Documentary, Ancient Earth - S2 E1 What Killed The Giant Insects
#GiantInsects #AncientEarth #Documentary #Prehistoric
#GiantInsects #AncientEarth #Documentary #Prehistoric
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00:28Dragonflies the size of hawks, centipedes larger than humans, a strange menagerie of
00:57giant insects and amphibians reigned over the earth 300 million years ago.
01:06Over time these huge creatures shrunk in size or disappeared.
01:13The reasons for their progressive extinction remain controversial.
01:25358 million years ago, the continents came together to form the supercontinent, Pangaea.
01:33This was the beginning of the Carboniferous period.
01:36Oxygen levels in the air were much higher back then, 35% compared to today's 21%.
01:43For the first time on earth, giant trees stored carbon dioxide and released oxygen in abundance.
01:53Human beings would not have survived in this high oxygen atmosphere.
01:59But for some swamp dwellers, it was ideal.
02:02Like Arthroplura, measuring up to 10 feet.
02:07This long-lost cousin of the centipedes was a herbivore.
02:12Formeganoia, with a wingspan up to 25 inches, this member of the dragonfly family is the largest
02:20known flying insect ever discovered, a tireless predator.
02:24It had no airborne competitors at the time since birds and flying reptiles didn't exist yet.
02:30The high oxygen levels in the atmosphere give the characteristic sepia color to the sky during
02:52the Carboniferous period.
02:55Oxygen also makes the air extremely flammable.
02:58Such a hostile world is hard for us to imagine.
03:21Lightning storms could set aflame the immense forests and their inhabitants.
03:27And yet giant insects thrived.
03:28Later, when fires became less frequent, these astonishing creatures simply disappeared.
03:46Scientists are trying to determine what caused that extinction.
03:48There are several possible culprits.
03:49In fact, it's a bit like an Agatha Christie novel, when there's not one, but several murders.
04:03It's our job to take the clues we have and reconstruct the investigations in order to come up with the most likely scenario.
04:10While we've known about giant insects since the 19th century, paleontologists did not understand why they had disappeared.
04:18For a long time, a change in the composition of the atmosphere was the only explanation.
04:23But at the beginning of the 21st century, the discovery of fantastic fossil insects and their predators opened up new possibilities.
04:31While that's a wonderful hypothesis, and assuredly something was preying upon these giant insects, we don't have great evidence for it.
04:40Around the world, American, European, and Chinese scientists confront the old theories using new fossil discoveries unearthed by groundbreaking technology.
04:50The earliest giant insect fossils were found in the French region of Allier in 1880.
05:07Under the surface of this pond were the remains of animals that had died 350 million years ago during the Carboniferous period.
05:15Meganeuros.
05:18Now extinct, these tireless predators are the largest flying insects that ever existed.
05:24This abandoned industrial site was an important coal field in the 19th century.
05:29And as the coal was dug out, fossils were discovered close to the town of Comandry.
05:36The owner of the coal mine, Mr. Moni, gave his name to the specimen that is preserved at the Natural History Museum in Paris.
05:44Meganeura Moni.
05:46André Nel, a paleontologist whose speciality is early insects, watches over this valuable piece.
05:57Miners would look for fossils to make a little extra money.
06:01And one day when they were opening slabs, they came across this animal.
06:06Unfortunately, when they were digging it out, they hit it four times with a pick and we lost its head.
06:12They were the super predators of the time, predators of other insects that were also very big.
06:17These large sized fossils are quite exceptional.
06:23While thousands of insects were found on the site of Comandry, only five Meganeuras were ever discovered.
06:30Meganeura, like all other insects, had four wings.
06:35Two on each side attached to the thorax in the centre.
06:39In front you had a head with big eyes because it was a predator.
06:42So its eyes, just like modern dragonflies, were used to see its environment in 360 degrees.
06:48So possibly even behind the animal.
06:51To better understand how this extinct animal once lived, we must step back 300 million years in time.
07:00This is what the French region of Allier would have looked like then.
07:13A giant swamp scattered with cypresses.
07:20Humidity, at nearly 100%, made the atmosphere dense.
07:25And allowed Meganeura to easily carry its heavy exoskeleton into the air.
07:32It is part of a genus that is extinct today.
07:35But it looks much like modern dragonflies.
07:38And is part of the same Odonatoptera super order.
07:43With wings that functioned independently of each other, Meganeura was agile in flight.
07:49But unlike its contemporary cousins, it couldn't fold its wings.
07:53Faced with this efficient airborne predator, vegetarian insects such as Paleodictyoptera had to keep themselves out of sight.
08:17By comparing its anatomy to modern dragonflies,
08:20we can guess at Meganeura's main physical characteristics.
08:24One, it could fly over 40 miles per hour.
08:33Two, it was a sight predator.
08:35Its head was independent from the rest of its exoskeleton,
08:38so it could keep it still while flying and focus on its prey.
08:43Three, it had a huge appetite.
08:47It could eat its own weight in food every 30 minutes.
08:52To catch all this food, Meganeura had an array of attributes identified in fossils.
08:58But what might explain its giant signs?
09:12Away from the public is the museum's library of species,
09:15where they keep the specimens that scientists study.
09:18Here we find Meganeuras and their prey, both reaching impressive sizes.
09:24So here you have an example of a Meganeura, on which we see the base of its wings, the thorax,
09:39but what is most spectacular are the four legs equipped with strong spines that were used to stab prey.
09:46But the Meganeura's prey were also large-sized insects, like the Palaeodictoptera.
09:53You just have one wing from here to here, so you can imagine the whole thing.
10:01These were Meganeura's prey.
10:04They were big guys too.
10:06Big insects to escape big predators.
10:09So in this case, we have an arms race between predators and prey.
10:16But this battle to be the biggest between Meganeura and its prey seems to have had its limits.
10:22Otherwise, paleontologists would certainly have found even bigger and more terrifying flying insect fossils.
10:32Most of Meganeura's day was spent looking for food, since its metabolism required a lot of energy.
10:37According to scientists, a huge size of insects during the Carboniferous period was possible because of the high levels of oxygen in the air.
10:53Insects don't have lungs, but instead use a unique system of tubes, trachea and trachea to bring air directly to their organs, including their digestive system.
11:04The downside to this system is it lacks efficiency.
11:11Air travels through the tissues in the form of gas.
11:16The bigger an insect is, the more oxygen it needs.
11:21It is very strange that these animals reach these sizes, because nowadays we do not have such big insects.
11:27And at the time of the dinosaurs, when we had large vertebrates, insects were much smaller.
11:36It turns out that in the Carboniferous period, for reasons linked to geochemistry, the oxygen rate in the atmosphere was higher than it is today,
11:45which encouraged the development of animals such as the large insects.
11:52Meganeuras could not survive in today's atmosphere, because not enough oxygen would reach their organs, including their brains.
11:59And they would faint.
12:05Since the beginning of the 20th century, scientists have proposed a link between the size of insects and the concentration of oxygen.
12:14But it wasn't until 2007 that an experiment finally proved it.
12:19In the Chicago suburbs, the Argonne National Laboratory houses the United States' most powerful synchrotron,
12:31a scanner that generates the brightest X-ray beams in the Northern Hemisphere.
12:36The distance around the particle accelerator is more than half a mile.
12:48So Jake Soka, the scientist in charge of the study, uses a trike to get around.
12:58Today, live insects are being put under the scanner.
13:02We use the idea that you can take living insects and make inferences about insects that existed in the past.
13:10What 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.
13:19So the idea of this hypothesis is that when you have more oxygen, your insects can get larger,
13:25and when you have less oxygen, insects will get smaller in response.
13:29But no one had really ever tested this hypothesis before.
13:34So we use synchrotron X-rays to look inside the animal to study the dimensions of their tracheal system.
13:42This particle accelerator generates extremely intense and focused X-rays that pass through the insect's body.
13:49Our purpose is to see the tracheal system in action.
13:52And some of the tracheal tubes are really small, and we want to see it in the living animal.
13:58So this is really the only technique where we can do all of those things.
14:01For the first time scientists are able to actually observe an insect breathing.
14:19Using this experiment, they discovered that crickets not only breathe passively, but also use their whole bodies to carry air to their organs.
14:30And you can see that bubble in the gut moves forward to the head, and it moves backward.
14:38And every time it's doing that, it's synchronized with the compression of the tracheal system.
14:44The movements that you see here are not a passive effect.
14:49This is an active movement by the animal, and the ultimate cause of it are contraction of muscles.
14:55Just as this cricket contracts its digestive system to send air to its organs,
15:01Meganeura would have contracted its abdomen to absorb the thick carboniferous air.
15:06The elastic exoskeleton would resume its shape once the muscles had completed their action.
15:11But beyond the discovery of this internal movement, what interests Jake Soka is the space occupied by the respiratory system within the insects' bodies?
15:30He has compared beetles of different sizes to study the link between their size and that of their respiratory system.
15:44And 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.
15:54So what we think, based on the study, is that if you would make this even larger, so if we would scale this up farther and farther,
16:03eventually you reach a limit where you can't stuff more tracheal system inside the animal because you have to have other things like muscles and gut and nervous tissue,
16:15fat bodies, things like that, that are all important for the physiology of the animal.
16:20You can't just have one big tracheal system.
16:23The higher oxygen concentration of the carboniferous period meant that insects required fewer respiratory tubes and could therefore grow to a larger size.
16:34But with the modification of the atmosphere, the giant insects had to reduce their size over millions of years of evolution.
16:42And not all of them survived these changes.
16:45290 million years ago, during the Permian period, oxygen levels decreased from 35% to 23%, close to today's level.
16:55And Gia had already formed a supercontinent extending from one pole to the other. Surrounded by a single ocean, it was subject to extreme climatic conditions.
17:07The heart of the continent suffered drastic temperature changes, and deserts appeared.
17:13But at the equator, heavy rainfall allowed the great forests from the Carboniferous Era to survive.
17:19During 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.
17:33This 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.
17:46The fungus stopped the accumulation of carbon on the ground, and instead it was recycled into the atmosphere.
18:00The proportion of oxygen in the air decreased gradually, with major consequences for the environment.
18:06This transitional period brought about the demise of Arthropleura, a distant relative of the centipedes.
18:21But why did the first giants of the Carboniferous Period disappear?
18:26Could their lifestyle be responsible?
18:28In 1977, Arthropleura fossils were found in Nautin, in the heart of the French countryside.
18:41The slag heaps surrounding this former mining town are hallmarks of its industrial past.
18:46In the local Natural History Museum, tribute is paid to the miners who discovered fossils while they were working.
18:52Among them, this impressive set of footprints, the most important ever found in France.
19:02They are examined by Sylvain Chabonnier, a specialist in arthropods, the family of invertebrates that includes insects and centipedes.
19:11Here you can see a set of tracks. You have two trails that are parallel.
19:16This was made by an organism of quite a respectable size, an animal that must have measured around three feet long.
19:22It's just a fragment of the track that was probably much bigger.
19:28Unfortunately, no adult-sized fossil has been discovered.
19:31But the paleontologists have found many smaller specimens in these coal deposits.
19:39You can see here what this little creature looked like.
19:42These are juvenile specimens, which are tiny.
19:44Here is a complete specimen with its shell that is well preserved.
19:48So obviously this organism, as it grows, will produce larger trails when it moves.
19:53Arthropleura was rather similar to modern centipedes.
19:58It could reach ten feet in length and it crawled on the ground or up trees in search of food.
20:04Life in the rainforests during the early Permian period was quite similar to that of the Carboniferous period.
20:22And there was enough oxygen in the atmosphere for Arthropleura to thrive and face unexpected predators such as Eriops.
20:36This amphibian locates Arthropleura using cells in its skin that detect vibrations on the tree trunk.
20:47The Arthropleura had a considerable advantage.
20:50The claws at the ends of its articulated legs allow it to grip the trunk.
20:54And its protective shell shields it against attackers.
20:56Arthropleura's disappearance may not have been caused by predators, but by decreasing food supplies.
21:19This creature was a herbivore. At the time it would have had plenty to eat.
21:29At that time the vegetation was equatorial or tropical, so it was an extremely lush vegetation with a great variety of plants.
21:39These plants are in fact the origin of coal.
21:42Arthropleura lived in this forest environment.
21:44You also have on the other side trees and leaves that were found in Arthropleura's stomach contents.
21:51So it probably fed on these tree branches.
21:54Did they eat from trees lying on the ground or did they climb trees?
21:57These are hypotheses we will probably never know for sure.
22:01These fossilized plants have been so well preserved that they still appear alive.
22:07But as they began to disappear, Arthropleura had to adapt.
22:11This forest environment will tend to dry out at the end of the Carboniferous.
22:16The climate will change, the vegetation will disappear, and Arthropleura will lose its food source.
22:22Which is probably one reason that explains its extinction.
22:26Over a period of 10 million years, the atmosphere and the climate gradually changed, bringing about the demise of Arthropleura.
22:35The most recent fossils we have date from about 280 million years ago.
22:41Evolution could have retained smaller and more energy efficient insects.
22:46However, in 2009, scientists were surprised to find new Meganeura fossils in the south of France.
22:52These specimens, discovered on sites dating from the end of the Permian period, prove that the declining oxygen rate cannot be the sole explanation for the extinction of giant insects.
23:06What clues did these unexpected fossils review?
23:17These deposits are scarce. Scientists know of only about 15 of them in the world, and like here, they've not been all fully excavated.
23:25This beautiful landscape, with its typical red rock, is located less than an hour from the French Riviera.
23:38This is one of the sites excavated by André Nel.
23:41Here we are, 250 million years into the red continental Permian.
23:53Red Permian because the rocks have become oxidized. The iron is oxidized and has become red.
23:59So 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.
24:09But fortunately, fossils have been found in other deposits.
24:14It's in a similar geological layer that insect fossils from the Permian period were discovered in 2009, close to the French city of Montpellier.
24:22For a long time, we thought that these giant dragonflies had existed during the Carboniferous period and at the beginning of the Permian.
24:28But they no longer existed towards the middle and end of the Permian.
24:31But we were surprised to discover dragonflies that were as big as those from the Carboniferous.
24:35Paleontologists were perplexed since the level of oxygen had already decreased by that period.
24:42In theory, giant insects should have disappeared, but the specimens of different sizes conserved in André Nel's laboratory in Paris proved that they were still around.
24:52There are tiny wings of the Meganuridae like this one here.
24:57This is the size of a modern dragonflies wing.
25:01We have much bigger species.
25:05Here is the rear wing of another Meganuridae, another species.
25:08This one too was a giant.
25:12We have bigger ones but only fragments.
25:15This here is a piece of Meganuridae's wing.
25:18The size is comparable to that of the Meganuridae of the Coniferous.
25:22We estimate that its wingspan is around 23 inches.
25:25We see that with these animals there is great diversity.
25:28It's during this time that they become the most diversified.
25:30We have small ones, medium ones, big ones and very big ones.
25:35This means they had not really become extinct at this period.
25:38This does not sit well with the scenario of extinction due to decrease in the level of oxygen.
25:43These recently discovered species of Meganuridae found in France have also turned up in the United States.
25:50Evidence of their existence is accumulating.
25:53Here is what the Earth looked like during the middle of the Permian period.
26:00A hot and humid world covered with tropical forests.
26:04With an oxygen rate just slightly higher than today.
26:08One animal species survived against all odds.
26:12Meganuridae, represented by this Meganuropsis.
26:17This specimen, discovered in Texas, is as large as its French cousins.
26:21But how can an insect measuring nearly two feet survive breathing air that was much poorer in oxygen than in the past?
26:31Did it have an advantage that Arthropleura did not?
26:44The Meganuropsis fossil was discovered in 1937, next to Kansas City in the USA.
26:49Professor Michael Engels is a paleoentomologist who has worked at the University of Canvass for the past 20 years.
27:05Author 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.
27:17These are some of the large insects that occur today.
27:22Large moths, stick insects, beetles, dragonflies and damselflies.
27:27And while they're pretty impressive in their size, none of them can compare to the giant insects of the past.
27:34According to Engels, one asset which might have enabled Meganuris to survive during the Permian period, despite the lower oxygen levels, is the movement of their wings.
27:43You would have an easier chance of getting a large flying insect than you would a large insect that doesn't fly.
27:53Wings 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 sacs and move air through the body.
28:03Flight 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 tissue within them by getting oxygen into an area where a wingless insect or other arthropod would not be able to.
28:20This full-body ventilation could be the secret to meganeoropsis' survival.
28:27The movement of its wings quickly brings air to the trachea, which then supplies the organs with oxygen.
28:33While the ground-dwelling giants of the carboniferous period disappeared, this advantage would have allowed Meganuris to continue ruling the skies during the Permian period, remaining at the top of the food chain in the swamps.
28:53This Diplocorvus, a now extinct amphibian, has no chance of going unnoticed, betrayed by its need for air.
29:04Meganuropsis sees it as soon as it leaves the water surface, thanks to eyes that are extremely sensitive to movement, shapes and colors.
29:13Are we standing in front of the water at the bottom?
29:14Let's go.
29:15C Extensionnage
29:16Let's go.
29:17Gamers
29:18Let's go.
29:19C Extensionnage
29:20Let's go.
29:21Smoking water
29:23Ceat
29:23The EPA
29:25The EPA
29:26How do you want help is able to cover me?
29:27To the EPA
29:29Let's go.
29:40What is the EPA
29:41Meganeurids were the super predators of the time, and their wings enabled them to survive
29:57despite falling levels of oxygen.
30:00So what caused their extinction?
30:03No Meganeurid fossils have been discovered from after the Permian period.
30:07Today, scientists still don't know exactly when they disappeared,
30:11but other large-sized dragonflies survived the next 130 million years.
30:17To explain the extinction of these giants, scientists are now contemplating the emergence of new predators.
30:24While insects were the only flying creatures during the first part of their history,
30:30other animals took to the skies during the later Permian period,
30:33between 300 and 250 million years ago, of what was to become, eventually, Europe.
30:40Jean-Sébastien Steyer,
30:55paleontologist at the Natural History Museum in Paris,
30:58is the leading French specialist in early vertebrates.
31:02He has come to the legendary paleontology gallery
31:05to collect a very important specimen for the study of insect predators.
31:11Though smaller in size than many other fossils,
31:14this was the first of its species to possess a major advantage.
31:18This is the fossil of a gliding reptile that is about 250 million years old
31:32and has the strange name of Cilius oravus.
31:36This reptile actually developed gliding flight.
31:41The ability to glide allows an animal to catch prey in the air,
31:45like the giant insects.
31:52The planet continued to heat up at the end of the Permian period.
31:57Swamps, an infinite source of fossils,
32:00now had aquatic plants characteristic of stagnant waters.
32:06Like the insects during the Carboniferous period,
32:10reptiles were just starting to try out life in the trees and flying.
32:13Amongst them, Cilius oravus would become an outstanding insect hunter,
32:19thanks to its retractable wings.
32:25It had a very unusual and interesting anatomy.
32:29Its fairly small head was a triangular shape.
32:31On its skull, we can see small conical pointed teeth.
32:35They were probably used to crack the hard exoskeletons of insects.
32:39And of course, the main characteristic of this gliding reptile
32:43are its stick-shaped bones that start around the armpits
32:46and enable this animal to throw itself in the air and base jump.
32:50We can well imagine it climbing up this microscope, for instance,
32:54and then jumping.
32:58We can even imagine it climbing with its small claws
33:01and then unfolding its wings to glide.
33:04So we can picture the race between Cilius oravus
33:07and the flying insects living at that time.
33:09Only 16 inches long, this small reptile couldn't catch Meganeurus.
33:17But it could compete for the same prey, the Paleodictyoptera.
33:22To catch its victim, it has to take the plunge.
33:25Cilius oravus can't flap its wings to catch flying insects.
33:38It relies on an element of surprise.
33:48And its ability to glide.
33:55There is no room for error.
34:17Cilius oravus is merely a first step on the road to flight.
34:25This gliding reptile has no doubt played a part.
34:29Maybe not in the full extension of giant insects.
34:32But in any case, we have a super predator regularly attacking them
34:36and we can therefore assume that this was one element
34:39in the decline of giant insects at the time.
34:44If Cilius oravus was not the only culprit,
34:47it was certainly the first to put pressure on giant insects
34:51before any others took to the skies.
34:54This animal guarding the entrance to the Karlsruhe Museum in Germany
35:01is part of the Pterosol family.
35:05These flying reptiles appeared 230 million years ago.
35:10Today, they are completely extinct.
35:13But scientists have discovered around 100 different species.
35:18Could they, too, have been a threat to giant insects?
35:21Professor Eberhard Frey, or Dino as he's usually known,
35:27is a world specialist in pterosaurs.
35:30Pterosaurs are flying reptiles
35:32and they are characterized by a flight membrane
35:36that extended from the tip of the little finger down to the ankle.
35:41The interesting point with these pterosaurs is that
35:44they have a size range which is simply unbelievable,
35:48from about 20 centimetres wingspan up to 14 metres wingspan,
35:53which is unique.
35:55Yet according to scientists,
35:57very few of these pterosaurs were insect eaters.
36:01The only insectivores were part of the Anuragnatis family,
36:05among the smallest pterosaurs.
36:07We cannot imagine, really, that they hunted the big insects.
36:13But probably, they chased the small ones,
36:15which are not seen in the fossil record.
36:18The big insects, however, also chased small insects,
36:22so they probably conquered about the same prey.
36:26All the other pterosaurs from that time we know
36:28likely fed on something else
36:31and thus did not make any concurrence to the big insects.
36:35And probably, this is one of the reasons
36:37why they persisted such a long time.
36:44230 million years ago, during the Triassic period,
36:48pterosaurs spread around Europe,
36:51but also to what is now South America and Asia.
36:55For the first time in the history of life on Earth,
36:58a family of vertebrates learn to master
37:01not just gliding, but flapping flight.
37:05Like Anuragnatis, discovered in Germany,
37:08its Asian cousin, Batrachognathis,
37:11is a flying reptile,
37:14nocturnal, insect-eating, and fast.
37:19With its flat skull and big eyes,
37:22Batrachognathis occupies the same ecological niche
37:25as modern-day owls.
37:26But the comparison with birds of prey stops there.
37:32Its enormous jaws are equipped with a dozen conical teeth.
37:36No flying insect can hide from Batrachognathis volums,
37:41literally, flying frog jaw.
37:45Can the calligrama,
37:47an insect with a 10-inch wingspan,
37:49take it on?
37:50An experiment carried out in Germany
37:59puts the theory to the test.
38:08Dino Frey works in collaboration
38:10with the Institute of Fluid Mechanics
38:12in Karlsruhe, Germany.
38:13This wind tunnel is usually used
38:16to refine the shape of airplanes
38:18and improve their aerodynamics.
38:21But today, the paleontologist is using it
38:23to test the pterosaur's flying abilities.
38:25A resin and carbon fiber model
38:33of aneurognathis
38:34is placed in the wind tunnel.
38:36We are at the beginning of our studies,
38:40but what we learned so far
38:42is that pterosaurs likely were extremely slow flyers,
38:46so they could cope with wind speeds
38:48around 40 kilometers per hour or less.
38:52But probably these guys needed to flap their wings
38:55to stay in the air
38:56and that they were not very good gliders.
38:59But flapping wings also means
39:01that they were, as active flyers,
39:04much more maneuverable.
39:06And this is, again, interesting
39:07when they started to chase insects on the wing.
39:13When pterosaurs appeared,
39:16insects lost the monopoly on flapping flight.
39:21Batrachognathus was indeed capable
39:23of leaving the treeline shore
39:25to chase insects out in the open,
39:28which his predecessor,
39:30Ciliocerathus, the flying lizard,
39:32was unable to do.
39:35The pterosaurs seem to have had more of an impact
39:38on the giant insects' prey
39:39than on the giant insects themselves,
39:43contributing to their final decline,
39:45but not fully explaining their extinction.
39:55On the other side of the Atlantic,
40:08one American researcher suggested other culprits
40:11in a study published in August 2012.
40:14This paleontologist specializes in the extinction
40:21that occurred at the end of the Permian period,
40:23250 million years ago.
40:29More at home in front of a computer
40:31than wielding a trowel in the field,
40:33Matthew Clapham is a database devotee.
40:37It took him a year and a half
40:39to collect the information needed
40:40to publish his survey
40:41on the decline of giant insects.
40:44He has undertaken a mammoth task,
40:47gathering the sizes of all fossil wings
40:49since the first scientific publications.
40:53We compiled this very large database
40:56with nearly 10,000 insect species
40:59by simply getting published papers
41:03where paleontologists had found insect fossils
41:06and described them and given them a name.
41:09Clapham discovered that during the first part
41:11of their history,
41:12insect size changed
41:13with the level of oxygen in the atmosphere.
41:15As oxygen declined,
41:17they diminished in size,
41:18and as it rose, their size increased.
41:21So this pattern holds
41:22for the first 200 million years or so
41:24of insect history,
41:26but then beginning in the late part
41:28of the Jurassic period,
41:29around 150 million years ago,
41:32you can see insects become smaller,
41:34even though atmospheric oxygen
41:36is going up at this time.
41:38And this coincides quite closely
41:39with the evolution of Archaeopteryx,
41:41the first bird.
41:43The ancient ancestors of the birds
41:46first appeared during the Jurassic period,
41:49160 million years ago.
41:51The oldest fossils come from China.
41:56At that time,
41:58forests of giant conifers
41:59offered a fantastic launch pad
42:01to conquer the sky.
42:02an ecological niche
42:06that was quickly seized
42:08by a new generation
42:09of creatures learning to fly.
42:12Small dinosaurs,
42:14like this Ancheonis,
42:15had feathers on their arms and legs
42:17and used them as wings.
42:24The claws on their wings
42:26enabled them to gain altitude
42:27and get good vantage points.
42:32Insects,
42:33like this Gerasimbrophlebia,
42:35had to hide in the trees
42:36to survive.
42:38As soon as it takes off,
42:40it becomes visible
42:41and is hunted down
42:42by Ancheonis.
42:44While only a few pterosaurs,
42:46like Aneuragnathus,
42:48ate insects,
42:49all bird ancestors did.
42:52Increasingly skilled at flying,
42:54they would become
42:54fierce insect predators.
42:56In the Cretaceous period,
43:01when these first birds
43:02are evolving,
43:03there would have been
43:04increased predation pressure
43:05on these large insects
43:07in particular,
43:08as they were less maneuverable
43:09than the smaller insects.
43:12In addition to this
43:12increased predation,
43:14there was likely competition
43:15between birds and insects,
43:17especially these large
43:18predatory insects,
43:20for the same food sources.
43:22And so both of those factors
43:23likely led to a decrease
43:25in insect size.
43:27This competition
43:29between birds and insects
43:30still happens today.
43:35Just like flying lizards
43:37and pterosaurs,
43:38birds would have had an influence
43:40on the size of insects.
43:41But why have giant insects
43:44completely disappeared,
43:46leaving only today's
43:47small insect population?
43:49A last clue
43:51could provide an answer.
43:53It came from a fossil-rich site
43:55close to where
43:56Ancheonis was found,
43:59in the Chinese region
44:00of Liaoning,
44:02northeast of Beijing.
44:03The numerous eruptions
44:06that shook the region
44:07125 million years ago
44:09have helped preserve
44:10certain plants
44:11from the period
44:12in volcanic ash,
44:14including the ancestors
44:15of flowering plants.
44:19Discovered in 2002
44:20by the paleobotanist
44:22Sun Gay,
44:24they would have had
44:24an unexpected impact
44:26on the extinction
44:26of the last
44:27large-sized dragonflies.
44:30But here,
44:32in China,
44:34in the west,
44:36Liaoning,
44:37we found
44:37the oldest known
44:39Angesma
44:40we call the Archeofructus.
44:44This is Archeofructus,
44:47the first flower
44:48to appear
44:49on our planet.
45:00On this fossil,
45:01seen through a microscope,
45:03we can distinguish
45:03the male organs,
45:05the stamens
45:05that contain the pollen,
45:07and the pistil,
45:08the female organ.
45:10These characteristics
45:11allow Sun Gay
45:13to confirm
45:13that this fossil
45:14belongs to the Angiosperms,
45:17a family of plants
45:18whose seeds
45:18are enclosed
45:19inside a fruit,
45:20unlike conifers.
45:23According to
45:24the paleobotanist,
45:25these plants
45:26were aquatic
45:27and grew
45:28on lake shores.
45:30But what does
45:30the appearance
45:31of the first
45:32flowering plants
45:33have to do
45:33with the extinction
45:34of large
45:35carnivorous insects?
45:40André Nell
45:41believes these
45:42two events
45:43are linked.
45:45Many families
45:46of insects
45:47disappeared at that time,
45:48and others
45:49managed to adapt
45:49to Angiosperms,
45:51which proliferated
45:52and began to diversify
45:53to produce
45:54more or less
45:54our modern forests.
45:56The impact
45:57was also very significant
45:58for dragonflies
45:58during that same period.
46:02Could the decline
46:04of giant insects
46:05have something
46:05to do with
46:06the dragonfly's
46:07original shape?
46:09Because before
46:10they were able
46:10to fly,
46:12they were aquatic creatures.
46:14Their life began
46:15underwater.
46:17For the first few years,
46:19they existed as larvae.
46:21And just like
46:22their cousins,
46:22the mayflies,
46:23they fed on other
46:24aquatic insect larvae.
46:34When flowering plants
46:36such as Archaeophoctus
46:37appeared on the lakeshores
46:39125 million years ago,
46:41the larvae's life conditions
46:44changed.
46:46The plants took root
46:48in shallow waters
46:49but then opened
46:50their flowers
46:51in the air.
46:54When they withered,
46:55their petals
46:56and leaves
46:57floated on the surface
46:58before sinking
46:58to the bottom.
47:01This material
47:02is digested
47:03by the microorganisms
47:05present in the water,
47:06but to do this,
47:08the organisms
47:08use the oxygen
47:09contained in the water,
47:11leaving little oxygen
47:12available
47:13for the dragonfly larvae.
47:15These dragonflies
47:16may have disappeared
47:18at that time
47:18because their larvae
47:20could not adapt
47:21to this change
47:22in the aquatic ecosystem
47:24and they were replaced
47:26by other dragonflies.
47:29The emergence
47:29of flowering plants
47:30completely modified
47:32the lake's ecosystem
47:33and would have led
47:35to the extinction
47:35of the last
47:36large-sized insects
47:37which had gradually
47:38declined
47:39since the Carboniferous.
47:45The extinction
47:49of arthropods
47:50and giant insects
47:51over millions of years
47:52of evolution
47:53teaches us
47:54that it took many
47:55protagonists
47:56to cause the extinction
47:57of these species.
47:59The change
48:00in the composition
48:00of oxygen
48:01in the atmosphere,
48:02the emergence
48:03of new predators
48:04like flying lizards,
48:06some pterosaurs
48:07and the bird ancestors
48:08and finally
48:10the birth of flowers.
48:15In the early 21st century,
48:19which are the largest insects
48:20that inhabit our planet?
48:33Today, insects can reach
48:36the size of a hand
48:38but very few are bigger
48:40than this Chinese cricket
48:41for we are at the dawn
48:45of a new phase
48:46of extinction
48:47caused by humans
48:50since the onset
48:52of the Industrial Revolution.
48:57The large insects
48:59live mostly in tropical
49:01or intertropical climates.
49:04They're in danger
49:05since the habitat
49:07is at risk.
49:08If the forest
49:09in which the giant
49:10stick insect lives
49:11is in danger,
49:13the giant butterfly
49:14will of course disappear.
49:16I certainly hope
49:16that we will continue
49:17to see them
49:18but certainly
49:19with the rate
49:20of habitat destruction
49:21that's going on
49:22throughout the world,
49:23particularly in the tropical
49:24environments
49:24where many of these species occur,
49:27it is very likely
49:28that a lot of them
49:29will be lost
49:29just like the giant insects.
49:39from the
49:57of the
49:58of
49:59the
50:00of
50:01the
50:02and
50:02the
50:05the
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