(mysterious music)
Dragonflies the size of hawks.
Centipedes larger than humans.
A strange menagerie of giant insects and amphibians
reigned over the Earth 300 million years ago.
Over time, these huge creatures shrunk in size
or disappeared.
The reasons for their progressive extinction
remain controversial.
358 million years ago, the continents came together
to form the supercontinent, Pangea.
This was the beginning of the Carboniferous period.
Oxygen levels in the air were much higher back then.
35% compared to today's 21%.
For the first time on Earth,
giant trees stored carbon dioxide
and released oxygen in abundance.
Human beings would not have survived
in this high oxygen atmosphere.
But for some swamp dwellers, it was ideal.
Like the Arthropleura, measuring up to 10 feet.
This long lost cousin of the centipedes was a herbivore.
Or Meganeura, with a wingspan up to 25 inches,
this member of the dragonfly family
is the largest known flying insect ever discovered.
A tireless predator.
It had no airborne competitors at the time
since birds and flying reptiles didn't exist yet.
The high oxygen levels in the atmosphere
give the characteristic sepia color
to the sky during the Carboniferous period.
Oxygen also makes the air extremely flammable.
(thunder rumbling)
Such a hostile world is hard for us to imagine.
Lightning storms could set aflame the immense forests,
and their inhabitants.
During this period not a day went by
without huge forest fires,
and yet giant insects thrived.
Later when the first became less frequent,
these astonishing creatures simply disappeared.
Scientists are trying to determine
what caused their extinction.
There are several possible culprits.
In fact, it's a bit like an Agatha Christie novel,
where there's not one, but several murderers.
It's our job to take the clues we have
and reconstruct the investigations
in order to come up with the most likely scenario.
While we've known about giant insects
since the 19th century,
paleontologists do not understand why they have disappeared.
For a long time, a change in the composition
of the atmosphere was the only explanation.
But at the beginning of the 21st century,
the discovery of fantastic fossil insects
and their predators opened up new possibilities.
While that's a wonderful hypothesis,
and assuredly something was preying
upon these giant insects,
we don't have great evidence for it.
Around the world,
American, European, and Chinese scientists
confront the old theories using new fossil discoveries
unearthed by groundbreaking technology
to try and explain why these giants became extinct.
The earliest giant insect fossils
were found in the French region of Allier in 1880.
Under the surface of this pond
were the remains of animals that had died
350 million years ago during the Carboniferous period.
Meganeuras.
Now extinct, these tireless predators
are the largest flying insects that ever existed.
This abandoned industrial site
was an important coal field in the 19th century,
and as the coal was dug out,
fossils were discovered close to the town of Commentry.
The owner of the coal mine, Mr. Monyi,
gave his name to the specimen that is preserved
at the Natural History Museum in Paris.
Meganeura Monyi.
Andre Nel, a paleontologist
whose specialty is early insects,
watches over this valuable piece.
(speaking foreign language)
Miners would look for fossils
to make a little extra money,
and one day when they were opening slabs,
they cam across this animal.
Unfortunately, when they were digging it out
they hit it four times with a pick and we lost its head.
They were the super predators of the time.
Predators were other insects that were also very big.
These large size fossils are quite exceptional.
While thousands of insects were found
on the site of Commentry,
only five Meganeuras were ever discovered.
Meganeura, like all other insects, had four wings,
two on each side attached to the thorax in the center.
In front you had a head with big eyes
because it was a predator, so its eyes,
just like modern dragonflies,
were used to see its environment in 360 degrees.
So possibly even behind the animal.
To better understand
how this extinct animal once lived,
we must step back 300 million years in time.
(mysterious music)
This is what the French region of Allier
would've looked like then,
a giant swamp scattered with cypruses.
Humidity at nearly 100% made the atmosphere dense
and allowed Meganeura to easily carry
its heavy exoskeleton into the air.
It is part of a genus that is extinct today,
but it looks much like modern dragonflies,
and it's part of the same Odonatoptera superorder.
With wings that functioned independently of each other,
Meganeura was agile in flight,
but unlike its contemporary cousins,
it couldn't fold its wings.
Faced with this efficient airborne predator,
vegetarian insects such as Palaeodictyoptera
had to keep themselves out of sight.
By comparing its anatomy to modern dragonflies,
we can guess at Meganeura's main physical characteristics.
One, it could fly over 40 miles per hour.
Two, it was a sight predator.
Its head was independent from the rest of its exoskeleton
so it could keep it still while flying
and focus on its prey.
Three, it had a huge appetite.
It could eat its own weight in food every 30 minutes.
To catch all this food, Meganeura had an array
of attributes identified in fossils.
(crunching)
But what might explain its giant size?
Away from the public is the museum's library of species,
where they keep the specimens that scientists study.
Here we find Meganeuras and their prey,
both reaching impressive sizes.
(speaking foreign language)
So here you have an example of a Meganaeura,
on which we see the base of its wings,
the thorax, but what is most spectacular
are the forelegs equipped with strong spines
that were used to stab prey.
But the Meganeura's prey were also large sized insects,
like the Palaeodictyoptera.
You just have one wing from here to here,
so you can imagine the whole thing.
These were Meganeura's prey.
They were big guys too.
Big insects to escape big predators.
So in this case we have an arms race
between predators and prey.
But this battle to be the biggest
between Meganeura and its prey
seems to have had its limits,
otherwise paleontologists would certainly have found
even bigger and more terrifying flying insect fossils.
Most of Meganeura's day was spent looking for food
since its metabolism required a lot of energy.
According to scientists, the huge size of insects
during the Carboniferous period was possible
because of the high levels of oxygen in the air.
Insects don't have lungs, but instead use a unique system
of tubes, trachea, and tracheos
to bring air directly to their organs,
including their digestive system.
The downside to this system is it lacks efficiency.
Air travels through the tissues in the form of gas.
The bigger an insect is, the more oxygen it needs.
(speaking foreign language)
It is very strange that these animals
reached these sizes, because nowadays
we do not have such big insects,
and at the time of the dinosaurs,
when we had large vertebrates,
insects were much smaller.
It turns out that in the Carboniferous period,
for reasons linked to geochemistry,
the oxygen rate in the atmosphere
was higher than it is today,
which encouraged the development of animals
such as the large insects.
Meganeuras could not survive
in today's atmosphere,
because not enough oxygen would reach their organs,
including their brains, and they would faint.
Since the beginning of the 20th century,
scientists have proposed a link between the size of insects
and the concentration of oxygen.
But it wasn't until 2007
that an experiment finally proved it.
In the Chicago suburbs, the Argon National Laboratory
houses the United States' most powerful synchrotron,
a scanner that generates the brightest X-ray beams
in the northern hemisphere.
The distance around the particle accelerator
is more than half a mile,
so Jake Socha, the scientist in charge of the study,
uses a trike to get around.
Today live insects are being put under the scanner.
We use the idea that you can take living insects
and make inferences about insects that existed in the past.
What we're trying to do in this study
is to test an old hypothesis
that the amount of oxygen in the atmosphere
is what limits insect body size.
So the idea of this hypothesis is that
when you have more oxygen your insects can get larger
and when you have less oxygen,
insects will get smaller in response.
But no one had really ever tested this hypothesis before.
So we used synchotron X-rays to look inside the animal
to study the dimensions of their tracheal system.
This particle accelerator
generates extremely intense and focused X-rays
that pass through the insect's body.
Our purpose is to see the tracheal system in action,
and some of the tracheal tubes are really small,
and we want to see it in the living animal.
So this is really the only technique
where we can do all of those things.
(mysterious music)
For the first time, scientists are able
to actually observe an insect breathing.
(chattering)
Using this experiment, they discover that crickets
not only breathe passively,
but also use their whole bodies
to carry air to their organs.
And you can see that bubble in the gut
moves forward to the head and then it moves backwards,
and every time it's doing that, it's synchronized
with the compression of the tracheal system.
The movements that you see here
are not a passive effect.
This is an active movement by the animal,
and the ultimate cause of it are contraction of muscles.
Just as this cricket
contracts its digestive system to send air to its organs,
Meganeura would've contracted its abdomen
to absorb the thick Carboniferous air.
The elastic exoskeleton would resume its shape
once the muscles had completed their action.
But beyond the discovery of this internal movement,
what interests Jake Socha is the space occupied
by the respiratory system within the insects' bodies.
He has compared beetles of different sizes
to study the link between their size
and that of their respiratory system.
And what we found is that the tracheal tubes
take up a larger fraction of the body
as you go from smaller to large than you might expect,
so what we think based on the study
is that you would make this even larger,
so we would scale this up farther and farther,
eventually you reach a limit
where you can't stuff more tracheal system inside the animal
because we have to have other things like muscles and gut
and nervous tissue, fat bodies, things like that
that are all important for the physiology of the animal.
You can't just have one big tracheal system.
The higher oxygen concentration
of the Carboniferous period
meant that insects required fewer respiratory tubes
and could therefore grow to a larger size.
But with the modification of the atmosphere,
the giant insects had to reduce their size
over millions of years of evolution,
and not all of them survived these changes.
290 million years ago during the Permian period,
oxygen levels decreased from 35% to 23%,
close to today's level.
Pangea had already formed a supercontinent
extending from one pole to the other,
surrounded by a single ocean.
It was subject to extreme climatic conditions.
The heart of the continent
suffered drastic temperature changes
and deserts appeared.
But at the equator heavy rainfall allowed the great forests
from the Carboniferous era to survive.
(rain falling)
(thunder rumbling)
During this period of major climate change
punctuated by the monsoons
and the warming of the atmosphere,
a living fungus appeared on the bark of trees.
This tiny mushroom uses an enzyme to break down wood.
Gradually plant debris and dead trees decompose
and no longer build up on the ground to form coal.
The fungus stopped the accumulation of carbon on the ground,
and instead it was recycled into the atmosphere.
The proportion of oxygen in the air decreased gradually,
with major consequences for the environment.
This transitional period brought about the demise
of Arthropleura, a distant relative of the centipedes.
But why did the first giants of the Carboniferous period
disappear?
Could their lifestyle be responsible?
In 1977, Arthropleura fossils were found
in the heart of the French countryside.
The sag heap surrounding this former mining town
are hallmarks of its industrial past.
In the local natural history museum,
tribute is paid to the miners who discovered fossils
while they were working.
Among them this impressive set of footprints,
the most important ever found in France.
They're examined by Sylvain Charbonnier,
a specialist in arthropods,
the family of invertebrates that includes
insects and centipedes.
Here you can see a set of tracks.
You have two trails that are parallel.
This was made by an organism of quite a respectable size,
an animal that must have measured around three feet long.
It's just a fragment of a track
that was probably much bigger.
Unfortunately no adult sized fossil
has been discovered.
The paleontologists have found many smaller specimens
in these coal deposits.
You can see here what this little creature looked like.
These are juvenile specimens, which are tiny.
Here's a complete specimen with its shell
that is well preserved, so obviously this organism
as it grows would produce larger trails when it moves.
Arthrolpleura was rather similar
to modern centipedes.
It could reach 10 feet in length
and it crawled on the ground or up trees in search of food.
Life in the rainforests during the early Permian period
was quite similar to that of the Carboniferous period.
(growling)
And there was enough oxygen in the atmosphere
for Arthropleura to thrive
and face unexpected predators,
such as Eryops.
This amphibian locates Arthropleura using cells in its skin
that detect vibrations on the tree trunk.
(suspenseful music)
But Arthropleura had a considerable advantage.
The claws at the ends of its articulated legs
allow it to grip the trunk,
and its protective shell shields it against attackers.
(splashing)
Arthropleura's disappearance may not have been caused
by predators, but by decreasing food supplies.
This creature was an herbivore.
At the time, it would've had plenty to eat.
(speaking foreign language)
At that time, the vegetation was equatorial or tropical,
so it was an extremely lush vegetation
with a great variety of plants.
These plants are in fact the origin of coal.
Arthropleura lived in this forest environment.
You also have on the other side
trees and leaves that were found
in Arthropleura's stomach contents.
So it probably fed on these tree branches.
Did they eat from trees lying on the ground
or did they climb trees?
These are hypothesis we will probably never know for sure.
These fossilized plants
have been so well preserved
that they still appear alive.
But as they began to disappear,
Arthropleura had to adapt.
This forest environment will tend to dry out
at the end of the Carboniferous.
The climate will change, the vegetation will disappear,
and Arthropleura will lose its food source,
which is probably one reason that explains its extinction.
Over a period of 10 million years,
the atmosphere and the climate gradually changed,
bringing about the demise of Arthropleura.
The most recent fossils we have date from about
280 million years ago.
Evolution could've retained
smaller and more energy efficient insects.
However in 2009, scientists were surprised to find
new Meganeura fossils in the South of France.
These specimens, discovered on sites
dating from the end of the Permian period,
proved that the declining oxygen rate
cannot be the sole explanation
for the extinction of giant insects.
What clues did these unexpected fossils reveal?
These deposits are scarce.
Scientists know only about 15 of them in the world,
and like here, they've not been all fully excavated.
This beautiful landscape with its typical red rock
is located less than an hour from the French Riviera.
This is one of the sites excavated by Andre Nel.
(speaking foreign language)
Here we are, 250 million years
into the red continental Permian.
Red Permian because the rocks have become oxidized.
The iron is oxidized and has become red.
So we are dealing with an environment
that is extremely rich in organisms
that have left their impact
but few visible fossils up to now.
In any case, in this deposit.
But fortunately fossils have been found at other deposits.
It's in a similar geological layer
that insect fossils from the Permian period
were discovered in 2009,
close to the French city of Montpelier.
For a long time we thought these giant dragonflies
had existed during the Carboniferous period
at the beginning of the Permian,
but they no longer existed towards
the middle or end of the Permian.
But we were surprised to discover dragonflies
that were as big as those from the Carboniferous.
Paleontologists were perplexed
since the level of oxygen had already decreased
by that period.
In theory, giant insects should have disappeared,
but the specimens of different sizes
concerned in Andre Nel's laboratory in Paris
proved that they were still around.
(speaking foreign language)
There are tiny wings in the Meganeura day,
like this one here.
This is the size of a modern dragonfly's wing.
We have much bigger species.
Here is the rear wing of another Meganeura,
another species.
This one too was a giant.
We have bigger ones, but only fragments.
This here is a piece of Meganeura's wing.
The size is comparable to that
of the Meganeura of the Coniferous.
We estimate that its wingspan is around 23 inches.
We see that with these animals there is great diversity.
It's during this time that they become the most diversified.
We have small ones, medium ones, big ones,
and very big ones.
This means they have not really become extinct
at this period.
This does not sit well with the scenario of extinction
due to the decrease in the level of oxygen.
These recently discovered species
of Meganeuras found in France
have also turned up in the United States.
Evidence of their existence is accumulating.
(suspenseful music)
Here is what the Earth looked like
during the middle of the Permian period.
A hot and humid world covered with tropical forests,
with an oxygen rate just slightly higher than today.
One animal species survived against all odds,
Meganeura, represented by this Meganeuropsis.
This specimen, discovered in Texas,
is as large as its French cousins.
But how can an insect measuring nearly two feet
survive breathing air that was much poorer in oxygen
than in the past?
Did it have an advantage that Arthropleura did not?
The Meganeuropsis fossil was discovered in 1937
next to Kansas City in the USA.
Professor Michael Ingalls is a paleoentomologist
who has worked at the University of Kansas
for the past 20 years.
Author of the definitive work
on the evolution of the insects,
he is also the head of this collection
containing 4.7 million specimens,
most of them contemporary insects.
These are some of the large insects that occur today,
large moths, stick insects, beetles,
dragonflies, and damsel flies,
and while they're pretty impressive in their size,
none of them can compare to the giant insects of the past.
According to Ingalls,
one asset which might've enabled Meganeuras to survive
during the Permian period despite the low oxygen levels
is the movement of their wings.
You would have an easier chance getting
a large flying insect than you would
a large insect that doesn't fly.
Wings are vital not only for the movement of the organism,
but as the muscles contract to move the wings up and down,
they actually press up against the air sacks
and move air through the body.
Flight actually confers an advantage to the giant insects
in the fact that the actual movement of the flight muscles
helps to support the metabolically active tissues
within them by getting oxygen into an area
where a wingless insect or other arthropod
would not be able to.
This full body ventilation
could be the secret to Meganeuropsis's survival.
The movement of its wings quickly brings air to the trachea
which then supplies the organs with oxygen.
While the ground dwelling giants of the Carboniferous period
disappeared, this advantage would've allowed Meganeuras
to continue ruling the skies during the Permian period,
remaining at the top of the food chain in the swamps.
This Diplocaulus, a now extinct amphibian,
has no chance of going unnoticed,
betrayed by its need for air.
Meganeuropsis sees it as soon as it leaves the water surface
thanks to eyes that are extremely sensitive to movement,
shapes, and colors.
(suspenseful music)
Meganeuras were the super predators of the time,
and their wings enabled them to survive
despite falling levels of oxygen.
So what caused their extinction?
No Meganeura fossils have been discovered
from after the Permian period.
Today scientists still don't know
exactly when they disappeared,
but other large sized dragonflies survived
the next 130 million years.
To explain the extinction of these giants,
scientists are now contemplating
the emergence of new predators.
While insects were the only flying creatures
during the first part of their history,
other animals took to the skies
during the later Permian period,
between 300 and 250 million years ago,
of what was to become eventually Europe.
Jean Sebastien Steyer,
paleontologist at the Natural History Museum in Paris,
is the leading French specialist in early vertebrates.
He has come to the legendary paleontology gallery
to collect a very important specimen
for the study of insect predators.
Though smaller in size than many other fossils,
this was the first of its species
to possess a major advantage.
This is the fossil of a gliding reptile
that is about 250 million years old
and has the strange name of Coelurosauravus.
This reptile actually developed gliding flight.
The ability to glide allows an animal
to catch prey in the air, like the giant insects.
The planet continued to heat up
at the end of the Permian period.
Swamps, an infinite source of fossils,
now had aquatic plants characteristic of stagnant waters.
Like the insects during the Carboniferous period,
reptiles were just starting to try out
life in the trees and flying.
Amongst them, Coelurosauravus would become
an outstanding insect hunter
thanks to its retractable wings.
It had a very unusual and interesting anatomy.
Its fairly small head was a triangular shape.
On its skull, we can see small conical pointed teeth.
They were probably used to crack the hard exoskeletons
of insects.
And of course, the main characteristic
of this gliding reptile are its stick shaped bones
that start around the armpits and enabled this animal
to throw itself in the air and base jump.
We can well imagine it climbing up this microscope,
for instance, and then jumping.
We can even imagine it climbing with its small claws
and then unfolding its wings to glide.
So we can picture the race between Coelurosauravus
and the flying insects living at that time.
Only 16 inches long, this small reptile
couldn't catch Meganeuras.
But it could compete for the same prey,
the Palaeodictyoptera.
To catch its victim, it has to take the plunge.
Coelurosauravus can't flap its wings.
To catch flying insects,
it relies on an element of surprise.
And its ability to glide.
There is no room for error.
(suspenseful music)
Coelurosauravus is merely a first step
on the road to flight.
This gliding reptile has no doubt played a part.
Maybe not in the full extension of giant insects,
but in any case, we have a super predator
regularly attacking them and we can therefore assume
that this was one element in the decline
of giant insects at the time.
If Coelurosauravus was not the only culprit,
it was certainly the first to put pressure on giant insects
before any others took to the skies.
This animal guarding the entrance
to the Kassel Museum in Germany
is part of the Pterosaur family.
These flying reptiles appeared 230 million years ago.
Today they are completely extinct,
but scientists have discovered around 100 different species.
Could they too have been a threat to the giant insects?
Professor Eberhard Frey, or Dino as he's usually known,
is a world specialist in Pterosaurs.
Pterosaurs are flying reptiles,
and they are characterized by flight membrane
that extended from the tip of the little finger
down to the ankle.
Interesting point with these Pterosaurs
is that they have a size range which is simply unbelievable
from about 20 centimeters wingspan
up to 14 meters wingspan, which is unique.
Yet according to scientists,
very few of these Pterosaurs were insect eaters.
The only insectivores were part of the Anurognathids family,
among the smallest Pterosaurs.
We cannot imagine really that they hunted the big insects.
But probably they chased the small ones,
which are not seen in the fossil record.
The big insects however also chased small insects,
so they probably conquered about the same prey.
All the other Pterosaurs from that time we know
likely fed on something else,
and thus did not make any concurrence to the big insects,
and probably this is one of the reasons
why they persisted such a long time.
230 million years ago,
during the Triassic period,
Pterosaurs spread around Europe,
but also to what is now South America and Asia.
For the first time in the history of life on Earth,
a family of vertebrates learned to master
not just gliding, but flapping flight.
Like Anurognathids discovered in Germany,
its Asian cousin, Batrachognathus, is a flying reptile,
nocturnal, insect eating, and fast.
With its flat skull and big eyes,
Batrachognathus occupied the same ecological niche
as modern day owls.
But the comparison with birds of prey stops there.
Its enormous jaws are equipped with a dozen conical teeth.
(screeching)
No flying insect can hide from Batrachognathus Volans,
literally flying frog jaw.
Can the Caligramma, an insect with a 10 inch wingspan,
take it on?
An experiment carried out in Germany
puts the theory to the test.
Dino Frey works in collaboration
with the Institute of Fluid Mechanics
in Karlsruhe, Germany.
This wind tunnel is usually used
to refine the shape of airplanes
and improve their aerodynamics.
But today the paleontologist is using it
to test the Pterosaur's flying abilities.
A resin and carbon fiber model of Anurognathids
is placed in the wind tunnel.
We are at the beginning of our studies,
but what we learned so far is that Pterosaurs
likely were extremely slow fliers,
so they could cope with wind speeds
around 40 kilometers per hour or less,
probably these guys needed to flap their wings
to stay in the air, and they were not very good gliders.
But flapping wings also means that they were
as active fliers much more maneuverable,
and this is again interesting when they started
to chase insects on the wing.
When Pterosaurs appeared,
insects lost the monopoly on flapping flight.
Batrachognathus was indeed capable
of leaving the tree lined shore
to chase insects out in the open,
which his predecessor, Coelurosauravus the flying lizard,
was unable to do.
The Pterosaurs seem to have had more of an impact
on the giant insects' prey
than on the giant insects themselves,
contributing to their final decline
but not fully explaining their extinction.
(mysterious music)
On the other side of the Atlantic,
one American researcher suggested other culprits
in a study published in August 2012.
This paleontologist specializes in the extinction
that occurred at the end of the Permian period
250 million years ago.
More at home in front of a computer
than wielding a trowel in the field,
Matthew Clapham is a database devotee.
It took him a year and a half to collect
the information needed to publish his survey
on the decline of giant insects.
He has undertaken a mammoth task.
Gathering the sizes of all fossil wings
since the first scientific publications.
We compiled this very large database
with nearly 10,000 insect species
by simply getting published papers
where paleontologists had found insect fossils
and described them and given them a name.
Clapham discovered that during
the first part of their history,
insect size changed with the level
of oxygen in the atmosphere.
As oxygen declined, they diminished in size,
and as it grows, their size increased.
So this pattern holds for the first
200 million years or so of insect history,
but then beginning in the late part of the Jurassic period,
around 150 million years ago,
we can see insects become smaller,
even though atmospheric oxygen is going up at this time.
And this coincides quite closely with the evolution
of Archaeopteryx, the first bird.
The ancient ancestors of the birds
first appeared during the Jurassic period
160 million years ago.
The oldest fossils come from China.
At that time, forests of giant conifers
offered a fantastic launchpad to conquer the sky.
An ecological niche that was quickly seized
by a new generation of creatures learning to fly.
Small dinosaurs, like this Anchiornis,
had feathers on their arms and legs,
and used them as wings.
(screeching)
The claws on their wings enabled them to gain altitude
and get good vantage points.
Insects like this Jerusin Brophlibia
had to hide in the trees to survive.
As soon as it takes off, it become visible
and is hunted down by Anchiornis.
While only a few Pterosaurs like Anurognathids ate insects,
all bird ancestors did.
Increasingly skilled at flying,
they would become fierce insect predators.
In the Cretaceous period,
when these first birds are evolving,
there would've been increased predation pressure
on these large insects in particular
as they were less maneuverable than the smaller insects.
In addition to this increased predation,
there was likely competition between birds and insects,
especially these large predatory insects,
for the same food sources,
and so both of those factors likely led to
a decrease in insect size.
This competition between birds and insects
still happens today.
Just like flying lizards and Pterosaurs,
birds would've had an influence on the size of insects.
But why have giant insects completely disappeared,
leaving only today's small insect population?
A last clue could provide an answer.
It came from a fossil rich site
close to where Anchiornis was found,
in the Chinese region of Liaoning, northeast of Beijing.
The numerous eruptions that shook the region
125 million years ago have helped preserve certain plants
from the period in volcanic ash,
including the ancestors of flowering plants.
Discovered in 2002 by the paleobotanist Sun Ge,
they would've had an unexpected impact
on the extinction of the last large sized dragonflies.
And here in China, in the west valley,
we found the oldest known (mumbles)
called the Archaefructus.
This is Archaefructus,
the first flower to appear on our planet.
On this fossil seen through a microscope
we can distinguish the male organs,
the stamens that contain the pollen
and the piston, the female organ.
These characteristics allow Sun Ge to confirm
that this fossil belongs to the Angiosperm,
a family of plants whose seeds are enclosed inside a fruit,
unlike conifers.
According to the paleobotanist,
these plants were aquatic, and grew on lake shores.
But what does the appearance of the first flowering plants
have to do with the extinction of large carnivorous insects?
Andre Nel believes these two events are linked.
Many families of insects disappeared at that time,
and others managed to adapt to angiosperms,
which proliferated and began to diversify
to produce more or less our modern forests.
The impact was also very significant for dragonflies
during that same period.
Could the decline of giant insects
have something to do with the dragonfly's original shape?
Because before they were able to fly,
they were aquatic creatures.
Their life began underwater.
For the first few years, they existed as larvae,
and just like their cousins the mayflies,
they fed on other aquatic insect larvae.
When flouring planets such as Archaefructus
appeared on the lake shores 125 million years ago,
the larvae's life conditions changed.
The plants took root in shallow waters,
but then opened their flowers in the air.
When they withered, their petals and leaves
floated on the surface before sinking to the bottom.
This material is digested by the microorganisms
present in the water, but to do this,
the organisms use the oxygen contained in the water,
leaving little oxygen available for the dragonfly larvae.
These dragonflies may have disappeared at that time
because their larvae could not adapt
to this change in the aquatic ecosystem,
and they were replaced by other dragonflies.
The emergence of flowering plants
completely modified the lake's ecosystem,
and would've led to the extinction
of the last large sized insects
which have gradually declined since the Carboniferous.
(suspenseful music)
The extinction of arthropods and giant insects
over millions of years of evolution
teaches us that it took many protagonists
to cause the extinction of these species.
A change in the composition of oxygen in the atmosphere,
the emergence of new predators like flying lizards,
some Pterosaurs, and the bird ancestors,
and finally, the birth of flowers.
In the early 21st century,
which are the largest insects that inhabit our planet?
Today, insects can reach the size of a hand,
but very few are bigger than this Chinese cricket,
for we are at the dawn of a new phase of extinction
caused by humans,
since the onset of the Industrial Revolution.
(speaking foreign language)
The large insects live mostly in tropical
or intertropical climates.
They are in danger since the habitat is at risk.
If the forest in which the giant stick insect lives
is in danger, the giant butterfly will of course disappear.
I certainly hope that we will continue to see them,
but certainly with the rate of habitat destruction
that's going on throughout the world,
particularly in the tropical environments
where many of these species occur,
it is very likely that a lot of them will be lost,
just like the giant insects.
(thunder rumbling)
(dramatic music)