(mellow music)
(dramatic music)
(roaring)
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To study the mammals that lived
during the age of the dinosaurs,
paleontologists were dependent for a long time
on tiny fragments of fossils.
They believed that mammals of that time
were no larger than a mouse,
and that they had only flourished
after the extinction of dinosaurs.
But, the discovery in China of amazingly
well-preserved fossils at the beginning of the 21st century
revealed that mammals were bigger and more varied
than previously thought.
Detailed analysis of their physical features
allows us to understand how they were able to
co-exist with their carnivorous neighbors
and even outlive them.
(dramatic music)
The fossils of these amazing mammals
were found in the volcanic region of Liaoning,
Northeast of Beijing.
Repenomamus was the size of a wolf,
and was able devour young, feathered dinosaurs.
They must have been victim to large predators,
like these yutyrannuses.
They are much bigger than all previously known mammals.
(squeaking)
These repenomamus lived 130 million years ago
in a highly active volcanic area.
(dramatic music)
Preserved in fine, volcanic ash,
their skeletons have survived the ages,
radically changing paleontologist's understanding
of the first mammals.
(dramatic music)
(whining)
(calling)
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These fossil mammals are certainly related to
our own evolutionary history in the sense
that we, ourselves, are mammals.
Mammals, whose name comes from mammary gland,
are the only animals to suckle their young.
Their characteristics include fur-covered bodies,
ears that are separate from their jaws,
and a great variety of teeth.
All of which, according to the latest fossil discoveries,
were already present at the time of the dinosaurs.
And what we see is that they go from having teeth
with a few cusps on them to having teeth that have
many different cusps or tools,
such that they were able to survive
the mass-extinction that killed off dinosaurs.
The fossils discovered
at the beginning of the 21st century
show that the first modern mammals appeared
125 million years ago, but genetic analysis indicates
that they may go back even further.
Until the discovery of new evidence,
controversy rages between geneticists,
and paleontologists.
It all began 250 million years ago,
at the beginning of the Triassic period,
during a time when the world was extremely hot.
The ancestors of the mammals were mammalian reptiles,
like these thrinaxodon, a relative of the reptile family.
Thrinaxodon is considered to be a transitional species
in the evolution towards mammals.
Like reptiles, its legs are not under its body,
but on the sides, and it has no external ears,
but like mammals it has several different
kinds of teeth and its body is covered with fur.
To escape the heat,
it dug burrows along the banks of rivers,
which is where it was fossilized.
New X-ray technology
at the Synchrotron Radiation Facility in France,
enables scientists to analyze
this South African burrow discovered in the 19th century.
(mellow music)
Using this innovation, Vincent Fernandez is able to study
the contents of the rock without destroying it.
(mellow music)
We discovered this burrow on a site where
a road was under construction, and amidst
all the burrows we discovered in this small quarry,
this one had small bones in it,
which gave us the idea of extracting it completely,
and studying it here at the Synchrotron in Grenoble.
This tunnel was buried 250 million years ago,
at a pivotal moment in the Triassic period,
when 70% of the planet's terrestrial species disappeared.
This block of stone may be able to tell us more about
what happened to the survivors of this dramatic extinction.
The best way to find out which animal
used which burrow is to find the animal
directly inside the burrow and to find this animal,
rather than clearing the rock by hand,
we will use X-rays to study the animal
inside the fossilized burrow.
A hundred billion times more powerful
than hospital X-rays, the Synchrotron is able
to distinguish the difference in density
between fossilized bones and the rock itself.
(mellow music)
This high resolution technology revealed the presence
of a thrinaxodon, a long lost mammal ancestor,
plus, an unexpected bonus,
an amphibian named broomistega, lying by its side.
(mellow music)
This is a very big surprise, because first of all,
we did not expect that, but mostly,
it's very rare because animals don't usually
share the same burrow, especially with animals
that are the same size and have the same diet.
Just as some mammals hibernate
to protect themselves from the cold,
this thrinaxodon burrows underground,
and estivates to avoid the heat.
(snuffling and grunting)
In this dormant state, it may not have been aware
of the broomistega taking refuge in its shelter.
The amphibian could also have been hiding
from the hostile climate,
and its fossil shows that it was injured.
We discovered that the broomstega was wounded.
It had a series of seven broken ribs that were healing.
We knew that because it has small bone growth
around the fractures, so we see the healing process.
We know it was probably injured for several weeks.
This discovery revealed
that mammals ancestors had developed the ability
to enter into a state of torpor.
One wounded, the other asleep.
Both animals would've been taken by surprise
by the rising waters.
The lineage to which thrinaxodon belonged
was capable of surviving because it could
dig underground tunnels and withstand droughts
thanks to its specific metabolism.
The fact that this lineage survived
allowed for the emergence of mammals
several million years later.
(mellow music)
Vincent and his South African colleagues
are now searching for new burrows to scan,
hoping to solve other mysteries.
We are also looking for an egg,
or a pregnant female that will finally tell us
which mode of reproduction our ancestors had.
It's a difficult task,
because mammal fossils from the Triassic period
are very rare.
(mellow music)
Until the late 20th century,
the only remains we had of the first mammals
were their teeth.
Like these tiny specimens that are preserved
at the National Museum of Natural History in Paris.
Mammal specialist Emmanuel Gheerbrant
remembers his early years as a paleontologist.
When I started my career in the 80s and 90s,
most of the remains we found were isolated teeth.
We dreamt of finding not only jaws, but complete skulls.
These tiny fragments
are obtained through painstaking work.
Paleontologists must sieve several tons of sediment
to uncover just a few of these mammalian teeth.
(mellow music)
The teeth are well-preserved because
tooth enamel is particularly resistant to time.
It is the hardest part of the skeleton,
the part that fossilizes best.
The interesting thing about these collections
of isolated mammal teeth is their small size.
You can have a collection of several hundred teeth
which will fit into a shoe box.
So, you can have the representation
of a very diversified fauna,
even the history of a whole geographical province,
which boils down to a collection
in the drawer of a cabinet with several hundred teeth.
That's exactly what the collection
studied by Emmanuel Gheerbrant's team looks like.
Started in 1976 in a fossil deposit near Narcy,
in Northeastern France, it now contains
close to a thousand teeth from the Upper Triassic period,
210 million years ago.
This is the oldest collection of mammals in the world,
with a dozen different species identified solely
through the shape of their teeth.
On these molars, the three cusps
are exclusive to mammals.
The molars are used to grind food,
while canines keep food in place, and incisors cut.
This complex dentition indicates
that these animals are mammals
since other animals species have only one type of tooth.
The shape of teeth is like an identity card
to show what group they belong to.
It's an identity card to identify the animal,
and it also reveals functional information,
in other words, the animal's diet.
Because sharp teeth for instance
indicate an insectivorous diet,
but if they have rather flattened teeth,
that indicates a herbivorous diet.
Though they tell us more
about how these dinosaur age mammals ate,
they fossils give no indication as to what they looked like.
(pensive music)
However, a tiny clue, discovered in France in 2008
reveals more about the skin of these extinct animals.
This abandoned quarry is located near the town
of Archingeay on the West Coast of France.
On this sand excavation site
two paleontologists from the University of Rennes
take advantage of the exposed walls
to come and collect fossils.
This geological layer dates from the Cretaceous period,
100 million years ago.
At the time, it was covered
by a forest of conifers and ginkgo trees
whose remains have been uncovered
by Romain Vullo and Didier Néraudeau.
Look at this.
This leaf has been in clay
for the past hundred million years.
Comes off, and if I blow on it,
I can bend it, which shows that it's still flexible.
Apart from its change in color,
the passage of millions of years doesn't seem to have
altered this leaf significantly.
The paleontologists are searching for another treasure
in this petrified forest.
Occasionally, bits of animals become trapped
in the resin from conifer trees.
When the resin fossilizes, it becomes amber.
So, here we are at the bottom of the quarry.
Water has poured down
and created an interesting little outcrop,
because you can see the different layers.
The layer is streaked because you have
different alternating sediments.
You have two main types of deposits.
You find sand deposits, white, ochre, and red,
and then another deposit from an accumulation of coal,
which forms these small black veins.
So, here, you can see sand alternating with clay beds
that contain plant debris, and small pieces of amber,
which is what we're looking for in particular.
The sediment is then sieved in a nearby pond.
We've got quite a few small fragments here.
That's a good sized piece.
It's slightly translucent, part brown, part red.
Paleontology relies on meticulous work,
and a fair amount of luck.
One major clue to the appearance of mammals was discovered
thanks to an incredible stroke of good fortune.
(tense, anticipatory music)
While looking for bacterial filaments,
one of Romain Vullo's colleagues
made an exceptional discovery.
Two hairs, trapped in amber.
So, we see the whole piece of amber,
and in the middle, the longer of the two hairs,
which is slightly bent.
As you can see, it is very, very fine.
We compared this 100 million year old fossil hair
with the hair of current mammals
and we found that this one presents
many similarities with what can be found
in existing species including scale morphology,
and scale layout.
And, the contours also show strong similarities
to the hair of living animals.
From a paleontological point of view,
this is an outstanding discovery
since there are only one or two
fossil mammal hairs in the world.
100 million years ago,
warm blooded mammals already had the same hair as today,
to protect them from the climate,
and allow them to survive the extinction
that decimated large dinosaurs.
(mellow music)
In China, at the beginning of the 21st century,
new clues to the physical appearance of mammals
were unearthed.
In a deposit dating from the Cretaceous period,
125 million years ago, fossils were discovered in an area
that was once a peninsula with a sub-tropical climate.
This world, dominated by huge dinosaurs
like these 30 foot hight titanosaurs
was also home to mammals.
Like this Eomaia scansoria, literally,
ancient mother that can climb.
Preyed upon by feathered dinosaurs like Zhenyuanlong,
Eomaia was the oldest known mammal ancestor
when it was discovered in 2002.
(pensive music)
Located in the Liaoning region, Northeast of Beijing,
this deposit was once a volcanic area
that has preserved our distant past
for millions of years.
(pensive music)
Zhe-Xi Luo, an American paleontologist
of Chinese origin is at the Xihatun Cliff
where many long lost fossils have emerged.
This Ni Tian formation is lake deposits
and it trapped all variety of fossil vertebrates,
most famous of all are feathered dinosaurs,
but are very important for understanding our own
human beings early evolutionary history,
are these Cretaceous mammals.
125 million years ago,
multiple volcanic eruptions created
a series of sedimentary layers.
Pockets of red ash flattened the mammals into the gray mud,
like a printing press.
(dramatic music)
(chittering)
Measuring six inches from nose to tail,
and weighing around an ounce,
Eomaia would've been fair game for the feathered dinosaurs.
(dramatic music)
The fossil mammals are preserved very well
because they lived nearby shallow water lake.
The sediments cumulated fairly slow,
and also there are occasional volcanic eruptions,
so the hot volcanic ash helped to trap
those fossil mammals in the sediment,
and that is why they are preserved so well.
Therefore, gave us this beautiful fossil to study.
At the Natural History Museum of Beijing,
Zhe-Xi Luo studies fossils of the Eomaia scansoria group,
placental mammals whose fetuses are sustained in the uterus
by a placenta, just like humans.
The whole body of the animal is beautifully preserved,
a dream come true for any mammal specialist.
It is absolutely amazing that we have
the entire fossils here.
With the entire skeleton we can start to flush out
a more interesting picture about these early mammals.
These guys lived in Cretaceous,
it has very grassile jaws, and we can recognize
even with the naked eye, the limbs are quite slender,
and we can tell by its very long fingers
and the different nail structures
that they are tree climbers.
This shows that the placental ancestors
are capable of exploring the arboreal,
or tree-living niches than all these other contemporaries,
and this gave us a big evolutionary advantage.
(squeaking)
Eomaia left its young high up,
out of reach of dinosaurs,
but sometimes slept on the ground.
These very first mammals would have to leave their shelter
in order to drink.
(squawking)
(running water and insects chirping)
Their extraordinary mobility is revealed by this skeleton,
particularly by the elongated trapezoid bones,
which resemble those of tree-dwelling primates.
It is really by studying the ankle joint
we are able to recognize a great many features
to place this particular fossil on the line
that eventually gave rise to modern placentas.
Its feeding habits were revealed
thanks to its extremely well-preserved teeth.
And you can tell that these mammals have
very sharp cusp in the front,
and in the lower teeth, generally there were
a series of very sharp triangles,
and those are very effective for cutting
the skeletons of insects and also slice off
the flesh out of worms.
(insects chirping)
(sniffing)
(crunching)
(squeaking)
After the discovery of Eomaia,
more fossils were unearthed in China, changing the vision
that paleontologists had of ancient mammals.
Countless wonders are kept at
the Institute of Vertebrate Paleontology in Beijing.
Among them is a repenomamus with a complete,
and unusually large skeleton.
(dramatic music)
Yuanqing Wang is the paleontologist
in charge of studying this strange, 30" creature,
unearthed in 2004.
A lot of Mesozoic mammals that are about the
size of a mouse or rat.
So, this is quite big.
Another feature of this large mammal
is its sharp, pointed teeth, embedded in a strong jaw.
Before we found this animal,
we know with Mesozoic mammals, generally it was thought
they're insectivores, and small,
living in the shadow of the dinosaurs.
You can see the teeth, they're sharp, and pointed.
So, it's a carnivorous animal.
Especially in his stomach area there are some
fragmentary bones of baby dinosaurs called Psittacosaurus,
so we said, "Okay, this guy ate dinosaurs."
The animal's stomach contents
are revolutionary.
They contain proof that some mammal ancestors
actually fed on young dinosaurs
rather than living in their shadow.
(barking)
(squawking)
(growling)
Paleontologists do not know exactly how they hunted,
but they believe repenomamus worked together in packs
like wolves.
(dramatic music)
(growling)
(snarling)
(dramatic music)
(mellow music)
The Beijing collection has
many surprises in store for scientists.
Discovered in 2006, volaticotherium has an unusual feature,
a large fold of skin connecting its upper and lower limbs.
(mellow music)
Observed under a microscope, this dark stain
reveals the presence of numerous hairs.
Called a patagium,
it's a fine membrane of skin covered in fur.
Like a flying squirrel,
the taut skin stretched between its limbs
meant that volaticotherium was able to glide from the trees.
(chittering)
Before this discovery, scientists believed that bats
were the first flying mammals to appear
50 million years ago.
Volaticotherium, who was around
the same time as the dinosaurs
showed that flying mammals were around long before that.
This nocturnal hunter waited for dusk
to start searching for its prey.
(suspenseful music)
It's really interesting, it's told us that
ecological diversity of the Mesozoic mammals
is much wider than we thought for,
really with other animals, it was living in the tree,
or walking on the ground.
Like these animals can climb there.
(dramatic music)
This flying animal confirms
that mammals had adapted to different environments
long before the extinction of the dinosaurs.
Despite the discovery of these fossils in China,
one question still troubled the scientific community
during the early 21st century.
When did placental mammals first appear?
Geneticists and paleontologists
thrashed out their opposing views in scientific journals.
In the German town of Oldenburg a team of researchers
hunts down the genes of modern mammals
in order to construct their family tree.
(tense music)
We can estimate by seeing how similar
a gene is in two different species of mammal
how closely related they are.
Olaf Bininda-Emonds is the author
of a 2007 study which analyzed the genes
of 99% of animals living today.
(mellow music)
This mammoth task required eight months of DNA sequencing
to track the genetic mutations of 60 markers
throughout the evolution of mammals.
The molecular data will give us
a much more complete picture.
We have DNA here for many more species
than we have fossil data for.
The fossils will give us
point estimates throughout the tree.
The DNA will fill in the gaps
and give us all the divergence times
for all the species of mammals
and all the common ancestors that were.
(mellow music)
This method, called the molecular clock,
shows that placental mammals separated from marsupials
160 million years ago during the Jurassic period,
then diversified during the Cretaceous period
to form the current main groups,
rodents, carnivores, and primates, an unexpected result,
since no fossil of these early mammals
has ever been discovered.
This was interesting because there's
a very big disconnect
between molecular studies and fossil studies.
(mellow music)
In Pittsburgh,
on the other side of the Atlantic,
another study offered very different results.
(mellow music)
It is the work of John Wible,
a paleontologist at the Carnegie Museum of Natural History.
(mellow music)
It's starting point was the discovery of a skull
found in a 75 million year old deposit in Mongolia
named Maelestes gobiensis.
It has been studied from every angle
since it does not belong to any known species.
400 of its morphological features
have been compared to those of 82 fossil,
or living mammals.
What we did is we looked at the individual
morphological features of this animal
across a broad array of other fossil forms
and living mammals to try to figure out what it was,
what it was related to, and our study supported
the traditional view that there were no
fossils living during the Cretaceous
that were members of the placental group itself,
there were only the ancestors of the placentals living.
Which of these two studies
should we believe?
Fossil or genetic?
The molecular studies all tend to say
that the crown group orders, rodents, primates,
carnivores, bats, they all have their origins
in the Cretaceous when the dinosaurs were still alive.
The problem is there is
absolutely no fossil evidence supporting this.
Many of these modern groups,
according to the molecular clock analyses
actually are, they should be present
in the Cretaceous record.
We can't find them.
There's no doubt that there were
placental mammals in the Cretaceous.
What's debated is what kind of placental mammals they are.
And, it's a question of who's right at the moment.
To achieve the most complete
mammal family tree, both types of data
will need to be refined.
Defining the pace of genetic mutations on one hand
and seeking fossil beds on the other,
since new fossils would confirm the geneticists' hypothesis.
In the meantime, paleontologists are also
trying to understand how these early mammals
protected themselves from dinosaurs.
(mellow music)
The ability to nurse their young could have been a benefit.
(mellow music)
If we want to understand how mon eutherians come from
we need to look at mon eutherians' distant relatives.
Zhangheotherium is a mammal
that is even more ancient than placental mammals.
This extremely well-preserved fossil
was discovered in China in 1997.
(speaks foreign language)
We can be relatively sure it is a mammal
because it had fur, and associated with fur
would be a whole series of reproductive features
as we know that it must have nursed its fetuses
but we don't know if the fetuses was born
either in a egg or a live fetus.
Lactation offers an advantage
when food is scarce, since the young continue to be fed
thanks to their mother's body reserves.
Lactation first appeared in the form of
hundreds of milk-producing glands on the abdomen,
just like modern platypuses.
The young would lick the thick milk
from their mother's hair.
(squeaking)
(mellow music)
Zhangheotherium has another characteristic
in common with monotremes like the platypus.
A spur on its hind leg.
This species definitely has another fossil
that has preserved with a bony spur,
and it's also consistent with the first observation
directly from this particular specimen.
In modern monotremes, this spur is definitely used
for self-defense, but we do not know
if it is truly poisonous or it's just a bony spur.
(suspenseful music)
Snakes have fangs, insects can sting,
but this defense technique is rare among modern mammals.
(squeaking)
(suspenseful music)
(squeaking angrily)
(growling)
Located on the male's hind legs
this spur may have released a venom
capable of paralyzing their foes.
(suspenseful music)
(squawking)
According to scientists,
this weapon is not terribly efficient
since it takes time for venom to have an effect.
As they evolved they tried other strategies,
like running away.
And, to improve this tactic,
what better than a superior sense of hearing?
The evolution of ear bones was a key advantage
for primitive mammals.
In 2011 the discovery of this Liaoconodon fossil
shows at last how the jawbones of these reptiles
migrated to form the middle ear of modern mammals,
120 million years ago.
This specimen's the most complete mammal
we have ever found in Western Liaoning.
All the bones are preserved here,
so it's a very beautiful specimen.
Especially this specimen preserves
the tiny bones of the ear region.
These ear ossicles usually is very difficult
to be preserved in fossils, because it's very tiny.
More important, it is a transitional stage
of the mammalian middle ear evolution.
In ancient mammals the lower jaw
was linked to the skull by an elongated bone.
In Liaoconodon this evolved to begin forming the earbones.
The hammer, anvil, and tympanic ring
became completely detached in modern mammals
to form the inner ear.
Amazingly, every mammal embryo, including humans,
reproduces this evolutionary phase in the womb,
resulting in the formation of the inner ear.
This precision tool allows us to analyze everything
that happens around us constantly.
Yes, it can hear the dangers earlier than the
other kind of animals, so, helps them to
escape from the predate.
The mystery of the inner ear bones,
a link with our reptilian past,
is cleared up thanks to this new fossil.
(mellow music)
Another mammal weapon, teeth, reveal their secrets
at the University of Washington in Seattle.
This is where Gregory Wilson
uses state-of-the-art technology
to analyze the teeth of multituberculates,
mammal species that became extinct 34 million years ago.
We found some really exciting results, actually.
What we found is that these multituberculates
that were living alongside dinosaurs
actually undergo an adaptive radiation
20 million years before dinosaurs go extinct.
And, what we see is that they go from having teeth
with a few cusps on them,
such that they can eat insects and so on,
to having teeth that have many different cusps or tools,
such that they can exploit
a new resource in flowering plants.
(mellow music)
It's that ability to exploit that new resource
that allows them to expand,
in terms of numbers of different species
of multituberculates as well as
the range of body sizes that they have,
such that they were able to survive
the mass-extinction that killed off dinosaurs.
(mellow music)
This study shows that multituberculates
evolved well before the extinction of dinosaurs.
They moved from an insect based diet
to a diet based on fruit, or even angiosperms,
flowering plants that appeared during the Cretaceous period.
To reach this astonishing result,
Gregory Wilson used fossils collected over a hundred years
in Montana's Hell Creek formation.
By studying this collection
of tiny teeth under a microscope,
he was able to familiarize himself
with the many species of multituberculates.
(mellow music)
This is the largest of multituberculates that lived,
the size of maybe a beaver or a marmot,
and it has many, many bumps all along the tooth row.
Those bumps act as tools to crush and grind food.
Another example sits inside this tiny vial.
It's another multituberculate, but it also had teeth
with many little bumps, so this was a smaller version
of this animal that lived during the time of dinosaurs.
This lineage we've known about for a very long time,
but it's been difficult to really quantify
or understand what the shape of those teeth mean.
We've tried many different approaches
but none have really been able to give us
the precision that we can now attain today.
This technological revolution
came in the form of the CT scan,
a medical imaging tool nowadays used by paleontologists.
(mellow music)
Specimens like this 67 million year old tooth
are first scanned with X-rays on a microscopic scale.
It is identifiable by its long incisor,
but what intrigues researchers
is the complexity of its molars.
Once the data is collected, cartography software
reconstructs an accurate map showing the shape of the teeth.
Gregory Wilson has found that carnivores
have a fairly simple tooth structure
with approximately 110 cusps per row of teeth,
while multitubercular teeth are far more complex
with up to 348 cusps.
This particular specimen that I just pulled up
has about 250 different complex little tools
on the surface of its tooth row,
and those little tools help break down plant material
that needs to be processed very finely
in order to be digested properly.
So, these guys have evolved towards eating plants.
(chittering)
(whimsical music)
It is this key function of grinding
which promoted the explosion
of herbivore and omnivore species,
an ecological niche untapped by primitive mammals.
(mellow music)
Despite these multiple discoveries,
at the end of the 20th century, the crucial question
about the origins of the first real mammals remained.
Once again, the Liaoning region provided the answer.
In 2011 Chinese farmers found the fossil
of a mammal called Juramaia sinensis, meaning,
Jurassic mother from China.
(mellow music)
The paleontologist Zhe-Xi Luo
has come for the first time to visit this area,
which stretches over several miles.
It is not an easy task to identify fossil bearing rocks
under the fields of lush corn.
But he is guided by a local specialist
in feathered dinosaurs whose oldest specimen, Anchiornis,
was excavated on a site close to this one.
(mellow music)
It's exciting fossil discovery because
it gave us a new milestone as to when
the placental lineage first start to appear on Earth,
and all the modern placental mammals have a deep root
into the Jurassic and it's coming from right here.
These rocks also are embedded with volcanic ashes
and this site had been dated by geochronology
to be 160 million, plus or minus a little bit,
so we know for sure these rocks
actually belong to the late Jurassic.
The Juramaia sinensis fossil
is the oldest specimen of a placental mammal
and is a critical piece of the puzzle
in the evolution of mammals,
was identified by its teeth, which included
molars, canines, and incisors.
As the genetic studies of living mammals showed,
their origin is much older than existing fossils
had suggested since the discovery of Juramaia
means that placental mammals must have appeared
at least 35 million years before Eomaia scansoria,
and even though paleontologists
are still seeking fossils from the Cretaceous period,
belonging to current groups like rodents or carnivores,
this discovery brings the conflicting opinion
of geneticists and paleontologists closer together.
Independent corroboration by fossils on one hand
and by molecules on the other gave us the confidence
that we are getting closer to the correct answer.
With Juramaia we know that
160 million years ago mammals already had
the characteristics that made them successful.
Fur, complex teeth, and acute hearing to escape predators,
and locate their prey.
(mellow music)
The general adaptation such as insectivory,
and such as capability to move on the tree,
gave this particular mammal some evolutionary advantage.
It has really equipped it well enough already
in the late Jurrasic for it's descendant to thrive
after the dinosaurs extinction.
(squawking)
(suspenseful music)
(squawking)
Certainly the mammals ancestors
were very small at the time of dinosaurs
but much more varied and better equipped
than was previously thought,
with advantages that we find later in primates,
our closest relatives.
(dramatic music)
(roaring)