What does it take to be a scientific pioneer?
To reframe and popularise evolutionary theory?
To reveal a new material, and win science's most coveted prize?
To discover one of palaeontology's elusive missing links?
Is the key to brilliance talent, ego or just plain good luck?
What makes a beautiful scientific mind?
Professor Jenny Clack is a world-renowned palaeontologist,
who solved one of the greatest riddles in the history of life on our planet.
One of the big questions that people had been trying to answer was,
how do you get from an animal that lives in the water and has fins,
to an animal that walks on land and has limbs with fingers and toes?
In the late 1980s, she found and described the fossil Acanthostega,
an ancient creature which offered new evidence
of how fish evolved legs and made the transition onto land.
Her talent for seeing what others had missed rewrote the textbooks
and led to global recognition for her work.
She's the great pioneer.
She's the one who led the way
and opened up this area that we others have come into.
We do talk about the Clack theory of the origin of tetrapods.
It does sometimes do to think about things that you take for granted.
What if it's not this way, but it's the other way?
But becoming a pioneer was by no means inevitable.
She's not a person with sharp elbows. That's not it at all.
It was quite clear she didn't have a great deal of confidence in herself.
Clack had to find the courage to take on
the stifling academic etiquette that had hampered research for decades.
The field had become moribund, and now it's been completely unlocked.
Answering one of evolution's greatest mysteries would mean
travelling to almost the ends of the earth for fossil evidence.
I was actually terrified, but discovery of those materials
was probably the most exciting thing after falling in love.
Just what does it take to turn accepted thinking on its head,
and make the palaeontological discovery of a generation?
Jenny Clack has made a life's work out of trying to find traces of a world
hundreds of millions of years ago, before even the dinosaurs.
Her passion is for the very first creatures that emerged from the seas
to conquer the Earth.
For me, trying to imagine what these animals were like,
it's a sense of mystery, where the animals are totally different
from anything that we have today.
It's trying to just imagine what they were like and what they were
doing, and what life was like for them, and just wanting to be there.
But the evidence is elusive.
With only scant fossilised remains to go on,
seeing into the rocks poses a creative challenge.
That has a lot to do with wanting to see something else
in the specimen that nobody's ever seen before,
and being able to see a little bit more about it.
It all goes into this sort of imagination
of what the animal would have been like.
Jenny's fascination for this era, known as the Devonian,
has fuelled her imagination since early childhood.
What sparked my interest in palaeontology
was an illustrated book called Prehistoric Animals,
and it had sections on the earliest part of the fossil record,
and it was always those earlier sections that really intrigued me,
and I remember flicking through this book, starting at the beginning,
and listening to the slow movement of Shostakovich's Fifth Symphony,
and if you do that, the music fits the pictures perfectly.
And if you know that piece of music,
that kind of sums up how I imagine the Devonian to be.
The story of the colonisation of the land by the creatures that
emerged from the swamps and pools of the Devonian Period
is one of the most fascinating episodes in the history of life.
But this mysterious world was a long way from the Manchester suburb
where Jenny grew up.
It wasn't a particularly special household.
A simple terraced house, fronting onto a road.
My parents were not at all academic.
In fact, they were very poorly educated,
and I don't remember the house being full of books, for example,
apart from the ones I borrowed from the library.
But we had the great advantage that,
across the road from where I lived, was a pond,
and in that pond were sticklebacks and tadpoles and all sorts
of wonderful things, and I used to bring home sticklebacks and newts.
My mother hated newts, but she let me keep them anyway.
And that was just a wonderful resource.
I was an only child, so I would go there regularly by myself.
Intrigued by the primitive-looking animals she found on her doorstep,
Jenny soon discovered there was another way
she could connect with creatures from the distant past.
Through fossils.
The remains of these animals will be down in the rocks,
well below the surface of the Earth,
but where cliffs like this have broken away,
then the rocks are exposed, and we can see where the animals' remains are.
By the time I was 11 or 12,
I'd heard of this great Victorian fossil hunter called Mary Anning,
who lived and worked at Lyme Regis,
and found some wonderful specimens like the fish lizards,
ichthyosaurs, and I decided that I wanted to be the new Mary Anning.
So we duly went to Lyme Regis.
While most children were playing on the beach,
Jenny was engrossed by the fossils.
I didn't find any ichthyosaurs, but we did find lots of ammonites,
and I thought to myself, "Wow, that sounds wonderful.
"I really want to do that."
Jenny had found her life's passion,
but for a girl growing up in the 1950s,
palaeontology wasn't seen as an obvious choice.
'Science plays an important part in the curriculum, these days.
'But girls who may be among the leading biologists must also
'be able to use their hands, and that's a useful experience
'when it comes to shopping in the future.'
When I was in my secondary school,
I actually felt very much of an also-ran.
I don't think I was considered anything special.
Certainly, it was never suggested that I would take the Oxbridge exams.
When it came to A-levels, they weren't as good as expected,
and I actually got into my fourth choice, Newcastle upon Tyne,
chosen really on the list at all because, one, it had a palaeontology option,
and two, it had a Gilbert and Sullivan society.
Don't let's be downhearted!
There's a silver lining to every cloud.
Certainly! Let's be perfectly happy!
By all means! Let's thoroughly enjoy ourselves!
It's absurd to cry.
Quite ridiculous!
Jenny's fourth choice turned out to be a lucky one.
The palaeontology option was thriving at Newcastle,
under the leadership of the forward-thinking Dr Alec Panchen.
'At Newcastle University Department of Zoology,
'Dr Alec Panchen talks about the difficulty of deciding
'how the first reptiles may have emerged from amphibian ancestors.'
If one looks at a reptile, such as a lizard,
and then an amphibian, such as a newt or a salamander,
the differences between the two aren't so obvious.
Dr Panchen's lab was one of the few places in the world
looking at the origin of tetrapods,
the broad term used for all four-limbed vertebrates,
from amphibians to mammals.
He was studying the earliest known tetrapods,
from over 300 million years ago,
precisely the era that had fired Jenny's childhood imagination.
But Dr Panchen set a high bar.
Alec Panchen was a very meticulous worker.
His papers have immense detail.
His drawings, beautiful reconstructions of skulls,
incredibly detailed.
Quite intimidatingly, for his students.
We all felt we had to try and draw like that
or we would be failures, and it certainly pulled us up a lot.
Although keen to study with Panchen,
Jenny found it hard to attract his attention.
I actually found him quite difficult to talk to.
He's very, very reserved.
When you get two people who are quite reserved together,
the conversation doesn't always flow freely, shall we say.
Panchen's elite group of PhD students seemed out of reach.
Well, she was very reserved, and in that sense,
maybe she didn't feel confident enough,
but there was no indication that she had talents
that would get her where it finally did.
When I got to my final year, I would have liked to do a PhD
in palaeontology,
but I was also told that Panchen didn't take anybody on
who hadn't got a first,
and I thought I was unlikely to get a first.
And, in fact, I didn't.
And so, I sort of gave up on that idea.
Instead of applying to join Dr Panchen's exclusive circle
of research graduates, Jenny opted for a less challenging job
in a regional museum in Birmingham.
My first job was a display technician.
Well, I wasn't altogether happy as a museum education person,
because I'm not that comfortable with children,
and of course a lot of the job was working with children.
I don't really know how to deal with them.
And she might have stayed in that job without the encouragement
that came from a chance meeting.
When I was working in Birmingham, I got interested in motorcycles.
And while I was at motorcycle club, I was part of a folk group,
and this guy was doing a floor spot, singing by himself with a guitar,
and I don't know what brought this subject up,
I don't know why he mentioned it, but he said the word dimetrodon.
She heard the magic word and pricked up her ears, and it really
was just a matter of time before we actually met from then on.
"What is this guy doing mentioning dimetrodon?"
Pretty soon we got to know each other.
So, yes, we never looked back.
Jenny's future husband Rob didn't only share her passion for bikes.
Soon the couple were hitting the road as fossil hunters.
We certainly would take our holidays on the back of a bike,
going up to Scotland to look for fossils.
And Rob would prove to be a vital support
at times when Jenny was uncertain how to progress.
It was quite clear, in those days, that she didn't have a great deal of confidence in herself.
But, looking back on it, that was simply a lack of experience.
With Rob's encouragement, Jenny kept nurturing her passion for fossils,
and it wasn't long before she spotted an opportunity.
My boss at the time knew that I wasn't entirely content in that job,
so she suggested that I do some private study,
because the local authority actually allowed staff to take off
three weeks a year to do some private study,
and so I took a chance.
Jenny knew that Bradford City Museum owned a fossil
that had been discovered in a local coal mine.
It was of a 300 million-year-old creature called Pholiderpeton,
thought to be one of the first tetrapods to venture onto land.
Jenny's old university tutor, Alec Panchen, had tried without success to get his hands on it.
Many years before, they had put it on display
embedded in a block of concrete,
and they would never take it out of the concrete for Alec,
and he was always very upset that this was the one specimen
he had never been allowed to work on.
Jenny hatched an idea that she thought just might impress him.
Using her museum connections, she promptly went and borrowed it, so she had it.
She recognised the power of having a good hand of cards
when you negotiate something.
Her hunch proved right.
Intrigued, Dr Panchen invited her to join him in Newcastle to inspect the specimen.
But it wasn't an easy fossil to get to grips with.
I remember a colleague of mine having a look at the specimen,
and he's used to dealing with roadkills, but he said,
"My Goodness, that's a mess!"
That was his reaction to the specimen.
But it turned out to be much more interesting
than you might have expected.
Despite having little time to impress her old tutor,
Jenny's sharp eye began to reveal itself.
I was preparing it, and looking at the bits that hadn't been exposed to the surface before,
and I found this peculiar chunky bone,
and I showed this to Alec, and I remember his precise words.
He said, "Well, I'm damned. It's a braincase."
And then, a few seconds later, "There could be a PhD in this.
"I could probably get a grant for you, if you're interested."
Can a duck swim?
Jenny promptly quit her museum job
and headed to Newcastle to begin a new life of academic research.
The Bradford fossil Pholiderpeton would form the basis of years of painstaking examination.
'Here in the Department of Zoology at Newcastle University in England,
'a research student is working on the fossil remains of one early amphibian.'
This animal lived 300 million years ago, and one can only be
fascinated and curious about what life was like in those days.
I'm, in fact, the first person to restudy this animal since 1926.
'She first of all cleans away parts of the matrix surrounding
'the fossil using a dental mallet, then further cleaning up
'by blasting with a jet of sodium bicarbonate particles.'
You're exposing things that have never been seen by anybody before.
It's compulsive. Your sense of time just disappears.
And unless somebody comes and knocks on the door and says,
"Time for a cup of tea," you could just stay there.
When you go to sleep at night, and you close your eyes,
you can see it in front of you.
It's a bit like watching a movie.
If you prepare your own material,
it does give you an intimate view of what you've got.
And this Bradford fossil was a rather strange specimen.
It had, probably underwater,
crawled inside a hollow tree trunk and died,
and then decomposed, and you knew it was all one animal,
and you knew that you had all the bits.
If only you could take it apart and put them together the right way.
As she put the pieces together, Jenny made a startling discovery.
It was one Friday evening.
I was working on the airbrasive,
and there was a little bone right at the tip of the specimen,
rather apart from all the other bones, so I sat and I prepared it.
So, this thing is about yay long.
Like nothing I'd ever seen before.
And I thought, "Now, wait a minute.
"The only bones that I can think of which have got holes
"through like that that aren't vertebrae
"would be one of the braincase bones at the back called the exoccipital,
"or a stapes."
My mind actually couldn't believe it to start with.
The stapes is a tiny bone in the ear of modern vertebrates.
Its ability to vibrate is critical to hearing.
No-one had ever discovered a stapes in an early tetrapod before,
as the bone was thought to be too small to survive fossilisation.
But there was something strange about this stapes.
What the stapes showed that I found
was that it was completely the wrong shape,
and it was fixed in a way that meant it couldn't transmit vibrations.
It wasn't free to vibrate.
So something odd was going on.
A stapes that was too big and solid to vibrate
would be useless for hearing in air.
But the prevailing theory
was that early land-dwelling tetrapods must be able to hear.
Jenny wondered if there was another way of looking at it.
It does sometimes do to think about things that you take for granted
and turn them on their heads.
What if it's not this way, but it's the other way?
The assumption had been that as fish evolved into tetrapods,
a bone in the jaw had rapidly transformed
into the tiny stapes that could vibrate.
Jenny's discovery suggested that this transformation had not
occurred as early as previously thought.
So, the stapes that I found is a step along the way into making
a modern ear in something like modern reptiles.
But it doesn't do it straight away.
Jenny wondered whether the bone she'd identified was in fact
evidence of a whole sense, hearing, in the process of evolving.
What if these animals couldn't yet hear?
Think about it like this.
What was there for it to listen to?
There weren't any creaking insects, there weren't any birds,
no animals were making noises.
The only sounds would have been the wind in the trees,
leaves blowing about, that kind of thing.
She began to trawl through decades of academic descriptions
of the ears of early tetrapods,
and soon realised that many of them did have stapes.
Jenny had spotted something that had been right under peoples' noses
all along, but simply dismissed as an unimportant scrap of bone.
Alec Panchen had been working on another related animal for some time.
There was a stapes, only Alec hadn't described it,
and Jenny pointed it out to him, you know, there, and it looks the same,
and he admitted that he had passed over it in embarrassed silence.
Jenny's work on stapes updated the textbooks.
Her unique way of seeing was yielding results.
One of the interesting things about it is to show
how what you see is governed by what you expect to see.
And that happens all the time, actually.
You don't always see what's there, because you've got a certain predisposition.
It certainly had been excellent training for her,
and it was clear that this was somebody who was capable of
changing the way we thought about some of these animals.
Well, it was at that point that I thought perhaps there were
other things that people have always taken for granted
that aren't the way we thought they were, and yes,
that was a lesson that I've continued to apply.
That certainly stood me in good stead.
Jenny was beginning to get noticed.
She landed a prestigious job
as a curator at Cambridge University's Museum of Zoology.
I was quite amazed when I got a job in Cambridge because,
not having been considered as a candidate for Oxbridge at school,
there's no way I was going to get into Cambridge.
I sort of felt that I'd got in by the back door,
via the museum connection.
In those days, many of the staff at Cambridge
still looked down on anyone who was "redbrick", and I think Jenny
had a lot more problems from being a redbrick than being a woman.
And certainly, several of them would always refer to her as Mrs Clack, not Dr Clack.
Aware that critical eyes were upon her,
and with the freedom now to pursue her own research,
Jenny chose to tackle one of the biggest mysteries
in our evolutionary story.
One that had taxed some of the greatest minds in palaeontology
for decades.
One of the big questions that people had been trying to answer,
in various ways,
was how do you get from an animal that lives in the water and has fins,
to an animal that walks on land and has limbs with fingers and toes?
And the evidence was simply absent.
Many of us would say it's more radical than anything that's
taken place on land, and that the origin of reptiles,
the origin of birds, the origin of mammals are all, really,
less radical than this fish-to-tetrapod transition.
It was thought that this important transition
from fish to vertebrates with limbs occurred during the Devonian era,
which began 400 million years ago.
But there was precious little evidence of how it had happened.
Imagination is very important in any science.
You have to be able to think about things that you can't see,
but exist in your head, and for a palaeontologist,
it's a question of imagining such a world as we've never been a part of.
The earliest evidence palaeontologists had was Eusthenopteron,
a fish with the precursors of our major limb bones,
dating from 380 million years ago.
But the next complete fossil specimen came after
a whopping gap in the record.
We have an animal called Eryops,
which is perhaps 80 million years later,
which has got perfectly robust limbs with fingers and toes, so those two
animals between them formed the sort of icons of the transition,
with the fish at one end of the spectrum,
and the tetrapod at the other end.
A major anatomical transformation had taken place during this time.
In the absence of hard evidence,
palaeontologists settled on the theory that periods of drought
had driven fish with proto-limbs onto land.
It was very much seen that an animal like Eusthenopteron,
while hopping from one drying pool to another, like a mud skipper,
would actually enhance its capabilities on land,
and that legs evolved from the fins
while it was on land, trying to do this hop, skip and a jump.
This is a hypothesis that kind of captured the public imagination,
and it really had a big influence on people's thinking for several decades from about the 1950s.
The only thing that could establish what actually happened was evidence.
Fossils of a creature from the middle of this gap,
which could reveal how the transition took place,
but there was one candidate for the role.
The only thing between Eusthenopteron and Carboniferous tetrapods with legs
was, for many decades, Ichthyostega.
Literally, that was all.
Ichthyostega was an intriguing tetrapod from 360 million years ago,
right in the middle of the fossil gap.
Its anatomy seemed to nod to the fish that came before
and the land animals that came later.
But the only specimen in existence was frustratingly off-limits.
Ichthyostega was in the hands of an eminent Swedish researcher, Erik Jarvik,
who had unearthed a cache of well-preserved fossils
on a pioneering expedition to Greenland in the 1930s.
In those early days,
these expeditions were really quite heroic, and it's a remarkable thing
that they brought back the material they were able to.
Conditions were really much more, how can I put it, primitive than today.
On his return from Greenland,
Jarvik set about a painstaking
investigation of this new discovery.
Jarvik was very hard-working and very single-minded,
and he was also quite talented, but not immensely talented.
Many things he got right, quite a few things he got wrong,
and he would never change his mind.
With Ichthyostega, Jarvik struggled,
and there were parts of the anatomy that he was never able to make sense of,
and he published it very, very slowly.
But the academic convention of the time meant that if other
researchers wanted to study this animal, they'd simply have to wait.
Because Jarvik had charge of the material,
it was felt to be his territory.
The etiquette of the time was really quite distinctive.
If somebody's in the middle of working actively on something,
in particular if it is stuff that they have collected themselves,
you don't just muscle in.
That would be considered very poor form.
The Stockholm crew had complete sovereign rights over
not only the material they had collected,
but really, the late Devonian of Greenland as a concept.
Other researchers' response to Jarvik's initial findings
only added to the delay.
When Jarvik published his work, British and American workers ridiculed it.
He was a sensitive chap,
and the result was a lot of bottled-up anger.
And it coloured his view of scientists outside Sweden
for the rest of his career.
And at this point, he felt disinclined to satisfy them
by publishing any more about it.
And he took the view that they could now wait
and he would work very slowly for several decades.
And he finally published his monograph in 1995,
having outlived most of his first generation of critics.
Jarvik's long silence left the field effectively closed.
This was immense frustration,
because the problem is that you can't really work on this kind of thing
without the material.
And if people aren't prepared to lend it to you,
because they are "working on it",
there's very little you can do about it.
He would frequently sit at conferences and not speak to anyone.
And he showed very little wish to engage in conversation.
Somebody did try to suggest that he should pass it on.
In fact, to Alec Panchen.
But this caused an immense rift between Jarvik and Panchen.
Not that Panchen felt it. But Jarvik did.
And that scuppered anybody else's chances
of getting their hands on it as well.
So you had this huge gap between a fish at 380 million years
and fairly well-known land animals at about 330-300 million years.
And in between, you had Ichthyostega
which was not very well-known at all.
It meant that nobody else could really think about it.
It was out of bounds.
And the subject remained moribund for decades.
Jenny knew that the only way to overcome the stifling etiquette
would be to somehow find different samples.
But Greenland was one of the only places in the world
with the right kind of Devonian rock.
It would be a very good area for an ambitious palaeontologist
to get into, IF you can find the specimens.
And the fact that Ichthyostega was known only from Greenland
which meant, at the very least, an expensive expedition,
meant that for many people
this was probably too onerous and complicated to envisage.
Then Jenny had an extraordinary breakthrough.
Brooding about Greenland,
she decided to ask the geologists
at the Earth Sciences Department over the road
about any trips they'd made there.
One recalled that a student had been to Jarvik's area of Greenland
in the early '70s, and had left some specimens in their storeroom.
In notes from a student, it said,
"We found tetrapods at three localities."
And that triggered an alarm.
Where is this material?
Jenny went down to the basement to see if she could find the fossils
that had been of little interest to the geologist.
And he pulled out a drawer full of this material.
He had no idea what it was he'd found.
It turns out that what the student had found was actually material,
not of Ichthyostega, but of a second animal
called Acanthostega,
which hitherto had only been known from two fragmentary specimens.
And what the student had found was a block
with three skulls of this animal together in a row.
I was blown away. Absolutely blown away.
I thought, "Oh, gosh!"
She was tremendously excited, because suddenly this
represented an opportunity to study a completely different animal.
A contemporary of Ichthyostega's, but obviously just from the skull
you could see that it was a very different animal.
And so it had to tell us lots of interesting, new information
about the evolution of tetrapods from fish.
Keen to know more,
Jenny managed to track down the student's field notebook.
In his scrappy notes
were altitudes and mountains,
and exactly how he'd found this material.
So we then knew pretty much where to go back and find this.
So, I mean, the obvious thing to do was try and get back there.
And go to the same locality.
The future rolled out in front of me.
I saw...I saw the future.
What was likely to happen.
It was astonishing that the only collection
of other Devonian tetrapod material was about 200-300 yards
from where she'd been working, and she didn't know about it.
None of us did.
That's luck, I'm afraid, by anybody's standard.
Well, luck and timing play into it in a big way.
But I think the key component, in a sense, one of the key components,
is spotting the chances when they come up, and leaping for them.
The next move was to get in touch with people in Copenhagen...
..and try to get them to agree to organise a joint expedition.
To go to Greenland,
Jenny would need permission from the Danish authorities.
Something no-one had ever previously managed,
owing to academic sensitivities.
They were always denied access.
This was because people in the museum in Copenhagen
didn't want to upset Jarvik.
So there's quite a lot of political activity behind this, as well.
Jenny saw that she had only one option.
To go and meet Jarvik, face to face.
Jenny and I went to a congress in Prague in 1985.
He was there.
She was, as I say, not a very forceful person
in initial conversation.
She's quite reserved, she's quite careful.
Where others had failed, Jenny's calm approach
and willingness to search for a fossil other than Ichthyostega
apparently won Jarvik round.
Although the conversation may have been initially a bit difficult,
I suspect Jarvik recognised in some ways
a slightly kindred personality type.
And not a sort of person who would go around ridiculing him
or in any way threatening him.
And in that sense,
I think she managed to charm him in a subtle sort of way.
And he was fine.
And that being the case,
the people in Copenhagen were very willing to come on board
and help get an expedition together to go back to Greenland.
Jenny now faced organising the most challenging fossil hunt of her life.
Enlisting her husband Rob,
and her PhD student, Per Ahlberg, to help her.
We'd never done anything like this before. I was actually terrified.
I had no idea really what to expect,
except that it's going to be difficult.
We were going in helicopters, and everybody knows helicopters crashed.
And polar bears eat you.
We knew this was going to be a hard trip.
We knew that we would be out in the field,
camping 300km inside the Arctic Circle.
We knew it was going to be cold.
We knew it was going to be hard work, climbing up mountains.
And we knew we were not very fit.
My girlfriend knitted me a nice, warm, new jumper.
I've still got it, too. It's got fish on it.
I've still got the same girlfriend, too.
In July 1987, a Danish support team deposited Jenny, Per and Rob
on the side of Stensio Bjerg, in the remote northeast of Greenland.
Now suddenly, here you are.
There's nobody for 100 miles in any direction.
That is isolated.
Having set up camp and made things work on that level,
we now had to go out and find something.
And if we didn't find anything of any significance,
it would be rather embarrassing
and rather a lot of money spent for nothing.
Looking for fossils can be a thankless task.
Because most of the time, you don't find anything.
For the first few days, we couldn't find where we were supposed to be.
We weren't even sure we were on the right mountain.
And we thought,
"We're here for 6 weeks and not going to go back with anything?"
We were walking on very steep scree slope,
made up of small slivers of rock.
Very loose, very insecure.
And at the bottom, we could see what appeared to be a sheer cliff
waiting for us to fall over it.
So we gave up.
And the three of us trudged back down the mountain,
feeling very depressed and ashamed, as you can imagine.
Jenny, as I recall, was getting quite worried about
whether anything useful was going to come out of this.
Because we were looking for white bone in darkish brown rock.
So anything white caught our eyes and we thought for an instant,
"I've found a fossil."
But a lot of the time, it was bird shit.
Almost one week in, the exhausted party
launched a third attempt on the mountain,
approaching it at a different level.
One of us, I forget who now,
picked up a little slab with a piece of bone on it,
showed it to Jenny, who gave a kind of whoop,
because this was part of the back of the skull of Acanthostega.
It was a piece of the same fossil animal
that Jenny had found in the drawer in Cambridge.
She realised that they must be close to the area
described in the student's notes.
As we started hacking at the rock,
hack a block off, break it up...
another skull.
We realised we are in this big kind of apron of fallen material
from some locality higher up.
We kept going up and it kept getting richer and richer,
and I found a lower jaw actually disappearing into the rock.
So there we were, and we had found the locality.
Now, of course, once we'd done that,
then we were really in business.
The team had discovered a whole strata of rock
full of Acanthostega remains.
And it looked like it contained more than just scattered bones.
The dream of the vertebrate palaeontologist
is to find a complete, articulated specimen,
with every bone in place, so you tip it out the rock and you can see what's going on.
One of the specimens that we found,
it was clear that it was a head at one end
and then leading back from there,
in sort of a glancing sunlight, was a row of bumps,
which looked as though they might be vertebrae.
We didn't know what we'd found.
But we knew it was going to be exciting.
It looked as if they had found one of palaeontology's holy grails.
The first complete specimen
of an early Devonian tetrapod.
This was it. This was the key, really,
to the rest of my career.
The discovery of those materials was probably the most exciting thing
after falling in love.
The party packed a metric tonne of fossils into crates
and returned to Cambridge.
DRILLING
Once home, they faced the monumental task
of bringing the rocks to life.
Here, you are dealing with an animal
and you don't know what it's going to look like.
Nobody knows what it's going to look like.
And you are able to piece together for the first time
a style of creature that nobody perhaps has previously seen.
Trying to imagine what these animals were like in life
is really what it's about for me.
I kind of wish we had a time machine.
That we could go back and look at the animals.
Because a lot of us are zoologists at heart.
These are animals that happen to be in the rocks.
Jenny now assembled another team
to undertake the painstaking work of fossil preparation.
When I started working on that material
using the adapted dental equipment that we use,
picks and drills and so forth,
I realised this was going to, er...
This was going to take a hell of a long time.
The Greenland rock is very hard, so it takes a long time to get
a very small amount of material out of the specimen.
You had these long periods of relatively
methodical preparation,
punctuated by great periods of excitement, so...
You're obsessive in doing this work,
because you don't know what you're going to find next.
And it's absorbing.
It can be nerve-wracking
because you don't really know where the bone is.
You have to be extremely careful and take it down bit by bit.
It's all a matter of colour and texture,
and being able to see subtle differences
as you expose different levels.
Finding out whether the Acanthostega fossils had legs was critical.
They could be the key to understanding how limbs had evolved.
I think we were pretty open-minded about it in the first place
because for all we knew, it could have had a fin instead of a limb.
I mean, other features of the anatomy suggested
that it really was quite primitive.
Jenny gave Mike Coates the job of preparing the body
of the most complete-looking specimen.
How much of the animal was there, we weren't sure.
So, of course, part of the rest of that was unpacking blocks.
Again, sitting in dusty museum basements
just trying to fit these things back together again,
how they'd been in the field before they'd been broken up.
He started work on what we thought was going to be a humerus arm bone.
And, indeed, that's what it turned out to be.
And it was pretty comparable with the humerus of a tetrapod.
The upper arm suggested
that this must be a land-walking amphibian.
But to their surprise, when Mike uncovered the lower arm bones,
these resembled those of Eusthenopteron, the fish ancestor.
It was an astonishing mix.
So then he started working on the adjoining block,
starting from the edge and working in.
And the first thing he found is a digit.
A row of elements joined one to the other, like fingers.
So he found a finger.
Digits meant a hand or a foot, not present in Eusthenopteron.
But that wasn't all.
So he went a bit further, found another one.
And another one.
And another one. And another one.
And he thought, "Ah, I've found five.
"Shall I carry on, or shall I just leave it?"
So he thought, "Just for the sake of completeness, I'll do a bit more."
And he went round and eventually came up with eight of them.
And that was...
when the fun really started.
The assumption had always been
that tetrapods had evolved with five digits.
It made a huge impact, because it seemed so outlandish.
And there were one or two people who wondered initially
whether what they had found was simply the two limbs
lying on top of each other,
giving that effect. Understandably enough.
But very quickly, when a few people had seen the materials,
it was acknowledged that this was in fact exactly what they said it was.
There had been a big debate for many decades about how digits had arisen
and why they look the way they do.
And the eight-digited limb of Acanthostega
landed kind of smack in this.
Jenny began to wonder
whether she needed to rethink the most basic assumptions.
I think as Mike was preparing the forelimb,
it just became obvious
that the forearms stretched out like that.
Really couldn't bend very far.
They just do not look like weight-bearing limbs.
So we began to think of what else it could do.
What was it being used for?
It was a confusing picture.
The arms didn't bend in a way
that would allow Acanthostega to walk.
And the eight-toed hand
looked more like a paddle than a foot it could stand on.
Then Jenny had a radical thought.
What if Acanthostega's limbs and feet hadn't evolved on land?
Perhaps limbs evolved before walking. Perhaps for some other purpose.
Swimming.
That idea, that limbs evolved in water first,
was quite revolutionary.
Maybe making their way through swampy, reedy, mucky streams.
Paddling in water, rather than walking on land.
In other words, something entirely different first.
And then only later used for walking with.
Just as she had with the stapes earlier in her career,
Jenny's creative vision was turning the received wisdom on its head.
But she knew she needed further proof.
She focused on the skull.
Inside the throat
were a series of gill bars,
which looked just the same as those that you find in fish.
So it's gill breathing. And then Mike found the tail.
Which had got long, long fin rays.
Which is useless out of water,
so that sort of completes the picture
of primitive tetrapods
living in water, being mainly aquatic,
and using their limbs for swimming.
Everybody expected Acanthostega
to look like a terrestrial animal from the neck back.
Nobody expected it to have gills.
It was a paradigm shift.
The decades-old textbook image
of a fish lumbering onto land on its fins
could only be wrong.
Other fossil evidence of plant life supported the idea
that these creatures lived in newly-formed marshland.
It seemed that the very first legs evolved not for walking,
but as a tactic for moving through dense vegetation in swamps.
Things can be evolved for one purpose
and then used later
in a slightly modified form for another thing.
And the idea that limbs
were not originally used for walking
might be counterintuitive.
But I think that's only because as humans and as terrestrial animals,
we kind of think walking must be
the be all and end all of what limbs are for.
But, of course, it isn't.
Once Jenny was ready to publish, her findings were well received.
I think she realised pretty quickly
that this was Nature-standard material.
That the journal, Nature,
which is one of the most prestigious scientific journals,
would actually publish this sort of stuff.
From when we started publishing the full descriptions of Acanthostega,
the head, the body, the limbs,
it became the model for a Devonian tetrapod.
Or a primitive tetrapod that could have given rise to later ones.
And Ichthyostega was marginalised.
But there was a remaining mystery about Ichthyostega.
Jarvik, the Swedish researcher
who had hung on to the only specimen for 50 years,
had described his animal
as having five toes.
We'd also found a hind limb of Ichthyostega
in the same expedition.
And preparation of that showed that it had seven digits on its foot.
So putting that together, a pattern of more than five digits
seemed to be what early tetrapods had.
If you go back and look Jarvik's specimen,
what he thought was one big toe, cracked,
with a lot of cracks in it, is actually these three toes.
So again, I think he was a little bit annoyed
that she'd interpreted it and he hadn't.
Jenny Clack had again seen what others had missed.
But Jarvik was unwilling to accept that science had moved on.
He finally published his definitive text on Ichthyostega.
And in it, he used photographic evidence of his own
to dismiss Clack's specimens as freaks.
Jarvik didn't really believe our story,
or our interpretation of the evidence.
So he considered that the material
of Ichthyostega and Acanthostega
were both mutants that we happen to have found.
You know, we know how rare mutants are in normal life.
And the idea that we had found two of them was a bit silly.
He just had the mindset that he had this safe knowledge
and that what we had found contradicted that.
So it was wrong.
Jenny's not like that at all.
She's very open-minded about her work.
One of the things that I appreciated very much being her student
was the sense that the student was always welcome to disagree
with the supervisors.
I don't imagine Jenny has ever thought herself to be infallible
in any aspect of this stuff.
This, of course, is the mark of a really good scientist.
Because that way, your science becomes self-correcting.
You're not going to veer off to the side and land in the ditch
which, in a sense, is what happened with Jarvik and his interpretations.
You will continue to head onwards towards a more and more
accurate understanding of the animals you're working with.
Other palaeontologists embraced Clack's theory
of the aquatic origin of limbs,
opening up a whole new area of research.
All of a sudden, Devonian tetrapods went from being
a marginal subject area to one of the hottest areas in palaeontology.
It's catalysed the whole thing.
We are now finding Devonian tetrapods worldwide.
And if you look at a graph
of the number of taxa known of Devonian tetrapods,
it's gone like that.
So it's almost exponential increase.
It's had a huge impact.
It's as though the field had become moribund,
and now it's been completely unlocked, and it's vibrant.
It was pretty radical.
Yeah, we rewrote the textbooks, effectively.
How long that will last, I'm not sure.
But that remains to be seen.
The self-deprecating girl
who never expected to do a PhD
had reached the pinnacle of her field.
Whoever you asked in the subject would say
Jenny is the world leader
in research on the origin of tetrapods.
She's the great pioneer.
She's the one who led the way and opened up this area
that we others have kind of come in to
and continue to contribute to.
And she continues to drive that subject forward to this day.
She is, for most of us, the leading worker in this field.
And as a measure of this,
we do talk about the Clack theory of the origin of tetrapods.
And there are very few other workers in vertebrate palaeontology
where a theory, a current theory, is immediately understood
by virtue of the name of the person who came up with it.
I think Jenny definitely deserves all the awards
and status that she's getting.
I'm sure she'd say she doesn't, but I think she does.
It's characteristic of a really good palaeontologist that they have,
how can I put it, the imagination
to understand these wretched remains as a one-time living organism.
And Jenny is very good at this.
Jenny became Professor Clack in 1997.
But her greatest accolade came when she was invited to become
the first woman in her field to join the Royal Society.
I suppose I had secretly wanted that for years
but never thought it would happen.
And I was nominated by the director of the museum at the time,
and I thought, "It's not going to get anywhere."
But it did. It was one of the most thrilling days of my life,
when I got that letter.
I don't think she made a great fuss about it.
I don't think she went round saying, "Hey, look at me!"
That's just not in her persona.
I was immensely proud, and I went round shouting, "Hey, look at her!"
But I'm still constantly amazed by how my career has gone.
And it's not finished yet, of course.
But, erm...truly astonishing.
Since describing Acanthostega, Professor Clack has remained
at the forefront of tetrapod research,
with over 140 publications.
And she continues to make new discoveries
that fill the gaps in the fossil record.
But she accepts that her theories could yet be superseded.
All our discoveries...
Fossils will remain,
but the interpretations can be overturned any day.
All this knowledge is provisional.
And this is something that people don't really
understand about science.
That it's not about certainty.
It's not necessarily even about facts.
It's about questions. And the answers that you give.
A lesson in life's impermanence,
that perhaps only palaeontology's long perspective
could have given her.
We should remember that we are only here temporarily.
We do need to bear in mind that
something will evolve to take our place at some point.
And I like to speculate about
which group of animals that might come from.
My betting is on rodents, actually.
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