1 00:00:00,690 --> 00:00:03,607 (mysterious music) 2 00:00:49,310 --> 00:00:51,810 Dragonflies the size of hawks. 3 00:00:53,070 --> 00:00:55,470 Centipedes larger than humans. 4 00:00:56,570 --> 00:01:00,620 A strange menagerie of giant insects and amphibians 5 00:01:00,620 --> 00:01:04,070 reigned over the Earth 300 million years ago. 6 00:01:05,820 --> 00:01:10,614 Over time, these huge creatures shrunk in size 7 00:01:10,614 --> 00:01:12,010 or disappeared. 8 00:01:13,210 --> 00:01:15,993 The reasons for their progressive extinction 9 00:01:15,993 --> 00:01:17,150 remain controversial. 10 00:01:25,640 --> 00:01:29,550 358 million years ago, the continents came together 11 00:01:29,550 --> 00:01:33,160 to form the supercontinent, Pangea. 12 00:01:33,160 --> 00:01:36,060 This was the beginning of the Carboniferous period. 13 00:01:36,060 --> 00:01:39,491 Oxygen levels in the air were much higher back then. 14 00:01:39,491 --> 00:01:42,480 35% compared to today's 21%. 15 00:01:44,488 --> 00:01:46,890 For the first time on Earth, 16 00:01:46,890 --> 00:01:49,970 giant trees stored carbon dioxide 17 00:01:49,970 --> 00:01:51,620 and released oxygen in abundance. 18 00:01:52,860 --> 00:01:54,760 Human beings would not have survived 19 00:01:54,760 --> 00:01:57,100 in this high oxygen atmosphere. 20 00:01:58,780 --> 00:02:02,550 But for some swamp dwellers, it was ideal. 21 00:02:02,550 --> 00:02:07,210 Like the Arthropleura, measuring up to 10 feet. 22 00:02:07,210 --> 00:02:10,630 This long lost cousin of the centipedes was a herbivore. 23 00:02:12,355 --> 00:02:16,850 Or Meganeura, with a wingspan up to 25 inches, 24 00:02:16,850 --> 00:02:19,327 this member of the dragonfly family 25 00:02:19,327 --> 00:02:23,120 is the largest known flying insect ever discovered. 26 00:02:23,120 --> 00:02:25,320 A tireless predator. 27 00:02:25,320 --> 00:02:27,330 It had no airborne competitors at the time 28 00:02:27,330 --> 00:02:30,670 since birds and flying reptiles didn't exist yet. 29 00:02:46,600 --> 00:02:48,890 The high oxygen levels in the atmosphere 30 00:02:48,890 --> 00:02:51,130 give the characteristic sepia color 31 00:02:51,130 --> 00:02:53,710 to the sky during the Carboniferous period. 32 00:02:55,260 --> 00:02:58,410 Oxygen also makes the air extremely flammable. 33 00:03:03,512 --> 00:03:06,429 (thunder rumbling) 34 00:03:17,590 --> 00:03:20,630 Such a hostile world is hard for us to imagine. 35 00:03:21,520 --> 00:03:24,840 Lightning storms could set aflame the immense forests, 36 00:03:26,170 --> 00:03:27,270 and their inhabitants. 37 00:03:33,560 --> 00:03:35,480 During this period not a day went by 38 00:03:35,480 --> 00:03:37,600 without huge forest fires, 39 00:03:37,600 --> 00:03:40,380 and yet giant insects thrived. 40 00:03:40,380 --> 00:03:42,450 Later when the first became less frequent, 41 00:03:42,450 --> 00:03:45,720 these astonishing creatures simply disappeared. 42 00:03:45,720 --> 00:03:47,310 Scientists are trying to determine 43 00:03:47,310 --> 00:03:48,900 what caused their extinction. 44 00:03:55,769 --> 00:03:57,310 There are several possible culprits. 45 00:03:57,310 --> 00:03:59,750 In fact, it's a bit like an Agatha Christie novel, 46 00:03:59,750 --> 00:04:02,490 where there's not one, but several murderers. 47 00:04:02,490 --> 00:04:04,950 It's our job to take the clues we have 48 00:04:04,950 --> 00:04:06,770 and reconstruct the investigations 49 00:04:06,770 --> 00:04:09,840 in order to come up with the most likely scenario. 50 00:04:09,840 --> 00:04:11,750 While we've known about giant insects 51 00:04:11,750 --> 00:04:13,740 since the 19th century, 52 00:04:13,740 --> 00:04:18,151 paleontologists do not understand why they have disappeared. 53 00:04:18,151 --> 00:04:20,450 For a long time, a change in the composition 54 00:04:20,450 --> 00:04:23,640 of the atmosphere was the only explanation. 55 00:04:23,640 --> 00:04:26,130 But at the beginning of the 21st century, 56 00:04:26,130 --> 00:04:28,710 the discovery of fantastic fossil insects 57 00:04:28,710 --> 00:04:32,070 and their predators opened up new possibilities. 58 00:04:32,070 --> 00:04:33,690 While that's a wonderful hypothesis, 59 00:04:33,690 --> 00:04:36,170 and assuredly something was preying 60 00:04:36,170 --> 00:04:37,410 upon these giant insects, 61 00:04:37,410 --> 00:04:39,570 we don't have great evidence for it. 62 00:04:40,430 --> 00:04:41,580 Around the world, 63 00:04:41,580 --> 00:04:44,210 American, European, and Chinese scientists 64 00:04:44,210 --> 00:04:47,207 confront the old theories using new fossil discoveries 65 00:04:47,207 --> 00:04:50,119 unearthed by groundbreaking technology 66 00:04:50,119 --> 00:04:53,790 to try and explain why these giants became extinct. 67 00:05:01,670 --> 00:05:03,700 The earliest giant insect fossils 68 00:05:03,700 --> 00:05:07,485 were found in the French region of Allier in 1880. 69 00:05:07,485 --> 00:05:09,260 Under the surface of this pond 70 00:05:09,260 --> 00:05:11,290 were the remains of animals that had died 71 00:05:11,290 --> 00:05:15,805 350 million years ago during the Carboniferous period. 72 00:05:15,805 --> 00:05:16,722 Meganeuras. 73 00:05:18,270 --> 00:05:20,840 Now extinct, these tireless predators 74 00:05:20,840 --> 00:05:23,790 are the largest flying insects that ever existed. 75 00:05:24,800 --> 00:05:27,010 This abandoned industrial site 76 00:05:27,010 --> 00:05:30,120 was an important coal field in the 19th century, 77 00:05:30,120 --> 00:05:31,770 and as the coal was dug out, 78 00:05:31,770 --> 00:05:34,680 fossils were discovered close to the town of Commentry. 79 00:05:37,110 --> 00:05:40,170 The owner of the coal mine, Mr. Monyi, 80 00:05:40,170 --> 00:05:42,660 gave his name to the specimen that is preserved 81 00:05:42,660 --> 00:05:44,940 at the Natural History Museum in Paris. 82 00:05:45,855 --> 00:05:46,688 Meganeura Monyi. 83 00:05:49,150 --> 00:05:51,020 Andre Nel, a paleontologist 84 00:05:51,020 --> 00:05:53,480 whose specialty is early insects, 85 00:05:53,480 --> 00:05:56,693 watches over this valuable piece. 86 00:05:56,693 --> 00:05:57,760 (speaking foreign language) 87 00:05:57,760 --> 00:05:59,190 Miners would look for fossils 88 00:05:59,190 --> 00:06:01,430 to make a little extra money, 89 00:06:01,430 --> 00:06:03,810 and one day when they were opening slabs, 90 00:06:03,810 --> 00:06:05,210 they cam across this animal. 91 00:06:06,580 --> 00:06:09,000 Unfortunately, when they were digging it out 92 00:06:09,000 --> 00:06:12,430 they hit it four times with a pick and we lost its head. 93 00:06:12,430 --> 00:06:14,460 They were the super predators of the time. 94 00:06:14,460 --> 00:06:17,460 Predators were other insects that were also very big. 95 00:06:20,590 --> 00:06:24,090 These large size fossils are quite exceptional. 96 00:06:24,090 --> 00:06:25,970 While thousands of insects were found 97 00:06:25,970 --> 00:06:28,010 on the site of Commentry, 98 00:06:28,010 --> 00:06:32,648 only five Meganeuras were ever discovered. 99 00:06:32,648 --> 00:06:35,930 Meganeura, like all other insects, had four wings, 100 00:06:35,930 --> 00:06:39,240 two on each side attached to the thorax in the center. 101 00:06:39,240 --> 00:06:41,660 In front you had a head with big eyes 102 00:06:41,660 --> 00:06:43,890 because it was a predator, so its eyes, 103 00:06:43,890 --> 00:06:45,810 just like modern dragonflies, 104 00:06:45,810 --> 00:06:49,120 were used to see its environment in 360 degrees. 105 00:06:49,120 --> 00:06:51,140 So possibly even behind the animal. 106 00:06:53,470 --> 00:06:54,610 To better understand 107 00:06:54,610 --> 00:06:57,310 how this extinct animal once lived, 108 00:06:57,310 --> 00:07:01,616 we must step back 300 million years in time. 109 00:07:01,616 --> 00:07:04,533 (mysterious music) 110 00:07:09,470 --> 00:07:11,660 This is what the French region of Allier 111 00:07:11,660 --> 00:07:12,960 would've looked like then, 112 00:07:14,531 --> 00:07:16,690 a giant swamp scattered with cypruses. 113 00:07:20,030 --> 00:07:25,030 Humidity at nearly 100% made the atmosphere dense 114 00:07:25,150 --> 00:07:27,440 and allowed Meganeura to easily carry 115 00:07:27,440 --> 00:07:29,880 its heavy exoskeleton into the air. 116 00:07:32,390 --> 00:07:35,710 It is part of a genus that is extinct today, 117 00:07:35,710 --> 00:07:38,897 but it looks much like modern dragonflies, 118 00:07:38,897 --> 00:07:42,140 and it's part of the same Odonatoptera superorder. 119 00:07:43,870 --> 00:07:46,630 With wings that functioned independently of each other, 120 00:07:46,630 --> 00:07:49,370 Meganeura was agile in flight, 121 00:07:49,370 --> 00:07:51,490 but unlike its contemporary cousins, 122 00:07:51,490 --> 00:07:53,670 it couldn't fold its wings. 123 00:07:56,640 --> 00:07:59,570 Faced with this efficient airborne predator, 124 00:07:59,570 --> 00:08:02,710 vegetarian insects such as Palaeodictyoptera 125 00:08:03,605 --> 00:08:05,730 had to keep themselves out of sight. 126 00:08:17,500 --> 00:08:20,736 By comparing its anatomy to modern dragonflies, 127 00:08:20,736 --> 00:08:24,290 we can guess at Meganeura's main physical characteristics. 128 00:08:25,200 --> 00:08:28,990 One, it could fly over 40 miles per hour. 129 00:08:33,410 --> 00:08:35,690 Two, it was a sight predator. 130 00:08:35,690 --> 00:08:38,870 Its head was independent from the rest of its exoskeleton 131 00:08:38,870 --> 00:08:42,010 so it could keep it still while flying 132 00:08:42,010 --> 00:08:43,610 and focus on its prey. 133 00:08:44,750 --> 00:08:47,810 Three, it had a huge appetite. 134 00:08:47,810 --> 00:08:51,300 It could eat its own weight in food every 30 minutes. 135 00:08:52,530 --> 00:08:55,700 To catch all this food, Meganeura had an array 136 00:08:55,700 --> 00:08:58,170 of attributes identified in fossils. 137 00:08:59,113 --> 00:09:01,446 (crunching) 138 00:09:02,791 --> 00:09:06,210 But what might explain its giant size? 139 00:09:12,560 --> 00:09:15,510 Away from the public is the museum's library of species, 140 00:09:15,510 --> 00:09:18,950 where they keep the specimens that scientists study. 141 00:09:18,950 --> 00:09:22,110 Here we find Meganeuras and their prey, 142 00:09:22,110 --> 00:09:24,500 both reaching impressive sizes. 143 00:09:31,502 --> 00:09:32,335 (speaking foreign language) 144 00:09:32,335 --> 00:09:34,790 So here you have an example of a Meganaeura, 145 00:09:34,790 --> 00:09:37,920 on which we see the base of its wings, 146 00:09:37,920 --> 00:09:40,947 the thorax, but what is most spectacular 147 00:09:40,947 --> 00:09:44,720 are the forelegs equipped with strong spines 148 00:09:44,720 --> 00:09:46,770 that were used to stab prey. 149 00:09:48,564 --> 00:09:52,680 But the Meganeura's prey were also large sized insects, 150 00:09:52,680 --> 00:09:55,090 like the Palaeodictyoptera. 151 00:09:57,020 --> 00:10:00,060 You just have one wing from here to here, 152 00:10:00,060 --> 00:10:02,240 so you can imagine the whole thing. 153 00:10:03,530 --> 00:10:05,620 These were Meganeura's prey. 154 00:10:05,620 --> 00:10:07,820 They were big guys too. 155 00:10:07,820 --> 00:10:10,360 Big insects to escape big predators. 156 00:10:11,770 --> 00:10:13,950 So in this case we have an arms race 157 00:10:13,950 --> 00:10:16,500 between predators and prey. 158 00:10:16,500 --> 00:10:18,140 But this battle to be the biggest 159 00:10:18,140 --> 00:10:20,840 between Meganeura and its prey 160 00:10:20,840 --> 00:10:22,840 seems to have had its limits, 161 00:10:22,840 --> 00:10:25,220 otherwise paleontologists would certainly have found 162 00:10:25,220 --> 00:10:28,280 even bigger and more terrifying flying insect fossils. 163 00:10:32,220 --> 00:10:35,320 Most of Meganeura's day was spent looking for food 164 00:10:35,320 --> 00:10:37,880 since its metabolism required a lot of energy. 165 00:10:39,680 --> 00:10:43,270 According to scientists, the huge size of insects 166 00:10:43,270 --> 00:10:45,510 during the Carboniferous period was possible 167 00:10:45,510 --> 00:10:48,200 because of the high levels of oxygen in the air. 168 00:10:53,410 --> 00:10:57,620 Insects don't have lungs, but instead use a unique system 169 00:10:57,620 --> 00:11:00,300 of tubes, trachea, and tracheos 170 00:11:00,300 --> 00:11:02,600 to bring air directly to their organs, 171 00:11:02,600 --> 00:11:04,410 including their digestive system. 172 00:11:10,440 --> 00:11:14,990 The downside to this system is it lacks efficiency. 173 00:11:14,990 --> 00:11:18,420 Air travels through the tissues in the form of gas. 174 00:11:18,420 --> 00:11:22,040 The bigger an insect is, the more oxygen it needs. 175 00:11:23,244 --> 00:11:24,077 (speaking foreign language) 176 00:11:24,077 --> 00:11:25,630 It is very strange that these animals 177 00:11:25,630 --> 00:11:28,070 reached these sizes, because nowadays 178 00:11:28,070 --> 00:11:30,650 we do not have such big insects, 179 00:11:30,650 --> 00:11:32,620 and at the time of the dinosaurs, 180 00:11:32,620 --> 00:11:34,930 when we had large vertebrates, 181 00:11:34,930 --> 00:11:37,300 insects were much smaller. 182 00:11:37,300 --> 00:11:39,870 It turns out that in the Carboniferous period, 183 00:11:39,870 --> 00:11:42,150 for reasons linked to geochemistry, 184 00:11:42,150 --> 00:11:43,890 the oxygen rate in the atmosphere 185 00:11:43,890 --> 00:11:45,840 was higher than it is today, 186 00:11:45,840 --> 00:11:48,290 which encouraged the development of animals 187 00:11:48,290 --> 00:11:50,190 such as the large insects. 188 00:11:52,720 --> 00:11:54,150 Meganeuras could not survive 189 00:11:54,150 --> 00:11:55,760 in today's atmosphere, 190 00:11:55,760 --> 00:11:58,180 because not enough oxygen would reach their organs, 191 00:11:58,180 --> 00:12:01,270 including their brains, and they would faint. 192 00:12:05,660 --> 00:12:08,010 Since the beginning of the 20th century, 193 00:12:08,010 --> 00:12:11,381 scientists have proposed a link between the size of insects 194 00:12:11,381 --> 00:12:13,500 and the concentration of oxygen. 195 00:12:14,350 --> 00:12:16,574 But it wasn't until 2007 196 00:12:16,574 --> 00:12:19,530 that an experiment finally proved it. 197 00:12:24,522 --> 00:12:28,680 In the Chicago suburbs, the Argon National Laboratory 198 00:12:28,680 --> 00:12:32,270 houses the United States' most powerful synchrotron, 199 00:12:32,270 --> 00:12:35,040 a scanner that generates the brightest X-ray beams 200 00:12:35,040 --> 00:12:36,390 in the northern hemisphere. 201 00:12:43,460 --> 00:12:45,890 The distance around the particle accelerator 202 00:12:45,890 --> 00:12:47,940 is more than half a mile, 203 00:12:47,940 --> 00:12:51,668 so Jake Socha, the scientist in charge of the study, 204 00:12:51,668 --> 00:12:53,630 uses a trike to get around. 205 00:12:58,160 --> 00:13:01,780 Today live insects are being put under the scanner. 206 00:13:03,070 --> 00:13:05,705 We use the idea that you can take living insects 207 00:13:05,705 --> 00:13:10,705 and make inferences about insects that existed in the past. 208 00:13:10,740 --> 00:13:12,080 What we're trying to do in this study 209 00:13:12,080 --> 00:13:14,280 is to test an old hypothesis 210 00:13:14,280 --> 00:13:16,650 that the amount of oxygen in the atmosphere 211 00:13:16,650 --> 00:13:19,220 is what limits insect body size. 212 00:13:19,220 --> 00:13:22,060 So the idea of this hypothesis is that 213 00:13:22,060 --> 00:13:25,380 when you have more oxygen your insects can get larger 214 00:13:25,380 --> 00:13:27,230 and when you have less oxygen, 215 00:13:27,230 --> 00:13:30,479 insects will get smaller in response. 216 00:13:30,479 --> 00:13:34,400 But no one had really ever tested this hypothesis before. 217 00:13:34,400 --> 00:13:38,350 So we used synchotron X-rays to look inside the animal 218 00:13:38,350 --> 00:13:40,800 to study the dimensions of their tracheal system. 219 00:13:42,320 --> 00:13:43,680 This particle accelerator 220 00:13:43,680 --> 00:13:47,150 generates extremely intense and focused X-rays 221 00:13:47,150 --> 00:13:49,570 that pass through the insect's body. 222 00:13:49,570 --> 00:13:52,790 Our purpose is to see the tracheal system in action, 223 00:13:52,790 --> 00:13:55,230 and some of the tracheal tubes are really small, 224 00:13:55,230 --> 00:13:58,640 and we want to see it in the living animal. 225 00:13:58,640 --> 00:14:00,530 So this is really the only technique 226 00:14:00,530 --> 00:14:02,330 where we can do all of those things. 227 00:14:04,074 --> 00:14:06,991 (mysterious music) 228 00:14:14,025 --> 00:14:15,960 For the first time, scientists are able 229 00:14:15,960 --> 00:14:18,880 to actually observe an insect breathing. 230 00:14:21,021 --> 00:14:22,550 (chattering) 231 00:14:22,550 --> 00:14:25,100 Using this experiment, they discover that crickets 232 00:14:25,100 --> 00:14:27,350 not only breathe passively, 233 00:14:27,350 --> 00:14:28,930 but also use their whole bodies 234 00:14:28,930 --> 00:14:30,810 to carry air to their organs. 235 00:14:32,830 --> 00:14:35,190 And you can see that bubble in the gut 236 00:14:35,190 --> 00:14:38,440 moves forward to the head and then it moves backwards, 237 00:14:38,440 --> 00:14:41,734 and every time it's doing that, it's synchronized 238 00:14:41,734 --> 00:14:44,390 with the compression of the tracheal system. 239 00:14:44,390 --> 00:14:45,940 The movements that you see here 240 00:14:45,940 --> 00:14:48,690 are not a passive effect. 241 00:14:48,690 --> 00:14:51,740 This is an active movement by the animal, 242 00:14:51,740 --> 00:14:56,190 and the ultimate cause of it are contraction of muscles. 243 00:14:56,190 --> 00:14:57,280 Just as this cricket 244 00:14:57,280 --> 00:15:01,400 contracts its digestive system to send air to its organs, 245 00:15:01,400 --> 00:15:03,670 Meganeura would've contracted its abdomen 246 00:15:03,670 --> 00:15:05,920 to absorb the thick Carboniferous air. 247 00:15:06,930 --> 00:15:09,620 The elastic exoskeleton would resume its shape 248 00:15:09,620 --> 00:15:12,300 once the muscles had completed their action. 249 00:15:21,150 --> 00:15:24,250 But beyond the discovery of this internal movement, 250 00:15:24,250 --> 00:15:27,760 what interests Jake Socha is the space occupied 251 00:15:27,760 --> 00:15:30,680 by the respiratory system within the insects' bodies. 252 00:15:35,180 --> 00:15:37,760 He has compared beetles of different sizes 253 00:15:37,760 --> 00:15:39,830 to study the link between their size 254 00:15:39,830 --> 00:15:42,260 and that of their respiratory system. 255 00:15:44,230 --> 00:15:47,551 And what we found is that the tracheal tubes 256 00:15:47,551 --> 00:15:49,960 take up a larger fraction of the body 257 00:15:49,960 --> 00:15:54,380 as you go from smaller to large than you might expect, 258 00:15:54,380 --> 00:15:57,150 so what we think based on the study 259 00:15:57,150 --> 00:15:59,230 is that you would make this even larger, 260 00:15:59,230 --> 00:16:02,750 so we would scale this up farther and farther, 261 00:16:02,750 --> 00:16:04,630 eventually you reach a limit 262 00:16:04,630 --> 00:16:08,960 where you can't stuff more tracheal system inside the animal 263 00:16:08,960 --> 00:16:13,000 because we have to have other things like muscles and gut 264 00:16:13,000 --> 00:16:17,610 and nervous tissue, fat bodies, things like that 265 00:16:17,610 --> 00:16:20,270 that are all important for the physiology of the animal. 266 00:16:20,270 --> 00:16:23,088 You can't just have one big tracheal system. 267 00:16:23,088 --> 00:16:25,330 The higher oxygen concentration 268 00:16:25,330 --> 00:16:27,440 of the Carboniferous period 269 00:16:27,440 --> 00:16:31,400 meant that insects required fewer respiratory tubes 270 00:16:31,400 --> 00:16:33,780 and could therefore grow to a larger size. 271 00:16:34,830 --> 00:16:36,970 But with the modification of the atmosphere, 272 00:16:36,970 --> 00:16:39,740 the giant insects had to reduce their size 273 00:16:39,740 --> 00:16:41,960 over millions of years of evolution, 274 00:16:42,850 --> 00:16:45,610 and not all of them survived these changes. 275 00:16:46,880 --> 00:16:50,660 290 million years ago during the Permian period, 276 00:16:50,660 --> 00:16:55,040 oxygen levels decreased from 35% to 23%, 277 00:16:55,040 --> 00:16:57,230 close to today's level. 278 00:16:57,230 --> 00:16:59,430 Pangea had already formed a supercontinent 279 00:16:59,430 --> 00:17:02,030 extending from one pole to the other, 280 00:17:02,030 --> 00:17:04,091 surrounded by a single ocean. 281 00:17:04,091 --> 00:17:07,791 It was subject to extreme climatic conditions. 282 00:17:07,791 --> 00:17:09,290 The heart of the continent 283 00:17:09,290 --> 00:17:11,980 suffered drastic temperature changes 284 00:17:11,980 --> 00:17:13,469 and deserts appeared. 285 00:17:13,469 --> 00:17:16,750 But at the equator heavy rainfall allowed the great forests 286 00:17:16,750 --> 00:17:19,821 from the Carboniferous era to survive. 287 00:17:19,821 --> 00:17:22,141 (rain falling) 288 00:17:22,141 --> 00:17:24,660 (thunder rumbling) 289 00:17:24,660 --> 00:17:27,100 During this period of major climate change 290 00:17:27,100 --> 00:17:28,840 punctuated by the monsoons 291 00:17:28,840 --> 00:17:30,890 and the warming of the atmosphere, 292 00:17:30,890 --> 00:17:33,980 a living fungus appeared on the bark of trees. 293 00:17:36,240 --> 00:17:40,240 This tiny mushroom uses an enzyme to break down wood. 294 00:17:40,240 --> 00:17:43,440 Gradually plant debris and dead trees decompose 295 00:17:43,440 --> 00:17:46,630 and no longer build up on the ground to form coal. 296 00:17:52,290 --> 00:17:55,890 The fungus stopped the accumulation of carbon on the ground, 297 00:17:55,890 --> 00:17:59,920 and instead it was recycled into the atmosphere. 298 00:17:59,920 --> 00:18:03,600 The proportion of oxygen in the air decreased gradually, 299 00:18:03,600 --> 00:18:05,890 with major consequences for the environment. 300 00:18:11,290 --> 00:18:14,440 This transitional period brought about the demise 301 00:18:14,440 --> 00:18:17,910 of Arthropleura, a distant relative of the centipedes. 302 00:18:21,490 --> 00:18:24,940 But why did the first giants of the Carboniferous period 303 00:18:24,940 --> 00:18:26,490 disappear? 304 00:18:26,490 --> 00:18:28,380 Could their lifestyle be responsible? 305 00:18:32,810 --> 00:18:36,840 In 1977, Arthropleura fossils were found 306 00:18:37,856 --> 00:18:40,830 in the heart of the French countryside. 307 00:18:40,830 --> 00:18:43,310 The sag heap surrounding this former mining town 308 00:18:43,310 --> 00:18:46,300 are hallmarks of its industrial past. 309 00:18:46,300 --> 00:18:48,350 In the local natural history museum, 310 00:18:48,350 --> 00:18:51,320 tribute is paid to the miners who discovered fossils 311 00:18:51,320 --> 00:18:52,520 while they were working. 312 00:18:55,500 --> 00:18:58,634 Among them this impressive set of footprints, 313 00:18:58,634 --> 00:19:01,590 the most important ever found in France. 314 00:19:02,750 --> 00:19:05,290 They're examined by Sylvain Charbonnier, 315 00:19:05,290 --> 00:19:07,360 a specialist in arthropods, 316 00:19:07,360 --> 00:19:09,420 the family of invertebrates that includes 317 00:19:09,420 --> 00:19:11,210 insects and centipedes. 318 00:19:12,060 --> 00:19:13,680 Here you can see a set of tracks. 319 00:19:13,680 --> 00:19:15,700 You have two trails that are parallel. 320 00:19:15,700 --> 00:19:19,200 This was made by an organism of quite a respectable size, 321 00:19:19,200 --> 00:19:22,440 an animal that must have measured around three feet long. 322 00:19:22,440 --> 00:19:23,660 It's just a fragment of a track 323 00:19:23,660 --> 00:19:25,410 that was probably much bigger. 324 00:19:27,630 --> 00:19:30,010 Unfortunately no adult sized fossil 325 00:19:30,010 --> 00:19:31,810 has been discovered. 326 00:19:31,810 --> 00:19:34,890 The paleontologists have found many smaller specimens 327 00:19:34,890 --> 00:19:36,100 in these coal deposits. 328 00:19:38,759 --> 00:19:42,050 You can see here what this little creature looked like. 329 00:19:42,050 --> 00:19:44,957 These are juvenile specimens, which are tiny. 330 00:19:44,957 --> 00:19:47,330 Here's a complete specimen with its shell 331 00:19:47,330 --> 00:19:50,010 that is well preserved, so obviously this organism 332 00:19:50,010 --> 00:19:52,710 as it grows would produce larger trails when it moves. 333 00:19:55,247 --> 00:19:56,830 Arthrolpleura was rather similar 334 00:19:56,830 --> 00:19:58,330 to modern centipedes. 335 00:20:00,180 --> 00:20:01,870 It could reach 10 feet in length 336 00:20:01,870 --> 00:20:05,620 and it crawled on the ground or up trees in search of food. 337 00:20:15,840 --> 00:20:19,970 Life in the rainforests during the early Permian period 338 00:20:19,970 --> 00:20:24,033 was quite similar to that of the Carboniferous period. 339 00:20:24,033 --> 00:20:26,283 (growling) 340 00:20:27,340 --> 00:20:29,530 And there was enough oxygen in the atmosphere 341 00:20:29,530 --> 00:20:31,490 for Arthropleura to thrive 342 00:20:32,580 --> 00:20:35,440 and face unexpected predators, 343 00:20:35,440 --> 00:20:37,260 such as Eryops. 344 00:20:37,260 --> 00:20:40,870 This amphibian locates Arthropleura using cells in its skin 345 00:20:40,870 --> 00:20:42,970 that detect vibrations on the tree trunk. 346 00:20:45,265 --> 00:20:46,850 (suspenseful music) 347 00:20:46,850 --> 00:20:49,860 But Arthropleura had a considerable advantage. 348 00:20:49,860 --> 00:20:52,310 The claws at the ends of its articulated legs 349 00:20:52,310 --> 00:20:54,270 allow it to grip the trunk, 350 00:20:54,270 --> 00:20:57,530 and its protective shell shields it against attackers. 351 00:21:06,634 --> 00:21:08,967 (splashing) 352 00:21:14,160 --> 00:21:16,460 Arthropleura's disappearance may not have been caused 353 00:21:16,460 --> 00:21:19,950 by predators, but by decreasing food supplies. 354 00:21:24,460 --> 00:21:26,720 This creature was an herbivore. 355 00:21:26,720 --> 00:21:28,870 At the time, it would've had plenty to eat. 356 00:21:31,134 --> 00:21:31,967 (speaking foreign language) 357 00:21:31,967 --> 00:21:34,560 At that time, the vegetation was equatorial or tropical, 358 00:21:34,560 --> 00:21:37,010 so it was an extremely lush vegetation 359 00:21:37,010 --> 00:21:39,340 with a great variety of plants. 360 00:21:39,340 --> 00:21:41,750 These plants are in fact the origin of coal. 361 00:21:42,610 --> 00:21:45,140 Arthropleura lived in this forest environment. 362 00:21:45,140 --> 00:21:46,810 You also have on the other side 363 00:21:46,810 --> 00:21:48,440 trees and leaves that were found 364 00:21:48,440 --> 00:21:50,240 in Arthropleura's stomach contents. 365 00:21:51,085 --> 00:21:53,920 So it probably fed on these tree branches. 366 00:21:53,920 --> 00:21:55,910 Did they eat from trees lying on the ground 367 00:21:55,910 --> 00:21:57,460 or did they climb trees? 368 00:21:57,460 --> 00:22:00,560 These are hypothesis we will probably never know for sure. 369 00:22:02,360 --> 00:22:03,610 These fossilized plants 370 00:22:03,610 --> 00:22:05,130 have been so well preserved 371 00:22:05,130 --> 00:22:07,350 that they still appear alive. 372 00:22:07,350 --> 00:22:09,334 But as they began to disappear, 373 00:22:09,334 --> 00:22:12,470 Arthropleura had to adapt. 374 00:22:12,470 --> 00:22:14,772 This forest environment will tend to dry out 375 00:22:14,772 --> 00:22:16,560 at the end of the Carboniferous. 376 00:22:16,560 --> 00:22:19,460 The climate will change, the vegetation will disappear, 377 00:22:19,460 --> 00:22:22,200 and Arthropleura will lose its food source, 378 00:22:22,200 --> 00:22:25,700 which is probably one reason that explains its extinction. 379 00:22:28,350 --> 00:22:30,480 Over a period of 10 million years, 380 00:22:30,480 --> 00:22:33,920 the atmosphere and the climate gradually changed, 381 00:22:33,920 --> 00:22:37,170 bringing about the demise of Arthropleura. 382 00:22:37,170 --> 00:22:39,320 The most recent fossils we have date from about 383 00:22:39,320 --> 00:22:41,830 280 million years ago. 384 00:22:41,830 --> 00:22:43,360 Evolution could've retained 385 00:22:43,360 --> 00:22:46,490 smaller and more energy efficient insects. 386 00:22:46,490 --> 00:22:50,170 However in 2009, scientists were surprised to find 387 00:22:50,170 --> 00:22:53,680 new Meganeura fossils in the South of France. 388 00:22:53,680 --> 00:22:56,080 These specimens, discovered on sites 389 00:22:56,080 --> 00:22:58,650 dating from the end of the Permian period, 390 00:22:58,650 --> 00:23:00,890 proved that the declining oxygen rate 391 00:23:00,890 --> 00:23:03,009 cannot be the sole explanation 392 00:23:03,009 --> 00:23:05,840 for the extinction of giant insects. 393 00:23:08,544 --> 00:23:12,630 What clues did these unexpected fossils reveal? 394 00:23:16,880 --> 00:23:19,150 These deposits are scarce. 395 00:23:19,150 --> 00:23:21,700 Scientists know only about 15 of them in the world, 396 00:23:21,700 --> 00:23:25,910 and like here, they've not been all fully excavated. 397 00:23:30,840 --> 00:23:33,907 This beautiful landscape with its typical red rock 398 00:23:33,907 --> 00:23:37,450 is located less than an hour from the French Riviera. 399 00:23:39,070 --> 00:23:41,660 This is one of the sites excavated by Andre Nel. 400 00:23:47,861 --> 00:23:48,857 (speaking foreign language) 401 00:23:48,857 --> 00:23:50,820 Here we are, 250 million years 402 00:23:50,820 --> 00:23:53,180 into the red continental Permian. 403 00:23:53,180 --> 00:23:55,970 Red Permian because the rocks have become oxidized. 404 00:23:55,970 --> 00:23:58,900 The iron is oxidized and has become red. 405 00:23:59,850 --> 00:24:01,690 So we are dealing with an environment 406 00:24:01,690 --> 00:24:03,800 that is extremely rich in organisms 407 00:24:03,800 --> 00:24:05,150 that have left their impact 408 00:24:06,012 --> 00:24:07,670 but few visible fossils up to now. 409 00:24:07,670 --> 00:24:09,860 In any case, in this deposit. 410 00:24:09,860 --> 00:24:13,870 But fortunately fossils have been found at other deposits. 411 00:24:13,870 --> 00:24:15,600 It's in a similar geological layer 412 00:24:15,600 --> 00:24:17,840 that insect fossils from the Permian period 413 00:24:17,840 --> 00:24:20,060 were discovered in 2009, 414 00:24:20,060 --> 00:24:21,940 close to the French city of Montpelier. 415 00:24:21,940 --> 00:24:24,630 For a long time we thought these giant dragonflies 416 00:24:24,630 --> 00:24:26,480 had existed during the Carboniferous period 417 00:24:26,480 --> 00:24:28,070 at the beginning of the Permian, 418 00:24:28,070 --> 00:24:29,500 but they no longer existed towards 419 00:24:29,500 --> 00:24:31,050 the middle or end of the Permian. 420 00:24:31,050 --> 00:24:33,065 But we were surprised to discover dragonflies 421 00:24:33,065 --> 00:24:36,200 that were as big as those from the Carboniferous. 422 00:24:36,200 --> 00:24:37,830 Paleontologists were perplexed 423 00:24:37,830 --> 00:24:40,620 since the level of oxygen had already decreased 424 00:24:40,620 --> 00:24:42,010 by that period. 425 00:24:42,010 --> 00:24:45,620 In theory, giant insects should have disappeared, 426 00:24:45,620 --> 00:24:47,540 but the specimens of different sizes 427 00:24:47,540 --> 00:24:50,530 concerned in Andre Nel's laboratory in Paris 428 00:24:50,530 --> 00:24:53,280 proved that they were still around. 429 00:24:53,280 --> 00:24:54,113 (speaking foreign language) 430 00:24:54,113 --> 00:24:55,780 There are tiny wings in the Meganeura day, 431 00:24:55,780 --> 00:24:57,020 like this one here. 432 00:24:58,033 --> 00:25:00,470 This is the size of a modern dragonfly's wing. 433 00:25:03,092 --> 00:25:05,300 We have much bigger species. 434 00:25:05,300 --> 00:25:07,800 Here is the rear wing of another Meganeura, 435 00:25:07,800 --> 00:25:08,990 another species. 436 00:25:09,991 --> 00:25:11,890 This one too was a giant. 437 00:25:12,770 --> 00:25:14,910 We have bigger ones, but only fragments. 438 00:25:16,110 --> 00:25:18,250 This here is a piece of Meganeura's wing. 439 00:25:18,250 --> 00:25:19,640 The size is comparable to that 440 00:25:19,640 --> 00:25:22,000 of the Meganeura of the Coniferous. 441 00:25:22,000 --> 00:25:25,440 We estimate that its wingspan is around 23 inches. 442 00:25:25,440 --> 00:25:28,430 We see that with these animals there is great diversity. 443 00:25:28,430 --> 00:25:31,670 It's during this time that they become the most diversified. 444 00:25:31,670 --> 00:25:33,650 We have small ones, medium ones, big ones, 445 00:25:33,650 --> 00:25:34,860 and very big ones. 446 00:25:34,860 --> 00:25:37,160 This means they have not really become extinct 447 00:25:37,160 --> 00:25:38,290 at this period. 448 00:25:38,290 --> 00:25:40,950 This does not sit well with the scenario of extinction 449 00:25:40,950 --> 00:25:43,980 due to the decrease in the level of oxygen. 450 00:25:43,980 --> 00:25:45,830 These recently discovered species 451 00:25:45,830 --> 00:25:48,060 of Meganeuras found in France 452 00:25:48,060 --> 00:25:51,210 have also turned up in the United States. 453 00:25:51,210 --> 00:25:54,680 Evidence of their existence is accumulating. 454 00:25:54,680 --> 00:25:56,930 (suspenseful music) 455 00:25:56,930 --> 00:25:58,400 Here is what the Earth looked like 456 00:25:58,400 --> 00:26:00,710 during the middle of the Permian period. 457 00:26:00,710 --> 00:26:04,700 A hot and humid world covered with tropical forests, 458 00:26:04,700 --> 00:26:08,010 with an oxygen rate just slightly higher than today. 459 00:26:08,010 --> 00:26:11,050 One animal species survived against all odds, 460 00:26:11,050 --> 00:26:16,000 Meganeura, represented by this Meganeuropsis. 461 00:26:17,080 --> 00:26:19,227 This specimen, discovered in Texas, 462 00:26:19,227 --> 00:26:22,371 is as large as its French cousins. 463 00:26:22,371 --> 00:26:25,929 But how can an insect measuring nearly two feet 464 00:26:25,929 --> 00:26:29,350 survive breathing air that was much poorer in oxygen 465 00:26:29,350 --> 00:26:30,940 than in the past? 466 00:26:32,130 --> 00:26:35,220 Did it have an advantage that Arthropleura did not? 467 00:26:43,540 --> 00:26:46,646 The Meganeuropsis fossil was discovered in 1937 468 00:26:46,646 --> 00:26:49,800 next to Kansas City in the USA. 469 00:26:53,010 --> 00:26:56,110 Professor Michael Ingalls is a paleoentomologist 470 00:26:57,990 --> 00:27:00,120 who has worked at the University of Kansas 471 00:27:00,120 --> 00:27:01,510 for the past 20 years. 472 00:27:05,012 --> 00:27:07,320 Author of the definitive work 473 00:27:07,320 --> 00:27:09,770 on the evolution of the insects, 474 00:27:09,770 --> 00:27:12,124 he is also the head of this collection 475 00:27:12,124 --> 00:27:15,300 containing 4.7 million specimens, 476 00:27:15,300 --> 00:27:17,440 most of them contemporary insects. 477 00:27:19,080 --> 00:27:22,070 These are some of the large insects that occur today, 478 00:27:22,070 --> 00:27:25,200 large moths, stick insects, beetles, 479 00:27:25,200 --> 00:27:27,311 dragonflies, and damsel flies, 480 00:27:27,311 --> 00:27:30,370 and while they're pretty impressive in their size, 481 00:27:30,370 --> 00:27:33,680 none of them can compare to the giant insects of the past. 482 00:27:34,554 --> 00:27:36,720 According to Ingalls, 483 00:27:36,720 --> 00:27:38,840 one asset which might've enabled Meganeuras to survive 484 00:27:38,840 --> 00:27:42,640 during the Permian period despite the low oxygen levels 485 00:27:42,640 --> 00:27:44,210 is the movement of their wings. 486 00:27:46,020 --> 00:27:48,190 You would have an easier chance getting 487 00:27:48,190 --> 00:27:50,257 a large flying insect than you would 488 00:27:50,257 --> 00:27:53,610 a large insect that doesn't fly. 489 00:27:53,610 --> 00:27:56,470 Wings are vital not only for the movement of the organism, 490 00:27:56,470 --> 00:27:59,780 but as the muscles contract to move the wings up and down, 491 00:27:59,780 --> 00:28:01,920 they actually press up against the air sacks 492 00:28:01,920 --> 00:28:03,780 and move air through the body. 493 00:28:04,670 --> 00:28:08,450 Flight actually confers an advantage to the giant insects 494 00:28:08,450 --> 00:28:10,867 in the fact that the actual movement of the flight muscles 495 00:28:10,867 --> 00:28:13,800 helps to support the metabolically active tissues 496 00:28:13,800 --> 00:28:16,730 within them by getting oxygen into an area 497 00:28:16,730 --> 00:28:19,390 where a wingless insect or other arthropod 498 00:28:19,390 --> 00:28:20,480 would not be able to. 499 00:28:22,250 --> 00:28:24,100 This full body ventilation 500 00:28:24,100 --> 00:28:27,960 could be the secret to Meganeuropsis's survival. 501 00:28:27,960 --> 00:28:31,110 The movement of its wings quickly brings air to the trachea 502 00:28:31,110 --> 00:28:34,210 which then supplies the organs with oxygen. 503 00:28:40,360 --> 00:28:43,250 While the ground dwelling giants of the Carboniferous period 504 00:28:43,250 --> 00:28:46,960 disappeared, this advantage would've allowed Meganeuras 505 00:28:46,960 --> 00:28:50,770 to continue ruling the skies during the Permian period, 506 00:28:50,770 --> 00:28:53,610 remaining at the top of the food chain in the swamps. 507 00:28:54,770 --> 00:28:58,050 This Diplocaulus, a now extinct amphibian, 508 00:28:58,050 --> 00:29:00,760 has no chance of going unnoticed, 509 00:29:00,760 --> 00:29:03,040 betrayed by its need for air. 510 00:29:04,020 --> 00:29:08,140 Meganeuropsis sees it as soon as it leaves the water surface 511 00:29:08,140 --> 00:29:11,360 thanks to eyes that are extremely sensitive to movement, 512 00:29:11,360 --> 00:29:12,520 shapes, and colors. 513 00:29:14,368 --> 00:29:17,368 (suspenseful music) 514 00:29:52,516 --> 00:29:54,810 Meganeuras were the super predators of the time, 515 00:29:54,810 --> 00:29:57,470 and their wings enabled them to survive 516 00:29:57,470 --> 00:30:00,090 despite falling levels of oxygen. 517 00:30:00,090 --> 00:30:02,360 So what caused their extinction? 518 00:30:03,370 --> 00:30:05,460 No Meganeura fossils have been discovered 519 00:30:05,460 --> 00:30:06,960 from after the Permian period. 520 00:30:07,810 --> 00:30:09,380 Today scientists still don't know 521 00:30:09,380 --> 00:30:11,440 exactly when they disappeared, 522 00:30:11,440 --> 00:30:13,995 but other large sized dragonflies survived 523 00:30:13,995 --> 00:30:17,310 the next 130 million years. 524 00:30:17,310 --> 00:30:19,584 To explain the extinction of these giants, 525 00:30:19,584 --> 00:30:21,810 scientists are now contemplating 526 00:30:21,810 --> 00:30:24,599 the emergence of new predators. 527 00:30:24,599 --> 00:30:27,920 While insects were the only flying creatures 528 00:30:27,920 --> 00:30:30,062 during the first part of their history, 529 00:30:30,062 --> 00:30:32,230 other animals took to the skies 530 00:30:32,230 --> 00:30:34,400 during the later Permian period, 531 00:30:34,400 --> 00:30:37,501 between 300 and 250 million years ago, 532 00:30:37,501 --> 00:30:40,770 of what was to become eventually Europe. 533 00:30:53,127 --> 00:30:55,255 Jean Sebastien Steyer, 534 00:30:55,255 --> 00:30:58,708 paleontologist at the Natural History Museum in Paris, 535 00:30:58,708 --> 00:31:02,089 is the leading French specialist in early vertebrates. 536 00:31:02,089 --> 00:31:05,738 He has come to the legendary paleontology gallery 537 00:31:05,738 --> 00:31:08,060 to collect a very important specimen 538 00:31:08,060 --> 00:31:10,180 for the study of insect predators. 539 00:31:11,030 --> 00:31:13,893 Though smaller in size than many other fossils, 540 00:31:13,893 --> 00:31:16,240 this was the first of its species 541 00:31:16,240 --> 00:31:18,990 to possess a major advantage. 542 00:31:27,871 --> 00:31:30,520 This is the fossil of a gliding reptile 543 00:31:30,520 --> 00:31:33,380 that is about 250 million years old 544 00:31:33,380 --> 00:31:36,000 and has the strange name of Coelurosauravus. 545 00:31:36,000 --> 00:31:38,850 This reptile actually developed gliding flight. 546 00:31:42,038 --> 00:31:43,550 The ability to glide allows an animal 547 00:31:43,550 --> 00:31:47,300 to catch prey in the air, like the giant insects. 548 00:31:52,910 --> 00:31:54,550 The planet continued to heat up 549 00:31:54,550 --> 00:31:56,950 at the end of the Permian period. 550 00:31:56,950 --> 00:32:00,310 Swamps, an infinite source of fossils, 551 00:32:00,310 --> 00:32:04,280 now had aquatic plants characteristic of stagnant waters. 552 00:32:06,830 --> 00:32:09,810 Like the insects during the Carboniferous period, 553 00:32:09,810 --> 00:32:11,660 reptiles were just starting to try out 554 00:32:11,660 --> 00:32:13,920 life in the trees and flying. 555 00:32:13,920 --> 00:32:17,090 Amongst them, Coelurosauravus would become 556 00:32:17,090 --> 00:32:19,240 an outstanding insect hunter 557 00:32:19,240 --> 00:32:20,860 thanks to its retractable wings. 558 00:32:25,536 --> 00:32:28,870 It had a very unusual and interesting anatomy. 559 00:32:28,870 --> 00:32:31,393 Its fairly small head was a triangular shape. 560 00:32:31,393 --> 00:32:35,610 On its skull, we can see small conical pointed teeth. 561 00:32:35,610 --> 00:32:38,610 They were probably used to crack the hard exoskeletons 562 00:32:38,610 --> 00:32:40,036 of insects. 563 00:32:40,036 --> 00:32:42,050 And of course, the main characteristic 564 00:32:42,050 --> 00:32:45,000 of this gliding reptile are its stick shaped bones 565 00:32:45,000 --> 00:32:48,170 that start around the armpits and enabled this animal 566 00:32:48,170 --> 00:32:51,360 to throw itself in the air and base jump. 567 00:32:51,360 --> 00:32:53,910 We can well imagine it climbing up this microscope, 568 00:32:53,910 --> 00:32:55,980 for instance, and then jumping. 569 00:32:58,480 --> 00:33:01,340 We can even imagine it climbing with its small claws 570 00:33:01,340 --> 00:33:03,330 and then unfolding its wings to glide. 571 00:33:04,840 --> 00:33:07,470 So we can picture the race between Coelurosauravus 572 00:33:07,470 --> 00:33:09,920 and the flying insects living at that time. 573 00:33:12,530 --> 00:33:15,140 Only 16 inches long, this small reptile 574 00:33:15,140 --> 00:33:17,152 couldn't catch Meganeuras. 575 00:33:17,152 --> 00:33:19,830 But it could compete for the same prey, 576 00:33:19,830 --> 00:33:20,990 the Palaeodictyoptera. 577 00:33:22,650 --> 00:33:25,870 To catch its victim, it has to take the plunge. 578 00:33:33,300 --> 00:33:36,410 Coelurosauravus can't flap its wings. 579 00:33:36,410 --> 00:33:38,700 To catch flying insects, 580 00:33:38,700 --> 00:33:41,720 it relies on an element of surprise. 581 00:33:49,190 --> 00:33:50,890 And its ability to glide. 582 00:33:56,468 --> 00:33:57,818 There is no room for error. 583 00:33:59,155 --> 00:34:02,155 (suspenseful music) 584 00:34:17,180 --> 00:34:20,220 Coelurosauravus is merely a first step 585 00:34:20,220 --> 00:34:21,340 on the road to flight. 586 00:34:26,040 --> 00:34:29,095 This gliding reptile has no doubt played a part. 587 00:34:29,095 --> 00:34:32,093 Maybe not in the full extension of giant insects, 588 00:34:32,093 --> 00:34:35,390 but in any case, we have a super predator 589 00:34:35,390 --> 00:34:38,280 regularly attacking them and we can therefore assume 590 00:34:38,280 --> 00:34:40,630 that this was one element in the decline 591 00:34:40,630 --> 00:34:42,180 of giant insects at the time. 592 00:34:44,280 --> 00:34:47,981 If Coelurosauravus was not the only culprit, 593 00:34:47,981 --> 00:34:52,420 it was certainly the first to put pressure on giant insects 594 00:34:52,420 --> 00:34:54,480 before any others took to the skies. 595 00:34:57,640 --> 00:34:59,560 This animal guarding the entrance 596 00:34:59,560 --> 00:35:01,922 to the Kassel Museum in Germany 597 00:35:01,922 --> 00:35:04,580 is part of the Pterosaur family. 598 00:35:05,490 --> 00:35:09,140 These flying reptiles appeared 230 million years ago. 599 00:35:10,312 --> 00:35:13,450 Today they are completely extinct, 600 00:35:13,450 --> 00:35:17,512 but scientists have discovered around 100 different species. 601 00:35:17,512 --> 00:35:21,810 Could they too have been a threat to the giant insects? 602 00:35:23,140 --> 00:35:27,230 Professor Eberhard Frey, or Dino as he's usually known, 603 00:35:27,230 --> 00:35:30,700 is a world specialist in Pterosaurs. 604 00:35:30,700 --> 00:35:33,300 Pterosaurs are flying reptiles, 605 00:35:33,300 --> 00:35:36,370 and they are characterized by flight membrane 606 00:35:36,370 --> 00:35:39,270 that extended from the tip of the little finger 607 00:35:39,270 --> 00:35:41,522 down to the ankle. 608 00:35:41,522 --> 00:35:44,100 Interesting point with these Pterosaurs 609 00:35:44,100 --> 00:35:48,220 is that they have a size range which is simply unbelievable 610 00:35:48,220 --> 00:35:51,140 from about 20 centimeters wingspan 611 00:35:51,140 --> 00:35:55,252 up to 14 meters wingspan, which is unique. 612 00:35:55,252 --> 00:35:57,770 Yet according to scientists, 613 00:35:57,770 --> 00:36:00,985 very few of these Pterosaurs were insect eaters. 614 00:36:00,985 --> 00:36:05,632 The only insectivores were part of the Anurognathids family, 615 00:36:05,632 --> 00:36:07,430 among the smallest Pterosaurs. 616 00:36:08,590 --> 00:36:12,834 We cannot imagine really that they hunted the big insects. 617 00:36:12,834 --> 00:36:15,430 But probably they chased the small ones, 618 00:36:15,430 --> 00:36:18,140 which are not seen in the fossil record. 619 00:36:18,140 --> 00:36:22,160 The big insects however also chased small insects, 620 00:36:22,160 --> 00:36:26,240 so they probably conquered about the same prey. 621 00:36:26,240 --> 00:36:29,280 All the other Pterosaurs from that time we know 622 00:36:29,280 --> 00:36:31,630 likely fed on something else, 623 00:36:31,630 --> 00:36:35,500 and thus did not make any concurrence to the big insects, 624 00:36:35,500 --> 00:36:37,540 and probably this is one of the reasons 625 00:36:37,540 --> 00:36:40,290 why they persisted such a long time. 626 00:36:44,260 --> 00:36:46,600 230 million years ago, 627 00:36:46,600 --> 00:36:48,600 during the Triassic period, 628 00:36:48,600 --> 00:36:50,930 Pterosaurs spread around Europe, 629 00:36:50,930 --> 00:36:54,670 but also to what is now South America and Asia. 630 00:36:56,240 --> 00:36:59,330 For the first time in the history of life on Earth, 631 00:36:59,330 --> 00:37:01,570 a family of vertebrates learned to master 632 00:37:01,570 --> 00:37:04,769 not just gliding, but flapping flight. 633 00:37:04,769 --> 00:37:08,360 Like Anurognathids discovered in Germany, 634 00:37:08,360 --> 00:37:13,360 its Asian cousin, Batrachognathus, is a flying reptile, 635 00:37:13,990 --> 00:37:18,150 nocturnal, insect eating, and fast. 636 00:37:19,830 --> 00:37:22,486 With its flat skull and big eyes, 637 00:37:22,486 --> 00:37:25,380 Batrachognathus occupied the same ecological niche 638 00:37:25,380 --> 00:37:26,890 as modern day owls. 639 00:37:27,889 --> 00:37:32,140 But the comparison with birds of prey stops there. 640 00:37:32,140 --> 00:37:36,137 Its enormous jaws are equipped with a dozen conical teeth. 641 00:37:36,137 --> 00:37:37,160 (screeching) 642 00:37:37,160 --> 00:37:41,230 No flying insect can hide from Batrachognathus Volans, 643 00:37:41,230 --> 00:37:43,580 literally flying frog jaw. 644 00:37:46,270 --> 00:37:49,549 Can the Caligramma, an insect with a 10 inch wingspan, 645 00:37:49,549 --> 00:37:50,850 take it on? 646 00:37:57,770 --> 00:37:59,750 An experiment carried out in Germany 647 00:37:59,750 --> 00:38:01,910 puts the theory to the test. 648 00:38:08,680 --> 00:38:10,610 Dino Frey works in collaboration 649 00:38:10,610 --> 00:38:12,570 with the Institute of Fluid Mechanics 650 00:38:12,570 --> 00:38:14,730 in Karlsruhe, Germany. 651 00:38:14,730 --> 00:38:16,630 This wind tunnel is usually used 652 00:38:16,630 --> 00:38:18,980 to refine the shape of airplanes 653 00:38:18,980 --> 00:38:21,100 and improve their aerodynamics. 654 00:38:21,100 --> 00:38:23,380 But today the paleontologist is using it 655 00:38:23,380 --> 00:38:26,010 to test the Pterosaur's flying abilities. 656 00:38:31,350 --> 00:38:34,690 A resin and carbon fiber model of Anurognathids 657 00:38:34,690 --> 00:38:36,140 is placed in the wind tunnel. 658 00:38:38,730 --> 00:38:40,500 We are at the beginning of our studies, 659 00:38:40,500 --> 00:38:43,220 but what we learned so far is that Pterosaurs 660 00:38:43,220 --> 00:38:46,090 likely were extremely slow fliers, 661 00:38:46,090 --> 00:38:48,109 so they could cope with wind speeds 662 00:38:48,109 --> 00:38:52,220 around 40 kilometers per hour or less, 663 00:38:52,220 --> 00:38:55,340 probably these guys needed to flap their wings 664 00:38:55,340 --> 00:38:59,600 to stay in the air, and they were not very good gliders. 665 00:38:59,600 --> 00:39:03,330 But flapping wings also means that they were 666 00:39:03,330 --> 00:39:06,096 as active fliers much more maneuverable, 667 00:39:06,096 --> 00:39:08,264 and this is again interesting when they started 668 00:39:08,264 --> 00:39:11,410 to chase insects on the wing. 669 00:39:14,529 --> 00:39:16,150 When Pterosaurs appeared, 670 00:39:16,150 --> 00:39:19,340 insects lost the monopoly on flapping flight. 671 00:39:21,538 --> 00:39:23,900 Batrachognathus was indeed capable 672 00:39:23,900 --> 00:39:25,350 of leaving the tree lined shore 673 00:39:25,350 --> 00:39:28,660 to chase insects out in the open, 674 00:39:28,660 --> 00:39:32,436 which his predecessor, Coelurosauravus the flying lizard, 675 00:39:32,436 --> 00:39:34,100 was unable to do. 676 00:39:35,600 --> 00:39:38,170 The Pterosaurs seem to have had more of an impact 677 00:39:38,170 --> 00:39:40,340 on the giant insects' prey 678 00:39:40,340 --> 00:39:42,820 than on the giant insects themselves, 679 00:39:42,820 --> 00:39:44,930 contributing to their final decline 680 00:39:44,930 --> 00:39:48,050 but not fully explaining their extinction. 681 00:39:49,122 --> 00:39:52,039 (mysterious music) 682 00:40:06,520 --> 00:40:08,550 On the other side of the Atlantic, 683 00:40:08,550 --> 00:40:11,610 one American researcher suggested other culprits 684 00:40:11,610 --> 00:40:14,880 in a study published in August 2012. 685 00:40:17,770 --> 00:40:21,170 This paleontologist specializes in the extinction 686 00:40:21,170 --> 00:40:23,550 that occurred at the end of the Permian period 687 00:40:24,567 --> 00:40:25,667 250 million years ago. 688 00:40:29,730 --> 00:40:31,480 More at home in front of a computer 689 00:40:31,480 --> 00:40:33,850 than wielding a trowel in the field, 690 00:40:33,850 --> 00:40:36,540 Matthew Clapham is a database devotee. 691 00:40:37,560 --> 00:40:39,410 It took him a year and a half to collect 692 00:40:39,410 --> 00:40:41,880 the information needed to publish his survey 693 00:40:41,880 --> 00:40:44,640 on the decline of giant insects. 694 00:40:44,640 --> 00:40:47,300 He has undertaken a mammoth task. 695 00:40:47,300 --> 00:40:49,709 Gathering the sizes of all fossil wings 696 00:40:49,709 --> 00:40:52,620 since the first scientific publications. 697 00:40:53,700 --> 00:40:56,560 We compiled this very large database 698 00:40:56,560 --> 00:40:59,944 with nearly 10,000 insect species 699 00:40:59,944 --> 00:41:03,330 by simply getting published papers 700 00:41:03,330 --> 00:41:06,720 where paleontologists had found insect fossils 701 00:41:06,720 --> 00:41:08,878 and described them and given them a name. 702 00:41:08,878 --> 00:41:10,640 Clapham discovered that during 703 00:41:10,640 --> 00:41:12,240 the first part of their history, 704 00:41:13,281 --> 00:41:14,796 insect size changed with the level 705 00:41:14,796 --> 00:41:15,910 of oxygen in the atmosphere. 706 00:41:15,910 --> 00:41:18,890 As oxygen declined, they diminished in size, 707 00:41:18,890 --> 00:41:21,610 and as it grows, their size increased. 708 00:41:21,610 --> 00:41:23,170 So this pattern holds for the first 709 00:41:23,170 --> 00:41:26,122 200 million years or so of insect history, 710 00:41:26,122 --> 00:41:29,640 but then beginning in the late part of the Jurassic period, 711 00:41:29,640 --> 00:41:32,410 around 150 million years ago, 712 00:41:32,410 --> 00:41:34,620 we can see insects become smaller, 713 00:41:34,620 --> 00:41:37,930 even though atmospheric oxygen is going up at this time. 714 00:41:37,930 --> 00:41:40,220 And this coincides quite closely with the evolution 715 00:41:40,220 --> 00:41:42,640 of Archaeopteryx, the first bird. 716 00:41:44,240 --> 00:41:46,144 The ancient ancestors of the birds 717 00:41:46,144 --> 00:41:48,990 first appeared during the Jurassic period 718 00:41:48,990 --> 00:41:51,170 160 million years ago. 719 00:41:51,170 --> 00:41:53,250 The oldest fossils come from China. 720 00:41:56,510 --> 00:41:59,650 At that time, forests of giant conifers 721 00:41:59,650 --> 00:42:03,040 offered a fantastic launchpad to conquer the sky. 722 00:42:05,600 --> 00:42:08,030 An ecological niche that was quickly seized 723 00:42:08,030 --> 00:42:11,240 by a new generation of creatures learning to fly. 724 00:42:12,290 --> 00:42:15,940 Small dinosaurs, like this Anchiornis, 725 00:42:15,940 --> 00:42:18,300 had feathers on their arms and legs, 726 00:42:18,300 --> 00:42:19,980 and used them as wings. 727 00:42:22,282 --> 00:42:25,439 (screeching) 728 00:42:25,439 --> 00:42:28,291 The claws on their wings enabled them to gain altitude 729 00:42:28,291 --> 00:42:30,190 and get good vantage points. 730 00:42:32,000 --> 00:42:35,280 Insects like this Jerusin Brophlibia 731 00:42:35,280 --> 00:42:38,109 had to hide in the trees to survive. 732 00:42:38,109 --> 00:42:41,149 As soon as it takes off, it become visible 733 00:42:41,149 --> 00:42:43,740 and is hunted down by Anchiornis. 734 00:42:44,800 --> 00:42:49,170 While only a few Pterosaurs like Anurognathids ate insects, 735 00:42:49,170 --> 00:42:52,310 all bird ancestors did. 736 00:42:52,310 --> 00:42:53,910 Increasingly skilled at flying, 737 00:42:53,910 --> 00:42:56,470 they would become fierce insect predators. 738 00:42:59,813 --> 00:43:01,420 In the Cretaceous period, 739 00:43:01,420 --> 00:43:03,670 when these first birds are evolving, 740 00:43:03,670 --> 00:43:05,960 there would've been increased predation pressure 741 00:43:05,960 --> 00:43:08,240 on these large insects in particular 742 00:43:08,240 --> 00:43:11,950 as they were less maneuverable than the smaller insects. 743 00:43:11,950 --> 00:43:14,080 In addition to this increased predation, 744 00:43:14,080 --> 00:43:17,950 there was likely competition between birds and insects, 745 00:43:17,950 --> 00:43:19,890 especially these large predatory insects, 746 00:43:19,890 --> 00:43:21,970 for the same food sources, 747 00:43:21,970 --> 00:43:24,447 and so both of those factors likely led to 748 00:43:24,447 --> 00:43:27,700 a decrease in insect size. 749 00:43:27,700 --> 00:43:30,860 This competition between birds and insects 750 00:43:30,860 --> 00:43:32,240 still happens today. 751 00:43:35,630 --> 00:43:38,283 Just like flying lizards and Pterosaurs, 752 00:43:38,283 --> 00:43:42,780 birds would've had an influence on the size of insects. 753 00:43:42,780 --> 00:43:45,880 But why have giant insects completely disappeared, 754 00:43:45,880 --> 00:43:48,930 leaving only today's small insect population? 755 00:43:50,140 --> 00:43:53,100 A last clue could provide an answer. 756 00:43:54,040 --> 00:43:55,950 It came from a fossil rich site 757 00:43:55,950 --> 00:43:59,200 close to where Anchiornis was found, 758 00:43:59,200 --> 00:44:04,110 in the Chinese region of Liaoning, northeast of Beijing. 759 00:44:05,450 --> 00:44:07,510 The numerous eruptions that shook the region 760 00:44:07,510 --> 00:44:11,327 125 million years ago have helped preserve certain plants 761 00:44:11,327 --> 00:44:14,360 from the period in volcanic ash, 762 00:44:14,360 --> 00:44:17,290 including the ancestors of flowering plants. 763 00:44:19,250 --> 00:44:23,657 Discovered in 2002 by the paleobotanist Sun Ge, 764 00:44:23,657 --> 00:44:26,130 they would've had an unexpected impact 765 00:44:26,130 --> 00:44:30,000 on the extinction of the last large sized dragonflies. 766 00:44:31,543 --> 00:44:36,543 And here in China, in the west valley, 767 00:44:37,060 --> 00:44:40,500 we found the oldest known (mumbles) 768 00:44:40,500 --> 00:44:42,550 called the Archaefructus. 769 00:44:45,410 --> 00:44:47,920 This is Archaefructus, 770 00:44:47,920 --> 00:44:50,810 the first flower to appear on our planet. 771 00:45:00,300 --> 00:45:03,090 On this fossil seen through a microscope 772 00:45:03,090 --> 00:45:05,120 we can distinguish the male organs, 773 00:45:05,120 --> 00:45:07,460 the stamens that contain the pollen 774 00:45:07,460 --> 00:45:09,840 and the piston, the female organ. 775 00:45:10,840 --> 00:45:13,560 These characteristics allow Sun Ge to confirm 776 00:45:13,560 --> 00:45:16,750 that this fossil belongs to the Angiosperm, 777 00:45:16,750 --> 00:45:20,419 a family of plants whose seeds are enclosed inside a fruit, 778 00:45:20,419 --> 00:45:21,990 unlike conifers. 779 00:45:23,430 --> 00:45:25,550 According to the paleobotanist, 780 00:45:25,550 --> 00:45:29,190 these plants were aquatic, and grew on lake shores. 781 00:45:30,140 --> 00:45:33,140 But what does the appearance of the first flowering plants 782 00:45:33,140 --> 00:45:37,000 have to do with the extinction of large carnivorous insects? 783 00:45:40,650 --> 00:45:44,310 Andre Nel believes these two events are linked. 784 00:45:45,720 --> 00:45:48,460 Many families of insects disappeared at that time, 785 00:45:48,460 --> 00:45:51,140 and others managed to adapt to angiosperms, 786 00:45:51,140 --> 00:45:53,640 which proliferated and began to diversify 787 00:45:53,640 --> 00:45:56,300 to produce more or less our modern forests. 788 00:45:56,300 --> 00:45:59,530 The impact was also very significant for dragonflies 789 00:45:59,530 --> 00:46:00,980 during that same period. 790 00:46:03,030 --> 00:46:05,120 Could the decline of giant insects 791 00:46:05,120 --> 00:46:09,110 have something to do with the dragonfly's original shape? 792 00:46:09,110 --> 00:46:11,956 Because before they were able to fly, 793 00:46:11,956 --> 00:46:13,960 they were aquatic creatures. 794 00:46:13,960 --> 00:46:16,510 Their life began underwater. 795 00:46:17,530 --> 00:46:21,330 For the first few years, they existed as larvae, 796 00:46:21,330 --> 00:46:23,490 and just like their cousins the mayflies, 797 00:46:23,490 --> 00:46:25,990 they fed on other aquatic insect larvae. 798 00:46:34,710 --> 00:46:37,620 When flouring planets such as Archaefructus 799 00:46:37,620 --> 00:46:41,752 appeared on the lake shores 125 million years ago, 800 00:46:41,752 --> 00:46:44,800 the larvae's life conditions changed. 801 00:46:47,380 --> 00:46:49,740 The plants took root in shallow waters, 802 00:46:49,740 --> 00:46:52,220 but then opened their flowers in the air. 803 00:46:54,470 --> 00:46:57,010 When they withered, their petals and leaves 804 00:46:57,010 --> 00:46:59,610 floated on the surface before sinking to the bottom. 805 00:47:02,070 --> 00:47:05,390 This material is digested by the microorganisms 806 00:47:05,390 --> 00:47:07,990 present in the water, but to do this, 807 00:47:07,990 --> 00:47:11,480 the organisms use the oxygen contained in the water, 808 00:47:11,480 --> 00:47:14,880 leaving little oxygen available for the dragonfly larvae. 809 00:47:15,940 --> 00:47:19,064 These dragonflies may have disappeared at that time 810 00:47:19,064 --> 00:47:21,770 because their larvae could not adapt 811 00:47:21,770 --> 00:47:24,876 to this change in the aquatic ecosystem, 812 00:47:24,876 --> 00:47:28,980 and they were replaced by other dragonflies. 813 00:47:28,980 --> 00:47:30,700 The emergence of flowering plants 814 00:47:30,700 --> 00:47:33,510 completely modified the lake's ecosystem, 815 00:47:34,420 --> 00:47:35,750 and would've led to the extinction 816 00:47:35,750 --> 00:47:37,940 of the last large sized insects 817 00:47:37,940 --> 00:47:41,400 which have gradually declined since the Carboniferous. 818 00:47:42,818 --> 00:47:45,818 (suspenseful music) 819 00:47:48,600 --> 00:47:51,430 The extinction of arthropods and giant insects 820 00:47:51,430 --> 00:47:53,310 over millions of years of evolution 821 00:47:53,310 --> 00:47:56,060 teaches us that it took many protagonists 822 00:47:56,060 --> 00:47:58,240 to cause the extinction of these species. 823 00:47:59,350 --> 00:48:02,840 A change in the composition of oxygen in the atmosphere, 824 00:48:02,840 --> 00:48:06,040 the emergence of new predators like flying lizards, 825 00:48:06,040 --> 00:48:09,230 some Pterosaurs, and the bird ancestors, 826 00:48:09,230 --> 00:48:12,680 and finally, the birth of flowers. 827 00:48:16,840 --> 00:48:18,927 In the early 21st century, 828 00:48:18,927 --> 00:48:22,150 which are the largest insects that inhabit our planet? 829 00:48:34,190 --> 00:48:38,650 Today, insects can reach the size of a hand, 830 00:48:38,650 --> 00:48:41,880 but very few are bigger than this Chinese cricket, 831 00:48:44,440 --> 00:48:47,550 for we are at the dawn of a new phase of extinction 832 00:48:48,990 --> 00:48:50,430 caused by humans, 833 00:48:51,710 --> 00:48:55,550 since the onset of the Industrial Revolution. 834 00:48:58,158 --> 00:48:59,001 (speaking foreign language) 835 00:48:59,001 --> 00:49:01,419 The large insects live mostly in tropical 836 00:49:01,419 --> 00:49:03,780 or intertropical climates. 837 00:49:04,820 --> 00:49:08,640 They are in danger since the habitat is at risk. 838 00:49:08,640 --> 00:49:11,550 If the forest in which the giant stick insect lives 839 00:49:11,550 --> 00:49:15,970 is in danger, the giant butterfly will of course disappear. 840 00:49:15,970 --> 00:49:18,490 I certainly hope that we will continue to see them, 841 00:49:18,490 --> 00:49:21,530 but certainly with the rate of habitat destruction 842 00:49:21,530 --> 00:49:22,840 that's going on throughout the world, 843 00:49:22,840 --> 00:49:24,810 particularly in the tropical environments 844 00:49:24,810 --> 00:49:26,854 where many of these species occur, 845 00:49:26,854 --> 00:49:30,221 it is very likely that a lot of them will be lost, 846 00:49:30,221 --> 00:49:32,440 just like the giant insects. 847 00:49:35,063 --> 00:49:37,980 (thunder rumbling) 848 00:49:52,250 --> 00:49:55,000 (dramatic music)