1 00:00:01,601 --> 00:00:04,001 After millions of years of evolution, 2 00:00:04,204 --> 00:00:06,695 our distant ancestors have filled the oceans 3 00:00:06,906 --> 00:00:08,931 and crawled out onto land. 4 00:00:13,113 --> 00:00:16,173 They have survived the giant insects of the swamps 5 00:00:16,383 --> 00:00:20,479 and mushroomed into massive reptiles, armed to the teeth. 6 00:00:27,260 --> 00:00:29,353 But now the war they've waged so long 7 00:00:29,562 --> 00:00:32,963 is much more than a battle between predator and prey. 8 00:00:33,233 --> 00:00:36,430 The whole planet is entering a different kind of crisis, 9 00:00:36,669 --> 00:00:39,467 one that will destroy most of these monster reptiles 10 00:00:39,672 --> 00:00:43,073 and wipe out 90 per cent of life on earth. 11 00:01:13,506 --> 00:01:16,942 All the continents on earth have now drifted together 12 00:01:17,143 --> 00:01:20,977 to create on giant land mass called Pangaea. 13 00:01:21,347 --> 00:01:26,046 And at its centre lies the largest desert the world has ever seen. 14 00:01:26,352 --> 00:01:30,721 It's a brutal world where animals have to be especially tough. 15 00:01:31,724 --> 00:01:33,749 Perfect for reptiles. 16 00:01:37,597 --> 00:01:40,930 This is a one-ton Siberian Scutosaurus, 17 00:01:41,134 --> 00:01:43,398 a distant ancestor of turtles. 18 00:01:43,603 --> 00:01:47,903 Although he has no shell, his back is covered in hard, bony plates. 19 00:01:48,108 --> 00:01:53,444 And just as well: these sand dunes hide a fearsome predator. 20 00:01:54,481 --> 00:01:57,177 Scutosaurus normally travel in herds. 21 00:01:57,383 --> 00:02:02,844 But this old male's got left behind, and his keen nose senses danger. 22 00:02:18,838 --> 00:02:21,398 Once he tires, he's vulnerable. 23 00:02:41,060 --> 00:02:44,257 His attacker is a carnivorous Gorgonopsid. 24 00:02:50,603 --> 00:02:53,333 She's fast, powerful, and equipped 25 00:02:53,540 --> 00:02:56,304 with deadly weapons no hunter has had before. 26 00:03:04,217 --> 00:03:07,618 Exhausted, trapped and weakened by his wound, 27 00:03:07,820 --> 00:03:10,345 the old Scutosaurus has no fight left. 28 00:03:12,158 --> 00:03:15,457 All he can do is wait for the killer blow. 29 00:03:36,182 --> 00:03:41,518 The Gorgonopsid's huge jaws hold a pair of fangs 12 centimetres long. 30 00:03:41,921 --> 00:03:45,220 She has evolved the world's first sabre teeth - 31 00:03:45,491 --> 00:03:49,086 a lethal weapon some mammal predators will later use. 32 00:04:00,707 --> 00:04:02,538 In this harsh landscape, 33 00:04:02,742 --> 00:04:06,109 the reptile's biggest battle is now with the elements. 34 00:04:06,446 --> 00:04:11,941 A massive surge in volcanic activity is beginning to superheat the atmosphere, 35 00:04:12,151 --> 00:04:16,850 creating the highest temperature life on earth has ever known. 36 00:04:19,325 --> 00:04:21,350 Each year the deserts spread. 37 00:04:21,561 --> 00:04:25,019 Even here in Siberia, far north of the equator, 38 00:04:25,231 --> 00:04:29,429 animals are forced to cluster around any lasting source of water, 39 00:04:29,636 --> 00:04:31,467 no matter how small. 40 00:04:38,011 --> 00:04:43,643 The huge female Gorgonopsid has come looking for a drink to wash down the Scutosaurus, 41 00:04:44,083 --> 00:04:47,951 and even smaller Gorgonopsids will do well to keep out of her way. 42 00:04:48,788 --> 00:04:51,256 Five metres long from nose to tail, 43 00:04:51,457 --> 00:04:53,925 she's the top predator on earth. 44 00:04:54,127 --> 00:04:55,822 There'll be nothing to rival her 45 00:04:56,029 --> 00:05:00,125 until the dinosaurs evolve in 30 million years' time. 46 00:05:02,835 --> 00:05:04,393 But unlike the dinosaurs, 47 00:05:04,604 --> 00:05:08,335 these early reptiles are more closely linked to our ancestors, 48 00:05:08,541 --> 00:05:11,533 mammals, than to lizards and crocodiles. 49 00:05:12,211 --> 00:05:13,542 They don't have fur, 50 00:05:13,746 --> 00:05:16,874 but they've already evolved scent glands in their skin. 51 00:05:17,116 --> 00:05:21,143 This way, everyone can tell when the giant Gorgonopsid is around. 52 00:05:28,795 --> 00:05:30,854 Despite the presence of these heavyweights, 53 00:05:31,064 --> 00:05:34,830 smaller creatures also eke out a living around the waterhole. 54 00:05:36,369 --> 00:05:41,033 Diictodon, a hardly little burrower, just half a metre long. 55 00:05:44,877 --> 00:05:50,338 They live as pairs in spiral burrows which remain cool even in the desert heat. 56 00:05:50,550 --> 00:05:52,381 Like the large predators outside, 57 00:05:52,585 --> 00:05:55,952 Diictodon are distant reptile relatives of mammals, 58 00:05:56,155 --> 00:06:00,285 and although it will be 30 million years before the first true mammals appear, 59 00:06:00,493 --> 00:06:03,360 there are already family resemblances. 60 00:06:04,330 --> 00:06:08,460 In particular, his hearing is linked to tiny bones in his lower jaw. 61 00:06:08,835 --> 00:06:12,100 One day these will evolve into our middle ear bones, 62 00:06:12,305 --> 00:06:14,330 something no reptile has. 63 00:06:20,213 --> 00:06:23,148 Several pairs of Diictodon live around the waterhole, 64 00:06:23,349 --> 00:06:24,782 but this is not a colony, 65 00:06:24,984 --> 00:06:29,045 they compete furiously for the sparse vegetation that is their food. 66 00:06:29,322 --> 00:06:32,052 This frequently leads to confrontation. 67 00:06:39,365 --> 00:06:40,889 These clashes are one reason 68 00:06:41,100 --> 00:06:45,230 why both males and females sport a pair of short tusks. 69 00:06:56,416 --> 00:07:00,352 There is, however, one big advantage to living in a crowd: 70 00:07:00,653 --> 00:07:04,817 if a neighbour spots danger, everyone soon knows about it. 71 00:07:07,226 --> 00:07:09,990 A Gorgonopsid has come to investigate. 72 00:07:22,175 --> 00:07:26,578 A single snap of those enormous jaws would crush Diictodon - 73 00:07:26,813 --> 00:07:28,747 if they could get a grip. 74 00:07:31,250 --> 00:07:33,810 But it's not always size that counts. 75 00:07:43,396 --> 00:07:46,661 These tiny mouthfuls are more trouble than they're worth. 76 00:07:48,401 --> 00:07:52,064 The Gorgonopsid knows that if she hangs around the waterhole for long enough, 77 00:07:52,271 --> 00:07:55,365 eventually larger prey will come to her. 78 00:08:08,588 --> 00:08:12,354 There is another, unseen, resident of this waterhole. 79 00:08:14,360 --> 00:08:18,558 A monster much less suited than the reptiles to the changing climate. 80 00:08:19,398 --> 00:08:24,028 A fugitive from when this desert world was lush and green. 81 00:08:25,037 --> 00:08:28,473 It lies in ambush underwater, like a crocodile. 82 00:08:35,314 --> 00:08:38,181 A giant amphibian Labyrinthodont. 83 00:08:40,086 --> 00:08:43,920 But pound for pound, this female's picked the wrong target. 84 00:08:49,662 --> 00:08:54,429 The amphibian's ambush attempt was probably driven by sheer desperation. 85 00:08:54,700 --> 00:08:58,534 For generations this waterhole has supported a wide range of animals, 86 00:08:58,738 --> 00:09:01,468 including several other Labyrinthodonts. 87 00:09:01,741 --> 00:09:03,402 But this one is the last, 88 00:09:03,609 --> 00:09:07,670 and as the water she depends on disappears, she's trapped. 89 00:09:19,358 --> 00:09:22,418 The wet season arrives, but there's no rain. 90 00:09:22,995 --> 00:09:24,394 With life under such pressure, 91 00:09:24,597 --> 00:09:26,497 species are dying out at a rate 92 00:09:26,699 --> 00:09:31,159 that won't be matched until humans evolve in 250 million years' time. 93 00:09:33,072 --> 00:09:36,769 The waterhole is now no more than a large puddle. 94 00:09:41,981 --> 00:09:44,472 Diictodon are more adaptable than most. 95 00:09:44,717 --> 00:09:46,947 They can dig deeper to escape the heat, 96 00:09:47,153 --> 00:09:49,883 carving out tunnels in the rock-hard mud. 97 00:09:55,094 --> 00:09:57,790 But the giant amphibian is in big trouble, 98 00:09:57,997 --> 00:10:02,229 and as she grows weaker, her enemy watches and waits. 99 00:10:02,635 --> 00:10:05,570 It's a deadly game of cat and mouse. 100 00:10:13,279 --> 00:10:16,305 But life here is about to change for everyone. 101 00:10:37,103 --> 00:10:41,506 A migrating herd of Scutosaurus has sniffed out the waterhole. 102 00:10:50,616 --> 00:10:53,813 It's possible the smelt the water several miles away, 103 00:10:54,020 --> 00:10:57,854 and this could well be the first drink they've had in six months. 104 00:11:04,730 --> 00:11:07,699 The desert plants are a poor source of nutrients, 105 00:11:07,900 --> 00:11:11,961 but these large reptiles are designed to squeeze out every ounce, 106 00:11:12,204 --> 00:11:14,172 although they cannot chew. 107 00:11:15,441 --> 00:11:19,275 Their huge stomachs hold stones they've picked up from the desert. 108 00:11:19,612 --> 00:11:24,481 These help grind the vegetation so their digestive juices can get to work. 109 00:11:35,561 --> 00:11:39,019 The tough little Diictodons are used to dodging danger. 110 00:11:40,566 --> 00:11:43,501 But the Gorgonopsid now keeps her distance. 111 00:11:44,336 --> 00:11:48,466 Even she dare not attack such a large armoured herd. 112 00:11:56,849 --> 00:11:58,510 It's a standoff. 113 00:12:05,858 --> 00:12:08,986 It turns out the Scutosaurus are a bigger threat to life 114 00:12:09,195 --> 00:12:11,959 around the waterhole than the predators. 115 00:12:12,364 --> 00:12:14,924 Within a few days they have drunk it dry. 116 00:12:17,903 --> 00:12:21,999 And moved on once again in their eternal search for food. 117 00:12:31,951 --> 00:12:36,513 They represent the plight of all creatures on the continent of Pangaea. 118 00:12:37,156 --> 00:12:41,889 The global drought is now obliterating millions of years of evolution. 119 00:12:42,461 --> 00:12:45,589 Life everywhere is on the brink. 120 00:12:59,178 --> 00:13:01,544 For animals that do not migrate, 121 00:13:01,747 --> 00:13:04,409 the situation's reaching a crisis point. 122 00:13:11,123 --> 00:13:14,650 Hunger drives the Gorgonopsid back to the Diictodon - 123 00:13:14,860 --> 00:13:17,727 and this time she tries to dig them out. 124 00:13:27,106 --> 00:13:29,768 But the Diictodon's hard work pays off. 125 00:13:30,176 --> 00:13:34,579 Their tunnel in the sun-baked earth is deep enough to keep them safe. 126 00:13:37,383 --> 00:13:42,252 Instead, the Gorgonopsid's nose leads her back to the dried-up waterhole. 127 00:13:42,655 --> 00:13:46,091 She senses things are not as lifeless as they seem. 128 00:14:02,141 --> 00:14:03,870 The giant amphibian. 129 00:14:04,076 --> 00:14:06,306 Just before the waterhole dried up, 130 00:14:06,512 --> 00:14:08,707 she must have burrowed into the damp mud, 131 00:14:08,914 --> 00:14:11,109 forming a cocoon around herself, 132 00:14:11,317 --> 00:14:14,878 in a last-ditch attempt to sit out the drought. 133 00:14:17,156 --> 00:14:18,487 But in her torpid state, 134 00:14:18,691 --> 00:14:22,354 she's helpless as the Gorgonopsid feasts. 135 00:14:43,883 --> 00:14:46,443 Eventually storm clouds gather, 136 00:14:46,685 --> 00:14:49,813 but instead of rainwater they bring sand. 137 00:14:59,732 --> 00:15:01,597 The sandstorm sweeps in, 138 00:15:01,800 --> 00:15:04,428 burying the waterhole completely. 139 00:15:28,160 --> 00:15:31,220 The vast Pangaean deserts continue to spread, 140 00:15:31,497 --> 00:15:34,159 snuffing out entire ecosystems. 141 00:15:34,633 --> 00:15:38,069 Even the mighty Gorgonopsid has at last succumbed. 142 00:15:38,337 --> 00:15:41,704 With no prey, even she could not survive. 143 00:15:42,508 --> 00:15:44,100 Mummified in the sand, 144 00:15:44,310 --> 00:15:47,438 this monster will soon be nothing but dust. 145 00:15:51,583 --> 00:15:53,414 Over the next few million years, 146 00:15:53,619 --> 00:15:57,521 the earth will suffocate under a stagnant blanket of heat, 147 00:15:57,823 --> 00:15:59,484 sparking a mass extinction, 148 00:15:59,692 --> 00:16:03,128 even greater than the one that will destroy the dinosaurs. 149 00:16:03,829 --> 00:16:06,957 The future belongs to a tiny group of survivors, 150 00:16:07,166 --> 00:16:10,294 small and adaptable enough to sit it out. 151 00:16:11,103 --> 00:16:14,197 The Diictodon carry on digging throughout the drought. 152 00:16:14,573 --> 00:16:16,939 This pair has unearthed plant tubers, 153 00:16:17,142 --> 00:16:21,670 which hold enough water and nutrients to keep them going for several months. 154 00:16:30,255 --> 00:16:32,189 As millions of years go by, 155 00:16:32,391 --> 00:16:34,325 the climate shifts again, 156 00:16:34,526 --> 00:16:39,361 and the reptiles are among the first to recover and repopulate the empty earth. 157 00:16:40,065 --> 00:16:45,503 From creatures like little Diictodon, larger, stronger herbivores evolve. 158 00:16:46,538 --> 00:16:51,840 These tough forerunners of mammals seem poised to seize control for good, 159 00:16:52,344 --> 00:16:56,371 but they are in fact set to play out their final scene. 160 00:17:11,063 --> 00:17:13,395 The dawn of the Triassic era, 161 00:17:13,599 --> 00:17:17,296 and the earth has only just begun to show signs of recovery. 162 00:17:17,870 --> 00:17:19,360 The deserts have stopped growing, 163 00:17:19,571 --> 00:17:24,599 and huge forests of primitive conifer start to re-colonise the land. 164 00:17:28,714 --> 00:17:32,650 In these new forests, plant eaters recover first. 165 00:17:32,985 --> 00:17:36,318 One in particular. Like most of the large reptiles, 166 00:17:36,522 --> 00:17:38,387 they may resemble dinosaurs, 167 00:17:38,590 --> 00:17:43,550 but Lystrosaurus are more closely linked to mammals - and to us. 168 00:17:43,962 --> 00:17:49,161 Astonishingly, their vast herds make up more than half of all life on earth. 169 00:17:49,568 --> 00:17:53,436 Never again will a single species do so well. 170 00:17:57,910 --> 00:18:01,778 Deep within the forests, though, a rival is evolving. 171 00:18:01,980 --> 00:18:06,974 A new type of animal, destined to change the face of life on earth. 172 00:18:13,492 --> 00:18:17,360 Meet Euparkeria, a tiny insect-eater. 173 00:18:17,663 --> 00:18:20,530 He may not look much of a threat to the dominant reptiles, 174 00:18:20,732 --> 00:18:23,895 but the key to his success is in his hip. 175 00:18:25,671 --> 00:18:27,730 The way his thigh bone is attached 176 00:18:27,940 --> 00:18:31,671 allows him to run on two legs, freeing his hands. 177 00:18:38,784 --> 00:18:42,481 This kind of agility has never been seen before in reptiles, 178 00:18:42,688 --> 00:18:45,316 and gives Euparkeria an edge. 179 00:18:58,537 --> 00:19:04,169 Euparkeria will lay the foundations for a new group of reptiles - the dinosaurs. 180 00:19:07,813 --> 00:19:11,340 Giants such as Tyrannosaurus and Diplodocus can all trace 181 00:19:11,550 --> 00:19:16,613 their family tree back to this little insect hunter in the Triassic forests. 182 00:19:26,198 --> 00:19:30,862 The monster herds of Lystrosaurus hoover up so much vegetation 183 00:19:31,069 --> 00:19:34,368 that they constantly migrate to find fresh food. 184 00:19:34,940 --> 00:19:37,101 They follow the seasonal rains, 185 00:19:37,309 --> 00:19:42,611 and each year in Antarctica this brings them to the edge of a huge escarpment. 186 00:19:46,051 --> 00:19:50,954 The only way down for these cumbersome animals is through a deep ravine. 187 00:20:13,979 --> 00:20:17,346 The herd moves mostly at night, and come sunset, 188 00:20:17,549 --> 00:20:20,143 they begin the dangerous descent. 189 00:20:21,553 --> 00:20:25,717 It will take several hours for all of them to pass through the ravine, 190 00:20:25,924 --> 00:20:29,325 and in some parts there's only space to move in single file, 191 00:20:30,028 --> 00:20:32,428 which leaves them very vulnerable. 192 00:20:46,445 --> 00:20:50,711 Lystrosaurus have sharp eyesight and a very good sense of smell. 193 00:20:51,149 --> 00:20:55,643 But in these cramped conditions it's hard to spot trouble ahead. 194 00:21:01,660 --> 00:21:07,360 They're being watched by a vicious nocturnal hunter - a therocephalian. 195 00:21:11,036 --> 00:21:13,504 Lystrosaurus are strong opponents, 196 00:21:13,705 --> 00:21:17,072 but this hunter doesn't rely on power to make a kill. 197 00:21:27,286 --> 00:21:31,382 The attack is swift, and seems to have been unsuccessful. 198 00:21:31,757 --> 00:21:35,124 But this predator's secret weapon is a poisonous bite. 199 00:21:35,427 --> 00:21:37,987 Its venom is more lethal than a black mamba's, 200 00:21:38,196 --> 00:21:41,393 and it quickly floods the Lystrosaurus's blood stream. 201 00:21:42,801 --> 00:21:47,204 All the therocephalians have to do is wait for it to take effect. 202 00:21:51,443 --> 00:21:55,106 The victim collapses, but the herd moves on without concern. 203 00:21:55,380 --> 00:21:57,439 They have no social bonds. 204 00:22:07,459 --> 00:22:10,360 The therocephalians close in for the kill. 205 00:22:23,842 --> 00:22:26,106 Dawn at the foot of the escarpment, 206 00:22:26,311 --> 00:22:30,179 and here the Lystrosaurus will face their biggest challenge yet. 207 00:22:30,415 --> 00:22:35,250 They need to cross a river, but its banks are lined with open jaws. 208 00:22:38,490 --> 00:22:42,790 Chasmatosaurs are the earliest ancestors of crocodiles and alligators. 209 00:22:42,994 --> 00:22:46,555 Their strange overbite means once they get their teeth into a victim, 210 00:22:46,765 --> 00:22:48,960 there is no chance of escape. 211 00:22:49,201 --> 00:22:51,192 They don't normally gather in such numbers, 212 00:22:51,403 --> 00:22:57,239 but they're here for a special event - the annual migration of the Lystrosaurus. 213 00:22:59,211 --> 00:23:03,580 If you're a Euparkeria, the river's not a great place for hunting insects. 214 00:23:04,082 --> 00:23:06,141 But he has speed on his side. 215 00:23:18,263 --> 00:23:22,597 As the sun rises, the Chasmatosaurs are drawn towards the water. 216 00:23:23,001 --> 00:23:24,161 Some of them haven't eaten 217 00:23:24,369 --> 00:23:27,770 since the Lystrosaurus last passed this way a year ago. 218 00:23:27,973 --> 00:23:30,806 Now they sense it's time to feed again. 219 00:23:42,654 --> 00:23:46,886 The front of the vast Lystrosaurus herd finally reaches the river. 220 00:23:53,298 --> 00:23:57,496 They're strong swimmers, but drowning is not the danger here. 221 00:24:03,241 --> 00:24:06,768 They linger at the river's edge, reluctant to go in. 222 00:24:07,546 --> 00:24:10,481 For reptiles, they have relatively large brains, 223 00:24:10,682 --> 00:24:13,150 and they remember what happened last year. 224 00:24:14,152 --> 00:24:17,087 But with more Lystrosaurus arriving all the time, 225 00:24:17,322 --> 00:24:19,790 the backlog will soon force them in. 226 00:24:28,066 --> 00:24:31,263 On the other side, lush grazing beckons, 227 00:24:31,603 --> 00:24:34,868 and eventually the first one takes the plunge. 228 00:24:44,382 --> 00:24:47,613 A strong swimmer, he quickly makes it to the other side. 229 00:24:47,886 --> 00:24:48,750 But with the steep banks, 230 00:24:48,954 --> 00:24:51,548 he's still got to find a place where he can get ashore, 231 00:24:51,790 --> 00:24:55,226 and every extra moment in the water increases the risk. 232 00:25:05,370 --> 00:25:09,272 More and more Lystrosaurus warily strike out for the other side. 233 00:25:14,246 --> 00:25:16,771 But now the predators are homing in. 234 00:25:35,400 --> 00:25:39,029 The first swimmer has made it, and clambers ashore. 235 00:25:39,237 --> 00:25:43,264 But many of the herd now entering the water will not be so lucky. 236 00:26:44,202 --> 00:26:45,396 Despite the carnage, 237 00:26:45,604 --> 00:26:48,300 the herd is soon reforming on the other side. 238 00:26:56,247 --> 00:26:59,182 The predators are quickly sated and exhausted. 239 00:27:00,585 --> 00:27:02,519 Although many Lystrosaurus are dead, 240 00:27:02,721 --> 00:27:05,918 it's still only a small proportion of the herd. 241 00:27:09,728 --> 00:27:13,994 The dominance of these strange mammal-like reptiles is short-lived. 242 00:27:14,199 --> 00:27:16,861 As the plant recovers, so does competition, 243 00:27:17,068 --> 00:27:20,936 and the brief glory days of Lystrosaurus will soon be gone. 244 00:27:28,480 --> 00:27:32,211 This is followed by a decline in all mammal-like reptiles, 245 00:27:32,417 --> 00:27:36,649 consigning our ancestors to the shadows for millions of years. 246 00:27:40,859 --> 00:27:46,855 Instead, it is creatures like Euparkeria that are about to usher in a new golden age. 247 00:27:48,566 --> 00:27:52,195 These specialists on two legs will provide a cornerstone for 248 00:27:52,404 --> 00:27:55,840 one of the greatest dynasties the world will ever see. 249 00:27:58,076 --> 00:28:01,239 Their descendants will become the dominant life form on earth 250 00:28:01,446 --> 00:28:04,313 for more than 170 million years, 251 00:28:04,949 --> 00:28:08,885 and be known as the most notorious monsters of them all. 252 00:28:18,897 --> 00:28:22,355 Welcome to the Age of Dinosaurs.