 00:43:19,320
So the tail appears
and then it just disappears.

880
00:43:19,320 --> 00:43:22,960
Not so with these early gill arches.

881
00:43:22,960 --> 00:43:26,640
Inside those gill arches,
there are all sorts of bits

882
00:43:26,640 --> 00:43:28,920
of anatomy that proved to be useful.

883
00:43:28,920 --> 00:43:31,680
Inside these really,
really early structures,

884
00:43:31,680 --> 00:43:34,240
we've already got little
arteries growing out.

885
00:43:34,240 --> 00:43:36,320
Which, if you were
going to be a fish,

886
00:43:36,320 --> 00:43:40,080
would supply your gills with
deoxygenated blood,

887
00:43:40,080 --> 00:43:42,520
ready to pick up oxygen
from the water.

888
00:43:42,520 --> 00:43:47,520
Inside these developing gill arches,
are developing muscles,

889
00:43:48,240 --> 00:43:50,400
which, if you were going
to be a fish, would open

890
00:43:50,400 --> 00:43:53,800
and close your gills
like our dogfish.

891
00:43:53,800 --> 00:43:56,760
Inside these bars,
there are also little bits

892
00:43:56,760 --> 00:43:59,720
of cartilage which, again,
if you were going to be a fish,

893
00:43:59,720 --> 00:44:02,360
would support your gills.

894
00:44:02,360 --> 00:44:04,000
But you're not going to be a fish.

895
00:44:04,000 --> 00:44:07,000
And what happens instead
is that all of those structures form

896
00:44:07,000 --> 00:44:10,000
and then they get recycled
into other things.

897
00:44:10,000 --> 00:44:13,480
And they get recycled
into all sorts of structures

898
00:44:13,480 --> 00:44:15,520
in our heads and in our necks.

899
00:44:16,920 --> 00:44:20,520
One of the things they get
recycled into is this.

900
00:44:20,520 --> 00:44:23,440
Now, this is one
of my favourite bones.

901
00:44:23,440 --> 00:44:25,400
It's a strange little bone.

902
00:44:25,400 --> 00:44:28,240
It is U-shaped, as you can see.

903
00:44:28,240 --> 00:44:31,680
And it's called the hyoid bone.

904
00:44:31,680 --> 00:44:35,520
This little bone sits
up here in your neck.

905
00:44:35,520 --> 00:44:37,760
It's quite difficult to feel it,
and don't try too hard

906
00:44:37,760 --> 00:44:40,440
because it's uncomfortable.
But that's where it is.

907
00:44:40,440 --> 00:44:44,120
It anchors the muscles that form
the floor of your mouth.

908
00:44:44,120 --> 00:44:48,240
And then, it sits there as something
for your voice box to hang from.

909
00:44:48,240 --> 00:44:51,840
So what I've got here
is a much bigger model of that.

910
00:44:51,840 --> 00:44:54,000
And here's the hyoid,
and then underneath it

911
00:44:54,000 --> 00:44:57,760
are the cartilages of your larynx,
or your voice box.

912
00:44:57,760 --> 00:45:01,080
So, that's what I'm using
to speak to you right now.

913
00:45:01,080 --> 00:45:03,240
But those cartilages do
another important thing,

914
00:45:03,240 --> 00:45:05,640
as well as providing
the mechanism of speech,

915
00:45:05,640 --> 00:45:08,200
they also keep the airway open.

916
00:45:08,200 --> 00:45:10,720
Something very important
that they're doing.

917
00:45:10,720 --> 00:45:15,760
These cartilages and that bone
come the gill arches in the embryo.

918
00:45:15,960 --> 00:45:19,640
So we can add the fish
to our Tree of Life.

919
00:45:19,640 --> 00:45:22,520
We can bring it in as a cousin,
and we can actually add

920
00:45:22,520 --> 00:45:24,360
an ancient fish ancestor.

921
00:45:26,360 --> 00:45:28,440
There is Juramaia,
our mammal ancestor.

922
00:45:28,440 --> 00:45:30,120
There's our reptile.

923
00:45:30,120 --> 00:45:31,280
And the fish, then.

924
00:45:31,280 --> 00:45:33,400
So, we've got modern
fish over there.

925
00:45:33,400 --> 00:45:36,800
If we trace that line up and across,
then that's going to join up

926
00:45:36,800 --> 00:45:38,880
with the line that
come up from humans.

927
00:45:38,880 --> 00:45:42,760
So, we're finding
this fish ancestor,

928
00:45:42,760 --> 00:45:47,360
500 million years ago
we've travelled now, back in time.

929
00:45:48,360 --> 00:45:50,240
But now... I know there's someone

930
00:45:50,240 --> 00:45:53,880
who's itching to introduce you
to yet another cousin,

931
00:45:53,880 --> 00:45:55,720
an even stranger cousin.

932
00:45:55,720 --> 00:45:57,720
Through the medium of genetics...

933
00:45:57,720 --> 00:45:59,920
Aha, you've said it again!

934
00:45:59,920 --> 00:46:04,080
So, Alice isn't the only one
who can have fun with cool animals

935
00:46:04,080 --> 00:46:06,240
at the Christmas lectures.

936
00:46:06,240 --> 00:46:09,520
So, Alice brought in
a horse and an armadillo.

937
00:46:09,520 --> 00:46:10,880
And a bat.
And a bat.

938
00:46:10,880 --> 00:46:13,520
But I present to you -
the fruit fly.

939
00:46:15,920 --> 00:46:18,560
So maybe you've seen these before,
you've probably seen them

940
00:46:18,560 --> 00:46:22,800
if you've left some over ripe fruit
lying around your kitchen

941
00:46:22,800 --> 00:46:25,440
in the summertime.
They're so wonderful!

942
00:46:25,440 --> 00:46:26,800
You are going to believe me.

943
00:46:26,800 --> 00:46:28,800
You are going to soon think
that these are cool.

944
00:46:28,800 --> 00:46:30,280
You don't think they're cool yet

945
00:46:30,280 --> 00:46:32,360
but wait till I finish
telling you about them.

946
00:46:32,360 --> 00:46:35,720
So, we're talking
about similarities.

947
00:46:35,720 --> 00:46:37,000
And just take a little look.

948
00:46:37,000 --> 00:46:39,200
These guys don't look similar to us
at all, do they?

949
00:46:39,200 --> 00:46:40,800
I mean, they don't even have bones

950
00:46:40,800 --> 00:46:43,200
so Alice won't be interested,
we know this already.

951
00:46:43,200 --> 00:46:46,280
Oh, they wear their skeletons on
the outside? How ridiculous!

952
00:46:46,280 --> 00:46:47,560
No bones to speak of.

953
00:46:47,560 --> 00:46:52,600
They have beautiful red compound
eyes, and they've got six legs,

954
00:46:53,120 --> 00:46:56,480
and they've got those
lovely, delicate wings.

955
00:46:56,480 --> 00:46:59,920
So, we're talking about trying
to find similarities

956
00:46:59,920 --> 00:47:01,920
and I bring out these things.

957
00:47:01,920 --> 00:47:06,440
But these guys are the
absolute heroes of genetics.

958
00:47:06,440 --> 00:47:11,480
So, they're actually responsible
for at least six Nobel prizes.

959
00:47:11,800 --> 00:47:14,360
So it's thanks to these... Do you
want to give them their prizes,

960
00:47:14,360 --> 00:47:18,200
Alice? Prizes? Who said prizes!

961
00:47:18,200 --> 00:47:21,520
It's thanks to these that we
understand the basis of a gene.

962
00:47:21,520 --> 00:47:23,680
That we know about
the existence of chromosomes.

963
00:47:23,680 --> 00:47:26,480
The existence of sex chromosomes.

964
00:47:26,480 --> 00:47:31,320
And we also understand your body
clock, the thing that makes you feel

965
00:47:31,320 --> 00:47:34,320
wakeful in the morning,
sleepy at night and hungry

966
00:47:34,320 --> 00:47:35,880
at particular times of day.

967
00:47:35,880 --> 00:47:40,880
And so, the story of these goes back
over 100 years to a place called

968
00:47:41,960 --> 00:47:43,760
the fly room, which was a lab.

969
00:47:43,760 --> 00:47:46,640
They called it the fly room because
it was full of these lovely guys.

970
00:47:46,640 --> 00:47:49,160
And these were the first people

971
00:47:49,160 --> 00:47:52,920
who decided to study these
fruit flies for genetics.

972
00:47:52,920 --> 00:47:56,280
The thing that they were really
interested in though was mutants.

973
00:47:56,280 --> 00:47:59,080
They had things like this.
This is an extraordinary mutant.

974
00:47:59,080 --> 00:48:03,560
The one on your right is a normal
fly with its beautiful red eye.

975
00:48:03,560 --> 00:48:05,760
But something's totally missing
on the other side.

976
00:48:05,760 --> 00:48:07,400
That one's completely
missing its eye.

977
00:48:07,400 --> 00:48:08,960
So that's an example of a mutant.

978
00:48:08,960 --> 00:48:12,400
And by studying these mutants,
they could understand lots of common

979
00:48:12,400 --> 00:48:16,480
principles, lots of the basic
principles of genetics.

980
00:48:16,480 --> 00:48:19,720
But there was a particular kind
of mutant that was especially

981
00:48:19,720 --> 00:48:22,360
interesting for what we want
to talk about today.

982
00:48:22,360 --> 00:48:26,000
And those were mutants
that had body parts

983
00:48:26,000 --> 00:48:29,400
in the wrong places.
So, look at this one here.

984
00:48:29,400 --> 00:48:31,080
On the left, this time
is a normal one.

985
00:48:31,080 --> 00:48:33,960
That's the fly head from the front.

986
00:48:33,960 --> 00:48:38,040
But on the right, something has gone
quite drastically wrong.

987
00:48:38,040 --> 00:48:40,440
And what's happening there
is there are actually

988
00:48:40,440 --> 00:48:44,000
legs growing where
they should be antennae.

989
00:48:44,000 --> 00:48:46,360
So they're legs,
but they're growing

990
00:48:46,360 --> 00:48:47,920
in totally the wrong place.

991
00:48:47,920 --> 00:48:51,200
So by studying thousands
and thousands of these

992
00:48:51,200 --> 00:48:52,880
kinds of mutants,

993
00:48:52,880 --> 00:48:56,680
they discovered a small number
of genes that could change

994
00:48:56,680 --> 00:48:58,560
the body parts around.

995
00:48:58,560 --> 00:49:01,560
And these genes are
master control genes.

996
00:49:01,560 --> 00:49:05,280
These are regulators and they turn
on lots of other sets of genes,

997
00:49:05,280 --> 00:49:07,160
and they make
everything else happen.

998
00:49:07,160 --> 00:49:09,280
So, they're kind of
like a master key

999
00:49:09,280 --> 00:49:11,520
that unlocks a whole
pile of things.

1000
00:49:11,520 --> 00:49:13,600
And these are called Hox genes.

1001
00:49:13,600 --> 00:49:17,800
So, the correct Hox genes turn
on to get the right body parts

1002
00:49:17,800 --> 00:49:19,120
in the right places.

1003
00:49:19,120 --> 00:49:22,080
But to really explain this,
I think we need more than words.

1004
00:49:22,080 --> 00:49:24,200
I think we need actually
to play a game...

1005
00:49:24,200 --> 00:49:26,760
Called Build A Fly!
Build A Fly!

1006
00:49:26,760 --> 00:49:29,000
And we are going
to need some volunteers.

1007
00:49:29,000 --> 00:49:30,760
Somebody in a lovely rainbow jumper.

1008
00:49:30,760 --> 00:49:33,000
And we'll pick somebody
from over here as well.

1009
00:49:33,000 --> 00:49:35,920
In your lovely turquoise jacket.
What's your name?

1010
00:49:35,920 --> 00:49:37,440
Louis.
Louis?

1011
00:49:39,640 --> 00:49:42,440
Would you stand here
in front of this bowl?

1012
00:49:42,440 --> 00:49:44,400
And what's your name?
Alice.

1013
00:49:44,400 --> 00:49:46,680
Alice! Good name.
We've got an Alice.

1014
00:49:46,680 --> 00:49:48,120
And this is your part here.

1015
00:49:48,120 --> 00:49:50,400
And I've got Holly
and Louis over here.

1016
00:49:50,400 --> 00:49:51,680
There's a picture here.

1017
00:49:51,680 --> 00:49:54,560
So, development is really,
really complex but we're going

1018
00:49:54,560 --> 00:49:57,640
to pick it up where
the fly embryo has already

1019
00:49:57,640 --> 00:49:59,680
divided into segments.

1020
00:49:59,680 --> 00:50:01,520
So, it's grown a bit.

1021
00:50:01,520 --> 00:50:03,960
You can think about this shape here.

1022
00:50:03,960 --> 00:50:06,960
It's a bit like a little grub,
it's got these little segments.

1023
00:50:06,960 --> 00:50:09,360
These are artificial colours
that have just been added

1024
00:50:09,360 --> 00:50:10,760
so you can see them.

1025
00:50:10,760 --> 00:50:13,120
In the real thing,
there's 14 segments

1026
00:50:13,120 --> 00:50:16,440
but we've simplified
and we have four segments.

1027
00:50:16,440 --> 00:50:17,840
So, these are our four segments.

1028
00:50:17,840 --> 00:50:21,760
We've got one, two, three,

1029
00:50:21,760 --> 00:50:24,400
four segments of this fly.

1030
00:50:24,400 --> 00:50:26,520
In every segment,
it looks kind of the same.

1031
00:50:26,520 --> 00:50:28,560
We don't have any
structures growing yet.

1032
00:50:28,560 --> 00:50:30,720
We don't have any legs,
we don't have any wings

1033
00:50:30,720 --> 00:50:32,240
growing anywhere yet.

1034
00:50:32,240 --> 00:50:35,200
If we look inside,
it also looks quite the same.

1035
00:50:35,200 --> 00:50:37,560
Because one thing we have here...

1036
00:50:38,920 --> 00:50:41,080
..are these Hox genes.

1037
00:50:41,080 --> 00:50:46,160
These master regulator Hox genes
that can control locks

1038
00:50:46,400 --> 00:50:49,760
and unlock huge portions
of the genome to get the right body

1039
00:50:49,760 --> 00:50:51,480
parts in the right place.

1040
00:50:51,480 --> 00:50:54,760
So, I've got these four Hox genes
in the first segment.

1041
00:50:54,760 --> 00:50:56,720
But they're also there
in the second segment,

1042
00:50:56,720 --> 00:50:59,240
and in the third segment.
Look, Alice has the same set there.

1043
00:50:59,240 --> 00:51:00,960
So these are all present everywhere.

1044
00:51:00,960 --> 00:51:03,560
So that's not the difference
that's going to make it work.

1045
00:51:03,560 --> 00:51:05,480
If we look here,
we've got the fly genome

1046
00:51:05,480 --> 00:51:07,240
that can be potentially unlocked.

1047
00:51:07,240 --> 00:51:10,000
But we've got the fly genome here,
we've got same genome

1048
00:51:10,000 --> 00:51:12,560
in all of the cells
of the entire body.

1049
00:51:12,560 --> 00:51:16,520
So, what we need to happen
is we need the right body parts

1050
00:51:16,520 --> 00:51:19,320
to grow in the right place.
So we need something else.

1051
00:51:19,320 --> 00:51:23,160
We need only one Hox gene
to be turned on there.

1052
00:51:23,160 --> 00:51:27,040
Only one to be turned on there,
only one there, and only one there.

1053
00:51:27,040 --> 00:51:28,480
But which one is the right one?

1054
00:51:28,480 --> 00:51:30,280
Only the right one
should get turned on

1055
00:51:30,280 --> 00:51:32,680
if we want to get the right parts
in the right places.

1056
00:51:32,680 --> 00:51:35,080
So, there's an extra something
I haven't shown you yet.

1057
00:51:35,080 --> 00:51:37,320
Which is, there is a difference
inside these segments.

1058
00:51:37,320 --> 00:51:41,240
And I'm going to represent
this slight difference with colour.

1059
00:51:41,240 --> 00:51:42,760
Now, don't turn around yet.

1060
00:51:42,760 --> 00:51:46,560
Now, each of the cabinets is
lit up in a particular colour.

1061
00:51:46,560 --> 00:51:50,280
That colour is going to match
one of your Hox genes here.

1062
00:51:50,280 --> 00:51:54,280
So, when I give you the word,
I want you to quickly turn around,

1063
00:51:54,280 --> 00:51:56,920
look what colour you have got,
then find the matching key.

1064
00:51:56,920 --> 00:52:00,040
And then, you're going to figure out
which cabinet door will open.

1065
00:52:00,040 --> 00:52:02,880
So, you're going to have to try
a few of them until you find

1066
00:52:02,880 --> 00:52:06,000
which one's open. Right, do we get
it? Are you ready? Steady, go!

1067
00:52:06,000 --> 00:52:09,840
We've got red, yellow, green, blue!

1068
00:52:09,840 --> 00:52:11,760
Keep trying, try them all!

1069
00:52:15,040 --> 00:52:16,400
It's got to be that one.

1070
00:52:16,400 --> 00:52:17,960
Can you get the key in?

1071
00:52:19,600 --> 00:52:20,880
Yes!

1072
00:52:20,880 --> 00:52:24,120
Yes! Now, you might want to...
Can you slip your shoes off?

1073
00:52:24,120 --> 00:52:27,880
I can help you. Just kick them off.

1074
00:52:27,880 --> 00:52:29,280
I'll help you get into this.

1075
00:52:29,280 --> 00:52:31,640
Now, you've got
a lovely bolero jacket.

1076
00:52:31,640 --> 00:52:36,600
Put your arms through that. On
the other side. Close the front.

1077
00:52:36,600 --> 00:52:39,120
OK. We'll get you lining up.
Here we go.

1078
00:52:39,120 --> 00:52:40,920
You did get the tricky one,
I'm so sorry.

1079
00:52:40,920 --> 00:52:42,960
There we go, and there's
another strap there.

1080
00:52:42,960 --> 00:52:46,080
Right - before we started, nothing
was growing anywhere, we didn't know

1081
00:52:46,080 --> 00:52:48,880
what anything was going to look
like. We didn't even know which was

1082
00:52:48,880 --> 00:52:51,680
the head end and which was the tail
end. But now we've got your head.

1083
00:52:51,680 --> 00:52:54,120
Look at these lovely wings. Can you
turn around a little bit?

1084
00:52:54,120 --> 00:52:55,560
Lovely wings are growing here.

1085
00:52:55,560 --> 00:52:57,360
And look.
Lovely fly legs.

1086
00:52:57,360 --> 00:53:00,080
And Louis is the back.
Brilliant.

1087
00:53:00,080 --> 00:53:01,880
And look at this.
We now have a fly!

1088
00:53:04,520 --> 00:53:07,640
Thank you so much.
Thank you.

1089
00:53:07,640 --> 00:53:10,280
Brilliant volunteers.
And you make a wonderful fly.

1090
00:53:10,280 --> 00:53:11,960
I'm sure you're good humans too.

1091
00:53:11,960 --> 00:53:14,560
That's all of the segments,
and all in the right order as well.

1092
00:53:14,560 --> 00:53:16,720
Yeah, yeah, yeah.
So, these Hox genes

1093
00:53:16,720 --> 00:53:18,960
are just at this amazing juncture.

1094
00:53:18,960 --> 00:53:22,320
And when you turn on the right
Hox gene in the right place,

1095
00:53:22,320 --> 00:53:24,800
you get the right body
parts in the right place.

1096
00:53:24,800 --> 00:53:27,760
But if you have the wrong
Hox gene turned on,

1097
00:53:27,760 --> 00:53:30,520
well, that's when you get
those weird mutants -

1098
00:53:30,520 --> 00:53:33,760
where you have legs growing
out of heads, and things like that.

1099
00:53:33,760 --> 00:53:36,240
But a really amazing thing
about these as well,

1100
00:53:36,240 --> 00:53:39,320
is that these don't
only exist in flies.

1101
00:53:39,320 --> 00:53:41,920
Flies have these Hox genes,
and as we pointed out

1102
00:53:41,920 --> 00:53:45,000
at the beginning, we could hardly
see any physical similarities.

1103
00:53:45,000 --> 00:53:46,960
They look totally,
totally different.

1104
00:53:46,960 --> 00:53:50,800
So, would you be surprised if I told
you that these same body plan

1105
00:53:50,800 --> 00:53:53,400
genes also operate in us?

1106
00:53:53,400 --> 00:53:55,480
We have these genes too,
even though our body

1107
00:53:55,480 --> 00:53:56,720
looks totally different.

1108
00:53:56,720 --> 00:53:58,840
But we do have a head end
and a tail end.

1109
00:53:58,840 --> 00:54:00,920
And we've got middle bits
with appendages.

1110
00:54:00,920 --> 00:54:03,240
Essentially, the genes
are actually the same.

1111
00:54:03,240 --> 00:54:06,800
So, if I was to give this to you,
Alice, this Hox gene that worked

1112
00:54:06,800 --> 00:54:10,160
for unlocking the fly head
in the fly genome.

1113
00:54:10,160 --> 00:54:12,600
But we're not looking
at a fly genome any more.

1114
00:54:12,600 --> 00:54:14,760
If we make this...
Ta-dah!

1115
00:54:14,760 --> 00:54:17,360
The human genome.
Well, that same Hox gene will work.

1116
00:54:17,360 --> 00:54:19,200
So, go on, try it
on the Cabinet. OK.

1117
00:54:19,200 --> 00:54:22,360
All right. It should
work in this top one here.

1118
00:54:22,360 --> 00:54:26,360
Yep. But this time, that Hox gene
which is very similar to the fly Hox

1119
00:54:26,360 --> 00:54:29,280
gene is unlocking the human genome.

1120
00:54:29,280 --> 00:54:31,840
And we get... Ta-dah!

1121
00:54:31,840 --> 00:54:33,880
Look, it's got Alice's hair.

1122
00:54:35,080 --> 00:54:37,200
So no matter which animals
we're looking at,

1123
00:54:37,200 --> 00:54:38,680
they all have the same genes.

1124
00:54:38,680 --> 00:54:43,680
The same genetic toolkit that lays
out the body plan that says,

1125
00:54:44,080 --> 00:54:47,800
you know, put a head here, tail end
here, legs in the middle...

1126
00:54:47,800 --> 00:54:49,920
That's arms but, you know,
you get the idea!

1127
00:54:49,920 --> 00:54:53,920
It's quite astonishing
to have delved into genetics

1128
00:54:53,920 --> 00:54:58,160
and found this similarity
between flies and humans.

1129
00:54:58,160 --> 00:54:59,920
But now looking at the DNA,

1130
00:54:59,920 --> 00:55:03,360
we've managed to find that
the fruit fly is a relative too.

1131
00:55:03,360 --> 00:55:06,120
Something that looks so different.

1132
00:55:06,120 --> 00:55:10,920
We can now add another link
on our Tree of Life.

1133
00:55:10,920 --> 00:55:14,760
Our fabulous, beautiful tree.
Beautiful! I love this.

1134
00:55:14,760 --> 00:55:16,960
But look over here, Alice,
look what we've got.

1135
00:55:16,960 --> 00:55:21,640
We have got the fruit fly -
this amazing, fruit fly.

1136
00:55:21,640 --> 00:55:24,520
Now, do you please now agree
that fruit flies are cool? No.

1137
00:55:24,520 --> 00:55:27,920
I hope so. Yes!
Thank you, some vindication.

1138
00:55:27,920 --> 00:55:31,240
So, we have this fruit fly and
if we trace back the ancestors.

1139
00:55:31,240 --> 00:55:34,520
We go up through branches here.
It's going really high.

1140
00:55:34,520 --> 00:55:36,040
Humans way over there.
Yeah.

1141
00:55:36,040 --> 00:55:40,200
So, we're actually going
to have to go to the top bar there.

1142
00:55:40,200 --> 00:55:42,440
Even with a stepladder...
We need to lower it a bit more.

1143
00:55:42,440 --> 00:55:44,240
I'm not going to be able
to reach up there.

1144
00:55:44,240 --> 00:55:46,240
What's this ancestor
going to look like?

1145
00:55:46,240 --> 00:55:48,760
Well, it looks like this.
Here's one I made earlier.

1146
00:55:48,760 --> 00:55:50,840
Was that you, Alice?
Well done.

1147
00:55:50,840 --> 00:55:52,840
I'm so good at origami.

1148
00:55:52,840 --> 00:55:56,280
So, this is not a fly,
it's not anything like a human.

1149
00:55:56,280 --> 00:55:59,800
It goes back to a really, really,
really ancient ancestor

1150
00:55:59,800 --> 00:56:02,960
that is, what? A worm?
A segmented worm. Yeah.

1151
00:56:02,960 --> 00:56:04,920
It doesn't have any appendages.

1152
00:56:04,920 --> 00:56:07,840
And it goes up here,
so we're now travelling back in time

1153
00:56:07,840 --> 00:56:10,200
about 800 million years

1154
00:56:10,200 --> 00:56:13,960
to put that segmented worm
on our Tree of Life.

1155
00:56:13,960 --> 00:56:15,560
And it's Christmas,
so you have to be nice

1156
00:56:15,560 --> 00:56:16,920
to your relatives.

1157
00:56:18,400 --> 00:56:21,680
So we found all these astonishing
connections with the rest

1158
00:56:21,680 --> 00:56:23,200
of life on Earth.

1159
00:56:23,200 --> 00:56:25,600
With all these other
groups of animals,

1160
00:56:25,600 --> 00:56:30,560
we found connections between humans
and bats and horses and armadillos.

1161
00:56:31,320 --> 00:56:34,320
And we can place these ancestors
then as well on the tree.

1162
00:56:34,320 --> 00:56:36,680
We're working back through time.

1163
00:56:36,680 --> 00:56:39,640
And we can place them
very precisely.

1164
00:56:39,640 --> 00:56:42,680
We know where they should go,
using both the fossil record

1165
00:56:42,680 --> 00:56:45,760
and the molecular clock
to place them in time.

1166
00:56:45,760 --> 00:56:49,280
So, we can reconstruct our big
family tree then and we can go back

1167
00:56:49,280 --> 00:56:51,400
and back and back in time.

1168
00:56:51,400 --> 00:56:56,280
If you look right up there -
you can see a little light.

1169
00:56:56,280 --> 00:56:59,840
So, where our family tree is
disappearing into the ceiling,

1170
00:56:59,840 --> 00:57:03,680
that light represents the common
ancestor of all life on Earth.

1171
00:57:03,680 --> 00:57:07,640
And that was a single-celled
organism four billion years ago.

1172
00:57:07,640 --> 00:57:11,840
And its descendants today are
mostly single-celled organisms.

1173
00:57:11,840 --> 00:57:14,840
They outnumber all of
as multicellular creatures.

1174
00:57:14,840 --> 00:57:17,480
But its descendants also
include plants and fungi,

1175
00:57:17,480 --> 00:57:19,880
and then, all of the animals

1176
00:57:19,880 --> 00:57:22,480
that we've been looking at.
All life on Earth.

1177
00:57:22,480 --> 00:57:23,720
Every single thing.

1178
00:57:23,720 --> 00:57:26,920
So, since that last
universal common ancestor,

1179
00:57:26,920 --> 00:57:28,840
life has been unfurling

1180
00:57:28,840 --> 00:57:31,840
and evolving in many,
many directions.

1181
00:57:31,840 --> 00:57:34,360
Just some of which we've shown here.

1182
00:57:34,360 --> 00:57:39,160
And only one of those
pathways leads to us.

1183
00:57:39,160 --> 00:57:44,200
And we come all the way down
to humans at the bottom here.

1184
00:57:44,200 --> 00:57:48,320
This puts us in our place.
It shows us where we come from.

1185
00:57:48,320 --> 00:57:52,480
And we are not
the pinnacle of evolution.

1186
00:57:52,480 --> 00:57:57,080
But we're in a fantastic place,
I think, because we're not separate

1187
00:57:57,080 --> 00:58:00,840
from nature,
we're very much part of it.

1188
00:58:00,840 --> 00:58:04,880
We are just one species
amongst billions.

1189
00:58:32,000 --> 00:58:36,600
So, just one of these little
leaves then represents us,

1190
00:58:36,600 --> 00:58:38,360
represents our species.

1191
00:58:38,360 --> 00:58:42,200
And in the next lecture,
we'll be focusing in on humans

1192
00:58:42,200 --> 00:58:46,000
and finding out how we evolved
as a very special group of apes.

1193
00:58:46,000 --> 00:58:48,600
We'll be looking at our
closest living relatives,

1194
00:58:48,600 --> 00:58:52,360
the chimpanzees and the gorillas,
and finding out about

1195
00:58:52,360 --> 00:58:54,960
the differences
that make us who we are.

1196
00:58:54,960 --> 00:58:57,760
But for tonight -
it's goodnight from me.

1197
00:58:57,760 --> 00:58:59,160
And it's goodnight from her!