WEBVTT 00:00:11.030 --> 00:00:12.830 One and a half million years ago 00:00:12.830 --> 00:00:17.130 there were people living in Africa. 00:00:17.130 --> 00:00:21.630 We can reconstruct exactly what they looked like. 00:00:26.070 --> 00:00:30.000 Every single one of us can trace our distant origins 00:00:30.000 --> 00:00:34.470 to people that looked like these. 00:00:34.470 --> 00:00:37.030 They too had an ancestry that goes even further 00:00:37.030 --> 00:00:39.500 back, eventually to primitive apelike 00:00:39.500 --> 00:00:44.500 creatures living in tropical forests. 00:00:47.730 --> 00:00:50.300 This is the remarkable story I'll be tracing in 00:00:50.300 --> 00:00:52.800 this series. 00:01:00.900 --> 00:01:03.570 I've been engaged for the last 15 years in a search 00:01:03.570 --> 00:01:05.600 for our ancestors. 00:01:05.600 --> 00:01:08.330 It was this quest that originally brought me to 00:01:08.330 --> 00:01:11.230 Lake Turkana, the so-called 'Jade Sea' in 00:01:11.230 --> 00:01:14.230 Northern Kenya. 00:01:19.370 --> 00:01:21.270 It was in Africa that my parents, 00:01:21.270 --> 00:01:24.530 Louis and Mary, have made many important discoveries 00:01:24.530 --> 00:01:27.030 concerning our past. 00:01:27.030 --> 00:01:29.430 Originally I didn't want to follow this family 00:01:29.430 --> 00:01:32.630 tradition; the last thing I wanted was to be a 00:01:32.630 --> 00:01:35.130 fossil hunter. 00:01:41.330 --> 00:01:43.130 Eventually however, the challenge proved too 00:01:43.130 --> 00:01:46.730 strong; I realized that, like my parents, 00:01:46.730 --> 00:01:50.530 I also wanted to know where we came from, 00:01:50.530 --> 00:01:53.530 to know what made us human. 00:01:57.770 --> 00:02:00.570 It's this curiosity which brings me and a team of 00:02:00.570 --> 00:02:03.570 colleagues here each year. 00:02:16.530 --> 00:02:18.630 The evidence we are looking for may be found 00:02:18.630 --> 00:02:20.900 in these eroded gullies and slopes around the 00:02:20.900 --> 00:02:22.770 lake. 00:02:22.770 --> 00:02:25.000 They are littered with the fossil remains of animals 00:02:25.000 --> 00:02:30.470 which lived here over the past 3 million years. 00:02:30.470 --> 00:02:34.530 Among them are clues to the origin of our species. 00:02:34.530 --> 00:02:37.430 When I discover a fossil, or somebody else finds a 00:02:37.430 --> 00:02:39.370 fossil and shows it to me, a fossil such as this, 00:02:39.370 --> 00:02:41.570 it's very, very exciting. 00:02:41.570 --> 00:02:44.130 I realize that I'm looking at something that's never 00:02:44.130 --> 00:02:46.170 been seen before by modern man. 00:02:46.170 --> 00:02:47.570 It's not just a bone to me; 00:02:47.570 --> 00:02:50.500 this is a bone of one of my ancestors but also one 00:02:50.500 --> 00:02:53.630 of your ancestors, and that to me is interesting. 00:02:53.630 --> 00:02:56.770 All of us have a natural curiosity about the early 00:02:56.770 --> 00:02:59.070 lives of our parents, our grandparents, 00:02:59.070 --> 00:03:00.770 our great-grandparents; we're all somewhat 00:03:00.770 --> 00:03:02.730 interested in history. 00:03:02.730 --> 00:03:05.200 We like to know how people lived in times before. 00:03:05.200 --> 00:03:08.400 Well by studying fossils one can in fact do that. 00:03:08.400 --> 00:03:10.630 But we're not talking about simply of hundreds 00:03:10.630 --> 00:03:12.500 of years, we're talking of hundreds of thousands of 00:03:12.500 --> 00:03:15.400 years, in fact we go back millions of years. 00:03:15.400 --> 00:03:18.430 We can, by collecting and studying fossils, 00:03:18.430 --> 00:03:21.730 tell the story of mankind almost to ten million 00:03:21.730 --> 00:03:22.970 years ago. 00:03:22.970 --> 00:03:25.730 We can determine how creatures lived that gave 00:03:25.730 --> 00:03:28.370 rise to us as a species. 00:03:28.370 --> 00:03:31.700 We can begin to understand how we as a species had 00:03:31.700 --> 00:03:34.470 become so remarkable successful on planet earth 00:03:34.470 --> 00:03:36.470 today. 00:03:43.930 --> 00:03:46.130 The earth was formed some four and a half thousand 00:03:46.130 --> 00:03:48.130 million years ago. 00:03:54.070 --> 00:03:56.600 Our success as a species may conceal the sobering 00:03:56.600 --> 00:03:59.800 fact that compared to this inconceivable length of 00:03:59.800 --> 00:04:03.370 time, we are very recent arrivals. 00:04:06.500 --> 00:04:09.170 Life itself didn't begin until about three and a 00:04:09.170 --> 00:04:11.270 half thousand million years ago when the first 00:04:11.270 --> 00:04:14.270 single-celled organisms appeared. 00:04:19.700 --> 00:04:22.630 Some 700 million years ago the first complex 00:04:22.630 --> 00:04:25.570 organisms appeared and life began to swarm in the 00:04:25.570 --> 00:04:27.570 seas. 00:04:35.330 --> 00:04:38.370 Life on land began with the amphibians about 400 00:04:38.370 --> 00:04:41.370 million years ago 00:04:45.970 --> 00:04:47.530 and the great age of the reptiles 00:04:47.530 --> 00:04:50.530 began about 300 million years ago. 00:04:54.970 --> 00:04:57.770 The first birds appeared 200 million years ago, 00:04:57.770 --> 00:05:00.830 which was also the time of the first mammals. 00:05:06.870 --> 00:05:09.000 A mere 70 million years ago we see the first 00:05:09.000 --> 00:05:12.130 primates and only 30 million years ago the 00:05:12.130 --> 00:05:15.130 common ancestor of apes and humans. 00:05:16.670 --> 00:05:19.500 The apes that evolved from that distant ancestor 00:05:19.500 --> 00:05:23.170 remain our closest living relatives. 00:05:23.170 --> 00:05:25.830 It's a remarkable fact that genetically we are 00:05:25.830 --> 00:05:28.500 closer to these chimps than say a horse is to a 00:05:28.500 --> 00:05:32.670 zebra. 00:05:32.670 --> 00:05:35.700 So how and why did our paths diverge? 00:05:35.700 --> 00:05:39.200 Why didn't we all turn out like chimpanzees? 00:05:39.200 --> 00:05:42.070 Why did they remain in the forests while our species 00:05:42.070 --> 00:05:46.070 moved out across the globe and even beyond? 00:05:56.400 --> 00:05:59.970 It's taken us millions of years to reach this point. 00:05:59.970 --> 00:06:02.130 To understand the reasons for our spectacular 00:06:02.130 --> 00:06:05.230 success we have first of all to know exactly what 00:06:05.230 --> 00:06:07.930 kind of animal we are. 00:06:07.930 --> 00:06:10.600 Our world is divided by countless different 00:06:10.600 --> 00:06:14.600 cultures, colors and races. 00:06:21.430 --> 00:06:23.630 Whenever we establish a new camp in Turkana, 00:06:23.630 --> 00:06:28.100 the local people always formally welcome us. 00:06:28.100 --> 00:06:31.100 I'm impressed most, not by the differences between 00:06:31.100 --> 00:06:35.100 us, buy by the overwhelming similarities. 00:06:42.600 --> 00:06:45.500 All of us belong to one single species, 00:06:45.500 --> 00:06:48.830 we all share a common ancestor. 00:06:48.830 --> 00:06:51.030 In searching for our origins we'll be looking 00:06:51.030 --> 00:06:54.000 for those fundamental characteristics that set 00:06:54.000 --> 00:06:57.000 us apart from all other living creatures. 00:07:02.700 --> 00:07:04.770 We are the only animal that regularly stands and 00:07:04.770 --> 00:07:08.400 walks upright. 00:07:08.400 --> 00:07:10.270 What led to this extraordinary development 00:07:10.270 --> 00:07:13.270 and when did it first happen? 00:07:17.170 --> 00:07:19.130 We are the only animal that regularly makes and 00:07:19.130 --> 00:07:22.170 uses tools and weapons. 00:07:22.170 --> 00:07:24.500 It was toolmaking that enabled us to master and 00:07:24.500 --> 00:07:28.530 manipulate our environment; 00:07:28.530 --> 00:07:30.300 how did we make this breakthrough and what was 00:07:30.300 --> 00:07:32.300 its impact? 00:07:33.170 --> 00:07:35.700 Long after tools were invented we learnt to 00:07:35.700 --> 00:07:39.700 harness fire, something no other animal does. 00:07:43.270 --> 00:07:45.700 This too was to have a profound effect on our way 00:07:45.700 --> 00:07:47.700 of life and on our environment. 00:07:54.300 --> 00:07:56.430 We developed complex social groups which were 00:07:56.430 --> 00:07:59.630 based on food sharing. 00:07:59.630 --> 00:08:02.530 I want to trace how this pattern of life developed 00:08:02.530 --> 00:08:04.970 and how it turned into the complex societies of 00:08:04.970 --> 00:08:09.970 today. 00:08:09.970 --> 00:08:12.330 And also how it helped develop that outstanding 00:08:12.330 --> 00:08:14.730 characteristic of our species, 00:08:14.730 --> 00:08:17.230 our large and complex brain. 00:08:22.030 --> 00:08:24.330 We're a species whose young remain dependent on 00:08:24.330 --> 00:08:28.000 their parents far longer than any other animal. 00:08:28.000 --> 00:08:30.170 Why this should be, and the impact it had, 00:08:30.170 --> 00:08:32.670 is also part of our story. 00:08:35.670 --> 00:08:37.900 How did we develop a complex language that is 00:08:37.900 --> 00:08:40.670 arguably most efficient communication system in 00:08:40.670 --> 00:08:44.330 the animal kingdom? 00:08:44.330 --> 00:08:46.570 The basic pattern of human life for more than a 00:08:46.570 --> 00:08:48.430 million years was that of the nomadic hunter 00:08:48.430 --> 00:08:50.200 gatherer. 00:08:50.200 --> 00:08:52.300 What caused that to change dramatically to a more 00:08:52.300 --> 00:08:55.330 settled way of life -one in which plants and 00:08:55.330 --> 00:08:58.770 animals were domesticated, a step that led directly 00:08:58.770 --> 00:09:01.330 to the world we know today? 00:09:04.330 --> 00:09:06.430 All these elements are undoubtedly a part of what 00:09:06.430 --> 00:09:10.900 made our species so successful -their origins 00:09:10.900 --> 00:09:15.830 go back an amazingly long time. 00:09:15.830 --> 00:09:18.170 These are the questions I'll try to answer in this 00:09:18.170 --> 00:09:19.270 series. 00:09:19.270 --> 00:09:22.830 Essentially what is it that makes us human? 00:09:22.830 --> 00:09:25.600 To do this we must look at much more than simply old 00:09:25.600 --> 00:09:27.700 bones. 00:09:27.700 --> 00:09:30.170 It's a story that's relevant to everybody. 00:09:30.170 --> 00:09:32.430 It's just as relevant for the people who are sent 00:09:32.430 --> 00:09:35.900 into outer space as it is to those living in the 00:09:35.900 --> 00:09:38.800 remoter parts of Africa or even us sitting in our 00:09:38.800 --> 00:09:41.600 homes watching the series. 00:09:41.600 --> 00:09:44.170 It's a story about the origin and past of a 00:09:44.170 --> 00:09:46.970 single common species. 00:09:46.970 --> 00:09:51.500 It's relevant to everybody on planet earth today. 00:09:51.500 --> 00:09:53.930 It's a story that interestingly only we can 00:09:53.930 --> 00:09:56.930 tell; we're the only animal that can look at 00:09:56.930 --> 00:10:00.570 its own past and understand it and document it. 00:10:00.570 --> 00:10:03.730 This sense of belonging to a single common species is 00:10:03.730 --> 00:10:05.130 important. 00:10:05.130 --> 00:10:07.070 I believe it's one of the most important things we 00:10:07.070 --> 00:10:09.970 can draw from our prehistoric record because 00:10:09.970 --> 00:10:12.530 today, when we face so many difficulties, 00:10:12.530 --> 00:10:16.430 I believe it's of value to face them on the basis of 00:10:16.430 --> 00:10:19.430 a single species, a single people. 00:10:25.070 --> 00:10:28.000 I want to start our story here in the African Rift 00:10:28.000 --> 00:10:30.000 Valley. 00:10:33.000 --> 00:10:35.770 It runs from Ethiopia in the north to Tanzania in 00:10:35.770 --> 00:10:37.770 the south. 00:10:46.500 --> 00:10:49.330 Along its floor are a string of lakes -remnants 00:10:49.330 --> 00:10:52.330 of larger ones that once existed here. 00:10:56.700 --> 00:10:59.270 Our ancestors lived alongside them for 00:10:59.270 --> 00:11:02.330 millions of years. 00:11:05.830 --> 00:11:08.530 They're ideal places for life and also for the 00:11:08.530 --> 00:11:11.030 preservation of a record of that life. 00:11:17.730 --> 00:11:19.470 The lakes are fed by rivers and seasonal 00:11:19.470 --> 00:11:25.500 streams created by sudden tropical storms. 00:11:25.500 --> 00:11:27.730 These streams drain off from the highlands and 00:11:27.730 --> 00:11:30.730 carry vast amounts of sand and silt. 00:11:36.770 --> 00:11:38.930 You can see on this model what happens when these 00:11:38.930 --> 00:11:42.500 rivers arrive at the lake. 00:11:42.500 --> 00:11:45.070 As the water slows the sediment is deposited on 00:11:45.070 --> 00:11:48.070 the lake bottom and also along the shore. 00:11:56.000 --> 00:12:01.430 This forms great fans or deltas -creating new land. 00:12:01.430 --> 00:12:03.930 If the lake rises, as here, 00:12:03.930 --> 00:12:06.870 a second delta is formed on top of the first. 00:12:11.900 --> 00:12:14.300 The process continues until the sediments are 00:12:14.300 --> 00:12:19.800 built up to a huge depth over a large area. 00:12:19.800 --> 00:12:22.830 This is still going on today at Turkana -the 00:12:22.830 --> 00:12:27.430 delta around this river is newly created land. 00:12:27.430 --> 00:12:29.330 And the animals that have always congregated around 00:12:29.330 --> 00:12:32.830 these lakes are inevitably caught up in the process. 00:12:40.030 --> 00:12:41.970 When an animal dies near the edge of the lake 00:12:41.970 --> 00:12:44.670 there's an excellent chance that its bones will 00:12:44.670 --> 00:12:47.370 be quickly buried and so be protected from the 00:12:47.370 --> 00:12:49.870 normal processes of decay. 00:12:56.300 --> 00:12:58.800 So this modern hippo skull will very likely become 00:12:58.800 --> 00:13:03.070 part of the future fossil record. 00:13:03.070 --> 00:13:05.430 What happens to the hippo is also what happened to 00:13:05.430 --> 00:13:11.330 the bones of our distant ancestors. 00:13:11.330 --> 00:13:13.430 When the rivers and lake flood, 00:13:13.430 --> 00:13:15.300 as they do each year, layers of sediment are 00:13:15.300 --> 00:13:20.230 deposited over the bone. 00:13:20.230 --> 00:13:23.170 Eventually this build up of sediments forces the 00:13:23.170 --> 00:13:26.970 river to change course. 00:13:26.970 --> 00:13:29.630 Its channels move back and forth over the years, 00:13:29.630 --> 00:13:33.400 dumping sediment over a wider and wider area until 00:13:33.400 --> 00:13:35.900 the whole flood plain is covered with layer upon 00:13:35.900 --> 00:13:40.800 layer of silt and sand. 00:13:40.800 --> 00:13:43.100 The hippo skull is now many feet down. 00:13:43.100 --> 00:13:47.270 The original land surface on which it lived could in 00:13:47.270 --> 00:13:49.800 some cases be covered by hundreds of feet of 00:13:49.800 --> 00:13:53.330 sediment. 00:13:53.330 --> 00:13:55.370 If the sediments are of the right chemical 00:13:55.370 --> 00:13:58.800 composition, the bone will become fossilized. 00:13:58.800 --> 00:14:01.230 That is, the organic material is replaced by 00:14:01.230 --> 00:14:05.930 minerals; the bone becomes a stone. 00:14:05.930 --> 00:14:08.800 If it remained buried below the present land 00:14:08.800 --> 00:14:10.300 surface, we would have very little chance of 00:14:10.300 --> 00:14:12.200 finding it. 00:14:12.200 --> 00:14:14.500 Luckily nature has done most of the job of 00:14:14.500 --> 00:14:17.330 excavation for us. 00:14:17.330 --> 00:14:21.130 Wind and rain erode away the surface. 00:14:21.130 --> 00:14:24.600 Streams cut back through the sedimentary layers 00:14:24.600 --> 00:14:28.400 exposing the various levels. 00:14:28.400 --> 00:14:30.200 The whole landscape is scoured and gouged by 00:14:30.200 --> 00:14:35.130 these natural forces. 00:14:35.130 --> 00:14:37.830 The fossils are found literally eroding out on 00:14:37.830 --> 00:14:42.430 the surface. 00:14:42.430 --> 00:14:45.330 Torrential rain brings surface water rushing down 00:14:45.330 --> 00:14:47.500 the slopes and this rapidly exposes long 00:14:47.500 --> 00:14:50.000 buried fossils. 00:15:09.470 --> 00:15:11.070 Within a short period of time, 00:15:11.070 --> 00:15:13.570 however, the fossil bone could be reburied or 00:15:13.570 --> 00:15:18.500 broken up and the fragments scattered. 00:15:18.500 --> 00:15:20.030 You have to be in the right place at the right 00:15:20.030 --> 00:15:23.030 time to find the best fossils. 00:15:31.070 --> 00:15:36.370 I came to the right place almost by chance. 00:15:36.370 --> 00:15:39.900 In 1967 I was flying up to the Omo Valley at the 00:15:39.900 --> 00:15:41.970 North end of Lake Turkana. 00:15:41.970 --> 00:15:44.430 I presume my pilot wasn't paying attention like I'm 00:15:44.430 --> 00:15:46.670 not at the moment, he was on autopilot, 00:15:46.670 --> 00:15:49.700 and we flew over the eastern side of this lake 00:15:49.700 --> 00:15:51.770 for the first time. 00:15:51.770 --> 00:15:54.830 And it was then that I saw these fabulous sediments, 00:15:54.830 --> 00:15:57.700 these deposits that were laid down here millions of 00:15:57.700 --> 00:15:59.200 years ago. 00:15:59.200 --> 00:16:01.570 Before that time nobody had suspected that there 00:16:01.570 --> 00:16:04.770 were sediments in this part of the world. 00:16:04.770 --> 00:16:06.670 You can see how the deposits have stratified 00:16:06.670 --> 00:16:09.930 and the volcanic ashes interbedded with them, 00:16:09.930 --> 00:16:12.330 you get an impression of a vast lake. 00:16:12.330 --> 00:16:14.930 And it was to that area that I came in 1968 to 00:16:14.930 --> 00:16:17.670 look for fossils and where since we've been finding 00:16:17.670 --> 00:16:20.630 so many hundreds of different animals embedded 00:16:20.630 --> 00:16:24.000 in these rocks. 00:16:24.000 --> 00:16:26.670 During the field season we go out every day to search 00:16:26.670 --> 00:16:30.130 these exposed sediments. 00:16:30.130 --> 00:16:32.670 It's exhausting work with temperatures often over 00:16:32.670 --> 00:16:36.130 100 degrees. 00:16:36.130 --> 00:16:38.370 Snakes, scorpions and the occasional lion add 00:16:38.370 --> 00:16:42.770 interest to our work. 00:16:42.770 --> 00:16:45.530 Most of the fossils have been found by a team of 00:16:45.530 --> 00:16:48.100 Kenyans who have an extraordinary skill at 00:16:48.100 --> 00:16:50.930 spotting significant finds amongst this jumble of 00:16:50.930 --> 00:16:53.430 rocks. 00:16:57.530 --> 00:16:59.830 When you find a fossil you have first to determine 00:16:59.830 --> 00:17:04.100 how old it is. 00:17:04.100 --> 00:17:07.500 You can't date the bone by its Carbon 14 content as 00:17:07.500 --> 00:17:11.800 all the carbon has long since disappeared. 00:17:11.800 --> 00:17:14.570 What we attempt to do is date the rocks or 00:17:14.570 --> 00:17:16.930 sediments in which it's found. 00:17:16.930 --> 00:17:19.370 One of the best ways for doing this is to date 00:17:19.370 --> 00:17:22.870 volcanic materials that are laid down in the same 00:17:22.870 --> 00:17:25.630 sequence as this bone. 00:17:25.630 --> 00:17:28.100 In this particular area and in other areas of 00:17:28.100 --> 00:17:30.300 Africa there are sites where there are volcanic 00:17:30.300 --> 00:17:32.900 ashes or volcanic tuffs as they're called. 00:17:32.900 --> 00:17:34.970 Those can be dated. 00:17:34.970 --> 00:17:36.970 We have one just above this hippo which would 00:17:36.970 --> 00:17:38.970 give us a very good indication of the age of 00:17:38.970 --> 00:17:41.970 this specimen. 00:17:58.400 --> 00:18:00.730 Those ancient volcanoes that erupted round Lake 00:18:00.730 --> 00:18:03.470 Turkana were similar to the recent eruption at 00:18:03.470 --> 00:18:07.070 Mount St. Helens in North America. 00:18:07.070 --> 00:18:09.170 That is, they were primarily volcanoes that 00:18:09.170 --> 00:18:12.800 threw out millions of tons of ash rather than red hot 00:18:12.800 --> 00:18:14.800 lava. 00:18:21.500 --> 00:18:23.730 This ash can cover the landscape to a depth of 00:18:23.730 --> 00:18:25.730 many feet. 00:18:30.830 --> 00:18:33.230 Certain minerals in the ash contain specific 00:18:33.230 --> 00:18:35.870 isotopes of potassium which immediately after 00:18:35.870 --> 00:18:39.600 eruption begin to decay very slowly into isotopes 00:18:39.600 --> 00:18:41.700 of argon. 00:18:41.700 --> 00:18:45.030 This decay happens at a known constant rate. 00:18:45.030 --> 00:18:47.400 By measuring how much potassium has turned to 00:18:47.400 --> 00:18:50.370 argon we can determine how long the ash has been 00:18:50.370 --> 00:18:51.900 there. 00:18:51.900 --> 00:18:56.470 The ash has a built in atomic clock as it were. 00:18:56.470 --> 00:18:59.130 Major eruptions are often separated by long 00:18:59.130 --> 00:19:03.700 intervals of time when life returns to normal. 00:19:07.570 --> 00:19:09.870 In many Rift Valley sites there are numbers of ash 00:19:09.870 --> 00:19:12.430 layers separating sediments which contain 00:19:12.430 --> 00:19:14.230 the fossils. 00:19:14.230 --> 00:19:17.130 So fossils can be dated by their position in this 00:19:17.130 --> 00:19:19.630 volcanic sandwich. 00:19:22.200 --> 00:19:24.470 When you find fragments of bone washing out of these 00:19:24.470 --> 00:19:27.830 exposed areas of sediments it's not magic to identify 00:19:27.830 --> 00:19:29.130 them. 00:19:29.130 --> 00:19:31.130 It's remarkably easy to tell the difference 00:19:31.130 --> 00:19:34.330 between the various sorts of animals and indeed the 00:19:34.330 --> 00:19:36.630 difference between the different parts of the 00:19:36.630 --> 00:19:38.470 skeleton within the various groups of animals. 00:19:38.470 --> 00:19:42.200 Distinguishing between different pieces of bones 00:19:42.200 --> 00:19:43.970 is rather like distinguishing between 00:19:43.970 --> 00:19:46.300 broken crockery. 00:19:46.300 --> 00:19:48.600 Anyone can tell the difference between a 00:19:48.600 --> 00:19:51.030 plate, a cup, a saucer and a bowl. 00:19:51.030 --> 00:19:52.700 But if you break that crockery, 00:19:52.700 --> 00:19:54.070 break it into individual pieces, 00:19:54.070 --> 00:19:55.870 it becomes much more difficult. 00:19:55.870 --> 00:19:58.330 And yet even there it's possible. 00:19:58.330 --> 00:20:00.500 With fragments of bone it's certainly possible 00:20:00.500 --> 00:20:02.270 and from those fragments one can learn a tremendous 00:20:02.270 --> 00:20:06.000 amount about the animals that the bones belong to. 00:20:06.000 --> 00:20:09.930 Bones from the same part of any animal always look 00:20:09.930 --> 00:20:11.330 quite similar. 00:20:11.330 --> 00:20:13.670 For example a baboon's thigh bone and that of a 00:20:13.670 --> 00:20:16.530 gazelle are the same basic shape in spite of their 00:20:16.530 --> 00:20:18.900 size difference. 00:20:18.900 --> 00:20:20.870 Teeth can tell you even more. 00:20:20.870 --> 00:20:22.630 The large flat molars of the bear, 00:20:22.630 --> 00:20:24.670 for example, are specialized for eating 00:20:24.670 --> 00:20:26.770 vegetation. 00:20:26.770 --> 00:20:29.970 In contrast a hyena has teeth designed for 00:20:29.970 --> 00:20:32.930 crushing and tearing flesh like that of a leopard. 00:20:32.930 --> 00:20:37.070 Fossil teeth can be easily matched to the nearest 00:20:37.070 --> 00:20:41.200 living counterpart. 00:20:41.200 --> 00:20:43.770 This is a sabre-toothed cat and clearly it was 00:20:43.770 --> 00:20:47.400 eating the same sort of thing as the leopard. 00:20:47.400 --> 00:20:49.700 Even though it is long extinct we can tell 00:20:49.700 --> 00:20:54.530 something of the life it was leading from its diet. 00:20:57.970 --> 00:20:59.670 The fossils that give me the greatest excitement 00:20:59.670 --> 00:21:02.730 are those belonging to our ancestors. 00:21:21.500 --> 00:21:23.700 When we find a human fossil everyone's drafted 00:21:23.700 --> 00:21:26.800 in to search for more. 00:21:26.800 --> 00:21:29.170 This is a fragment of upper jaw it probably 00:21:29.170 --> 00:21:31.370 belong to the same individual as the skull 00:21:31.370 --> 00:21:33.430 fragment. 00:21:33.430 --> 00:21:37.430 It's one and a half million years old. 00:21:41.370 --> 00:21:43.430 Everything we find is eventually brought back 00:21:43.430 --> 00:21:46.430 here to our base camp at Koobi Fora on the shores 00:21:46.430 --> 00:21:48.430 of the lake. 00:21:57.830 --> 00:22:00.230 It is here that we usually make the first examination 00:22:00.230 --> 00:22:01.200 of the fossils. 00:22:01.200 --> 00:22:03.030 (Woman) That's how it should go. 00:22:03.030 --> 00:22:07.030 Look you can see the impression on the stern ... 00:22:07.030 --> 00:22:12.570 (Man) It seems to have died with its mouth open. 00:22:12.570 --> 00:22:15.730 (Man) Where's yesterday's things? 00:22:15.730 --> 00:22:18.500 (Narrator) Many specimens are incomplete. 00:22:18.500 --> 00:22:20.400 It's a kind of jigsaw puzzle with, 00:22:20.400 --> 00:22:24.200 unfortunately, most of the pieces missing. 00:22:24.200 --> 00:22:26.870 If we're lucky we can reassemble the scattered 00:22:26.870 --> 00:22:31.200 fragments -but we do find more complete specimens. 00:22:31.200 --> 00:22:33.470 We've now got remains of over two hundred individuals 00:22:33.470 --> 00:22:37.000 represented by almost all parts of the skeleton 00:22:37.000 --> 00:22:40.130 including various limb bones as well as jaws and 00:22:40.130 --> 00:22:42.600 teeth. 00:22:42.600 --> 00:22:45.600 The most important of all are the complete skulls. 00:22:45.600 --> 00:22:47.830 But these bones are just the beginning. 00:22:47.830 --> 00:22:51.630 You can take the skull and you can set it against 00:22:51.630 --> 00:22:54.000 where it was found and the geologist can tell you a 00:22:54.000 --> 00:22:55.730 great deal about the environment in which that 00:22:55.730 --> 00:22:57.170 individual lived. 00:22:57.170 --> 00:22:59.700 The paleobotanist can tell you about the plants that 00:22:59.700 --> 00:23:01.470 were growing there at the time by studying the 00:23:01.470 --> 00:23:02.800 pollen. 00:23:02.800 --> 00:23:04.400 The automist can take the skull, 00:23:04.400 --> 00:23:06.400 or part of the skeleton, and by looking at the 00:23:06.400 --> 00:23:09.000 markings on the skull can put back the flesh, 00:23:09.000 --> 00:23:12.070 and by putting back the flesh we can begin to get 00:23:12.070 --> 00:23:14.170 some idea of the soft tissues as well as the 00:23:14.170 --> 00:23:15.230 hard tissues. 00:23:15.230 --> 00:23:17.400 And through this we get a very precise picture of 00:23:17.400 --> 00:23:21.970 what the individual actually looked like. 00:23:21.970 --> 00:23:24.330 This, for example, is what we think one of our 00:23:24.330 --> 00:23:26.930 ancestors -Homo erectus -might have looked like. 00:23:26.930 --> 00:23:33.300 The appearance we can deduce from the skeleton. 00:23:33.300 --> 00:23:35.770 The tools and bone refuse he left behind are a good 00:23:35.770 --> 00:23:39.830 clue to behaviour. 00:23:39.830 --> 00:23:41.730 The central question is how did such creatures 00:23:41.730 --> 00:23:44.800 evolve into us? 00:23:44.800 --> 00:23:46.830 The fossil record is a record of change. 00:23:46.830 --> 00:23:51.170 We can document the stages by which one form changes 00:23:51.170 --> 00:23:53.530 into another. 00:23:53.530 --> 00:23:56.230 The process by which this happens is fundamental to 00:23:56.230 --> 00:23:57.900 our story. 00:23:57.900 --> 00:24:00.170 It's been known as 'natural selection' ever 00:24:00.170 --> 00:24:03.670 since the days of Charles Darwin. 00:24:03.670 --> 00:24:06.900 His "Origin of Species" was published in 1859 when 00:24:06.900 --> 00:24:10.000 the popular view was that all animal species were 00:24:10.000 --> 00:24:12.870 unchanging; being the result of an act of divine 00:24:12.870 --> 00:24:14.630 creation. 00:24:14.630 --> 00:24:17.230 Darwin proposed that animals had changed and 00:24:17.230 --> 00:24:20.430 offered a mechanism to explain this. 00:24:20.430 --> 00:24:23.870 I think Darwin's greatest insight was almost 00:24:23.870 --> 00:24:26.170 certainly his recognition of the fundamental 00:24:26.170 --> 00:24:29.300 importance of individual variation within a 00:24:29.300 --> 00:24:32.770 species, and his idea that nature worked on this 00:24:32.770 --> 00:24:35.670 variation to produce gradual change in that 00:24:35.670 --> 00:24:37.100 species. 00:24:37.100 --> 00:24:39.900 Indeed he wrote in "Origin of Species" on this very 00:24:39.900 --> 00:24:41.800 point. 00:24:41.800 --> 00:24:45.270 "If variations useful to any organic being do ever 00:24:45.270 --> 00:24:47.570 occur, assuredly individuals thus 00:24:47.570 --> 00:24:49.900 characterized will have the best chance of being 00:24:49.900 --> 00:24:52.170 preserved in the struggle for life. 00:24:52.170 --> 00:24:53.700 And from the strong principle of inheritance 00:24:53.700 --> 00:24:56.600 they will tend to produce offspring similarly 00:24:56.600 --> 00:24:58.700 characterized. 00:24:58.700 --> 00:25:00.070 This principle of preservation, 00:25:00.070 --> 00:25:01.570 or the survival of the fittest, 00:25:01.570 --> 00:25:04.830 I have called natural selection. 00:25:04.830 --> 00:25:06.230 It leads to the improvement of each 00:25:06.230 --> 00:25:11.670 creature in relation to its conditions of life". 00:25:11.670 --> 00:25:12.830 All animals are in competition for the 00:25:12.830 --> 00:25:14.670 resources of their habitat. 00:25:14.670 --> 00:25:18.770 Natural selection ensures that traits that give 00:25:18.770 --> 00:25:20.900 animals an advantage in this competition will be 00:25:20.900 --> 00:25:24.070 selected for -whether it be a faster turn of speed, 00:25:24.070 --> 00:25:29.130 keener eyesight or hearing. 00:25:29.130 --> 00:25:31.330 A strong zebra that can chase off rival males 00:25:31.330 --> 00:25:33.770 stands a better chance of getting more mates and so 00:25:33.770 --> 00:25:36.770 having more offspring. 00:25:45.230 --> 00:25:47.800 Natural selection leads to animals becoming adapted 00:25:47.800 --> 00:25:49.900 to certain niches. 00:25:49.900 --> 00:25:52.200 The giraffe's long neck is not there because 00:25:52.200 --> 00:25:54.770 ancestral giraffes stretched to reach the 00:25:54.770 --> 00:25:57.370 tops of trees on which they fed. 00:25:57.370 --> 00:25:58.930 It's there because in the past, 00:25:58.930 --> 00:26:01.600 taller giraffes could feed off bushes and trees at a 00:26:01.600 --> 00:26:03.900 height shorter animals couldn't reach. 00:26:03.900 --> 00:26:08.070 So the taller ones had less competition, 00:26:08.070 --> 00:26:10.700 got more food and were better able to survive and 00:26:10.700 --> 00:26:14.330 reproduce producing more successful long-necked 00:26:14.330 --> 00:26:17.500 giraffes. 00:26:17.500 --> 00:26:19.800 A gerenuk gives us another example of natural 00:26:19.800 --> 00:26:22.170 selection. 00:26:22.170 --> 00:26:24.470 It has evolved a peculiar method of feeding. 00:26:24.470 --> 00:26:29.400 This gives the gerenuk access to a food source 00:26:29.400 --> 00:26:33.070 that other antelopes can't reach -so it would have 00:26:33.070 --> 00:26:36.270 been selected for. 00:26:36.270 --> 00:26:38.300 How long does it take for these adaptations and 00:26:38.300 --> 00:26:42.300 changes to produce totally new species? 00:26:42.300 --> 00:26:44.130 One of the foremost advocates of a new 00:26:44.130 --> 00:26:46.600 explanation of evolutionary change is 00:26:46.600 --> 00:26:49.270 Professor Stephen J. Gould. 00:26:49.270 --> 00:26:51.730 (Gould) Traditionally the view among evolutionists has 00:26:51.730 --> 00:26:55.900 been that the process is in its essence a slow, 00:26:55.900 --> 00:26:58.730 steady, gradual one, proceeding step by 00:26:58.730 --> 00:27:02.330 imperceptible step, linking ancestor and 00:27:02.330 --> 00:27:04.670 descendant through all possible degrees of 00:27:04.670 --> 00:27:06.100 interediary forms. 00:27:06.100 --> 00:27:08.070 That was Darwin's belief, it was one of the 00:27:08.070 --> 00:27:10.430 controlling beliefs of his system. 00:27:10.430 --> 00:27:12.770 And yet as Huxley pointed out to Darwin in 00:27:12.770 --> 00:27:15.700 criticizing what he didn't agree with in Darwin's 00:27:15.700 --> 00:27:17.970 "Origin" is nothing about the theory of natural 00:27:17.970 --> 00:27:20.870 selection that requires this kind of imperceptible 00:27:20.870 --> 00:27:22.070 gradualism. 00:27:22.070 --> 00:27:23.670 And Huxley said "Look Darwin, 00:27:23.670 --> 00:27:25.130 you're going to be in enough trouble anyway 00:27:25.130 --> 00:27:27.200 trying to convince people about evolution, 00:27:27.200 --> 00:27:28.530 not to mention natural selection, 00:27:28.530 --> 00:27:31.230 why are you tying it to this unnecessary, 00:27:31.230 --> 00:27:33.470 and by the way false, belief in the absolutely 00:27:33.470 --> 00:27:36.200 gradual nature of change?" 00:27:36.200 --> 00:27:39.100 Huxley believed that change could occur in 00:27:39.100 --> 00:27:43.800 leaps and starts and I believe that's probably so. 00:27:43.800 --> 00:27:47.370 The main reason being that evolutionists hold that 00:27:47.370 --> 00:27:50.530 very large populations have a great deal of 00:27:50.530 --> 00:27:53.600 inertia against substantial evolutionary 00:27:53.600 --> 00:27:55.370 change, in the whole population, 00:27:55.370 --> 00:27:57.700 if only because it takes favorable mutations so 00:27:57.700 --> 00:28:00.830 long to spread through and because you need to get so 00:28:00.830 --> 00:28:03.830 many favorable mutations fixed before you have a 00:28:03.830 --> 00:28:04.770 new form. 00:28:04.770 --> 00:28:07.570 And therefore most biologists would hold that 00:28:07.570 --> 00:28:11.000 evolution or the chance of successful and extensive 00:28:11.000 --> 00:28:14.670 evolution, is maximized in very small populations 00:28:14.670 --> 00:28:18.130 where mutations have a chance of spreading and 00:28:18.130 --> 00:28:21.870 becoming fixed with some reasonable speed. 00:28:21.870 --> 00:28:24.070 And therefore most biologists believe that 00:28:24.070 --> 00:28:27.400 speciation can occur primarily when tiny 00:28:27.400 --> 00:28:31.270 numbers of individuals get isolated from the parental 00:28:31.270 --> 00:28:34.730 form and can follow their own evolutionary 00:28:34.730 --> 00:28:36.730 direction. 00:28:39.670 --> 00:28:42.470 (Narrator) So evolution may not be a gradual process, 00:28:42.470 --> 00:28:45.400 but one punctuated by sudden leaps or periods of 00:28:45.400 --> 00:28:48.530 rapid change, followed by long periods when animals 00:28:48.530 --> 00:28:51.600 don't change. 00:28:51.600 --> 00:28:54.000 Our story is no different from that of other 00:28:54.000 --> 00:28:56.700 animals, but this presents us with a problem. 00:28:56.700 --> 00:29:02.070 If speciation occurs rapidly and occurs in 00:29:02.070 --> 00:29:05.230 small populations, it's perfectly reasonable when 00:29:05.230 --> 00:29:07.670 you consider the difficulties of fossils 00:29:07.670 --> 00:29:09.500 being preserved and then being found, 00:29:09.500 --> 00:29:11.900 that we're going to seldom find the so-called 00:29:11.900 --> 00:29:15.600 'missing links', the examples of a species in 00:29:15.600 --> 00:29:17.530 transition. 00:29:17.530 --> 00:29:19.400 Nevertheless, having said that, 00:29:19.400 --> 00:29:21.700 I think it's fair to say that when we do find a 00:29:21.700 --> 00:29:24.500 fossil, the fossil is almost certainly going to 00:29:24.500 --> 00:29:28.030 be representative in a very real sense of the 00:29:28.030 --> 00:29:31.070 stage of the population that it comes from. 00:29:31.070 --> 00:29:33.430 It's most unlikely that a fossil will be 00:29:33.430 --> 00:29:35.730 representative of a freak. 00:29:35.730 --> 00:29:38.300 The mathematical probability of finding a 00:29:38.300 --> 00:29:41.530 freak is so extraordinary as to be very difficult to 00:29:41.530 --> 00:29:43.900 consider. 00:29:43.900 --> 00:29:48.570 When one is fortunate and finds a population that is 00:29:48.570 --> 00:29:53.330 well represented in terms of numbers and is found in 00:29:53.330 --> 00:29:55.800 a situation where you can trace it over long periods 00:29:55.800 --> 00:29:58.700 of time, then you do have a chance of actually 00:29:58.700 --> 00:30:01.430 locating one of these 'missing links' or 00:30:01.430 --> 00:30:06.030 changing populations. 00:30:06.030 --> 00:30:08.270 Just one example would prove the case. 00:30:08.270 --> 00:30:11.500 At Lake Turkana that example turned up amongst 00:30:11.500 --> 00:30:14.500 the fossil shells that litter these deposits. 00:30:18.830 --> 00:30:21.570 The various fossil species of snails from Turkana 00:30:21.570 --> 00:30:24.300 have been studied by one of my colleagues, 00:30:24.300 --> 00:30:26.730 Dr. Peter Williamson. 00:30:26.730 --> 00:30:29.830 In one case the parent species which had existed 00:30:29.830 --> 00:30:33.100 successfully for years looked like this -the 00:30:33.100 --> 00:30:36.200 edges of the spiral are gently curved. 00:30:36.200 --> 00:30:38.970 In the same lake, some hundreds of thousands of 00:30:38.970 --> 00:30:44.170 years later, the same snails looked like this. 00:30:44.170 --> 00:30:46.500 They have sharp, angled edges. 00:30:46.500 --> 00:30:49.400 What Peter found is the link between the two, 00:30:49.400 --> 00:30:50.970 and here they are. 00:30:50.970 --> 00:30:54.670 A population where some shells look like the 00:30:54.670 --> 00:30:56.700 parent, others like the daughter. 00:30:56.700 --> 00:31:00.770 It is a group sampled in the act of evolving from 00:31:00.770 --> 00:31:04.770 one form to another in a very short period of time. 00:31:09.230 --> 00:31:11.430 They are our best proof that so-called 'missing 00:31:11.430 --> 00:31:16.570 links' really exist. 00:31:16.570 --> 00:31:20.030 I find it very strange that today many people 00:31:20.030 --> 00:31:23.330 still think of evolution as just a theory. 00:31:23.330 --> 00:31:25.800 I'm convinced, and I think many others are as well, 00:31:25.800 --> 00:31:28.100 that there's sufficient evidence to demonstrate 00:31:28.100 --> 00:31:30.070 evolution as a fact. 00:31:30.070 --> 00:31:32.170 The process of natural selection works, 00:31:32.170 --> 00:31:34.530 it has worked in countless incidences that can be 00:31:34.530 --> 00:31:36.500 well documented. 00:31:36.500 --> 00:31:39.130 I also am puzzled, and indeed I find it very 00:31:39.130 --> 00:31:41.700 arrogant, that many people think that if evolution 00:31:41.700 --> 00:31:45.070 occurred, it occurred because we were to be 00:31:45.070 --> 00:31:46.400 produced -that we are the end product, 00:31:46.400 --> 00:31:50.600 the inevitable end product of natural selection. 00:31:50.600 --> 00:31:52.370 Nothing could be further from the truth. 00:31:52.370 --> 00:31:56.200 We are here as a result of a series of accidents if 00:31:56.200 --> 00:31:57.070 you like. 00:31:57.070 --> 00:32:00.530 There was nothing preplanned about humanity. 00:32:00.530 --> 00:32:03.400 One can demonstrate that if certain events hadn't 00:32:03.400 --> 00:32:04.900 happened we wouldn't be here today. 00:32:04.900 --> 00:32:08.400 But we do have fossils that demonstrate the 00:32:08.400 --> 00:32:10.330 process by which we arrived, 00:32:10.330 --> 00:32:12.830 we can document the transformation of an 00:32:12.830 --> 00:32:16.730 apelike creature through a series of steps to what we 00:32:16.730 --> 00:32:20.730 are today -fully modern human beings. 00:32:23.300 --> 00:32:25.870 Our story begins in the forest. 00:32:25.870 --> 00:32:28.370 It was here that our primate ancestors evolved 00:32:28.370 --> 00:32:30.500 some of the crucial characteristics that we 00:32:30.500 --> 00:32:35.870 share with all primates today. 00:32:35.870 --> 00:32:38.070 The first primate was probably not unlike a 00:32:38.070 --> 00:32:40.000 modern mouse lemur. 00:32:40.000 --> 00:32:41.400 To live and move safely in the trees, 00:32:41.400 --> 00:32:44.870 grasping hands and stereoscopic vision were 00:32:44.870 --> 00:32:47.000 crucial and we have inherited these same 00:32:47.000 --> 00:32:49.500 traits. 00:32:50.170 --> 00:32:53.270 The ring-tailed lemur is a good model for another 00:32:53.270 --> 00:32:56.100 important stage in our development. 00:32:56.100 --> 00:32:57.700 Increasing coordination of eyes, 00:32:57.700 --> 00:32:59.930 hands and brain represented a further 00:32:59.930 --> 00:33:03.000 specialization for life in the trees. 00:33:06.430 --> 00:33:08.470 From this stage one evolutionary 00:33:08.470 --> 00:33:10.630 path led to the monkeys like the colobus, 00:33:10.630 --> 00:33:14.630 animals that are even more at home in the trees. 00:33:29.400 --> 00:33:31.200 When monkeys move around in the trees and on the 00:33:31.200 --> 00:33:33.070 ground, like these baboons, 00:33:33.070 --> 00:33:34.970 they walk on all fours with their trunk 00:33:34.970 --> 00:33:36.770 horizontal. 00:33:36.770 --> 00:33:39.770 This is an unlikely model for our early ancestors. 00:33:43.330 --> 00:33:46.830 It is quite different from the way the apes move. 00:33:46.830 --> 00:33:48.900 These animals move through the trees by swinging 00:33:48.900 --> 00:33:52.830 below branches keeping their trunks upright. 00:33:52.830 --> 00:33:54.800 It's an adaptation seen in its most extreme and 00:33:54.800 --> 00:33:57.800 spectacular form in the gibbon. 00:34:24.200 --> 00:34:26.130 I am certainly not proposing that our 00:34:26.130 --> 00:34:29.370 ancestors move through the trees like a gibbon. 00:34:29.370 --> 00:34:31.630 The more generalized pattern of our closest 00:34:31.630 --> 00:34:34.630 relative the chimp is a better model. 00:34:36.930 --> 00:34:39.870 This animals moves through the trees on all fours or 00:34:39.870 --> 00:34:42.370 by swinging below branches. 00:34:47.670 --> 00:34:50.970 On the ground it also moved on all fours but 00:34:50.970 --> 00:34:58.470 occasionally it will walk on two legs. 00:34:58.470 --> 00:35:00.800 Of course we are not descended from any of the 00:35:00.800 --> 00:35:02.430 modern apes. 00:35:02.430 --> 00:35:03.870 They are the product of millions of years of 00:35:03.870 --> 00:35:06.970 separate evolution, just as we are. 00:35:06.970 --> 00:35:09.470 But we are so close to the chimpanzee genetically 00:35:09.470 --> 00:35:11.630 that there can be no doubt that we share a common 00:35:11.630 --> 00:35:13.870 ancestor. 00:35:13.870 --> 00:35:17.870 So when and why did our paths diverge? 00:35:22.270 --> 00:35:24.800 Imagine that we could go back in time twenty million 00:35:24.800 --> 00:35:26.300 years. 00:35:29.670 --> 00:35:32.230 At that time tropical rain forests covered much of 00:35:32.230 --> 00:35:36.630 the Old World. 00:35:36.630 --> 00:35:39.630 They were filled with primitive apes. 00:35:39.630 --> 00:35:41.500 They had the place to themselves, 00:35:41.500 --> 00:35:44.330 filling the niches that are today occupied by 00:35:44.330 --> 00:35:47.430 monkeys. 00:35:47.430 --> 00:35:49.870 These apes were the Dryopithecines 00:35:49.870 --> 00:35:53.930 and we have found many of their fossils. 00:35:53.930 --> 00:35:55.800 Their teeth were designed to deal with the 00:35:55.800 --> 00:35:58.170 vegetation of the forest -plants, 00:35:58.170 --> 00:36:02.730 leaves, fruits, like modern monkeys and apes. 00:36:05.530 --> 00:36:08.230 From their skulls and limb bones we can deduce what 00:36:08.230 --> 00:36:13.770 they looked like. 00:36:13.770 --> 00:36:16.600 It was an apelike animal but one that moved on all 00:36:16.600 --> 00:36:19.730 fours like a monkey. 00:36:19.730 --> 00:36:23.000 The Dryopithecines were well adapted to the forest 00:36:23.000 --> 00:36:25.170 existence. 00:36:25.170 --> 00:36:27.030 Then some fifteen million years ago, 00:36:27.030 --> 00:36:30.230 the world climate began to get cooler and more 00:36:30.230 --> 00:36:33.300 seasonal weather resulted. 00:36:33.300 --> 00:36:35.800 One effect was that these great forests began to 00:36:35.800 --> 00:36:38.900 shrink, giving way to more open woodland and 00:36:38.900 --> 00:36:40.900 grasslands. 00:36:43.930 --> 00:36:46.500 It's about at this time that we begin to see in 00:36:46.500 --> 00:36:48.770 the fossil record the first evidence of a number 00:36:48.770 --> 00:36:50.800 of different species adapting to the open 00:36:50.800 --> 00:36:52.030 country. 00:36:52.030 --> 00:36:54.500 We begin to get the early pigs moving out into the 00:36:54.500 --> 00:36:56.300 grasslands, the early horses, 00:36:56.300 --> 00:36:58.630 the early antelopes and there seems to be a 00:36:58.630 --> 00:37:01.100 general trend towards adapting to this open 00:37:01.100 --> 00:37:02.830 savannah country that seems to have been 00:37:02.830 --> 00:37:05.530 developing right across the world in what we now 00:37:05.530 --> 00:37:06.870 know as the Old World, that is Africa and 00:37:06.870 --> 00:37:09.570 Southern Europe and Asia. 00:37:09.570 --> 00:37:11.730 The primates also responded to this new 00:37:11.730 --> 00:37:14.000 habitat, new environment that was being developed 00:37:14.000 --> 00:37:16.530 and amongst the primates that so adapted were a 00:37:16.530 --> 00:37:19.270 group that undoubtedly came from the 00:37:19.270 --> 00:37:20.330 Dryopithecines. 00:37:20.330 --> 00:37:22.300 It is this group, the Ramapithecines, 00:37:22.300 --> 00:37:25.130 that we believe we can trace the human story to. 00:37:25.130 --> 00:37:27.570 What is very interesting is that one of the major 00:37:27.570 --> 00:37:29.730 collections of these fossils has been found not 00:37:29.730 --> 00:37:33.730 in Africa, but in Asia, in Pakistan. 00:37:40.570 --> 00:37:43.100 This is Khaur near the foothills of the Himalayas 00:37:43.100 --> 00:37:47.300 in Pakistan. 00:37:47.300 --> 00:37:49.600 For the last ten years a joint Pakistan and 00:37:49.600 --> 00:37:52.500 American team has been searching near here for 00:37:52.500 --> 00:37:55.570 those descendants of the Dryopithecines -perhaps 00:37:55.570 --> 00:38:02.730 the most distant obvious ancestors of our species. 00:38:02.730 --> 00:38:04.630 What we all want to know is what happened to the 00:38:04.630 --> 00:38:08.500 Dryopithecines, how and why did the human line 00:38:08.500 --> 00:38:11.500 split from the line of the apes. 00:38:14.230 --> 00:38:16.100 They're looking for the answers in the Potwar 00:38:16.100 --> 00:38:21.500 plateau about fifty miles south of Rawalpindi. 00:38:21.500 --> 00:38:23.570 In these arid badlands, erosion has cut through 00:38:23.570 --> 00:38:26.670 layers of sediments that were laid down between fifteen 00:38:26.670 --> 00:38:30.370 and eight million years ago. 00:38:30.370 --> 00:38:33.000 The fossils found here provide important evidence 00:38:33.000 --> 00:38:35.770 about the earliest hominoids -the name we 00:38:35.770 --> 00:38:40.600 give to the families of apes and humans. 00:38:40.600 --> 00:38:42.130 The co-leader of the expedition 00:38:42.130 --> 00:38:43.930 is Dr. David Pilbeam. 00:38:43.930 --> 00:38:46.430 (Pilbeam) We found over a hundred new hominoids since we 00:38:46.430 --> 00:38:48.330 came here to Pakistan, which is more than double 00:38:48.330 --> 00:38:50.230 what we previously knew, but unfortunately they 00:38:50.230 --> 00:38:54.000 tend to be rather broken and fragmented because 00:38:54.000 --> 00:38:56.800 streams and rivers break up things and scatter 00:38:56.800 --> 00:38:58.630 them. 00:38:58.630 --> 00:39:01.470 We have three sizes of hominoids. 00:39:01.470 --> 00:39:04.200 The first is Gigantopithecus, 00:39:04.200 --> 00:39:05.630 so called because it' s an enormous creature. 00:39:05.630 --> 00:39:10.200 It's jaw dwarfs that of a modern human. 00:39:10.200 --> 00:39:12.970 The next is Sivapithecus, a considerably smaller 00:39:12.970 --> 00:39:15.730 creature and finally, smaller still, 00:39:15.730 --> 00:39:17.870 Ramapithecus. 00:39:17.870 --> 00:39:20.530 They all had relatively large, 00:39:20.530 --> 00:39:22.800 thick-enameled cheek teeth. 00:39:22.800 --> 00:39:26.330 They all have front teeth which although basically 00:39:26.330 --> 00:39:30.770 apelike, show very large amounts of Wear. 00:39:30.770 --> 00:39:35.130 This is Sivapithecus, the canines are worn down in 00:39:35.130 --> 00:39:38.270 the back, in the front and on the tops and the 00:39:38.270 --> 00:39:43.270 incisors are also very markedly worn. 00:39:43.270 --> 00:39:45.100 For a living ape this would show an 00:39:45.100 --> 00:39:48.330 extraordinarily high amount of wear and we 00:39:48.330 --> 00:39:51.400 could conclude from this that we're dealing with 00:39:51.400 --> 00:39:54.430 animals that are still perhaps basically apelike, 00:39:54.430 --> 00:39:57.030 but that they're using their teeth in different 00:39:57.030 --> 00:40:01.370 ways from any living ape. 00:40:01.370 --> 00:40:03.630 (Narrator) Why should their teeth be different? 00:40:03.630 --> 00:40:06.300 One answer came from the sediments in which they 00:40:06.300 --> 00:40:07.100 were found. 00:40:07.100 --> 00:40:08.930 By studying the fossil pollens, 00:40:08.930 --> 00:40:11.730 paleobotanists can tell that at the time of the 00:40:11.730 --> 00:40:13.900 Ramapithecines, it probably looked something 00:40:13.900 --> 00:40:15.600 like this. 00:40:15.600 --> 00:40:17.770 It is forest edge giving way to woodland. 00:40:17.770 --> 00:40:22.500 Woodland only occurs when there are wet and dry 00:40:22.500 --> 00:40:25.230 seasons -and this affects the type of food that's 00:40:25.230 --> 00:40:27.130 available. 00:40:27.130 --> 00:40:32.600 (Pilbeam) When the weather is dry, plants need to protect 00:40:32.600 --> 00:40:36.130 themselves from drying out by developing relatively 00:40:36.130 --> 00:40:38.900 tough or fibrous outer coatings to their seeds or 00:40:38.900 --> 00:40:40.530 their fruits. 00:40:40.530 --> 00:40:44.370 So it's possible that our woodland hominoids were 00:40:44.370 --> 00:40:47.970 eating tougher, more abrasive, 00:40:47.970 --> 00:40:50.500 more difficult to chew food, 00:40:50.500 --> 00:40:54.370 also possibly food that was on average less 00:40:54.370 --> 00:40:57.530 nutritious, processing more of it. 00:40:57.530 --> 00:41:00.230 And this is why they have relatively larger and 00:41:00.230 --> 00:41:03.300 thick enamel -thicker enameled cheek teeth. 00:41:03.300 --> 00:41:05.400 (Narrator) This suggests that the Ramapithecines had indeed 00:41:05.400 --> 00:41:08.330 successfully moved into woodland and more open 00:41:08.330 --> 00:41:09.630 country. 00:41:09.630 --> 00:41:12.270 David Pilbeam is prepared to speculate about other 00:41:12.270 --> 00:41:16.300 ways in which they adapted to these conditions. 00:41:16.300 --> 00:41:19.100 (Pilbeam) All of them probably moved in basically in the way 00:41:19.100 --> 00:41:22.770 that the living apes do, they probably had 00:41:22.770 --> 00:41:24.430 relatively short trunks. 00:41:24.430 --> 00:41:27.630 They moved in the trees and on the ground with 00:41:27.630 --> 00:41:29.570 their bodies more vertical, 00:41:29.570 --> 00:41:31.930 they would have hung below branches. 00:41:31.930 --> 00:41:35.630 I think it's quite reasonable to conclude 00:41:35.630 --> 00:41:38.170 that an animal as small as Ramapithecus when on the 00:41:38.170 --> 00:41:40.730 ground would have moved bipedal quite a lot of the 00:41:40.730 --> 00:41:43.570 time and that this tendency to be upright 00:41:43.570 --> 00:41:46.630 would have been reinforced if it was also feeding on 00:41:46.630 --> 00:41:48.270 the ground. 00:41:48.270 --> 00:41:51.030 (Narrator) So far neither David Pilbeam nor anyone else 00:41:51.030 --> 00:41:54.300 has found enough fossils to prove that Ramapithecus 00:41:54.300 --> 00:41:56.230 walked upright. 00:41:56.230 --> 00:41:59.530 But it is interesting that these fossils are found in 00:41:59.530 --> 00:42:02.270 what was once the kind of open woodland where we 00:42:02.270 --> 00:42:05.300 find all later hominids, the name we give to the 00:42:05.300 --> 00:42:07.900 human family. 00:42:07.900 --> 00:42:10.200 So they could represent the first real shift 00:42:10.200 --> 00:42:13.070 towards us. 00:42:13.070 --> 00:42:15.570 (Pilbeam) When I started work here seven years ago, 00:42:15.570 --> 00:42:17.500 I thought that I had a pretty clear-cut 00:42:17.500 --> 00:42:20.070 understanding of human evolution. 00:42:20.070 --> 00:42:21.800 I thought that it was a relatively simple process 00:42:21.800 --> 00:42:25.070 and I believed that the earliest hominids had 00:42:25.070 --> 00:42:27.770 differentiated from the apes primarily because 00:42:27.770 --> 00:42:30.030 they had begun to use tools and later had 00:42:30.030 --> 00:42:31.770 evolved cultural behavior. 00:42:31.770 --> 00:42:33.400 I don't think that's true anymore. 00:42:33.400 --> 00:42:36.270 We're beginning to look away from the head towards 00:42:36.270 --> 00:42:38.770 the stomach for explanations of what went 00:42:38.770 --> 00:42:40.300 on in our evolution. 00:42:40.300 --> 00:42:42.700 We're beginning to produce explanations that are 00:42:42.700 --> 00:42:45.330 related to food and feeding, 00:42:45.330 --> 00:42:47.330 to diet, to the way the food is obtained and 00:42:47.330 --> 00:42:49.670 processed. 00:42:49.670 --> 00:42:52.070 (Narrator) The shift in diet and habitat that happened here 00:42:52.070 --> 00:42:54.900 between fifteen and eight million years ago could, 00:42:54.900 --> 00:42:57.230 of course lead nowhere. 00:42:57.230 --> 00:42:59.170 But David believes that, for some of the 00:42:59.170 --> 00:43:03.900 Ramapithecines at least, it was significant. 00:43:03.900 --> 00:43:05.900 (Pilbeam) Collectively the Ramapithecids I think can 00:43:05.900 --> 00:43:10.330 be seen as the last common ancestor of the hominoids 00:43:10.330 --> 00:43:13.400 and all of the living apes. 00:43:13.400 --> 00:43:15.330 The Gigantopithecus line became extinct about a 00:43:15.330 --> 00:43:18.200 million years ago. 00:43:18.200 --> 00:43:19.730 I think Sivapithecus makes a good ancestor for the 00:43:19.730 --> 00:43:23.030 one living Asia ape, the orangutan. 00:43:23.030 --> 00:43:26.770 And Ramapithecus itself is our best candidate for the 00:43:26.770 --> 00:43:29.570 earliest hominid. 00:43:29.570 --> 00:43:31.470 I think that undoubted hominids, 00:43:31.470 --> 00:43:34.000 animals that are upright walkers and that have 00:43:34.000 --> 00:43:36.830 small canines, probably evolved in Africa between 00:43:36.830 --> 00:43:39.800 six and eight million years ago and that they did so from 00:43:39.800 --> 00:43:41.930 an animal that would have resembled quite closely 00:43:41.930 --> 00:43:45.370 the Ramapithecus that we have here in Pakistan. 00:43:45.370 --> 00:43:48.130 (Narrator) With so little to go on even this reconstruction 00:43:48.130 --> 00:43:52.500 of a Ramapithecus face is largely supposition. 00:43:52.500 --> 00:43:55.770 It remains an intriguing enigma. 00:43:55.770 --> 00:43:58.130 I don't think at the moment we have enough 00:43:58.130 --> 00:44:00.900 evidence to say definitely whether Ramapithecus was 00:44:00.900 --> 00:44:03.830 or was not our direct ancestor. 00:44:03.830 --> 00:44:05.900 We have jaws and teeth from different parts of 00:44:05.900 --> 00:44:07.830 the world and on the basis of that evidence it's a 00:44:07.830 --> 00:44:09.830 perfectly good candidate. 00:44:09.830 --> 00:44:11.800 I think we all want to have an ancestor that 00:44:11.800 --> 00:44:14.400 dates somewhere between eight and fourteen million years, 00:44:14.400 --> 00:44:15.430 I think it gives a respectability to our 00:44:15.430 --> 00:44:17.700 species. 00:44:17.700 --> 00:44:19.670 But frankly, on the basis of those jaws and teeth we 00:44:19.670 --> 00:44:21.700 can say very little. 00:44:21.700 --> 00:44:24.400 Despite that statement I am guilty of saying too 00:44:24.400 --> 00:44:25.270 much. 00:44:25.270 --> 00:44:27.570 In my own popular books I have frequently shown 00:44:27.570 --> 00:44:30.100 Ramapithecus as standing upright. 00:44:30.100 --> 00:44:32.470 Indeed if you look at all the popular books that 00:44:32.470 --> 00:44:33.830 have been published Ramapithecus is always 00:44:33.830 --> 00:44:37.870 shown as upright or almost upright. 00:44:37.870 --> 00:44:40.800 Some cheat, some show Ramapithecus leaning 00:44:40.800 --> 00:44:43.170 against a tree, this suggests that it may or may 00:44:43.170 --> 00:44:46.470 not have been upright, but on jaws and teeth none of 00:44:46.470 --> 00:44:48.300 us know the answer. 00:44:48.300 --> 00:44:50.370 We have to find other parts of the skeleton. 00:44:50.370 --> 00:44:54.300 After Ramapithecus the story doesn't get much 00:44:54.300 --> 00:44:55.930 better until much later. 00:44:55.930 --> 00:44:58.370 There's a period between eight and four million years where 00:44:58.370 --> 00:45:00.830 there're virtually no fossils. 00:45:00.830 --> 00:45:02.800 Perhaps we haven't looked in the right places. 00:45:02.800 --> 00:45:06.770 The fossils that do exist consist of a few fragments 00:45:06.770 --> 00:45:11.030 that fit in a small box. 00:45:11.030 --> 00:45:13.530 We have a lower jaw dating at about 00:45:13.530 --> 00:45:15.000 five and a half million years 00:45:15.000 --> 00:45:18.370 with a single tooth set in it. 00:45:18.370 --> 00:45:21.470 We have two fragments of the arm: a fragment of the 00:45:21.470 --> 00:45:25.300 upper arm and a fragment of the lower arm. 00:45:25.300 --> 00:45:30.170 We also have two isolated teeth. 00:45:30.170 --> 00:45:32.230 These tell us very little except about the shape of 00:45:32.230 --> 00:45:34.330 those teeth. 00:45:34.330 --> 00:45:36.370 And that is all we have for this long period of 00:45:36.370 --> 00:45:39.370 time, remarkably little. 00:45:44.800 --> 00:45:47.100 Much of the current research efforts in Africa 00:45:47.100 --> 00:45:49.730 and Asia is being directed to try and find fossils 00:45:49.730 --> 00:45:52.730 that will fill this long gap. 00:45:57.600 --> 00:45:59.870 We have recently begun work on the west side of 00:45:59.870 --> 00:46:02.400 Lake Turkana. 00:46:02.400 --> 00:46:04.670 We've come here because these sediments are of the 00:46:04.670 --> 00:46:06.700 right age. 00:46:06.700 --> 00:46:12.000 Some date between four and seven million years. 00:46:12.000 --> 00:46:14.730 I hope that somewhere here in this desolate landscape 00:46:14.730 --> 00:46:17.630 we will find remains of the creatures that evolved 00:46:17.630 --> 00:46:20.330 from the Ramapithecines -creatures that must be 00:46:20.330 --> 00:46:25.800 more closely related to our species. 00:46:25.800 --> 00:46:27.800 Until we find them there is very little that can be 00:46:27.800 --> 00:46:30.530 said with certainty about this long period of our 00:46:30.530 --> 00:46:34.230 evolutionary story. 00:46:34.230 --> 00:46:37.170 We're still not exactly certain what occurred 00:46:37.170 --> 00:46:39.700 during that long gap in the fossil record. 00:46:39.700 --> 00:46:41.800 But what is certain is that by four million years 00:46:41.800 --> 00:46:46.130 ago, here in Africa, a major event had occurred. 00:46:46.130 --> 00:46:48.800 An event that was to have crucial implications and 00:46:48.800 --> 00:46:50.800 which set man apart from all other living 00:46:50.800 --> 00:46:52.570 creatures. 00:46:52.570 --> 00:46:55.400 During that time our primitive apelike ancestor 00:46:55.400 --> 00:46:58.300 stood up on two legs and began to walk upright. 00:46:58.300 --> 00:47:05.800 Once that had happened, our ancestors were well on 00:47:05.800 --> 00:47:07.730 the way to becoming the most successful, 00:47:07.730 --> 00:47:11.900 powerful and dangerous animal on earth.