1 00:00:48,127 --> 00:00:50,118 (SPEAKS TUAREG) 2 00:01:01,687 --> 00:01:03,996 We're looking for a dinosaur. 3 00:01:04,047 --> 00:01:09,440 At the time when the dinosaur first appeared, about 200 million years ago, 4 00:01:09,807 --> 00:01:14,039 all the land on the earth was grouped together in one supercontinent 5 00:01:14,127 --> 00:01:17,517 and the dinosaurs roamed all over it. 6 00:01:17,687 --> 00:01:22,556 And so today their remains can be found in the fragments of that supercontinent, 7 00:01:22,407 --> 00:01:28,801 in Australia, in North America, in Europe and here in Africa. 8 00:01:29,127 --> 00:01:33,757 We're on an expedition in the southern fringes of the Sahara 9 00:01:33,887 --> 00:01:35,878 and the reason we've come here 10 00:01:36,287 --> 00:01:39,802 is that in a desert there's very little vegetation to cover the rocks, 11 00:01:39,967 --> 00:01:44,961 so that if there are dinosaurs in them, we'll be able to see them. 12 00:01:55,527 --> 00:01:59,998 One of the expedition leaders, Dick Moody, showed me their first find. 13 00:02:00,127 --> 00:02:02,960 I'm sure you'll find this one, which we haven't touched, 14 00:02:03,487 --> 00:02:05,842 quite a superb specimen, quite exciting. 15 00:02:05,887 --> 00:02:09,721 0h, it is absolutely magnificent. 16 00:02:10,687 --> 00:02:13,485 This is obviously the backbone, but which way is it lying? 17 00:02:13,887 --> 00:02:18,597 It's running in that direction, we believe, towards the head and towards the east. 18 00:02:18,687 --> 00:02:22,236 And in this direction, generally, back towards the tail. 19 00:02:22,527 --> 00:02:24,597 - And the ribs? - The ribs are running off. 20 00:02:24,727 --> 00:02:29,881 As you can see, they're slightly disarticulated and slightly broken up, 21 00:02:30,007 --> 00:02:33,761 but they are running in that general direction down the sand dune. 22 00:02:33,967 --> 00:02:36,686 And how long do you think the complete animal was? 23 00:02:36,847 --> 00:02:39,122 Between 20 and 30 metres. 24 00:02:39,247 --> 00:02:41,715 - What, that's 90 feet? - Yes. 25 00:02:41,647 --> 00:02:44,161 - That's enormous. - It's a large animal, yes. 26 00:02:44,607 --> 00:02:46,677 How complete do you think it might be? 27 00:02:46,527 --> 00:02:51,317 We're hoping to find some skull material and obviously limb material underneath here. 28 00:02:52,767 --> 00:02:55,440 If we clear these just a little... 29 00:02:55,647 --> 00:02:58,241 The weathered shales in which the bones were embedded 30 00:02:58,527 --> 00:03:02,076 were so soft that we could brush them away with our hands. 31 00:03:05,527 --> 00:03:12,126 After only half an hour, we already had some idea of how much of the animal was preserved. 32 00:03:12,727 --> 00:03:17,437 But it was a further day before all the bones at this site were exposed. 33 00:03:23,047 --> 00:03:25,481 There weren't as many as we had first hoped. 34 00:03:25,927 --> 00:03:28,839 The base of the tail and the lower spine was there, 35 00:03:28,807 --> 00:03:32,356 but the legs and most of the body were missing. 36 00:03:34,287 --> 00:03:39,680 But half a mile away, the rest of the expedition was working on another group of bones. 37 00:03:39,567 --> 00:03:43,685 These were leg bones and probably belonged, if not to the same animal, 38 00:03:43,887 --> 00:03:47,163 then at least to the same kind. 39 00:03:51,087 --> 00:03:56,719 The huge carcass, whatever it was, had clearly already been dismembered before it was buried. 40 00:03:56,687 --> 00:03:59,645 Perhaps other scavenging dinosaurs had pulled it apart. 41 00:04:00,047 --> 00:04:02,197 Perhaps the rotting body had disintegrated 42 00:04:02,247 --> 00:04:05,876 as it lay in the river that eventually buried it in mud. 43 00:04:06,527 --> 00:04:11,396 The expedition was from the Natural History Museum and Kingston Polytechnic in London. 44 00:04:11,767 --> 00:04:14,281 Before the bones could be transported back, 45 00:04:14,567 --> 00:04:20,199 they had to be protected by wrapping them with strips of sackcloth soaked in plaster. 46 00:04:22,687 --> 00:04:28,159 This will harden into a solid jacket that will hold the whole specimen together. 47 00:04:30,087 --> 00:04:33,602 The expedition dug up and plastered almost 100 bones 48 00:04:33,447 --> 00:04:35,836 in the four weeks they worked in the Sahara. 49 00:04:36,327 --> 00:04:38,397 But this was only the start. 50 00:04:38,447 --> 00:04:42,235 Indeed, it won't be until the team gets the bones back to London 51 00:04:42,287 --> 00:04:45,120 and has cleaned them, studied them and pieced them together, 52 00:04:45,167 --> 00:04:49,797 that they will know for sure exactly what kind of dinosaur they've got. 53 00:04:56,007 --> 00:05:00,000 But one thing is certain - it's a giant. 54 00:05:04,127 --> 00:05:10,043 These bones, too, in the museum in East Berlin, came from Africa back in 1912. 55 00:05:09,887 --> 00:05:12,606 When pieced together, they proved to belong 56 00:05:12,767 --> 00:05:16,840 to the most massive land animal known up to that time. 57 00:05:17,087 --> 00:05:21,524 It was 74 feet, 22½ metres long, 58 00:05:21,887 --> 00:05:26,722 it stood 39 feet, that's 12 metres, high, 59 00:05:26,687 --> 00:05:30,646 and it was estimated to weigh 77 tons, 60 00:05:31,007 --> 00:05:34,841 which is as much as 12 bull elephants put together. 61 00:05:34,847 --> 00:05:38,442 This is brachiosaurus. 62 00:05:44,567 --> 00:05:48,355 It's head, perched on top of its immensely long neck, 63 00:05:48,407 --> 00:05:52,116 was comparatively tiny, less than three feet long, 64 00:05:52,247 --> 00:05:55,557 but it has huge nostrils, high on its forehead 65 00:05:55,607 --> 00:05:59,566 and they led some people to suggest that this animal lived in lakes, 66 00:05:59,927 --> 00:06:03,078 with its head and nostrils above the surface 67 00:06:03,287 --> 00:06:08,964 while it walked along the bottom with the water supporting its huge body. 68 00:06:09,047 --> 00:06:12,039 But that, we now know, would have been impossible. 69 00:06:12,847 --> 00:06:15,680 If its nostrils were open at the surface, 70 00:06:15,727 --> 00:06:19,242 the water pressure 30 or so feet below the surface 71 00:06:19,567 --> 00:06:23,446 would have been so great that its lungs would've collapsed. 72 00:06:23,407 --> 00:06:28,435 Furthermore, the shape of its legs and its deep, narrow chest 73 00:06:28,687 --> 00:06:31,121 all suggest an animal that lived on land. 74 00:06:31,567 --> 00:06:34,479 So now, it seems, we have to think of brachiosaurus 75 00:06:34,447 --> 00:06:40,841 as a kind of gigantic reptilian giraffe, browsing the tops of the trees. 76 00:06:46,967 --> 00:06:50,721 Brachiosaurus may be the biggest mounted dinosaur in the world, 77 00:06:50,807 --> 00:06:53,526 but it may not be so for long. 78 00:06:58,007 --> 00:07:02,717 In New Mexico, they've found remains of an animal that may be even bigger. 79 00:07:03,287 --> 00:07:07,644 They've already given it a name, seismosaurus, the "earth-shaker". 80 00:07:07,607 --> 00:07:11,725 But the rock in which it is embedded, unlike the soft shales of the Sahara, 81 00:07:11,687 --> 00:07:13,723 is almost as hard as concrete, 82 00:07:14,087 --> 00:07:18,365 and excavating it is a laborious and time-consuming business. 83 00:07:20,807 --> 00:07:24,641 The excavation leader, Dave Gillette, told me the story. 84 00:07:24,527 --> 00:07:28,122 This is where we found the first set of vertebrae in 1979. 85 00:07:28,367 --> 00:07:30,483 We finally excavated in 1985. 86 00:07:30,767 --> 00:07:32,678 How much of it was showing? 87 00:07:32,687 --> 00:07:34,598 Only the upper part. 88 00:07:34,607 --> 00:07:38,600 It was showing as though it had been carved out of the rock in bas-relief. 89 00:07:38,927 --> 00:07:41,680 It was perfectly exposed just in this fashion. 90 00:07:41,807 --> 00:07:44,879 - And then? - Then, when we looked closer in the ground, 91 00:07:45,167 --> 00:07:50,195 we found a total of eight vertebrae along this line, all in perfect articulation, 92 00:07:50,447 --> 00:07:54,201 and they're from the basal part of the tail, leading into the pelvic region. 93 00:07:54,287 --> 00:07:57,518 There's another vertebra here. Then we took out two large blocks, 94 00:07:57,647 --> 00:08:02,960 one here, another here at the base of the tail, that led right up to the hip region. 95 00:08:02,967 --> 00:08:06,004 - What's that? - This is a rib, which has been displaced 96 00:08:06,207 --> 00:08:10,325 from the proper anatomical position when the animal died. 97 00:08:10,607 --> 00:08:13,758 - The rock looks awful. - It is terribly hard around the bone. 98 00:08:13,967 --> 00:08:18,518 - It takes for ever for us to excavate the bones. - Does the animal go on in there? 99 00:08:18,767 --> 00:08:23,921 We think the animal continues right into the hill to the north for another 60 or 70 feet. 100 00:08:23,967 --> 00:08:26,356 - Under the rock? - About eight feet deep. 101 00:08:26,367 --> 00:08:30,485 We're using sophisticated and experimental remote-sensing techniques 102 00:08:30,687 --> 00:08:33,679 to try to see those bones before we excavate. 103 00:08:36,447 --> 00:08:40,645 The site is only a few miles from Los Alamos atomic research station, 104 00:08:40,767 --> 00:08:43,156 and the scientists there, on their days off, 105 00:08:43,167 --> 00:08:46,523 come out to use the most advanced techniques of nuclear physics 106 00:08:46,527 --> 00:08:50,361 to help Dave locate his dinosaur bones deep in the rock. 107 00:08:50,807 --> 00:08:54,766 This sledge carries a still-experimental remote-sensing device, 108 00:08:54,647 --> 00:08:57,115 a kind of radar that looks into the ground. 109 00:09:00,487 --> 00:09:03,399 It's dragged along carefully-plotted tracks across the rock 110 00:09:03,367 --> 00:09:07,963 and already readings from it are beginning to confirm the gigantic size of the animal. 111 00:09:08,087 --> 00:09:12,126 I asked Dave how long he thought seismosaurus might eventually prove to be. 112 00:09:12,487 --> 00:09:17,607 My best estimate is 140 feet in length, from the snout to the tip of the tail. 113 00:09:17,767 --> 00:09:19,325 How does that compare? 114 00:09:19,207 --> 00:09:22,995 The previous record-holder was diplodocus at 87 feet. 115 00:09:23,527 --> 00:09:25,518 We're approaching twice that length. 116 00:09:25,447 --> 00:09:29,156 When will you actually know whether this is a world-beater? 117 00:09:29,287 --> 00:09:33,678 We know now. We have good confidence in our calculations. 118 00:09:37,847 --> 00:09:41,965 Dinosaurs certainly include some gigantic animals. 119 00:09:43,607 --> 00:09:46,280 Stegosaurus, bigger than a rhinoceros. 120 00:09:47,367 --> 00:09:50,598 Allosaurus, tall as a giraffe. 121 00:09:59,847 --> 00:10:03,965 But they weren't all huge. Some were no bigger than a dog. 122 00:10:14,167 --> 00:10:17,000 Nonetheless, many were very big indeed 123 00:10:17,527 --> 00:10:22,840 and they certainly include some of the most spectacular animals ever to walk the earth. 124 00:10:27,127 --> 00:10:32,326 They dominated the world for over 160 million years. 125 00:10:53,527 --> 00:10:58,362 But what did a dinosaur like this actually look like when it was alive? 126 00:10:58,367 --> 00:11:03,157 Did it have hide like an elephant, or was it covered in scales like a lizard, 127 00:11:03,167 --> 00:11:05,886 or perhaps hair, like a horse? 128 00:11:06,047 --> 00:11:10,962 The skin, of course, like the rest of the soft parts, is very rarely fossilised, 129 00:11:11,327 --> 00:11:15,115 but in this exceptional example, it has been. 130 00:11:18,527 --> 00:11:22,486 This is the fleshy pad on the underside of its foot. 131 00:11:26,287 --> 00:11:30,997 And behind you can still see the wrinkles in the skin on its belly. 132 00:11:33,527 --> 00:11:38,920 This particular individual was, most unusually, entombed in the hot sand of a desert, 133 00:11:38,807 --> 00:11:41,275 and although its flesh decayed and disappeared, 134 00:11:41,687 --> 00:11:45,043 its tough hide was baked and mummified. 135 00:11:44,967 --> 00:11:48,755 You can even see the impressions of the scales in the skin. 136 00:11:49,767 --> 00:11:51,758 From remarkable specimens like this, 137 00:11:52,167 --> 00:11:55,364 we can deduce that dinosaur skin was thick and tough, 138 00:11:55,527 --> 00:11:58,599 probably not unlike an elephant's hide. 139 00:11:59,367 --> 00:12:02,962 But was it grey and colourless like an elephant's? 140 00:12:08,487 --> 00:12:14,403 0r was it, perhaps, brightly coloured, as are the skins of many reptiles today? 141 00:12:18,567 --> 00:12:20,797 Animal pigments don't fossilise, 142 00:12:20,967 --> 00:12:24,721 so it's anyone's guess as to whether the dinosaurs were coloured or not, 143 00:12:25,007 --> 00:12:27,965 but it's tempting to think that they were. 144 00:12:34,647 --> 00:12:39,004 But we can go further than simply investigating the size and appearance of dinosaurs. 145 00:12:41,847 --> 00:12:43,644 What did the dinosaurs eat? 146 00:12:44,247 --> 00:12:48,798 Well, flowering plants didn't develop until about 100 million years ago. 147 00:12:48,567 --> 00:12:51,923 That means that for most of the time dinosaurs were on earth, 148 00:12:52,407 --> 00:12:56,525 there were very few of the kinds of plant that dominate the land today. 149 00:12:56,727 --> 00:13:01,118 There were no oak trees or hazel in Europe, on which deer feed. 150 00:13:01,047 --> 00:13:05,996 In Africa there was no thorn scrub or acacia, on which elephant and giraffe browse. 151 00:13:06,327 --> 00:13:12,562 Most important of all, there was no grass, on which horses or bison or antelope graze. 152 00:13:12,567 --> 00:13:15,798 Instead there were plants like these. 153 00:13:21,207 --> 00:13:22,845 These are cycads. 154 00:13:22,647 --> 00:13:27,163 Today they grow wild in only a very few places, and mostly in the tropics. 155 00:13:27,447 --> 00:13:31,804 But when the dinosaurs first evolved, they were spread worldwide. 156 00:13:34,647 --> 00:13:40,438 In addition to these, there were also tree-ferns and primitive conifers like pines. 157 00:13:40,407 --> 00:13:46,243 But all these plants had tough, fibrous leaves, almost indigestible, you might think. 158 00:13:50,767 --> 00:13:57,479 To make matters more awkward, the early dinosaurs were poorly equipped with teeth. 159 00:13:57,967 --> 00:14:01,437 Diplodocus had only these small, peg-like teeth 160 00:14:01,327 --> 00:14:05,081 that could have done little more than just nip off the fronds. 161 00:14:05,647 --> 00:14:11,563 It certainly couldn't have chewed them. So how did it avoid terrible indigestion? 162 00:14:19,087 --> 00:14:23,842 Clues to the answer were eventually found lower down in the skeleton. 163 00:14:23,887 --> 00:14:28,165 Between the ribs of specimens that had been fossilised more or less complete 164 00:14:28,687 --> 00:14:33,317 are sometimes found great heaps of small, highly polished pebbles. 165 00:14:33,487 --> 00:14:35,762 It seems these had been swallowed and stored 166 00:14:35,887 --> 00:14:39,084 in a muscular pouch of the dinosaur's stomach, a gizzard, 167 00:14:39,247 --> 00:14:44,958 which served as a kind of internal mill to grind up its fibrous meals. 168 00:14:45,967 --> 00:14:48,765 Even so, it must have taken a very long time 169 00:14:48,767 --> 00:14:55,115 for a dinosaur's digestive juices to break down the woody stems and trunks of plants like these. 170 00:14:55,487 --> 00:14:58,718 If you have to keep your food in your stomach a long time, 171 00:14:58,847 --> 00:15:03,238 then you need a very big stomach to serve as a storage vat. 172 00:15:06,527 --> 00:15:10,406 That, in turn, means you need a very large body to carry it. 173 00:15:10,367 --> 00:15:12,722 So the ancient pastures of tree-ferns 174 00:15:12,767 --> 00:15:19,206 may be one of the main reasons why plant-eating dinosaurs grew so big. 175 00:15:19,487 --> 00:15:23,480 As millions of years passed, however, evolution brought changes. 176 00:15:23,807 --> 00:15:29,564 The first flowering plants appeared, and so did new kinds of plant-eating dinosaurs. 177 00:15:29,567 --> 00:15:34,038 These are hadrosaurs. They had no teeth at all in the front of their jaws. 178 00:15:34,367 --> 00:15:39,282 Instead, the rounded bone was almost certainly covered with a horny sheath. 179 00:15:39,167 --> 00:15:44,366 With this, they could have done little more than just nip off leaves and twigs. 180 00:15:48,287 --> 00:15:53,042 But inside the mouth, at the back of the jaws, they had an enormous battery of teeth, 181 00:15:53,087 --> 00:15:54,884 row upon row. 182 00:15:55,007 --> 00:15:57,965 This particular jaw had over 200. 183 00:15:58,367 --> 00:16:03,395 As these crushed and ground the tough fibres, they were inevitably worn down. 184 00:16:03,647 --> 00:16:08,721 But new ones grew in the bone of the jaw beneath and moved up to replace the old ones. 185 00:16:08,927 --> 00:16:11,885 But could they use them to chew? 186 00:16:11,607 --> 00:16:16,601 Mammals like this camel can chew by moving their lower jaw from side to side, 187 00:16:16,887 --> 00:16:21,039 so they are able to break down the toughest of plant foods. 188 00:16:21,447 --> 00:16:25,235 The dinosaurs were reptiles, and no reptile can do that. 189 00:16:25,287 --> 00:16:31,283 They can only move their jaws up and down, and that puts a real limit on what they can eat. 190 00:16:32,927 --> 00:16:36,761 The hadrosaurs dealt with that problem in a most remarkable way. 191 00:16:36,807 --> 00:16:40,482 The highlighted upper jaw could actually hinge outwards. 192 00:16:40,647 --> 00:16:42,797 When a hadrosaur's skull is examined closely, 193 00:16:43,047 --> 00:16:48,440 it reveals an elastic joint between the upper jaw and the roof of the snout. 194 00:16:51,207 --> 00:16:55,917 This means that as the lower jaw moves up, it pushes aside the upper jaw, 195 00:16:56,007 --> 00:17:01,035 in effect, chewing without any sideways movement of the lower jaw at all. 196 00:17:13,687 --> 00:17:18,078 The most powerful grinding battery of all was that possessed by triceratops, 197 00:17:18,007 --> 00:17:20,441 one of the last of the dinosaurs. 198 00:17:20,407 --> 00:17:24,719 This, the product of 100 million years of development in the technique of chewing, 199 00:17:25,207 --> 00:17:29,837 is perhaps the most powerful chewing device ever possessed by any animal. 200 00:17:30,007 --> 00:17:32,965 A huge beak in the front served as shears 201 00:17:32,887 --> 00:17:36,084 which could probably slice clean through a tree trunk. 202 00:17:36,247 --> 00:17:39,125 The branches were then moved to the back of the mouth, 203 00:17:39,607 --> 00:17:42,963 where the massive grinders reduced them to pulp. 204 00:17:52,807 --> 00:17:56,436 But these teeth belong to a very different sort of animal. 205 00:17:56,647 --> 00:17:59,559 These are not thin pegs for nipping off bits of leaves. 206 00:18:00,047 --> 00:18:04,040 These are daggers, finely serrated along the edge like steak knives, 207 00:18:03,887 --> 00:18:07,675 adapted to slicing through flesh and hide. 208 00:18:08,207 --> 00:18:13,565 In life, much of the empty space in the skull here would have been filled by massive muscles, 209 00:18:13,487 --> 00:18:17,116 which gave an enormously powerful bite to these huge jaws. 210 00:18:17,447 --> 00:18:22,237 This is Tyrannosaurus rex, the biggest of all the meat-eating dinosaurs, 211 00:18:22,247 --> 00:18:26,160 measuring over forty feet long and weighing about seven tons, 212 00:18:26,567 --> 00:18:30,924 surely the most terrifying hunter ever to roam the earth. 213 00:18:56,047 --> 00:18:58,959 With long, curved claws and sharp teeth, 214 00:18:59,127 --> 00:19:04,076 the carnivorous dinosaurs must have been terrifying and highly efficient predators. 215 00:19:04,407 --> 00:19:08,923 But other kinds of dinosaurs evolved that had no teeth at all. 216 00:19:16,367 --> 00:19:20,280 This one seems to have been rather like the ostrich of today. 217 00:19:23,567 --> 00:19:27,958 So perhaps, like an ostrich, this dinosaur, called struthiomimus, 218 00:19:28,367 --> 00:19:33,839 picked up and swallowed anything, animal or vegetable, it considered remotely edible. 219 00:19:36,047 --> 00:19:39,562 So the bones of dinosaurs, carefully pieced together, 220 00:19:39,647 --> 00:19:42,559 can tell us a great deal about how big they were, 221 00:19:43,007 --> 00:19:46,283 what they fed on, and therefore their relationships with one another, 222 00:19:46,367 --> 00:19:48,483 and how their limbs articulated. 223 00:19:48,767 --> 00:19:50,758 But how fast could they move? 224 00:19:50,687 --> 00:19:54,999 To answer that question, you have to come to a place like this. 225 00:19:57,967 --> 00:20:01,755 150 million years ago, there was a mudflat here, 226 00:20:01,807 --> 00:20:04,367 around the margin of a freshwater lake. 227 00:20:04,687 --> 00:20:07,918 The lake filled and eventually sediments covered the whole area, 228 00:20:08,047 --> 00:20:10,959 and the mudflats turned into mudstones. 229 00:20:10,927 --> 00:20:14,124 In them are preserved huge footprints - 230 00:20:14,287 --> 00:20:16,676 dinosaur footprints. 231 00:20:19,927 --> 00:20:22,441 These, nearly a yard across, 232 00:20:22,807 --> 00:20:28,245 can only have been made by a huge plant-eater like a brontosaur such as diplodocus. 233 00:20:28,367 --> 00:20:30,801 No other had such a huge foot. 234 00:20:30,767 --> 00:20:35,522 Here the animal has trodden on a small shell, a kind of freshwater mussel. 235 00:20:35,687 --> 00:20:38,838 Molluscs virtually identical to this still live today, 236 00:20:39,047 --> 00:20:42,084 but only in water that is less than three feet deep. 237 00:20:42,407 --> 00:20:45,717 So these little shells confirm that these dinosaurs that day 238 00:20:45,767 --> 00:20:48,486 were splashing through the shallows. 239 00:20:50,567 --> 00:20:55,960 If you can measure an animal's stride from its tracks, and also know the length of its legs, 240 00:20:56,087 --> 00:21:00,080 it's possible to calculate the speed at which it was moving. 241 00:21:00,487 --> 00:21:05,481 The brontosaurs had legs that were about nine feet long, as we know from their skeletons. 242 00:21:05,767 --> 00:21:09,760 But this animal's right hind leg, which was printed here, 243 00:21:10,087 --> 00:21:15,115 is only about six feet from the next print in the sequence. 244 00:21:15,367 --> 00:21:20,395 So we can be pretty sure the animal that was moving along here was moving fairly slowly, 245 00:21:20,647 --> 00:21:23,400 as perhaps you'd expect if it was just plodding along, 246 00:21:23,527 --> 00:21:26,325 looking for food around the margin of a lake. 247 00:21:26,407 --> 00:21:30,082 But, in fact, although thousands of these prints have now been found, 248 00:21:30,247 --> 00:21:33,876 not one of them has a stride longer than 12 feet. 249 00:21:34,087 --> 00:21:39,081 So we can be pretty certain that these animals were fairly slow-moving. 250 00:21:52,247 --> 00:21:54,886 These prints, though, are very different, 251 00:21:55,127 --> 00:21:58,085 not circular but with three prominent toes. 252 00:21:59,847 --> 00:22:05,922 At the end of each, there is a deep, sharp mark that can only have been made by a claw. 253 00:22:06,087 --> 00:22:12,606 They match the three-toed feet of theropods, medium-sized, carnivorous dinosaurs. 254 00:22:12,407 --> 00:22:15,717 From tracks like these, it's been calculated that some of these hunters 255 00:22:15,807 --> 00:22:19,083 could run at up to 30 miles an hour. 256 00:22:21,567 --> 00:22:24,525 Moving at such speeds demands a great deal of energy, 257 00:22:24,927 --> 00:22:29,079 and an animal can only produce enough if it has a warm body. 258 00:22:29,167 --> 00:22:35,037 So did the dinosaurs get their energy directly from the sun, as reptiles do today, 259 00:22:34,927 --> 00:22:38,886 or could they generate warmth internally, like birds and mammals? 260 00:22:39,247 --> 00:22:42,159 That is a question of great debate. 261 00:22:44,767 --> 00:22:47,964 This is how Tyrannosaurus rex may have moved, 262 00:22:48,407 --> 00:22:51,877 in the opinion of one of the new generation of dinosaur interpreters, 263 00:22:52,087 --> 00:22:54,806 Robert Bakker of the Museum of Colorado. 264 00:22:54,967 --> 00:22:59,199 0K, Tyrannosaurus rex, the most famous dinosaur, the most popular dinosaur, 265 00:22:59,287 --> 00:23:05,522 and here it is, running at 40 miles per hour, faster than a rhino, faster than an elephant. 266 00:23:05,527 --> 00:23:08,405 This T. Rex is going faster than a lion. 267 00:23:08,407 --> 00:23:11,319 Yes, but that's your animation. How do you know? 268 00:23:11,847 --> 00:23:15,601 Because of the way the muscles were hung on those leg bones, 269 00:23:15,687 --> 00:23:18,440 the way the calf muscles were hung on that knee, 270 00:23:18,367 --> 00:23:21,404 and the way the massive thigh muscles were hung on that ilium. 271 00:23:21,847 --> 00:23:26,443 - But why does that prove it was warm-blooded? - Let's look at the real one, eh? 272 00:23:28,127 --> 00:23:32,643 Could it really have reared up like that and lifted its immense length? 273 00:23:32,927 --> 00:23:35,885 Absolutely, and more. It could jump, it could run fast. 274 00:23:35,807 --> 00:23:40,085 This is a T. Rex, a real one, a cast, with a bloody big knee, right? 275 00:23:40,607 --> 00:23:44,566 - But why does that make it warm-blooded? - Actually, it's the other way around. 276 00:23:44,567 --> 00:23:49,925 Unlike the Pentagon, evolution doesn't build more strength than the animal needs. 277 00:23:50,327 --> 00:23:56,596 This animal is immensely strong. It has a strong knee and a bloody big drumstick of calf muscle 278 00:23:56,567 --> 00:24:01,277 to run fast, because warm-bloodedness demands speed. 279 00:24:01,367 --> 00:24:05,485 This animal has to cruise fast and it needs great bursts of speed 280 00:24:05,687 --> 00:24:08,997 because it has to kill more often than a cold-blooded animal. 281 00:24:09,047 --> 00:24:13,438 There is no cold-blooded animal today with this great strength. None. 282 00:24:13,847 --> 00:24:17,362 This is not a scaled-up lizard or a scaled-up tortoise. 283 00:24:17,207 --> 00:24:22,600 This is an enlarged, five-ton, meat-eating roadrunner, that's what it is. 284 00:24:23,167 --> 00:24:25,556 And like a roadrunner, it's eating frequently. 285 00:24:25,687 --> 00:24:30,203 There's another message about speed in the skeleton, not in the legs but in the chest, 286 00:24:30,007 --> 00:24:35,365 because in the chest, in the first three ribs, in that space, 287 00:24:35,767 --> 00:24:39,806 there is only one organ housed, the cardiac chamber, the heart. 288 00:24:40,087 --> 00:24:44,080 And in modern cold-bloods, the heart is very small, 289 00:24:43,927 --> 00:24:48,318 because cold-blooded animals need only a weak cardiac organ. 290 00:24:48,727 --> 00:24:54,962 But look at this: The first rib, the second rib, the third rib. Look how long that is. 291 00:24:54,967 --> 00:25:00,041 There was housed in these ribs, without doubt, a gigantic heart 292 00:25:00,247 --> 00:25:07,244 designed to pump, designed to put out blood flow at emphatically warm-blooded levels. 293 00:25:16,687 --> 00:25:22,523 So maybe we should get rid of the image of dinosaurs as slow, lumbering plodders 294 00:25:22,647 --> 00:25:27,516 and think of them instead as nimble and agile in spite of their size. 295 00:25:27,567 --> 00:25:29,717 (BL00D-CURDLING R0AR) 296 00:25:32,447 --> 00:25:37,601 The truth is almost certainly that some were warm-blooded and others were not. 297 00:25:38,687 --> 00:25:43,602 A skeleton can not only give clues about the temperature of an animal's blood, 298 00:25:43,967 --> 00:25:49,678 it can, perhaps even more surprisingly, reveal something about the animal's social life. 299 00:25:49,727 --> 00:25:52,195 This is the skull of a hadrosaur. 300 00:25:52,127 --> 00:25:57,406 Like all hadrosaurs, it has a rounded front to its jaws, lacking in teeth, 301 00:25:57,887 --> 00:26:00,606 which in life were probably covered with a horn, 302 00:26:00,767 --> 00:26:05,318 and which give the family as a whole the name duck-billed dinosaurs. 303 00:26:05,087 --> 00:26:09,000 At the back there is a battery of powerful, plant-crushing teeth. 304 00:26:09,407 --> 00:26:13,639 In fact, the skulls of all hadrosaurs are very much the same, 305 00:26:13,727 --> 00:26:18,243 except for one feature - this, a crest. 306 00:26:18,527 --> 00:26:21,325 And this varies amazingly. 307 00:26:21,407 --> 00:26:25,286 This one is thin and forward-pointing, 308 00:26:25,247 --> 00:26:29,763 this one is long and goes right down the front of the skull 309 00:26:30,047 --> 00:26:35,121 and this one is broad and plate-like and sits on top of the skull. 310 00:26:35,327 --> 00:26:38,478 So these are three separate species. 311 00:26:38,687 --> 00:26:41,201 But this is almost certainly a male, 312 00:26:41,567 --> 00:26:46,721 because here's another one with very much the same shape of crest on top of the skull, 313 00:26:46,847 --> 00:26:50,522 but slightly smaller, so it's probably a female. 314 00:26:50,687 --> 00:26:56,080 And there is a third in which the same shape of crest is only just developing, 315 00:26:55,967 --> 00:26:57,958 so that's probably half-grown. 316 00:27:02,207 --> 00:27:08,476 So crests in hadrosaurs served to proclaim an individual's sex, age and species. 317 00:27:08,447 --> 00:27:10,597 And since such adornments that do that 318 00:27:10,847 --> 00:27:14,965 elsewhere in the animal kingdom are very often made more obvious with colour, 319 00:27:15,167 --> 00:27:20,036 we can speculate that the dinosaurs were indeed quite spectacular-looking animals, 320 00:27:19,967 --> 00:27:24,677 as the character of their scaly skin has already suggested. 321 00:27:26,687 --> 00:27:30,236 But these crests were more than visual signals. 322 00:27:32,447 --> 00:27:38,283 Inside, there are air chambers, which must have acted as resonators when the animals bellowed. 323 00:27:40,127 --> 00:27:44,166 Since the air chambers vary in size and shape as much as the crests, 324 00:27:43,967 --> 00:27:47,721 each species must have had its own characteristic call. 325 00:27:47,807 --> 00:27:49,798 (GRUNTING) 326 00:28:06,047 --> 00:28:09,403 And they probably roared in deafening choruses, 327 00:28:09,407 --> 00:28:14,162 for we know that plant-eating dinosaurs lived in herds, as wildebeest do today. 328 00:28:14,687 --> 00:28:16,917 In Montana, deposits have been discovered 329 00:28:17,087 --> 00:28:21,683 where the bones of hadrosaurs are piled up in vast numbers. 330 00:28:23,807 --> 00:28:27,402 Jack Horner, the researcher who discovered the remains of the herds, 331 00:28:27,647 --> 00:28:30,923 has also found in Montana even more extraordinary evidence 332 00:28:31,007 --> 00:28:33,157 of the social life of dinosaurs. 333 00:28:33,407 --> 00:28:35,875 He's actually found their nests and eggs, 334 00:28:36,247 --> 00:28:40,001 and he showed me where I, too, could pick up bits of the shell. 335 00:28:40,087 --> 00:28:42,282 (ATTENBOROUGH) Is that anything? (HORNER) Just eggshell. 336 00:28:42,487 --> 00:28:45,001 (ATTENBOROUGH) What do you mean, just? 337 00:28:44,887 --> 00:28:47,117 (ATTENBOROUGH) Really? (HORNER) Well... 338 00:28:47,287 --> 00:28:52,964 ...when we're looking for a nest, what we want to see is... Eggshell is important. 339 00:28:53,527 --> 00:28:56,917 - Is it always black? - Yep. 340 00:28:56,887 --> 00:28:59,606 In this formation it's always black. 341 00:28:59,767 --> 00:29:01,997 In other formations it can be other colours. 342 00:29:02,167 --> 00:29:05,876 If the piece is big enough, you can see the texture of the egg 343 00:29:06,007 --> 00:29:08,680 and then, with a microscope, you can see the pores. 344 00:29:09,007 --> 00:29:11,521 Is this the sort of size you get normally? 345 00:29:11,407 --> 00:29:16,083 Well, in a nest where there's babies, the eggshell will be really tiny 346 00:29:16,527 --> 00:29:19,803 because the babies were in the nest, they trampled the eggs 347 00:29:19,887 --> 00:29:23,084 and so it gets broken up quite bad. 348 00:29:23,247 --> 00:29:28,002 But if we find a nest that was deserted after the eggs had been laid, 349 00:29:28,207 --> 00:29:30,198 then we'll find big pieces. 350 00:29:30,927 --> 00:29:34,966 Jack has even discovered complete clutches of unhatched eggs 351 00:29:35,247 --> 00:29:37,124 which he's taken back to his lab. 352 00:29:38,927 --> 00:29:43,557 Now this nest is actually upside down, isn't it, because that's the top of the jacket. 353 00:29:43,727 --> 00:29:46,400 And so these are the eggs? 354 00:29:46,607 --> 00:29:48,598 These are the eggs, yeah. 355 00:29:48,527 --> 00:29:51,837 This is the centre egg in the nest. 356 00:29:51,887 --> 00:29:55,118 The centre egg is always laid upright 357 00:29:55,647 --> 00:30:00,402 and then each egg out from the centre becomes more and more inclined. 358 00:30:00,447 --> 00:30:03,200 - They were laid spirally? - Spiral, uh-huh. 359 00:30:03,527 --> 00:30:06,519 - This was the first? - That was the first, I assume. 360 00:30:06,607 --> 00:30:09,440 - Are they loose? - Yes, this one's loose. 361 00:30:09,607 --> 00:30:15,955 You can see the pointed end of the egg, and the top of the egg has been smushed down. 362 00:30:15,847 --> 00:30:20,204 - And is there shell on there? - Yeah, this is all shell. 363 00:30:20,647 --> 00:30:23,719 This whole nest, presumably, was deserted by the parents. 364 00:30:24,007 --> 00:30:25,998 Apparently so, yeah. 365 00:30:25,927 --> 00:30:28,646 - Do you think there's anything in that? - Yes. 366 00:30:28,967 --> 00:30:32,403 - I don't think there is, I know. - How do you know? 367 00:30:32,327 --> 00:30:38,197 They've been x-rayed and CAT-scanned, and there are indications of little ones in there. 368 00:30:38,567 --> 00:30:43,846 How can you wait? Why don't you hit it with a spoon and take it out? 369 00:30:43,847 --> 00:30:48,284 I would like to do that. My preparators tell me I'm not supposed to. 370 00:30:48,647 --> 00:30:52,925 - Have you got an opened egg? - Yes, we have one from another nest. 371 00:30:54,967 --> 00:30:58,437 - This was a clutch of nineteen eggs. - Nineteen? 372 00:30:58,807 --> 00:31:03,676 Nineteen, and all nineteen have embryos. This is one of the better ones. 373 00:31:04,327 --> 00:31:08,479 What you see here is the thigh-bone, the femur, 374 00:31:08,647 --> 00:31:14,836 the tibia and then the ankle joint with the foot underneath. 375 00:31:14,847 --> 00:31:16,838 Very carefully open it up. 376 00:31:18,087 --> 00:31:22,239 - And what can we see there? - What we're looking at is the right leg. 377 00:31:22,127 --> 00:31:24,118 There's the left leg, the tibia. 378 00:31:24,527 --> 00:31:27,678 And then between the knees is the skull, 379 00:31:27,887 --> 00:31:30,003 sitting right in here. 380 00:31:30,207 --> 00:31:34,405 So we can see that tiny little teeth had erupted in the jaw. 381 00:31:34,447 --> 00:31:37,837 (ATTENBOROUGH) So it could give you a nip as soon as it hatched, 382 00:31:37,807 --> 00:31:41,595 just like young alligators can today. 383 00:31:42,047 --> 00:31:45,119 What about individual bones, do you ever get them out? 384 00:31:45,407 --> 00:31:46,886 Yeah. 385 00:31:46,847 --> 00:31:52,444 One of the eggs I took completely apart and just took out this. 386 00:31:53,967 --> 00:32:00,600 It's a humerus, the upper arm-bone of the embryo. 387 00:32:01,167 --> 00:32:07,003 Just for comparison, so you get some idea of what it looks like, 388 00:32:06,927 --> 00:32:09,236 here's a sub-adult. 389 00:32:09,327 --> 00:32:14,321 - So you can see, it had a little growing to do. - Beautiful. 390 00:32:15,607 --> 00:32:17,882 The bones of young a few weeks old 391 00:32:18,007 --> 00:32:21,283 also reveal a great deal about the hadrosaur's habits. 392 00:32:21,367 --> 00:32:25,645 They are found inside the nest, implying that the young stayed there. 393 00:32:25,927 --> 00:32:30,364 That means their parents must have brought back food to the nest to feed them, 394 00:32:30,247 --> 00:32:35,844 and there's confirmation of that in their teeth, which are already slightly worn. 395 00:32:39,847 --> 00:32:43,886 The hadrosaurs flourished around 75 million years ago. 396 00:32:44,167 --> 00:32:47,796 In Montana, the climate was much warmer than it is there today, 397 00:32:48,007 --> 00:32:51,363 and there were swamps fringing an inland sea. 398 00:32:52,807 --> 00:32:56,083 The dinosaurs had reached the pinnacle of their evolution 399 00:32:56,167 --> 00:32:58,727 and many different kinds lumbered through the swamps 400 00:32:59,047 --> 00:33:03,916 which, then as now, were also the home of many other reptiles and birds. 401 00:33:21,887 --> 00:33:28,838 But 64 million years ago, the hadrosaurs and all the other dinosaurs vanished. 402 00:33:29,687 --> 00:33:33,441 The reign of the dinosaurs had ended. 403 00:33:40,407 --> 00:33:43,717 There are many theories as to why the dinosaurs finally became extinct. 404 00:33:44,247 --> 00:33:48,126 One of the most recent is that an asteroid collided with the earth, 405 00:33:48,087 --> 00:33:50,282 creating such an immense explosion on impact 406 00:33:50,487 --> 00:33:54,116 that the skies filled with dust, blotting out the sun. 407 00:33:54,327 --> 00:33:56,477 In the darkness, the plants all died, 408 00:33:56,727 --> 00:34:00,083 and the dinosaurs, with nothing to eat, starved to death. 409 00:34:00,087 --> 00:34:02,760 There are two problems with that or any other theory 410 00:34:02,967 --> 00:34:06,562 which depends upon a single catastrophe as the explanation. 411 00:34:06,807 --> 00:34:10,766 The first is that the dinosaurs didn't die out in a year or a decade 412 00:34:10,647 --> 00:34:12,797 but over thousands of years. 413 00:34:13,047 --> 00:34:17,563 The second is that, although the dinosaurs died out, many other creatures didn't. 414 00:34:21,727 --> 00:34:25,720 These alligators are reptiles, just as the dinosaurs were. 415 00:34:25,567 --> 00:34:30,436 They evolved on earth long before the dinosaurs, yet they've survived to the present. 416 00:34:30,847 --> 00:34:34,635 It seems unlikely that they would have lived through a sudden global catastrophe 417 00:34:34,527 --> 00:34:36,836 in which the dinosaurs perished. 418 00:34:40,807 --> 00:34:46,325 A more likely explanation, to my mind, is a gradual change in the earth's climate. 419 00:34:46,567 --> 00:34:51,846 Some animals, birds, for example, were better able to cope with this than the dinosaurs, 420 00:34:52,047 --> 00:34:55,722 with their less-than-perfect control over their body temperature. 421 00:34:57,527 --> 00:34:59,836 The early birds, like birds today, 422 00:34:59,927 --> 00:35:03,920 were protected by their superbly efficient insulating coats of feathers, 423 00:35:04,247 --> 00:35:05,760 so they survived. 424 00:35:09,727 --> 00:35:14,278 Small reptiles were able to take refuge against the cold in nooks and crannies, 425 00:35:14,447 --> 00:35:19,646 and reptiles that lived in water were cushioned against extreme temperature changes. 426 00:35:23,167 --> 00:35:29,037 So the earth still retains representatives from all these animal groups. 427 00:35:30,487 --> 00:35:33,524 But for me, the most exciting thing about the dinosaurs 428 00:35:33,367 --> 00:35:35,756 is not how they died, but how they lived. 429 00:35:36,247 --> 00:35:40,286 Their dynasty, after all, lasted for nearly 200 million years, 430 00:35:40,567 --> 00:35:44,845 compared with a mere two or three million years that human beings have been on earth. 431 00:35:44,887 --> 00:35:47,560 When the hadrosaurs were at the height of their success, 432 00:35:47,767 --> 00:35:52,397 much of North America was covered with swamps very like these. 433 00:35:54,967 --> 00:35:57,606 In the 64 million years since then, 434 00:35:57,847 --> 00:36:00,680 the shallow seas that covered much of North America 435 00:36:01,207 --> 00:36:04,199 drained away from the margins of the continent. 436 00:36:04,087 --> 00:36:07,477 Rivers deposited layers of mud over the fallen trees 437 00:36:07,927 --> 00:36:11,761 and finally the swamps became dry land. 438 00:36:15,127 --> 00:36:22,124 This is the richest dinosaur graveyard in the world, Drumheller in Alberta, Canada. 439 00:36:27,927 --> 00:36:33,843 This light-coloured rock is composed of sand that was laid down in a river channel. 440 00:36:34,167 --> 00:36:37,079 The dark layer at the top is the remains of mud 441 00:36:37,047 --> 00:36:40,437 deposited when the whole area was submerged in a flood. 442 00:36:40,647 --> 00:36:43,445 It's in between these layers in these particular cliffs 443 00:36:43,527 --> 00:36:47,236 that dinosaur bones are most commonly found. 444 00:36:56,047 --> 00:37:00,882 Almost 500 skeletons of 50 different species have come from these cliffs, 445 00:37:00,847 --> 00:37:04,635 the remains of a whole community of dinosaurs. 446 00:37:08,047 --> 00:37:11,278 And here, too, in the Tyrrell Museum of Palaeontology 447 00:37:11,247 --> 00:37:16,526 more of them have been reconstructed and displayed than anywhere else in the world. 448 00:37:22,567 --> 00:37:25,320 They daily astonish thousands of visitors, 449 00:37:25,447 --> 00:37:28,086 who come both to marvel at the bones 450 00:37:28,327 --> 00:37:33,321 and to learn about the vanished lives of these spectacular animals. 451 00:37:46,527 --> 00:37:53,797 So today, less than 200 years since we discovered that these animals even existed, 452 00:37:54,207 --> 00:37:59,600 we've learnt so much about them that we can almost hear the champ of these huge jaws, 453 00:37:59,487 --> 00:38:04,083 visualise the glint in the eye that once revolved in this empty socket, 454 00:38:04,287 --> 00:38:09,122 clothe this immense skeleton with leathery skin and muscles 455 00:38:09,567 --> 00:38:15,324 and picture in our imaginations in almost as much detail as if they were alive today 456 00:38:15,247 --> 00:38:19,798 these bellowing, battling, browsing, 457 00:38:20,047 --> 00:38:24,006 nesting, courting, scavenging, fighting creatures 458 00:38:24,367 --> 00:38:26,358 that disappeared from the earth 459 00:38:26,287 --> 00:38:30,883 over 50 million years before mankind appeared upon it.