1 00:00:05,501 --> 00:00:11,742 It's long been known that millions of years ago one special creature walked here. 2 00:00:14,213 --> 00:00:18,163 These are fossilised footsteps from the dawn of mankind, 3 00:00:18,488 --> 00:00:22,095 the oldest footprints made by a human ancestor. 4 00:00:23,553 --> 00:00:26,166 For years scientists have been convinced 5 00:00:26,400 --> 00:00:32,517 that whatever creature walked here would hold the key to the biggest mystery in all evolution: 6 00:00:32,768 --> 00:00:40,559 why it is that human beings have evolved to be so different, so unlike all other animals? 7 00:00:41,388 --> 00:00:45,424 Now a new discovery may just provide the answer to that question. 8 00:00:45,643 --> 00:00:49,319 The trouble is it is not what anyone had expected. 9 00:00:49,476 --> 00:00:55,124 When I first saw this fossil I realised it was going to really change our ideas of human evolution. 10 00:00:58,284 --> 00:01:00,631 It is a change of such importance 11 00:01:00,820 --> 00:01:03,933 that the story of how man rose up from the apes 12 00:01:04,121 --> 00:01:08,971 and came to rule the world may now have to be rewritten. 13 00:01:29,842 --> 00:01:35,224 In this secret vault in Kenya they keep human history under lock and key. 14 00:01:38,369 --> 00:01:41,717 Here they guard the most precious fossils in the world, 15 00:01:42,109 --> 00:01:45,551 the fossils that tell the story of our evolution 16 00:01:51,869 --> 00:01:58,206 and there is one fossil here more remarkable that all the others found just recently. 17 00:01:58,738 --> 00:02:02,148 It is of a human ancestor like no other. 18 00:02:02,961 --> 00:02:07,576 We didn't realise how different it was until we began comparing in the, in the museum 19 00:02:07,874 --> 00:02:10,846 and that was a very exciting time because we waited such a long time 20 00:02:11,136 --> 00:02:17,118 to have the specimen prepared and then when we got to study it and we kept taking something else out of the 21 00:02:17,319 --> 00:02:20,698 cupboard and, and comparing it and it was different and this was different and that was different. 22 00:02:22,325 --> 00:02:27,419 Meave Leakey and her team spent a whole year painstakingly assembling their discovery 23 00:02:27,614 --> 00:02:29,491 from just tiny fragments 24 00:02:32,946 --> 00:02:37,114 and as they analysed it further the more baffled they became. 25 00:02:38,402 --> 00:02:43,071 This fossil didn't fit into any known pattern of human evolution. 26 00:02:44,498 --> 00:02:47,440 We just simply couldn't find something that looked really similar. 27 00:02:47,978 --> 00:02:51,207 Quite quickly we began to realise we had something very, very different 28 00:02:51,351 --> 00:02:53,135 and then of course it was a matter of saying well, 29 00:02:53,432 --> 00:02:57,672 OK, to have something different but which group does it fit in, it must fit with something that's already known 30 00:02:58,204 --> 00:03:02,553 and, and then it didn't, it didn't seem to work that way either and so 31 00:03:02,725 --> 00:03:07,466 in the end we realised that we did have something that was, it was unknown, it was new. 32 00:03:11,049 --> 00:03:13,803 They had put together a skull, 33 00:03:14,381 --> 00:03:17,636 the oldest skull ever found of a human ancestor. 34 00:03:18,043 --> 00:03:23,800 When word of this discovery spread, science was faced with something stunning 35 00:03:24,646 --> 00:03:27,743 because this fossil should not exist. 36 00:03:28,745 --> 00:03:32,703 Because of it a mystery that many in science thought had been solved 37 00:03:33,172 --> 00:03:35,253 will have to be reopened, 38 00:03:36,395 --> 00:03:39,743 for this skull says that a key part of the theory 39 00:03:40,056 --> 00:03:44,813 of how human beings evolved from apes and came to dominate the planet 40 00:03:45,376 --> 00:03:48,693 has all been based on a mistake. 41 00:04:03,666 --> 00:04:08,329 The big mystery of human evolution began ten million years ago 42 00:04:08,626 --> 00:04:14,039 when the Earth was a very different place, far more lush and tropical than it is today. 43 00:04:14,650 --> 00:04:18,170 Back then one kind of creature reigned supreme: 44 00:04:19,125 --> 00:04:20,110 the apes. 45 00:04:20,574 --> 00:04:25,737 They were everywhere. The Earth really was the planet of the apes. 46 00:04:28,274 --> 00:04:33,155 These were apes like we can barely imagine. There were 50 different species of them 47 00:04:33,430 --> 00:04:35,608 and they roamed right across the planet. 48 00:04:36,422 --> 00:04:40,252 There was the huge cevapithecus in the jungles of the East. 49 00:04:40,490 --> 00:04:42,630 It was twice the weight of a man. 50 00:04:43,719 --> 00:04:47,549 There was tiny limnopithecus that lurked high in the forest canopy 51 00:04:47,762 --> 00:04:50,616 eating fruit no other creature could reach. 52 00:04:51,560 --> 00:04:54,827 This world was an ape's paradise. 53 00:04:56,679 --> 00:05:02,137 For the apes living some ten million years ago it was really a great time 54 00:05:02,138 --> 00:05:06,615 because we had an enormous variety of different types of apes 55 00:05:06,834 --> 00:05:10,792 those living more in the trees, those living more on the ground, 56 00:05:11,027 --> 00:05:15,110 there were very big apes and there were smaller apes 57 00:05:15,407 --> 00:05:19,209 and it must have been really an exciting time. 58 00:05:20,884 --> 00:05:24,592 Apes were the most intelligent animals alive at the time. 59 00:05:25,092 --> 00:05:29,223 They may even have used sticks and stones as tools to get food, 60 00:05:29,895 --> 00:05:35,027 but then the fossil record shows the planet of the apes just stops. 61 00:05:36,764 --> 00:05:43,335 All this enormous variety of different types of apes disappeared 62 00:05:43,866 --> 00:05:52,909 about some 7 or 8 million years ago and we really cannot find an exact explication why this happened. 63 00:05:54,255 --> 00:05:59,465 Seven million years later there are just a few survivors from the planet of the apes 64 00:05:59,778 --> 00:06:03,596 like the orang-utan, the gorilla and the chimpanzee 65 00:06:05,395 --> 00:06:09,650 and in place of all those apes is an animal clearly related to them, 66 00:06:09,838 --> 00:06:12,138 but which could not be more different: 67 00:06:12,686 --> 00:06:13,906 human beings. 68 00:06:20,430 --> 00:06:24,811 No other creature has ever thought like us, built like us, 69 00:06:25,390 --> 00:06:27,127 dreamed like us. 70 00:06:36,797 --> 00:06:40,395 We are more intelligent than any other animal there has ever been. 71 00:06:42,054 --> 00:06:46,231 We alone can aspire to understand the deepest mysteries of the Universe, 72 00:06:46,645 --> 00:06:49,790 we alone can hope to control nature itself, 73 00:06:50,150 --> 00:06:54,343 we are light years ahead of anything that has ever lived before. 74 00:06:59,161 --> 00:07:03,135 We choose to go to the Moon in this decade and do the other things, 75 00:07:03,527 --> 00:07:07,360 not because they are easy but because they are hard. 76 00:07:08,924 --> 00:07:14,604 Just one small step for man, one giant leap for mankind. 77 00:07:16,700 --> 00:07:20,439 This gulf between us and all other creatures is so huge 78 00:07:20,674 --> 00:07:26,369 that long ago it convinced scientists that we must have been produced by an evolutionary process 79 00:07:26,650 --> 00:07:29,262 that was different from all other animals. 80 00:07:29,528 --> 00:07:32,704 In some way we had been chosen, 81 00:07:37,148 --> 00:07:40,356 but what had made us evolve into something so unique, 82 00:07:40,715 --> 00:07:45,863 what evolutionary development had allowed us to become so vastly more intelligent 83 00:07:46,254 --> 00:07:47,959 than all other animals. 84 00:07:49,883 --> 00:07:53,810 That was the great question the disciples of Charles Darwin, 85 00:07:54,014 --> 00:07:57,284 evolution's founding father, were left with. 86 00:07:59,286 --> 00:08:04,418 The answer, early anthropologists thought, would lie out there in the rocks. 87 00:08:05,012 --> 00:08:09,221 Somewhere there would be a fossil that could explain it all. 88 00:08:10,300 --> 00:08:13,852 It would be a fossil of an animal that was basically an ape, 89 00:08:14,149 --> 00:08:18,154 but which showed the first key human characteristic to have evolved. 90 00:08:18,999 --> 00:08:21,925 It was believed that that first key characteristic 91 00:08:22,363 --> 00:08:25,664 would prove to be the thing that had made us so superior 92 00:08:25,710 --> 00:08:27,212 to all other animals 93 00:08:28,480 --> 00:08:32,141 and of all the evolutionary changes between humans and apes 94 00:08:32,453 --> 00:08:34,111 one dwarfs them all: 95 00:08:35,582 --> 00:08:38,711 our brains have grown to an extraordinary size 96 00:08:38,929 --> 00:08:41,699 and this bewitched early anthropologists. 97 00:08:42,106 --> 00:08:47,425 Humans have very large brains and our cranial capacity is about 1400 cubic centimetres 98 00:08:47,629 --> 00:08:52,666 and this contrasts to the chimpanzees that are around 400 cubic centimetres, 99 00:08:52,932 --> 00:08:56,171 so humans are three times the size of a chimpanzee brain. 100 00:08:56,907 --> 00:09:02,414 And so over 100 years ago the big brain theory of human evolution was born. 101 00:09:02,852 --> 00:09:06,263 It seemed obvious that our special evolutionary process 102 00:09:06,435 --> 00:09:10,158 must have begun with the development of our superior intelligence. 103 00:09:11,379 --> 00:09:14,915 According to the theory, in the last seven million years 104 00:09:15,118 --> 00:09:18,169 an ape must have evolved to have a slightly bigger brain. 105 00:09:18,623 --> 00:09:24,318 This more intelligent ape would have given birth to a line of progressively bigger brained super-apes 106 00:09:24,583 --> 00:09:27,212 who ultimately turned into humans. 107 00:09:27,822 --> 00:09:30,137 When we're looking at human evolution 108 00:09:30,294 --> 00:09:33,830 what we have to realise is that we define ourselves by our big brain 109 00:09:33,970 --> 00:09:37,162 and by everything that results from that big brain 110 00:09:37,475 --> 00:09:43,092 and for many years palaeoanthropologists have felt that that was what we're looking for, 111 00:09:43,093 --> 00:09:45,970 the, the most important period in human evolution 112 00:09:46,160 --> 00:09:50,322 is when we see that big brain, that somehow this defines our species. 113 00:09:51,386 --> 00:09:54,593 The big brain theory dominated early anthropology. 114 00:09:54,860 --> 00:09:57,692 All they needed was the fossil to prove it. 115 00:09:58,286 --> 00:10:02,354 It turned the quest to find the fossil with the first key human characteristic 116 00:10:02,762 --> 00:10:07,080 into the quest for the fossil of an ape-like animal with a big brain. 117 00:10:07,690 --> 00:10:11,711 The only question was how would they know when they had found it? 118 00:10:12,070 --> 00:10:16,060 How big would its brain have to be to make it our ancestor? 119 00:10:19,423 --> 00:10:23,350 One man who thought he knew the answer was one of the anthropology's legends: 120 00:10:23,541 --> 00:10:24,745 Louis Leakey. 121 00:10:29,001 --> 00:10:32,239 Leakey set what he called a cerebral rubicon. 122 00:10:32,724 --> 00:10:37,637 By pouring beads into a skull's brain cavity and then measuring the volume of the beads 123 00:10:37,934 --> 00:10:40,375 it is possible to estimate brain size. 124 00:10:45,835 --> 00:10:48,542 Leakey said the fossil they were looking for 125 00:10:48,730 --> 00:10:51,608 would have a brain bigger than that of any known ape, 126 00:10:52,187 --> 00:10:56,662 but about half that of a human's measured in cubic centimes. 127 00:10:57,601 --> 00:11:02,373 Anthropologists were trying to define what the first human would be like 128 00:11:02,483 --> 00:11:08,006 and they set a value for brain size that was outside the range of any known ape 129 00:11:08,241 --> 00:11:13,732 and they settled on a figure of about 600-700 cubic centimetres. 130 00:11:15,719 --> 00:11:18,661 Leakey looked in Africa for 50 years. 131 00:11:18,911 --> 00:11:22,760 He found bones of ancient apes, he even found a skull, 132 00:11:22,917 --> 00:11:29,331 but its brain was below the 600 cubic centimetres needed for it to be the elusive ape with the big brain, 133 00:11:29,644 --> 00:11:33,790 the ape that had set us out on our unique evolutionary path, 134 00:11:34,869 --> 00:11:39,094 but all the while he knew it had to be out there in Africa 135 00:11:39,469 --> 00:11:42,723 somewhere just waiting for him to find it. 136 00:11:44,378 --> 00:11:49,385 By the 1970s Louis Leakey was an old man with failing health. 137 00:11:49,698 --> 00:11:52,858 It was time for someone else to take up the quest. 138 00:12:02,934 --> 00:12:08,300 . The call was answered by Louis's son, Richard and his wife Meave. 139 00:12:12,399 --> 00:12:18,689 They sent teams scouring the rocks of Kenya looking for the elusive fossil of the ape with the big brain, 140 00:12:19,393 --> 00:12:25,213 that key characteristic that scientists believed triggered the amazing evolution of human beings. 141 00:12:33,975 --> 00:12:40,154 Then, after searching for four years, they saw something peeping out from the rocks. 142 00:12:43,299 --> 00:12:48,947 It was just a few fragments sitting on the surface that really didn't look like anything 143 00:12:49,276 --> 00:12:53,125 and in fact the field crew had noticed it and looked at it and thought that it was 144 00:12:53,344 --> 00:12:54,548 bits of an antelope. 145 00:12:55,909 --> 00:13:00,478 This bit of an antelope was dated at around 2.8 million years old, 146 00:13:00,994 --> 00:13:05,359 halfway between the present day and the end of the planet of the apes, 147 00:13:05,516 --> 00:13:10,069 the perfect age for the key development that had separated humans from apes 148 00:13:10,256 --> 00:13:15,982 to have happened and there was something about this fossil that intrigued Richard Leakey 149 00:13:16,624 --> 00:13:19,456 and so he began trying to put the pieces together. 150 00:13:20,113 --> 00:13:23,586 After about a week of Richard not doing a very good job, I have to say, 151 00:13:23,868 --> 00:13:27,044 they got bored with it and, and said OK, you have a go. 152 00:13:27,779 --> 00:13:31,831 It was a task that Meave Leakey had never attempted before. 153 00:13:32,457 --> 00:13:37,151 And so for the next few weeks I had a wonderful time trying to stick all these pieces together 154 00:13:37,573 --> 00:13:42,251 and I think it was, it was definitely one of the most challenging and exciting jigsaw puzzles I've ever done 155 00:13:42,877 --> 00:13:44,363 and it gradually came together. 156 00:13:48,760 --> 00:13:53,094 It was not the skull of an antelope, but of an ape-like creature 157 00:13:53,547 --> 00:13:56,395 and it seemed to have an unusually large brain. 158 00:13:56,896 --> 00:14:01,386 The question was did it cross the magical cerebral rubicon, 159 00:14:01,731 --> 00:14:04,030 600 cubic centimetres? 160 00:14:04,469 --> 00:14:09,491 They couldn't wait to get it back to Nairobi and to do it properly, so they decided to fudge it in camp but 161 00:14:09,741 --> 00:14:12,244 using whatever they had and they didn't have very much, 162 00:14:12,527 --> 00:14:15,311 so what they did was they filled the cranium with sand and then they poured the sand 163 00:14:15,953 --> 00:14:21,460 into a rain gauge and they measured the amount of sand that filled the cranial vault 164 00:14:21,772 --> 00:14:27,999 and it came to eight inches of rain which they estimated was to be about 800cc which is pretty close. 165 00:14:28,000 --> 00:14:31,147 I think now it's, it's 785 or something like that. 166 00:14:31,914 --> 00:14:34,620 Richard Leakey believed he had done it. 167 00:14:35,043 --> 00:14:38,344 He thought he had found the fossil his father had been looking for, 168 00:14:38,860 --> 00:14:42,052 so there was one person he just had to tell. 169 00:14:42,521 --> 00:14:45,744 Richard said well, I really want to take it to Nairobi 'cos I want to show my father 170 00:14:45,963 --> 00:14:49,295 and so he flew back to Nairobi with it and to show Louis. 171 00:14:49,796 --> 00:14:55,694 Louis was very excited when he, when he saw the specimen and it was, it was a great moment I think for both of them. 172 00:14:56,805 --> 00:15:00,044 Two weeks later Louis Leakey died. 173 00:15:00,764 --> 00:15:04,456 The skull, now known simply by its museum classification number, 174 00:15:04,581 --> 00:15:05,911 14/70, 175 00:15:06,146 --> 00:15:08,868 seemed to have fulfilled his life's quest, 176 00:15:09,243 --> 00:15:12,028 to find the fossil of the ape with the big brain, 177 00:15:12,106 --> 00:15:15,845 the fossil that seemed to prove humans had evolved in their special way 178 00:15:16,123 --> 00:15:19,346 because of the early development of their intelligence. 179 00:15:23,680 --> 00:15:26,214 14/70 was a sensation, 180 00:15:26,872 --> 00:15:28,984 reconstructed all over the world 181 00:15:29,218 --> 00:15:32,879 so that everyone could gaze upon this crucial human ancestor. 182 00:15:33,380 --> 00:15:37,010 it became more than just a fossil, but an icon, 183 00:15:37,416 --> 00:15:41,953 because here seemed to be proof that what had always seemed so obvious 184 00:15:42,313 --> 00:15:44,894 that it must be our superior intelligence 185 00:15:45,035 --> 00:15:47,789 that had set us apart from all other animals 186 00:15:47,992 --> 00:15:51,888 and the first key evolutionary change that had begun it all 187 00:15:51,951 --> 00:15:54,892 must have been the development of the big brain. 188 00:15:55,533 --> 00:16:01,150 So here seemed to be evidence for what you can think of as the sort of brain-led theory of human evolution, 189 00:16:01,151 --> 00:16:05,202 that we have a large brain early on in the course of human evolution 190 00:16:05,327 --> 00:16:12,915 and in a sense once you have a large brain everything else is inevitable and this seemed to show exactly that pattern. 191 00:16:14,683 --> 00:16:19,611 It now seemed beyond doubt that human beings had evolved in their unique way 192 00:16:19,956 --> 00:16:26,293 because of the big brain, but this whole theory was about to be proved wrong. 193 00:16:38,811 --> 00:16:43,129 The triumph of Leakey and 14/70 was to be short-lived. 194 00:16:43,239 --> 00:16:47,572 In 1974 a young American researcher called Don Johanson 195 00:16:47,713 --> 00:16:53,533 was hard at it in the field looking in rocks that were about the same age as 14/70. 196 00:16:54,181 --> 00:16:57,561 I was out surveying in the morning with one of my graduate students Tom Gray 197 00:16:57,748 --> 00:17:02,113 and as we were walking back to, to the Land Rover it was now noon time and it was, 198 00:17:02,144 --> 00:17:06,212 well it was close to 110 degrees and it was time to head back to camp, 199 00:17:06,276 --> 00:17:12,283 I happened to glance over my shoulder and as I looked down I spotted this piece of bone, 200 00:17:12,565 --> 00:17:13,942 a little piece of elbow, 201 00:17:15,037 --> 00:17:20,873 and as I looked up this slope, a very gradual slope, I saw glistening in that sunlight 202 00:17:21,123 --> 00:17:22,688 other pieces of bone. 203 00:17:25,254 --> 00:17:31,778 They had stumbled upon almost the entire skeleton of a three million year old ape-like creature. 204 00:17:33,061 --> 00:17:35,892 Here was a specimen that was astonishingly complete, 205 00:17:35,971 --> 00:17:39,772 something that really literally had never been found before. 206 00:17:41,228 --> 00:17:44,779 Round the campfire they christened their new discovery. 207 00:17:45,984 --> 00:17:49,457 One night when we were celebrating we were listening to a Beatles tape 208 00:17:49,661 --> 00:17:54,667 and on that tape Lucy in the Sky with Diamonds was playing and a member of the expedition said 209 00:17:55,027 --> 00:17:57,639 well, why don't we just call the skeleton Lucy. 210 00:18:02,819 --> 00:18:05,713 Back in America they began to analyse Lucy. 211 00:18:06,386 --> 00:18:10,673 She was classified as an Australopithecine, an ape-like creature, 212 00:18:10,845 --> 00:18:14,021 and was dated at about 3.2 million years old, 213 00:18:14,444 --> 00:18:16,728 just older than 14/70, 214 00:18:18,762 --> 00:18:22,939 but then as they slowly put the bones together there came proof 215 00:18:23,221 --> 00:18:26,052 that she really was a human ancestor 216 00:18:32,733 --> 00:18:37,223 because this ape-like creature had one clear human characteristic 217 00:18:37,817 --> 00:18:42,151 and it wasn't a big brain, but something quite different. 218 00:18:42,871 --> 00:18:45,734 She seemed to walk in a way that only humans do. 219 00:18:46,172 --> 00:18:51,820 Lucy was, as scientists say, bipedal, unlike apes who are quadrapedal. 220 00:18:52,367 --> 00:18:55,605 She walked on two legs not four. 221 00:18:56,012 --> 00:19:00,737 Fortunately we had most of her pelvis preserved 222 00:19:00,799 --> 00:19:05,039 which of course is a critical part in terms of how an animal locomotes. 223 00:19:05,133 --> 00:19:09,295 For example, a quadrapedal, a four-legged chimpanzee 224 00:19:09,468 --> 00:19:15,538 - this example for example - is very different from what we see in Lucy's pelvis 225 00:19:15,710 --> 00:19:20,998 and in, in many, many respects, not identical, but in many aspects 226 00:19:21,202 --> 00:19:24,113 Lucy's pelvis reminds us of our own. 227 00:19:24,425 --> 00:19:30,793 Here is a, a pelvis of a modern human walking on two legs and the similarities are quite striking. 228 00:19:31,293 --> 00:19:36,143 No mammals, apart from humans, have ever walked on two legs 229 00:19:36,534 --> 00:19:38,850 And there was more. 230 00:19:40,790 --> 00:19:43,168 They found Lucy's footprints. 231 00:19:44,905 --> 00:19:50,052 The fossilised Laetoli footprints were discovered in Northern Tanzania in 1976. 232 00:19:50,496 --> 00:19:54,908 They are 3.6 million years old, almost the same age as Lucy, 233 00:19:55,205 --> 00:19:57,974 and were just the same size as her feet. 234 00:19:58,601 --> 00:20:05,062 They seemed to confirm that Australopithecines like Lucy had walked on two legs. 235 00:20:06,595 --> 00:20:12,790 We're looking at the soft anatomy of, of early human ancestors who walked across a volcanic ash 236 00:20:12,791 --> 00:20:15,731 and left the impression of what their feet looked like. 237 00:20:15,732 --> 00:20:19,784 We see that their feet were shaped just like ours, 238 00:20:19,988 --> 00:20:23,961 that they walked around in a manner that was almost identical to ourselves. 239 00:20:24,462 --> 00:20:30,470 If Lucy had walked on two legs then it seemed she had to have been a human ancestor 240 00:20:31,158 --> 00:20:36,932 and that's where the trouble started because Lucy's brain was just too small. 241 00:20:38,058 --> 00:20:42,642 Fortunately we had the, the, the very back portion 242 00:20:43,737 --> 00:20:48,086 of the skull preserved and you can tell from the curvature and the size 243 00:20:48,087 --> 00:20:54,016 of, of brain that would have fitted in there that it was about the size of an American softball 244 00:20:54,830 --> 00:20:59,570 which means about a, a third to a fourth the size of a modern human brain, 245 00:20:59,758 --> 00:21:05,046 so this was a creature with, with, with an ape-sized brain, very different from our own. 246 00:21:07,268 --> 00:21:09,490 There was now a huge problem. 247 00:21:09,928 --> 00:21:14,261 Only one of Lucy and 14/70 could be our ancestor. 248 00:21:14,605 --> 00:21:20,504 Both were about three million years old, but each had different characteristics unique to humans. 249 00:21:21,959 --> 00:21:27,607 If the theory was right and it really had been the development of our masterful intelligence 250 00:21:27,827 --> 00:21:34,006 that had led us to evolve from apes then that ancestor had to be the big brain 14/70, 251 00:21:34,585 --> 00:21:37,339 but now there was real doubt. 252 00:21:39,498 --> 00:21:43,034 The signal that was coming out of these fossils was, was difficult to interpret 253 00:21:43,035 --> 00:21:48,009 because on the one hand you had 14/70 with its very large brain 254 00:21:48,244 --> 00:21:53,407 and on the other hand you had Lucy with a very small brain 255 00:21:53,892 --> 00:22:00,400 but clearly bipedal and so what, what we then had was really a period of conflict. 256 00:22:01,183 --> 00:22:07,035 The only compromise, that somehow the slightly older Lucy had evolved into 14/70, 257 00:22:07,269 --> 00:22:08,740 was also ruled out. 258 00:22:09,584 --> 00:22:12,557 14/70's brain was twice the size of Lucy's. 259 00:22:12,729 --> 00:22:16,062 There was no way any creature could have doubled its brain size 260 00:22:16,171 --> 00:22:19,535 in the 400,000 years that separated them. 261 00:22:25,042 --> 00:22:28,156 The conflict was resolved brutally. 262 00:22:31,019 --> 00:22:36,401 14/70 and Lucy were dated again using radioactive dating techniques. 263 00:22:36,980 --> 00:22:39,905 Both had been found between layers of volcanic rocks 264 00:22:40,093 --> 00:22:43,707 and volcanoes produce radioactive minerals when they erupt. 265 00:22:44,286 --> 00:22:50,481 Over time these minerals decay. By working out how far this decaying process had gone 266 00:22:50,748 --> 00:22:55,504 they calculated the age of the rocks in which the fossils were found. 267 00:22:56,818 --> 00:22:59,963 The result would change everything. 268 00:23:03,717 --> 00:23:07,441 Two-legged Lucy was just over three million years old, 269 00:23:07,691 --> 00:23:12,870 but big brain 14/70 was more than a million years younger, 270 00:23:13,167 --> 00:23:18,220 less than two million years old. The Leakeys had blundered. 271 00:23:19,268 --> 00:23:24,384 The difference was such that 14/70 could be descended from Lucy 272 00:23:24,713 --> 00:23:29,579 and that means the fossil of an ape-like creature with the first key human characteristic 273 00:23:29,907 --> 00:23:32,692 was not the big brained 14/70, 274 00:23:32,865 --> 00:23:36,182 but the two-legged small brained Lucy. 275 00:23:39,033 --> 00:23:42,835 The big brain theory was now officially in the bin. 276 00:23:43,680 --> 00:23:47,137 Instead, hard though it was to believe, it was now clear 277 00:23:47,138 --> 00:23:49,985 that the first key human evolutionary development 278 00:23:50,172 --> 00:23:53,849 that had set human beings on their unique evolutionary path 279 00:23:54,052 --> 00:23:56,556 was that we had walked on two legs. 280 00:23:57,464 --> 00:24:02,236 They basically killed the old idea that the earliest ancestors would have a big brain 281 00:24:02,579 --> 00:24:09,636 because now we realised that bipedalism must have led into later ancestors with the larger brain size. 282 00:24:09,840 --> 00:24:14,658 Lucy now became the great iconic fossil, 283 00:24:14,846 --> 00:24:21,449 the creature that held the key to why human beings were so much more intelligent than all other animals, 284 00:24:22,246 --> 00:24:25,767 though it was hard to see why walking on two legs 285 00:24:26,001 --> 00:24:30,585 had somehow made us the most intelligent beings on the planet. 286 00:24:35,389 --> 00:24:39,332 Why intelligence should have evolved from moving on two legs 287 00:24:39,817 --> 00:24:44,026 doesn't seem obvious, so now a theory had to be devised 288 00:24:44,433 --> 00:24:51,270 to explain how bipedalism had let us evolve into the most amazing creature on the planet. 289 00:24:54,427 --> 00:24:57,728 We suffer from back pain, fallen arches, hernias. 290 00:24:57,807 --> 00:25:00,873 We're very slow, we're one of the slowest mammals around. 291 00:25:00,983 --> 00:25:08,414 Think about the fact that here was a little 31ft tall Lucy walking around with lots of hungry carnivores. 292 00:25:08,602 --> 00:25:14,954 . She couldn't out-run a house cat, so the advantages of bipedalism must have far outweighed the disadvantages. 293 00:25:15,893 --> 00:25:18,803 But then it all became clear to anthropologists. 294 00:25:19,194 --> 00:25:24,498 Stage one was that by standing up our front legs became hands. 295 00:25:25,234 --> 00:25:30,177 When our ancestors stood up they could begin to use their hands to carry things, 296 00:25:30,505 --> 00:25:36,466 to make new stones tools, to manipulate things, to use them in ways that, that quadrupeds don't. 297 00:25:38,704 --> 00:25:41,348 Tools led to early technology, 298 00:25:41,926 --> 00:25:47,950 technology to more ways of getting food. Better diet fed bigger brains. 299 00:25:49,718 --> 00:25:55,851 This had enormous consequences for things like social organisation and language 300 00:25:56,195 --> 00:26:00,654 and that this was then the stimulus for the development of the larger brains. 301 00:26:04,080 --> 00:26:09,102 Larger brains led to primitive culture and new ways of communicating. 302 00:26:09,477 --> 00:26:12,747 Better communication led to more complex societies, 303 00:26:12,887 --> 00:26:18,488 more complex societies to more advanced cultures and even bigger brains 304 00:26:19,020 --> 00:26:21,977 and so it went on for millions of years. 305 00:26:23,510 --> 00:26:30,206 So there were ways in which two legs could lead to mankind's ancestors developing bigger brains. 306 00:26:30,941 --> 00:26:37,231 It seemed we had evolved into the most intelligent of all animals for one simple, crucial reason: 307 00:26:37,528 --> 00:26:42,112 because millions of years ago Australopithecines like Lucy 308 00:26:42,425 --> 00:26:44,819 walked on two legs, 309 00:26:46,289 --> 00:26:49,997 but there seemed to be something even more extraordinary about Lucy, 310 00:26:50,294 --> 00:26:54,769 something so remarkable that it confirmed what many had long believed 311 00:26:55,160 --> 00:26:59,916 that in some strange evolutionary way we really were unique 312 00:27:00,510 --> 00:27:07,675 because it began to seem that Lucy's species alone of all creatures had defied the laws of evolution. 313 00:27:14,794 --> 00:27:21,991 Lucy's species should have evolved according to laws of evolution which state that major evolutionary events occur 314 00:27:22,256 --> 00:27:25,354 when there is a sudden and dramatic environmental change. 315 00:27:25,698 --> 00:27:29,140 Those who cannot adapt to the new world die, 316 00:27:36,447 --> 00:27:42,502 but some animals will have a chance mutation that may help them survive in the new environment. 317 00:27:42,847 --> 00:27:45,992 These survivors will form the basis of a new species. 318 00:27:46,274 --> 00:27:51,624 Slowly these new species will start to exploit all the different ecological niches 319 00:27:51,765 --> 00:27:53,142 in the new environment. 320 00:27:53,534 --> 00:28:00,480 Gradually these creatures will adapt to these different niches and slowly one new species will evolve into two. 321 00:28:02,566 --> 00:28:08,261 We can see how this happens where something new arises, there's a new adaptation, a slightly better way 322 00:28:08,498 --> 00:28:13,492 of getting hold of food, of avoiding a predator, of walking across a landscape 323 00:28:13,980 --> 00:28:19,262 and that then gives that population an advantage. It spreads out into new areas 324 00:28:19,566 --> 00:28:24,948 where you have one population you now have two, where you have one species you now have two species. 325 00:28:26,016 --> 00:28:28,969 This is how evolutionary family trees develop. 326 00:28:29,408 --> 00:28:32,199 Two species split to form separate branches. 327 00:28:32,287 --> 00:28:35,579 These branches can split again and then again 328 00:28:35,753 --> 00:28:39,233 and so a whole host of related species will develop. 329 00:28:40,209 --> 00:28:46,768 So what is happening is that each time you're getting proliferation of branches, you're getting divergence taking place 330 00:28:47,068 --> 00:28:52,913 and with that divergence comes what we think of as an adaptive radiation. 331 00:28:53,827 --> 00:28:58,421 Adaptive radiation is one of the fundamental truths of evolution. 332 00:28:58,947 --> 00:29:03,302 There are signs of it in virtually every type of animal that has ever lived, 333 00:29:06,080 --> 00:29:07,858 like the cat family. 334 00:29:14,441 --> 00:29:19,772 The cats are a beautiful example of an adaptive radiation because you can see what they all have in common. 335 00:29:20,023 --> 00:29:24,141 They have in common the fact that they are hunters and stalking hunters 336 00:29:24,391 --> 00:29:30,236 and they have diversified from a common ancestor into everything from lions which are very large 337 00:29:30,237 --> 00:29:36,119 to wild cats and lynxes that can live in cold environments to indeed domestic cats today 338 00:29:36,320 --> 00:29:40,237 so that they're a beautiful example of the, the shape of evolution. 339 00:29:48,422 --> 00:29:52,966 Adaptive radiation has given cats a classic evolutionary family tree, 340 00:29:53,478 --> 00:29:57,371 lots of related species coming from lots of different branches. 341 00:29:57,759 --> 00:30:02,215 It means the cat family tree has a distinctly bushy appearance 342 00:30:02,653 --> 00:30:07,897 and tracing any individual creature's line of ancestors is a complex business. 343 00:30:08,873 --> 00:30:11,965 If Lucy's species had evolved like any other animal 344 00:30:12,315 --> 00:30:15,531 her evolutionary tree should have the same bushy shape. 345 00:30:15,782 --> 00:30:20,463 There should be lots of two-legged creatures appearing just after the planet of the apes, 346 00:30:21,677 --> 00:30:28,123 but the fossil record seemed to show that the only signs of adaptive radiation came well after Lucy. 347 00:30:28,561 --> 00:30:31,827 All the fossils leading back from Lucy to the planet of the apes 348 00:30:32,103 --> 00:30:37,034 seemed to be just primitive versions of the same Australopithecine Lucy. 349 00:30:37,643 --> 00:30:42,409 It seemed that Lucy had evolved without any adaptive radiation. 350 00:30:43,943 --> 00:30:48,086 Our family tree appeared to have no related branches before Lucy at all 351 00:30:48,299 --> 00:30:53,993 but was just a solitary straight line and this defied the laws of evolution. 352 00:30:54,944 --> 00:31:00,001 One would expect to look at human evolution as an adaptive radiation, 353 00:31:00,477 --> 00:31:04,544 but the way it was always reconstructed was very much as a linear story 354 00:31:04,720 --> 00:31:08,299 and I think that actually goes back to the idea of human uniqueness. 355 00:31:08,300 --> 00:31:13,643 People expected humans to evolve differently and uniquely and have a single line. 356 00:31:16,572 --> 00:31:22,017 It seemed to many that the old idea that humans were different from all other animals 357 00:31:22,367 --> 00:31:23,306 was right. 358 00:31:26,428 --> 00:31:31,609 Every other creature had followed the typical evolutionary pattern of adaptive radiation, 359 00:31:32,073 --> 00:31:34,526 except Lucy's species. 360 00:31:36,479 --> 00:31:41,072 She alone seemed to have emerged from a single elite line of super-creatures 361 00:31:41,423 --> 00:31:45,166 so special they defied the laws of evolution. 362 00:31:56,455 --> 00:31:59,396 Then, thousands of miles from Africa, 363 00:31:59,760 --> 00:32:01,475 a chain of events began 364 00:32:01,625 --> 00:32:08,709 that would alter our whole attitude to Lucy and her species' extraordinary ability to defy the laws of evolution. 365 00:32:17,997 --> 00:32:20,313 Along came Jay Quade. 366 00:32:20,801 --> 00:32:23,267 He couldn't care less about human evolution. 367 00:32:23,893 --> 00:32:29,125 He's a geochemist, an expert in the chemical composition of rocks. 368 00:32:33,694 --> 00:32:38,150 A few years ago he was contacted by some baffled palaeontologists. 369 00:32:39,200 --> 00:32:44,845 They had noticed something strange about fossils dating from between 6-8 million years ago, 370 00:32:45,571 --> 00:32:48,012 fossils from the end of the planet of the apes. 371 00:32:48,825 --> 00:32:53,669 A whole swathe of animals, not just the apes, seemed to disappear 372 00:32:54,195 --> 00:32:56,223 and they all had one thing in common: 373 00:32:57,024 --> 00:32:59,127 they lived in the same environment. 374 00:33:01,405 --> 00:33:04,083 Starting about eight million years ago what was disappearing 375 00:33:04,233 --> 00:33:08,251 were animals that they believed were specific to a forested habitat: 376 00:33:09,001 --> 00:33:13,407 tree dwelling orang-utans, tree dwelling monkeys, forest dwelling giraffes, 377 00:33:13,632 --> 00:33:15,885 forest dwelling rodents to name a few. 378 00:33:21,767 --> 00:33:24,909 In place of the tree dwellers were new fossils, 379 00:33:25,347 --> 00:33:28,313 fossils of completely different types of animals, 380 00:33:28,639 --> 00:33:31,180 animals that lived on open plains. 381 00:33:31,768 --> 00:33:36,324 For some unknown reason there had been a radiation of new forms, 382 00:33:37,213 --> 00:33:38,540 but what had caused it? 383 00:33:39,204 --> 00:33:44,361 There was a big mystery and so it was our mission, it was our task to try and flesh out all the cause and effect here, 384 00:33:44,636 --> 00:33:49,355 try to identify the causes behind this big change, this big turnover in, in the animals. 385 00:33:53,410 --> 00:33:57,803 Quade went all over the world sampling rocks from the end of the planet of the apes 386 00:33:58,466 --> 00:34:01,257 and everywhere he found mysterious nodules, 387 00:34:01,770 --> 00:34:04,336 nodules of a substance called calcite, 388 00:34:04,737 --> 00:34:07,766 a carbon compound left by decaying plants. 389 00:34:11,679 --> 00:34:15,945 Different types of plants leave behind their own unique calcite fingerprint. 390 00:34:16,461 --> 00:34:20,916 Identify that fingerprint and you will know what vegetation have covered the world 391 00:34:21,304 --> 00:34:24,445 at the time that all these changes were happening. 392 00:34:26,435 --> 00:34:30,953 All that we require for a single analysis is it's about on, on that order 393 00:34:31,079 --> 00:34:33,607 and that to me is an amazing thing 394 00:34:34,281 --> 00:34:39,162 because you can give me a sample this size and I'll reconstruct a landscape for you. 395 00:34:45,107 --> 00:34:49,441 The ground up nodules were mixed with acid to release carbon dioxide. 396 00:34:50,755 --> 00:34:53,556 The carbon dioxide was trapped in test tubes. 397 00:34:53,916 --> 00:34:59,548 Carbon dioxide contains radioactive isotopes which are different in every type of plant. 398 00:35:01,792 --> 00:35:06,423 So identify the isotope and you identify the type of plant. 399 00:35:09,771 --> 00:35:12,368 Quade's nodules showed a clear pattern. 400 00:35:12,720 --> 00:35:17,297 They said that eight million years ago much of the world was covered in forest, 401 00:35:17,668 --> 00:35:25,002 but by six million years ago the forests had shrunk. In their place was grassland. 402 00:35:27,544 --> 00:35:30,595 Quade had stumbled upon something extraordinary. 403 00:35:31,318 --> 00:35:35,640 He realised that he was looking at one of the great changes in life on Earth. 404 00:35:36,559 --> 00:35:39,571 For some unknown reason at the end of the planet of the apes 405 00:35:39,786 --> 00:35:43,071 there had been an environmental revolution across the planet, 406 00:35:43,384 --> 00:35:47,159 the perfect conditions for dramatic evolutionary change. 407 00:35:47,609 --> 00:35:53,534 There were clear and strong hints from paleontological records for a major extinction event, 408 00:35:54,356 --> 00:36:00,360 a kind of ecologic blitzkrieg in terms of the animals that is, that really a lot of, 409 00:36:00,361 --> 00:36:03,762 lot of important animals that had roamed the landscape disappeared, completely 410 00:36:04,114 --> 00:36:07,009 disappeared in the period 8-6 million years ago. 411 00:36:12,661 --> 00:36:18,019 There had been a mass extinction. This explained the disappearance of the planet of the apes. 412 00:36:18,841 --> 00:36:25,021 As the forests were replaced by grassland all sorts of forest dwelling animals had died on a massive scale. 413 00:36:25,314 --> 00:36:31,416 In their place had come new species, ones that could adapt to the new world, the plain dwellers. 414 00:36:33,880 --> 00:36:39,649 A vast adaptive radiation had begun. It had affected every kind of animal on the planet, 415 00:36:39,962 --> 00:36:42,524 except apparently us, 416 00:36:45,301 --> 00:36:49,290 because if the theory built on Lucy was still to be believed 417 00:36:49,545 --> 00:36:54,825 then her species alone had evolved without being part of this radiation. 418 00:36:55,274 --> 00:36:59,499 They alone came from a single elite line of creatures so special 419 00:36:59,948 --> 00:37:02,862 they defied the laws of evolution. 420 00:37:05,702 --> 00:37:09,183 It was all starting to look a little bit absurd. 421 00:37:18,740 --> 00:37:24,435 No one thought the idea of our unique evolutionary path more absurd than Meave Leakey. 422 00:37:25,155 --> 00:37:27,564 Ever since the 14/70 disaster 423 00:37:27,830 --> 00:37:32,226 she had her suspicions about Lucy and the amazing story she seemed to tell. 424 00:37:32,821 --> 00:37:36,184 The news of the mass extinction and adaptive radiation 425 00:37:36,513 --> 00:37:39,329 prompted her to re-examine the whole issue. 426 00:37:41,661 --> 00:37:46,714 It's always intrigued me that we only knew about one species that was over three million years old 427 00:37:47,402 --> 00:37:51,439 because if you look at any other animal group then you'll get radiation 428 00:37:51,939 --> 00:37:53,973 and it just didn't make sense. 429 00:37:56,914 --> 00:38:03,094 So last year Meave Leakey returned to the three million year old rocks of Northern Kenya. 430 00:38:03,532 --> 00:38:05,582 She was looking for a fossil. 431 00:38:10,416 --> 00:38:13,889 It was a fossil that, in theory, should not exist 432 00:38:14,500 --> 00:38:18,005 because most people thought that 31 million years ago 433 00:38:18,381 --> 00:38:24,858 there was only one possible human ancestor, only one human-like species that walked on two legs, 434 00:38:25,313 --> 00:38:27,613 the Australopithecine Lucy. 435 00:38:31,695 --> 00:38:36,060 Find a different species of human-like biped and she would have proof 436 00:38:36,061 --> 00:38:42,663 of adaptive radiation in humans, proof that we had evolved just like other animals. 437 00:38:43,054 --> 00:38:45,244 Then one of her team spotted something. 438 00:38:46,011 --> 00:38:50,548 As I saw it I stopped and bended down and look at it, 439 00:38:53,223 --> 00:38:55,320 I couldn't say what is this? 440 00:39:00,140 --> 00:39:08,932 So I just it's this might be something good but it was behind me about 200 metres. 441 00:39:11,278 --> 00:39:15,189 When we looked and it was just a few little fragments. It didn't look particularly smart, 442 00:39:15,377 --> 00:39:19,757 but you never know and you always hope there's going to be something more under the ground 443 00:39:20,148 --> 00:39:21,463 and we were lucky. 444 00:39:22,480 --> 00:39:24,560 I became so happy. 445 00:39:26,015 --> 00:39:27,814 I went to the camp... 446 00:39:29,457 --> 00:39:32,195 I didn't eat anything, 447 00:39:32,336 --> 00:39:35,371 so it was just only joy that was in my heart. 448 00:39:37,013 --> 00:39:40,221 It was a skull so it was, you know, really exciting 449 00:39:40,534 --> 00:39:46,385 but at that point there wasn't enough of it to say whether it was the same species as Lucy or not. 450 00:39:50,577 --> 00:39:53,597 25 years after they did it for the first time, 451 00:39:53,910 --> 00:39:59,323 Meave Leakey's team assembled a skull that they believed to be about three million years old. 452 00:39:59,652 --> 00:40:02,484 This time there had to be no mistakes. 453 00:40:03,141 --> 00:40:08,179 So we spent the next year repairing all the cracks and taking all the rock off it and 454 00:40:08,554 --> 00:40:12,246 making it into the situation where we could start study, studying it 455 00:40:12,684 --> 00:40:18,739 'cos you can't study it obviously until, until it's been reconstructed and is as close as possible to its original shape. 456 00:40:25,420 --> 00:40:28,533 To help her she called in Dr Fred Spoor, 457 00:40:28,830 --> 00:40:32,507 an expert in anatomy from University College, London. 458 00:40:33,008 --> 00:40:36,231 He uses a technique called computer tomography 459 00:40:36,559 --> 00:40:39,595 to analyse the inner structure of fossil bones. 460 00:40:40,048 --> 00:40:43,646 This helps him work out how a fossil fits together. 461 00:40:45,383 --> 00:40:48,919 The first thing they noticed was the skull had a small brain, 462 00:40:49,326 --> 00:40:55,537 just like Lucy, so it clearly would not resurrect the discredited big brain theory. 463 00:40:56,459 --> 00:40:58,368 Then came a key discovery. 464 00:40:58,962 --> 00:41:02,467 It was to do with how the spine entered the head. 465 00:41:03,546 --> 00:41:07,254 In apes the spine always enters the head at the back of the skull. 466 00:41:07,676 --> 00:41:10,884 It's a typical characteristic of four-legged animals, 467 00:41:12,465 --> 00:41:17,675 but in the millions of years since the end of the planet of the apes our spines have shifted 468 00:41:17,893 --> 00:41:23,354 to enter our head underneath the skull. This helps us to walk upright. 469 00:41:24,527 --> 00:41:29,064 It's one of the reasons we walk on two legs and apes don't. 470 00:41:33,570 --> 00:41:40,344 In the new skull the hole for the spine was underneath, just like humans. 471 00:41:41,220 --> 00:41:44,866 It meant the creature must have walked on two legs, 472 00:41:45,335 --> 00:41:49,387 so it was a possible human ancestor. The question now was: 473 00:41:49,747 --> 00:41:52,547 was it just the same species as Lucy, 474 00:41:53,079 --> 00:41:59,524 the creature, the theory said, had evolved in one single line from apes, or was it something different? 475 00:42:02,153 --> 00:42:07,144 The important question that of course from day one when the, when the specimen was found 476 00:42:07,263 --> 00:42:11,127 and is always in the back of your mind even when you're cleaning is: what is it? 477 00:42:12,692 --> 00:42:14,992 Ultimately that's what we're kind of after. 478 00:42:16,135 --> 00:42:20,986 So in this case yes, we had to start comparing it 479 00:42:20,987 --> 00:42:25,241 with what we knew about other human ancestors from approximately the same period and, 480 00:42:25,242 --> 00:42:28,996 and the most obvious thing was to compare it with Lucy's kind. 481 00:42:30,827 --> 00:42:36,600 It was then that Dr Spoor made a breakthrough. It was something about the face. 482 00:42:37,537 --> 00:42:39,930 Apes have upper jaws that jut out, 483 00:42:40,149 --> 00:42:44,890 a chin that falls away and a nose that sticks out ahead of their cheekbones. 484 00:42:45,140 --> 00:42:47,784 Lucy's face was like an ape's. 485 00:42:48,535 --> 00:42:53,745 In humans the upper jaw, the nose, the chin and the cheekbones are all on the same level. 486 00:42:53,964 --> 00:43:00,739 It means our face is flat. The new skull was also flat like a human's. 487 00:43:01,989 --> 00:43:08,262 If you go from one cheekbone to the other cheekbone you can put a pen across and it's nearly, 488 00:43:09,654 --> 00:43:13,597 nearly flat, all the way here in what you call the mid-face as well. 489 00:43:14,942 --> 00:43:21,216 If you now try to do here in, in Lucy that's impossible because you have that nose coming forward so you, 490 00:43:21,874 --> 00:43:23,689 you, you balance over it. 491 00:43:24,706 --> 00:43:29,008 The difference between the new skull and Lucy was fundamental. 492 00:43:29,696 --> 00:43:31,934 They had to be different species 493 00:43:33,263 --> 00:43:41,164 and there was more. When they dated it they discovered the new skull was 31 million years old, 494 00:43:41,463 --> 00:43:44,983 almost exactly the same age as Lucy. 495 00:43:45,390 --> 00:43:48,456 It meant they had found a possible human ancestor 496 00:43:48,691 --> 00:43:51,695 that was of an entirely different species to Lucy, 497 00:43:52,101 --> 00:43:55,669 but living at exactly the same time. 498 00:43:56,463 --> 00:43:58,825 Lucy was not unique. 499 00:43:59,325 --> 00:44:04,395 Here was clear evidence of adaptive radiation in humans 500 00:44:07,211 --> 00:44:12,421 and so in February this year they announced that they had discovered flat face man, 501 00:44:12,860 --> 00:44:16,458 or as they called him Kenyanthropus platyops. 502 00:44:26,362 --> 00:44:29,851 All those theories about how unique humans are, 503 00:44:29,928 --> 00:44:32,838 that only Lucy could have made the footprints at Laetoli, 504 00:44:33,245 --> 00:44:35,560 that there had only been Lucy's species, 505 00:44:35,748 --> 00:44:39,785 that we have followed a path of evolution different from all other animals, 506 00:44:40,332 --> 00:44:42,460 they have all come tumbling down. 507 00:44:43,368 --> 00:44:45,730 We are just like any other creature. 508 00:44:46,090 --> 00:44:49,986 There is nothing different or special about human evolution. 509 00:44:50,142 --> 00:44:54,899 We are governed by the same laws of nature as everything else. 510 00:44:56,009 --> 00:45:01,954 It really questions again that, that uniqueness and in general that's, that's 511 00:45:02,470 --> 00:45:06,288 the theme in human evolution to think that everything that has to do with us is, 512 00:45:06,289 --> 00:45:11,529 is unique and is different from the evolutionary patterns that you see with other animals. 513 00:45:12,515 --> 00:45:16,254 That just holds up less and less and we turn out to be more and more 514 00:45:16,942 --> 00:45:20,635 like any other family of, of animals. 515 00:45:23,873 --> 00:45:29,349 With the announcement of Kenyanthropus this year our family tree is now being altered. 516 00:45:30,741 --> 00:45:34,919 Several two-legged creatures must have emerged from the planet of the apes. 517 00:45:35,341 --> 00:45:39,049 Among them Lucy, Kenyanthropus and who knows what else. 518 00:45:39,675 --> 00:45:42,914 Only one of these can be our direct ancestor 519 00:45:43,634 --> 00:45:45,808 and we may never know which one. 520 00:45:46,324 --> 00:45:52,520 Meave Leakey thinks it could be her discovery, Kenyanthropus, the flat face man. 521 00:45:52,958 --> 00:45:57,417 For such a long time we've believed there was just a single linear, a single ancestor. 522 00:45:57,604 --> 00:46:01,625 Now there's a choice and we may in the future have even another choice 523 00:46:01,767 --> 00:46:05,569 because I think there's another, there's also a chance that we still haven't found the common ancestor, 524 00:46:05,897 --> 00:46:07,665 but there's a good chance that this could be it. 525 00:46:09,104 --> 00:46:13,047 Could this then be the face of the earliest known human ancestor? 526 00:46:13,751 --> 00:46:19,196 We may never know because Kenyanthropus may be just one of many two-legged apes 527 00:46:19,306 --> 00:46:24,437 that emerged millions of years ago and we could have evolved from any one of them 528 00:46:24,829 --> 00:46:28,787 and so we can now tell a new story about our origins. 529 00:46:32,073 --> 00:46:36,328 It is a story not of a creature chosen above all other animals, 530 00:46:36,563 --> 00:46:40,990 but of one just like any other which evolved by chance mutation. 531 00:46:42,163 --> 00:46:46,575 it began, as evolution always does, with a chance event. 532 00:46:47,796 --> 00:46:52,223 Eight million years ago a huge environmental upheaval began. 533 00:46:52,692 --> 00:46:56,650 Forests all over the world were replaced by grassland. 534 00:46:57,527 --> 00:47:02,205 A vast adaptive radiation began creating a host of new species 535 00:47:02,471 --> 00:47:06,585 who could survive in open plains not forests. 536 00:47:07,164 --> 00:47:11,154 One of these was a breed of apes that had a chance mutation, 537 00:47:11,607 --> 00:47:14,845 apes that could walk on two legs. 538 00:47:16,175 --> 00:47:20,650 These two-legged apes would have multiplied, as did all the other new creatures 539 00:47:20,806 --> 00:47:24,373 over millions of years into many related species. 540 00:47:25,108 --> 00:47:27,878 By the time of Lucy, three million years ago, 541 00:47:28,113 --> 00:47:32,259 there were perhaps half a dozen different two-legged animals of this kind. 542 00:47:32,602 --> 00:47:36,529 Just one of these species would have been our ancestor. 543 00:47:36,967 --> 00:47:44,164 For some reason, probably just sheer chance, it survived when all the other two-legged creatures died out. 544 00:47:44,509 --> 00:47:50,345 This animal, and we do not yet know what it was, eventually became human. 545 00:47:51,268 --> 00:47:55,335 One of the things we learnt looking at the fossil record like this and, and looking back in time, 546 00:47:55,773 --> 00:48:01,812 the fact that we're here today is really very much a chance event and we were part of, of a main ecosystem, 547 00:48:01,890 --> 00:48:05,536 we were part of the evolution that was going on with, with all the other animals. 548 00:48:06,208 --> 00:48:09,275 That is the real story of our evolution. 549 00:48:09,823 --> 00:48:13,875 We were not chosen, we did not defy the laws of nature, 550 00:48:14,360 --> 00:48:17,661 we are simply the ape that got lucky.