1 00:00:06,600 --> 00:00:08,600 [thunder crashing] 2 00:00:11,720 --> 00:00:12,960 [rainfall] 3 00:00:13,040 --> 00:00:13,920 [dog barking] 4 00:00:14,000 --> 00:00:15,400 [birds calling] 5 00:00:16,960 --> 00:00:18,960 [varied bird calls] 6 00:00:22,520 --> 00:00:24,520 [wings fluttering] 7 00:00:25,560 --> 00:00:30,000 [narrator] The Earth, home to millions of species. 8 00:00:30,080 --> 00:00:31,280 [man talking on radio] 9 00:00:31,360 --> 00:00:33,640 [woman singing] 10 00:00:34,640 --> 00:00:37,880 But what might live... beyond? 11 00:00:45,160 --> 00:00:48,480 There are countless planets  throughout the universe. 12 00:00:53,920 --> 00:00:57,360 If life exists on only a fraction of them, 13 00:00:58,520 --> 00:01:03,200 then the universe must be... alive. 14 00:01:03,960 --> 00:01:05,960 [cawing] 15 00:01:10,000 --> 00:01:12,000 [chattering] 16 00:01:12,960 --> 00:01:16,640 All living things have the same needs. 17 00:01:19,440 --> 00:01:20,640 To feed... 18 00:01:27,320 --> 00:01:28,600 reproduce... 19 00:01:33,280 --> 00:01:34,120 and evolve. 20 00:01:38,120 --> 00:01:40,760 By applying the laws of life on Earth 21 00:01:41,320 --> 00:01:43,080 to the rest of the universe... 22 00:01:45,120 --> 00:01:46,920 it's possible to imagine 23 00:01:47,400 --> 00:01:48,880 what could live... 24 00:01:50,320 --> 00:01:52,480 on alien worlds. 25 00:02:15,720 --> 00:02:19,040 All life forms need a planet to live on. 26 00:02:20,640 --> 00:02:23,760 But how many planets  are there in the universe? 27 00:02:28,920 --> 00:02:30,480 [man] Think about our star, 28 00:02:31,440 --> 00:02:32,400 the Sun, 29 00:02:33,360 --> 00:02:36,760 with Earth, Mars, Jupiter orbiting it. 30 00:02:41,520 --> 00:02:42,880 For centuries, 31 00:02:42,960 --> 00:02:46,040 people have asked themselves, "What about the other stars? 32 00:02:46,120 --> 00:02:48,200 Uh, do they have planets as well?" 33 00:02:52,120 --> 00:02:53,760 And 24 years ago, 34 00:02:54,600 --> 00:02:55,920 I found one! 35 00:03:02,880 --> 00:03:06,440 Didier Queloz is a superstar astrophysicist. 36 00:03:09,120 --> 00:03:12,840 He has won the Nobel Prize  for discovering the first planet 37 00:03:12,920 --> 00:03:14,880 beyond our solar system. 38 00:03:18,520 --> 00:03:21,480 [Didier] I was 28 years old when I found the planet. 39 00:03:22,240 --> 00:03:24,560 I was about to finish my PhD, 40 00:03:24,640 --> 00:03:28,080 and my PhD adviser gave me the key of the equipment. 41 00:03:28,680 --> 00:03:32,400 And after observing a couple of times, the star 51 Peg, 42 00:03:32,480 --> 00:03:35,080 I realized that something was going on on that star.  43 00:03:36,720 --> 00:03:39,120 And frankly, I just panicked at that time. 44 00:03:40,120 --> 00:03:42,840 I thought something was really wrong with my equipment. 45 00:03:44,120 --> 00:03:48,120 And the more I wanted to understand this, the less it made sense. 46 00:03:49,640 --> 00:03:53,040 Until the point I got convinced it must be a planet. 47 00:03:58,480 --> 00:04:00,240 That's likely to be a planet over there. 48 00:04:02,440 --> 00:04:03,920 Could be Jupiter over there. 49 00:04:04,480 --> 00:04:05,720 It's pretty cool. 50 00:04:12,040 --> 00:04:15,280 Distant planets are invisible  to telescopes 51 00:04:15,920 --> 00:04:17,960 because they don't emit any light. 52 00:04:21,120 --> 00:04:23,800 But if a planet passes in front of a star, 53 00:04:24,760 --> 00:04:26,880 it casts a tiny shadow, 54 00:04:27,520 --> 00:04:30,680 and there's a minuscule dimming  of the star's brightness. 55 00:04:32,920 --> 00:04:35,960 When astronomers detect this dip in light level, 56 00:04:36,040 --> 00:04:38,400 they have found a new planet. 57 00:04:41,920 --> 00:04:43,040 Hello, guys. 58 00:04:43,960 --> 00:04:46,200 Uh... Oh, hey. Here is what the telescope is looking at. 59 00:04:46,280 --> 00:04:48,200 This is a picture  of the telescope right now. 60 00:04:49,240 --> 00:04:52,640 Uh, in the middle, you have the... the target we're observing. 61 00:04:52,720 --> 00:04:56,680 So, you analyze this whole field, you process the data, 62 00:04:56,760 --> 00:05:00,480 and, um, if you're lucky enough, you detect this. 63 00:05:00,560 --> 00:05:03,200 There's a little bit of a decrease  of the flux, 64 00:05:03,280 --> 00:05:06,560 and this tells me  that there is a planet orbiting that star. 65 00:05:10,960 --> 00:05:14,560 [Didier] We know there are a huge number  of planets in the universe. 66 00:05:17,720 --> 00:05:21,400 There must be a zillion kinds of different life. 67 00:05:22,240 --> 00:05:25,400 Let's imagine  that this is the Earth, here... 68 00:05:27,080 --> 00:05:28,040 Right? 69 00:05:28,120 --> 00:05:33,760 So, imagine that one meter  is 20 light-years. 70 00:05:33,840 --> 00:05:37,040 So, I've made two meters as 40 light-years. 71 00:05:37,120 --> 00:05:42,200 This is where you have 51 Peg, where the first planet was detected. 72 00:05:44,000 --> 00:05:46,920 Each of these tiny lights  represents a star 73 00:05:47,000 --> 00:05:48,840 where a planet has been found. 74 00:05:51,320 --> 00:05:53,000 Over the next few years, 75 00:05:53,440 --> 00:05:55,680 planets were turning up everywhere. 76 00:05:57,400 --> 00:05:59,640 ♪ Planets, planets everywhere ♪ 77 00:06:03,360 --> 00:06:05,760 It looks pretty cool right now. [laughs] 78 00:06:06,240 --> 00:06:08,480 A horizon of stars and planets... 79 00:06:09,320 --> 00:06:11,000 all around. [laughs] 80 00:06:16,920 --> 00:06:21,560 Planets beyond our solar system are called exoplanets. 81 00:06:26,520 --> 00:06:29,920 Astronomers have found  over 4,000 of them. 82 00:06:31,120 --> 00:06:32,880 And they keep finding more. 83 00:06:41,280 --> 00:06:46,480 They now believe there's at least  one planet for every star in the universe. 84 00:06:48,920 --> 00:06:55,280 That means over  a million, billion, trillion exoplanets. 85 00:07:00,040 --> 00:07:03,600 More than all  the grains of sand on Earth. 86 00:07:05,840 --> 00:07:10,440 A vast canvas for the evolution of life. 87 00:07:18,160 --> 00:07:20,760 The distances are mind-boggling. 88 00:07:22,720 --> 00:07:26,560 The nearest exoplanets  are trillions of miles from us. 89 00:07:29,720 --> 00:07:34,640 But they're all subject to the same force that holds the Earth in place. 90 00:07:37,200 --> 00:07:38,200 Gravity. 91 00:07:46,160 --> 00:07:49,520 Imagine a world double the size of Earth, 92 00:07:50,440 --> 00:07:52,280 with twice as much gravity. 93 00:07:56,040 --> 00:07:58,360 This is Atlas. 94 00:08:03,160 --> 00:08:06,360 How would life adapt on such a world? 95 00:08:14,480 --> 00:08:16,480 [alien bird trilling] 96 00:08:17,920 --> 00:08:21,520 Gravity pulls vegetation  to the planet's surface. 97 00:08:24,120 --> 00:08:27,520 And yet, seeds can float in the sky. 98 00:08:29,520 --> 00:08:32,600 That's because gravity here is so strong. 99 00:08:33,120 --> 00:08:36,080 Air molecules are densely packed together... 100 00:08:38,280 --> 00:08:42,840 creating a thick, buoyant atmosphere  for seeds to drift through. 101 00:08:53,520 --> 00:08:55,080 And where there are seeds... 102 00:08:56,160 --> 00:08:57,680 there are sky grazers. 103 00:08:59,000 --> 00:09:00,320 [screeches] 104 00:09:03,120 --> 00:09:06,280 Giant herbivores with six wings 105 00:09:07,040 --> 00:09:09,600 to ride on the dense pillow of air. 106 00:09:10,720 --> 00:09:12,720 [creatures calling] 107 00:09:21,200 --> 00:09:22,800 Because of the extra gravity, 108 00:09:23,440 --> 00:09:26,240 they weigh twice as much  as they would on Earth. 109 00:09:29,520 --> 00:09:31,640 But they don't fall from the sky. 110 00:09:32,320 --> 00:09:36,480 The atmosphere is thick enough to keep them airborne. 111 00:09:43,720 --> 00:09:46,000 Whether on Atlas or on Earth, 112 00:09:46,680 --> 00:09:50,800 flying is always a battle  to overcome gravity. 113 00:09:52,480 --> 00:09:54,480 [birds calling] 114 00:09:59,320 --> 00:10:02,920 [man] You might say I have a pretty complicated relationship with gravity. 115 00:10:04,640 --> 00:10:07,280 And you can really feel that gravity  is a force pulling you down 116 00:10:07,360 --> 00:10:08,800 as you struggle your way up. 117 00:10:11,920 --> 00:10:15,280 But ultimately, my dream  has always been to be able to fly. 118 00:10:18,560 --> 00:10:21,520 Whoo-hoo-hoo! [laughs] 119 00:10:23,480 --> 00:10:27,960 The thing I love most about paragliding  is that it's so simple and intuitive. 120 00:10:28,040 --> 00:10:29,800 It's just you and the air. 121 00:10:32,040 --> 00:10:34,640 Like the sky grazers on Atlas, 122 00:10:35,120 --> 00:10:38,400 paragliders use their wings  to generate lift. 123 00:10:42,120 --> 00:10:44,680 But the atmosphere  is less dense on Earth... 124 00:10:46,640 --> 00:10:49,680 so it takes more effort  to stay airborne. 125 00:10:54,120 --> 00:10:56,480 [Fiorenzo] Most people don't see air as a substance. 126 00:10:58,520 --> 00:11:00,120 But for me, when I'm flying, 127 00:11:00,200 --> 00:11:04,160 I really see it as a fluid  that's moving up and down the valleys 128 00:11:04,240 --> 00:11:05,600 and along the ridges. 129 00:11:08,720 --> 00:11:12,040 It would be really weird  to fly in a very dense atmosphere. 130 00:11:13,040 --> 00:11:16,680 You could just be gliding around  the whole time, effortlessly. 131 00:11:20,120 --> 00:11:24,160 The best way to gain altitude  is to find an updraft, 132 00:11:25,120 --> 00:11:26,880 known as a "thermal." 133 00:11:29,120 --> 00:11:31,160 [Fiorenzo] When you hit the thermal, it's very similar 134 00:11:31,240 --> 00:11:33,440 to when you're in an elevator and it starts. 135 00:11:36,520 --> 00:11:38,080 You feel a push upwards. 136 00:11:38,160 --> 00:11:39,600 Yeah, there we go! 137 00:11:43,720 --> 00:11:45,880 Just the power of nature to pull me up. 138 00:11:50,040 --> 00:11:52,840 When I'm flying  and I see a bird circling up, 139 00:11:52,920 --> 00:11:54,880 it means there must be a thermal there. 140 00:11:55,680 --> 00:11:57,840 So we're always constantly looking at them. 141 00:12:02,400 --> 00:12:06,000 You can really feel the balance between the gravity pulling you down 142 00:12:06,080 --> 00:12:07,640 and the air lifting you up. 143 00:12:08,320 --> 00:12:11,760 You can then use your bodyweight to gain speed, 144 00:12:11,840 --> 00:12:13,840 and use that speed  to generate more energy 145 00:12:14,440 --> 00:12:16,240 and feel that you're moving  through the air. 146 00:12:34,680 --> 00:12:38,320 Gravity may be weaker on Earth than on Atlas... 147 00:12:39,120 --> 00:12:42,680 but the thinner atmosphere means there's less buoyancy. 148 00:12:45,240 --> 00:12:48,400 So, eventually, everything falls. 149 00:13:10,720 --> 00:13:14,520 On Atlas, the sky grazers never need to land. 150 00:13:15,080 --> 00:13:16,800 [screeching] 151 00:13:18,720 --> 00:13:22,280 Their front and back wings  are for direction and thrust. 152 00:13:25,520 --> 00:13:28,280 Their long middle wings are for catching thermals. 153 00:13:32,080 --> 00:13:33,720 Despite their weight, 154 00:13:34,360 --> 00:13:38,320 the air is thick enough for them to live a life 155 00:13:38,800 --> 00:13:40,080 in the sky. 156 00:13:45,120 --> 00:13:48,080 But it's not always a peaceful life. 157 00:13:48,160 --> 00:13:49,600 [creatures chattering] 158 00:13:50,640 --> 00:13:54,760 As on Earth, grazers attract predators. 159 00:13:57,400 --> 00:14:02,000 Using hydrogen-producing bacteria to inflate their air sacs, 160 00:14:02,440 --> 00:14:04,560 they take to the skies. 161 00:14:05,400 --> 00:14:07,400 [calling loudly] 162 00:14:15,080 --> 00:14:17,840 Alone, they're no match for their prey... 163 00:14:20,440 --> 00:14:22,320 so they hunt in a pack... 164 00:14:24,400 --> 00:14:27,800 waiting for a sky grazer  to stray from the group. 165 00:14:38,480 --> 00:14:41,920 Target sighted, they expel their gas... 166 00:14:44,440 --> 00:14:46,240 and attack from above. 167 00:14:56,840 --> 00:14:59,080 The fastest predator on Earth 168 00:14:59,160 --> 00:15:01,320 uses the same tactic. 169 00:15:04,640 --> 00:15:06,600 [man] My interest in flying falcons is... 170 00:15:07,160 --> 00:15:11,240 their predatory instinct coupled with the speed factor... 171 00:15:16,320 --> 00:15:18,360 and how they use that speed  to their advantage. 172 00:15:24,040 --> 00:15:27,240 But just watching  a top predator do its thing... 173 00:15:31,520 --> 00:15:33,280 is perfection. 174 00:15:43,720 --> 00:15:46,600 I probably have 30-some birds  at this moment. 175 00:15:47,440 --> 00:15:49,320 Each bird is a different personality. 176 00:15:50,720 --> 00:15:52,240 What I love about falcons 177 00:15:52,320 --> 00:15:55,440 is how evolution has made the most perfect specimen. 178 00:15:58,080 --> 00:16:00,080 [imitating bird calls] 179 00:16:00,480 --> 00:16:02,480 -[falcon squawking] -[Vahe chirping] 180 00:16:03,200 --> 00:16:04,280 [laughs] 181 00:16:05,440 --> 00:16:07,720 I do have a relationship with these guys. 182 00:16:07,800 --> 00:16:09,840 Certainly from my end, I do. [laughs] 183 00:16:09,920 --> 00:16:11,880 I don't think the falcons  see it that way, 184 00:16:11,960 --> 00:16:14,160 but they certainly see me  as part of the team. 185 00:16:16,560 --> 00:16:21,960 Vahe Alaverdian trains  captive-bred falcons how to hunt. 186 00:16:27,240 --> 00:16:29,240 [Vahe] These birds are  genetically programmed 187 00:16:29,320 --> 00:16:31,600 to be the top-notch  avian predators that they are. 188 00:16:34,440 --> 00:16:35,840 What we do as falconers 189 00:16:35,920 --> 00:16:38,600 is try to awaken that predatorial nature in the bird. 190 00:16:47,240 --> 00:16:49,240 Lure training is the very first step. 191 00:16:49,320 --> 00:16:51,360 Come on, buddy! Hup, hup, hup, hup, hup! 192 00:16:54,640 --> 00:16:57,000 I want to put that lure  in front of the bird, 193 00:16:57,560 --> 00:16:59,920 and get the falcon  to coordinate eye to foot... 194 00:17:00,000 --> 00:17:00,840 Hup, hup! 195 00:17:00,920 --> 00:17:03,040 ...and throw its feet out as if it's gonna grab it. 196 00:17:03,920 --> 00:17:06,920 As that happens, I try to pull that away from the falcon 197 00:17:07,400 --> 00:17:10,360 to get it to shoot up in the air  and repeat this process again. 198 00:17:11,320 --> 00:17:14,800 I wanna see that bird drop down  as vertical as it can. 199 00:17:18,520 --> 00:17:22,120 That's something that they later on will apply to hunting game. 200 00:17:30,440 --> 00:17:35,000 When the falcons are ready, Vahe introduces a prey target... 201 00:17:36,600 --> 00:17:37,840 a racing pigeon. 202 00:17:41,240 --> 00:17:44,200 The falcon can't keep up with the pigeon in a chase, 203 00:17:45,440 --> 00:17:47,560 so its best bet is to drop on it... 204 00:17:48,480 --> 00:17:49,600 using gravity. 205 00:17:55,840 --> 00:17:58,720 [Vahe] When the bird thinks that he's got the advantage, 206 00:17:59,560 --> 00:18:01,680 that's when the wings will get tucked in. 207 00:18:04,640 --> 00:18:07,400 They stoop into a little teardrop shape... 208 00:18:09,040 --> 00:18:10,360 coming down from the heavens. 209 00:18:12,440 --> 00:18:14,880 The kinetic energy of a falcon hitting a pigeon 210 00:18:16,120 --> 00:18:19,560 would be as if you were hit  by a cannonball. 211 00:18:27,440 --> 00:18:30,480 In training, the pigeon invariably gets away, 212 00:18:31,560 --> 00:18:35,120 because the falcon is made to stoop  from less than a thousand feet. 213 00:18:38,440 --> 00:18:39,880 When hunting for real, 214 00:18:40,520 --> 00:18:42,520 it'll drop from a greater height... 215 00:18:44,280 --> 00:18:45,600 to lethal effect. 216 00:18:55,960 --> 00:18:57,760 [creatures calling] 217 00:19:00,840 --> 00:19:02,120 [screeching] 218 00:19:06,440 --> 00:19:08,680 The predators make their move. 219 00:19:19,400 --> 00:19:20,920 [wailing] 220 00:19:23,840 --> 00:19:25,600 They deploy their wings 221 00:19:25,680 --> 00:19:27,040 to create drag... 222 00:19:28,960 --> 00:19:31,200 destabilizing the sky grazer 223 00:19:31,280 --> 00:19:33,680 to devour it on the ground. 224 00:19:39,640 --> 00:19:41,200 [moans] 225 00:19:42,720 --> 00:19:46,600 But this pack is too small to take down such a large beast. 226 00:19:53,640 --> 00:19:55,480 Today, they'll go hungry. 227 00:19:56,240 --> 00:19:57,080 [calls] 228 00:19:57,760 --> 00:19:59,760 [creatures barking and chattering] 229 00:20:01,400 --> 00:20:03,400 [creatures howling] 230 00:20:07,920 --> 00:20:10,880 The sky grazer climbs to a safe height... 231 00:20:12,520 --> 00:20:13,680 to recuperate. 232 00:20:13,760 --> 00:20:15,320 [howling] 233 00:20:19,440 --> 00:20:21,200 But as a fertile female, 234 00:20:21,920 --> 00:20:23,240 she has company. 235 00:20:25,680 --> 00:20:29,360 Male grazers, competing to be chosen as a mate. 236 00:20:30,240 --> 00:20:32,240 [all calling] 237 00:20:36,640 --> 00:20:39,680 Their oversized tails are a handicap, 238 00:20:40,720 --> 00:20:42,200 making it harder to fly. 239 00:20:43,640 --> 00:20:47,440 But to the female, they're a sign of vitality. 240 00:20:48,920 --> 00:20:50,720 [howling] 241 00:20:51,600 --> 00:20:53,880 The first to reach her gets to mate 242 00:20:54,720 --> 00:20:57,000 and pass on his genes. 243 00:20:58,760 --> 00:21:00,760 [birdsong] 244 00:21:04,720 --> 00:21:07,560 The same principle applies on Earth, 245 00:21:08,760 --> 00:21:10,560 whether up in the sky 246 00:21:11,280 --> 00:21:12,800 or down in the dirt. 247 00:21:15,920 --> 00:21:18,600 Males compete for the right to mate. 248 00:21:20,600 --> 00:21:22,760 [man 1] And running, set... 249 00:21:24,160 --> 00:21:27,600 [man 2] I think when people sit at home  watching insects on television, 250 00:21:27,680 --> 00:21:30,200 they imagine the cameraman sitting in the jungle, 251 00:21:30,760 --> 00:21:32,480 in a river or in a hedge, 252 00:21:33,120 --> 00:21:35,880 waiting for this beetle to come across 253 00:21:35,960 --> 00:21:39,440 and reproduce or have a fight  in front of the camera. 254 00:21:42,120 --> 00:21:43,440 It doesn't work that way. 255 00:21:48,880 --> 00:21:53,200 This is a ramshackle old shed  which is attached to my parents' place, 256 00:21:53,320 --> 00:21:54,520 which is just there. 257 00:21:55,640 --> 00:21:58,680 Huge advantages to having a place attached to your mum and dad's. 258 00:21:58,760 --> 00:22:02,880 You get good dinners in the evening and, uh, teas arriving during the day. 259 00:22:03,920 --> 00:22:05,720 -Have a look and see what we're doing. -Oh! 260 00:22:06,360 --> 00:22:07,600 Oh, gosh. 261 00:22:08,560 --> 00:22:10,240 Oh! What on Earth are they? 262 00:22:10,320 --> 00:22:12,400 [Robert] They are rhinoceros beetles. 263 00:22:13,720 --> 00:22:15,280 The male's got these big horns. 264 00:22:15,360 --> 00:22:18,600 The female doesn't.  It's a form of sexual selection, 265 00:22:18,680 --> 00:22:22,720 because the females like males with big horns. 266 00:22:24,320 --> 00:22:25,600 So every time they mate, 267 00:22:25,680 --> 00:22:28,960 they'll mate with a beetle  that has a slightly bigger horn 268 00:22:29,040 --> 00:22:30,760 -than the one they've last seen before. -Oh! 269 00:22:30,840 --> 00:22:33,600 And, therefore, that male passes its genes on. 270 00:22:34,320 --> 00:22:37,400 So, over generations, the horns will get bigger. 271 00:22:39,280 --> 00:22:41,480 -[man 1] Anywhere particular? -[Robert] Um, just on the... 272 00:22:41,560 --> 00:22:43,520 on the log facing the other male. 273 00:22:44,400 --> 00:22:46,320 [man 1] Here they go. They're going straight away. 274 00:22:49,920 --> 00:22:52,160 The horns of a male rhinoceros beetle 275 00:22:52,240 --> 00:22:54,800 are like the tail of a male sky grazer. 276 00:22:57,840 --> 00:23:00,280 They've evolved for sexual competition. 277 00:23:20,640 --> 00:23:22,840 -Ha-ha! -That dominant one's done it again. 278 00:23:28,360 --> 00:23:30,200 [Robert] That's a good shot. The shot we wanted. 279 00:23:30,280 --> 00:23:32,040 -[man 1] Yeah. -[Robert] Going into her, yeah. 280 00:23:35,640 --> 00:23:36,760 One, two, three. 281 00:23:37,960 --> 00:23:39,120 -That right? -[Robert] Yeah. 282 00:23:39,760 --> 00:23:41,120 -[man 1] Yep. -[man 3] That's it. 283 00:23:41,200 --> 00:23:42,680 -Can I... Yes. -You putting that in? 284 00:23:48,000 --> 00:23:51,760 Male insects don't always fight  to snare a mate. 285 00:23:53,240 --> 00:23:57,320 Sometimes it's enough just to show off their physical prowess. 286 00:24:00,160 --> 00:24:02,520 [man 1] Right, I'm gonna bring the male in front of you. 287 00:24:02,600 --> 00:24:03,800 He's coming in from your right. 288 00:24:06,480 --> 00:24:08,080 Now, uh-- He's flown off. 289 00:24:09,200 --> 00:24:11,560 These are stalk-eyed flies. 290 00:24:14,760 --> 00:24:17,440 [Robert] Stalk-eyed fly is an amazing little thing. 291 00:24:17,520 --> 00:24:21,280 It looks a little bit like an ant  with massive eyes on the ends of stalks. 292 00:24:22,680 --> 00:24:26,600 Both the male and the female have eyes on the end of stalks, 293 00:24:26,680 --> 00:24:29,360 but the male has much longer eye stalks than the female. 294 00:24:32,040 --> 00:24:36,200 The males with the long stalks will come up to one another, 295 00:24:36,280 --> 00:24:38,480 and they will, kind of,  have a little dance. 296 00:24:44,640 --> 00:24:46,000 And they will try and judge 297 00:24:46,080 --> 00:24:48,920 which of the two of them  has the bigger stalks. 298 00:24:51,080 --> 00:24:53,000 There they are. That's the standoff! 299 00:24:57,560 --> 00:25:01,280 The winner of that will remain where they are and the loser will then toddle off. 300 00:25:03,280 --> 00:25:05,960 That winner then will gain access to the female, 301 00:25:06,040 --> 00:25:08,200 and be able to reproduce with her, 302 00:25:08,280 --> 00:25:11,000 and that way can pass on  the genetics that he has, 303 00:25:11,080 --> 00:25:14,080 which will include  that of a longer eye stalk. 304 00:25:15,600 --> 00:25:17,600 -[Robert] Yes! Got it. -[man 1] Are-- are you on it? 305 00:25:18,200 --> 00:25:19,400 Oh, It's fantastic. 306 00:25:25,160 --> 00:25:28,280 Normally, it's a second and they're gone. This is fantastic. 307 00:25:34,920 --> 00:25:36,960 Why would the male stalk-eyed fly  go to the effort 308 00:25:37,040 --> 00:25:38,880 of having these enormous eye stalks? 309 00:25:39,440 --> 00:25:43,000 Well, the idea is that you are  conspicuously signaling to the female 310 00:25:43,080 --> 00:25:48,000 that you can have this incredible  investment of energy into this resource 311 00:25:48,080 --> 00:25:49,520 that is completely needless. 312 00:25:51,720 --> 00:25:53,440 And if you can still survive, 313 00:25:53,520 --> 00:25:57,080 if you can carry on flying and living  and not getting predated upon, 314 00:25:57,160 --> 00:26:01,840 and still have this... wasteful extravagance coming out of your head, 315 00:26:01,920 --> 00:26:04,880 then you're gonna be a pretty good bet to reproduce with. 316 00:26:09,640 --> 00:26:11,640 [creatures howling and barking] 317 00:26:19,040 --> 00:26:20,280 On Atlas, 318 00:26:20,360 --> 00:26:26,080 the long tail of the male sky grazer shows he's an ideal choice... 319 00:26:28,200 --> 00:26:30,880 to father the next generation. 320 00:26:32,720 --> 00:26:35,080 [howling] 321 00:26:37,720 --> 00:26:41,040 But the mother can't lay her eggs  in the sky. 322 00:26:45,080 --> 00:26:46,440 [roars] 323 00:26:46,960 --> 00:26:48,800 So she's come down to land. 324 00:26:53,120 --> 00:26:58,280 Because of the gravity, she's too heavy  to launch herself back into the sky. 325 00:26:58,360 --> 00:26:59,840 [roars] 326 00:27:02,080 --> 00:27:03,240 [moans] 327 00:27:04,200 --> 00:27:08,080 To create new life, she must surrender her own. 328 00:27:22,120 --> 00:27:25,760 The babies grow up close  to where their mothers die. 329 00:27:29,320 --> 00:27:33,080 Now they need to get off the ground  and into the air. 330 00:27:33,160 --> 00:27:34,720 [all calling] 331 00:27:40,320 --> 00:27:41,480 [crunching] 332 00:27:41,560 --> 00:27:44,160 But scavengers lie in wait. 333 00:27:45,760 --> 00:27:47,360 Boneless creatures 334 00:27:47,480 --> 00:27:50,360 with no skeleton to give them form. 335 00:27:53,720 --> 00:27:55,840 [calling] 336 00:27:55,920 --> 00:28:00,200 They kill by enveloping and dissolving their prey. 337 00:28:10,920 --> 00:28:17,240 The sky grazers have only just hatched,  but already they're in grave danger. 338 00:28:20,840 --> 00:28:24,000 And now, there's no going back. 339 00:28:24,080 --> 00:28:25,760 [calling and squeaking] 340 00:28:35,240 --> 00:28:36,480 [insects chirping] 341 00:28:36,560 --> 00:28:38,840 [animal howling] 342 00:28:46,040 --> 00:28:48,040 [meerkat grunting] 343 00:28:48,200 --> 00:28:49,640 Every day on Earth, 344 00:28:49,720 --> 00:28:53,000 young animals have to overcome  terrible odds, 345 00:28:53,560 --> 00:28:55,000 if they're to survive. 346 00:28:59,200 --> 00:29:03,760 Sixty percent of meerkats don't make it  to their first birthday. 347 00:29:06,320 --> 00:29:08,920 [woman] For a young meerkat, in their early life, 348 00:29:09,400 --> 00:29:11,840 there's a lot of danger here. 349 00:29:12,680 --> 00:29:16,680 They're vulnerable for many months  after they're born... 350 00:29:19,840 --> 00:29:23,640 but particularly in the first month or two after they emerge from the burrow. 351 00:29:25,920 --> 00:29:29,520 Predators are everywhere, and a constant danger. 352 00:29:34,920 --> 00:29:36,360 There are snakes in this area 353 00:29:37,720 --> 00:29:40,000 that will eat a young meerkat. 354 00:29:51,440 --> 00:29:52,880 -[snake hisses] -[meerkat chatters] 355 00:29:58,360 --> 00:30:00,360 [barking and chattering] 356 00:30:03,400 --> 00:30:06,280 A young meerkat is safe within a group, 357 00:30:07,240 --> 00:30:10,400 but if it lags behind, it's vulnerable. 358 00:30:15,840 --> 00:30:18,720 Scorpions are a constant threat. 359 00:30:22,120 --> 00:30:23,600 [squeaking] 360 00:30:24,560 --> 00:30:27,400 [Kirsty] The young are really completely incompetent, 361 00:30:27,880 --> 00:30:31,120 and totally ignorant when it comes  to dealing with scorpions, initially. 362 00:30:34,240 --> 00:30:36,720 But they can't avoid  this danger forever. 363 00:30:38,640 --> 00:30:42,040 They're going to eventually have to learn how to neutralize the threat. 364 00:30:48,360 --> 00:30:49,440 [whimpers] 365 00:30:49,520 --> 00:30:52,960 The first time that a young meerkat faces a scorpion 366 00:30:53,040 --> 00:30:54,920 and it has to deal with it itself 367 00:30:56,640 --> 00:30:59,000 is probably a terrifying encounter. 368 00:31:00,720 --> 00:31:03,440 This is a real moment of truth. 369 00:31:12,360 --> 00:31:14,360 [yelping] 370 00:31:28,120 --> 00:31:32,280 It's a real rite of passage, because once they've managed to do that themselves, 371 00:31:33,280 --> 00:31:36,320 then they really are at a stage where they can start to forage by themselves 372 00:31:36,400 --> 00:31:39,280 and become independent  and be a useful group member. 373 00:31:41,040 --> 00:31:44,840 So, they've really managed to escape the vulnerability of being a pup 374 00:31:44,920 --> 00:31:48,400 and made that transition  into being an adult. 375 00:31:57,600 --> 00:32:00,960 It's one step on the road to adulthood, 376 00:32:01,040 --> 00:32:03,720 but it's by no means plain sailing  after that. 377 00:32:05,160 --> 00:32:07,680 There are a lot of threats out there, 378 00:32:07,760 --> 00:32:11,080 and it will have to continue to learn  in order to reach adulthood. 379 00:32:18,240 --> 00:32:20,240 [creatures roaring] 380 00:32:23,240 --> 00:32:25,880 If the young sky grazers are to grow up, 381 00:32:27,320 --> 00:32:28,920 they have no choice. 382 00:32:31,320 --> 00:32:33,040 It's time to fly. 383 00:32:33,120 --> 00:32:34,640 [screeching] 384 00:32:46,800 --> 00:32:48,800 [predators chattering] 385 00:33:03,440 --> 00:33:06,000 Even in the air, they're still not safe. 386 00:33:14,160 --> 00:33:18,400 On Atlas, survival is a game of chance. 387 00:33:27,040 --> 00:33:31,080 Life goes on from one generation to the next. 388 00:33:34,640 --> 00:33:36,400 At least for now. 389 00:33:41,640 --> 00:33:46,720 The strong gravity of Atlas  pulls asteroids onto a collision course. 390 00:33:55,120 --> 00:33:57,440 Most burn up in the atmosphere. 391 00:33:59,320 --> 00:34:02,840 But there's a constant threat  something big will get through... 392 00:34:05,160 --> 00:34:08,320 and reset the course of life  on the planet. 393 00:34:18,520 --> 00:34:21,760 Because gravity is weaker  on Earth than Atlas, 394 00:34:21,840 --> 00:34:24,320 asteroid strikes are less frequent. 395 00:34:27,320 --> 00:34:31,240 But when they do occur, they can be catastrophic. 396 00:34:32,880 --> 00:34:34,880 [birds calling] 397 00:34:36,440 --> 00:34:38,640 [man] This is the Yucatán Peninsula. 398 00:34:42,480 --> 00:34:46,200 27,000 square miles of tropical jungle. 399 00:34:49,120 --> 00:34:54,600 But hidden within the jungle  are numerous sinkholes called cenotes. 400 00:35:08,040 --> 00:35:12,280 These are entrances to vast underground cave systems. 401 00:35:15,040 --> 00:35:18,360 There's no surface rivers or streams in the peninsula, 402 00:35:19,320 --> 00:35:23,040 so the only source of water is underground in caves. 403 00:35:30,080 --> 00:35:34,000 But the really interesting thing  is the location of these cenotes. 404 00:35:34,400 --> 00:35:39,440 Although there's probably 10,000  or more cenotes across the peninsula, 405 00:35:39,880 --> 00:35:42,000 in the northwest corner... 406 00:35:45,360 --> 00:35:50,080 they occur in a very well-defined  semicircle. 407 00:35:50,160 --> 00:35:54,440 If we follow that semicircle  out into the Gulf of Mexico... 408 00:35:57,880 --> 00:36:02,800 we now have a complete circle  that marks what one would expect 409 00:36:02,880 --> 00:36:06,000 from the edge  of an asteroid impact crater. 410 00:36:07,800 --> 00:36:10,000 [Thomas] 65 million years ago, 411 00:36:10,080 --> 00:36:13,760 gravity pulled an asteroid  into our solar system. 412 00:36:16,560 --> 00:36:18,520 It smashed into our planet, 413 00:36:18,840 --> 00:36:22,720 causing the extinction  of 75 percent of life on Earth. 414 00:36:33,920 --> 00:36:37,320 The asteroid strike generated  enough debris 415 00:36:38,200 --> 00:36:41,080 to block out sunlight for two years. 416 00:36:44,520 --> 00:36:47,480 A world plunged into darkness. 417 00:36:48,680 --> 00:36:50,000 Nothing could grow. 418 00:36:54,320 --> 00:36:56,000 This would happen on Atlas 419 00:36:56,680 --> 00:36:59,280 if a big enough asteroid  hit the planet. 420 00:37:01,160 --> 00:37:04,480 [Thomas] Cenotes are difficult places to survive... 421 00:37:06,320 --> 00:37:10,000 just like the Earth was 65 million years ago. 422 00:37:12,240 --> 00:37:17,000 What are the characteristics that  a species needs to survive an extinction? 423 00:37:27,720 --> 00:37:29,080 Somebody's in here. 424 00:37:39,640 --> 00:37:42,400 So, crocodiles are very resilient animals. 425 00:37:44,720 --> 00:37:48,000 They live both in the water and on land. 426 00:37:50,320 --> 00:37:54,600 They're generalists. They don't require a specific diet. 427 00:37:56,400 --> 00:37:58,360 They'll eat almost anything. 428 00:38:00,400 --> 00:38:02,800 Whatever is available is good enough, 429 00:38:03,440 --> 00:38:04,560 they'll take it. 430 00:38:09,720 --> 00:38:11,280 Here in this cenote, 431 00:38:12,240 --> 00:38:15,600 one's fallen in, gotten trapped, no way out... 432 00:38:17,040 --> 00:38:18,560 Somehow, some way... 433 00:38:19,840 --> 00:38:21,160 he's succeeded. 434 00:38:22,400 --> 00:38:23,840 They're survivors. 435 00:38:26,920 --> 00:38:30,960 In a changing world, it pays to be a generalist, 436 00:38:31,040 --> 00:38:32,400 not a specialist. 437 00:38:46,400 --> 00:38:49,080 If a big enough asteroid hits Atlas, 438 00:38:49,640 --> 00:38:52,680 the sky grazers and predators  would be doomed. 439 00:38:53,680 --> 00:38:55,680 [screeching] 440 00:38:59,360 --> 00:39:02,640 They're too specialized  to cope with change. 441 00:39:08,040 --> 00:39:11,600 The generalists  are the boneless scavengers. 442 00:39:13,000 --> 00:39:16,240 Like crocodiles, they eat anything... 443 00:39:17,440 --> 00:39:19,200 and live anywhere. 444 00:39:23,640 --> 00:39:26,200 On this imagined high-gravity world, 445 00:39:26,920 --> 00:39:30,120 they could be the great survivors. 446 00:39:43,440 --> 00:39:45,160 How might life adapt 447 00:39:45,240 --> 00:39:47,040 on a different world, 448 00:39:48,320 --> 00:39:49,920 where creatures are trapped 449 00:39:50,560 --> 00:39:52,160 between a searing desert 450 00:39:53,760 --> 00:39:55,680 and a frozen shadowland? 451 00:39:57,720 --> 00:40:00,600 A world of extremes.