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Documentary, Extinct: A Horizon Guide to Dinosaurs 2011
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00:00Dinosaurs. Masters of the planet for 160 million years.
00:17The biggest, baddest animals ever to walk the Earth.
00:23They had claws a foot long
00:25and enormous bone-crushing jaws with teeth the size of carving knives.
00:34Weighing up to 80 tonnes, the ground would literally shake when they moved.
00:43But how do we know so much about them?
00:46For over 40 years, Horizon and the BBC have followed the world's paleontologists
00:52on their quest to find out what these elusive creatures were really like.
00:58As a paleontologist, I love digging up the possibility of monsters of my childhood,
01:04looking for strange beasts that once roamed where I live now.
01:10Over time, with only bones and tiny fragments of information to go on,
01:15scientists have managed to piece together the complex jigsaw puzzle
01:18that is the life of the dinosaurs.
01:22There have been astonishing new finds,
01:25controversial theories,
01:28and extraordinary revelations about these giant reptiles.
01:33Quick, agile, fast-moving...
01:3515,000 pounds of gut-crunching terror.
01:37These tantalising clues and breakthrough new technology
01:45have enabled scientists to reach for the answers to the biggest questions of all.
01:50Do we really know what happened to the dinosaurs?
01:54And is there a chance that some might still be alive today?
01:57어떻게 what happened to the dinosaurs?
01:59We are now alive today.
02:02We are alive today.
02:08closed by李克勳
02:10Following the
02:21When Horizon first began reporting on dinosaurs over 40 years ago,
02:34paleontology was a science based on a lot of speculation
02:37and not that much evidence.
02:41Scientists really just had bits and pieces to go on.
02:47So it's hardly surprising that the dinosaurs we came to know and love
02:51were really just a mixture of fact and fantasy.
03:01The largest flesh eater the world has ever seen.
03:07I'm not afraid.
03:09All children now learn at an early age but are reluctant to believe
03:12that Tyrannosaurus and all the other dinosaurs followed a well-trod trail to oblivion.
03:17I see a little hole up in his nose.
03:20They've heard other stories about dinosaurs too, many of which are myths,
03:24replacing the fairy stories of earlier generations.
03:27For our limited knowledge of these prehistoric monsters provides numerous questions,
03:32but very few answers.
03:33I would like to get his mail.
03:36for years scientists had grappled with fundamental questions.
03:52They didn't know what dinosaurs ate,
03:55how they bred,
03:56sometimes they weren't even sure how the skeletons fitted together.
04:05They also couldn't work out whether one of the major groups of dinosaurs,
04:09the sauropods,
04:10lived on land or in water.
04:15But one of the first major finds covered by Horizon revealed evidence of sauropod behaviour frozen in time.
04:21Footprints
04:24In the bed of the Paloxy River in Texas are tracks made by dinosaurs 70 million years ago,
04:32when the hard limestone rock was mud.
04:34This is evidence that convinces the most doubting tourist.
04:37Some are tracks of the meat-eating dinosaurs,
04:44others of the heavy, long-necked, long-tailed dinosaurs.
04:48It is these which pose a problem.
04:50Where are the creatures who made these tracks swamp dwellers,
04:53or did they move around on land?
04:56Thirty years ago,
04:57the river was dammed and the tracks photographed and carefully plotted.
05:00The shallowness of the footprints and the absence of tail marks suggested a herd of the animals living in water sufficiently deep to keep their tails out of the mud.
05:11It's difficult to believe that such huge creatures, weighing up to 80 tons, could support themselves out of water.
05:19But here is evidence for just that, a tail mark.
05:22If these creatures could support themselves out of water on one occasion,
05:25couldn't they be ordinary land dwellers who occasionally ventured to the swamps?
05:30At the time, a single tail mark was not enough to convince the palaeontologists that sauropods were anything but aquatic.
05:42But as more skeletons were discovered,
05:44their similarities to animals living on land became clearer.
05:51So then we have long straight limbs and a long neck, adaptations,
05:55not for a hippo-like existence,
05:57but for living on land, feeding high on land trees.
06:02Scientists looked again at the fossil footprints,
06:06and turned to living animals to try and determine how fast the sauropods could move.
06:14Dinosaur bones are only one source of information, present-day animals are another.
06:19Neil Alexander is professor of zoology at Leeds University.
06:22His main research interest is analysing how animals move.
06:26Recently, he's found a way of applying his work to answering a seemingly impossible question.
06:32How fast did dinosaurs walk?
06:34On the beach at Southport, some vital evidence was laid out.
06:38These are replicas of some of the biggest footprints ever found.
06:45They're found in Texas, and they're not new footprints.
06:49They're footprints made something like a hundred million years ago, preserved as fossils.
06:54Now, these big fellows, these are the hind foot feet.
07:00It was a four-legged animal.
07:02And these hind feet are about three feet long.
07:05Stride length here of eight feet from right hind foot down to right hind foot down again.
07:14The dinosaur footprints are only part of the information needed.
07:17Now, something called a froude number has to be worked out.
07:21It's a mathematical formula relating the size of an animal's legs to the way its stride increases as it moves faster.
07:28Now, we're going along about five miles an hour, and the horse is walking.
07:34Each foot is moving in its own time. There are no two feet going together.
07:39We're going to speed up a bit, and then you will see the gait change.
07:44If we go up now to about ten miles an hour, there we are.
07:51The diagonally opposite feet are moving together.
07:57Now, if we speed up again and go further, there we are, going through a canter into a full gallop.
08:11In the gallop, we've got the two forefeet moving about together, the two hind feet moving again about together.
08:24And there we must be going at something like twenty miles an hour.
08:28Professor Alexander has studied dozens of animals, from tiny gerbils to huge elephants, and worked out their froude numbers.
08:37From these, he's able to estimate what the froude number for any animal of any size will be.
08:42And so we find out what the froude number is for the dinosaur, and how fast the dinosaur was going.
08:49And it's awful slow.
08:53Two miles an hour.
08:56Now, two miles an hour, that's a slow walk for a man.
09:01For something with legs three times as long as a man, it's a very slow walk indeed.
09:07Professor Alexander's work had reinforced the widely held view that dinosaurs were slow, lumbering reptiles.
09:18But the discovery of a new kind of dinosaur would change our thinking.
09:33We have right over here one that I discovered myself, which I think is one of the most interesting dinosaurs that's ever been found.
09:39In fact, I also think it's one of the most important dinosaurs ever found.
09:44Let me show you some very interesting things about this fellow.
09:47First of all, it's a carnivorous dinosaur, but not a big one like Tyrannosaurus.
09:52It's just a little fellow, probably about four or five feet high, maybe eight or nine feet in length.
09:59Weighed maybe about 175 pounds, about your weight or mine.
10:04One of the curious things about him is the construction of his foot.
10:09And the peculiar thing about this is the very large, sickle-like claw on the one toe.
10:15And remember that in addition to this long, bony claw, there was a horny sheath that fit over that,
10:23so that the total claw was probably half again as long.
10:26Obviously not designed for walking, and quite certainly an offensive weapon.
10:31This strange structure, which we had never seen before in any of the carnivorous dinosaurs,
10:36is the reason that I coined the name for this that I did.
10:39Terrible claw, Deinonychus.
10:41But he was a fellow I wouldn't want to meet on a dark street at night, I'll tell you.
10:48John Ostrom realised Deinonychus was a ground-breaking dinosaur,
10:52one that overturned long-held ideas about how they moved.
10:56So the picture that we get from Deinonychus seems to be completely different from the old picture that we had of dinosaurs,
11:03as sort of sluggish, sun-basking animals like modern lizards and turtles.
11:08Deinonychus seems to be a very quick, agile, fast-moving, two-legged predator.
11:13Good balance control means a high neurological development.
11:19This discovery is what sort of pushed me over the brink into looking at dinosaurs in a whole new light.
11:28Other dinosaurs, too, were suddenly seen as fast-moving, agile creatures.
11:33And Ostrom's new ideas about them developed like this.
11:40In the animal world, there's a major division.
11:43In one group, there are mammals, which are active, hot-blooded creatures.
11:47In the other are reptiles, which are generally less active and cold-blooded.
11:52Where do dinosaurs fit?
11:54Since, like mammals, they were very active, Ostrom reasoned perhaps they were hot-blooded, too.
12:00This idea was revolutionary.
12:08Was it really possible that dinosaurs, ancient reptiles, could be warm-blooded?
12:19It would be another 30 years before deep bone analysis revealed that he might be right.
12:25For years, paleontologists have been looking at the outsides of dinosaurs.
12:37On the outsides, we can understand how dinosaurs evolved and how their anatomy changed over time.
12:42But deep inside the bones, we can actually trace dinosaur life.
12:46By analyzing thin cross-sections of fossilized dinosaur bone, Christy Curry-Rogers is helping to rewrite what we know about dinosaurs from the inside out.
12:58I think let's go with this one and this smaller one.
13:03Those two look good.
13:04Okay.
13:05One of the things that we see when we crack open dinosaur bones is a story of a very fast growth rate throughout life history.
13:17We see that dinosaurs were growing very, very quickly on par with modern mammals and birds, not like reptiles at all.
13:25This is a great example from a young apatosaurus, a young, large sauropod dinosaur.
13:32All of these white spaces that we see here are places where blood vessels used to flow through this bone when the animal was still alive.
13:38And this is completely different than the bone that we might see of a reptile like a crocodile or a turtle.
13:43Instead, this is a lot more similar to those bones of mammals and birds.
13:47What she's discovered from deep within the dinosaur bones has reinforced the idea that at least some of them were warm-blooded.
13:56Dinosaurs, just like other modern animals, probably were fairly well adapted for whatever thermoregulatory strategy.
14:04I think that they were perfectly well adapted to deal with the problems of maintaining a body temperature.
14:10Advances in technology were allowing scientists to break new ground, proving that dinosaurs weren't just giant lizards, but a truly unique kind of reptile.
14:27But like a detective looking for clues, finding a whole dinosaur skeleton was the paleontologist's dream.
14:34And in 1990, an American fossil hunter hit the jackpot.
14:38For Pete Larson and his then-girlfriend Susan, the day had started as an ordinary, everyday fossil hunt.
14:53We were out actually digging on a triceratops skull that my ten-year-old son Matthew had found.
14:59And we were just having a grand old time. It was a very, very nice, small triceratops skull.
15:03And all of a sudden Susan walked up with a couple bone fragments.
15:07And I said, is there more? And she said, there's lots more.
15:14Nothing could have prepared them for what they'd found.
15:17I looked up the face of the cliff and I saw an expanse about eight feet wide and perhaps two feet deep with bones jutting out everywhere.
15:28And as I crawled up to the top of this exposure, I saw three articulated vertebrae.
15:34I knew that they had to come from a T-Rex because of the size of the curve of those bones.
15:44They were obviously parts of a vertebrae from a meat-eating dinosaur.
15:48And when I saw those three articulated vertebrae, I knew this was going to be the most important specimen that we'd ever dug on.
15:57I just knew it.
16:01Pete Larsen marveled at the size of the partially exposed killer dinosaur.
16:08And nicknamed it Sue after his girlfriend.
16:11It was like clawing our way to the top of Mount Everest.
16:17And as we were uncovering it, we could see the top.
16:20And as we got her out of the ground, we were there.
16:23We had climbed the Mount Everest of paleontology.
16:34We got the biggest, baddest of all the T-Rexes that ever was.
16:41And it got even better.
16:45Sue was extremely well preserved and nearly complete.
16:48Exactly what Pete Larsen had dreamed of finding.
16:53At long last, here was a chance to study the world's ultimate killing machine in extraordinary detail.
16:59And all from just this one specimen.
17:11Deep within Sue's well-preserved skull, scientists were about to discover something they'd never seen before.
17:16Deep within Sue's well-preserved skull, scientists were about to discover something they'd never seen before.
17:40And cutting-edge technology would allow them to see it in exquisite detail.
17:53Basically, when it comes down to it, I was told to describe the thing inside and out.
17:56I took that literally. I knew they wouldn't let me break the skull apart.
18:01So, CT scanning is the answer.
18:08CT scanning is an advanced X-ray imaging technique.
18:11It allowed Chris Brochu to build up computer images of slices through the head, which he moulded together to produce a three-dimensional likeness of a T-Rex skull.
18:23Then, painstakingly, millimeter by millimeter, he followed the contours on the inside of this skull to reveal the structure of a T-Rex brain.
18:41The first time I saw the individual slices themselves, they didn't seem all that exciting.
18:57It wasn't until I built the first animation, the first flip through a bunch of slices all going through the skull.
19:03That was when it really struck me that there were a lot of things here to see.
19:10The CT scans revealed something scientists had never before been able to see in such detail.
19:20Protruding from the delicate network of brain tissue was the optic nerve.
19:25This nerve was responsible for relaying information from the eyes to the visual centers in the brain.
19:37And it was big enough to carry a lot of information.
19:43The scans seemed to confirm T-Rex did indeed have a key attribute of a skilled predator.
19:49It would have been able to seek out its prey at a distance and destroy it with the accuracy of an assassin.
20:04T-Rex could see its prey, but that didn't automatically make it an efficient killer.
20:10To get to grips with its enormous jaws, scientists devised a risky experiment.
20:14Lock jaw, lock jaw, lock jaw.
20:19Gators and crocodiles make a great model for studying the feeding biomechanics of extinct theropod dinosaurs.
20:25They have very similar musculature.
20:27And just the basic leverage of their jaws and things like that are actually just a good analogy for Tyrannosaur feeding.
20:36Okay, grab that pole.
20:37Watch your feet, watch your feet.
20:44Remember, she can run forward.
20:46Two feet. One, two, three.
20:48Go, go, go, go, go, go, go.
20:50Watch your feet, Grace.
20:52This is a female American crocodile, Stevie.
20:55A youngster at 31 years old, she's only half the size she could become.
21:00She may be small, but her strength is obvious.
21:03Bob has a tape. Stay in line with her. Back up, back up, back up, back up.
21:09Back up.
21:11Who's got a tape?
21:13She's heavy.
21:15Because her jaws are thought to work in a similar way to T-Rex jaws, Erickson plans to measure her bite to see what it may reveal about the power behind a T-Rex bite.
21:25Yet as she's small, and he's not tested her before, he has no idea what kind of results he'll get.
21:33Pull the leg out of that.
21:35I'm all set.
21:37Erickson needs to get the crocodile to crunch onto a specially designed pressure sensor, which will record the force of the bite.
21:45Everybody ready?
21:47The tricky bit is getting the timing right.
21:50The bite needs to be a spontaneous one.
21:53Okay, here we go. Hang on.
22:05819 pounds.
22:09Good bite.
22:10An 800-pound bite is comparable to what a lion could do, or a spotted hyena, which is the bone-crushing champion among mammals.
22:17So, a very small crocodilian is capable of doing bite forces equal to what some of these large carnivorine mammals do.
22:24If you've matched up an equal-sized crocodile, say, to a large lion, though, the crocodile will bite probably three times more forcefully.
22:31Watch your legs.
22:33If jaws like these give crocodiles a bite force well above what their weight implies, then Erickson believes the same must have been true of T-Rex jaws.
22:44Nice canine on the side.
22:45His work suggested the power of a T-Rex bite may have been on a scale beyond anything we have ever seen.
22:52It's not a natural thing to stick your hand inside the mouth of a crocodile, but I shouldn't try this at home, kids.
22:58To get an idea of how much more powerful, Erickson worked on doing more than just scale up the bite.
23:07Snout width is 14.2.
23:09He measured every physical detail of his crocodiles to try to map the differences in skull shape and body weight compared to an animal the size and shape of a T-Rex.
23:18Erickson's preliminary maximum estimate of a T-Rex bite could be as much as 40,000 pounds of force.
23:30That's about 50 times more powerful than our crocodile.
23:36T-Rex would have had easily the most powerful bite of any animal that has ever lived.
23:43The combination of new finds and advanced technology has enabled paleontologists to interpret fossils with greater certainty.
24:06We now know more than ever before about what dinosaurs looked like, how fast they grew, their skill as predators, and how they moved.
24:25All building a convincing picture of how the dinosaurs came to dominate the Earth for over 160 million years.
24:33160 million years is a pretty long time and makes dinosaurs some of the most successful animals ever to have walked the Earth.
24:49After all, modern humans have only been around for a couple of hundred thousand years.
24:53Now, evidence of dinosaur life fills the geological record.
24:56But then suddenly, 65 million years ago, it all disappeared.
25:01The dinosaurs vanished.
25:07Scientists spent years scrutinising dinosaur bones looking for answers.
25:12You got something? Yeah.
25:14This is a caudal vertebrae.
25:17Great.
25:18They struggled to come up with ideas to explain the mass extinction.
25:22Perhaps the climate deteriorated.
25:25Becoming too hot.
25:31Or too cold.
25:33Or suddenly too wet.
25:38Or too dry.
25:39There were problems maybe of reproduction.
25:47Or maybe their eggs were eaten by the tiny furry mammals.
25:52Maybe it was God's will.
25:54Or lack of standing room in the ark.
25:56But it was only when they turned their attention to rocks rather than bones that scientists had a breakthrough.
26:16Geologists searching for clues to the extinction discovered an unusual layer of clay in the geological record that marked the boundary between the time of the dinosaurs and the time of mammals.
26:31Nobel Prize winning physicist Luis Alvarez and his team took up the challenge.
26:37You see this clay layer here? It's about a half inch thick.
26:41That's when the dinosaurs went out.
26:42You really don't know how long it took, why it's there.
26:47And so I said, maybe some of the tricks that I know as a physicist might help unravel that story.
26:54And then we talked about it for the next couple of weeks and finally decided to look for iridium as a measure of the deposition rate.
27:05A small quantity of the metal iridium constantly falls to Earth from space and the team expected to find only trace amounts.
27:18But their tests showed something astonishing.
27:21There was so much iridium in the clay layer, there could only be one source.
27:25Alvarez's radical idea was that it had been brought to Earth by a meteorite.
27:36The vast majority of iridium-bearing meteorites started life as asteroids.
27:41Most of them, in an orbit between Mars and Jupiter, never come anywhere near the Earth.
27:45But the theory goes that a few are occasionally swung out of line by the enormous gravitational pull of Jupiter.
27:53A very few of these finish up in an orbit which crosses the Earth's.
27:58Most of the time they pass harmlessly by, but every now and then they collide.
28:02Alvarez's theory is that 65 million years ago, a huge asteroid, six miles wide, smashed into the Earth with devastating effects.
28:13It was this collision, he believes, that covered the Earth with iridium and wiped out the dinosaurs.
28:24It's not all that far-fetched. Only 25,000 years ago, a much smaller collision caused Meteor Crater in Arizona.
28:34There are larger impact craters on the Earth's surface. Many have been eroded away over time and are rather difficult to recognise.
28:42Nevertheless, so far, over the whole world, more than 200 have been identified.
28:47But none of these is both the right age and size for Alvarez's theory.
28:52However, there's an alternative. The asteroid may have landed in the sea.
28:57Dr. Cesare Emiliani.
28:59We have no evidence at all of a crater of the size that this asteroid should have made,
29:06either on land or on the ocean floor. This is a map that shows the structure of the ocean floor.
29:11On the other hand, we have quite a bit of evidence indicating that plant life on the continents
29:16in a broad area ranging from the Urals to the Rockies suffered somewhat at the end of the Cretaceous,
29:25while plant life west of the Urals, from the Urals to the Rockies around the North Atlantic,
29:31suffered very little or nothing at all. That would seem to indicate that the point of impact of the asteroid
29:39was somewhere between the Urals and the Rockies. Now, we have no crater on land.
29:42We have no crater on the visible ocean floor, on what we see now.
29:46But a portion of the ocean floor since then has disappeared under the continent,
29:51because the oceanic crust moves toward the continent that dives under the continent.
29:56There is a substantial chance that the asteroid might have hit an area of the ocean floor that has since disappeared.
30:03So, if one were to make a wild guess as to where the asteroid might have hit,
30:08one would say somewhere in the North Pacific, around here.
30:15Without finding a crater, it was hard to prove that it was an asteroid that had killed off the dinosaurs.
30:21But by 1997, scientists realised they'd been looking in the wrong place.
30:32A number of circular structures had been found in the Caribbean.
30:35The shape of islands, circular structures in the seafloor, circular geophysical anomalies.
30:44When you're looking for an impact crater, usually the obvious thing,
30:47because most craters are round, is looking for something big and round.
30:50One of Hildebrand's suspects was on the Yucatan Peninsula of Mexico.
30:57There, the state oil company, Petrolinas Mexicana,
31:01had detected a strange circular anomaly in the Earth's gravity field.
31:12Chicxulub, the dead centre of the big round hole.
31:16But at the surface, there's no sign of a catastrophe.
31:20The 200-kilometre-wide crater is hidden.
31:24It's buried hundreds of metres beneath the Earth's surface.
31:27So Hildebrand had to investigate it in some other way.
31:29We've taken another 1,400 measurements and combined them with the data
31:31that Petrolinas Mexicanos already had,
31:33to make this map of the gravity field.
31:35Here, you can see the data that Petrolinas Mexicanos has already had,
31:37to make this map of the gravity field.
31:39Here, you can see the data of the Earth's gravity field.
31:41The data that Petrolinas Mexicanos has already had,
31:45to make this map of the gravity field.
31:48Here, you can see all this concentric circular structure that represents the crater.
31:55From here to here, it's about 180 kilometres.
31:59Petrolinas Mexicanos had known about this big buried structure for decades.
32:02They had drilled several wells into it for oil exploration, beginning in 1952.
32:09When they did so, they found what they thought was volcanic rock, the stuff.
32:14But this contained shock quartz all through it and impact glass and so on.
32:19These are the classic signs, the deposits you'd expect in a big impact crater.
32:23The rock proved to be precisely 65 million years old, the age of the mass extinction.
32:30Here, at last, was the first confirmation that Shikshalup was ground zero.
32:33Hildebrand confirmed the theory proposed 17 years earlier that a devastating asteroid had hit the Earth 65 million years ago.
32:44By 2004, scientists believed they had proof that the impact had caused a massive explosion.
32:59quickly followed by an enormous shockwave that had destroyed life for hundreds of miles around.
33:08And there was more.
33:21Investigations of the layer of rock that marks the time when the dinosaurs disappeared, known as the KT boundary,
33:28revealed further evidence of what had happened in the aftermath.
33:32These are called spherules.
33:35They're actually made of round rock globules, so we know they're condensed from a very hot vapour cloud.
33:42And it also tells us, some of the mineralogy in there tells us,
33:46that these spherules, these globules originated at very high temperatures.
33:52Well, that's exciting. You know, something hot happened, and hot is associated with an impact.
34:00The spherules were evidence that the fireball had vapourised billions of tonnes of rock.
34:06In outer space, the vapour condensed into tiny droplets, which fell back all over the Earth as white-hot spherules.
34:16From America to New Zealand, there seemed to be evidence of massive burning at the time of the impact.
34:26It looked as if the world's forests had spontaneously ignited,
34:31as the rain of spherules heated the atmosphere by up to 1,000 degrees centigrade.
34:35If we're looking at 600, 1,000 degrees, then this would instantly have ignited all the plant matter across the world,
34:46and it just would have been sent up in flames.
34:49The impact was also thought to have created a deluge of vicious acid rain.
34:56The fireball had released chemicals which turned the water deadly.
35:05It was suggested that the acid rain had a pH so low that it was like battery acid.
35:09And if you had something that low in pH, it would literally burn everything on the land,
35:14from plants to the dinosaurs to everything else.
35:20Then there was the final clue from the K-T boundary.
35:23A high concentration of fern spores.
35:31Ferns flourish whenever all other plants have been killed off by some environmental devastation.
35:36So the predominance of fern spores, known as a fern spike, suggested something had wiped out every plant on the planet.
35:51Fern spikes were found all over the world, such as in New Zealand.
35:55And this, I think, became stronger and stronger evidence that there was something like global darkness caused by an impact.
36:01So the theory grew up that vast amounts of dust created by the impact must have blocked out the sun.
36:11This could have plunged the world into freezing darkness for months or years.
36:19Any dinosaurs which had escaped burning either froze or starved to death.
36:24The mystery surrounding the death of the dinosaurs finally appeared to have been solved.
36:43A number of factors may have influenced the extinction,
36:46but research had shown that the impact at Chicxulub was the crucial factor.
36:54We should probably be thankful for that mighty asteroid, because if the dinosaurs hadn't been wiped out,
37:05then mammals may never have flourished and we might not exist.
37:09So what would have happened if an asteroid hadn't hit the Earth and the dinosaurs had survived?
37:14Well, it's a thought that's given rise to some fairly novel ideas.
37:17I think that some dinosaurs, like some mammals, would have become increasingly intelligent at a geometric rate, as did our own ancestors.
37:27And I think, possibly, by this time, the dinosaurs themselves would have approached our own level of brain development.
37:33Ron Sagan, a sculptor at our museum, and myself have collaborated over the last several months in trying to estimate what the appearance of one of these highly encephalized or intelligent dinosaurs might have been,
37:45a dinosaur for the 1980s, and here is an example of what we think it may have looked like.
37:50Their model of a 20th century dinosaur incorporates many features of the original reptiles.
38:02The binocular vision, the absence of an external ear, a deep chest cavity with ribs all the way down the abdomen,
38:10opposable fingers, and no external genitalia.
38:12But it looks closer to a human being than a brontosaurus. In building it, have they, perhaps, unwittingly favored our own kind?
38:20I don't think so. I think just as the birds and the bats and the flying reptiles all have a crudely avian form,
38:28I think so, too, there is a meaning to the human form, so that we are, in effect, adapted to interact with an environment as highly encephalized bipeds or walking animals with a very large brain.
38:41So, perhaps, if it were not for a chance collision with an asteroid, creatures very like this could be ruling the world today,
38:48just as they did all those millions of years ago.
38:53Let's imagine, perhaps, that the dinosaurs really did become some sort of dinosauroid.
38:57The great rock doesn't fall out of the sky. It's a bright light in the sky. The dinosaur says, what's that? No idea.
39:03The mass extinction is postponed. In fact, it's cancelled. So, what's happening then? We've got the apes rapidly evolving.
39:09And then they're beginning to look over their shoulders because, just conceivably, there are also these dinosauroids doing rather similar things.
39:17And then, of course, it's fascinating to think what would have happened. Would it have been an evolutionary race?
39:22Maybe there would have been a winner? Or maybe, ultimately, unbelievably, madly, it could have been perhaps even a cooperation.
39:28The utopian notion of dinosaurs and humans sharing the planet may appeal, even be plausible, to some.
39:38But most paleontologists see the dinosauroid as an insult to dinosaurs.
39:42There's probably some good ideas there. The brain was getting bigger and they probably would have continued to out-compete other animals.
39:54But for them to become fully erect like humans, I think, is a little bit fanciful.
39:58Dinosaurs would have continued to develop. They would have continued to specialize. They would have adapted. But they would have adapted and specialized as dinosaurs. They wouldn't have become primates or primate-like.
40:11The idea that a dinosauroid could exist, as a scientific question, it's bogus. It's about as bogus as it gets.
40:20It is fairly arrogant to think that the endpoint of all evolutionary trajectories should sort of emulate human beings.
40:32If the asteroid had never hit, life on Earth could have been very different.
40:40But, of course, that's all just crazy speculation.
40:55Everybody now knows that the dinosaurs were wiped out 65 million years ago and none of them survived that catastrophic asteroid impact.
41:03Or did they?
41:04The idea that dinosaurs may have evolved into something else is one that had been doing the rounds for many years.
41:10But it began to gather momentum when some paleontologists began to increasingly suspect that dinosaurs might still be alive.
41:17The Natural History Museum London.
41:35Within these hallowed halls lies the fossil that first hinted at the origin of birds.
41:43Discovered in Germany a hundred years ago, superstitious quarry workers thought it was a fallen angel.
41:49Archaeopteryx turned out to be something almost as remarkable.
42:02The size of a pigeon, it possessed teeth, a long bony tail and claws on its arms, all features of reptiles.
42:09At the same time, it was very much like a bird.
42:15It actually has impressions of the wing feathers, both wings, and long tail feathers.
42:23But the tail has a long set of bones running down it as well, which modern birds don't have at all.
42:28So Archaeopteryx really does seem to be a primitive bird.
42:34These fossils, I still find it very exciting to look at them because they have so much scientific information contained in them,
42:42but they're very beautiful objects to look at in their own right.
42:45And they really are an exceptional snapshot record of evolution.
42:48That fossil was to be the key to something that John Ostrom had been thinking about for decades.
43:01When he'd first described Deinonychus in the 1960s,
43:06he'd noticed that its skeleton was strangely similar to that of a bird.
43:12Archaeopteryx helped him refine his ideas.
43:15Neat animal, isn't it?
43:19I think so.
43:21And what made me even more excited was when I saw structures in that animal
43:28that I subsequently recognized in Archaeopteryx.
43:33So this is the Sonhofen Archaeopteryx?
43:36This is what I call a Sonhofen specimen, yeah.
43:39John Ostrom's crucial realization was that his beloved Deinonychus
43:43shared many anatomical features with Archaeopteryx.
43:48He compared in detail the skeletons of predatory dinosaurs, Archaeopteryx and modern birds.
43:54He found a whole set of similarities, most notably in the skull, the hind limbs and the forearms.
44:02For a start, they all have the same number of fingers.
44:05This is a skeleton of a modern pigeon.
44:08Three fingers in the hand of a modern bird, three fingers preserved in the hand of Deinonychus.
44:16And that particular kind of hand morphology is also supplemented by the strange wrist bone that allows for the flexibility that produces the flapping strokes.
44:29The similarities between birds and the predaceous dinosaurs is amazing for me.
44:42But, as with all groundbreaking new theories, Ostrom's idea had its detractors.
44:47The dinosaur-bird theory has tremendous popular appeal.
44:54One can vicariously study dinosaurs at the backyard bird feeder.
44:58And one can go get a piece of dinosaur leg at the local Kentucky Fried Chicken.
45:05So it has tremendous appeal to the public.
45:08Unfortunately, it seems to be wrong.
45:10Alan Faduccia argued that birds evolved long before dinosaurs came along.
45:17They descended from much more primitive reptiles.
45:20And any similarities between birds and predatory dinosaurs were superficial.
45:25They resembled each other because they both walked on their hind legs, not because they were closely related.
45:30Such vocal sceptics were going to need better proof if they were to be convinced of the dinosaur-to-bird theory.
45:50And in 1999 in Tucson, Arizona, fossil collectors thought they might have come across a specimen that fitted the bill.
45:57I carried it out to the light of the sunlight so that I could see it cross-lit.
46:14And there were a number of beautiful teeth in this skull.
46:18And that was very exciting.
46:19And then we studied also the tail that was a dinosaur, very dinosaur-like tail.
46:27I got this incredible high feeling.
46:30It is the feeling of discovery, that wonderful time when everything clicks into position.
46:38The two fossil dealers thought they could be looking at one of the most important fossils ever found.
46:43A specimen that would prove beyond doubt one of the most controversial theories in all of evolution.
46:51This fossil, this clearly cross between a bird and a dinosaur, was what everybody had been looking for.
47:00And here it was, right there, right in front of my eyes, and I was one of the first people to see it.
47:03I looked it over very carefully, literally under a magnifying glass.
47:10And I was looking for any tell-tale features, particularly on the tail.
47:14I wanted to look at that tail very carefully because it was clearly, clearly a dinosaur tail.
47:18The world of paleontology was gripped and a team of experts was assembled to investigate.
47:35After several months, they confirmed that it was the missing link.
47:39It had a bird-like front and legs and a dinosaur-like tail.
47:42They called it Archaeoraptor, ancient hunter, and proudly presented it to the world.
47:56Scientists could now say that dinosaurs evolved into birds.
48:00One of the most important theories in evolution was finally proved.
48:04But not everyone was convinced.
48:20At the University of Texas, Tim Rowe had used a CAT scan to study the fossil.
48:26The results threw up some serious questions about how it fitted together.
48:31I'm going to show you two slices.
48:33The first is this slice here through the skull and these other elements here.
48:38And the second slice will be back through the ankle and through the tail,
48:41through this critical region here, through one of the legs.
48:45And when we go to these slices, here's what we see.
48:49Here's the skull.
48:51And we can see the skull is part of this upper layer of shale.
48:55And with this, you can see the fracture pattern here.
48:59Here are some very tight fractures that fit together.
49:01Here are a pair of curved fractures that fit together.
49:03One fitting against the next, a straight fracture.
49:06The pieces on either side are the same thickness.
49:08They're the same density.
49:10But when we get out here to the very edge of the block,
49:12this piece is a little bit thicker than the piece it's glued against.
49:16It's also a little denser than the piece it's glued against.
49:19Now, as we move down to the tail, to the critical area,
49:21we can see that it's completely surrounded by grout.
49:26And that there are no natural ties between the tail piece and this piece to the right,
49:30or this piece to the left.
49:32In fact, it's just swimming in this ocean of grout here.
49:35And as we map through the entire specimen,
49:37we found that there are no verifiable fits between the tail and any of the other parts anywhere else in the specimen.
49:49The scan clearly showed what the naked eye couldn't see.
49:52There was no natural skeletal link between the all-important tail and the rest of the fossil.
49:59It had simply been glued on with grout.
50:02The vital evidence that seemed to prove the link between birds and dinosaurs was a fake.
50:22The dinosaur fake was a dreadful blow for supporters of the bird theory.
50:26But scientists who were committed to the idea refused to give up.
50:29They were determined to keep looking for proof.
50:35Although the fossil had been a fake,
50:38its front half was a new kind of primitive bird.
50:42Fossil hunters flocked to the region where it had been found.
50:47And they struck gold.
50:59Extraordinary, well-preserved fossils revealed dinosaurs and birds not only shed features like downy feathers,
51:06but also hollow bones and similar pelvises and hind limbs.
51:09On a remote farm in Colorado,
51:13paleontologist Brent Breithaupt presented even more proof of the close relationship between the ancient fossils and birds.
51:18Very good.
51:19That should make an excellent track.
51:20Here we have two tracks that we recently made.
51:21This one here is from the Red Gulch dinosaur track.
51:23Here we have two tracks that we recently made.
51:24This one here is from the Red Gulch Dinosaur Track site.
51:27This one here preserves the red gulch dinosaur.
51:28Here we have two tracks that we recently made.
51:33This one here is from the Red Gulch Dinosaur track site.
51:37Very good, that should make an excellent track.
51:44Here we have two tracks that we recently made.
51:48This one here is from the Red Gulch dinosaur track site.
51:52This one here preserves the three-toe impressions, the tridactyl impressions of the foot of
51:59the dinosaurs, the small to medium sized theropod dinosaurs that lived up there.
52:05Now over here, we have one that we just got from this site, again, a nice tridactyl footprint.
52:14Again, very well preserved.
52:17If we compare both of these casts, we can see these particular tracks look very, very much
52:23the same.
52:25But these footprints are not those of a theropod that died over 65 million years ago.
52:32These are only a few hours old.
52:37There's dinosaurs in them, there are hills.
52:41In fact, dinosaurs are everywhere.
52:54For the first time on network television, paleontologist Julia Clark is about to perform an autopsy on
53:01a dinosaur.
53:03Only, you are more likely to know it as a roast turkey.
53:11Because you see, birds are dinosaurs.
53:18So today we're going to dissect the evidence that birds are living dinosaurs from this turkey.
53:24What we're pulling off here is the major flight muscle, the super coracoidus that is in Velociraptor
53:34and Oviraptor.
53:37One of the features you see is that the second finger is the longest.
53:41And this is a feature we see going back as far as early dinosaurs.
53:46You know, even Triassic forms.
53:50Of course, we're all familiar with wishbones from any kind of turkey meal.
53:59But wishbones actually are one of the kind of most intuitive pieces of evidence that birds
54:05are living dinosaurs.
54:07Because we have wishbones now from a whole variety of theropod dinosaurs including relatives
54:12of Tyrannosaurus and Velociraptor and even earlier dinosaurs such as Coelophysis.
54:18Yes, just as we share 98% of our DNA with chimps, turkeys, in fact all modern birds, are direct
54:32descendants of theropod dinosaurs.
54:44And the freshly made dinosaur tracks in the hills of Colorado, emus, inwardly, outwardly,
54:57even in the way they move.
54:59The similarities between theropod dinosaurs and birds are numerous.
55:04But being warm-blooded, their ultimate success was in an evolutionary solution to the need
55:10to keep warm.
55:12Large dinosaurs really don't have a problem with body heat.
55:15Basically, if they have a problem, it's getting rid of excess body heat.
55:18But small dinosaurs have this problem.
55:21They're losing their heat all the time.
55:23So it would be a good thing if a small dinosaur was warm-blooded for it to have some kind of
55:28insulation on its body.
55:31It started with the development of thin, downy filaments.
55:35In time, those filaments strengthened and thickened.
55:39As non-flying birds, emus are perhaps one of the best examples of feathers as they were
55:44originally designed, as an insulating layer.
55:49Once you have those long feathers, then, of course, it does give you an aerodynamic advantage
55:54as well.
55:56If you have that advantage, then selection starts working on that advantage.
56:00And it may well be that that was forcing these feathers to become longer and longer until
56:05finally that animal not only jumped across the ditch, it actually flapped its arms and
56:09flew across the ditch.
56:11And so it seems that flight, far from being the reason for the evolution of feathers, may
56:16have been a byproduct.
56:17But with it, some dinosaurs were already adapting in ways that would equip them for life after
56:23the meteorite impact.
56:28The fact of the matter is that the age of the dinosaurs never actually ended.
56:33Dinosaurs did survive the cataclysmic event of 65 million years ago.
56:38So when we talk about dinosaurs living with us today, and the fanciful notion of what it
56:45would be like, it's not so much fantasy.
56:49They're right there.
56:50The dinosaurs have not only survived, there are far more species of them on the earth today
56:54than there are mammals.
56:55They're not the biggest animals anymore, but still there's over 10,000 living species of
57:01descendants of dinosaurs.
57:03They didn't actually go extinct at the end of the Cretaceous period like everybody thinks.
57:07If we're outside flying around, we can't go into a forest without hearing dinosaurs.
57:15So in that sense, maybe they actually won out, and we just think we're on top.
57:28Over the last half century, scientists have hunted all over the world for new clues to help them
57:33piece together the fragments which reveal the life of the dinosaurs.
57:38They've come up with ingenious new ways of working out how the dinosaurs lived and behaved,
57:46made extraordinary discoveries, and battled to answer some of the oldest, most vital questions
57:54of all.
57:59There are still things that we don't know.
58:02There are mysteries to be solved.
58:04And one of the exciting things about paleontology is that in an instant, perhaps with just the
58:08tiniest of discoveries, everything that we think we know about dinosaurs today could all
58:13change again.
58:15There are always new discoveries out there waiting to be found.
58:28BBC iPlayer has the whole series of the captivating, shocking, and breathtaking Blue Planet live
58:34available now.
58:35And David Attenborough is on BBC Two tomorrow with the intriguing story of a German horse that
58:40was declared a maths genius.
58:42Natural Curiosities at seven.
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