Your inner Reptile

from the plains of South Africa to the shores of Nova Scotia in the bones of ancient creatures near a skull right in this block and deep inside your DNA lies an incredible story the story of your body and why you're built the way you are your skin and hair your complex teeth and remarkable sense of hearing can all be traced back to ancient reptiles that once ruled the earth their bodies were shaped by great transitions in the history of life and that legacy still shapes our bodies today my name is Neil Shubin as an anatomist I look at human bodies differently for most people within us I see the ghosts of animals past distant ancestors who shaped our Anatomy in surprising ways prepare yourself for a trip back to an ancient world if you really want to know why you look the way you do it's time to meet your inner reptile it was here in the small town of pars burrow in Nova Scotia over 25 years ago that I first discovered my inner reptile oh my gosh this was my second home when I was a graduate school this little Main Street I can't tell you how many times I ripped back and forth a lot of my personal histories on the street back then I was a young eager Harvard graduate student off to lead my very first fossil expedition yeah there's the bait is it beautiful when you're catching it a really nice time what makes the Bay of Fundy a special place to hunt for fossils is it's huge tides they're the largest in the world in just six hours 100 billion tons of water drains half a mile out to sea these massive tides constantly erode the cliff face making it a wonderful place for exposing new fossils you know we came to Nova Scotia to look at these orange rocks and these aren't rocks are kind of perfect you have ancient lake beds you have ancient streams even from the margin of an ancient desert all in one small place and so this area we hit really hard we had our eyes to the rocks we had a collecting bags and their Rock hammers and we were ready to fill them with with bones the challenges we didn't fill them with bones we didn't find much of anything and really our luck was to change because of events in town so the breakthrough came when the president of the local Lions Club invited us to be judges for the town's beauty contest so it was up to us to perform this onerous task the problem was in judging the contest and in the celebration afterwards we stayed up way too late in the evening and that late-night reverie had consequences the next day so the next morning got up too late it was high tide and the tides are just so huge here what happens is the tide will lap up against the rocks and what we found is we were stuck we were surrounded by dark volcanic rocks formed from hot lava flows nobody in their right mind would look for fauces here today so you know we skipped rocks rocks weren't the best in the world for skipping my buddy bill had disappeared then I heard his voice he was like Neil you may would come over here and take a look at this I'll never forget those words as long as I'm there holy cow this is the spot I mean it's shut it out more I was 1985 well what happened was Bill was at this point and what he had discovered was that inside these basalt boulders lie seams of this brown sandstone and within this brown sandstone were bones as we chipped away at the rock we uncovered countless fossils there were leg bones teeth even whole jaws this site yielded thousands of pieces of bone from a momentous period in our history found loads of things but the real gem isn't here what you're seeing here is a an upper jaw there's a canine tooth and a series of other smaller tooth behind him these 200 million year old teeth belonged to a creature called a trifle adopt it may look like an insignificant little animal but it's unlike anything alive today now what we have here is really unique kind of animal with a unique mix of features part reptile part mammal SI unit skull and its jaws and its limb bones virtually every feature of its Anatomy this is a creature right on the cusp of the transition from reptile to man a key moment in the evolution of the human body trace your ancestry way back in time and you'll find an ancient relative a fish-like creature that crawled from the water onto land about 375 million years ago animals like this gave rise to amphibians and more important to our story reptiles over time one line of reptiles gave rise to early mammals and eventually to us but before you get the idea this was one smooth ride your reptilian ancestors faced a rocky road they would colonize a hostile land compete for food and territory and even deal with the worst mass extinction the world had ever seen our lives today seem worlds away from this story but every chapter shaped our reptilian ancestors changing their bodies and we can still see those features in our bodies today one of the most surprising is visible in the first few weeks after conception we've come to an IVF clinic to see our inner reptile and septa and dev have graciously allowed us to see their eight week old fetus and what's going on inside let's shrink image a little bit oh look at here there's two in the first few weeks of pregnancy it's almost as if the embryo is a window back in time that reveals our evolutionary history the head this is the heart and this is the tail and here's the yolk sac oh it's like oh wow there you go yeah you don't think about yolk and a human right you're thinking yolk for chicken eggs chicken eggs so thanks to launch organic free-range when you think of yolk you don't think of humans but we have a little yolk sac in early development it gets smaller and smaller as the embryo develops there's no yoke inside it's a remnant from a time when our ancestors laid eggs and that's not the only gift they left us so bright light lying around is the amnion and then the black around the baby is the amniotic fluid the amnion forms a fluid-filled sac that cushions the embryo when a mother's waters break this is the SAC that bursts that little tissue represents something that happened hundreds of millions of years ago and our connection to one of the great events in the history of life 375 million years ago life took a critical turn for most of evolutionary history our ancestors needed to live in water it's where they fed made it and most importantly laid their eggs but when the first vertebrates ventured out onto land into a completely alien world they faced a life-and-death challenge how to prevent their eggs from drying out amphibians got around the problem by returning to water to lay their eggs reptiles evolved a far more radical solution a whole new type of egg they enclosed their embryos in a sack filled with fluid the amnio and then covered it with a protective shell this meant they could lay their eggs on Shore and start to invade the land this innovation opened the floodgates for totally new kinds of animals from snakes and birds to crocodiles and turtles and eventually mammals like us that egg lank history shows up in more than just our Anatomy it's also written in our genes what's really amazing about genes is you can look at their changes that is you can compare the genome of a human to the genome of the reptile to the genome of a chicken and you can ask the question how are they similar and how are they different and that's exactly what researchers did they searched for a particular kind of gene that produces yolk in the egg reptiles and birds have several of these yolk genes that produce gobs of yolk protein to feed the embryo guess what when researchers look to humans where do they find they found we to have yoke genes but they no longer functional they're knocked out their derelicts that's because long ago our ancestors stop relying on yolk to nourish their embryos the yoke genes began to decay until eventually they produced no yoke at all but those broken jeans still lie buried in our genome like fossils from the past so what the genes tell us what DNA tells us is that we have come from an egg-laying animal we're related to egg layers we're related to reptiles we carry the genetic signature of our eggy passed inside of us not all a reptilian past is buried so deep inside of us if you go to the beach there's ample evidence all around you our skin can also be traced back to when our ancestors left the water to combat the dry air on land they have opted a new kind of skin they built up layer upon layer of dead cells to form a watertight barrier around their bodies and you can see these layers most clearly when a snake sheds at the skin we have inherited those same dead skin layers to keep our bodies from drying out but unlike reptiles our skin is filled with its own moisturizers special glands that secrete oils to keep the surface layer hydrated that's why our skin is soft and supple to the touch while a reptiles is dry so our skin arose from an ancient battle against the elements over 300 million years ago but once a reptile ancestors had broken their ties to water a new challenge lay ahead the coastline of South Africa is one of the most dramatic landscapes on the planet but two fossil hunters the real drama lies inside the rocks they're home to one of the richest reptilian boneyards on the planet on the other side of these mountains you'll find a desolate landscape stretching for thousands of miles it's called the kuru the land of great thirst and it holds clues to the evolution of some important parts of our bodies one of the region's best fossil hunters is an old friend of mine Roger Smith you remember the mid-90s when we ran into you guys in the minion yeah that place had thorns like I've never seen I keep so much blood that see 150g of fish there's any one way together thank you the thing about Roger is he loves this place you can't be with him you know for more than five minutes - you realize he lives eats sleeps drinks on these rocks and it's a passion that just is so infectious for Roger this dusty Bush holds evidence of an arms race between predators and prey these is a bone that reveal an escalating struggle among their ancestors as they fought for food and territory on dry land I was really excited to come here I mean I've studied about this place you know for much of my career for decades my expectations were this vast desert you know with with the beautiful exposures of rock you know so when I first came on this place I was kind of disappointed and I see these grasslands I didn't see a whole lot of rock it was not what I expected to the untrained eye we could have been walking over a pile of rubble but look closer and you begin to see evidence of life in these rocks it's the back end of a skull yeah but that's where the nerve cord goes through coming down the spine and then this would be the front of the skull that's right top of the head yeah and then there's now it just dive down yeah Wow because here was skull right in this block the creatures that lived here were very different from anything alive today they look like reptiles but they also had some mammalian features so in paleontologists first found these fossils they named them the mammal-like reptiles and the kuru is covered with their remains I mean over 50 feet here we're stumbling over you know skeleton after skeleton of of you know mammal-like reptile I've never experienced that in my entire career it was it was a stunning morning the fossils found here revealed key changes happening in the bodies of mammal-like reptiles it almost looks like a tibia fibula maybe from the other side among the most telling for our story where changes happening inside their mouths beautiful cusps oh you see them nicely this is yeah hit that and that takes us to one of my favorite topics teeth foreign atomists teeth can reveal a lot about an animal's life one of the great in animists of all time was Baron georges cuvier who lived in paris in the 1800s it was remarkably important remarkably smart and remarkably arrogant in a boast and his boast was show me the tooth of any animal and I can reconstruct its entire skeleton turns out Cuvier was pretty much right and here's the tooth is a huge tooth clearly came from a big animal flat surface on top that animal clearly chews plant material what is a big animal it eats plants an elephant here's another one large canines big scissor-like teeth in the back this creature clearly you know is built to eat meat this is Alliant so teeth contains so many answers to the basic biology of creatures they could tell us what animals eat what they what they likely look like but they can do so much more they can answer mysteries that Cuvier can only dreamed of knowing teeth give us a window into our distant past by telling us how our ancestors lived and evolved Roger wants to show me a particularly striking specimen that's over 250 million years old oh wow ferocious Leos teeth this is the golden opposite these are the carnival's of that time boy the teeth really tell a story on it certainly didn't yeah gorgonopsids might look a bit like t-rex but they lived millions of years before any dinosaur was around this is a fossil that when you see you know exactly how it lived what it did you know this wasn't messing around this picture axes it gorgonopsids were ferocious predators with mouths full of highly specialized teeth and that represents a dramatic change from the much more basic teeth of reptiles most reptiles have sharp egg-shaped teeth that all look really similar these teeth are only great for one thing biter they can't strip or true their food instead they tear off chunks and then swallow them whole the gorgonopsids teeth had come a long way from their reptilian cousins compared to the reptiles before it there was no differentiation of incisors and canines but this elongation of the canine is particularly mammal-like feature and the front teeth were like little needles that came together very very well adapted for flesh tearing so here you you start to see differentiation along the tooth row they're all sort of the same shape but they're different sizes specialized in different ways gorgonopsids had virtual swiss army knives of teeth giant canines for piercing tough skin and incisors for stripping flesh off a carcass so they could avoid swallowing whole bones never before had such menacingly efficient eating machines rule the land these particular Google options were fairly long leaked and the front legs were slightly sprawled the back legs were nice and upright so even in their gait they're somewhat between a reptile remember over millions of years back teeth would also become more specialized they developed extra ridges called cusps for chewing food allowing more efficient digestion and more energy for chasing prey these ancient innovations were the precursors to the molars we have in our mouths today try to mount the ballers couldn't eat the apple mouthing sorry couldn't eat the whatever you call this it's good by the way laundry room guava roll thank you for having ballers it doesn't go ahead I could do this one you know but the humble tooth is very important for our lives today every time you fighting what happened if that is a very complex behavior air front of our teeth the incisors bite into that Apple and they do so in almost a perfect way the teeth des clued in a very fixed pattern a very precise pattern we take for granted how we rely on precise tooth the tooth occlusion except and things go wrong except we crack a tooth isn't about them good look at you kneel and make sure everything is where it's supposed to be and there's nothing in here that isn't suppose wonderfully complex teeth might allow us to have a great bite but it's come at a price you know what makes this interesting thing about is you know the consequences of the reptile mammal transition are the fact that we need a thank you me reptiles don't need dentistry cuz they're producing lots of teeth throughout their lives you know boom boom boom their to produce them they're out of there most reptiles like the snake grow multiple sets of teeth in their lifetime there's a constant stream of new teeth erupting in their mouths but after we lose our baby teeth we're left with one adult set to last us the rest of our lives this may not seem like the best of strategies but there is a plus side it allows us to develop our very precise bite if you're continually replacing your teeth right I mean I think it would be hard to get that you know micron scale occlusion which is so really important to us you're right when we lose a tooth the changes that occur to compensate for the loss of that tooth and the space that it held has a profound effect on our inclusions the reason our rows of teeth match up so precisely is that our ancestors reduced the number of sets that they produced we've made up for that by strengthening our teeth with extra roots and thick enamel to help them last a lifetime along with a little help from our dentists that's name off to take better look when I go to the zoo with my kids the reptile house is not my favorite place yes I would like them in the form you find them it dead yeah dead for my dentist Roger's tales from the Karoo would be the stuff of nightmares but for Roger what happened here is an endlessly fascinating drama to him the rocks and fossils tell the story of a vanished world these rocks were laid down five large Mississippi sized meandering rivers that flowed pretty much throughout the year long ago this landscape looked dramatically different it was wet humid with huge lumbering animals crowding the riverbanks and these larger sation sized carnivores the the gorgonopsids which shed upon them so they were flourishing for nearly 20 million years the gorgonopsids sliced and diced their way across the planet but their reign of terror was about to end 252 million years ago the climate began to change dramatically this Cataclysm wiped out most animal species including the gorgonopsids as we go up here we start to see the change in the rocks from these wet floodplains to the drying out plants dyed soils washed away the kuru became a dead son this is the great end Permian mass extinction the great dying mother of all mass extinctions as they say that's right the mother of all mass extinctions you know when you think about the history of life on Earth if you lay out every fossil that we've ever discovered there's certain periods of time where many creatures just disappear never to be seen again and we call these you know the mass extinctions well these mass extinctions are hugely important for understanding our world today understanding our bodies how they came into being because these mass extinctions don't only just remove creatures but they create new opportunities for the survivors not all our distant relatives were wiped out by the Permian extinction the fossil evidence tells us that some survived on the surface and others burrowed underground layla have a look at this we're excavating an underground burrow this is originally a hole down into the ancient floodplain dug by one of these animals and is been filled with sand and the sand is solidified now and it's what we call a burrow cast this is so cool when you look at this thing it's sort of an s-shaped curve but there's a branch going off of it what's going on with the other shape well that's the interest chamber and and we know from some of our modern burrowing animals that these side chambers are used as latrines or places to store their wastes very sanitary of them I'm impressed Roger thinks that living underground may have helped our ancestors survive in a world of extreme temperatures and it's within barrows like this that a new body feature may have emerged one that is important to all mammals today hair haier rarely fossilizes but Roger sees tantalizing evidence in these ancient barriers that may explain how and why it first evolved oh that is beautiful two specimens that's to throw an accident two juveniles right next to them wow that is just absolutely beautiful do you know how lucky you are to find things like this it was quite a sensation to find it the way there are lying this body beautifully curled around this one lying straight it really looks like the borough has collapsed on these and just preserved them as there was sleeping or hibernating so what do you know about the biology of his creatures just from what we're seeing here the skeletons did Steve pretty sure that it had insectivorous that beetles cockroaches that sort of thing it has a large eyes appears to have been nocturnal or at least in the dawn and dusk where they would come out of their burrows to hunt insects here that's the million-dollar question does their necks not have air we prefer not to reconstruct some accident with a full body hair but we do have evidence around the cheek so whiskers around the lower jaw as well as on the maxilla around here so more as a sensory organ than than a thermoregulation these pits on the skull suggests that thorn accident had whiskers just like a cat or a dog today and although we can't be completely certain there's no evidence that it had hair anywhere else so a hairless guy with whiskers at the front that's right you very much a half-and-half animal if we could go back in time and ventured deep underground we'd see that here they are first evolved as a sensory organ whiskers would have helped for an accident to navigate inside its burrow and when it emerged at dusk they were used to find its way in the dark it's thought that over millions of years our distant relatives got hairier and hairier and by fifty million years after turn accident they had started using hair for a new purpose to keep warm so hair dates back to a whiskered creature that lived in the aftermath of a great extinction complex teeth are linked to predators that battled in long-lost lands and a waterproof skin to a time when our ancestors moved onto land each of these body features is linked to a new chapter in the history of life but hair teeth and skin share an even deeper connection one that lies at the heart of our inner reptile there's a scientist in London named Abigail Tucker who's deciphering this ancient history this is Sponge Bob the bearded dragon and even though we look so different from reptile friends here raesha share lots of common features in our skin skin is not just an outer covering out of it grow body parts is different as hair teeth claws and scales Abigail's passion lies in probing the mystery of how these so-called skin organs form as an example take the tooth from a mouse embryo she cuts out an area of skin tissue from the lower jaw which will eventually transform into a tooth you need really steady hands for this kind of work here I'm using a tungsten needle but for very small tissue we glue an eyelash to a glass stick and use that as a really fine little knife it's starting to go now there we go so here we're looking at a tooth at the bud stage it hasn't really sort of got a tooth shape yet because there was a flat sheet and now it's pushed its way in forming this little bud shape after placing the tooth bud in an incubator Abigail can observe how it grows and what she sees is remarkable the skin folds in upon itself very much like watching origami and now you really can see that that's formed a tooth then it's not just any old tooth it's a molar tooth will is nice cusps developing here and the tooth is just the beginning all our skin organs for hairs glands are formed in a similar way from simple folds in skin tissue we think that this is a really sort of ancient principle it's this sort of folding that was one of the first steps to be able to actually then go on and from a very simple skin to something with lots of different organs developing within it once the process of folding skin was in place it could be modified to produce all kinds of skin organs from a reptile scale to a bird's feather and even that defining body feature of malice mammary glands and what's surprising is the formation of all skin organs is controlled by a single master gene called EDA EDA we know is very important for doing things like controlling how hairy you are therefore how many has you form in a particular area or how many teeth you have and one of those teeth are going to look like it seems to be doing something slightly different in all those different organs but it's absolutely essential in all of them this gene plays a crucial role in building all the vital structures that originate within skin and if you really want to see just how powerful EDA is meet actor Michael Berryman so my big question was looks like we had Star Trek it was fantastic I was the first boolean blue skinned yes I think we were wonderful mutation Michael often plays monsters and aliens in science fiction movies he suffers from a rare mutation in his et a gene that stopped his skin organs from developing properly I had the experience as a very young age I started realizing I had issues with my skin for instance no fingernails I have two nails here one here one here one here one here the rest are not fully developed but there were areas that were just raw meat where there was no dermis on it at all but I also realized that I well I had no teeth the teeth that I had had to be removed I've worn dentures my entire life it also affected me in a matter of which I cannot dissipate body heat which is absolutely huge yeah when you're an actor your inner hot lights I mean what do you do what is it well the acting came about secondary to my chosen profession which was food and beverage I was going to be I had a restaurant I'm a way to be a chef I started to realize that I would overheat quite readily so the only way in which I could anticipate the body heat was actually physically meaning I would go into a freezer that was 20 below zero Wow and and and breathe slowly and deeply to cool the blood in my long so sweat glands fingertips and nails hair yes as well teeth teeth I mean these are all skin organs so you of all people understand just how important skin is yeah yeah I like it what is healthy Michael skin condition demonstrates the crucial role EDA has had in shaping our bodies when we look at evolution no we don't inherit structures from our ancestors I mean I didn't hurt an elbow you know from the fish we found up in the what we inherit are the developmental processes the genes that are the manufacturing processes if you will to build those organs and EDA is a very important part of our evolutionary history from teeth to hair and even skin glands the EDA gene helps shape the bodies of our reptile ancestors and with every change they became more and more like mammals but there is one more critical change that helped complete the transition to mammals and it enriches our lives today a new kind of ear the hearing anatomy of mammals is unique you won't find ear flaps on any reptile our ears are extremely sensitive allowing us to pick up a wide range of sounds from high-pitched squeaks to low distance calls okay and the secret of their incredible sensitivity lies in the tiniest bones in our body these are the three bones of our middle ear all mammals including people have these three bones that sit inside the skull and what they do is they form a little lever system that turns the vibration of air into sound that our nervous system can perceive we like all mammals have three of these bones in our middle ear but reptiles only have one these two extra bones of malleus and incus enable us to amplify sounds that reach our eardrum which is one reason why our hearing is so much better than reptiles this presents us with a simple yet extraordinary puzzle how did our acute sense of hearing using three bones emerge from our reptilian ancestors who used only one for nearly two centuries scientists have been fascinated by this mystery and one of them is my former student Karen Sears so these are the gray short tailed opossum and they have been used in labs for a few decades and are now becoming a much more popular lab organism they're very cute so the opossums like other marsupial mammals the mother gives birth very early compared to what we would call placental mammals things like us like my slick dogs these guys you know they're a month and a half old they're pretty big when they're born they crawl up here and attach to these nipples and they're only a few millimeters in length at that stage they are almost at a embryonic stage of development about the equivalent of a human embryo at about 40 days of development so they don't really have hind limbs they have no hair they can't hear at all at that point these opossums are born just two weeks after mating and Karen can see how their ear bones form at each stage of development from early embryo to adult in order to find the bones she euthanizes the apostles and uses flesh-eating beetle larvae to strip away the tissue and leave bare bones these dermestid beetles are used by labs and museums the world over it takes about 24 hours for them to complete their work Karin is then left with a series of skulls through which she can trace the development of the middle ear bones from embryo to adult and what the skulls reveal is astonishing so what's really surprising is if you look at these early opossum embryos which you see is essentially a reptilian style here with one ear bone those two extra middle ear bones they're gonna be in the ear in the adult they are part of the job and so the jaw joint between the skull and the jaw really looks like that of a reptile and after they're born and while they're growing up those little bones they're gonna be the mammalian middle ear disconnect from the jaw they get relatively smaller and move up to their final position to become a mammal like ear so if you have modern reptiles with one ear bone you have modern mammals with three ear bones I think what the embryos do is they almost provide a link between those two so what we see in the opossums is from that time they're born through their adults they almost go through 300 million years of evolution in terms of their ears how do we know that the bones we used to hear with came from the bones reptiles used to eat with well this amazing transition we see in development from jaw bones to ear bones we also see in the fossil record and we see it fossils from here in South Africa and if we look at some of these primitive mammal like reptiles we see something in the lower jaw that's very different from us because what it has is one bone here which carries the teeth and then there's a bunch of other bones that are sort of moderately sized that sit at the back of the jaw they form the jaw joint itself as you go forward in time what you start to see they're creatures like this which have a larger bone that holds all the teeth and ever smaller bones at the back of the jaw that formed the jaw joint then we hit a point when you get to animals that lived around 200 million years ago more recent in the fossil record you find that they have formed a completely new gorge one that's because the bone that holds the teeth had grown so large it made contact with the skull so over millions of years bones that form the old jaw joint began to shrink and eventually became redundant but instead of being lost altogether these old jaw bones were repurposed to take up a new role in the ear finding out when that transition took place is difficult because the tiny ear bones sit loose in the skull and they are rarely found with the rest of the body but recently a fascinating discovery was made in another part of the world China one of the leading scientists involved in the study is my colleague says sheilo who works in a lab next door to mine Solo is a fabulous anatomist here's a guy who knows the anatomy of the teeth the anatomy of the jaws the anatomy of the ears of reptiles and mammals as well as anybody in the planet furthermore he's able to work with any specimens when the fossil of the first spotted in the field my friend thought is just a pebble he picked it up that he realized the word bones in that pebble it's a fossil after more detailed work we know that it's actually at mammal stone and it's related to the origin of all mammals they named it had Roku diem using a 3d printer Lowe built an enlarged replica of its tiny skull the teeth had cusps like other mammals but it's the lower jaw that really stood out the jaw joint looked remarkably like that of modern mammals which suggests that the old reptilian jaw bones were no longer being used to eat with they had become part of the ear on the inside of the jaw are structured to hold of the year bone this shows us how to code Eames year bones are still attached to the job but the attachment was minimal had Roca diems ear bones were on their way to being completely separate so this 195 million year old creature no bigger than a paperclip had taken a big step towards the kind of hearing we have today along with its specialized teeth that fur coat hydrocodone is regarded as one of the earliest mammals and there was a final surprise another important mammalian feature inside its skull we originally thought the early mammals brain were a lot smaller but a draconian really surprised us has a huge brain in fact it's brain is 50% bigger relative to its body mass than anything before it that's why we called the fossil hydrocodeine and means it got a great big brain the question is why would our ancestors have needed such a big brain in the first place after all they weren't building cities or reading Shakespeare 195 million years ago a big brain helped them to survive in a dangerous nighttime world the rise of a new kind of reptile the dinosaurs forced to the early mammals to become tiny creatures of the night from smelling to hearing to touch in with their whiskers processing so much sensory information who caused their brains to grow they hunted in the dark and hid in their burrows during the day many of them maintained that lifestyle for over 130 million years only when the dinosaurs were wiped out and yet another mass extinction 65 million years ago could the mammals truly emerge and flourish so when the dinosaurs disappeared that's when mammals really took off in a big way they they took the opportunity of the only vacant niches the empty spaces on the land surface and they stepped out under the dinosaurs footprints and and radiated and diversity so in a very real sense we wouldn't be here if it wasn't for the removal or death of the dinosaurs right suddenly our earliest mammalian ancestors were tiny but deep within their bodies just as in ours is an incredible history more you look at faucet the more you look at MVS the more you see that we're repurposed rep top the jaw I'm using to talk with the teeth they used to eat with the ear bones I used to hear with the skin and the structures that appear within it that arose in our reptile past so in a very real sense every day we feel the consequences of our inner reptile torn between his scientific findings and devotion to his faith and to his family Paul Bettany stars as Charles Darwin in a late-night movie over on BBC one in half-an-hour creation is at 11:25 next here on BBC four though delving into the secret history of the brain with an emotional take on life

from the plains of South Africa to the shores of Nova Scotia in the bones of ancient creatures near a skull right in this block and deep inside your DNA lies an incredible story the story of your body and why you&#39;re built the way you are your skin and hair your complex teeth and remarkable sense of hearing can all be traced back to ancient reptiles that once ruled the earth their bodies were shaped by great transitions in the history of life and that legacy still shapes our bodies today my name is Neil Shubin as an anatomist I look at human bodies differently for most people within us I see the ghosts of animals past distant ancestors who shaped our Anatomy in surprising ways prepare yourself for a trip back to an ancient world if you really want to know why you look the way you do it&#39;s time to meet your inner reptile it was here in the small town of pars burrow in Nova Scotia over 25 years ago that I first discovered my inner reptile oh my gosh this was my second home when I was a graduate school this little Main Street I can&#39;t tell you how many times I ripped back and forth a lot of my personal histories on the street back then I was a young eager Harvard graduate student off to lead my very first fossil expedition yeah there&#39;s the bait is it beautiful when you&#39;re catching it a really nice time what makes the Bay of Fundy a special place to hunt for fossils is it&#39;s huge tides they&#39;re the largest in the world in just six hours 100 billion tons of water drains half a mile out to sea these massive tides constantly erode the cliff face making it a wonderful place for exposing new fossils you know we came to Nova Scotia to look at these orange rocks and these aren&#39;t rocks are kind of perfect you have ancient lake beds you have ancient streams even from the margin of an ancient desert all in one small place and so this area we hit really hard we had our eyes to the rocks we had a collecting bags and their Rock hammers and we were ready to fill them with with bones the challenges we didn&#39;t fill them with bones we didn&#39;t find much of anything and really our luck was to change because of events in town so the breakthrough came when the president of the local Lions Club invited us to be judges for the town&#39;s beauty contest so it was up to us to perform this onerous task the problem was in judging the contest and in the celebration afterwards we stayed up way too late in the evening and that late-night reverie had consequences the next day so the next morning got up too late it was high tide and the tides are just so huge here what happens is the tide will lap up against the rocks and what we found is we were stuck we were surrounded by dark volcanic rocks formed from hot lava flows nobody in their right mind would look for fauces here today so you know we skipped rocks rocks weren&#39;t the best in the world for skipping my buddy bill had disappeared then I heard his voice he was like Neil you may would come over here and take a look at this I&#39;ll never forget those words as long as I&#39;m there holy cow this is the spot I mean it&#39;s shut it out more I was 1985 well what happened was Bill was at this point and what he had discovered was that inside these basalt boulders lie seams of this brown sandstone and within this brown sandstone were bones as we chipped away at the rock we uncovered countless fossils there were leg bones teeth even whole jaws this site yielded thousands of pieces of bone from a momentous period in our history found loads of things but the real gem isn&#39;t here what you&#39;re seeing here is a an upper jaw there&#39;s a canine tooth and a series of other smaller tooth behind him these 200 million year old teeth belonged to a creature called a trifle adopt it may look like an insignificant little animal but it&#39;s unlike anything alive today now what we have here is really unique kind of animal with a unique mix of features part reptile part mammal SI unit skull and its jaws and its limb bones virtually every feature of its Anatomy this is a creature right on the cusp of the transition from reptile to man a key moment in the evolution of the human body trace your ancestry way back in time and you&#39;ll find an ancient relative a fish-like creature that crawled from the water onto land about 375 million years ago animals like this gave rise to amphibians and more important to our story reptiles over time one line of reptiles gave rise to early mammals and eventually to us but before you get the idea this was one smooth ride your reptilian ancestors faced a rocky road they would colonize a hostile land compete for food and territory and even deal with the worst mass extinction the world had ever seen our lives today seem worlds away from this story but every chapter shaped our reptilian ancestors changing their bodies and we can still see those features in our bodies today one of the most surprising is visible in the first few weeks after conception we&#39;ve come to an IVF clinic to see our inner reptile and septa and dev have graciously allowed us to see their eight week old fetus and what&#39;s going on inside let&#39;s shrink image a little bit oh look at here there&#39;s two in the first few weeks of pregnancy it&#39;s almost as if the embryo is a window back in time that reveals our evolutionary history the head this is the heart and this is the tail and here&#39;s the yolk sac oh it&#39;s like oh wow there you go yeah you don&#39;t think about yolk and a human right you&#39;re thinking yolk for chicken eggs chicken eggs so thanks to launch organic free-range when you think of yolk you don&#39;t think of humans but we have a little yolk sac in early development it gets smaller and smaller as the embryo develops there&#39;s no yoke inside it&#39;s a remnant from a time when our ancestors laid eggs and that&#39;s not the only gift they left us so bright light lying around is the amnion and then the black around the baby is the amniotic fluid the amnion forms a fluid-filled sac that cushions the embryo when a mother&#39;s waters break this is the SAC that bursts that little tissue represents something that happened hundreds of millions of years ago and our connection to one of the great events in the history of life 375 million years ago life took a critical turn for most of evolutionary history our ancestors needed to live in water it&#39;s where they fed made it and most importantly laid their eggs but when the first vertebrates ventured out onto land into a completely alien world they faced a life-and-death challenge how to prevent their eggs from drying out amphibians got around the problem by returning to water to lay their eggs reptiles evolved a far more radical solution a whole new type of egg they enclosed their embryos in a sack filled with fluid the amnio and then covered it with a protective shell this meant they could lay their eggs on Shore and start to invade the land this innovation opened the floodgates for totally new kinds of animals from snakes and birds to crocodiles and turtles and eventually mammals like us that egg lank history shows up in more than just our Anatomy it&#39;s also written in our genes what&#39;s really amazing about genes is you can look at their changes that is you can compare the genome of a human to the genome of the reptile to the genome of a chicken and you can ask the question how are they similar and how are they different and that&#39;s exactly what researchers did they searched for a particular kind of gene that produces yolk in the egg reptiles and birds have several of these yolk genes that produce gobs of yolk protein to feed the embryo guess what when researchers look to humans where do they find they found we to have yoke genes but they no longer functional they&#39;re knocked out their derelicts that&#39;s because long ago our ancestors stop relying on yolk to nourish their embryos the yoke genes began to decay until eventually they produced no yoke at all but those broken jeans still lie buried in our genome like fossils from the past so what the genes tell us what DNA tells us is that we have come from an egg-laying animal we&#39;re related to egg layers we&#39;re related to reptiles we carry the genetic signature of our eggy passed inside of us not all a reptilian past is buried so deep inside of us if you go to the beach there&#39;s ample evidence all around you our skin can also be traced back to when our ancestors left the water to combat the dry air on land they have opted a new kind of skin they built up layer upon layer of dead cells to form a watertight barrier around their bodies and you can see these layers most clearly when a snake sheds at the skin we have inherited those same dead skin layers to keep our bodies from drying out but unlike reptiles our skin is filled with its own moisturizers special glands that secrete oils to keep the surface layer hydrated that&#39;s why our skin is soft and supple to the touch while a reptiles is dry so our skin arose from an ancient battle against the elements over 300 million years ago but once a reptile ancestors had broken their ties to water a new challenge lay ahead the coastline of South Africa is one of the most dramatic landscapes on the planet but two fossil hunters the real drama lies inside the rocks they&#39;re home to one of the richest reptilian boneyards on the planet on the other side of these mountains you&#39;ll find a desolate landscape stretching for thousands of miles it&#39;s called the kuru the land of great thirst and it holds clues to the evolution of some important parts of our bodies one of the region&#39;s best fossil hunters is an old friend of mine Roger Smith you remember the mid-90s when we ran into you guys in the minion yeah that place had thorns like I&#39;ve never seen I keep so much blood that see 150g of fish there&#39;s any one way together thank you the thing about Roger is he loves this place you can&#39;t be with him you know for more than five minutes - you realize he lives eats sleeps drinks on these rocks and it&#39;s a passion that just is so infectious for Roger this dusty Bush holds evidence of an arms race between predators and prey these is a bone that reveal an escalating struggle among their ancestors as they fought for food and territory on dry land I was really excited to come here I mean I&#39;ve studied about this place you know for much of my career for decades my expectations were this vast desert you know with with the beautiful exposures of rock you know so when I first came on this place I was kind of disappointed and I see these grasslands I didn&#39;t see a whole lot of rock it was not what I expected to the untrained eye we could have been walking over a pile of rubble but look closer and you begin to see evidence of life in these rocks it&#39;s the back end of a skull yeah but that&#39;s where the nerve cord goes through coming down the spine and then this would be the front of the skull that&#39;s right top of the head yeah and then there&#39;s now it just dive down yeah Wow because here was skull right in this block the creatures that lived here were very different from anything alive today they look like reptiles but they also had some mammalian features so in paleontologists first found these fossils they named them the mammal-like reptiles and the kuru is covered with their remains I mean over 50 feet here we&#39;re stumbling over you know skeleton after skeleton of of you know mammal-like reptile I&#39;ve never experienced that in my entire career it was it was a stunning morning the fossils found here revealed key changes happening in the bodies of mammal-like reptiles it almost looks like a tibia fibula maybe from the other side among the most telling for our story where changes happening inside their mouths beautiful cusps oh you see them nicely this is yeah hit that and that takes us to one of my favorite topics teeth foreign atomists teeth can reveal a lot about an animal&#39;s life one of the great in animists of all time was Baron georges cuvier who lived in paris in the 1800s it was remarkably important remarkably smart and remarkably arrogant in a boast and his boast was show me the tooth of any animal and I can reconstruct its entire skeleton turns out Cuvier was pretty much right and here&#39;s the tooth is a huge tooth clearly came from a big animal flat surface on top that animal clearly chews plant material what is a big animal it eats plants an elephant here&#39;s another one large canines big scissor-like teeth in the back this creature clearly you know is built to eat meat this is Alliant so teeth contains so many answers to the basic biology of creatures they could tell us what animals eat what they what they likely look like but they can do so much more they can answer mysteries that Cuvier can only dreamed of knowing teeth give us a window into our distant past by telling us how our ancestors lived and evolved Roger wants to show me a particularly striking specimen that&#39;s over 250 million years old oh wow ferocious Leos teeth this is the golden opposite these are the carnival&#39;s of that time boy the teeth really tell a story on it certainly didn&#39;t yeah gorgonopsids might look a bit like t-rex but they lived millions of years before any dinosaur was around this is a fossil that when you see you know exactly how it lived what it did you know this wasn&#39;t messing around this picture axes it gorgonopsids were ferocious predators with mouths full of highly specialized teeth and that represents a dramatic change from the much more basic teeth of reptiles most reptiles have sharp egg-shaped teeth that all look really similar these teeth are only great for one thing biter they can&#39;t strip or true their food instead they tear off chunks and then swallow them whole the gorgonopsids teeth had come a long way from their reptilian cousins compared to the reptiles before it there was no differentiation of incisors and canines but this elongation of the canine is particularly mammal-like feature and the front teeth were like little needles that came together very very well adapted for flesh tearing so here you you start to see differentiation along the tooth row they&#39;re all sort of the same shape but they&#39;re different sizes specialized in different ways gorgonopsids had virtual swiss army knives of teeth giant canines for piercing tough skin and incisors for stripping flesh off a carcass so they could avoid swallowing whole bones never before had such menacingly efficient eating machines rule the land these particular Google options were fairly long leaked and the front legs were slightly sprawled the back legs were nice and upright so even in their gait they&#39;re somewhat between a reptile remember over millions of years back teeth would also become more specialized they developed extra ridges called cusps for chewing food allowing more efficient digestion and more energy for chasing prey these ancient innovations were the precursors to the molars we have in our mouths today try to mount the ballers couldn&#39;t eat the apple mouthing sorry couldn&#39;t eat the whatever you call this it&#39;s good by the way laundry room guava roll thank you for having ballers it doesn&#39;t go ahead I could do this one you know but the humble tooth is very important for our lives today every time you fighting what happened if that is a very complex behavior air front of our teeth the incisors bite into that Apple and they do so in almost a perfect way the teeth des clued in a very fixed pattern a very precise pattern we take for granted how we rely on precise tooth the tooth occlusion except and things go wrong except we crack a tooth isn&#39;t about them good look at you kneel and make sure everything is where it&#39;s supposed to be and there&#39;s nothing in here that isn&#39;t suppose wonderfully complex teeth might allow us to have a great bite but it&#39;s come at a price you know what makes this interesting thing about is you know the consequences of the reptile mammal transition are the fact that we need a thank you me reptiles don&#39;t need dentistry cuz they&#39;re producing lots of teeth throughout their lives you know boom boom boom their to produce them they&#39;re out of there most reptiles like the snake grow multiple sets of teeth in their lifetime there&#39;s a constant stream of new teeth erupting in their mouths but after we lose our baby teeth we&#39;re left with one adult set to last us the rest of our lives this may not seem like the best of strategies but there is a plus side it allows us to develop our very precise bite if you&#39;re continually replacing your teeth right I mean I think it would be hard to get that you know micron scale occlusion which is so really important to us you&#39;re right when we lose a tooth the changes that occur to compensate for the loss of that tooth and the space that it held has a profound effect on our inclusions the reason our rows of teeth match up so precisely is that our ancestors reduced the number of sets that they produced we&#39;ve made up for that by strengthening our teeth with extra roots and thick enamel to help them last a lifetime along with a little help from our dentists that&#39;s name off to take better look when I go to the zoo with my kids the reptile house is not my favorite place yes I would like them in the form you find them it dead yeah dead for my dentist Roger&#39;s tales from the Karoo would be the stuff of nightmares but for Roger what happened here is an endlessly fascinating drama to him the rocks and fossils tell the story of a vanished world these rocks were laid down five large Mississippi sized meandering rivers that flowed pretty much throughout the year long ago this landscape looked dramatically different it was wet humid with huge lumbering animals crowding the riverbanks and these larger sation sized carnivores the the gorgonopsids which shed upon them so they were flourishing for nearly 20 million years the gorgonopsids sliced and diced their way across the planet but their reign of terror was about to end 252 million years ago the climate began to change dramatically this Cataclysm wiped out most animal species including the gorgonopsids as we go up here we start to see the change in the rocks from these wet floodplains to the drying out plants dyed soils washed away the kuru became a dead son this is the great end Permian mass extinction the great dying mother of all mass extinctions as they say that&#39;s right the mother of all mass extinctions you know when you think about the history of life on Earth if you lay out every fossil that we&#39;ve ever discovered there&#39;s certain periods of time where many creatures just disappear never to be seen again and we call these you know the mass extinctions well these mass extinctions are hugely important for understanding our world today understanding our bodies how they came into being because these mass extinctions don&#39;t only just remove creatures but they create new opportunities for the survivors not all our distant relatives were wiped out by the Permian extinction the fossil evidence tells us that some survived on the surface and others burrowed underground layla have a look at this we&#39;re excavating an underground burrow this is originally a hole down into the ancient floodplain dug by one of these animals and is been filled with sand and the sand is solidified now and it&#39;s what we call a burrow cast this is so cool when you look at this thing it&#39;s sort of an s-shaped curve but there&#39;s a branch going off of it what&#39;s going on with the other shape well that&#39;s the interest chamber and and we know from some of our modern burrowing animals that these side chambers are used as latrines or places to store their wastes very sanitary of them I&#39;m impressed Roger thinks that living underground may have helped our ancestors survive in a world of extreme temperatures and it&#39;s within barrows like this that a new body feature may have emerged one that is important to all mammals today hair haier rarely fossilizes but Roger sees tantalizing evidence in these ancient barriers that may explain how and why it first evolved oh that is beautiful two specimens that&#39;s to throw an accident two juveniles right next to them wow that is just absolutely beautiful do you know how lucky you are to find things like this it was quite a sensation to find it the way there are lying this body beautifully curled around this one lying straight it really looks like the borough has collapsed on these and just preserved them as there was sleeping or hibernating so what do you know about the biology of his creatures just from what we&#39;re seeing here the skeletons did Steve pretty sure that it had insectivorous that beetles cockroaches that sort of thing it has a large eyes appears to have been nocturnal or at least in the dawn and dusk where they would come out of their burrows to hunt insects here that&#39;s the million-dollar question does their necks not have air we prefer not to reconstruct some accident with a full body hair but we do have evidence around the cheek so whiskers around the lower jaw as well as on the maxilla around here so more as a sensory organ than than a thermoregulation these pits on the skull suggests that thorn accident had whiskers just like a cat or a dog today and although we can&#39;t be completely certain there&#39;s no evidence that it had hair anywhere else so a hairless guy with whiskers at the front that&#39;s right you very much a half-and-half animal if we could go back in time and ventured deep underground we&#39;d see that here they are first evolved as a sensory organ whiskers would have helped for an accident to navigate inside its burrow and when it emerged at dusk they were used to find its way in the dark it&#39;s thought that over millions of years our distant relatives got hairier and hairier and by fifty million years after turn accident they had started using hair for a new purpose to keep warm so hair dates back to a whiskered creature that lived in the aftermath of a great extinction complex teeth are linked to predators that battled in long-lost lands and a waterproof skin to a time when our ancestors moved onto land each of these body features is linked to a new chapter in the history of life but hair teeth and skin share an even deeper connection one that lies at the heart of our inner reptile there&#39;s a scientist in London named Abigail Tucker who&#39;s deciphering this ancient history this is Sponge Bob the bearded dragon and even though we look so different from reptile friends here raesha share lots of common features in our skin skin is not just an outer covering out of it grow body parts is different as hair teeth claws and scales Abigail&#39;s passion lies in probing the mystery of how these so-called skin organs form as an example take the tooth from a mouse embryo she cuts out an area of skin tissue from the lower jaw which will eventually transform into a tooth you need really steady hands for this kind of work here I&#39;m using a tungsten needle but for very small tissue we glue an eyelash to a glass stick and use that as a really fine little knife it&#39;s starting to go now there we go so here we&#39;re looking at a tooth at the bud stage it hasn&#39;t really sort of got a tooth shape yet because there was a flat sheet and now it&#39;s pushed its way in forming this little bud shape after placing the tooth bud in an incubator Abigail can observe how it grows and what she sees is remarkable the skin folds in upon itself very much like watching origami and now you really can see that that&#39;s formed a tooth then it&#39;s not just any old tooth it&#39;s a molar tooth will is nice cusps developing here and the tooth is just the beginning all our skin organs for hairs glands are formed in a similar way from simple folds in skin tissue we think that this is a really sort of ancient principle it&#39;s this sort of folding that was one of the first steps to be able to actually then go on and from a very simple skin to something with lots of different organs developing within it once the process of folding skin was in place it could be modified to produce all kinds of skin organs from a reptile scale to a bird&#39;s feather and even that defining body feature of malice mammary glands and what&#39;s surprising is the formation of all skin organs is controlled by a single master gene called EDA EDA we know is very important for doing things like controlling how hairy you are therefore how many has you form in a particular area or how many teeth you have and one of those teeth are going to look like it seems to be doing something slightly different in all those different organs but it&#39;s absolutely essential in all of them this gene plays a crucial role in building all the vital structures that originate within skin and if you really want to see just how powerful EDA is meet actor Michael Berryman so my big question was looks like we had Star Trek it was fantastic I was the first boolean blue skinned yes I think we were wonderful mutation Michael often plays monsters and aliens in science fiction movies he suffers from a rare mutation in his et a gene that stopped his skin organs from developing properly I had the experience as a very young age I started realizing I had issues with my skin for instance no fingernails I have two nails here one here one here one here one here the rest are not fully developed but there were areas that were just raw meat where there was no dermis on it at all but I also realized that I well I had no teeth the teeth that I had had to be removed I&#39;ve worn dentures my entire life it also affected me in a matter of which I cannot dissipate body heat which is absolutely huge yeah when you&#39;re an actor your inner hot lights I mean what do you do what is it well the acting came about secondary to my chosen profession which was food and beverage I was going to be I had a restaurant I&#39;m a way to be a chef I started to realize that I would overheat quite readily so the only way in which I could anticipate the body heat was actually physically meaning I would go into a freezer that was 20 below zero Wow and and and breathe slowly and deeply to cool the blood in my long so sweat glands fingertips and nails hair yes as well teeth teeth I mean these are all skin organs so you of all people understand just how important skin is yeah yeah I like it what is healthy Michael skin condition demonstrates the crucial role EDA has had in shaping our bodies when we look at evolution no we don&#39;t inherit structures from our ancestors I mean I didn&#39;t hurt an elbow you know from the fish we found up in the what we inherit are the developmental processes the genes that are the manufacturing processes if you will to build those organs and EDA is a very important part of our evolutionary history from teeth to hair and even skin glands the EDA gene helps shape the bodies of our reptile ancestors and with every change they became more and more like mammals but there is one more critical change that helped complete the transition to mammals and it enriches our lives today a new kind of ear the hearing anatomy of mammals is unique you won&#39;t find ear flaps on any reptile our ears are extremely sensitive allowing us to pick up a wide range of sounds from high-pitched squeaks to low distance calls okay and the secret of their incredible sensitivity lies in the tiniest bones in our body these are the three bones of our middle ear all mammals including people have these three bones that sit inside the skull and what they do is they form a little lever system that turns the vibration of air into sound that our nervous system can perceive we like all mammals have three of these bones in our middle ear but reptiles only have one these two extra bones of malleus and incus enable us to amplify sounds that reach our eardrum which is one reason why our hearing is so much better than reptiles this presents us with a simple yet extraordinary puzzle how did our acute sense of hearing using three bones emerge from our reptilian ancestors who used only one for nearly two centuries scientists have been fascinated by this mystery and one of them is my former student Karen Sears so these are the gray short tailed opossum and they have been used in labs for a few decades and are now becoming a much more popular lab organism they&#39;re very cute so the opossums like other marsupial mammals the mother gives birth very early compared to what we would call placental mammals things like us like my slick dogs these guys you know they&#39;re a month and a half old they&#39;re pretty big when they&#39;re born they crawl up here and attach to these nipples and they&#39;re only a few millimeters in length at that stage they are almost at a embryonic stage of development about the equivalent of a human embryo at about 40 days of development so they don&#39;t really have hind limbs they have no hair they can&#39;t hear at all at that point these opossums are born just two weeks after mating and Karen can see how their ear bones form at each stage of development from early embryo to adult in order to find the bones she euthanizes the apostles and uses flesh-eating beetle larvae to strip away the tissue and leave bare bones these dermestid beetles are used by labs and museums the world over it takes about 24 hours for them to complete their work Karin is then left with a series of skulls through which she can trace the development of the middle ear bones from embryo to adult and what the skulls reveal is astonishing so what&#39;s really surprising is if you look at these early opossum embryos which you see is essentially a reptilian style here with one ear bone those two extra middle ear bones they&#39;re gonna be in the ear in the adult they are part of the job and so the jaw joint between the skull and the jaw really looks like that of a reptile and after they&#39;re born and while they&#39;re growing up those little bones they&#39;re gonna be the mammalian middle ear disconnect from the jaw they get relatively smaller and move up to their final position to become a mammal like ear so if you have modern reptiles with one ear bone you have modern mammals with three ear bones I think what the embryos do is they almost provide a link between those two so what we see in the opossums is from that time they&#39;re born through their adults they almost go through 300 million years of evolution in terms of their ears how do we know that the bones we used to hear with came from the bones reptiles used to eat with well this amazing transition we see in development from jaw bones to ear bones we also see in the fossil record and we see it fossils from here in South Africa and if we look at some of these primitive mammal like reptiles we see something in the lower jaw that&#39;s very different from us because what it has is one bone here which carries the teeth and then there&#39;s a bunch of other bones that are sort of moderately sized that sit at the back of the jaw they form the jaw joint itself as you go forward in time what you start to see they&#39;re creatures like this which have a larger bone that holds all the teeth and ever smaller bones at the back of the jaw that formed the jaw joint then we hit a point when you get to animals that lived around 200 million years ago more recent in the fossil record you find that they have formed a completely new gorge one that&#39;s because the bone that holds the teeth had grown so large it made contact with the skull so over millions of years bones that form the old jaw joint began to shrink and eventually became redundant but instead of being lost altogether these old jaw bones were repurposed to take up a new role in the ear finding out when that transition took place is difficult because the tiny ear bones sit loose in the skull and they are rarely found with the rest of the body but recently a fascinating discovery was made in another part of the world China one of the leading scientists involved in the study is my colleague says sheilo who works in a lab next door to mine Solo is a fabulous anatomist here&#39;s a guy who knows the anatomy of the teeth the anatomy of the jaws the anatomy of the ears of reptiles and mammals as well as anybody in the planet furthermore he&#39;s able to work with any specimens when the fossil of the first spotted in the field my friend thought is just a pebble he picked it up that he realized the word bones in that pebble it&#39;s a fossil after more detailed work we know that it&#39;s actually at mammal stone and it&#39;s related to the origin of all mammals they named it had Roku diem using a 3d printer Lowe built an enlarged replica of its tiny skull the teeth had cusps like other mammals but it&#39;s the lower jaw that really stood out the jaw joint looked remarkably like that of modern mammals which suggests that the old reptilian jaw bones were no longer being used to eat with they had become part of the ear on the inside of the jaw are structured to hold of the year bone this shows us how to code Eames year bones are still attached to the job but the attachment was minimal had Roca diems ear bones were on their way to being completely separate so this 195 million year old creature no bigger than a paperclip had taken a big step towards the kind of hearing we have today along with its specialized teeth that fur coat hydrocodone is regarded as one of the earliest mammals and there was a final surprise another important mammalian feature inside its skull we originally thought the early mammals brain were a lot smaller but a draconian really surprised us has a huge brain in fact it&#39;s brain is 50% bigger relative to its body mass than anything before it that&#39;s why we called the fossil hydrocodeine and means it got a great big brain the question is why would our ancestors have needed such a big brain in the first place after all they weren&#39;t building cities or reading Shakespeare 195 million years ago a big brain helped them to survive in a dangerous nighttime world the rise of a new kind of reptile the dinosaurs forced to the early mammals to become tiny creatures of the night from smelling to hearing to touch in with their whiskers processing so much sensory information who caused their brains to grow they hunted in the dark and hid in their burrows during the day many of them maintained that lifestyle for over 130 million years only when the dinosaurs were wiped out and yet another mass extinction 65 million years ago could the mammals truly emerge and flourish so when the dinosaurs disappeared that&#39;s when mammals really took off in a big way they they took the opportunity of the only vacant niches the empty spaces on the land surface and they stepped out under the dinosaurs footprints and and radiated and diversity so in a very real sense we wouldn&#39;t be here if it wasn&#39;t for the removal or death of the dinosaurs right suddenly our earliest mammalian ancestors were tiny but deep within their bodies just as in ours is an incredible history more you look at faucet the more you look at MVS the more you see that we&#39;re repurposed rep top the jaw I&#39;m using to talk with the teeth they used to eat with the ear bones I used to hear with the skin and the structures that appear within it that arose in our reptile past so in a very real sense every day we feel the consequences of our inner reptile torn between his scientific findings and devotion to his faith and to his family Paul Bettany stars as Charles Darwin in a late-night movie over on BBC one in half-an-hour creation is at 11:25 next here on BBC four though delving into the secret history of the brain with an emotional take on life

Transcript for:Your inner Reptile

Transcript for:
Your inner Reptile