1 00:00:06,006 --> 00:00:08,008 [tense music playing] 2 00:00:09,968 --> 00:00:11,970 [distant roaring] 3 00:00:16,766 --> 00:00:20,395 [Morgan Freeman] In the four billion years of life on our planet, 4 00:00:21,354 --> 00:00:23,398 countless species have risen... 5 00:00:26,026 --> 00:00:27,193 and fallen. 6 00:00:28,486 --> 00:00:30,488 [distant roaring] 7 00:00:30,572 --> 00:00:35,785 But one remarkable dynasty has had a greater impact than any other. 8 00:00:41,082 --> 00:00:43,626 [roaring] 9 00:00:46,129 --> 00:00:47,630 The mammals. 10 00:00:50,300 --> 00:00:53,261 This is the story of their epic journey... 11 00:00:53,344 --> 00:00:55,346 [roaring] 12 00:00:56,973 --> 00:00:59,350 ...to become rulers of the world. 13 00:01:03,104 --> 00:01:05,106 [music fades] 14 00:01:05,774 --> 00:01:07,776 {\an8}[rousing music playing] 15 00:01:30,173 --> 00:01:32,592 [snarling] 16 00:01:32,675 --> 00:01:34,761 {\an8}[trilling] 17 00:01:36,596 --> 00:01:37,847 {\an8}[screeching] 18 00:01:42,977 --> 00:01:45,271 {\an8}[rousing music continues] 19 00:01:48,983 --> 00:01:50,944 [growling] 20 00:01:51,027 --> 00:01:52,946 [wind howling] 21 00:01:55,031 --> 00:01:56,783 {\an8}[rumbling] 22 00:01:58,785 --> 00:02:00,829 [rousing music intensifies] 23 00:02:00,912 --> 00:02:02,997 [music fades] 24 00:02:10,338 --> 00:02:12,340 {\an8}[insects chirping] 25 00:02:23,476 --> 00:02:26,187 Hidden in the ancient Jurassic forests... 26 00:02:28,314 --> 00:02:30,817 mammals came from humble beginnings... 27 00:02:33,528 --> 00:02:37,407 ruled over by the greatest dynasty that ever lived... 28 00:02:38,616 --> 00:02:40,368 [distant bellowing] 29 00:02:48,084 --> 00:02:49,377 ...the dinosaurs. 30 00:02:51,504 --> 00:02:53,256 [growls softly] 31 00:02:53,339 --> 00:02:55,216 They dominated so totally... 32 00:02:55,300 --> 00:02:56,342 [snorting] 33 00:02:57,468 --> 00:03:01,347 ...that early mammals were confined to the shadows. 34 00:03:04,184 --> 00:03:09,063 For the most part, they were small, keeping to the trees... 35 00:03:12,984 --> 00:03:14,819 away from the giants. 36 00:03:24,078 --> 00:03:25,580 They became nocturnal, 37 00:03:27,081 --> 00:03:31,127 developing a range of heightened senses that helped them in the dark. 38 00:03:35,131 --> 00:03:36,841 Under the dinosaurs' rule, 39 00:03:38,218 --> 00:03:41,095 there was a limit to how far they could rise. 40 00:03:44,015 --> 00:03:47,435 But in time, everything changed. 41 00:03:57,278 --> 00:04:00,406 One of the most violent events in our planet's history 42 00:04:01,616 --> 00:04:04,202 heralded a new era. 43 00:04:16,547 --> 00:04:18,549 [poignant music playing] 44 00:04:24,472 --> 00:04:26,140 Despite the devastation, 45 00:04:27,475 --> 00:04:29,686 the planet did recover. 46 00:04:36,442 --> 00:04:38,361 Within a few million years, 47 00:04:39,279 --> 00:04:42,615 forests had regrown and carpeted much of the land. 48 00:04:48,288 --> 00:04:50,873 The climate became hot and wet. 49 00:04:54,419 --> 00:04:58,381 The perfect conditions for life to flourish. 50 00:05:06,931 --> 00:05:10,935 A world primed for a new wave of evolution. 51 00:05:14,605 --> 00:05:17,108 - [insects chirping] - [birds squawking] 52 00:05:21,237 --> 00:05:25,116 The asteroid had inflicted devastating losses on the mammals... 53 00:05:28,619 --> 00:05:30,997 yet some of the smaller ones, 54 00:05:31,831 --> 00:05:35,626 able to hide in holes, had survived. 55 00:05:43,259 --> 00:05:45,345 [creature chattering] 56 00:05:47,638 --> 00:05:49,223 Free of the dinosaurs, 57 00:05:50,725 --> 00:05:53,353 they could finally venture out of the shadows 58 00:05:55,063 --> 00:05:56,647 and come into the open. 59 00:06:06,991 --> 00:06:09,660 - [birds chirping] - [chattering] 60 00:06:14,624 --> 00:06:16,125 Like their ancestors, 61 00:06:16,709 --> 00:06:19,087 coatis have many adaptations 62 00:06:19,170 --> 00:06:22,131 that help them thrive in the rich rainforest. 63 00:06:23,716 --> 00:06:27,762 Extremely social, they find safety in numbers. 64 00:06:33,226 --> 00:06:37,688 The mother's flexible nose can smell food hidden beneath the leaf litter. 65 00:06:39,357 --> 00:06:44,112 A supersense honed over millions of years of foraging in the darkness. 66 00:06:56,749 --> 00:07:00,420 Like all mammals, coatis are warm-blooded, 67 00:07:01,879 --> 00:07:04,090 so can be active at all times. 68 00:07:08,845 --> 00:07:12,390 That means these babies need plenty of energy. 69 00:07:16,727 --> 00:07:21,274 Fortunately, mammals have evolved an extraordinary solution. 70 00:07:24,402 --> 00:07:25,403 Milk. 71 00:07:25,486 --> 00:07:28,072 [suckling] 72 00:07:28,156 --> 00:07:30,908 They can feed their young whenever they choose, 73 00:07:32,410 --> 00:07:34,662 even when food is scarce. 74 00:07:38,833 --> 00:07:42,920 But milk wasn't the early mammals' only secret weapon. 75 00:07:49,010 --> 00:07:52,138 They also had brain power. 76 00:07:56,476 --> 00:07:59,103 [tapping] 77 00:07:59,645 --> 00:08:02,315 And it's still just as important today. 78 00:08:05,902 --> 00:08:08,821 In the forests of Costa Rica, 79 00:08:08,905 --> 00:08:11,782 this capuchin monkey is trying to solve a puzzle. 80 00:08:15,244 --> 00:08:19,123 How to get the meat from inside a closed clam. 81 00:08:21,542 --> 00:08:25,004 The monkey isn't strong enough to crack the shell... 82 00:08:25,087 --> 00:08:27,215 [tapping continues] 83 00:08:29,050 --> 00:08:33,763 but it's discovered that repeated hammering will tire the clam... 84 00:08:40,561 --> 00:08:42,271 until it finally opens. 85 00:08:45,483 --> 00:08:48,778 Learning this lesson takes a large brain... 86 00:08:49,529 --> 00:08:50,738 [clam thuds on ground] 87 00:08:50,821 --> 00:08:52,698 - ...and coordination. - [squeaks] 88 00:08:52,782 --> 00:08:55,284 [playful music playing] 89 00:09:00,706 --> 00:09:04,210 This unique intelligence allowed their primate ancestors 90 00:09:04,293 --> 00:09:08,256 to survive in the forest of 50 million years ago. 91 00:09:16,055 --> 00:09:19,350 Clever animals tend to be inquisitive... 92 00:09:22,603 --> 00:09:25,481 and that can pay huge dividends. 93 00:09:35,908 --> 00:09:37,827 This female has learned 94 00:09:38,911 --> 00:09:40,162 and remembered 95 00:09:41,998 --> 00:09:43,833 where she can find water. 96 00:09:47,712 --> 00:09:49,380 But it's too deep to reach. 97 00:09:50,673 --> 00:09:54,051 Luckily, she has an inspired solution. 98 00:09:58,014 --> 00:10:02,101 She turns her tail into a sponge. 99 00:10:10,735 --> 00:10:15,281 But not all their challenges are to do with finding food and water. 100 00:10:15,948 --> 00:10:17,033 [squeaks] 101 00:10:20,077 --> 00:10:24,332 Some fruit is collected not to eat... 102 00:10:27,209 --> 00:10:29,170 but to rub over their bodies. 103 00:10:34,216 --> 00:10:36,427 This fruit contains citronella, 104 00:10:37,637 --> 00:10:40,348 an oil that mosquitoes can't stand. 105 00:10:40,431 --> 00:10:43,017 [uplifting music playing] 106 00:10:46,145 --> 00:10:50,524 The monkeys have discovered their very own insect repellent. 107 00:11:03,287 --> 00:11:05,623 Free from pesky biting insects, 108 00:11:06,957 --> 00:11:10,461 the clever capuchins can finally relax. 109 00:11:11,212 --> 00:11:13,214 [music ends] 110 00:11:15,800 --> 00:11:19,095 But just as their ancestors were beginning to make progress, 111 00:11:20,554 --> 00:11:26,060 the warm, wet conditions in which they had thrived began to change. 112 00:11:41,242 --> 00:11:45,329 The Antarctic landmass started to split away from South America... 113 00:11:48,332 --> 00:11:51,794 creating the space for new ocean currents... 114 00:11:54,130 --> 00:11:56,424 that helped drive a global cooling. 115 00:12:00,761 --> 00:12:04,181 The climate was switching into a new, colder state. 116 00:12:05,266 --> 00:12:07,268 [poignant music playing] 117 00:12:08,686 --> 00:12:10,604 But that was just the beginning. 118 00:12:17,361 --> 00:12:20,906 As Antarctica became colder and more isolated, 119 00:12:21,699 --> 00:12:23,993 the huge continent froze, 120 00:12:25,494 --> 00:12:28,038 locking up much of the planet's fresh water. 121 00:12:35,838 --> 00:12:38,048 As the world further north dried out, 122 00:12:38,799 --> 00:12:42,428 it became a harsher, more difficult place to live. 123 00:12:47,141 --> 00:12:49,351 Food became more spread out, 124 00:12:50,352 --> 00:12:51,520 harder to find. 125 00:12:52,813 --> 00:12:54,690 And as the Earth changed, 126 00:12:55,941 --> 00:12:57,610 so did the mammals. 127 00:13:04,283 --> 00:13:05,409 [heavy footstep] 128 00:13:05,993 --> 00:13:07,995 [snorting] 129 00:13:08,496 --> 00:13:11,123 Some became enormous. 130 00:13:18,088 --> 00:13:20,132 A male Megacerops. 131 00:13:21,217 --> 00:13:22,635 [grunting] 132 00:13:24,053 --> 00:13:25,721 Two and a half meters tall... 133 00:13:25,805 --> 00:13:26,680 [grunting] 134 00:13:26,764 --> 00:13:28,140 ...four meters long... 135 00:13:31,602 --> 00:13:33,646 and three tons in weight. 136 00:13:35,606 --> 00:13:36,649 [snorting] 137 00:13:37,733 --> 00:13:38,901 [grunts] 138 00:13:38,984 --> 00:13:44,198 Its huge size allows it to travel large distances in search of food... 139 00:13:45,699 --> 00:13:46,867 [grunting] 140 00:13:46,951 --> 00:13:50,996 ...and ensures it has reserves to get through leaner times. 141 00:13:54,166 --> 00:13:56,669 [majestic music playing] 142 00:13:58,337 --> 00:14:04,009 Mammals were now big enough to rival the long-lost dinosaurs. 143 00:14:11,141 --> 00:14:14,937 But being big has other implications... 144 00:14:18,357 --> 00:14:23,112 especially when it comes to finding a mate. 145 00:14:25,364 --> 00:14:26,532 [snorting] 146 00:14:30,369 --> 00:14:33,163 [grunting] 147 00:14:36,000 --> 00:14:39,169 This female is already closely guarded by a male, 148 00:14:41,046 --> 00:14:42,673 much larger than the first. 149 00:14:43,257 --> 00:14:44,258 [snorts] 150 00:14:45,718 --> 00:14:46,718 [growling] 151 00:14:48,804 --> 00:14:50,306 If challenged, 152 00:14:51,098 --> 00:14:53,475 he could seriously injure his opponent. 153 00:14:57,313 --> 00:14:59,189 [roaring] 154 00:15:01,400 --> 00:15:02,443 [snorts] 155 00:15:03,569 --> 00:15:04,862 [grunting] 156 00:15:10,743 --> 00:15:14,330 But the smaller male may be in luck. 157 00:15:18,167 --> 00:15:19,710 Another female, 158 00:15:21,503 --> 00:15:24,089 and she seems to be alone. 159 00:15:27,176 --> 00:15:28,177 [grunts] 160 00:15:32,389 --> 00:15:34,642 It's the chance he's been waiting for. 161 00:15:35,351 --> 00:15:36,977 [grunting] 162 00:15:38,270 --> 00:15:39,980 [growling] 163 00:15:41,857 --> 00:15:43,067 He has a rival. 164 00:15:43,150 --> 00:15:44,151 [roaring] 165 00:15:46,820 --> 00:15:49,823 This time, they're evenly matched. 166 00:15:51,575 --> 00:15:53,243 [grunting, growling] 167 00:15:54,495 --> 00:15:56,497 [tense music playing] 168 00:15:58,582 --> 00:15:59,792 [bellows] 169 00:16:00,376 --> 00:16:02,002 [grunting] 170 00:16:02,670 --> 00:16:03,712 [bellows] 171 00:16:04,880 --> 00:16:05,880 [roars] 172 00:16:08,592 --> 00:16:10,302 - [bellowing] - [growling] 173 00:16:13,389 --> 00:16:15,724 [roaring, growling] 174 00:16:19,269 --> 00:16:21,480 [growling] 175 00:16:30,823 --> 00:16:32,157 [grunting] 176 00:16:36,787 --> 00:16:37,955 With these mammals... 177 00:16:38,038 --> 00:16:39,999 [growls] 178 00:16:40,082 --> 00:16:41,750 ...size matters. 179 00:16:46,088 --> 00:16:48,465 But even the mightiest Megacerops 180 00:16:49,925 --> 00:16:53,679 couldn't overcome the planet's next great challenge. 181 00:17:06,275 --> 00:17:11,321 The formation of Antarctica was creating global climate chaos. 182 00:17:13,699 --> 00:17:15,576 As ocean currents shifted 183 00:17:16,744 --> 00:17:18,412 and the planet dried... 184 00:17:21,081 --> 00:17:23,667 it became a tinderbox. 185 00:17:23,751 --> 00:17:25,753 [mournful music playing] 186 00:17:36,805 --> 00:17:40,309 Wildfires ravaged the land... 187 00:17:43,103 --> 00:17:46,398 clearing the way for something completely different... 188 00:17:53,030 --> 00:17:56,784 something that would challenge mammals as never before. 189 00:18:02,122 --> 00:18:04,249 As the smoke cleared, 190 00:18:04,333 --> 00:18:06,210 there rose from the ashes 191 00:18:06,293 --> 00:18:12,716 a life-form that had previously only survived in the margins. 192 00:18:21,892 --> 00:18:23,102 Grass. 193 00:18:30,984 --> 00:18:33,987 Taking root during the great drying... 194 00:18:36,198 --> 00:18:37,825 it spread so quickly, 195 00:18:39,326 --> 00:18:41,954 it would soon cover one-fifth of the land. 196 00:18:51,964 --> 00:18:56,385 But the endless plains were no paradise for the mammals. 197 00:19:00,556 --> 00:19:02,766 Many couldn't digest grass 198 00:19:04,351 --> 00:19:06,770 and soon went extinct. 199 00:19:11,191 --> 00:19:13,443 [insects chirping] 200 00:19:13,527 --> 00:19:14,611 [snorts] 201 00:19:16,405 --> 00:19:18,073 Twenty million years later, 202 00:19:19,158 --> 00:19:23,704 and today's grazing mammals remain locked in an arms race 203 00:19:24,288 --> 00:19:25,873 with this green invader. 204 00:19:29,960 --> 00:19:36,633 They have evolved a whole swathe of game-changing adaptations. 205 00:19:38,802 --> 00:19:40,596 Specialized teeth, 206 00:19:41,221 --> 00:19:44,183 strengthened to prevent silica in the grass 207 00:19:45,267 --> 00:19:46,602 from wearing them out... 208 00:19:50,814 --> 00:19:54,276 and huge bellies to process it all. 209 00:20:00,616 --> 00:20:03,076 Their young are born fully formed... 210 00:20:03,160 --> 00:20:04,328 [snorting] 211 00:20:06,038 --> 00:20:08,415 ...able to walk within hours of birth... 212 00:20:14,713 --> 00:20:17,633 and follow their herd in search of fresh growth. 213 00:20:21,803 --> 00:20:25,432 Mammals have truly conquered the grassy plains... 214 00:20:30,479 --> 00:20:35,567 their huge numbers the most obvious sign of this exceptional success. 215 00:20:41,865 --> 00:20:44,993 But just as some mammals evolved to feed on the grass, 216 00:20:46,453 --> 00:20:49,957 others evolved to feed on the grazers. 217 00:20:54,044 --> 00:20:55,170 Hunters. 218 00:20:57,422 --> 00:20:59,424 [herd lowing] 219 00:21:05,430 --> 00:21:09,601 The herd has its own defense against the cheetahs' blistering speed. 220 00:21:15,899 --> 00:21:18,110 - Many eyes... - [snorting, grunting] 221 00:21:18,193 --> 00:21:19,569 ...spot the danger early. 222 00:21:19,653 --> 00:21:22,406 - [herd grunting] - [bird squawking] 223 00:21:22,489 --> 00:21:25,242 [tense music playing] 224 00:21:30,664 --> 00:21:32,332 [grunting] 225 00:21:32,416 --> 00:21:37,045 Running bodies create confusion for the young to hide in. 226 00:21:39,631 --> 00:21:41,466 But the big cat has a plan... 227 00:21:43,552 --> 00:21:46,346 forged by its clever mammalian brain. 228 00:21:50,976 --> 00:21:52,060 Panic the herd, 229 00:21:52,728 --> 00:21:53,937 split them up, 230 00:21:55,355 --> 00:21:57,232 and target a lone calf. 231 00:22:07,075 --> 00:22:09,077 [tense, energetic music playing] 232 00:22:22,341 --> 00:22:24,468 Desperate to defend her only calf, 233 00:22:25,635 --> 00:22:27,679 the female wildebeest counters. 234 00:22:34,061 --> 00:22:36,521 The chase is far from over. 235 00:22:41,401 --> 00:22:43,612 The cheetah has lost a lot of ground... 236 00:22:46,323 --> 00:22:49,076 but the calf is tiring. 237 00:22:49,159 --> 00:22:51,661 [tense, energetic music continues] 238 00:23:02,881 --> 00:23:04,508 [music slows] 239 00:23:04,591 --> 00:23:06,718 As the youngster turns, 240 00:23:07,302 --> 00:23:09,971 it's the hunter who must now run for its life. 241 00:23:15,852 --> 00:23:17,979 [herd lowing] 242 00:23:19,564 --> 00:23:21,733 The calf is safe once more... 243 00:23:21,817 --> 00:23:24,486 [calm music playing] 244 00:23:27,364 --> 00:23:29,825 ...but the cheetah will be back... 245 00:23:38,208 --> 00:23:42,879 and the war between the grassland mammals will continue 246 00:23:42,963 --> 00:23:45,966 as it has done for millions of years. 247 00:23:47,092 --> 00:23:49,261 [tranquil music playing] 248 00:24:08,947 --> 00:24:11,074 In prehistoric South America, 249 00:24:12,075 --> 00:24:15,078 the grasslands played host to the same battle... 250 00:24:17,956 --> 00:24:19,916 but with very different animals. 251 00:24:20,709 --> 00:24:22,711 [intriguing music playing] 252 00:24:32,262 --> 00:24:33,889 This giant armadillo... 253 00:24:36,475 --> 00:24:38,185 is also a mammal... 254 00:24:40,520 --> 00:24:43,064 though one the size of a car. 255 00:24:45,567 --> 00:24:48,195 Doedicurus may not be fast, 256 00:24:49,821 --> 00:24:51,406 but what they lack in speed... 257 00:24:51,490 --> 00:24:52,782 [trilling] 258 00:24:52,866 --> 00:24:57,412 ...they make up for with armor and a lethal tail... 259 00:25:03,293 --> 00:25:04,878 [grunts softly, snorts] 260 00:25:04,961 --> 00:25:09,132 ...adaptations that protect them and their young 261 00:25:09,216 --> 00:25:11,468 from any would-be predators. 262 00:25:11,551 --> 00:25:13,386 [trilling] 263 00:25:17,682 --> 00:25:19,684 [ominous music playing] 264 00:25:25,190 --> 00:25:27,442 [soft growling] 265 00:25:29,444 --> 00:25:30,487 A Smilodon... 266 00:25:33,615 --> 00:25:35,116 but a mere youngster. 267 00:25:37,702 --> 00:25:39,162 - [soft growling] - [snorting] 268 00:25:39,246 --> 00:25:41,206 [whimsical music playing] 269 00:25:43,333 --> 00:25:44,543 [trilling] 270 00:25:44,626 --> 00:25:46,211 He's not a serious threat... 271 00:25:46,294 --> 00:25:47,587 [trilling] 272 00:25:47,671 --> 00:25:50,048 [hissing, growling] 273 00:25:50,131 --> 00:25:52,342 ...even with his dagger-like teeth. 274 00:25:56,805 --> 00:25:59,182 He's never seen a Doedicurus up close, 275 00:26:00,058 --> 00:26:03,395 and their defenses are intriguing. 276 00:26:04,896 --> 00:26:06,189 [hissing] 277 00:26:12,529 --> 00:26:14,030 [soft growling] 278 00:26:15,824 --> 00:26:18,201 His curiosity gets the better of him. 279 00:26:18,285 --> 00:26:20,453 [trilling] 280 00:26:20,537 --> 00:26:21,830 [purring] 281 00:26:24,291 --> 00:26:26,126 [trilling] 282 00:26:26,209 --> 00:26:27,794 - [grunts] - [hisses] 283 00:26:28,712 --> 00:26:31,256 [whimsical music continues] 284 00:26:31,339 --> 00:26:33,508 [trilling] 285 00:26:33,592 --> 00:26:35,969 He explores every angle. 286 00:26:38,221 --> 00:26:40,223 [snorting] 287 00:26:42,058 --> 00:26:43,685 [trilling] 288 00:26:50,483 --> 00:26:53,987 For the young Doedicurus, the only option is to stay put. 289 00:26:54,070 --> 00:26:55,780 [trilling] 290 00:27:01,286 --> 00:27:04,497 The giant armadillos' armor is completely impregnable... 291 00:27:05,749 --> 00:27:07,417 [growls softly] 292 00:27:07,500 --> 00:27:08,668 ...and they know it. 293 00:27:11,796 --> 00:27:13,590 - [trilling] - [growling] 294 00:27:18,845 --> 00:27:20,347 [growling] 295 00:27:22,766 --> 00:27:25,602 But there is one obvious opportunity. 296 00:27:26,645 --> 00:27:28,605 [trilling] 297 00:27:28,688 --> 00:27:30,231 [growls] 298 00:27:31,566 --> 00:27:35,028 The young Doedicurus is so much smaller. 299 00:27:37,697 --> 00:27:39,324 If he can get a hold on it... 300 00:27:39,407 --> 00:27:41,409 - [growling] - [trilling] 301 00:27:41,493 --> 00:27:43,870 ...he might be able to turn it over. 302 00:27:43,953 --> 00:27:44,996 [hissing] 303 00:27:47,791 --> 00:27:49,376 [trilling] 304 00:27:49,459 --> 00:27:51,544 But not with the adults around. 305 00:27:54,756 --> 00:27:56,341 [low growling] 306 00:27:57,550 --> 00:28:00,011 - Another stalemate. - [juvenile moans] 307 00:28:01,012 --> 00:28:03,014 - [trilling] - [snarling] 308 00:28:08,645 --> 00:28:12,399 Battles between the mammals have always driven their evolution, 309 00:28:13,566 --> 00:28:16,695 and they don't just happen in the grasslands. 310 00:28:16,778 --> 00:28:19,280 [wind whistling] 311 00:28:19,364 --> 00:28:20,907 Fifty million years ago, 312 00:28:21,700 --> 00:28:26,371 what are now India and Asia collided on an epic scale. 313 00:28:28,915 --> 00:28:31,710 The crash forced the land into the sky, 314 00:28:32,460 --> 00:28:35,213 creating the towering Himalayas. 315 00:28:35,880 --> 00:28:38,383 [majestic music playing] 316 00:28:42,804 --> 00:28:46,307 Today, they are 2,500 kilometers long, 317 00:28:47,183 --> 00:28:49,227 almost nine kilometers high, 318 00:28:50,562 --> 00:28:51,938 and still growing. 319 00:28:55,024 --> 00:28:57,694 With their freezing temperatures and thin air, 320 00:28:58,486 --> 00:29:02,240 these mountains are uninhabitable for most animals. 321 00:29:02,323 --> 00:29:04,993 [unsettling music playing] 322 00:29:07,454 --> 00:29:08,788 But not all. 323 00:29:15,712 --> 00:29:17,422 Deep in a sunless valley... 324 00:29:23,178 --> 00:29:24,679 a male snow leopard... 325 00:29:30,685 --> 00:29:33,813 and an ibex that has fallen to its death. 326 00:29:44,991 --> 00:29:47,243 The leopard is very old, 327 00:29:48,578 --> 00:29:51,539 worn and tattered by his harsh mountain life. 328 00:29:56,711 --> 00:30:01,591 At these altitudes, mammals must feed regularly to keep warm. 329 00:30:05,470 --> 00:30:08,765 But the Himalayas present the ultimate hunting challenge. 330 00:30:14,437 --> 00:30:17,565 High above the valley, a female... 331 00:30:22,821 --> 00:30:26,491 and her cubs, fathered by the male. 332 00:30:28,576 --> 00:30:29,953 Three of them in total, 333 00:30:30,829 --> 00:30:33,665 all amazingly camouflaged. 334 00:30:40,338 --> 00:30:42,966 Snow leopards have thick fur, 335 00:30:44,050 --> 00:30:45,593 large paws, 336 00:30:46,678 --> 00:30:47,929 and long tails... 337 00:30:52,600 --> 00:30:56,479 perfect adaptations for the coldest, 338 00:30:57,146 --> 00:31:00,692 most precipitous nursery on Earth. 339 00:31:00,775 --> 00:31:02,777 [stirring music playing] 340 00:31:18,751 --> 00:31:20,503 [music fades] 341 00:31:23,590 --> 00:31:25,508 Away from the dangerous cliffs... 342 00:31:27,343 --> 00:31:29,345 [light, playful music playing] 343 00:31:29,429 --> 00:31:31,764 ...the mother initiates a hunting lesson. 344 00:31:31,848 --> 00:31:32,932 [soft growling] 345 00:31:36,394 --> 00:31:37,645 [growling] 346 00:31:44,152 --> 00:31:47,113 Teaching and caring for one's young 347 00:31:48,781 --> 00:31:50,909 is a key mammalian trait. 348 00:32:05,465 --> 00:32:08,968 These cubs will stay with their mother for nearly two years... 349 00:32:15,016 --> 00:32:19,979 learning the skills needed to survive on the very edge of life. 350 00:32:20,980 --> 00:32:22,774 [music ends] 351 00:32:25,818 --> 00:32:29,948 At these altitudes, every opportunity must be taken. 352 00:32:34,911 --> 00:32:37,997 The old male is tracking a herd. 353 00:32:44,879 --> 00:32:49,550 In this vertical world, he must get above his prey... 354 00:32:49,634 --> 00:32:51,636 [tense music playing] 355 00:33:02,689 --> 00:33:04,315 ...and close enough... 356 00:33:05,984 --> 00:33:07,485 for an ambush. 357 00:33:14,701 --> 00:33:16,703 [tense music continues] 358 00:33:46,733 --> 00:33:48,276 [loose rocks tinkle] 359 00:33:50,361 --> 00:33:52,113 [rocks clattering] 360 00:33:53,906 --> 00:33:56,325 [water splashing] 361 00:34:03,541 --> 00:34:04,541 [snorts] 362 00:34:10,840 --> 00:34:12,175 This time 363 00:34:13,176 --> 00:34:15,178 death has claimed them both. 364 00:34:20,349 --> 00:34:22,351 [poignant music playing] 365 00:34:30,943 --> 00:34:34,322 But the leopard's legacy lives on. 366 00:34:38,951 --> 00:34:40,536 In a few months' time, 367 00:34:41,788 --> 00:34:46,000 his cubs will leave their mother and start to hunt alone, 368 00:34:47,960 --> 00:34:50,713 having learned all the skills they need 369 00:34:52,465 --> 00:34:55,176 to survive at the top of the world. 370 00:35:12,985 --> 00:35:15,488 Although they had conquered the land, 371 00:35:16,823 --> 00:35:18,783 the mammals didn't stop there. 372 00:35:18,866 --> 00:35:20,868 [insects chirping] 373 00:35:24,205 --> 00:35:29,544 One branched out and went in an entirely different direction. 374 00:35:38,511 --> 00:35:43,766 Fifty million years ago, bats opened up a whole new realm... 375 00:35:47,562 --> 00:35:49,272 through flight. 376 00:35:53,484 --> 00:35:55,486 [gentle music playing] 377 00:36:16,966 --> 00:36:20,261 Flying allows animals to search much further for food... 378 00:36:23,723 --> 00:36:26,767 and gather in their millions. 379 00:36:39,155 --> 00:36:44,243 Today, one in five of all mammal species is a bat. 380 00:36:44,327 --> 00:36:46,329 [high-pitched squeaking] 381 00:36:50,124 --> 00:36:54,295 But bats were not the first animals to take to the skies. 382 00:36:59,425 --> 00:37:01,636 Having spent the night foraging, 383 00:37:01,719 --> 00:37:05,223 these fruit bats are in a race to return to the roost... 384 00:37:05,306 --> 00:37:07,308 [high-pitched squeaking] 385 00:37:10,311 --> 00:37:13,648 ...for with daylight comes danger. 386 00:37:15,024 --> 00:37:17,193 [tense music playing] 387 00:37:17,276 --> 00:37:18,319 Birds. 388 00:37:18,861 --> 00:37:20,863 [high-pitched squeaking] 389 00:37:26,869 --> 00:37:30,581 They evolved flight long before the mammals. 390 00:37:41,968 --> 00:37:43,970 [tense music intensifies] 391 00:37:50,810 --> 00:37:53,437 Faster and stronger than bats... 392 00:38:01,070 --> 00:38:03,781 eagles are armed with deadly talons. 393 00:38:05,491 --> 00:38:07,493 [squeaking] 394 00:38:07,576 --> 00:38:10,162 [music fades] 395 00:38:10,246 --> 00:38:12,039 [high-pitched squeaking] 396 00:38:12,123 --> 00:38:13,958 But as dusk falls, 397 00:38:16,085 --> 00:38:19,964 the skies belong to the bats once more. 398 00:38:20,047 --> 00:38:22,550 [serene music playing] 399 00:38:22,633 --> 00:38:24,385 Millions take to the wing, 400 00:38:25,011 --> 00:38:28,639 knowing that safety lies in numbers 401 00:38:29,557 --> 00:38:32,393 and in the coming darkness. 402 00:38:47,825 --> 00:38:51,579 At the same time as bats were first moving into the air, 403 00:38:52,288 --> 00:38:55,833 other mammals were moving into the sea... 404 00:38:59,754 --> 00:39:03,966 {\an8}...attracted by the abundance of food hidden beneath the waves. 405 00:39:17,980 --> 00:39:22,568 The mammals' journey into the oceans was a gradual one. 406 00:39:22,651 --> 00:39:24,653 [lowing] 407 00:39:27,865 --> 00:39:29,950 These are Maiacetus, 408 00:39:30,868 --> 00:39:34,997 two-and-a-half-meter-long ancestors of the whales. 409 00:39:38,292 --> 00:39:40,086 [lowing] 410 00:39:40,169 --> 00:39:45,883 But unlike whales, they still spend much of their time lazing on land. 411 00:39:45,966 --> 00:39:47,968 [peaceful music playing] 412 00:39:51,806 --> 00:39:55,267 It's in the water that they come alive... 413 00:39:57,812 --> 00:39:59,605 chasing schools of fish. 414 00:40:12,410 --> 00:40:16,205 His time down here is limited by how long he can hold his breath. 415 00:40:26,841 --> 00:40:29,552 He seems caught between two worlds, 416 00:40:31,220 --> 00:40:33,264 especially when facing danger. 417 00:40:33,347 --> 00:40:35,349 [ominous music playing] 418 00:40:49,488 --> 00:40:53,242 The mammal's intelligence is his only defense... 419 00:40:56,787 --> 00:40:58,873 but he can't stay down here forever. 420 00:40:58,956 --> 00:41:00,958 [ominous music continues] 421 00:41:02,418 --> 00:41:03,669 Otodus. 422 00:41:04,587 --> 00:41:07,339 Twice the length of a great white shark. 423 00:41:09,175 --> 00:41:13,971 With finely-tuned senses, it can pinpoint his exact location, 424 00:41:15,514 --> 00:41:17,975 and it's in no hurry to make its move. 425 00:41:21,312 --> 00:41:23,856 The Maiacetus is running out of air. 426 00:41:23,939 --> 00:41:25,941 [tense, hurried music playing] 427 00:41:34,116 --> 00:41:37,119 In open water, there's no escape. 428 00:41:39,914 --> 00:41:42,082 An overhang offers refuge. 429 00:41:49,548 --> 00:41:51,926 But time is running out. 430 00:41:56,180 --> 00:41:58,182 [music intensifies] 431 00:42:05,940 --> 00:42:07,816 A gully provides cover. 432 00:42:13,572 --> 00:42:15,574 [music fades] 433 00:42:15,658 --> 00:42:17,493 [grunting] 434 00:42:17,576 --> 00:42:18,577 Safe 435 00:42:19,787 --> 00:42:22,081 and able to breathe once more. 436 00:42:22,164 --> 00:42:24,166 [lowing] 437 00:42:25,000 --> 00:42:26,043 [grunting] 438 00:42:30,339 --> 00:42:35,177 Mammals had a long way to go to become masters of the world's oceans, 439 00:42:38,597 --> 00:42:40,766 but it was only a matter of time. 440 00:42:52,319 --> 00:42:54,405 As the planet continued to cool, 441 00:42:55,281 --> 00:42:57,366 it fed an explosion of life... 442 00:43:05,666 --> 00:43:09,587 allowing the giants of today to evolve. 443 00:43:17,052 --> 00:43:19,054 [rousing music playing] 444 00:43:30,065 --> 00:43:33,277 The mammals had gone from tiny land animals... 445 00:43:35,446 --> 00:43:38,449 to being bigger than dinosaurs. 446 00:43:58,385 --> 00:44:00,095 With each giant breath, 447 00:44:00,679 --> 00:44:05,267 they use oxygen far more effectively than Maiacetus. 448 00:44:07,102 --> 00:44:08,896 And being warm-blooded, 449 00:44:08,979 --> 00:44:13,609 their muscles are always at a temperature for maximum performance... 450 00:44:17,571 --> 00:44:22,785 ...allowing the whales to generate sustained bursts of energy. 451 00:44:24,078 --> 00:44:26,705 [dark, pulsing music playing] 452 00:44:34,505 --> 00:44:36,215 When competing for a mate, 453 00:44:36,924 --> 00:44:39,843 humpback males exploit this ability to the full... 454 00:44:45,265 --> 00:44:47,101 pursuing a single female. 455 00:44:53,816 --> 00:44:56,193 This is much more than about speed. 456 00:45:01,490 --> 00:45:05,035 The males stay as close to the female as possible 457 00:45:05,119 --> 00:45:08,539 so she can judge their strength and stamina. 458 00:45:14,712 --> 00:45:16,714 [dark, pulsing music continues] 459 00:45:28,726 --> 00:45:33,021 Bubble streaming intimidates rivals. 460 00:45:36,775 --> 00:45:39,111 The males plow into each other. 461 00:45:49,955 --> 00:45:51,415 Some get left behind, 462 00:45:52,875 --> 00:45:53,917 still fighting. 463 00:45:54,001 --> 00:45:56,712 [dramatic music playing] 464 00:46:08,015 --> 00:46:10,893 The main group keeps up the chase... 465 00:46:13,270 --> 00:46:15,647 hot on the tail of the female. 466 00:46:26,533 --> 00:46:27,701 [music ends abruptly] 467 00:46:31,497 --> 00:46:32,998 Then suddenly, 468 00:46:33,957 --> 00:46:35,375 she stops. 469 00:46:41,215 --> 00:46:43,217 [peaceful music playing] 470 00:46:46,011 --> 00:46:47,596 Hanging in the water... 471 00:46:50,599 --> 00:46:52,518 she has called off the race. 472 00:47:01,318 --> 00:47:03,320 She has made her decision... 473 00:47:11,161 --> 00:47:12,996 and allows one male... 474 00:47:16,291 --> 00:47:17,626 to approach. 475 00:47:24,383 --> 00:47:27,886 The mammals have conquered every habitat on Earth. 476 00:47:32,307 --> 00:47:35,602 Land, air, and sea. 477 00:47:41,567 --> 00:47:46,321 The asteroid strike had allowed the mammals to go from lowly underdogs... 478 00:47:49,575 --> 00:47:51,535 to become a global power. 479 00:47:53,954 --> 00:48:00,586 Such is the role of chance in the history of life on our planet. 480 00:48:05,799 --> 00:48:07,801 [music fades] 481 00:48:09,928 --> 00:48:15,601 But there is one more chapter in the mammal story still to be told. 482 00:48:20,564 --> 00:48:22,482 Two and a half million years ago, 483 00:48:23,817 --> 00:48:26,612 the mammals were faced with a new challenge. 484 00:48:27,863 --> 00:48:29,323 [wind howling] 485 00:48:29,406 --> 00:48:31,408 [poignant music playing] 486 00:48:37,205 --> 00:48:41,960 What had been a slow cooling of the planet intensified. 487 00:48:49,009 --> 00:48:51,845 The start of an ice age. 488 00:48:55,641 --> 00:48:59,311 From its frozen wastes would come a new force... 489 00:49:01,146 --> 00:49:07,402 a mammal armed with more intelligence and adaptability than any before. 490 00:49:10,238 --> 00:49:14,076 The most dangerous animal the world had ever seen. 491 00:49:14,159 --> 00:49:16,161 [sinister music playing] 492 00:49:19,331 --> 00:49:20,749 [music ends] 493 00:49:21,917 --> 00:49:24,503 [rousing music playing]