In here I have some of your cousins.
They are tiny, bioluminescent single-celled organisms.
And when I shake them, they glow.
They spend their time floating around and glowing.
You spend your time going to school and seeing your friends.
And yet we are related.
We're both part of the great Tree of Life on this planet.
But where do we fit into this Tree of Life?
Welcome to the Royal Institution Christmas Lectures.
I'm Professor Alice Roberts and over the course of these three
lectures, we are going to find out who we really are.
And we're going to do that by comparing ourselves
with each other, with earlier types of humans,
and even with other animals as well.
And we will be looking for similarities and differences
between us until we can really point out what is unique about us
as a species and what is unique about each one of us as individuals.
So, we can trace back our evolutionary line until we get
to a common ancestor of everything alive today.
And that common ancestor was a single cell,
a single-celled organism perhaps in a deep sea vent,
the bottom of the oceans, or maybe in a warm, shallow pond.
And that ancestor lived four billion years ago.
Now, that's a huge number to think about,
a massive number to try to conceive, so we've got a bit of help.
We are going to illustrate just how big that is.
This is my friend Fran, and this is a ribbon
which represents four billion years of life on Earth.
And our time on the planet is represented
by just that tiny little black strip at the end there.
So, that tiny black strip is actually 300,000 years of modern humans,
Homo sapiens, our species being alive on Earth.
And then as we go back in time,
we're going back through mammal ancestors.
And back and back and back. It's going to take far too long.
Fran, we need some more power, we need some help here.
Here is Mike with a leaf blower. Yes!
Back through mammal ancestors, those are reptiles.
Multicellular.
The yellow's all single celled animals.
And you're helping us go back in time,
ribbons of time are descending on you.
All single cells are still going.
It's such a huge amount of time.
And there we go, right back to the beginning
and the end of the ribbon there.
Give us back our time, you're stealing our time.
So that's four billion years of life on Earth,
but somewhere in amongst all of that is our story,
our thread.
How do we find it?
How do we go about tracking back our own story through time?
We use the science of life.
We use biology.
So we can start to look for similarities and differences
between different living animals.
And the first living animal I want to introduce you to this evening -
and this is the first time we've had a horse in the Royal Institution -
is Leo. Leo is a beautiful horse.
He's come in with Caroline and Charles from Windsor.
And Leo is going to show us just how similar we are to horses.
Now, I'm an anatomist, so I am interested in him
on the outside. He's beautiful.
He has a beautiful mane, beautiful coat, beautiful tail.
If we turn him round, though, Caroline,
we can reveal some of Leo's insides.
And now you can see the horse skeleton painted
on the outside of him.
Now, he looks so different from us, doesn't he?
He's a very, very different sort of animal.
He's a mammal, so he must have some things in common with us.
And we can get at some of those similarities by looking
at anatomy like this.
So, we are going to need a human to compare him with.
Here's someone we prepared earlier.
This is Adam, our living human skeleton.
Adam, can I position you over here?
Thank you very much.
So, Adam has his skeleton painted on his outside as well.
And what I want to try to do now is to find some
of these similarities between humans and horses,
so can I have a volunteer from the audience?
Yes, do you want to come down and have a go?
What's your name?
So, if you stand over here.
Boyan. B-O-Y-A-N.
Boyan. Yes.
What I want you to do...
Leo's just having a little look at you. He's a very friendly horse.
Do you want to turn around and say hello to him,
so that you've met each other properly?
So, what I want you to do is to look at the bones
in the horse's leg and then to look at Adam and see
if you can find the same ones.
So, if I just stand you back here. Is that all right?
And, Adam, if we just move you a little bit this way.
That's brilliant. Now, I'm just going to spin Adam round,
if that's all right, Adam.
The first bone I want you to find, Boyan, is this one here,
which is a scapula, or shoulder blade.
Can you find the shoulder blade in the horse?
Where do you think that's going to be?
It's still going to be quite triangular.
A bit higher, a bit higher... What about this one here?
Well, it is much bigger, so... It is much bigger.
He is much bigger, though, isn't he?
So that's the scapula on the horse, and it is equivalent
to the scapula in the human.
And it's what attaches the horse's front leg
onto its body, onto its chest.
And it's doing exactly the same thing in Adam,
it's attaching the upper limb, the arm.
Adam, if I spin you back around again.
Now we can start to go down the limb.
So, you found the scapula. Can you find the equivalent
of this bone, the humerus, in the horse?
Well done. And then can you find the equivalent of these two bones?
This is the radius and the ulna in the human.
Can you find something which might be equivalent to those?
Here. A little bit higher, look.
Can you see the horse's elbow? The equivalent there? Yes. Yeah.
And then we've got a collection of bones in the wrist here.
Adam, can you hold your hand out like that so we can see?
So, in your wrist, you have got this little collection
of bones called carpal bones.
Can you see a little cluster of bones which might be equivalent
to those bones there? Can you see there?
Yeah. So, that's its wrist.
That's the equivalent to the horse's wrist.
Then you've got a long bone which is this bone in the palm here.
But you can see it down there on the horse.
And then you should have three bones,
because fingers have each got three bones.
If you look at your own fingers, you will see you have got three bones
in your fingers and you see one, two, three bones there.
Can you see three bones getting down towards Leo's foot?
Oh, yes, I can see one, two, three.
Brilliant. So, we have got the same pattern of bones -
one, two, many - in the human and the horse.
You were great. Thank you very much, Boyan. Thank you. Thank you.
APPLAUSE
Now, I'm going to keep Adam and Leo here a little while longer
while we introduce you to some other guests,
and we're going to carry on looking for these similarities.
So, this is Brutus. Andy, if I stick you there.
Yeah. Isn't he wonderful?
What is he? Armadillo.
He's an armadillo. What type of armadillo is he?
He is a large hairy armadillo.
And he is large and hairy. Armadillos are mammals as well.
They're wonderful creatures. Is he all right? Yeah, he's fine.
He's got bony plates on his skull and over his back here which helps
protect him from predators, and also he can crawl inside thorn bushes
to run away from predators and not get scratched.
And he has got some other amazing adaptations,
including these fantastic paws which are for digging.
So, he's a digging mammal, he lives in a burrow,
he digs out grubs and ants and termites to eat.
There we go, we can see his lovely paws there.
And we can bring in a skeleton of an armadillo
to have a look in a bit more detail.
Now, in this skeleton of an armadillo, you can see
that we've got the same bones.
We have quite a scapula, or shoulder blade, up here.
Then there is a humerus.
Then there is a radius and an ulna again, just like in Adam.
Then there are carpal bones.
Then there are these very chunky, robust fingers
which are absolutely great for digging,
for pushing all of that soil out of the way.
Is he OK to stay with us for a minute, Andy?
Yeah, yeah. Thank you.
I want to introduce you to another guest now.
This is a tiny little bat.
This is Merlin the serotine,
one of the largest bats in Britain.
Could you show him to the front row over there, perhaps?
So, a tiny little bat there.
So, again, this is a mammal, so we will find some similarities,
even though it's such a different sort of animal.
Can I bring you back over here and we'll just have a look at his wings?
Now, is he all right to show us his wings? He's quite nervous.
Is he waking up? You might be able to stretch
his wing out and have a look. Might be able to open it.
So, we can see his wing there and you can see the way
that his wing is made of skin stretched over a bony framework.
I think we can let him put his wing away.
Yes. And we can look at a bat's skeleton alongside him.
And when we bring out the bat's skeleton,
we start to see here another similarity,
another pattern of similarity with all of these other animals
that we've looked at. So, looking at this bat skeleton,
you've got a tiny little scapula, a tiny little shoulder blade,
attaching the wing to the thorax, to the chest.
Then a humerus.
Then you have got those forearm bones and wrist bones,
just like in the human.
And then the bones that actually form the structure of the wing
are the bat's fingers.
So, again, they've got one, two, three bones in each of those struts
that are supporting the wing.
So, we are finding some amazing similarities between animals
that look very, very different on the surface.
Now, before you do this, I just want to say,
please can you do it very quietly?
We're going to give a very gentle round of applause to all of our
animal menagerie and their owners.
Thank you. Thank you.
So, how amazing to find all those hidden similarities
between the horse and the human and the armadillo and the bat.
What's even more astounding is that once you start looking
for these similarities, you find them absolutely everywhere,
from the anatomy that we can see with our eyes, like the skeleton,
right down to the level of molecules inside our cells.
So, to take us down to that level now, and to look at DNA
in ourselves, I want to introduce you to somebody very special
from Trinity College, Dublin, and The Genetics Society,
Professor Aoife McLysaght.
Thank you.
So, in order to do what Alice says and to really get
down to a molecular level, the first thing we have to do is imagine
this theatre as a cell.
Imagine we're inside a cell.
So, if we get some balloons and just gently bounce them
around like they're floating inside a cell.
Yeah, so we can see different things.
Like, we have mitochondria,
which are generating the energy in the cell.
We have lysosomes, which are the waste management plant in the cell.
And lots of other bits and pieces.
But, Alice, the thing that I'm really interested in
is this big one here.
So, catch! No! It's like a wrecking ball!
Yes.
So, this is the special one.
So, you've got lots of other little balloons...
Got lots of other little balloons, but there's only one of these.
This is the nucleus of the cell, and this contains something
very important and something that I am especially interested
in as a geneticist, but we can't see it yet.
And, Alice, I'd like you to do the honours, please.
So, Aoife has just handed me a very, very sharp instrument.
Yeah, I was carrying that in my pocket until now,
so that was a bit risky. What's inside it?
Well, we will see, let's see. So, we will count from three.
Three, two, one...
Oh!
So what we have here...is DNA.
So, you've probably heard of DNA before,
and maybe you know that DNA is really, really important for making
you what you are. And look at this, we have got two colours.
We have got yellow and white.
So, half of it is yellow, half of it's white.
So, this is half from your mum and half from your dad.
And if we were to... We have 23 pairs of chromosomes.
In the human genome, 23 pairs.
And if we were to stretch these out end to end,
they would reach to two metres long, which is basically this length
I'm carrying here.
But I don't mean two metres
on the scale of this whole theatre as a cell.
I mean two metres in real life,
two metres inside the cells of your body.
So, if we lined up all of the DNA in our chromosomes,
in a single cell, it would be two metres long? Yes.
But the thing is, it's extremely thin,
like, less than one of the threads of this,
and it's all scrunched up really, really small.
And it is packed into a tiny space, just like that.
So, DNA is really, really long.
And so that is a lot of DNA.
It is actually three billion letters of the DNA that you have as a human.
I presume you're all human, yeah? I didn't check.
But it's actually quite simple.
It's only got four parts to it. So, the four parts,
we symbolise them with the letters A, C, T and G.
So, just four parts to DNA.
And if you look at this bit here, so we've made the letters big here,
but you can see there's a sequence of letters.
We've got T-A-C-C-A-G-A-T-T-C-G.
Right? You can read that like I can read that?
That's a DNA sequence. That's all we mean when we talk
about a DNA sequence. It's a sequence of letters.
And because you're all human, you've got a human DNA sequence,
and a horse has a horse DNA sequence, and an armadillo
has an armadillo DNA sequence.
And we can actually compare them.
And so look at this.
This is a real piece of DNA sequence.
This is from the human genome, so you all have this in you.
This is actually a little bit of a gene.
And this gene is involved in the development of your front limb.
So, for you, that's an arm, for the horse, it's a leg.
And if we look at this little bit in the sequence,
we can read it across, it's easy.
T-C-C-T-A-T-A-G-G, etc.
Easy to read DNA sequences.
And then you've got the armadillo, the bat and the horse.
And if you look at this, you can see really quickly
that the beginning is the same in all of them,
so they all have T-C-C-T-A,
But then we've got one difference here.
So, this is something that happens in humans but not in the others.
We've got a T in human, but we've got a C everywhere else.
And if we look here, we've got an A in horse
and a G everywhere else.
So, we all have similar genes, a bit like Alice showed you,
you have the same bones in the different animals,
but they're a slightly different shape,
but they're still recognisably the same.
So, they're slightly different but the same,
and we see that with the genes.
I think it's just fascinating that we've got these similarities
when we look at anatomy, when we look at skeletons,
and it's there as well at the level of the DNA sequences.
At the DNA level, yeah. That's brilliant. Thank you, Aoife.
Yes. I'll see you later, Alice. See you later.
Now, biologists started noticing these differences
back in the 19th century.
Not in DNA sequences, because that science was yet to come,
but they could look at skeletons.
And there was one biologist in particular who wrote about this,
and his name was Richard Owen,
and I've got a copy of his book here.
And this book is nearly 170 years old.
It was published in 1849, and it's called On The Nature Of The Limbs.
So, he looked at the bones of a horse, and actually
there's a really weird similarity here when I compare
that with the bones of a bat and with the bones of...
He used a mole. We used an armadillo.
And what Richard Owen said was there's something deeply
strange here, deeply weird, because why do all these animals
look the same under the skin?
If their structure was just about what they did,
just about their function, you wouldn't expect any underlying
similarity between something that flies
and something that runs fast and something that digs.
So, there's something else going on.
And it was a great puzzle to him and he didn't crack it,
he didn't work it out.
He said, there's some kind of abstract idea of mammalness,
and all of these animals are just variations on a theme.
Ten years later, Charles Darwin published his book,
On The Origin Of Species, and he nailed it.
He said there is something really important that links
these animals together and explains
all of these underlying similarities.
And it's not abstract at all.
It's a real thing.
And what it is is a shared ancestor.
So, when you're looking at the armadillo and the horse
and the human and the bat, the reason that they've got
those similarities is that if we trace their family trees back
and back and back and back, we get to a point where
there's a shared ancestor, an ancient mammal ancestor
that had that pattern of bones in its limb
and all of these different organisms, including us,
have inherited that pattern from it.
And we've got an idea of what that mammal ancestor
actually looked like, and it is this.
And she is called Juramaia, which means Jurassic mother.
She was around at the time of the dinosaurs and she lived
about 170 million years ago.
So, we've inherited the pattern of bones in our limbs
from ancient ancestors like this.
We've also, some of us, inherited something else
from ancient mammal ancestors.
I wonder if anybody in the audience can wiggle their ears?
Something very important here is that you have to make sure
you're really wiggling your ears and not just moving your whole scalp.
You've got a muscle in the front of your forehead here,
called frontalis, and a muscle at the back of your head,
called occipitalis.
And I can shift my whole scalp backwards and forwards.
It's a really important life skill.
It's...taken me some years to perfect.
But what I can't do is wiggle my ears independently of that.
So I think there were some...
Were there any ear wiggling people here?
So you think you can wiggle your ears.
What's your name? Matt. Matt.
Wiggle your ears. I think he is...
That's a pretty good ear wiggling.
Well done. Well done, Matt.
So, Matt is able to voluntarily use little muscles around the ear
that all of us have, but only some of us seem able to use them still.
And this is left over from ancient mammal ancestors
who had much bigger ears than us.
So, there are these interesting remnants of ancient ancestors in us,
and we can look at the fossil record and we can find really ancient
mammals like that Juramaia, and we can date them,
because we can date the rocks that they're found in.
But, actually, there's another, completely different independent way
of dating a common ancestor of mammals,
and that's by looking at genetics.
Did you say genetics?
I might have done. That's my bit.
So, yeah, it's true that we can look at DNA sequences.
As you just saw, we looked at some DNA sequences and we saw
a few differences, right?
And we can look at this and we can think about how those differences
accumulate and think about it with respect to time.
And this is because every time you have a new generation,
the DNA has to get copied to be passed on that new generation.
And every time you copy DNA, there's just a chance
that there's mistake made.
So, a mistake is a mutation, when you're talking about DNA.
And so sometimes those mutations have some big effect and maybe
there's something we can see on the outside.
And sometimes the mutations really do nothing and so they're
just gradually, over time, getting more and more changes,
which means that when we look at the number of changes,
we can actually figure out the amount of time.
But I am going to explain this better with a little demo,
and for this, I'm going to need two volunteers.
Wow, this is brilliant.
OK, so, you there in the lovely Christmas jumper.
You come down. And, yes, another Christmas jumper.
Is that your little dachshund? Lovely.
OK, so, what is your name? Dylan.
And your name?
OK. Can you go over there with Alice?
And Dylan, you just stand there for a moment.
So, what we have here is we have two DNA sequences
and everybody can see at this point they're the same.
So, they're lined up like they were printed on the page earlier.
So you can pair up and down.
So we have got T-G-C-G-A-C-A...
That's a DNA sequence.
And these are actually identical
because they have a very recent common ancestor.
So that's...they're sharing ancestors very, very recently.
What we're going to see what happens when species get separated.
So, I'm going to be this species on the top,
and, Alice, maybe you could take the bottom one. Yeah. So, Alison and I
at the moment are identical to each other.
But we get separated. We have our reasons, I suppose,
we've gone astray, but look, there's this river in between us
and we can't go back now.
So, now we are separate and our lineages can't mix any more.
So, now, when we have generations on this side in the Aoife lineage,
those aren't going to get mixed, those changes aren't going to get
mixed up with what happens over on Alice's side of the river.
So, things are happening independently
on the two sides of the river.
So, what we're going to get you to do is we're going to imagine
there is new generations happening and there is mutations happening.
So, what I am going to get you to do is I'm going to ask you to flick
one of these, but not just yet
because we're going to count together.
And the same thing for you over there.
So, we're going to count with the audience together
and we're going to count down from three each time and I want
you to just randomly pick one of them and flip it over. OK?
So, we count together. Three, two, one.
Go. Flip it. Do one. OK, brilliant.
And again. Three, two, one.
Choose another one. Beautiful. And one more. Brilliant.
Three, two, one.
Lovely. Brilliant. We have got three random mutations over here.
Thank you so much. Thank you so much. OK, so thank you so much.
You can sit down again. Thank you so much, both of you. Thank you.
We'll put these back here now.
Put these back here now so we can compare them again
and let's just see what happened.
So, Alison and I have been separated for three generations
and our descendants now are comparing their DNA.
And so even though Alice and I started out exactly the same,
now our descendants are slightly different.
So, let's see if we can find some changes.
So, like, here we've got a G and then a C.
That is one change. In another change.
Two, three, four.
I've got to line them up, Aoife.
Yes, I know. You're helping me, thank you so much. Five.
Six differences.
So, we had two sides of the river,
so it's three differences on each side of the river.
And in our case, we know that there was one change happening
per generation, so we could say even if we didn't know how much time
had elapsed, we could count the differences in the DNA sequences,
and just from that on its own, without having any other
information, we could say that these two species had a common
ancestor three generations ago.
So, this idea is called a molecular clock.
So, we can use the molecule, look at the changes in the DNA
molecule and use it to count time, to measure time.
So, you could do that for two different animals...
Like, a human and a bat, could you do it for a human and a bat? Yes.
So, we wouldn't do it for something as small as this sequence.
We'd do it for much, much more.
So, for a human and a bat, we can compare thousands
and thousands and thousands of genes, and when we do that,
we can count up the differences and estimate the time.
And we say we get to 96 million years ago, there was a common
ancestor between humans and bats.
That's quite a long time, isn't it?
And what about for all placental mammals, so mammals like us?
Yes, so if we add in more species and we look at deeper divergences,
we get back to about 170 million years ago.
So, this is amazing, because that's a date based purely
on the genetics of living organisms... Yes.
Working out how fast they change over time and saying,
"well, we must have had a common ancestor with all those other
"mammals going back 170 million years ago" and then looking at the fossil
record, we find these really early mammals 170 million years ago.
So, we have got two completely different branches of science
agreeing with each other. Totally in harmony.
And it's time to put our ancient mammal ancestor
onto the Tree of Life.
So, we have this beautiful tree, Alice. Aw, this is our tree.
This is how we reconstruct all of those similarities and differences.
It tells us how related we are
to different organisms on the planet today.
And it's just like a family tree, so, you know, you are connected
to your siblings through your parents and then to your cousins
through your grandparents, except we're doing it for species.
So, we have, look, we've got the human here
and the animals we've just been looking at, in fact...
Yeah, the bat, the horse, the armadillo. Yeah, yeah, yeah. So...
So, a common ancestor of all of those, then,
going back 170 million years ago, we've already met Juramaia,
and here she is in origami form.
And we're going to stick her on.
So, we'll add her to our Tree of Life.
So, this is the branch, then, that's the last meeting point
of all of these different lineages.
After that, they start going their separate ways. Yeah, yeah.
So, we're gradually accumulating more cousins, more ancestors.
Now we're going to go in search of some slightly stranger cousins
Thank you. So, this, ladies and gentlemen, is an egg.
It is not a hen's egg.
This one actually came from an emu.
And the egg is an amazing biological phenomenon.
If you think about it, it's got to support the developing embryo
inside it and give it everything it needs
before that chick eventually breaks out of the egg
and starts to live on its own outside of the egg.
So, I am going to... They've given me a teaspoon.
I can't believe this. I don't think this is going to cut it.
I'm going to need something
a bit more effective than a teaspoon, I think.
So, this is Douglas, who's the head of eggs
from the Natural History Museum.
Indeed. And what have you got, an Army knife?
Yeah. Lovely. So, what shall I...? Shall I hold the egg there?
If you could just hold it gently there, that would be great.
And... Just going to put that in there.
You've done this before, haven't you, Douglas? I have.
How many times have you done it before?
I have done this 18 years running.
18 years of opening eggs. There you go.
And looking inside them. So here we go.
Just gently get that egg out.
It's like a cookery show.
Thank you, Douglas. So, Joe, come and have a look.
There's an enormous yolk inside that emu egg,
as you might have expected. You've seen your yolks before.
What the yolk is is a bag of nutrients, a bag of food
for the developing emu embryo, if this egg had ever been fertilised.
So, that's full of lovely, rich nutrients.
And there are other membranes that develop inside the egg
if an embryo grows in there.
So, there's a membrane that lies up against the inner surface
of the egg shell and gases can actually permeate
through the egg shell, so oxygen can get in,
carbon dioxide can get out.
So, the developing embryo is exchanging oxygen and carbon
dioxide with the atmosphere.
And there's another membrane that forms a bag
around the developing embryo itself,
and that is called the amniotic membrane.
So, the embryo develops inside this bag of fluid,
and that bag of fluid is very important, because it
protects the embryo from shocks and it also means that the embryo
can move its little developing limbs and those limbs only form properly
if it can do that.
So, we're now going to meet some...
Well, no longer embryos, but chicks that have got too big
for their amniotic sacs and too big for their eggshells
and are actually hatching out.
So, these are quails and we have timed it
so that they are hatching out today.
We've been incubating these in the Royal Institution
for 17 days, but they're just popping out of their eggshells,
so they've just reached the end of their gestation,
and out they come.
And then this, of course, is another type of animal that lays eggs.
So, over here we have got a reptile.
Does anybody recognise what that reptile is? Yeah?
A bearded lizard. Yeah, it's a bearded dragon, yeah,
it's a type of lizard, a bearded dragon.
He's absolutely wonderful.
So, these reptiles lay eggs as well, and...
Their eggs are a little bit different.
Their eggs are leathery on the outside, so their shells
But they do the same thing - they let the oxygen in,
and the carbon dioxide out.
Inside, you've got all the same life support systems that the quails
had inside their eggs before they actually hatched out.
But now, I want to introduce you to somebody who hasn't hatched yet.
So, we'll say goodbye to our bearded dragon and our quails.
And, we'll say hello to somebody else.
Hi, Rosie. Hello.
Rosie, you are going to have a baby. Yes.
And, Rosie is going to let us have a look at her baby.
So, how pregnant are you? How far through your pregnancy are you?
23 weeks, due in April.
Wonderful. So, that's just over halfway.
Human babies are in their mother's wombs for 40 weeks,
on average, about nine months.
If you hop up there, Rosie.
This is Jill, who is a sonographer, so she does ultrasound.
Using ultrasound, we can actually have a look inside Rosie's tummy,
inside her belly, and have a look at her baby
which is developing inside the womb.
Ultrasound just uses sound waves, and those sound waves will pass
in and they'll bounce back.
So, it's a little bit like sonar,
a little like submarines using sonar.
Those sound waves bounce back and then we can start to see anatomy
or we can see the baby.
This is amazing.
So, Jill, you can see the baby's head there, can't you?
At the moment, we're looking at this baby in two dimensions,
so, as though we're looking right through the head.
But you can do it in 3D as well, can't you?
I'm just trying. I think the baby's moved into a difficult position now.
And we call this 4D, because it's 3D plus time,
so you're actually seeing this baby moving inside Rosie's womb.
We're just having a little look to see if we can see the baby's
face peeking out.
It's not behaving very well, but I do have one that we got earlier.
We can see the face.
How do you feel, Rosie, seeing your baby in there?
Quite emotional, yeah. It's amazing!
It's utterly extraordinary to be able to look at your little baby.
You can see the nose, you can see a mouth,
a hand up by her face.
She looks very much like my son. Does she?
When he was a newborn, yeah.
Yeah, yeah. This is absolutely wonderful.
We can see around this baby that there's space,
but in fact, this is fluid-filled space.
We can see that the baby is inside an amniotic sac.
So, there's a membrane around it and then this blackness
is the fluid around the baby.
So, just like the developing chick and the developing reptile
inside its egg, a human baby starts growing
inside a fluid-filled bag - the amniotic sac.
But there's something else as well
that we can see here that's really important. I think it's this.
That's the placenta, isn't it, Jill? It is, yeah.
So, this big area of grey here is an organ that is grown
specially inside Rosie to support her developing baby.
So, this is the life-support system for human babies in the womb.
And the placenta is an astonishing organ.
It's allowing Rosie's baby to get oxygen and nutrients from her blood.
And it's allowing that baby to get rid of things
like carbon dioxide as well.
So, that baby is being supported while it's inside the womb,
and it's exchanging gases
and other sorts of compounds
with Rosie's blood.
That is amazing.
Thank you very much.
And let's say thank you again to Rosie and Jill. Thank you.
It's so amazing, and what an amazing privilege to see that tiny person
a few months before they actually emerge into the world.
And who knows? In a few more years' time, maybe
they'll be here watching Christmas lectures.
I think they'll have to come back, won't they?
They've been to the Christmas lectures, they'll definitely
have to come back to them.
The placenta is the most amazing organ.
It's the doing all that important work for that developing baby.
But it does something else and that's really important, as well.
Because that developing baby is a genetically distinct individual.
That baby is not the same as his or her mum.
That baby is a new person.
So, usually, your immune system would seek out anything
that wasn't you and get rid of it.
That's what your immune system does, doesn't it? It protects you.
So, there has to be a barrier between that developing baby
and the mum's immune system,
and the placenta is a really important part of that.
And then - a fantastic clue as to how it does
that comes from genetics.
Did you say genetics? I said it again.
So, there's actually something really special about placenta.
And we can see that in something really special about the genetics
of the placenta.
As Alice said, it's a barrier in your body.
It's a barrier between the maternal and the foetal side.
You actually have lots of other places in your body
where you have barriers - the lining of your lungs,
the lining of your intestine, the lining of your blood vessels.
Those barriers look a bit like this.
So, these are cells, obviously.
And this is a layer of cells.
So, if you look at this -
we have this layer of cells and that's pretty good.
It's good enough for most of those parts of your body.
But you can also see that there are lots of holes there, there are gaps.
Even if it's a nice, tightly packed group of cells,
there are gaps that can get through there.
So, things can still get through. So, the placenta is a bit different.
Alice, maybe you could help me?
Because in the placenta, the cells, the neighbouring
cells, merge together.
And it doesn't happen like this, by the way,
because the way it happens in a placenta is that the cells,
the neighbouring cells, the membranes just join
together like this. It's not...
This isn't a cooking show!
This is the Christmas lectures, Alice.
But the neighbouring cells join together.
And this doesn't just happen randomly.
There's actually a special gene
and it makes a protein called syncytin
that makes this happen.
The neighbouring cells, they join together and you get
something that looks a bit more like a pancake.
When we look at the sequence of these genes and try to see
what else they look like anywhere else,
we find that they're just like genes that make the outer
coating of viruses.
So, these genes are very, very similar when we look
at the sequence.
And it makes sense, because when a virus causes
infection, what happens is the virus comes along and it merges
into the cell that it's infecting.
And what we see in the placenta is that the neighbouring cells
are merging together.
So, it actually makes sense that the function is very,
very similar in the virus and here recycled into the placenta.
So, how does a virus gene get into...
I mean, we're talking about human DNA? Yes.
Why is there a virus gene in human DNA?
Well, it's a bit weird, isn't it?
But actually, in our ancestors, they would have had viral infections
all the time, like I'm sure everybody here
has had a virus at some point.
When you get a viral infection, it actually enters into the cell
and releases its DNA into the cell.
Sometimes when it does that, the DNA actually integrates
into the DNA of the person that's being infected.
If you can imagine some ancient mammalian ancestors,
they had lots of viral infections every now and again -
the virus, instead of just causing an infection and then the infection
ending, the DNA hung around.
This is actually about 8%
of what we call the human genome.
Looks like virus DNA. So that tells you how many infections
there have been over the years as well.
That's a huge proportion, as well. A huge proportion, yeah.
So, presumably, that viral DNA then gets inserted into our DNA.
We've dismantled it a bit, we've taken bits out of it
to stop it being pathological. Yes. To stop it hurting us.
But then what happened is the evolution, kind of,
stumbled across this deactivated virus gene,
and suddenly, it became useful again.
So it's like the scrap yard.
There's all these pieces that are left over,
and they still kind of work a bit but they're not quite working -
they're a bit broken. So, for the virus,
this gene is helping the virus
enter the cell by merging into its membrane.
And now in the placenta,
it's helping the neighbouring cells merge into each other.
So, it's kind of recycling the same function.
It's a brilliant bit of recycling, isn't it? Fabulous.
So, this shows us an important clue as to how the placenta came
about in our ancient mammal ancestors.
But still, what we've discovered is a connection going back even
further than that with those egg-laying relatives of ours.
Because of that amniotic membrane around the developing embryo
in both humans and in reptiles and birds as well.
So, now we can put another relative, another ancestor in fact,
on the Tree of Life. It's beautiful.
This time, the ancestor that we've got is a reptile.
So this is a reptile that was an egg-laying reptile.
It's a mammal-like reptile and it lived about 300 million years ago.
So, we're going higher. Yeah.
So there is Juramaia, we're having to go back here.
We've got the egg-laying things over here,
so we've got a chicken and maybe a crocodile and a lizard.
So we follow the thread up and we get to...
Will I help you? I can help. Thank you. There we go.
So there is an ancient mammal-like reptile,
300 million years ago on the Tree of Life.
So as we're going up, we're just going further back in time.
Yeah. And discovering more cousins and more ancestors -
and egg-laying ancestors this time.
So then we've got an answer to the question,
which came first, the chicken or the egg? Oh.
Biologists know that eggs came first.
This egg-laying reptile was there ages before anything
like a chicken evolved. I know, I know! Oh, really?
Just wanted to spoil the joke!
So now I want to look at these creatures over here.
So here, we've got some origami fish.
So I want to find out our connection with fish.
I'm just going to disappear out here,
but you might be able to see me on the other side.
Hello.
In this tank here, we've got a type of shark.
So, this is a type of dogfish.
And this is another relative of ours.
So, another cousin on the Tree of Life.
And, you know, you might have been persuaded that the horse
was a relative of ours, had the same bones in its legs.
And, the armadillo and the bat. Am I starting to stretch things now?
Hmm. Maybe a little, but there are still similarities here.
There are certainly differences.
This fish has got fins rather than limbs.
It lives in water - it can extract oxygen
from the water, whereas I breathe air.
But that fish has got a skull and I've got a skull.
And it's got a spine.
So we are both vertebrates.
It is getting more tricky to see similarities, though.
But, if we go back to an earlier stage of development,
there are many more similarities to see.
So, what I want to do now is introduce you
to a 3D-printed human embryo.
So, this is a 3D print of a human embryo
at around four weeks of gestation.
And this is about the size you were then.
And you're barely the size of a fingernail clipping.
But there are some important clues here
if we look at the anatomy of an early embryo.
We're not going to see them in this tiny little 3D print.
So I'm going to give you that without sneezing.
Thank you.
What we've done is we've scaled up the embryo to about 800 times
its actual size at the end of the fourth week of development.
And I've got two embryos here.
One of them's a fish, one of them is a human.
Which one do you think is which?
Which one do you think is a human, and which one you think is a fish?
That one's a human. That one's a fish. Yeah, you're right!
I mean, look how similar they are.
It is really shocking how similar the fish and the human embryo
are at this particular stage of development.
They've both got a head, they've both got a developing eye,
you can just see up there.
They've both got tails, so human embryos have tails.
And then later on, they disappear, so I don't think any
of you have got tails particularly.
You'll have a coccyx bone but not an actual tail.
But there are these strange, strange things in the neck.
So, this is the human embryo.
You can see that the human embryo's got odd bars,
or ridges, in its neck and the fish embryo has as well.
Now, in the fish, those ridges are going to develop into something
which you can see in the adults.
And I don't know whether we'll be able to see it.
Can we just about see? Yes, we can.
Can you see the gills opening and closing on the side
of our dogfish's neck?
So, you're looking down towards the base where the fin is joining,
and you can just see those gills opening and closing.
So that's what those developed into in the fish.
And then you go - what?
Why are there things in the human embryo
that look as though they're going to develop into gills?
Anyone in the room got gills?
Anyone at all got gills?
You haven't got gills! You can't breathe underwater!
I'd love to have gills,
I'd love to be able to be underwater. But,
I'd to give up some of the anatomy that I have got
that's really, really useful to me.
Because something very interesting happens with these gill arches
in the embryo.
Some structures in embryology, in embryonic development,
appear and then disappear. That's what happened to the tail.
So the tail appears and then it just disappears.
Not so with these early gill arches.
Inside those gill arches, there are all sorts of bits
of anatomy that proved to be useful.
Inside these really, really early structures,
we've already got little arteries growing out.
Which, if you were going to be a fish,
would supply your gills with deoxygenated blood,
ready to pick up oxygen from the water.
Inside these developing gill arches, are developing muscles,
which, if you were going to be a fish, would open
and close your gills like our dogfish.
Inside these bars, there are also little bits
of cartilage which, again, if you were going to be a fish,
would support your gills.
But you're not going to be a fish.
And what happens instead is that all of those structures form
and then they get recycled into other things.
And they get recycled into all sorts of structures
in our heads and in our necks.
One of the things they get recycled into is this.
Now, this is one of my favourite bones.
It's a strange little bone.
It is U-shaped, as you can see.
And it's called the hyoid bone.
This little bone sits up here in your neck.
It's quite difficult to feel it, and don't try too hard
because it's uncomfortable. But that's where it is.
It anchors the muscles that form the floor of your mouth.
And then, it sits there as something for your voice box to hang from.
So what I've got here is a much bigger model of that.
And here's the hyoid, and then underneath it
are the cartilages of your larynx, or your voice box.
So, that's what I'm using to speak to you right now.
But those cartilages do another important thing,
as well as providing the mechanism of speech,
they also keep the airway open.
Something very important that they're doing.
These cartilages and that bone come the gill arches in the embryo.
So we can add the fish to our Tree of Life.
We can bring it in as a cousin, and we can actually add
an ancient fish ancestor.
There is Juramaia, our mammal ancestor.
There's our reptile.
And the fish, then.
So, we've got modern fish over there.
If we trace that line up and across, then that's going to join up
with the line that come up from humans.
So, we're finding this fish ancestor,
500 million years ago we've travelled now, back in time.
But now... I know there's someone
who's itching to introduce you to yet another cousin,
an even stranger cousin.
Through the medium of genetics...
Aha, you've said it again!
So, Alice isn't the only one who can have fun with cool animals
at the Christmas lectures.
So, Alice brought in a horse and an armadillo.
And a bat. And a bat.
But I present to you - the fruit fly.
So maybe you've seen these before, you've probably seen them
if you've left some over ripe fruit lying around your kitchen
in the summertime. They're so wonderful!
You are going to believe me.
You are going to soon think that these are cool.
You don't think they're cool yet
but wait till I finish telling you about them.
So, we're talking about similarities.
And just take a little look.
These guys don't look similar to us at all, do they?
I mean, they don't even have bones
so Alice won't be interested, we know this already.
Oh, they wear their skeletons on the outside? How ridiculous!
No bones to speak of.
They have beautiful red compound eyes, and they've got six legs,
and they've got those lovely, delicate wings.
So, we're talking about trying to find similarities
and I bring out these things.
But these guys are the absolute heroes of genetics.
So, they're actually responsible for at least six Nobel prizes.
So it's thanks to these... Do you want to give them their prizes,
Alice? Prizes? Who said prizes!
It's thanks to these that we understand the basis of a gene.
That we know about the existence of chromosomes.
The existence of sex chromosomes.
And we also understand your body clock, the thing that makes you feel
wakeful in the morning, sleepy at night and hungry
at particular times of day.
And so, the story of these goes back over 100 years to a place called
the fly room, which was a lab.
They called it the fly room because it was full of these lovely guys.
And these were the first people
who decided to study these fruit flies for genetics.
The thing that they were really interested in though was mutants.
They had things like this. This is an extraordinary mutant.
The one on your right is a normal fly with its beautiful red eye.
But something's totally missing on the other side.
That one's completely missing its eye.
So that's an example of a mutant.
And by studying these mutants, they could understand lots of common
principles, lots of the basic principles of genetics.
But there was a particular kind of mutant that was especially
interesting for what we want to talk about today.
And those were mutants that had body parts
in the wrong places. So, look at this one here.
On the left, this time is a normal one.
That's the fly head from the front.
But on the right, something has gone quite drastically wrong.
And what's happening there is there are actually
legs growing where they should be antennae.
So they're legs, but they're growing
in totally the wrong place.
So by studying thousands and thousands of these
kinds of mutants,
they discovered a small number of genes that could change
the body parts around.
And these genes are master control genes.
These are regulators and they turn on lots of other sets of genes,
and they make everything else happen.
So, they're kind of like a master key
that unlocks a whole pile of things.
And these are called Hox genes.
So, the correct Hox genes turn on to get the right body parts
in the right places.
But to really explain this, I think we need more than words.
I think we need actually to play a game...
Called Build A Fly! Build A Fly!
And we are going to need some volunteers.
Somebody in a lovely rainbow jumper.
And we'll pick somebody from over here as well.
In your lovely turquoise jacket. What's your name?
Louis. Louis?
Would you stand here in front of this bowl?
And what's your name? Alice.
Alice! Good name. We've got an Alice.
And this is your part here.
And I've got Holly and Louis over here.
There's a picture here.
So, development is really, really complex but we're going
to pick it up where the fly embryo has already
divided into segments.
So, it's grown a bit.
You can think about this shape here.
It's a bit like a little grub, it's got these little segments.
These are artificial colours that have just been added
so you can see them.
In the real thing, there's 14 segments
but we've simplified and we have four segments.
So, these are our four segments.
We've got one, two, three,
four segments of this fly.
In every segment, it looks kind of the same.
We don't have any structures growing yet.
We don't have any legs, we don't have any wings
growing anywhere yet.
If we look inside, it also looks quite the same.
Because one thing we have here...
..are these Hox genes.
These master regulator Hox genes that can control locks
and unlock huge portions of the genome to get the right body
parts in the right place.
So, I've got these four Hox genes in the first segment.
But they're also there in the second segment,
and in the third segment. Look, Alice has the same set there.
So these are all present everywhere.
So that's not the difference that's going to make it work.
If we look here, we've got the fly genome
that can be potentially unlocked.
But we've got the fly genome here, we've got same genome
in all of the cells of the entire body.
So, what we need to happen is we need the right body parts
to grow in the right place. So we need something else.
We need only one Hox gene to be turned on there.
Only one to be turned on there, only one there, and only one there.
But which one is the right one?
Only the right one should get turned on
if we want to get the right parts in the right places.
So, there's an extra something I haven't shown you yet.
Which is, there is a difference inside these segments.
And I'm going to represent this slight difference with colour.
Now, don't turn around yet.
Now, each of the cabinets is lit up in a particular colour.
That colour is going to match one of your Hox genes here.
So, when I give you the word, I want you to quickly turn around,
look what colour you have got, then find the matching key.
And then, you're going to figure out which cabinet door will open.
So, you're going to have to try a few of them until you find
which one's open. Right, do we get it? Are you ready? Steady, go!
We've got red, yellow, green, blue!
Keep trying, try them all!
It's got to be that one.
Can you get the key in?
Yes!
Yes! Now, you might want to... Can you slip your shoes off?
I can help you. Just kick them off.
I'll help you get into this.
Now, you've got a lovely bolero jacket.
Put your arms through that. On the other side. Close the front.
OK. We'll get you lining up. Here we go.
You did get the tricky one, I'm so sorry.
There we go, and there's another strap there.
Right - before we started, nothing was growing anywhere, we didn't know
what anything was going to look like. We didn't even know which was
the head end and which was the tail end. But now we've got your head.
Look at these lovely wings. Can you turn around a little bit?
Lovely wings are growing here.
And look. Lovely fly legs.
And Louis is the back. Brilliant.
And look at this. We now have a fly!
Thank you so much. Thank you.
Brilliant volunteers. And you make a wonderful fly.
I'm sure you're good humans too.
That's all of the segments, and all in the right order as well.
Yeah, yeah, yeah. So, these Hox genes
are just at this amazing juncture.
And when you turn on the right Hox gene in the right place,
you get the right body parts in the right place.
But if you have the wrong Hox gene turned on,
well, that's when you get those weird mutants -
where you have legs growing out of heads, and things like that.
But a really amazing thing about these as well,
is that these don't only exist in flies.
Flies have these Hox genes, and as we pointed out
at the beginning, we could hardly see any physical similarities.
They look totally, totally different.
So, would you be surprised if I told you that these same body plan
genes also operate in us?
We have these genes too, even though our body
looks totally different.
But we do have a head end and a tail end.
And we've got middle bits with appendages.
Essentially, the genes are actually the same.
So, if I was to give this to you, Alice, this Hox gene that worked
for unlocking the fly head in the fly genome.
But we're not looking at a fly genome any more.
If we make this... Ta-dah!
The human genome. Well, that same Hox gene will work.
So, go on, try it on the Cabinet. OK.
All right. It should work in this top one here.
Yep. But this time, that Hox gene which is very similar to the fly Hox
gene is unlocking the human genome.
And we get... Ta-dah!
Look, it's got Alice's hair.
So no matter which animals we're looking at,
they all have the same genes.
The same genetic toolkit that lays out the body plan that says,
you know, put a head here, tail end here, legs in the middle...
That's arms but, you know, you get the idea!
It's quite astonishing to have delved into genetics
and found this similarity between flies and humans.
But now looking at the DNA,
we've managed to find that the fruit fly is a relative too.
Something that looks so different.
We can now add another link on our Tree of Life.
Our fabulous, beautiful tree. Beautiful! I love this.
But look over here, Alice, look what we've got.
We have got the fruit fly - this amazing, fruit fly.
Now, do you please now agree that fruit flies are cool? No.
I hope so. Yes! Thank you, some vindication.
So, we have this fruit fly and if we trace back the ancestors.
We go up through branches here. It's going really high.
Humans way over there. Yeah.
So, we're actually going to have to go to the top bar there.
Even with a stepladder... We need to lower it a bit more.
I'm not going to be able to reach up there.
What's this ancestor going to look like?
Well, it looks like this. Here's one I made earlier.
Was that you, Alice? Well done.
I'm so good at origami.
So, this is not a fly, it's not anything like a human.
It goes back to a really, really, really ancient ancestor
that is, what? A worm? A segmented worm. Yeah.
It doesn't have any appendages.
And it goes up here, so we're now travelling back in time
about 800 million years
to put that segmented worm on our Tree of Life.
And it's Christmas, so you have to be nice
to your relatives.
So we found all these astonishing connections with the rest
of life on Earth.
With all these other groups of animals,
we found connections between humans and bats and horses and armadillos.
And we can place these ancestors then as well on the tree.
We're working back through time.
And we can place them very precisely.
We know where they should go, using both the fossil record
and the molecular clock to place them in time.
So, we can reconstruct our big family tree then and we can go back
and back and back in time.
If you look right up there - you can see a little light.
So, where our family tree is disappearing into the ceiling,
that light represents the common ancestor of all life on Earth.
And that was a single-celled organism four billion years ago.
And its descendants today are mostly single-celled organisms.
They outnumber all of as multicellular creatures.
But its descendants also include plants and fungi,
and then, all of the animals
that we've been looking at. All life on Earth.
Every single thing.
So, since that last universal common ancestor,
life has been unfurling
and evolving in many, many directions.
Just some of which we've shown here.
And only one of those pathways leads to us.
And we come all the way down to humans at the bottom here.
This puts us in our place. It shows us where we come from.
And we are not the pinnacle of evolution.
But we're in a fantastic place, I think, because we're not separate
from nature, we're very much part of it.
We are just one species amongst billions.
So, just one of these little leaves then represents us,
represents our species.
And in the next lecture, we'll be focusing in on humans
and finding out how we evolved as a very special group of apes.
We'll be looking at our closest living relatives,
the chimpanzees and the gorillas, and finding out about
the differences that make us who we are.
But for tonight - it's goodnight from me.
And it's goodnight from her!