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of all the animals that live on our planet one extraordinary group dominates
it has produced the largest the fastest the most intelligent creatures that have
ever lived they're known as the vertebrates
and they all share one vital feature a backbone
I'm travelling back in time to look for the key advances that drove their
remarkable success so far I have seen the vertebrates grow from tiny origins
to dominate the oceans colonize the land and take to the skies
this program I'm going to track the rise of a whole new branch of vertebrate life
the most complex animals yet to appear on earth they started as a group of
twenty little creatures scarcely bigger than my little finger nocturnal animals
but they were to develop into some of the biggest creatures the planet has
ever seen it's a group that also contains us this is a story of the
mammals I want to investigate how the mammals acquired a new set of key
features that allowed them to thrive in every corner of our planet features we
also have inherited we will find the evidence in a series of thrilling fossil
discoveries and in living animals
with the latest scientific analysis we'll be able to bring our ancient
ancestors back to life
today animals with backbones dominate our pallets of land the air and at sea
but how did that evolutionary takeover come about there's been lots of gaps in
the story but in recent decades exciting new discoveries have been made here in
China and I'm here to look at them the rocks of China are yielding up the
elusive missing links in the vertibird story
ancient creatures preserved as fossils
to find new evidence from the very start of the mammal story I'm traveling to the
south of China and the province of Jana
fossils found here can reveal the kind of world those first mammals encountered
and the kind of animals they had to compete with to gain a foothold and
survive this area of southern China is known as the liu fung basin and 180
million years ago it was a vast natural hollow into which waters from all the
surrounding hills flowed and with those streams came sediment which is now this
and they also brought the bodies of the animals that lived in those hills
including creatures like this one a dinosaur
excavators have uncovered hundreds of specimens like this one in the
surrounding countryside local museum is crowded with one of the largest
collections of complete dinosaur skeletons in the world
but a unique discovery here has revealed some of the earliest evidence for the
origins of the animal group that would eventually succeed them at the same time
the dinosaurs were roaming in this area there was another very different
creature evolving in their shadow one that was on a much much smaller scale
paleontologist one cow has spent his life exploring these hills he's used to
finding the remains of large dinosaurs but on this hilltop site he and his
colleagues discovered something that didn't match the usual profile homina
Thomson out to be alive I came to collect fossils with my colleagues in
this area here at the time and was not like this there were no crops growing
here after looking around we followed this little slope we found a sniff or so
about 2 centimeters long Johanna we thought it might be something special
so we send it to the lab in Beijing to clean it up
I have traveled north to Beijing to see when house discovery for myself it's now
stored in one of the world's leading institutes for the study of fossils and
this is it and what seems extraordinary near miraculous to me
is that anybody should notice that a tiny tiny little thing like this is
actually a fossil but a fossil it is it's the head of a tiny animal there's
the tip of its nose that's the back of its neck and you
could also see it's got an eye socket it's called Hydra Co diem if I turn it
upside down you can see the bottom of its jaw it might be the skull of a
really minut little reptile but it's not because reptiles have simple cone-shaped
teeth and this one has a tooth that is rather different that has the shape of a
little insect eating mammals too so this is one of the earliest mammal fossils we
know of and to that extent it's the ancestor of all mammals alive today
including ourselves
as such Hendrik odium holds a key position in the evolutionary story of
the backboned animals the vertebrates
the first creature of the beginnings of a backbone lived over 500 million years
ago then fish amphibians and reptiles evolved it's from the reptile line that
the first mammals emerge the Hatrack odium fossil dates to 195 million years
ago these simple origins led to the vast diversity of mammals we see around us
today over 5700 living species have adapted to survive in every corner of
the planet
we humans dominate and are the most numerous of the large mammals
this astonishing journey was built on a series of key evolutionary advances that
began in very early forms like Patrick odium we only have its cow but we can
work out from modern mammals what the rest of its skeleton was like
so how did this minut animal gain a foothold in the age of the dinosaurs
good main city in southern China I've come to this late night market to
observe one of the first crucial steps in the mammal story the development of
an amazing feature that gave them a key advantage but only after dark the
mammals found a niche for themselves not so much in space as in time at night
when the reptiles are not active a simple experiment with two pets that
happen to be for sale in the market tonight can demonstrate why this is so
this is a thermal camera and it will show a cold body as a black or very dark
so this lizard which is on the table is coal Valley and it appears to be very
much the same temperature as the table reptiles get much of their energy
directly from the Sun as warmth but there is no Sun at night as a
consequence it's scarcely got the energy to move this puppy on the other hand is
very active and when you look at him with the camera you can see that his
body is very warm indeed and he mustn't eat the lizard the mammals very early in
their history developed the remarkable ability to generate heat within their
bodies they became warm-blooded and they achieved this by driving their
metabolism at a much higher rate but to do that you need extra fuel extra food
a reptile like a lizard can go for many days without eating but if a mammal is
denied its food for several days it will die so in order to keep their fuel bills
down the mammals use the technique familiar to any householder insulation
they coated their bodies as this puppy has with
with warm blood and the covering of hair Patrick odium was free to hunt for
insects in the cool of the night but now came a new challenge to find its way
around in pitch darkness detailed analysis of heidrick odium skull is
revealing remarkable new evidence of a set of ingenious solutions to this
problem the clues are tiny and invisible to outside scrutiny but professor
Scheele or an expert on early mammals is using a micro CT scanner to unlock the
skulls in the secrets X rays penetrate the rock and pick out detailed fossil
structures within a computer then build a 3d model of the bones and in
particular the cavity that once held the brain
professor law is able to identify an area that is clearly much larger than
its equivalent in the reptile if you look at the CT scan here you can tell
that despite a tiny little skull the bring is enormous but one of the most
striking features of this particular fossil is that a has very large
olfactory bulbs when you say olfactory bones those are the part of the brain
that detects smell correct this mammal must have had very refined sensory
detecting of all kinds of smell allowing it to be active in the dark of the night
this powerful sense of smell would have helped Heydrich odium pick out the scent
of the worms and insects in federal
the scans have also revealed a radical advance in the second sense that vital
in the dark hearing the telltale clue lies
surprisingly in Heydrich odium jaw one very interesting feature that's so
unique about this fossil mammal is very flat geo the surface on the inside of
the jaw is perfectly flat in the primitive Prima Marion forms there are
big booths grooves like these indicate the presence of two key bones that are
attached to the jaw of a reptile seen here in green and red third bone colored
blue transmits sound waves in each ear in a mammal there has been a truly
amazing evolutionary development the two jaw bones have shifted to form with the
third the middle ear
this three-pound arrangement opens up a range of higher pitched frequencies that
a reptile cannot hear
it's the system we have inherited inside our years so here in hydrocodeine we get
the earliest indication that the three years bonds so important for our hearing
have already originated witness possible
now ears could pick up the faintest rustle in the undergrowth and guide
Heydrich odium to any insects moving nearby professor Lewis analysis has also
identified a spectacular advance in the third key sense it also has very large
areas responsible for skin touch for touch
that's right mammals have hairs one of the most important function of the hair
is actually to gave us the sensory touch and this animal has already developed
that
the use of hairs as touch sensors is perhaps most obvious from the way modern
mammals use their whiskers this brown rat relies on them for finding its way
around at night or underground at the base of each of those long hairs on its
nose there is a nerve receptor and whenever the hair is touched the message
is sent up to the rats brain it's not just the whiskers though hairs all over
its body are wired up to its nervous system this creates a sensory bubble
allowing the rat to map the world around it just by using its hairs a hundred and
ninety five million years ago the hairs on Heydrich odium must have been wired
up in the same way
this remarkable little creature now had a whole array of new powers with which
to meet the challenges of the night
a heightening of the senses powered by growing brain had enabled the early
mammals to survive in the shadow of the dinosaurs and then they also developed a
radical new way of nourishing their young
we can look for clues to this next crucial step in our evolutionary story
in Australia not in fossils but in the bodies of two highly unusual creatures
that live here
the first is the platypus which uses it's rubbery beak like a
radar transmitter to hunt for shrimp or mollusks
underwater
and the second is the Echidna which forages for ants and termites on man the
platypus an echidna are the only two survivors of a group of mammals called
the monotremes
trace their genetic line back and we discover they split from all other
mammals around 200 million years ago
because they retain traits from that distant time they give us a remarkable
insight into very early mammals like how to code 'i'm the most extraordinary
feature of all is one that no other modern mammal has retained they lay eggs
this echidna egg is tiny only about the size of a marble the hatching process
itself has only rarely been captured on film
these are newly hatched platypus young filmed in their mothers burrow
they're only about the size of jellybeans
the early mammals must have laid eggs in the same way and they inherited this
trait from their reptile ancestors
this is a view inside a reptile egg the embryo feeds on a supply of highly
nutritious yolk by the time reptiles hatch they're sufficiently
well-developed to go looking for their own food but the platypus and the
Echidna are very different their smaller eggs contain only a small amount of yolk
so they're young hatched in a far less developed state they need a lot more
nourishment if they're going to grow and survive but at Healesville sanctuary
near Melbourne we can find delightful evidence that platypus young do develop
with great success without having to leave their mothers burrow four months
after it hatched a youngster is emerging for the first time it has grown from a
tiny hatchling to near adult size and that is thanks to an amazing form of
nourishment that is a defining feature of all mammals milk
this rich mixture of proteins fats carbohydrates and minerals losses from
the bellas of female platypus and the Echidna rather like sweat and provides
their young with everything they need to grow it's likely that early mammals like
how to code him nourish their young in the same way first with a reduced amount
of you and then with milk so what could explain this hugely
significant step new genetic analysis is providing the answer dr. Hendrix Iceland
has been using the platypus to investigate the DNA of the early
mammals the platypus is really an amazing creature it's really this
crossover of a mammal and AB reptile science and so it has a key position in
the evolutionary analysis of all mammals first he looked at the reduction in egg
yolk reptiles have at least three genes that together manufacture their large
yolk dr. Joycelyn has found that the Platypus DNA records a dramatic change
taking place in the early mammals we found only one egg yolk gene in the
Platypus genome that really was functional and was producing the egg
yolk protein presumably the fact that there was any one gene which was
producing yolk accounts the fact that the Platypus egg is has more exactly the
early mammals must have started to switch off their yolk genes and dr.
Kai's Minh has made a second key discovery
the trigger for this shutdown was the arrival of the genes to produce milk so
you have the milk genes appearing that then allow for the subsequent loss of
the egg yolk death the mammals began to favor milk over egg yolk as a way to
nourish their young and that is because milk has one key advantage it's on tap
and that means that none of it need go to waste and there's no limit on how
much and for how long a mother can feed her young wall body's powerful senses
and now milk had allowed the early mammals like how to code IAM to gain a
foothold while the reptiles still ruled
but combining egg-laying with milk feeding brought a new challenge a mammal
mother could not leave the eggs to hatch by themselves as most reptiles do today
she had to stay with them
then came a truly astonishing solution the egg instead of being laid was
retained inside the body and started its development there so that the young was
born alive
apart from the monotremes there are two other major groups of modern mammals
around today marsupials and placentals it's thought that they first appeared
around a hundred and sixty million years ago both give birth to live young but
they do so in two very different ways
spectacular Fossil Beds in the north of China have in recent years produced the
earliest ancestors yet found of these two groups
this is Loughnane province 125 million years ago
volcanoes were erupting in this region
they left layer upon layer of yellow ash in these rocks
excavations have revealed the fossilized remains of animals trapped in these
layers and preserved in extraordinary detail this is a fossil that's been
called sino Delphis its skeleton is very easily seen but around its skeleton
there are dark marks and close examination shows that their fur so we
can be pretty sure that this is the fossil of a mammal but it's skeleton and
particular its teeth make you clear that it was a marsupial marsupials were once
distributed throughout the globe but most of aound today in Australia and
they allow us to see how their ancestors began to bring their young into the
world alive this is a sanctuary for breeding endangered species of wallaby
through the use of foster mother's
running the conservation project is dr. David Tackett of the University of
Adelaide today he and his team are conducting a health check on a newly
arrived baby wallaby known as a Joey
this Joey looks like it's about 2 grams so about 16 days old so 16 days ago this
young would have been born Palmer super young were born premature
so it's ears are folded and the eyes are closed
instead of being enclosed in an egg when leaving its mother like a baby echidna
this Joey emerged directly from its mother's birth canal just 30 days after
conception its front legs are more developed and strong enough for it to
pull itself up through the fur and wriggle inside a feature that is unique
to Marcio pills a pouch here there's a highly developed milk delivery system
the milk is channeled through long fleshy tubes teats a wallaby mother has
four of them and can even feed young of different ages at the same time she
might have young just newly born attached to one T and she'll have a
young of its head in the pH feeding from another tape and those two teats will be
producing a milk that is of different consistency so so one are we to nourish
a newborn young and the others to nourish a young that's almost ready to
wean it's a great system the long teats also give the young away
to cling on to their mother as she moves around
this opossum is a marsupial that lives in South America and it has no pouch its
young seal their mouth so tightly around the teats they stay firmly attached this
may well be how the early marsupials like sino Delphis carried their young
around they were now no longer tied to a nest or a burrow
but the egg-laying mammals but this method had one obvious drawback
outside their mother's body the newborn young were vulnerable to accident and
exposed to disease
in China new evidence is emerging for the pioneers of an even more radical
solution at the same time as the marsupials appeared another branch
developed on the family tree of the mammals a branch that we belong to and
it had a way of nurturing their young before birth
I'm traveling to Beijing and it's Museum of Natural History to see remarkably
early evidence for this group
this is it it's been called Jeremiah which means Jurassic mother it's bones
and in particular its teeth identified as a member of the mammal group to which
we belong but the key thing about it is it's date
it's Jurassic a hundred and sixty million years old and this makes
Jeremiah the earliest creature we know of that could have nurtured its young in
a revolutionary new way
Jun Amaya lived and hunted in a world still dominated by the dinosaurs but it
may have had a powerful advantage the ability for a mother to carry her young
not outside her body like the marsupials but inside in a womb to understand how
Jeremiah could have achieved this we can look at one of its living descendants
the one that carries its young inside for the longest period of all mammals
the elephant this is da cunha she is part of a breeding program at Melbourne
Zoo in Australia and she is pregnant dr. Thomas Hildebrand one of the world's
leading experts in mammal birth is monitoring progress with an ultrasound
scanner we study the longest pregnancy on the planet which elephant half was 22
months and so ultrasone allows us non-invasively to see all the
differences during the fetal development which is quite exciting and was never
done before more detailed 3d scans give us a spectacular view inside her womb
even at an early stage of development the baby's trunk is visible and moving
but we can also see the presence of a remarkable organ that evolved to make it
possible to feed a developing baby before birth
the presenter this baby elephant was born in the zoo just three weeks ago and
it's placenta has been saved for analysis here we have the elephant at
center of the baby which is running outside say at these bloodless its forms
the umbilical cord allowing to move all the nutrients to the baby and take all
the waste material away on the underside is a ring of sponge like tissue that
attaches to the lining of the mother's womb and allows nutriment to flow in and
waste to flow out but it also operates as a life-saving barrier because half of
the unborn baby's genes are from its father it was under threat in the womb
from its mother's immune system the baby is foreign materials and alien
to the mother and what be rejected if there is not this very specific system
engaged which protects the baby against the maternal immune system because the
tissues of the presenter are composed of cells from both mother and baby and the
two blood supplies never mix the baby is protected this allows it to remain
inside the womb until it's ready to survive in the outside world mammals
equipped with this miracle of evolutionary engineering are known as
presenters
it's likely that their earliest ancestors like Jeremiah were the first
to rear their young inside their bodies a hundred and sixty million years ago by
now the mammals had acquired all the key characteristics that define them as a
group hairy bodies milk and live birth and this combination would eventually
provide them with the platform for an astonishing explosion in diversity for
millions of years they remain the small shoe light creatures that we've
encountered so far skittering about around the feet of the dinosaurs but
then came a sudden global catastrophe that threatened to bring the whole
history of the vertebrates to a sudden end
a meteor impact that sent shockwaves around the world and coincided with the
extinction of the dinosaurs we're still not exactly sure why the dinosaurs
disappeared but certainly 65 million years ago they disappear from the fossil
record many other vertebrates survived and for them the dominance of the world
was now up for grabs
scientists are unearthing stunning evidence in Germany for how the mammals
seized this opportunity this natural hollow is known as the Messel pit an
entire community of animals was entombed here by an extraordinary freak of nature
47 million years ago this was a lake fringed by a subtropical rainforest but
it's waters held a dark secret the lake was in fact a flooded volcanic
crater it's thought that lethal carbon dioxide gas released from its depths
periodically bubbled to the surface killing the creatures that drank it in
Shaw or flew over its waters
their bodies drifted down to the bottom to be entombed in the muddy sediment
it's now one of the most remarkable fossil excavation sites in the world
painstaking work is uncovering creatures sealed inside layers of the ancient lake
bed they're preserved in extraordinary detail
it's a unique snapshot of life after the dinosaurs there are reptiles like
lizards and snakes here to our ancient Birds the vertebrate group that evolved
from the dinosaurs but the biggest changes are amongst the mammals they
have started to specialize this perhaps is the least of them
it's an insect eater a creature like a large shrew and its teeth are still
relatively simple but then there are also animals like this and this has very
big knowing front teeth this is an early rodent creature like a rat and then
bigger still is this animal this has grinding molar teeth at the
back and long legs it's beginning to stand up on its toes this is an early
horse and perhaps the most specialized in remarkable hor of this still very
early date is this extraordinary as wrestling this as you can see is a bat
and the preservation is so remarkable that the skin can be easily seen not
only on its forelegs which turns them into wings but even you can see this
large ear on the side of its head would suggest that already it was beginning to
echolocate to hear its own calls so it navigates during flying
the mammals were displaying an extraordinary ability to rapidly adapt
their bodies to fill the range of niches left vacant by the death of the
dinosaurs they had new opportunities but they also faced a new evolutionary
pressure climate change 10 million years of gradual global warming had triggered
a surge in plant life the land became covered in forests that grew ever denser
and darker new mammals emerged with new features that helped them to thrive in
this changed environment features that would have huge significance for humans
this is an early member of the group of mammals that was going to produce us
this is an early primate and you can see that on its front legs its hands they
have an opposable thumb so it could grasp and the same on the back legs in
the big toe is also opposable so this animal was a climber
the primates could now reach food that was high up in trees and it's thought
that it was a new type of food that triggered another astonishing advance in
their bodies the major improvement in sight dr.
Sandra angles is part of a team investigating the diet of the fossilized
primate from the meso pit remarkably she's able to examine the preserved
contents of its gut
we have particles of the last meal of this primate and we analyzed it with
very high magnification and we found the oval outline of a seed which is part of
a fruit and because we found it in the gut of this primate we know that it fed
on fruit 3d scans of its teeth make it clear that food was a major part of its
diet this animal was a specialized food eater
if we take a closer look to the shape of the teeth
we have structures as deep essence or rounder cusps that are the right tools
to break up fruit
47 million years ago large fleshy fruit like this had only recently been
developed by plants it was one of the ways in which they had adapted to the
new dense forest environments many early plants relied on the wind should the
strip of their seeds but in the forest there was little or no wind so they had
a problem they solved it by recruiting the help of birds and they did that by
wrapping their seeds in an edible sweet flesh fruit burbs carried the seeds in
their stomachs and eventually deposited them elsewhere in the forest the
primates had clearly began to exploit this cozy arrangement but to take full
advantage they needed to improve their vision during the age of the dinosaurs
when the mammals were largely nocturnal they had developed a better night vision
but sacrificed the feature not needed in the dark the ability to see cover today
most mammals still see the world largely in black and white but the reptiles and
their cousins the birds retained excellent color vision
and the food bearing plants had evolved a signaling arrangement to match there's
no point in having your seeds distributed before they're fully formed
so the plants evolved a color coding system to show when that was this plant
for example here is a young fruit still growing its flesh is hard and bitter and
it's green but this fruit is fully formed its flesh is good to eat the soft
and the seed within is ready to go and red to spot a flash of red color and
amongst the green foliage is easy for a bird or reptile
but for a mammal with a nighttime vision red and green are indistinguishable then
remarkably some of the primates manage defeat no other mammal has achieved
they put evolution into reverse and reacquired color vision the common
ancestor of this monkey and of me lived up in the trees in the daylight and they
quickly evolves the ability see color and therefore to know which was ripened
which was unripe fruit and so take advantage of the system as it already
had been worked out between the birds and the plants let's just see what she
thinks about that which of those do you like there is it
after the dinosaur extinctions of 65 million years ago the mammals were using
their spectacular adaptability to evolve and diversify at an astonishing rate
in the process they laid the foundations for the major mammal groups we see today
but then around 47 million years ago came a new set of problems
the Earth's climate changed yet again many places became drier and where that
happened the forests thinned out and was replaced by low scattered bushes and
grass and those new environments presented new challenges to animals and
ushered in the age of the mammal monsters
scientists are finding stunning evidence of this change in the great plains of
North America
this dramatic country in South Dakota is known as the badlands
streams and rivers have eroded the rocks into fantastic shapes but 40 million
years ago these were layers of sediment laid down across an open floodplain
paleontologist Clint Boyd is looking here for the fossilized remains of
creatures from that ancient time and he is finding mammals that are giants this
is part of the bone that we call the femur or the upper thigh bone and this
round surface right here is for the hip socket and so you can see it's very
large we'd be talking about a very large animal and not only do we have the thigh
bone but we've got ankle bones spread out over here and then cascading down
from that spot we've got some of the toe bones coming down so if we add all this
up together based on the size we're looking at an animal that's probably
about two meters tall two hips the creature is known as a Titan of fear
it was a herbivore it fed on the lush vegetation that once covered this area
of the United States
a range of different specimens have been collected at the Denver Museum of Nature
and Science and they reveal that the first item athere's were built on a much
smaller scale when Titanic eaters first appear on the scene they look like this
this is the lower jaw of one of the first Titanic ears and it's one of these
sheep sized animals in only five million years members of the group go from sheep
sized to about the size of a small horse within only 15 million years of their
first appearance Titanic fares look like this here you can see the skull of one
of these Titanic ears in evolutionary terms the size increase is astonishingly
quick but what drove this remarkable change
another fossil could provide an explanation it dates back to the time of
the first and smallest tide on earth ears but it's a very different type of
mammal this is the skull of Malfi less bad water ANSYS the bad cat from bad
water this was the largest predator at the time this is the skull this large
crest is for large jaw muscles which would have given a powerful shearing
bite that ran these blade-like teeth perfect for chopping up a tight an
affair and what's very interesting is that Malthus was exactly the same size
as the top herbivores of the time like Titanic ears
the earliest tightener theas could hide from these bad cats in the dense forest
environments but as those forests began to thin out the Titanes ears were more
vulnerable to attack one way to improve their chances was to grow bigger an
herbivore is much more likely to survive an encounter with a predator if it's a
little bit larger and so there was a bit of an arms race between the Predators
and the prey and animals like Titanic ears were able to escape this predator
pressure by becoming the super-sized Giants we see 35 million years ago
fossilized remains of Titanic is from the Badlands of South Dakota and
elsewhere across the Great Plains allow us to reconstruct its rapid growth spurt
from modest beginnings they increase their bulk ten times over till the
largest stored over eight feet tall
on the open grasslands that increasingly covered the earth many other giant
mammals emerged together they're known as the megafauna
this charm sloths was found in California
in China I've come to see the remains of mammoths
and a remarkable creature that was the largest land mammal to walk this earth
this great beast is called para Kara theorem
it stood 5 metres tall and nearly 8 metres long those furry little mammals
scampering about in the shadows have produced descendants that could
stare the biggest dinosaur in the eye
today the elephant is one of the few species of megafauna to have survived
but those outsized versions have otherwise disappeared from the planet
so what happened to them
their eventual extinction coincides with another key event in the history of the
earth
from around two and a half million years ago ice sheets spread down from the
north and up from the south to cover vast areas of the continents
but it was only when the ice finally retreated just 10,000 years ago that the
megafauna vanished some have blamed that on the rise and Falls of temperature as
the Ice Age finally came to a close but others have sought the comfort amongst
the mammals themselves a newly evolved super predator
to see some of the earliest evidence for its arrival in China I've returned to
Beijing these fossilized remains belong to a primate
it's been dated to around 68 thousand years ago this primate had two new
evolutionary features first its pelvis then animal with the pelvis like this
would have been able to walk upright secondly the skull its brain case is
enormous in proportion to the size of its body it's six times the average
mammal solid and that would report great intelligence and this creature of course
was a human being the early humans put their new intelligence to deadly use
they worked out how to make weapons
these stones carefully chipped to form sharp blades were found alongside human
remains and they developed new powers of communication that enabled them to join
forces and hunt in teams this was a new kind of predator it first appeared in
Africa and then spread to all the other continents and each time its appearance
in that continent coincided more or less with the disappearance of the megafauna
which suggests had the very least that this creature had something to do with
that event to conclude my journey in China and find the last step in our
evolutionary story I'm back in Kunming city to visit one of its busiest
maternity wards
an enlarged brain brought us huge advantages but its size also presented a
basic design problem at Birth the bony skull encasing the brain still had to
make it out through the mother's birth canal
a new addition to our species just 12 hours old can reveal how this is
possible this little boy's name is Xiao Bao it means little treasure he was born
because of a special feature in his cowboy mammal skulls are made up of
separate bones and if most species those are fused together the time of birth to
form a hard bony box to protect them a special organ the brain but not so with
Xiao Bao and other human beings they remain separate and that allowed his
head to slightly change shape and squeeze through the aperture of his
mother's pelvis
this also allows the brain to continue to grow and develop after birth
in fact the plates won't start to fuse until shaobao is around two years old
it's one of the most recent in a long line of remarkable evolutionary
developments that allowed the vertebrates animals with the backbone to
create the dazzling diversity we see around us today shaobao ancestor like
that of all of us stretches back over 500 million years to a tiny little
worm-like creature swimming in the bottom of the sea
this backbone and jaw came from the early fish
his limbs and lungs from amphibians
the reptiles gave him his water tight skin
tiny nocturnal mammals donated a bigger brain sharper senses
and the manner in which he was born
his hands and color vision came from the fruit eating primates and his larger
brain and greater intelligence from the first humans so all our features of our
body can be traced back to our ancient ancestors and there's much more we have
yet to learn about them but one thing is certain the evolution of the vertebrates
has not yet come to an end
available now on the BBC homepage David Attenborough takes a personal journey
through the BBC archive with a collection of 30 full-length programmes
while next tonight here on BBC two don't knock the knowledge brought to you with
the letter K on Qi
