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These are the user uploaded subtitles that are being translated: 1 00:00:08,120 --> 00:00:12,040 Pegasus, Bucephalus, Champion, 2 00:00:12,040 --> 00:00:17,520 Trigger, Seabiscuit, Red Rum. 3 00:00:17,520 --> 00:00:19,960 I'm talking about the stuff 4 00:00:19,960 --> 00:00:21,960 of myth and legend. 5 00:00:31,640 --> 00:00:34,160 Just look at her. 6 00:00:34,160 --> 00:00:36,200 She's absolutely 7 00:00:36,200 --> 00:00:39,120 gorgeous, aren't you? 8 00:00:39,120 --> 00:00:43,080 Equus ferus caballus - the horse, to you and I. 9 00:00:46,320 --> 00:00:48,800 A statuesque pinnacle 10 00:00:48,800 --> 00:00:50,680 of natural art. 11 00:00:54,720 --> 00:00:56,600 This is a creature 12 00:00:56,600 --> 00:01:00,360 supremely shaped to move. 13 00:01:18,200 --> 00:01:21,560 Thanks to 700 mighty muscles... 14 00:01:22,800 --> 00:01:26,120 ..and a heart the size of a football... 15 00:01:30,120 --> 00:01:33,160 ..the horse is one of the fastest 16 00:01:33,160 --> 00:01:36,000 and most powerful animals on the planet. 17 00:01:41,680 --> 00:01:44,760 They don't call it horsepower for nothing. 18 00:01:48,720 --> 00:01:51,360 So how did the horse 19 00:01:51,360 --> 00:01:53,480 become one of nature's 20 00:01:53,480 --> 00:01:55,480 greatest athletes? 21 00:01:59,000 --> 00:02:00,960 To answer that... 22 00:02:02,720 --> 00:02:04,720 ..we must travel back in time... 23 00:02:10,560 --> 00:02:12,120 ..to meet the key 24 00:02:12,120 --> 00:02:13,600 movers and shakers... 25 00:02:15,480 --> 00:02:17,440 ..before hooves thundered... 26 00:02:23,120 --> 00:02:25,320 ..or hearts raced. 27 00:02:26,440 --> 00:02:28,640 Back to a time 28 00:02:28,640 --> 00:02:31,600 when almost nothing at all 29 00:02:31,600 --> 00:02:33,840 moved. 30 00:02:58,200 --> 00:03:00,040 The story of the horse 31 00:03:00,040 --> 00:03:04,120 and, in fact, the story of movement 32 00:03:04,120 --> 00:03:06,400 can be traced, incredibly, 33 00:03:06,400 --> 00:03:09,520 right to our own doorstep. 34 00:03:12,560 --> 00:03:14,800 This is a quintessential 35 00:03:14,800 --> 00:03:17,200 English landscape, a rural idyll of 36 00:03:17,200 --> 00:03:19,680 rolling hills and ancient woodlands. 37 00:03:23,560 --> 00:03:25,280 But I've got to tell you 38 00:03:25,280 --> 00:03:28,640 that I was standing here just over half a billion years ago, 39 00:03:28,640 --> 00:03:30,960 the view would have been very different. In fact, I wouldn't 40 00:03:30,960 --> 00:03:34,520 have been standing, I'd have been submerged deep beneath the waves 41 00:03:34,520 --> 00:03:38,120 on the ocean floor. And over millions of years, 42 00:03:38,120 --> 00:03:41,680 these rocks have been pushed up and laid bare. 43 00:03:41,680 --> 00:03:44,440 And they tell us of the history of that time, 44 00:03:44,440 --> 00:03:47,320 a history written in sand and silt. 45 00:03:47,320 --> 00:03:50,960 A history with some fascinating clues. 46 00:03:54,800 --> 00:03:57,000 Hiding in plain sight 47 00:03:57,000 --> 00:03:59,560 are some of the most precious 48 00:03:59,560 --> 00:04:01,360 fossils on the planet. 49 00:04:03,320 --> 00:04:07,320 But millions of years of weathering have warped these rocks, 50 00:04:07,320 --> 00:04:10,360 making them very hard to spot. 51 00:04:12,200 --> 00:04:14,920 Now, I did tell you they were tricky to see, 52 00:04:14,920 --> 00:04:18,280 but there is one right in front of me here. 53 00:04:18,280 --> 00:04:21,160 Just follow my fingers. 54 00:04:21,160 --> 00:04:23,120 It starts up here, 55 00:04:23,120 --> 00:04:25,200 then it arches down. 56 00:04:25,200 --> 00:04:27,360 You can see the ridges in the rock, 57 00:04:27,360 --> 00:04:29,720 particularly visible here. 58 00:04:29,720 --> 00:04:31,400 And then it comes up towards 59 00:04:31,400 --> 00:04:33,960 my shoulder, and this bit follows 60 00:04:33,960 --> 00:04:35,480 right up past my ear. 61 00:04:35,480 --> 00:04:37,760 These would have been made by fronds 62 00:04:37,760 --> 00:04:39,280 and they would have been attached 63 00:04:39,280 --> 00:04:40,680 around a centre point, which 64 00:04:40,680 --> 00:04:42,880 could have been somewhere here. 65 00:04:42,880 --> 00:04:45,200 This is a fossil of Bradgatia. 66 00:04:45,200 --> 00:04:48,400 And I know it doesn't look like much, it might look like 67 00:04:48,400 --> 00:04:50,920 an old cabbage that's been pressed in the rock to you, 68 00:04:50,920 --> 00:04:52,680 but it wasn't an old cabbage. 69 00:04:52,680 --> 00:04:54,560 It wasn't a plant at all. 70 00:04:54,560 --> 00:04:57,240 And this is a very, very important fossil 71 00:04:57,240 --> 00:05:01,360 because it's a fossil of one of the earliest animals 72 00:05:01,360 --> 00:05:03,400 that ever lived on Earth. 73 00:05:08,040 --> 00:05:10,920 Over half a billion years ago, 74 00:05:10,920 --> 00:05:12,720 this slab of rock... 75 00:05:17,080 --> 00:05:20,880 ..was home to some of the very first animals. 76 00:05:26,240 --> 00:05:28,680 Theirs is a peaceful life. 77 00:05:36,560 --> 00:05:39,280 But this strange community 78 00:05:39,280 --> 00:05:41,560 does have a problem. 79 00:05:43,800 --> 00:05:46,280 When animals with large, complex 80 00:05:46,280 --> 00:05:48,760 bodies first evolved, 81 00:05:48,760 --> 00:05:50,480 they couldn't move. 82 00:05:52,040 --> 00:05:54,360 We call them sessile. 83 00:05:57,680 --> 00:05:59,800 Rooted to the ground, 84 00:05:59,800 --> 00:06:02,160 they must rely on the ocean 85 00:06:02,160 --> 00:06:03,920 to bring them what they need... 86 00:06:06,200 --> 00:06:07,840 ..and they're powerless 87 00:06:07,840 --> 00:06:09,520 if it doesn't. 88 00:06:12,160 --> 00:06:14,040 Animal life could have remained 89 00:06:14,040 --> 00:06:16,920 stuck in this way forever, 90 00:06:16,920 --> 00:06:21,360 if it wasn't for an evolutionary maverick. 91 00:06:24,480 --> 00:06:30,160 This is a cast of a fossil that's about 565 million years old, 92 00:06:30,160 --> 00:06:34,160 which means it formed around the same time as Bradgatia. Now, 93 00:06:34,160 --> 00:06:36,920 when the scientists first looked at it, they were initially confused. 94 00:06:36,920 --> 00:06:38,400 It's quite difficult to see. 95 00:06:38,400 --> 00:06:41,840 Look, it starts up here and it runs down here. 96 00:06:41,840 --> 00:06:45,120 It's almost as if someone has been running their fingertip 97 00:06:45,120 --> 00:06:47,360 over some soft mud, 98 00:06:47,360 --> 00:06:49,720 and then it terminates down here. 99 00:06:49,720 --> 00:06:51,240 But if you look here, 100 00:06:51,240 --> 00:06:52,880 you can see there are a few little 101 00:06:52,880 --> 00:06:56,200 half-moon shapes. Now, the reason 102 00:06:56,200 --> 00:06:58,840 those scientists were initially confused is they were probably 103 00:06:58,840 --> 00:07:02,800 looking for a fossil of an animal, but this is not that. 104 00:07:02,800 --> 00:07:05,720 What it is is a fossil of something 105 00:07:05,720 --> 00:07:07,880 an animal left behind. 106 00:07:10,280 --> 00:07:14,480 Now, we think the story goes something like this. 107 00:07:15,880 --> 00:07:20,640 In amongst the creatures stuck to the seabed is a tiny animal, 108 00:07:20,640 --> 00:07:23,440 little more than a gelatinous blob. 109 00:07:25,280 --> 00:07:27,320 Like other animals here, 110 00:07:27,320 --> 00:07:29,080 it eats specks of food 111 00:07:29,080 --> 00:07:31,200 that drift on the ocean currents. 112 00:07:33,200 --> 00:07:36,080 But today, the current has shifted... 113 00:07:37,720 --> 00:07:42,400 ..and is now carrying the meagre morsels just out of reach. 114 00:07:45,840 --> 00:07:48,600 Deprived of food, the only option 115 00:07:48,600 --> 00:07:50,800 for this stationary population 116 00:07:50,800 --> 00:07:52,920 is to sit and wait for their luck 117 00:07:52,920 --> 00:07:56,080 and the currents to change. 118 00:07:57,840 --> 00:08:01,040 But this animal is a pioneer. 119 00:08:06,960 --> 00:08:09,880 You see, this little blob 120 00:08:09,880 --> 00:08:11,720 can do something 121 00:08:11,720 --> 00:08:13,880 that the other animals can't. 122 00:08:25,720 --> 00:08:28,560 Abandon the safety of its home... 123 00:08:29,680 --> 00:08:31,720 ..and move. 124 00:08:39,200 --> 00:08:41,240 With every heave... 125 00:08:42,600 --> 00:08:44,480 ..it leaves a mark. 126 00:08:47,760 --> 00:08:51,440 Some of the earliest animal tracks on the planet. 127 00:09:03,680 --> 00:09:07,400 One small step for this tiny blob, 128 00:09:07,400 --> 00:09:11,160 one giant leap for animalkind. 129 00:09:18,560 --> 00:09:22,720 Now, we'll never know exactly when the first step was taken. 130 00:09:22,720 --> 00:09:25,960 We can presume that there were some missteps - 131 00:09:25,960 --> 00:09:29,280 evolutionary stumbles, if you like - 132 00:09:29,280 --> 00:09:34,240 but that leap between being sessile and motile was a profound one. 133 00:09:36,720 --> 00:09:38,480 Today... 134 00:09:41,840 --> 00:09:44,000 ..whether they are finding food... 135 00:09:45,240 --> 00:09:46,760 ..or mates... 136 00:09:48,320 --> 00:09:50,080 ..or shelter... 137 00:09:51,440 --> 00:09:55,160 ..our planet is an extravaganza 138 00:09:55,160 --> 00:09:56,280 of motion. 139 00:09:57,840 --> 00:10:01,920 An estimated 97% of animals 140 00:10:01,920 --> 00:10:05,200 moving in weird and wonderful ways. 141 00:10:06,880 --> 00:10:09,080 And none of this would be possible 142 00:10:09,080 --> 00:10:12,440 without one key ingredient. 143 00:10:19,440 --> 00:10:20,760 Muscle. 144 00:10:20,760 --> 00:10:21,920 HORSES WHINNY 145 00:10:25,760 --> 00:10:30,240 To understand just how powerful muscle can be, 146 00:10:30,240 --> 00:10:33,680 we need a demonstration from an expert. 147 00:10:33,680 --> 00:10:37,240 I give you...the leech. 148 00:10:39,840 --> 00:10:42,680 I know, not everyone's favourite animal, 149 00:10:42,680 --> 00:10:45,200 but it won't surprise you to know 150 00:10:45,200 --> 00:10:48,800 that I'm rather a fan of the leech. 151 00:10:48,800 --> 00:10:50,040 What are they? 152 00:10:50,040 --> 00:10:51,800 Well, they're a type of worm, 153 00:10:51,800 --> 00:10:54,000 and there are about 700 species 154 00:10:54,000 --> 00:10:55,880 in the world. 155 00:10:55,880 --> 00:10:58,560 Many, like this one, are parasitic. 156 00:10:58,560 --> 00:11:00,040 This is a medicinal leech, 157 00:11:00,040 --> 00:11:01,520 and it's been used by 158 00:11:01,520 --> 00:11:02,960 medical practitioners 159 00:11:02,960 --> 00:11:07,600 to suck the blood from humans for 3,500 years. 160 00:11:07,600 --> 00:11:09,200 But I digress. 161 00:11:09,200 --> 00:11:10,600 What about its movement? 162 00:11:12,320 --> 00:11:14,960 Well, let's take a look at their body. 163 00:11:14,960 --> 00:11:17,160 First thing you'll notice - no legs. 164 00:11:17,160 --> 00:11:18,920 Its body is made up almost 165 00:11:18,920 --> 00:11:20,960 entirely of muscles. 166 00:11:27,200 --> 00:11:31,960 Muscles are built from tiny cells called myocytes. 167 00:11:33,760 --> 00:11:36,240 We sometimes call them muscle fibres. 168 00:11:38,400 --> 00:11:40,040 Within the leech, 169 00:11:40,040 --> 00:11:42,280 there are thousands, 170 00:11:42,280 --> 00:11:44,320 while an animal like the horse 171 00:11:44,320 --> 00:11:46,440 contains millions 172 00:11:46,440 --> 00:11:49,080 and millions of them. 173 00:11:49,080 --> 00:11:53,400 They work thanks to their superpower - 174 00:11:53,400 --> 00:11:56,240 their ability to contract. 175 00:11:59,120 --> 00:12:01,240 Now, this leech's muscle cells 176 00:12:01,240 --> 00:12:03,440 are arranged in opposing sets. 177 00:12:03,440 --> 00:12:05,040 There are circular muscles 178 00:12:05,040 --> 00:12:06,480 that run around its body 179 00:12:06,480 --> 00:12:08,160 and longitudinal muscles, 180 00:12:08,160 --> 00:12:10,520 which run from one end to the other. 181 00:12:10,520 --> 00:12:13,360 So how exactly does it move? Well, 182 00:12:13,360 --> 00:12:14,960 I'll try and demonstrate that here. 183 00:12:14,960 --> 00:12:16,400 Come on. 184 00:12:21,440 --> 00:12:23,480 It stretches forward 185 00:12:23,480 --> 00:12:26,240 using those circular muscles, 186 00:12:26,240 --> 00:12:30,080 and then contracts its longitudinal muscles 187 00:12:30,080 --> 00:12:32,000 and pulls itself forward... 188 00:12:33,600 --> 00:12:36,680 ..so that it can slowly inch across 189 00:12:36,680 --> 00:12:38,240 the palm of my hand 190 00:12:38,240 --> 00:12:39,880 and down my fingers. 191 00:12:41,280 --> 00:12:43,680 Something that I find 192 00:12:43,680 --> 00:12:45,200 quite therapeutic. 193 00:12:47,040 --> 00:12:48,760 You may consider it perverse, 194 00:12:48,760 --> 00:12:50,840 but I'm rather enjoying this. 195 00:12:58,920 --> 00:13:01,840 Today, it's easy to take muscles for granted... 196 00:13:03,720 --> 00:13:06,520 ..but half a billion years ago, 197 00:13:06,520 --> 00:13:09,040 it was primitive muscle cells 198 00:13:09,040 --> 00:13:11,640 that turned contraction 199 00:13:11,640 --> 00:13:13,240 into action... 200 00:13:14,800 --> 00:13:17,240 ..allowing pioneering animals 201 00:13:17,240 --> 00:13:20,240 to take a leap into the unknown. 202 00:13:25,400 --> 00:13:27,440 And the importance of this 203 00:13:27,440 --> 00:13:30,760 simply can't be underestimated, 204 00:13:30,760 --> 00:13:34,640 because from this point on, movement would become 205 00:13:34,640 --> 00:13:39,840 one of the most powerful driving forces in animal evolution. 206 00:13:41,560 --> 00:13:44,880 To reach the next step in the story of the horse, 207 00:13:44,880 --> 00:13:46,640 we must hit fast-forward. 208 00:13:49,840 --> 00:13:52,880 For the next 40 million years, 209 00:13:52,880 --> 00:13:55,240 evolution gallops on. 210 00:14:02,440 --> 00:14:04,760 THUNDERCLAP 211 00:14:04,760 --> 00:14:06,640 Muscles stretch 212 00:14:06,640 --> 00:14:09,160 and shape animal life, 213 00:14:09,160 --> 00:14:11,760 and more and more time is spent... 214 00:14:15,880 --> 00:14:17,680 ..on the go. 215 00:14:34,640 --> 00:14:39,920 As they say, necessity is the mother of invention, 216 00:14:39,920 --> 00:14:43,040 and that was certainly the case for animals experimenting 217 00:14:43,040 --> 00:14:45,200 with early locomotion. 218 00:14:48,560 --> 00:14:51,240 Down here, every trip across 219 00:14:51,240 --> 00:14:54,760 the seafloor demands energy, 220 00:14:54,760 --> 00:14:56,320 and lots of it. 221 00:15:01,080 --> 00:15:03,240 And to get from A to B, 222 00:15:03,240 --> 00:15:08,360 it's thought that ancestors of the horse had evolved to use muscle 223 00:15:08,360 --> 00:15:11,800 in a totally new way. Incredibly, 224 00:15:11,800 --> 00:15:13,880 evidence of this 225 00:15:13,880 --> 00:15:16,800 can still be seen today. 226 00:15:16,800 --> 00:15:21,000 Inside this little plastic tub here, 227 00:15:21,000 --> 00:15:25,120 I have a beautiful animal. 228 00:15:26,280 --> 00:15:29,520 It's called a sea squirt, or a tunicate, 229 00:15:29,520 --> 00:15:32,920 and it's a chordate, which means we're actually related to this. 230 00:15:32,920 --> 00:15:35,280 I know it's difficult to believe, but it's true. 231 00:15:35,280 --> 00:15:39,160 And the benefit of looking at this particular species 232 00:15:39,160 --> 00:15:41,240 is that it's transparent. 233 00:15:41,240 --> 00:15:42,840 I can see inside it. 234 00:15:42,840 --> 00:15:46,160 And I can see a tube running around its body, 235 00:15:46,160 --> 00:15:48,600 and that tube is filled full of 236 00:15:48,600 --> 00:15:51,680 oxygen, minerals and sugar. 237 00:15:53,440 --> 00:15:56,080 It's its blood. 238 00:15:56,080 --> 00:15:59,440 And that tube is contracting. 239 00:16:00,720 --> 00:16:04,800 Waves of muscle contraction are pushing that blood around the body. 240 00:16:06,920 --> 00:16:08,960 Fundamentally, 241 00:16:08,960 --> 00:16:12,520 this is a simple heart. 242 00:16:12,520 --> 00:16:15,480 It's thought that systems like this 243 00:16:15,480 --> 00:16:18,240 allowed this ancestor of the horse 244 00:16:18,240 --> 00:16:20,920 to enjoy an active lifestyle. 245 00:16:30,920 --> 00:16:33,200 Just like the rest of its kind, 246 00:16:33,200 --> 00:16:34,960 nutrient-rich blood 247 00:16:34,960 --> 00:16:36,840 is being pumped through its body, 248 00:16:36,840 --> 00:16:40,320 making its muscles fizz with energy. 249 00:16:45,280 --> 00:16:47,600 Now, most of these creatures 250 00:16:47,600 --> 00:16:49,560 wouldn't win any races, 251 00:16:49,560 --> 00:16:51,040 spending their energy just 252 00:16:51,040 --> 00:16:53,640 wriggling along the seabed. 253 00:16:53,640 --> 00:16:56,960 But the ancestor of the horse 254 00:16:56,960 --> 00:17:00,480 seems to have had an extra boost, 255 00:17:00,480 --> 00:17:02,240 meaning... 256 00:17:07,160 --> 00:17:10,880 ..it can swim harder, better, 257 00:17:10,880 --> 00:17:13,080 faster, stronger. 258 00:17:39,560 --> 00:17:42,360 Its remarkable athletic ability 259 00:17:42,360 --> 00:17:46,120 is thanks to an innovative use of muscle 260 00:17:46,120 --> 00:17:49,800 that unlocked the full potential of the heart. 261 00:17:58,840 --> 00:18:03,280 At this point, evolution all starts to go a bit Frankenstein. 262 00:18:03,280 --> 00:18:05,440 You see, for any muscle to contract, 263 00:18:05,440 --> 00:18:07,480 it requires a stimulus, an order, 264 00:18:07,480 --> 00:18:12,120 and that typically comes in the form of a tiny electric zap. 265 00:18:13,520 --> 00:18:15,120 And it's thought that some 266 00:18:15,120 --> 00:18:16,680 muscle cells inside some of 267 00:18:16,680 --> 00:18:19,480 the earliest hearts took charge, 268 00:18:19,480 --> 00:18:22,520 specialised and started to send out 269 00:18:22,520 --> 00:18:25,520 a series of rhythmic zaps. 270 00:18:25,520 --> 00:18:29,280 And all of the surrounding muscle cells complied by contracting, 271 00:18:29,280 --> 00:18:33,280 generating a single powerful pulse. 272 00:18:35,680 --> 00:18:38,360 Now, these mutant zapping cells 273 00:18:38,360 --> 00:18:41,840 are called pacemakers, and almost all animals have them. 274 00:18:41,840 --> 00:18:46,840 We have a single primary pacemaker called the sinoatrial node. 275 00:18:46,840 --> 00:18:51,720 And as soon as those ancient pacemakers began to pulse, 276 00:18:51,720 --> 00:18:54,840 they instigated a revolution. 277 00:18:58,400 --> 00:19:01,280 In the ancestor of the horse, 278 00:19:01,280 --> 00:19:04,320 those specialised pacemaker cells 279 00:19:04,320 --> 00:19:06,160 have now clustered together 280 00:19:06,160 --> 00:19:07,960 in a localised region... 281 00:19:07,960 --> 00:19:09,680 HEARTBEAT 282 00:19:11,560 --> 00:19:13,120 ..giving its heart 283 00:19:13,120 --> 00:19:15,080 a more powerful beat. 284 00:19:20,240 --> 00:19:22,920 And over many generations... 285 00:19:24,440 --> 00:19:26,920 ..the beat gets stronger. 286 00:19:30,960 --> 00:19:34,000 The muscle walls around the pacemaker thicken... 287 00:19:36,840 --> 00:19:38,320 ..chambers form... 288 00:19:40,400 --> 00:19:41,760 ..and valves... 289 00:19:42,920 --> 00:19:44,840 ..directing blood flow 290 00:19:44,840 --> 00:19:46,640 around the body... 291 00:19:51,440 --> 00:19:53,920 ..becoming an iconic, 292 00:19:53,920 --> 00:19:56,040 life-sustaining organ. 293 00:19:58,440 --> 00:20:01,640 It's an ingenious use of muscle, 294 00:20:01,640 --> 00:20:05,560 one that transformed animal locomotion. 295 00:20:07,520 --> 00:20:11,160 When hearts went from being a simple pump to a more complex 296 00:20:11,160 --> 00:20:12,840 muscular mechanism, 297 00:20:12,840 --> 00:20:17,320 it led to a step change in the evolution of movement. 298 00:20:17,320 --> 00:20:21,080 It allowed animals to become bigger, stronger, faster. 299 00:20:21,080 --> 00:20:25,440 It allowed them to get off of that seabed into the world above. 300 00:20:25,440 --> 00:20:27,360 And from that point on, 301 00:20:27,360 --> 00:20:30,200 life would become a slithering, 302 00:20:30,200 --> 00:20:32,520 crawling, walking, running, 303 00:20:32,520 --> 00:20:35,600 jumping and climbing adventure. 304 00:20:35,600 --> 00:20:37,400 Today... 305 00:20:38,960 --> 00:20:41,520 ..across the globe, 306 00:20:41,520 --> 00:20:43,520 beating hearts are pumping oxygen 307 00:20:43,520 --> 00:20:45,360 through all sorts of bodies. 308 00:20:48,320 --> 00:20:51,520 Around 2.5 billion heartbeats 309 00:20:51,520 --> 00:20:53,840 will supply your muscles with 310 00:20:53,840 --> 00:20:55,360 the energy they need... 311 00:20:56,920 --> 00:20:59,720 ..from your first breath 312 00:20:59,720 --> 00:21:02,960 till your last. 313 00:21:04,840 --> 00:21:08,680 It's a rhythm that connects us all 314 00:21:08,680 --> 00:21:11,400 to the first beats, 315 00:21:11,400 --> 00:21:14,400 over half a billion years ago. 316 00:21:18,520 --> 00:21:21,280 Time to take a leap forward... 317 00:21:23,160 --> 00:21:25,360 ..as the descendants of those 318 00:21:25,360 --> 00:21:27,320 early swimmers get bigger, 319 00:21:27,320 --> 00:21:29,640 stronger and faster. 320 00:21:31,040 --> 00:21:33,360 They shapeshift through countless 321 00:21:33,360 --> 00:21:35,200 iterations until 322 00:21:35,200 --> 00:21:39,000 140 million years later... 323 00:21:41,920 --> 00:21:43,280 ..they have become... 324 00:21:44,680 --> 00:21:46,080 ..fish. 325 00:21:51,240 --> 00:21:55,200 This is an ocean full of powerful bodies. 326 00:21:57,240 --> 00:22:00,320 But here, it's not how many muscles 327 00:22:00,320 --> 00:22:02,800 you've got that counts, 328 00:22:02,800 --> 00:22:04,760 it's how you use them. 329 00:22:08,400 --> 00:22:10,480 Now, there are many forces 330 00:22:10,480 --> 00:22:12,320 shaping evolution. 331 00:22:14,080 --> 00:22:16,920 The need to find food, the need to find mates. 332 00:22:19,080 --> 00:22:22,320 But there are even greater forces at play, 333 00:22:22,320 --> 00:22:25,000 those forces which shape the entire universe. 334 00:22:25,000 --> 00:22:28,920 I'm talking about the laws of physics. 335 00:22:28,920 --> 00:22:31,040 And when it comes to locomotion, 336 00:22:31,040 --> 00:22:33,760 harnessing these would be key. 337 00:22:33,760 --> 00:22:38,000 And fish have achieved that with a remarkable innovation, 338 00:22:38,000 --> 00:22:40,800 something that's startling in its simplicity, 339 00:22:40,800 --> 00:22:43,400 but significant in its importance. 340 00:22:48,080 --> 00:22:49,960 Something that, today, 341 00:22:49,960 --> 00:22:54,640 has helped make fish the success story of our oceans. 342 00:22:57,880 --> 00:23:00,600 Attached to their streamlined bodies, 343 00:23:00,600 --> 00:23:02,960 structures of flesh, cartilage 344 00:23:02,960 --> 00:23:04,840 and bone have evolved. 345 00:23:06,800 --> 00:23:09,160 Tools which their muscles 346 00:23:09,160 --> 00:23:13,200 can control, expanding the mechanics 347 00:23:13,200 --> 00:23:15,360 of movement available to them. 348 00:23:18,360 --> 00:23:21,000 They can be gliders, 349 00:23:21,000 --> 00:23:22,560 thrusters, 350 00:23:22,560 --> 00:23:25,040 rudders. 351 00:23:25,040 --> 00:23:28,520 I'm talking about fins. 352 00:23:34,600 --> 00:23:38,280 And 380 million years ago, 353 00:23:38,280 --> 00:23:40,400 the ancestor of the horse 354 00:23:40,400 --> 00:23:43,840 was a fish, with fins like this. 355 00:23:46,480 --> 00:23:49,320 You can see the fin here. 356 00:23:49,320 --> 00:23:51,040 But look at the base. 357 00:23:51,040 --> 00:23:52,960 It's made up of a series of 358 00:23:52,960 --> 00:23:56,120 robust, strong bones which anchor it to the body, 359 00:23:56,120 --> 00:23:59,640 and they would have been covered with powerful muscles. 360 00:23:59,640 --> 00:24:02,080 And it's this stalk, or lobe, 361 00:24:02,080 --> 00:24:04,760 which gives this group of fishes their name. 362 00:24:04,760 --> 00:24:08,240 We call them the lobe-finned fishes. 363 00:24:08,240 --> 00:24:11,440 Now, I've got to be honest with you, in the open ocean, 364 00:24:11,440 --> 00:24:14,440 this set-up probably didn't confer them with much of 365 00:24:14,440 --> 00:24:15,680 a competitive advantage, 366 00:24:15,680 --> 00:24:18,080 but under certain circumstances, 367 00:24:18,080 --> 00:24:20,960 it proved to be a real bonus. 368 00:24:30,320 --> 00:24:32,640 This is Onychodus... 369 00:24:34,360 --> 00:24:36,040 ..an ancient predator 370 00:24:36,040 --> 00:24:37,840 as big as a crocodile... 371 00:24:39,960 --> 00:24:42,880 ..with muscular lobed fins. 372 00:24:47,080 --> 00:24:49,080 Now, its size and weight 373 00:24:49,080 --> 00:24:51,240 should be an advantage, 374 00:24:51,240 --> 00:24:54,240 making Onychodus a formidable foe. 375 00:24:56,240 --> 00:24:57,840 But when it swims... 376 00:25:00,280 --> 00:25:03,240 ..the water around it is churned up, 377 00:25:03,240 --> 00:25:05,120 giving the game away. 378 00:25:11,080 --> 00:25:14,440 So how does this ocean giant catch its dinner? 379 00:25:20,880 --> 00:25:24,080 The answer lies in those lobed fins. 380 00:25:24,080 --> 00:25:27,240 Inside there is a tool that's just begging to be used, 381 00:25:27,240 --> 00:25:30,200 a tool with enormous potential. 382 00:25:30,200 --> 00:25:32,840 I'm talking about a lever. 383 00:25:38,240 --> 00:25:41,920 You see, the relatively small distance travelled by my hand 384 00:25:41,920 --> 00:25:47,400 and arm here is magnified out there at the tip of the oar, 385 00:25:47,400 --> 00:25:50,000 which is moving far further. 386 00:25:56,880 --> 00:25:59,600 When it comes to generating movement, 387 00:25:59,600 --> 00:26:01,920 muscles are fantastic, 388 00:26:01,920 --> 00:26:03,960 but they do have their limitations. 389 00:26:06,480 --> 00:26:11,360 The lever is life's great multiplier. 390 00:26:16,520 --> 00:26:19,480 Look, a small amount of force 391 00:26:19,480 --> 00:26:22,360 applied by my arms in the boat 392 00:26:22,360 --> 00:26:24,800 is transferred to the tip of those oars, 393 00:26:24,800 --> 00:26:29,280 and it allows me to propel the boat forward. 394 00:26:29,280 --> 00:26:33,080 Not exactly with Olympic prowess, I have to confess, 395 00:26:33,080 --> 00:26:35,200 but with a degree of efficiency. 396 00:26:41,280 --> 00:26:44,200 And it's thought this same principle 397 00:26:44,200 --> 00:26:46,280 helped this hulking fish 398 00:26:46,280 --> 00:26:49,080 to move with incredible delicacy... 399 00:26:50,800 --> 00:26:52,480 ..by doing something 400 00:26:52,480 --> 00:26:54,480 very unfish-like. 401 00:26:59,680 --> 00:27:02,360 Using four of its lobed fins, 402 00:27:02,360 --> 00:27:05,440 along with the physics of levers, 403 00:27:05,440 --> 00:27:08,280 Onychodus turns minimum effort 404 00:27:08,280 --> 00:27:10,920 into maximum movement 405 00:27:10,920 --> 00:27:13,160 and propels itself 406 00:27:13,160 --> 00:27:16,240 stealthily across the seafloor. 407 00:27:30,240 --> 00:27:33,080 Swapping swimming for walking, 408 00:27:33,080 --> 00:27:38,520 it saves its energy for one final, 409 00:27:38,520 --> 00:27:41,000 powerful thrust. 410 00:27:47,600 --> 00:27:51,760 Thanks to its four lobed fins, 411 00:27:51,760 --> 00:27:54,960 Onychodus is a master of the ambush. 412 00:28:01,120 --> 00:28:03,200 So, with skills like these, 413 00:28:03,200 --> 00:28:07,920 you'd expect there to be plenty of lobe-finned fish in the sea, 414 00:28:07,920 --> 00:28:13,240 but today, they have almost entirely vanished from our waters. 415 00:28:19,800 --> 00:28:21,360 My goodness! 416 00:28:22,960 --> 00:28:25,360 That was a bit of a workout. 417 00:28:25,360 --> 00:28:29,040 Now, look, levers are very useful in water, 418 00:28:29,040 --> 00:28:33,040 but they could become even more useful somewhere else. 419 00:28:36,600 --> 00:28:39,000 When fish like Onychodus begin 420 00:28:39,000 --> 00:28:41,360 to use their lobed fins to walk, 421 00:28:41,360 --> 00:28:43,720 rather than swim, 422 00:28:43,720 --> 00:28:46,800 they set off a chain reaction. 423 00:28:53,120 --> 00:28:55,640 Over millions of years... 424 00:28:57,120 --> 00:28:58,840 ..the thick bridge of bones 425 00:28:58,840 --> 00:29:01,600 inside those four fins lengthen... 426 00:29:04,640 --> 00:29:06,640 ..and the muscles surrounding them 427 00:29:06,640 --> 00:29:08,400 shift and alter... 428 00:29:10,400 --> 00:29:14,200 ..creating strong, tough appendages. 429 00:29:15,800 --> 00:29:18,360 No longer fins at all... 430 00:29:20,520 --> 00:29:24,080 ..but four levered limbs. 431 00:29:25,440 --> 00:29:29,400 This was the birth of the tetrapods. 432 00:29:31,240 --> 00:29:33,960 And today, there are more than 433 00:29:33,960 --> 00:29:36,600 30,000 species, 434 00:29:36,600 --> 00:29:38,080 inhabiting every continent. 435 00:29:45,960 --> 00:29:48,200 A diverse supergroup, 436 00:29:48,200 --> 00:29:50,800 all descendants of those fish 437 00:29:50,800 --> 00:29:52,400 with four lobed fins, 438 00:29:52,400 --> 00:29:55,520 are now putting them to use 439 00:29:55,520 --> 00:29:57,480 in very different ways. 440 00:29:59,040 --> 00:30:01,480 Including the horse. 441 00:30:07,720 --> 00:30:09,960 For many tetrapods today, 442 00:30:09,960 --> 00:30:13,400 moving on land is second nature, 443 00:30:13,400 --> 00:30:17,480 but for their ancestors crawling out of the sea, 444 00:30:17,480 --> 00:30:19,640 it was a very different story. 445 00:30:22,760 --> 00:30:25,320 Moving from one ecosystem 446 00:30:25,320 --> 00:30:28,000 to another which is completely different, 447 00:30:28,000 --> 00:30:33,280 requires a painfully slow process of adaptation. 448 00:30:33,280 --> 00:30:35,920 But the creatures that were making that transition 449 00:30:35,920 --> 00:30:39,040 looked a little bit like this. 450 00:30:43,160 --> 00:30:45,080 Oh, yes. 451 00:30:46,960 --> 00:30:49,240 Look at that. 452 00:30:49,240 --> 00:30:51,040 That's special. 453 00:30:51,040 --> 00:30:53,720 One of nature's jewels. 454 00:30:53,720 --> 00:30:55,440 Absolutely beautiful. 455 00:30:55,440 --> 00:30:59,120 This is a marbled newt. 456 00:30:59,120 --> 00:31:02,720 You see how it got its name, with that marbling running down 457 00:31:02,720 --> 00:31:04,280 its back there. 458 00:31:05,960 --> 00:31:07,880 It's an amphibian. 459 00:31:07,880 --> 00:31:11,240 It spends its spring in ponds going through its breeding cycle 460 00:31:11,240 --> 00:31:13,960 and then at the end of summer, it emerges onto land, 461 00:31:13,960 --> 00:31:16,080 where it spends the rest of the year. 462 00:31:16,080 --> 00:31:20,560 But, of course, it's gone through millions of years of evolution, 463 00:31:20,560 --> 00:31:23,920 which allow it to exploit the best of both worlds - 464 00:31:23,920 --> 00:31:26,200 the wet and the dry. 465 00:31:26,200 --> 00:31:28,320 But what about its movement? 466 00:31:28,320 --> 00:31:32,120 Well, in the ponds, it's a fairly good swimmer, to be fair. 467 00:31:32,120 --> 00:31:33,920 What about on land? 468 00:31:33,920 --> 00:31:35,360 Let's give it a go. 469 00:31:44,560 --> 00:31:47,360 They're tentative, they're slow, 470 00:31:47,360 --> 00:31:49,480 they're laborious, they're calculated. 471 00:31:49,480 --> 00:31:52,200 Their little bodies bending from side to side, 472 00:31:52,200 --> 00:31:54,600 as they rather lethargically 473 00:31:54,600 --> 00:31:56,320 move through the environment. 474 00:31:57,840 --> 00:32:00,760 I've never seen a newt galloping or frolicking. 475 00:32:00,760 --> 00:32:03,160 I'm never going to. But this does 476 00:32:03,160 --> 00:32:05,640 tell us something very important. 477 00:32:07,800 --> 00:32:10,720 Movement on land is hard. 478 00:32:10,720 --> 00:32:12,160 Very hard. 479 00:32:18,960 --> 00:32:22,240 This newt can get away with having 480 00:32:22,240 --> 00:32:26,160 four left feet because in a pinch, 481 00:32:26,160 --> 00:32:28,560 it can retreat to a habitat 482 00:32:28,560 --> 00:32:31,040 it finds easier to negotiate. 483 00:32:37,840 --> 00:32:41,520 But 350 million years ago, 484 00:32:41,520 --> 00:32:43,440 if the ancestors of the horse 485 00:32:43,440 --> 00:32:45,040 were to pursue a life 486 00:32:45,040 --> 00:32:47,240 solely on solid ground, 487 00:32:47,240 --> 00:32:51,480 they would need to be far more coordinated. 488 00:32:51,480 --> 00:32:56,400 And the answer to their coordination conundrum came, once again, 489 00:32:56,400 --> 00:32:59,000 with an evolutionary innovation 490 00:32:59,000 --> 00:33:02,440 from the ever-adaptable muscle. 491 00:33:02,440 --> 00:33:06,600 Inside almost every muscle in my body, 492 00:33:06,600 --> 00:33:09,800 I have something called a stretch sensor. 493 00:33:09,800 --> 00:33:13,480 And stretch sensors are highly specialised muscle fibres 494 00:33:13,480 --> 00:33:17,520 that are constantly monitoring how and when 495 00:33:17,520 --> 00:33:20,000 those muscles are moving. 496 00:33:20,000 --> 00:33:25,040 The key thing is that they are all linked together in a complex web, 497 00:33:25,040 --> 00:33:27,360 so each individual muscle knows 498 00:33:27,360 --> 00:33:30,920 exactly when every...other muscle 499 00:33:30,920 --> 00:33:35,080 is moving. Now, despite the fact that this is an incredibly 500 00:33:35,080 --> 00:33:39,240 complicated system, I bet that you've never even thought about it, 501 00:33:39,240 --> 00:33:41,920 and that's because you don't have to, 502 00:33:41,920 --> 00:33:43,880 despite the fact that it's crucial 503 00:33:43,880 --> 00:33:46,200 for every single move that we make. 504 00:33:55,800 --> 00:33:59,960 Tiny stretch sensors allow the muscles to communicate 505 00:33:59,960 --> 00:34:02,360 with the central nervous system, 506 00:34:02,360 --> 00:34:05,240 giving us and most living tetrapods 507 00:34:05,240 --> 00:34:07,560 the ability to co-ordinate movement 508 00:34:07,560 --> 00:34:10,120 with astonishing precision. 509 00:34:10,120 --> 00:34:13,360 Often, faster than you can think. 510 00:34:20,360 --> 00:34:22,000 Look at that. 511 00:34:28,200 --> 00:34:30,160 Just look at the legs there. 512 00:34:30,160 --> 00:34:33,960 Every part of them is moving independently, 513 00:34:33,960 --> 00:34:36,000 in isolation, at the same time. 514 00:34:36,000 --> 00:34:38,600 And then the weight - 515 00:34:38,600 --> 00:34:42,640 that's got to be balanced between all four feet. 516 00:34:42,640 --> 00:34:44,760 And running down those legs - 517 00:34:44,760 --> 00:34:47,520 just going to speed it up, look at that - 518 00:34:47,520 --> 00:34:50,560 are ripples of muscles. 519 00:34:50,560 --> 00:34:52,880 That's the glutes, that's the quads, 520 00:34:52,880 --> 00:34:57,040 that's the hamstrings, all working in unison. 521 00:35:00,040 --> 00:35:02,200 Without these little gizmos, 522 00:35:02,200 --> 00:35:04,560 these stretch sensors hiding in muscles 523 00:35:04,560 --> 00:35:07,400 and the complex network that joins them all together, 524 00:35:07,400 --> 00:35:11,840 animals with bodies like this simply would not have been able to evolve. 525 00:35:15,880 --> 00:35:18,320 It was down to this innovation 526 00:35:18,320 --> 00:35:19,960 that animal bodies could become 527 00:35:19,960 --> 00:35:22,360 radically more coordinated, 528 00:35:22,360 --> 00:35:25,800 and those tiny little bones, once hidden in those fish's fins, 529 00:35:25,800 --> 00:35:27,680 could really come into their own. 530 00:35:29,680 --> 00:35:33,280 Those fully terrestrial animals 531 00:35:33,280 --> 00:35:38,320 could put one foot in front of the other with extreme precision... 532 00:35:40,320 --> 00:35:42,680 ..and this was a game-changer. 533 00:35:48,040 --> 00:35:50,440 Time for us to motor on. 534 00:35:53,560 --> 00:35:56,760 Over the next 300 million years, 535 00:35:56,760 --> 00:35:59,320 the tetrapods scattered across the Earth. 536 00:36:05,240 --> 00:36:08,400 Whilst life faced some cosmic curveballs... 537 00:36:10,200 --> 00:36:12,320 ..it was never fully derailed. 538 00:36:14,640 --> 00:36:16,440 And evolution carried on... 539 00:36:19,600 --> 00:36:21,280 ..tumbling us... 540 00:36:25,080 --> 00:36:26,720 ..into a new world... 541 00:36:30,920 --> 00:36:32,560 ..where the way you move... 542 00:36:34,080 --> 00:36:37,720 ..can be a matter of life 543 00:36:37,720 --> 00:36:39,360 and death. 544 00:36:44,400 --> 00:36:46,640 This is Phenacodus. 545 00:36:54,280 --> 00:36:57,560 Life looks pretty serene, 546 00:36:57,560 --> 00:37:00,600 but Phenacodus must constantly 547 00:37:00,600 --> 00:37:04,200 be on guard, because this world 548 00:37:04,200 --> 00:37:06,880 is full of expert movers... 549 00:37:06,880 --> 00:37:08,400 BRANCH SNAPS 550 00:37:08,400 --> 00:37:10,120 ..whose bodies... 551 00:37:12,080 --> 00:37:14,640 ..have evolved for the chase. 552 00:37:18,280 --> 00:37:20,640 GROWLING When the hunt is on... 553 00:37:20,640 --> 00:37:23,920 ..surging adrenaline, thumping hearts 554 00:37:23,920 --> 00:37:26,800 and straining muscles will only take you so far. 555 00:37:31,280 --> 00:37:33,360 Faced with a situation it can't 556 00:37:33,360 --> 00:37:35,040 muscle its way out of... 557 00:37:36,920 --> 00:37:39,080 ..the secret to Phenacodus's 558 00:37:39,080 --> 00:37:43,320 survival lies in its feet. 559 00:37:48,000 --> 00:37:50,200 Come on, Siddy! Nance, come on! 560 00:37:50,200 --> 00:37:51,760 DOG BARKS 561 00:37:56,880 --> 00:38:00,960 Do you know, sometimes, people say, "Why poodles? 562 00:38:00,960 --> 00:38:03,680 "Why poodles?" they say. And I facetiously reply, 563 00:38:03,680 --> 00:38:05,200 "Are there other breeds of dog?" 564 00:38:05,200 --> 00:38:06,400 I mean, look at them. 565 00:38:06,400 --> 00:38:09,800 Boundless energy, incredibly loyal, 566 00:38:09,800 --> 00:38:11,400 and they can also help us 567 00:38:11,400 --> 00:38:14,200 with an important part of our story. 568 00:38:14,200 --> 00:38:16,000 You see, hidden beneath 569 00:38:16,000 --> 00:38:18,960 this curly fur here is a crucial 570 00:38:18,960 --> 00:38:21,880 step change in evolution. 571 00:38:21,880 --> 00:38:24,720 Now, I don't need to tell you about my foot and leg, 572 00:38:24,720 --> 00:38:27,000 you've got your own. Starts off at the toe, 573 00:38:27,000 --> 00:38:28,560 goes across the foot to the ankle, 574 00:38:28,560 --> 00:38:32,400 then you've got the shin, the knee, the thigh. 575 00:38:32,400 --> 00:38:34,400 We put our feet down 576 00:38:34,400 --> 00:38:36,040 onto the ground, we plant them 577 00:38:36,040 --> 00:38:38,200 flat on the ground like that. 578 00:38:38,200 --> 00:38:39,560 We're what we call 579 00:38:39,560 --> 00:38:43,520 plantigrade animals. It's quite an efficient way of walking. 580 00:38:43,520 --> 00:38:46,720 Nancy, on the other hand, is altogether different. 581 00:38:46,720 --> 00:38:48,920 Let's take a look at her back leg here. 582 00:38:48,920 --> 00:38:51,280 You see, her toes stretch 583 00:38:51,280 --> 00:38:52,760 from here to here. 584 00:38:52,760 --> 00:38:54,640 The rest of her foot bones 585 00:38:54,640 --> 00:38:56,280 all the way up to here, which looks 586 00:38:56,280 --> 00:38:57,840 like a backward-pointing knee, 587 00:38:57,840 --> 00:39:01,120 but this is, in fact, her ankle. 588 00:39:01,120 --> 00:39:02,840 Her knee is all the way 589 00:39:02,840 --> 00:39:04,520 up here. So Nancy 590 00:39:04,520 --> 00:39:07,120 is effectively standing up 591 00:39:07,120 --> 00:39:10,040 on her toe bones. 592 00:39:10,040 --> 00:39:13,280 She's a digitigrade animal, 593 00:39:13,280 --> 00:39:15,320 and that's altogether different. 594 00:39:15,320 --> 00:39:18,240 It means that you move in a very different way, doesn't it? 595 00:39:18,240 --> 00:39:19,920 Shall we show them? 596 00:39:19,920 --> 00:39:22,400 Come on, let's go. Come on. 597 00:39:30,880 --> 00:39:33,760 Right, Sid, Nancy. 598 00:39:33,760 --> 00:39:35,520 Let's see them in action. 599 00:39:35,520 --> 00:39:37,040 BARKING 600 00:39:42,000 --> 00:39:44,840 Woo-hoo-hoo! BARKING 601 00:39:44,840 --> 00:39:46,560 Look at them go! You see, 602 00:39:46,560 --> 00:39:50,360 this change in anatomy allows the leg to become longer, 603 00:39:50,360 --> 00:39:52,400 the stride to become longer, 604 00:39:52,400 --> 00:39:56,080 and more efficient use of all of that elastic energy 605 00:39:56,080 --> 00:39:58,800 stored in the muscles and tendons 606 00:39:58,800 --> 00:40:00,720 above their ankle. 607 00:40:00,720 --> 00:40:01,880 Look at that! 608 00:40:01,880 --> 00:40:03,200 Bouncing about. 609 00:40:03,200 --> 00:40:05,160 BARKING 610 00:40:05,160 --> 00:40:08,320 Alacrity, agility. 611 00:40:08,320 --> 00:40:10,320 Critically, speed. 612 00:40:10,320 --> 00:40:13,240 That is a happy poodle. 613 00:40:14,480 --> 00:40:17,680 And, you know, this adaptation has occurred a number of times 614 00:40:17,680 --> 00:40:21,280 in terrestrial animals. But having said that, 615 00:40:21,280 --> 00:40:25,120 if you really want to be a creature living life in the fast lane, 616 00:40:25,120 --> 00:40:29,640 evolution can offer you one more gear. 617 00:40:29,640 --> 00:40:32,080 Siddy, Nance, come on! Come on! 618 00:40:34,280 --> 00:40:38,360 When it comes to speed and efficiency, plantigrade - 619 00:40:38,360 --> 00:40:41,760 that's us - will get you from A to B. 620 00:40:41,760 --> 00:40:44,920 Digitigrade - like my dogs - 621 00:40:44,920 --> 00:40:47,040 ups the revs. 622 00:40:48,760 --> 00:40:51,520 But 56 million years ago, 623 00:40:51,520 --> 00:40:55,440 Phenacodus was on the verge of something new. 624 00:40:56,480 --> 00:41:00,800 Not just bouncing on the balls of its feet, 625 00:41:00,800 --> 00:41:05,440 but pushing off from the very tips of its toes... 626 00:41:08,920 --> 00:41:11,680 ..lengthening its stride even further. 627 00:41:13,040 --> 00:41:16,200 So future generations take the concept... 628 00:41:17,320 --> 00:41:18,920 ..and run with it. 629 00:41:23,920 --> 00:41:25,960 As bones elongate 630 00:41:25,960 --> 00:41:27,560 and muscles bulk up... 631 00:41:28,800 --> 00:41:30,320 ..they spend more 632 00:41:30,320 --> 00:41:32,600 and more time on tiptoe... 633 00:41:35,920 --> 00:41:37,320 ..and in the process... 634 00:41:38,840 --> 00:41:40,600 ..find the most efficiency 635 00:41:40,600 --> 00:41:42,480 in trading many toes 636 00:41:42,480 --> 00:41:45,600 for one large, 637 00:41:45,600 --> 00:41:47,600 powerful shock absorber. 638 00:41:52,720 --> 00:41:54,520 Look at this. 639 00:41:54,520 --> 00:41:57,520 This is clearly a cast 640 00:41:57,520 --> 00:41:59,880 of a fossil of a hoof. 641 00:41:59,880 --> 00:42:04,120 A hoof at the end of a very long leg. 642 00:42:04,120 --> 00:42:08,080 A leg that's clearly all about movement. 643 00:42:08,080 --> 00:42:11,800 A leg, though, that is surprisingly different than ours. 644 00:42:11,800 --> 00:42:13,840 You see, essentially, it's foot 645 00:42:13,840 --> 00:42:15,680 all the way from here to here. 646 00:42:15,680 --> 00:42:18,480 This is the equivalent of our ankle. 647 00:42:18,480 --> 00:42:21,120 The bone here would be like those in the sole of our foot. 648 00:42:21,120 --> 00:42:22,480 And down here, 649 00:42:22,480 --> 00:42:26,480 it's balancing on a single tiptoe. 650 00:42:26,480 --> 00:42:29,520 The hoof itself would have been made of keratin, 651 00:42:29,520 --> 00:42:31,560 just like our fingernail. 652 00:42:31,560 --> 00:42:33,640 And also, what's interesting is at the other end, 653 00:42:33,640 --> 00:42:36,640 the front legs weren't attached to the skeleton. 654 00:42:36,640 --> 00:42:38,080 They were embedded 655 00:42:38,080 --> 00:42:40,880 in a heavy mass of powerful muscle, 656 00:42:40,880 --> 00:42:45,360 and this gave it the capacity for a greater stride. 657 00:42:45,360 --> 00:42:47,480 You see this groove here? 658 00:42:47,480 --> 00:42:50,040 Running down here would have been a tendon, 659 00:42:50,040 --> 00:42:51,920 perhaps half a metre long, 660 00:42:51,920 --> 00:42:54,920 a giant elastic band. 661 00:42:54,920 --> 00:42:57,360 But it is a leg with compromises. 662 00:42:57,360 --> 00:43:00,480 I mean, you can't pick anything up with a hoof, 663 00:43:00,480 --> 00:43:02,040 you can't manipulate anything. 664 00:43:02,040 --> 00:43:04,440 It's lost all dexterity, 665 00:43:04,440 --> 00:43:06,720 at the expense of speed. 666 00:43:09,000 --> 00:43:13,160 This three-million-year-old hoof 667 00:43:13,160 --> 00:43:15,720 tells us of the arrival 668 00:43:15,720 --> 00:43:19,080 of a new group of animals. 669 00:43:19,080 --> 00:43:22,360 Animals we call Equus. 670 00:43:34,560 --> 00:43:37,040 These single-hoofed mammals 671 00:43:37,040 --> 00:43:40,040 first evolved on the plains of North America... 672 00:43:42,160 --> 00:43:44,440 ..before spreading across the globe. 673 00:43:47,160 --> 00:43:49,600 Among them 674 00:43:49,600 --> 00:43:52,560 was one remarkable species. 675 00:43:54,720 --> 00:43:57,200 Equus ferus. 676 00:44:00,360 --> 00:44:04,560 Known to you and I as the horse. 677 00:44:10,720 --> 00:44:12,400 Its body shaped 678 00:44:12,400 --> 00:44:14,680 generation after generation... 679 00:44:19,520 --> 00:44:22,200 ..by the evolutionary drive to move. 680 00:44:25,560 --> 00:44:29,080 700 muscles, passed down 681 00:44:29,080 --> 00:44:31,240 over half a billion years, 682 00:44:31,240 --> 00:44:34,040 from a pioneer who changed the world. 683 00:44:34,040 --> 00:44:37,440 A huge heart, with an ancient beat, 684 00:44:37,440 --> 00:44:41,000 that began deep beneath the waves. 685 00:44:41,000 --> 00:44:43,240 Long levered limbs 686 00:44:43,240 --> 00:44:46,800 that once helped a fish to walk... 687 00:44:48,360 --> 00:44:51,120 ..and four large hooves, 688 00:44:51,120 --> 00:44:53,160 the legacy of ancestors 689 00:44:53,160 --> 00:44:56,280 who had to run for their lives. 690 00:44:57,600 --> 00:45:01,000 But there's one final twist 691 00:45:01,000 --> 00:45:03,360 in the story of the horse, 692 00:45:03,360 --> 00:45:05,240 because Equus ferus 693 00:45:05,240 --> 00:45:07,560 was about to encounter 694 00:45:07,560 --> 00:45:09,960 a new force of evolution. 695 00:45:17,400 --> 00:45:19,200 Another species 696 00:45:19,200 --> 00:45:22,760 on an evolutionary journey of its own. 697 00:45:22,760 --> 00:45:25,000 A bipedal tetrapod, 698 00:45:25,000 --> 00:45:27,240 with opposable thumbs, 699 00:45:27,240 --> 00:45:31,360 and an overinflated sense of self-worth. 700 00:45:48,720 --> 00:45:51,960 4,000 years ago, Homo sapiens - 701 00:45:51,960 --> 00:45:53,840 that's us - inhabited 702 00:45:53,840 --> 00:45:55,320 much of the planet. 703 00:45:55,320 --> 00:45:56,840 HORSE WHINNIES 704 00:45:56,840 --> 00:45:59,880 We had city states and agriculture. 705 00:45:59,880 --> 00:46:02,640 Empires were beginning to grow. 706 00:46:04,840 --> 00:46:07,720 And at this time, in Europe and Asia, 707 00:46:07,720 --> 00:46:09,520 we begin to see evidence 708 00:46:09,520 --> 00:46:12,040 of a growing relationship 709 00:46:12,040 --> 00:46:14,160 between horses 710 00:46:14,160 --> 00:46:15,960 and humans. 711 00:46:18,640 --> 00:46:23,160 Now, no-one is exactly sure how the first horse was tamed. 712 00:46:23,160 --> 00:46:25,560 Maybe someone caught one of those wild horses, 713 00:46:25,560 --> 00:46:28,520 took it into captivity, gave it shelter, food, 714 00:46:28,520 --> 00:46:32,240 cared for it, loved it and trained it. 715 00:46:32,240 --> 00:46:35,400 But what we do know is that in pretty short time, 716 00:46:35,400 --> 00:46:40,080 we took these strong, efficient, powerful animals 717 00:46:40,080 --> 00:46:43,920 and turned them into our perfect companions. 718 00:46:43,920 --> 00:46:46,520 And, you know, we didn't just tame them. 719 00:46:46,520 --> 00:46:49,840 Over generation after generation, we bred them, 720 00:46:49,840 --> 00:46:52,560 choosing those characteristics which favoured the way 721 00:46:52,560 --> 00:46:55,600 we wanted horses to be. 722 00:46:55,600 --> 00:46:58,520 So in the end, we took the wild horse 723 00:46:58,520 --> 00:47:01,800 and we turned it into the workhorse. 724 00:47:14,640 --> 00:47:16,760 We chose the strongest. 725 00:47:18,320 --> 00:47:20,000 We chose the most powerful. 726 00:47:21,560 --> 00:47:24,640 But we also chose the friendliest, 727 00:47:24,640 --> 00:47:26,880 the most amenable. 728 00:47:29,840 --> 00:47:32,480 And for better or for worse, 729 00:47:32,480 --> 00:47:34,560 over the generations, 730 00:47:34,560 --> 00:47:36,960 the horse was altered. 731 00:47:40,560 --> 00:47:42,520 The ancestors of the modern horse 732 00:47:42,520 --> 00:47:44,160 were a pretty wild bunch. 733 00:47:45,280 --> 00:47:47,800 Diverse not only in terms of their physical appearance, 734 00:47:47,800 --> 00:47:50,760 but also, their genetic make-up. 735 00:47:50,760 --> 00:47:52,880 And about 4,000 years ago, 736 00:47:52,880 --> 00:47:55,800 we see two gene variants appear. 737 00:47:55,800 --> 00:47:57,160 HORSE WHINNIES 738 00:47:57,160 --> 00:47:59,960 Now, one of those appears to make them less aggressive, 739 00:47:59,960 --> 00:48:01,520 more manageable. 740 00:48:03,680 --> 00:48:07,080 And the other, which appears to give them a stronger back, 741 00:48:07,080 --> 00:48:09,760 making them easier to ride. 742 00:48:09,760 --> 00:48:11,520 Now, what's interesting is that 743 00:48:11,520 --> 00:48:14,000 within the space of just a few hundred years, 744 00:48:14,000 --> 00:48:16,040 we'd spread those gene variants 745 00:48:16,040 --> 00:48:18,400 throughout the population. 746 00:48:20,200 --> 00:48:22,960 The wild horse was effectively gone. 747 00:48:22,960 --> 00:48:25,840 We had one global species, 748 00:48:25,840 --> 00:48:28,600 selected by humans. 749 00:48:28,600 --> 00:48:30,080 You. 750 00:48:30,080 --> 00:48:33,320 Yes. I know. 751 00:48:33,320 --> 00:48:35,320 It wasn't my fault. 752 00:48:35,320 --> 00:48:37,040 I wasn't around then. 753 00:48:49,160 --> 00:48:52,480 Today, the horse goes by a new name. 754 00:48:54,160 --> 00:48:58,160 Equus ferus caballus. 755 00:48:58,160 --> 00:49:00,080 The domestic horse. 756 00:49:01,560 --> 00:49:04,120 Our relationship is a special one. 757 00:49:05,960 --> 00:49:07,560 Together, we've travelled to 758 00:49:07,560 --> 00:49:09,480 every corner of the globe. 759 00:49:11,400 --> 00:49:12,960 Step by step... 760 00:49:14,320 --> 00:49:15,960 ..and side by side. 761 00:49:21,520 --> 00:49:23,400 We often think of evolution 762 00:49:23,400 --> 00:49:25,360 as a battle between species, 763 00:49:25,360 --> 00:49:27,520 a game of winners and losers, 764 00:49:27,520 --> 00:49:29,880 a game of survival of the fittest. 765 00:49:29,880 --> 00:49:33,000 But very occasionally, species come together 766 00:49:33,000 --> 00:49:36,880 and the result is greater than the sum of their parts. 767 00:49:36,880 --> 00:49:40,440 Now, there's no doubt we played a hugely instrumental role 768 00:49:40,440 --> 00:49:42,200 in the evolution of the horse, 769 00:49:42,200 --> 00:49:45,800 but then the horse has had an impact on us too, 770 00:49:45,800 --> 00:49:50,880 because without this remarkable animal as our greatest partner, 771 00:49:50,880 --> 00:49:55,040 we simply wouldn't be the species we are today. 772 00:49:59,000 --> 00:50:01,800 The horse's evolutionary journey 773 00:50:01,800 --> 00:50:03,680 is just one thread 774 00:50:03,680 --> 00:50:06,360 in an extraordinary tapestry... 775 00:50:07,880 --> 00:50:11,800 ..that weaves together every animal, 776 00:50:11,800 --> 00:50:14,520 in fact, every living thing 777 00:50:14,520 --> 00:50:16,240 on our planet. 778 00:50:17,920 --> 00:50:21,080 It's taken four billion years 779 00:50:21,080 --> 00:50:23,560 to get here, but, boy, 780 00:50:23,560 --> 00:50:27,000 has life come a very, very long way! 781 00:50:30,080 --> 00:50:33,000 From the cell that began it all... 782 00:50:35,160 --> 00:50:36,640 ..to sex... 783 00:50:37,760 --> 00:50:39,560 ..to competition... 784 00:50:40,840 --> 00:50:43,120 ..to predation and protection. 785 00:50:49,560 --> 00:50:52,920 From the oceans to the land 786 00:50:52,920 --> 00:50:56,320 and, for some, back again. 787 00:50:59,680 --> 00:51:03,320 For others, onwards to the skies. 788 00:51:05,520 --> 00:51:08,560 There was a bum that changed the world. 789 00:51:09,800 --> 00:51:11,880 There were jaws, limbs, 790 00:51:11,880 --> 00:51:14,600 hearts and minds. 791 00:51:14,600 --> 00:51:17,720 Minds which have evolved to sense, 792 00:51:17,720 --> 00:51:20,400 to move, to love, 793 00:51:20,400 --> 00:51:22,080 to contemplate... 794 00:51:25,160 --> 00:51:27,560 ..and, in our case, 795 00:51:27,560 --> 00:51:29,000 to begin to understand 796 00:51:29,000 --> 00:51:31,320 our own origins. 797 00:51:37,040 --> 00:51:39,840 A journey of knowledge 798 00:51:39,840 --> 00:51:41,880 that we're still on today. 799 00:51:44,520 --> 00:51:47,000 There's an outdated view, 800 00:51:47,000 --> 00:51:48,960 a mistaken idea, 801 00:51:48,960 --> 00:51:53,960 that we humans are the be-all and end-all of evolution. 802 00:51:53,960 --> 00:51:56,480 That everything we've explored, everything we've shown you 803 00:51:56,480 --> 00:52:02,280 in this series was just about making us the perfect organism, 804 00:52:02,280 --> 00:52:05,000 the paragon of life on Earth. 805 00:52:05,000 --> 00:52:07,760 But it's simply not true. 806 00:52:07,760 --> 00:52:10,680 We're not perfect and we weren't made. 807 00:52:10,680 --> 00:52:13,760 We've been shaped by exactly the same forces 808 00:52:13,760 --> 00:52:19,440 that have shaped every organism that's ever lived on this planet. 809 00:52:19,440 --> 00:52:22,040 And through a startling twist of fate, 810 00:52:22,040 --> 00:52:24,480 we are now having a profound effect 811 00:52:24,480 --> 00:52:26,920 on evolution ourselves. 812 00:52:26,920 --> 00:52:30,160 A dramatic, rapid and scary one 813 00:52:30,160 --> 00:52:33,120 because of what we're doing to our environment 814 00:52:33,120 --> 00:52:38,800 and because we're driving a massive extinction event. 815 00:52:38,800 --> 00:52:43,760 Now, evolution does feast on extinction. 816 00:52:43,760 --> 00:52:47,320 It loves the opportunities, the vacancies. 817 00:52:47,320 --> 00:52:51,160 So whatever we do now, life will go on. 818 00:52:51,160 --> 00:52:54,280 Life will be bright, life will be beautiful, 819 00:52:54,280 --> 00:52:57,720 life will be wonderful. 820 00:52:57,720 --> 00:53:01,880 But in evolutionary terms, what about us? 821 00:53:01,880 --> 00:53:04,360 Could we become shorter, 822 00:53:04,360 --> 00:53:06,640 slower, more short-sighted? 823 00:53:06,640 --> 00:53:10,720 Might we become smarter, more stupid? 824 00:53:12,160 --> 00:53:16,360 I don't think it really matters about our anatomy at this point. 825 00:53:17,680 --> 00:53:20,760 I think what matters is how we think, 826 00:53:20,760 --> 00:53:25,520 imagine and create our way out of our situation. 827 00:53:27,000 --> 00:53:31,880 I think that what needs to be driving human evolution right now... 828 00:53:33,400 --> 00:53:34,720 ..is hope. 829 00:53:57,200 --> 00:53:58,920 But before we go... 830 00:54:01,560 --> 00:54:03,280 ..how did we bring the story 831 00:54:03,280 --> 00:54:05,240 of evolution to life? 832 00:54:08,600 --> 00:54:10,400 The way that one animal, 833 00:54:10,400 --> 00:54:11,720 over millions of years, 834 00:54:11,720 --> 00:54:14,680 can transform into something radically different 835 00:54:14,680 --> 00:54:17,520 was once a mystery lost to time. 836 00:54:19,240 --> 00:54:21,680 - If we think about a book, we have lots of different pages 837 00:54:21,680 --> 00:54:23,600 that tell us the story from start to finish. 838 00:54:25,040 --> 00:54:28,080 However, with evolution and fossils, some of those pages are missing. 839 00:54:30,080 --> 00:54:32,080 - But occasionally, evidence 840 00:54:32,080 --> 00:54:34,040 is unearthed of the process 841 00:54:34,040 --> 00:54:38,640 in action. In 2004, palaeontologists 842 00:54:38,640 --> 00:54:40,400 in the Canadian Arctic 843 00:54:40,400 --> 00:54:43,240 discovered a ground-breaking fossil. 844 00:54:43,240 --> 00:54:45,440 - So this is a cast of Tiktaalik. 845 00:54:45,440 --> 00:54:49,640 Now, Tiktaalik lived about 375 million years ago, 846 00:54:49,640 --> 00:54:51,720 and it's got the scales very much 847 00:54:51,720 --> 00:54:53,960 like modern-day fish have today. 848 00:54:53,960 --> 00:54:56,920 And what's quite unusual is that it actually has a neck. 849 00:54:56,920 --> 00:54:58,480 And these bones that are around there, 850 00:54:58,480 --> 00:54:59,800 these are the sort of collar bone 851 00:54:59,800 --> 00:55:01,480 or shoulder girdle. It looks like 852 00:55:01,480 --> 00:55:04,000 a cross between a fish and an amphibian, 853 00:55:04,000 --> 00:55:07,000 and that's because that's exactly what it is. 854 00:55:07,000 --> 00:55:08,400 - Tiktaalik was really this kind of 855 00:55:08,400 --> 00:55:10,480 unique snapshot in evolutionary time 856 00:55:10,480 --> 00:55:12,480 at this key moment 857 00:55:12,480 --> 00:55:14,240 for the water-to-land transition. 858 00:55:15,680 --> 00:55:17,160 - So it's a perfect example of 859 00:55:17,160 --> 00:55:18,400 a transitional fossil. 860 00:55:18,400 --> 00:55:20,440 - Transitional fossils are incredibly rare. 861 00:55:21,640 --> 00:55:24,080 They play the really important role of filling those gaps 862 00:55:24,080 --> 00:55:26,880 between morphologies that we kind of know are there, 863 00:55:26,880 --> 00:55:28,720 but we don't really know exactly 864 00:55:28,720 --> 00:55:30,840 what they might have looked like. 865 00:55:30,840 --> 00:55:33,400 - Transitional fossils represent 866 00:55:33,400 --> 00:55:35,200 just one out of millions, 867 00:55:35,200 --> 00:55:37,760 possibly billions, of individuals 868 00:55:37,760 --> 00:55:39,240 that, over generations, 869 00:55:39,240 --> 00:55:42,040 contribute to evolutionary change. 870 00:55:42,040 --> 00:55:45,040 Coming up with a way to illustrate this 871 00:55:45,040 --> 00:55:47,040 posed a huge challenge 872 00:55:47,040 --> 00:55:49,760 to the visual effects team behind the series. 873 00:55:49,760 --> 00:55:52,160 - Evolution does not move in a straight line, 874 00:55:52,160 --> 00:55:54,440 because it is purely opportunistic 875 00:55:54,440 --> 00:55:55,880 and slightly haphazard. 876 00:55:55,880 --> 00:55:58,960 - It's tinkering. It's messing with what's already there, 877 00:55:58,960 --> 00:56:00,440 rather than kind of always 878 00:56:00,440 --> 00:56:03,200 necessarily inventing something from scratch. 879 00:56:03,200 --> 00:56:05,800 - It's all about a great grand experiment 880 00:56:05,800 --> 00:56:07,280 and just seeing what happens. 881 00:56:08,600 --> 00:56:11,240 - The team spent thousands of hours 882 00:56:11,240 --> 00:56:12,960 crafting and animating 883 00:56:12,960 --> 00:56:14,760 computer-generated models 884 00:56:14,760 --> 00:56:16,200 to bring ancient animals 885 00:56:16,200 --> 00:56:17,520 back to life. 886 00:56:17,520 --> 00:56:19,800 But to illustrate the randomness 887 00:56:19,800 --> 00:56:23,160 and variation seen as life evolves, 888 00:56:23,160 --> 00:56:25,680 they needed to experiment. 889 00:56:25,680 --> 00:56:28,720 After consulting scientists to accurately model 890 00:56:28,720 --> 00:56:30,960 the key evolutionary changes, 891 00:56:30,960 --> 00:56:33,120 they used generative AI software 892 00:56:33,120 --> 00:56:36,480 to create hundreds of variations, 893 00:56:36,480 --> 00:56:39,280 representing countless generations. 894 00:56:39,280 --> 00:56:42,440 And by hand-selecting and merging 895 00:56:42,440 --> 00:56:44,520 the best results with their original 896 00:56:44,520 --> 00:56:46,440 animations, they were able 897 00:56:46,440 --> 00:56:48,200 to condense millions of years 898 00:56:48,200 --> 00:56:50,120 of evolution... 899 00:56:50,120 --> 00:56:51,600 - Look at that! - There's bones inside! 900 00:56:51,600 --> 00:56:52,800 - No way! 901 00:56:52,800 --> 00:56:55,600 - ..into a matter of seconds. 902 00:56:55,600 --> 00:56:57,160 - In reality, this would take 903 00:56:57,160 --> 00:56:58,520 millions of years. 904 00:57:00,440 --> 00:57:01,920 - This is a fantastic way 905 00:57:01,920 --> 00:57:04,440 to illustrate the evolution of form. 906 00:57:04,440 --> 00:57:06,640 This is basically how I imagine it playing out in my head. 907 00:57:17,440 --> 00:57:18,960 - This series has been over 908 00:57:18,960 --> 00:57:21,200 four billion years in the making... 909 00:57:22,680 --> 00:57:25,080 ..and as a certain Charles Darwin 910 00:57:25,080 --> 00:57:26,840 once wrote, 911 00:57:26,840 --> 00:57:29,280 "From so simple a beginning 912 00:57:29,280 --> 00:57:32,120 "endless forms most beautiful 913 00:57:32,120 --> 00:57:34,480 "and most wonderful have been, 914 00:57:34,480 --> 00:57:37,320 "and are being evolved." 915 00:57:37,320 --> 00:57:40,120 - One of the big key life lessons that 916 00:57:40,120 --> 00:57:42,000 I've learned from studying evolution 917 00:57:42,000 --> 00:57:44,360 is that change is constant 918 00:57:44,360 --> 00:57:46,640 and change is the norm. So things 919 00:57:46,640 --> 00:57:48,240 have always changed and will always 920 00:57:48,240 --> 00:57:49,800 continue to change, and life 921 00:57:49,800 --> 00:57:51,160 will always continue to adapt. 922 00:57:54,160 --> 00:57:55,880 - That's how it's always been, 923 00:57:55,880 --> 00:57:57,120 and there's no reason to believe 924 00:57:57,120 --> 00:57:58,960 that's not how it's going to continue to be. 925 00:58:11,520 --> 00:58:15,040 - Do you want to know how an elephant is related to a clownfish? 926 00:58:15,040 --> 00:58:18,760 Discover more in a poster from the Open University on 927 00:58:18,760 --> 00:58:20,760 the tree of life. To get your free copy, 928 00:58:20,760 --> 00:58:23,360 scan the QR code on-screen or ring... 929 00:58:27,040 --> 00:58:28,520 ..or visit... 66715

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