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Dinosaurs. | 0:00:07 | 0:00:08 | |
Masters of the planet for 160 million years. | 0:00:08 | 0:00:13 | |
The biggest, baddest animals ever to walk the Earth. | 0:00:17 | 0:00:20 | |
They had claws a foot long. | 0:00:22 | 0:00:25 | |
And enormous, bone-crushing jaws | 0:00:25 | 0:00:28 | |
with teeth the size of carving knives. | 0:00:28 | 0:00:31 | |
Weighing up to 80 tons, the ground would literally shake when they moved. | 0:00:34 | 0:00:39 | |
But how do we know so much about them? | 0:00:43 | 0:00:45 | |
For over 40 years, Horizon and the BBC have followed | 0:00:46 | 0:00:50 | |
the world's palaeontologists on their quest to find out | 0:00:50 | 0:00:54 | |
what these elusive creatures were really like. | 0:00:54 | 0:00:56 | |
As a palaeontologist, I love digging up the possibility | 0:00:58 | 0:01:01 | |
of monsters of my childhood, | 0:01:01 | 0:01:03 | |
looking for strange beasts that once roamed where I live now. | 0:01:03 | 0:01:07 | |
Over time, with only bones and tiny fragments of information | 0:01:10 | 0:01:13 | |
to go on, scientists have managed to piece together | 0:01:13 | 0:01:16 | |
the complex jigsaw puzzle that is the life of the dinosaurs. | 0:01:16 | 0:01:21 | |
There have been astonishing new finds, | 0:01:21 | 0:01:24 | |
controversial theories... | 0:01:24 | 0:01:26 | |
And extraordinary revelations about these giant reptiles. | 0:01:28 | 0:01:32 | |
Quick, agile, fast-moving. | 0:01:32 | 0:01:34 | |
15,000lbs of gut-crunching terror. | 0:01:34 | 0:01:37 | |
These tantalising clues and breakthrough new technology have enabled scientists | 0:01:40 | 0:01:45 | |
to reach for the answers to the biggest questions of all. | 0:01:45 | 0:01:49 | |
Do we really know what happened to the dinosaurs? | 0:01:49 | 0:01:53 | |
And is there a chance that some might still be alive today? | 0:01:53 | 0:01:57 | |
When Horizon first began reporting on dinosaurs over 40 years ago, | 0:02:29 | 0:02:33 | |
palaeontology was a science based on a lot of speculation | 0:02:33 | 0:02:37 | |
and not that much evidence. | 0:02:37 | 0:02:39 | |
Scientists really had just bits and pieces to go on. | 0:02:41 | 0:02:45 | |
So it's hardly surprising that the dinosaurs we came to know and love | 0:02:47 | 0:02:52 | |
were really just a mixture of fact and fantasy. | 0:02:52 | 0:02:55 | |
The largest flesh eater the world has ever seen. | 0:03:02 | 0:03:05 | |
I'm not afraid! | 0:03:07 | 0:03:08 | |
All children now learn at an early age, | 0:03:08 | 0:03:11 | |
but are reluctant to believe that tyrannosaurus | 0:03:11 | 0:03:13 | |
and all the other dinosaurs followed a well-trod trail to oblivion. | 0:03:13 | 0:03:18 | |
I see a little hole up in his nose. | 0:03:18 | 0:03:20 | |
They've heard other stories about dinosaurs too, | 0:03:20 | 0:03:23 | |
many of which are myths, | 0:03:23 | 0:03:24 | |
replacing the fairy stories of earlier generations. | 0:03:24 | 0:03:27 | |
For our limited knowledge of these pre-historic monsters | 0:03:27 | 0:03:30 | |
provides numerous questions, but very few answers. | 0:03:30 | 0:03:35 | |
CHILDREN LAUGH | 0:03:35 | 0:03:37 | |
Look at that. Nine feet tall. What a monster. | 0:03:40 | 0:03:44 | |
For years, scientists had grappled with fundamental questions. | 0:03:48 | 0:03:52 | |
They didn't know what dinosaurs ate, how they bred. | 0:03:52 | 0:03:56 | |
Sometimes they weren't even sure how the skeletons fitted together. | 0:03:58 | 0:04:02 | |
They also couldn't work out | 0:04:04 | 0:04:06 | |
whether one of the major groups of dinosaurs, | 0:04:06 | 0:04:09 | |
the sauropods, lived on land or in water. | 0:04:09 | 0:04:13 | |
But one of the first major finds covered by Horizon | 0:04:15 | 0:04:18 | |
revealed evidence of sauropod behaviour frozen in time. | 0:04:18 | 0:04:21 | |
Footprints. | 0:04:23 | 0:04:24 | |
In the bed of the Paluxy river in Texas are tracks made | 0:04:26 | 0:04:29 | |
by dinosaurs 70 million years ago, | 0:04:29 | 0:04:32 | |
when the hard limestone rock was mud. | 0:04:32 | 0:04:35 | |
This is evidence that convinces the most doubting tourist. | 0:04:35 | 0:04:39 | |
Some are tracks of the meat-eating dinosaurs, | 0:04:41 | 0:04:45 | |
Others of the heavy, long-necked, long-tailed dinosaurs. | 0:04:45 | 0:04:48 | |
It is these which pose a problem. | 0:04:48 | 0:04:50 | |
Were the creatures who made these tracks swamp dwellers, | 0:04:50 | 0:04:54 | |
or did they move around on land? | 0:04:54 | 0:04:56 | |
30 years ago, the river was dammed and the tracks photographed | 0:04:56 | 0:04:59 | |
and carefully plotted. The shallowness of the footprints | 0:04:59 | 0:05:03 | |
and the absence of tail marks suggested a herd of the animals | 0:05:03 | 0:05:07 | |
living in water sufficiently deep to keep their tails out of the mud. | 0:05:07 | 0:05:10 | |
It's difficult to believe that such huge creatures | 0:05:10 | 0:05:13 | |
weighing up to 80 tons could support themselves out of water. | 0:05:13 | 0:05:17 | |
But here is evidence for just that, a tail mark. | 0:05:19 | 0:05:22 | |
If these creatures could support themselves out of water | 0:05:22 | 0:05:25 | |
on one occasion, couldn't they be ordinary land dwellers | 0:05:25 | 0:05:28 | |
who occasionally ventured to the swamps? | 0:05:28 | 0:05:30 | |
At the time, a single tail mark was not enough to convince | 0:05:33 | 0:05:36 | |
the palaeontologists that sauropods were anything but aquatic. | 0:05:36 | 0:05:42 | |
But as more skeletons were discovered, | 0:05:42 | 0:05:45 | |
their similarities to animals living on land became clearer. | 0:05:45 | 0:05:48 | |
So then we have long straight limbs and a long neck, | 0:05:50 | 0:05:54 | |
adaptations not for a hippo-like existence, | 0:05:54 | 0:05:56 | |
but for living on land, feeding high on trees. | 0:05:56 | 0:06:00 | |
Scientists looked again at the fossil footprints... | 0:06:01 | 0:06:04 | |
And turned to living animals to try and determine how fast | 0:06:05 | 0:06:08 | |
the sauropods could move. | 0:06:08 | 0:06:10 | |
Dinosaur bones are only one source of information. | 0:06:13 | 0:06:17 | |
Present day animals are another. | 0:06:17 | 0:06:20 | |
Neil Alexander is Professor of Zoology at Leeds University. | 0:06:23 | 0:06:27 | |
His main research interest is analysing how animals move. | 0:06:27 | 0:06:30 | |
Recently he's found a way of applying his work | 0:06:30 | 0:06:33 | |
to answering a seemingly impossible question. | 0:06:33 | 0:06:36 | |
How fast did dinosaurs walk? | 0:06:36 | 0:06:37 | |
On the beach at Southport, some vital evidence was laid out. | 0:06:37 | 0:06:41 | |
These are replicas of some of the biggest footprints ever found. | 0:06:41 | 0:06:45 | |
They were found in Texas, and they're not new footprints. | 0:06:45 | 0:06:49 | |
They're footprints made something like 100 million years ago, | 0:06:49 | 0:06:53 | |
preserved as fossils. | 0:06:53 | 0:06:55 | |
Now, these big fellows, these are the hind feet. | 0:06:55 | 0:07:00 | |
It was a four legged animal, | 0:07:00 | 0:07:02 | |
and these hind feet | 0:07:02 | 0:07:04 | |
are about three feet long. Stride length here of eight feet | 0:07:04 | 0:07:08 | |
from right hind foot down to right hind foot down again. | 0:07:08 | 0:07:11 | |
The dinosaur footprints are only part of the information needed. | 0:07:14 | 0:07:18 | |
Now something called a Froude number has to be worked out. | 0:07:18 | 0:07:21 | |
It's a mathematical formula relating the size of an animal's legs | 0:07:21 | 0:07:24 | |
to the way its stride increases as it moves faster. | 0:07:24 | 0:07:27 | |
Now we're going along at about five miles an hour, | 0:07:29 | 0:07:32 | |
and the horse is walking. | 0:07:32 | 0:07:34 | |
Each foot is moving in its own time. | 0:07:34 | 0:07:36 | |
There are no two feet going together. | 0:07:36 | 0:07:39 | |
We're going to speed up a bit, and then you'll see the gait change. | 0:07:40 | 0:07:45 | |
If we go up now to about ten miles an hour, there we are... | 0:07:45 | 0:07:50 | |
The diagonally opposite feet are moving together. | 0:07:52 | 0:07:57 | |
Now if we speed up again and go further, there we are... | 0:08:00 | 0:08:05 | |
Going through a canter into a full gallop. | 0:08:07 | 0:08:10 | |
In the gallop, we've got the two forefeet moving about together, | 0:08:10 | 0:08:16 | |
the two hind feet moving, again, about together. | 0:08:16 | 0:08:20 | |
And now we must be going at something like 20 miles an hour. | 0:08:24 | 0:08:27 | |
Professor Alexander has studied dozens of animals, | 0:08:30 | 0:08:33 | |
from tiny gerbils to huge elephants, and worked out their Froude numbers. | 0:08:33 | 0:08:37 | |
From these, he's able to estimate | 0:08:37 | 0:08:39 | |
what the Froude number for any animal of any size will be. | 0:08:39 | 0:08:42 | |
And so we find out what the Froude number is for the dinosaur, | 0:08:43 | 0:08:47 | |
and how fast the dinosaur was going. | 0:08:47 | 0:08:50 | |
And it's awful slow. | 0:08:52 | 0:08:54 | |
Two miles an hour. | 0:08:56 | 0:08:57 | |
Now, two miles an hour, that's a slow walk for a man. | 0:08:58 | 0:09:02 | |
For something with legs three times as long as a man, | 0:09:02 | 0:09:05 | |
it's a very slow walk indeed. | 0:09:05 | 0:09:08 | |
Professor Alexander's work had reinforced the widely held view | 0:09:11 | 0:09:15 | |
that dinosaurs were slow, lumbering reptiles. | 0:09:15 | 0:09:19 | |
But the discovery of a new kind of dinosaur | 0:09:25 | 0:09:28 | |
would change our thinking. | 0:09:28 | 0:09:30 | |
We have right over here one that I discovered myself, | 0:09:33 | 0:09:36 | |
which I think is one of the most interesting dinosaurs | 0:09:36 | 0:09:39 | |
that's ever been found. In fact, I also think | 0:09:39 | 0:09:42 | |
it's one of the most important dinosaurs ever found. | 0:09:42 | 0:09:45 | |
Let me show you some interesting things | 0:09:45 | 0:09:48 | |
about this fellow. First of all, it's a carnivorous dinosaur. | 0:09:48 | 0:09:51 | |
But not a big one like tyrannosaurus, | 0:09:51 | 0:09:53 | |
it's just a little fella, | 0:09:53 | 0:09:54 | |
probably about four or five feet high, | 0:09:54 | 0:09:58 | |
maybe about eight or nine feet in length. | 0:09:58 | 0:10:01 | |
Weighed maybe about 175 pounds, about your weight or mine. | 0:10:01 | 0:10:04 | |
One of the curious things about him is the construction of his foot. | 0:10:04 | 0:10:09 | |
And the peculiar thing about this is the very large, sickle-like claw | 0:10:09 | 0:10:14 | |
on the one toe. | 0:10:14 | 0:10:15 | |
And remember that in addition to this long bony claw, | 0:10:15 | 0:10:20 | |
there was a horny sheath that fit over that | 0:10:20 | 0:10:23 | |
so that the total claw was probably half again as long. | 0:10:23 | 0:10:26 | |
Obviously not designed for walking, | 0:10:26 | 0:10:28 | |
and quite certainly an offensive weapon. | 0:10:28 | 0:10:31 | |
This strange structure | 0:10:31 | 0:10:32 | |
which we had never seen before in any of the carnivorous dinosaurs | 0:10:32 | 0:10:37 | |
is the reason I coined the name for this that I did. Terrible claw. Deinonychus. | 0:10:37 | 0:10:41 | |
But he was a fella | 0:10:41 | 0:10:42 | |
I wouldn't want to meet on a dark street at night, I'll tell ya. | 0:10:42 | 0:10:46 | |
John Ostrum realised Deinonychus was a ground-breaking dinosaur, | 0:10:48 | 0:10:53 | |
one that overturned long-held ideas about how they moved. | 0:10:53 | 0:10:56 | |
So the picture that we get from Deinonychus | 0:10:56 | 0:10:59 | |
seems to be completely different | 0:10:59 | 0:11:01 | |
from the old picture that we had of dinosaurs as sort of sluggish, | 0:11:01 | 0:11:04 | |
sun-basking animals like modern lizards | 0:11:04 | 0:11:07 | |
and turtles. Deinonychus seems to be a very quick, agile, | 0:11:07 | 0:11:11 | |
fast-moving, two-legged predator. | 0:11:11 | 0:11:13 | |
Good balance control means a high neurological development. | 0:11:13 | 0:11:19 | |
This discovery is what sort of pushed me over the brink | 0:11:19 | 0:11:22 | |
into looking at dinosaurs in a whole new light. | 0:11:22 | 0:11:24 | |
Other dinosaurs too were suddenly seen as fast-moving, agile creatures. | 0:11:29 | 0:11:32 | |
And Ostrum's new ideas about them developed like this. | 0:11:37 | 0:11:41 | |
In the animal world, there's a major division. In one group, | 0:11:41 | 0:11:45 | |
there are mammals which are active, hot-blooded creatures. | 0:11:45 | 0:11:48 | |
In the other are reptiles, which are generally less active | 0:11:48 | 0:11:51 | |
and cold-blooded. | 0:11:51 | 0:11:53 | |
Where do dinosaurs fit? | 0:11:53 | 0:11:55 | |
Since like mammals, they were very active, | 0:11:55 | 0:11:57 | |
Ostrum reasoned perhaps they were hot-blooded too. | 0:11:57 | 0:12:01 | |
This idea was revolutionary. | 0:12:06 | 0:12:08 | |
Was it really possible that dinosaurs, | 0:12:08 | 0:12:10 | |
ancient reptiles, could be warm-blooded? | 0:12:10 | 0:12:14 | |
It would be another 30 years before deep bone analysis | 0:12:19 | 0:12:22 | |
revealed that he might be right. | 0:12:22 | 0:12:25 | |
For years, palaeontologists have been looking | 0:12:34 | 0:12:36 | |
at the outsides of dinosaurs. | 0:12:36 | 0:12:38 | |
+On the outsides, we can understand how dinosaurs evolved | 0:12:38 | 0:12:41 | |
and their anatomy changed over time, | 0:12:41 | 0:12:43 | |
but deep inside the bones, we can trace dinosaur life. | 0:12:43 | 0:12:46 | |
By analysing thin cross-sections of fossilised dinosaur bone, | 0:12:48 | 0:12:52 | |
Kristi Curry Rogers is helping to rewrite | 0:12:52 | 0:12:55 | |
what we know about dinosaurs from the inside out. | 0:12:55 | 0:12:58 | |
I think let's go with this one. | 0:12:58 | 0:13:01 | |
And the smaller one. | 0:13:01 | 0:13:02 | |
-Those two look good. -OK. | 0:13:02 | 0:13:05 | |
One of the things we see | 0:13:08 | 0:13:10 | |
when we crack open dinosaur bones is a story of a very fast growth rate | 0:13:10 | 0:13:16 | |
throughout life history. We see that dinosaurs | 0:13:16 | 0:13:20 | |
were growing very, very quickly on a par with modern mammals and birds, | 0:13:20 | 0:13:24 | |
not like reptiles at all. | 0:13:24 | 0:13:25 | |
This is a great example from a young Apatosaurus, | 0:13:27 | 0:13:30 | |
a young, large sauropod dinosaur. | 0:13:30 | 0:13:32 | |
All of these white spaces we see are places where blood vessels | 0:13:32 | 0:13:35 | |
used to flow through this bone when the animal was still alive. | 0:13:35 | 0:13:38 | |
This is completely different than the bone | 0:13:38 | 0:13:40 | |
we might see of a reptile, like a crocodile, or a turtle. | 0:13:40 | 0:13:43 | |
Instead this is lot more similar to those bones of mammals and birds. | 0:13:43 | 0:13:46 | |
What she's discovered from deep within the dinosaur bones | 0:13:46 | 0:13:51 | |
has reinforced the idea that at least some of them were warm-blooded. | 0:13:51 | 0:13:55 | |
Dinosaurs, just like other modern animals, | 0:13:56 | 0:13:59 | |
probably were fairly well adapted for whatever thermoregulatory strategy. | 0:13:59 | 0:14:04 | |
I think they were perfectly well adapted to deal | 0:14:04 | 0:14:07 | |
with the problems of maintaining a body temperature. | 0:14:07 | 0:14:10 | |
Advances in technology were allowing scientists to break new ground, | 0:14:17 | 0:14:21 | |
proving that dinosaurs weren't just giant lizards | 0:14:21 | 0:14:24 | |
but a truly unique kind of reptile. | 0:14:24 | 0:14:27 | |
But like a detective looking for clues, | 0:14:27 | 0:14:30 | |
finding a whole dinosaur skeleton was the palaeontologists' dream | 0:14:30 | 0:14:34 | |
and, in 1990, an American fossil-hunter hit the jackpot. | 0:14:34 | 0:14:38 | |
For Pete Larson, and his then girlfriend Susan, | 0:14:46 | 0:14:49 | |
the day had started as an ordinary, everyday fossil hunt. | 0:14:49 | 0:14:54 | |
We were out actually digging on a triceratops skull | 0:14:54 | 0:14:57 | |
that my ten-year-old son Matthew had found. | 0:14:57 | 0:15:00 | |
We were just having a grand old time, it was a very nice, small triceratops skull. | 0:15:00 | 0:15:03 | |
And all of a sudden, Susan walks up with a couple of bone fragments. | 0:15:03 | 0:15:07 | |
And I said, "Is there more?" | 0:15:07 | 0:15:10 | |
And she said, "There's lots more." | 0:15:10 | 0:15:11 | |
Nothing could have prepared them for what they'd found. | 0:15:14 | 0:15:17 | |
I looked up the face of the cliff and saw an expanse about eight feet wide | 0:15:19 | 0:15:24 | |
and perhaps two feet deep with bones jutting out everywhere. | 0:15:24 | 0:15:28 | |
And as I crawled up to the top of this exposure, | 0:15:28 | 0:15:31 | |
I saw three articulated vertebra. | 0:15:31 | 0:15:34 | |
I knew they had to come from a T rex because of the size of the curve of those bones, | 0:15:39 | 0:15:44 | |
they were obviously parts of vertebrae | 0:15:44 | 0:15:47 | |
from a meat-eating dinosaur. | 0:15:47 | 0:15:48 | |
And when I saw those three articulated vertebrae, | 0:15:50 | 0:15:53 | |
I knew this was going to be the most important specimen we'd ever dug up. | 0:15:53 | 0:15:57 | |
I just knew it. | 0:15:57 | 0:15:58 | |
Pete Larson marvelled at the size of the partially-exposed killer dinosaur. | 0:16:01 | 0:16:05 | |
And nicknamed it "Sue" after his girlfriend. | 0:16:08 | 0:16:11 | |
It was like clawing our way to the top of Mount Everest, | 0:16:13 | 0:16:16 | |
and as we were uncovering it, we could see the top, | 0:16:16 | 0:16:19 | |
and as we got her out of the ground, we were there. | 0:16:19 | 0:16:23 | |
We had climbed the Mount Everest of palaeontology. | 0:16:23 | 0:16:25 | |
We got the biggest, baddest of all the T rexs that ever was. | 0:16:34 | 0:16:39 | |
And it got even better. | 0:16:40 | 0:16:42 | |
Sue was extremely well preserved and nearly complete, | 0:16:45 | 0:16:48 | |
exactly what Pete Larson had dreamed of finding. | 0:16:48 | 0:16:52 | |
At long last, here was a chance to study the world's ultimate killing machine | 0:16:52 | 0:16:57 | |
in extraordinary detail | 0:16:57 | 0:16:59 | |
and all from just this one specimen. | 0:16:59 | 0:17:02 | |
Deep within Sue's well-preserved skull, | 0:17:33 | 0:17:36 | |
scientists were about to discover something they'd never seen before. | 0:17:36 | 0:17:41 | |
And cutting edge technology would allow them to see it in exquisite detail. | 0:17:46 | 0:17:51 | |
Basically, when it comes down to it, I was told to describe the thing inside and out | 0:17:53 | 0:17:57 | |
I took that literally. | 0:17:57 | 0:17:58 | |
I knew they wouldn't let me break the skull apart | 0:17:58 | 0:18:00 | |
so CT scanning is the answer. | 0:18:00 | 0:18:03 | |
CT scanning is an advanced x-ray imaging technique. | 0:18:08 | 0:18:12 | |
It allowed Chris Brochu to build up | 0:18:14 | 0:18:16 | |
computer images of slices through the head | 0:18:16 | 0:18:19 | |
which he moulded together to produce | 0:18:19 | 0:18:22 | |
a three-dimensional likeness of a T rex skull. | 0:18:22 | 0:18:25 | |
Then, painstakingly, millimetre by millimetre, he followed the contours | 0:18:31 | 0:18:36 | |
on the inside of the skull to reveal the structure of a T rex brain. | 0:18:36 | 0:18:41 | |
The first time I saw the individual slices themselves, | 0:18:52 | 0:18:55 | |
they didn't seem all that exciting. | 0:18:55 | 0:18:57 | |
It wasn't until I built the first animation, | 0:18:57 | 0:19:00 | |
the first flip through a bunch of slices all going through the skull, | 0:19:00 | 0:19:03 | |
that was when it really struck me | 0:19:03 | 0:19:06 | |
that there were a lot of things here to see. | 0:19:06 | 0:19:08 | |
The CT scans revealed something scientists had never before been able to see in such detail. | 0:19:10 | 0:19:16 | |
Protruding from the delicate network of brain tissue, | 0:19:20 | 0:19:24 | |
was the optic nerve. | 0:19:24 | 0:19:25 | |
This nerve was responsible for relaying information | 0:19:28 | 0:19:32 | |
from the eyes to the visual centres in the brain. | 0:19:32 | 0:19:35 | |
And it was big enough to carry a LOT of information. | 0:19:37 | 0:19:40 | |
The scans seemed to confirm T rex did indeed | 0:19:43 | 0:19:46 | |
have a key attribute of a skilled predator. | 0:19:46 | 0:19:49 | |
It would have been able to seek out its prey at a distance | 0:19:49 | 0:19:54 | |
and destroy it with the accuracy of an assassin. | 0:19:54 | 0:19:57 | |
T rex could see its prey, but that didn't automatically make it | 0:20:04 | 0:20:08 | |
an efficient killer. | 0:20:08 | 0:20:09 | |
To get to grips with its enormous jaws, | 0:20:09 | 0:20:12 | |
scientists devised a risky experiment. | 0:20:12 | 0:20:15 | |
Watcha, watcha. | 0:20:15 | 0:20:16 | |
Gators and crocodiles make a great model | 0:20:19 | 0:20:21 | |
for studying the feeding biomechanics | 0:20:21 | 0:20:23 | |
of extinct theropod dinosaurs. | 0:20:23 | 0:20:24 | |
They have very similar musculature, and the basic leverage of their jaws | 0:20:24 | 0:20:29 | |
and things like that are just a good analogy for tyrannosaur feeding. | 0:20:29 | 0:20:33 | |
OK, grab that pole! | 0:20:36 | 0:20:38 | |
Let's go. | 0:20:38 | 0:20:39 | |
Watch your feet, watch your feet. Remember she can run forward. | 0:20:42 | 0:20:46 | |
One, two, three...go, go, go! | 0:20:46 | 0:20:50 | |
Watch your feet, Ray. | 0:20:50 | 0:20:51 | |
This is a female American crocodile, Stevie. | 0:20:51 | 0:20:55 | |
A youngster at 31 years old, she's only half the size she could become. | 0:20:55 | 0:20:59 | |
She may be small, but her strength is obvious. | 0:20:59 | 0:21:04 | |
Stay in line with her. Back up, back up, back up! | 0:21:04 | 0:21:08 | |
-Back up. Who's got tape? -I have tape. | 0:21:10 | 0:21:13 | |
She's heavy. | 0:21:13 | 0:21:14 | |
Because her jaws are thought to work in a similar way to T rex jaws, | 0:21:14 | 0:21:19 | |
Erickson plans to measure her bite to see what it may reveal | 0:21:19 | 0:21:22 | |
about the power behind a T rex bite. | 0:21:22 | 0:21:24 | |
Yet, as she's small and he's not tested her before, | 0:21:26 | 0:21:28 | |
he has no idea what kind of results he'll get. | 0:21:28 | 0:21:32 | |
All the way with that... | 0:21:32 | 0:21:34 | |
I'm all set. | 0:21:34 | 0:21:36 | |
Erickson needs to get the crocodile to crunch onto | 0:21:36 | 0:21:39 | |
a specially-designed pressure sensor, | 0:21:39 | 0:21:42 | |
which will record the force of the bite. | 0:21:42 | 0:21:45 | |
OK, everybody ready? | 0:21:45 | 0:21:46 | |
The tricky bit is getting the timing right. | 0:21:46 | 0:21:50 | |
The bite needs to be a spontaneous one. | 0:21:50 | 0:21:52 | |
Here we go. Hang on. | 0:21:58 | 0:22:00 | |
819lbs. Good bite. | 0:22:06 | 0:22:10 | |
An 800-lb bite is comparable to what a lion could do or | 0:22:10 | 0:22:13 | |
a spotted hyena, which is the bone crushing champion among mammals. | 0:22:13 | 0:22:17 | |
A very small crocodilian is capable of doing bite forces | 0:22:17 | 0:22:20 | |
equal to what some of these large carnivoran mammals do. | 0:22:20 | 0:22:24 | |
If you matched up an equal-sized crocodile say to a large lion, | 0:22:24 | 0:22:28 | |
the crocodile will bite three times more forcefully. | 0:22:28 | 0:22:31 | |
Watch your legs. | 0:22:31 | 0:22:33 | |
If jaws like these give crocodiles a bite force | 0:22:34 | 0:22:37 | |
well above what their weight implies, | 0:22:37 | 0:22:40 | |
then Erickson believes the same must have been true of T rex jaws. | 0:22:40 | 0:22:43 | |
His work suggested the power of a T rex bite | 0:22:43 | 0:22:48 | |
may have been on a scale beyond anything we have ever seen. | 0:22:48 | 0:22:52 | |
It's not a natural thing | 0:22:52 | 0:22:53 | |
to stick your hand inside the mouth of a crocodile, but... | 0:22:53 | 0:22:57 | |
Probably shouldn't try this at home, kids. | 0:22:57 | 0:22:59 | |
To get an idea of how much more powerful, | 0:22:59 | 0:23:01 | |
Erickson worked on doing more than just scale up the bite. | 0:23:01 | 0:23:06 | |
Snout width is 14.2. | 0:23:06 | 0:23:08 | |
He measured every physical detail of his crocodiles to try to map | 0:23:08 | 0:23:12 | |
the differences in skull shape and body weight | 0:23:12 | 0:23:15 | |
compared to an animal the size and shape of a T rex. | 0:23:15 | 0:23:19 | |
50.2 head length... | 0:23:19 | 0:23:22 | |
Erickson's preliminary maximum estimate of a T rex bite | 0:23:22 | 0:23:26 | |
could be as much as 40,000lbs of force. | 0:23:26 | 0:23:30 | |
That's about 50 times more powerful than our crocodile. | 0:23:32 | 0:23:36 | |
T rex would have had easily the most powerful bite | 0:23:37 | 0:23:40 | |
of any animal that has ever lived. | 0:23:40 | 0:23:43 | |
The combination of new finds and advanced technology | 0:23:58 | 0:24:01 | |
has enabled palaeontologists to interpret fossils | 0:24:01 | 0:24:04 | |
with greater certainty. | 0:24:04 | 0:24:07 | |
We now know more than ever before | 0:24:07 | 0:24:10 | |
about what dinosaurs looked like, | 0:24:10 | 0:24:13 | |
how fast they grew, their skill as predators, | 0:24:13 | 0:24:19 | |
and how they moved. | 0:24:19 | 0:24:20 | |
All building a convincing picture | 0:24:24 | 0:24:28 | |
of how the dinosaurs came to dominate the Earth | 0:24:28 | 0:24:31 | |
for over 160 million years. | 0:24:31 | 0:24:32 | |
160 million years is a pretty long time | 0:24:41 | 0:24:44 | |
and makes dinosaurs some of the most successful animals | 0:24:44 | 0:24:47 | |
ever to have walked the Earth. | 0:24:47 | 0:24:48 | |
After all, modern humans have only been around for a couple of hundred thousand years. | 0:24:48 | 0:24:53 | |
Evidence of dinosaur life fills the geological record | 0:24:53 | 0:24:56 | |
but then suddenly, 65 million years ago, | 0:24:56 | 0:24:59 | |
it all disappeared. | 0:24:59 | 0:25:01 | |
The dinosaurs vanished. | 0:25:01 | 0:25:03 | |
Scientists spent years scrutinising dinosaur bones, looking for answers. | 0:25:07 | 0:25:12 | |
-You got something? -Yeah, this is a vertebrae... | 0:25:12 | 0:25:16 | |
They struggled to come up with ideas to explain the mass extinction. | 0:25:18 | 0:25:22 | |
Perhaps the climate deteriorated, becoming too hot... | 0:25:22 | 0:25:25 | |
..or too cold. | 0:25:31 | 0:25:32 | |
Or suddenly too wet... | 0:25:34 | 0:25:37 | |
..or too dry. | 0:25:39 | 0:25:40 | |
There were problems maybe of reproduction | 0:25:45 | 0:25:48 | |
or maybe their eggs were eaten by the tiny furry mammals. | 0:25:48 | 0:25:51 | |
IT BURPS | 0:25:56 | 0:25:57 | |
Maybe it was God's will or lack of standing room in the ark. | 0:26:00 | 0:26:04 | |
But it was only when they turned their attention to rocks, | 0:26:10 | 0:26:13 | |
rather than bones, that scientists had a breakthrough. | 0:26:13 | 0:26:17 | |
Geologists searching for clues to the extinction discovered | 0:26:18 | 0:26:23 | |
an unusual layer of clay in the geological record that marked | 0:26:23 | 0:26:26 | |
the boundary between the time of the dinosaurs and the time of mammals. | 0:26:26 | 0:26:31 | |
Nobel prize winning physicist Luiz Alvarez and his team | 0:26:31 | 0:26:35 | |
took up the challenge. | 0:26:35 | 0:26:37 | |
You see this clay layer here, about a half-inch thick. | 0:26:38 | 0:26:41 | |
That's when the dinosaurs went out. | 0:26:41 | 0:26:43 | |
We really don't know how long it took, why it's there. | 0:26:43 | 0:26:47 | |
So I said, "Maybe some of the tricks I know as a physicist | 0:26:47 | 0:26:51 | |
"might help unravel that story." | 0:26:51 | 0:26:54 | |
And we talked about it for the next couple of weeks | 0:26:54 | 0:26:58 | |
and finally decided to look for iridium | 0:26:58 | 0:27:01 | |
as a measure of the deposition rate. | 0:27:01 | 0:27:05 | |
A small quantity of the metal iridium | 0:27:08 | 0:27:10 | |
constantly falls to Earth from space, | 0:27:10 | 0:27:13 | |
and the team expected to find only trace amounts. | 0:27:13 | 0:27:16 | |
But their tests showed something astonishing. | 0:27:17 | 0:27:20 | |
There was so much iridium in the clay layer | 0:27:20 | 0:27:23 | |
there could only be one source. | 0:27:23 | 0:27:26 | |
Alvarez's radical idea was that it had been brought to Earth | 0:27:28 | 0:27:32 | |
by a meteorite. | 0:27:32 | 0:27:33 | |
The vast majority of iridium-bearing meteorites started life as asteroids. | 0:27:36 | 0:27:40 | |
Most of them, in an orbit between Mars and Jupiter, | 0:27:40 | 0:27:43 | |
never come anywhere near the Earth. | 0:27:43 | 0:27:45 | |
But the theory goes that a few are occasionally | 0:27:45 | 0:27:48 | |
swung out of line by the enormous gravitational pull of Jupiter. | 0:27:48 | 0:27:52 | |
A very few of these finish up in an orbit which crosses the Earth's. | 0:27:54 | 0:27:58 | |
Most of time they pass harmlessly by, but every now and then, they collide. | 0:27:58 | 0:28:02 | |
Alvarez's theory is that 65 million years ago a huge asteroid, | 0:28:04 | 0:28:08 | |
six miles wide, smashed into the Earth with devastating effects. | 0:28:08 | 0:28:12 | |
It was this collision, he believes, that covered the Earth with iridium | 0:28:19 | 0:28:23 | |
and wiped out the dinosaurs. | 0:28:23 | 0:28:26 | |
It's not all that far-fetched. | 0:28:26 | 0:28:27 | |
Only 25,000 years ago, | 0:28:27 | 0:28:29 | |
a much smaller collision caused Meteor Crater in Arizona. | 0:28:29 | 0:28:33 | |
There are larger impact craters on the Earth's surface. | 0:28:34 | 0:28:37 | |
Many have been eroded away over time, | 0:28:37 | 0:28:40 | |
and are rather difficult to recognise. | 0:28:40 | 0:28:43 | |
Nevertheless, so far, over the whole world, more than 200 | 0:28:43 | 0:28:46 | |
have been identified, | 0:28:46 | 0:28:47 | |
but none of these is both the right age and size for Alvarez's theory. | 0:28:47 | 0:28:52 | |
However, there's an alternative. | 0:28:52 | 0:28:54 | |
The asteroid may have landed in the sea. | 0:28:54 | 0:28:56 | |
Dr Cesare Emiliani. | 0:28:56 | 0:28:58 | |
We have no evidence at all | 0:28:58 | 0:29:00 | |
of a crater of the size that this asteroid this should have made | 0:29:00 | 0:29:04 | |
either on land or on the ocean floor. | 0:29:04 | 0:29:07 | |
This is a map that shows the structure of the ocean floor. | 0:29:07 | 0:29:10 | |
On the other hand, | 0:29:10 | 0:29:11 | |
we have evidence indicating that plant life on the continents, | 0:29:11 | 0:29:15 | |
in a broad area ranging from the Urals to the Rockies, | 0:29:15 | 0:29:20 | |
suffered somewhat, at the end of the Cretaceous. | 0:29:20 | 0:29:24 | |
While plant life west of the Urals, from the Urals to the Rockies, | 0:29:24 | 0:29:29 | |
around the North Atlantic, | 0:29:29 | 0:29:31 | |
suffered very little or nothing at all. | 0:29:31 | 0:29:33 | |
That would seem to indicate that the point of impact of the asteroid | 0:29:33 | 0:29:38 | |
was somewhere between the Urals and the Rockies. | 0:29:38 | 0:29:41 | |
We have no crater on land, we have no crater on the visible ocean floor | 0:29:41 | 0:29:45 | |
but a portion of the ocean floor since then has disappeared under the continent. | 0:29:45 | 0:29:50 | |
Because the oceanic crust moves towards the continents | 0:29:50 | 0:29:54 | |
and then dives under the continents. | 0:29:54 | 0:29:56 | |
There is a substantial chance that the asteroid | 0:29:56 | 0:29:59 | |
might have hit an area of the ocean floor | 0:29:59 | 0:30:02 | |
that has since disappeared. | 0:30:02 | 0:30:04 | |
If one were to make a wild guess as to where the asteroid may have hit, | 0:30:04 | 0:30:08 | |
one would say somewhere in the North Pacific, round here. | 0:30:08 | 0:30:11 | |
Without finding a crater, it was hard to prove that it was | 0:30:15 | 0:30:19 | |
an asteroid that had killed off the dinosaurs. | 0:30:19 | 0:30:21 | |
But, by 1997, scientists realised | 0:30:26 | 0:30:29 | |
they'd been looking in the wrong place. | 0:30:29 | 0:30:32 | |
A number of circular structures had been found in the Caribbean. | 0:30:32 | 0:30:36 | |
The shape of islands, circular structures on the sea floor, | 0:30:36 | 0:30:41 | |
circular geophysical anomalies. | 0:30:41 | 0:30:43 | |
When you're looking for an impact crater, usually the obvious thing, | 0:30:43 | 0:30:47 | |
because most craters are round, is looking for something big and round. | 0:30:47 | 0:30:50 | |
One of Hildebrand's suspects was on the Yucatan peninsula of Mexico. | 0:30:52 | 0:30:57 | |
There the state oil company, Petrolinas Mexicana, had detected | 0:30:57 | 0:31:01 | |
a strange circular anomaly in the Earth's gravity field. | 0:31:01 | 0:31:04 | |
Chixulub, the dead centre of the big round hole, | 0:31:11 | 0:31:14 | |
but at the surface there's no sign of a catastrophe. | 0:31:14 | 0:31:19 | |
The 200km-wide crater is hidden. | 0:31:28 | 0:31:32 | |
It's buried hundreds of metres beneath the Earth's surface, | 0:31:32 | 0:31:35 | |
so Hildebrand had to investigate it in some other way. | 0:31:35 | 0:31:39 | |
We've taken another 1,400 measurements and combined them with the data that | 0:31:39 | 0:31:43 | |
Petroleos Mexicanos already had to make this map of the gravity field. | 0:31:43 | 0:31:48 | |
Here you can see all this concentric circular structure | 0:31:48 | 0:31:52 | |
that represents the crater. | 0:31:52 | 0:31:55 | |
From here to here is about 180km. | 0:31:55 | 0:31:59 | |
Petroleos Mexicanos had known about this big buried structure for decades. | 0:31:59 | 0:32:03 | |
They'd drilled several wells into it for oil exploration, beginning in 1952. | 0:32:03 | 0:32:08 | |
When they did so, they found what they thought was volcanic rock. | 0:32:10 | 0:32:13 | |
But this contains shock quartz and impact glass and so on. | 0:32:13 | 0:32:17 | |
These are the classic signs, | 0:32:17 | 0:32:20 | |
the deposits you'd expect in a big impact crater. | 0:32:20 | 0:32:23 | |
The rock proved to be precisely 65 million years old - | 0:32:23 | 0:32:27 | |
the age of the mass extinction. | 0:32:27 | 0:32:29 | |
Here at last was the first confirmation that Chicxulub was ground zero. | 0:32:29 | 0:32:34 | |
Hildebrand confirmed the theory proposed 17 years earlier | 0:32:36 | 0:32:41 | |
that a devastating asteroid had hit Earth 65 million years ago. | 0:32:41 | 0:32:46 | |
By 2004, scientists believed they had proof that the impact | 0:32:53 | 0:32:57 | |
had caused a massive explosion... | 0:32:57 | 0:33:00 | |
..quickly followed by an enormous shock wave that had destroyed life for hundreds of miles around | 0:33:02 | 0:33:08 | |
And there was more. Investigations of the layer of rock | 0:33:19 | 0:33:23 | |
that marks the time when the dinosaurs disappeared - | 0:33:23 | 0:33:26 | |
known as the KT boundary - | 0:33:26 | 0:33:28 | |
revealed further evidence of what had happened in the aftermath. | 0:33:28 | 0:33:33 | |
These are called spherals. | 0:33:33 | 0:33:35 | |
They're actually made of round rock globules, so we know they're condensed | 0:33:35 | 0:33:39 | |
from a very hot vapour cloud. And some of the mineralogy in there | 0:33:39 | 0:33:46 | |
tells us these globules originated at very high temperatures. | 0:33:46 | 0:33:51 | |
That's exciting. | 0:33:52 | 0:33:53 | |
You know something hot happened and hot is associated with an impact. | 0:33:53 | 0:33:57 | |
The spherals were evidence that the fireball had vaporised | 0:34:00 | 0:34:04 | |
billions of tons of rock. | 0:34:04 | 0:34:07 | |
In outer space, the vapour condensed into tiny droplets which fell back | 0:34:07 | 0:34:11 | |
all over the Earth as white hot spherals. | 0:34:11 | 0:34:15 | |
From America to New Zealand there seemed to be | 0:34:20 | 0:34:24 | |
evidence of massive burning at time of impact. | 0:34:24 | 0:34:28 | |
It looked as if the world's forests had spontaneously ignited, | 0:34:28 | 0:34:31 | |
as the spherals heated the atmosphere by up to 1,000 degrees centigrade. | 0:34:31 | 0:34:36 | |
If we're looking at 600, 1,000 degrees, then this would instantly | 0:34:38 | 0:34:42 | |
have ignited all the plant matter across the world | 0:34:42 | 0:34:45 | |
and it just would have been sent up in flames. | 0:34:45 | 0:34:51 | |
The impact was also thought to have created vicious acid rain. | 0:34:51 | 0:34:57 | |
The fireball had release chemicals, which turned the water deadly. | 0:34:59 | 0:35:03 | |
It was suggested that the acid rain had a pH | 0:35:05 | 0:35:08 | |
so low it was like battery acid. | 0:35:08 | 0:35:10 | |
If you had something that low, | 0:35:10 | 0:35:12 | |
it would literally burn everything on the land | 0:35:12 | 0:35:15 | |
from plants, to dinosaurs to everything else. | 0:35:15 | 0:35:18 | |
Then there was the final clue from the KT boundary - | 0:35:19 | 0:35:23 | |
a high concentration of fern spores. | 0:35:23 | 0:35:26 | |
Ferns flourish whenever all other plants have been killed off by some environmental devastation. | 0:35:31 | 0:35:37 | |
So the predominance of fern spores - known as a fern spike - | 0:35:39 | 0:35:44 | |
suggested something had wiped out every plant on the planet. | 0:35:44 | 0:35:48 | |
Fern spikes were found all over the world, such as in New Zealand. | 0:35:51 | 0:35:55 | |
This, I think, became stronger and stronger evidence | 0:35:55 | 0:35:57 | |
that there was something LIKE global darkness caused by an impact. | 0:35:57 | 0:36:01 | |
So the theory grew up that vast amounts of dust created by the impact | 0:36:04 | 0:36:08 | |
must have blocked out the sun. | 0:36:08 | 0:36:10 | |
This could have plunged the world into freezing darkness for months or years. | 0:36:11 | 0:36:17 | |
Any dinosaurs that escaped burning either froze or starved to death. | 0:36:19 | 0:36:24 | |
The mystery surrounding the death of the dinosaurs | 0:36:34 | 0:36:37 | |
finally appeared to have been solved. | 0:36:37 | 0:36:41 | |
A number of factors may have influenced the extinction, | 0:36:43 | 0:36:46 | |
but research had shown that the impact at Chicxulub WAS the crucial factor. | 0:36:46 | 0:36:51 | |
We should probably be thankful for that mighty asteroid - | 0:36:59 | 0:37:02 | |
if the dinosaurs hadn't been wiped out, | 0:37:02 | 0:37:05 | |
mammals may never have flourished and we might not exist. | 0:37:05 | 0:37:08 | |
So what would have happened if an asteroid hadn't hit the Earth | 0:37:08 | 0:37:11 | |
and the dinosaurs had survived? | 0:37:11 | 0:37:14 | |
It's a thought that's given rise to some novel ideas. | 0:37:14 | 0:37:18 | |
I think that some dinosaurs, like some mammals would have become | 0:37:18 | 0:37:22 | |
increasingly intelligent at a geometric rate, | 0:37:22 | 0:37:25 | |
as did our own ancestors, | 0:37:25 | 0:37:26 | |
and I think, possibly, by this time the dinosaurs themselves | 0:37:26 | 0:37:30 | |
would have approached our own level of brain development. | 0:37:30 | 0:37:34 | |
A sculptor at our museum | 0:37:34 | 0:37:36 | |
and myself have collaborated over the last several months in trying | 0:37:36 | 0:37:39 | |
to estimate what the appearance of one of these highly encephalised | 0:37:39 | 0:37:43 | |
or intelligent dinosaurs might have been, a dinosaur for the 1980s, | 0:37:43 | 0:37:46 | |
and here is an example of what we think it may have looked like. | 0:37:46 | 0:37:50 | |
Their model of a 20th-century dinosaur incorporates | 0:37:56 | 0:37:59 | |
many features of the original reptiles - the binocular vision, | 0:37:59 | 0:38:03 | |
the absence of an external ear, a deep chest cavity with ribs | 0:38:03 | 0:38:08 | |
all the way down the abdomen, | 0:38:08 | 0:38:10 | |
opposable fingers and no external genitalia. | 0:38:10 | 0:38:13 | |
But it looks closer to a human being than a brontosaurus. | 0:38:13 | 0:38:16 | |
In building it, have they perhaps unwittingly favoured our own kind? | 0:38:16 | 0:38:20 | |
I don't think so. | 0:38:20 | 0:38:21 | |
I think just as the birds, bats and flying reptiles all have | 0:38:21 | 0:38:26 | |
a crudely avian form, so too there is a meaning to the human form. | 0:38:26 | 0:38:31 | |
So that we are, in effect, adapted to interact with | 0:38:31 | 0:38:34 | |
an environment as highly encephalised bipeds | 0:38:34 | 0:38:38 | |
or walking animals with a very large brain. | 0:38:38 | 0:38:41 | |
So perhaps were it not for a chance collision with an asteroid, | 0:38:41 | 0:38:45 | |
creatures like this could be ruling the world today | 0:38:45 | 0:38:48 | |
just as they did all those millions of years ago. | 0:38:48 | 0:38:51 | |
Let's imagine that the dinosaurs really did become some sort | 0:38:53 | 0:38:56 | |
of dinosauroid, the great rock doesn't fall out of the sky, | 0:38:56 | 0:38:59 | |
there's a bright light in the sky, the dinosaur says, "What's that? | 0:38:59 | 0:39:02 | |
"No idea". The mass extinction is postponed. In fact, cancelled. | 0:39:02 | 0:39:07 | |
So what's happening then? | 0:39:07 | 0:39:08 | |
We've got the Apes rapidly evolving and they're beginning to | 0:39:08 | 0:39:11 | |
look over their shoulders because just conceivably there are also | 0:39:11 | 0:39:14 | |
these dinosauroids doing rather similar things. | 0:39:14 | 0:39:18 | |
What would have happened? | 0:39:18 | 0:39:20 | |
Would it have been an evolutionary race? Maybe there would have been a winner? | 0:39:20 | 0:39:24 | |
Or maybe, unbelievably, madly, there could have been a co-operation. | 0:39:24 | 0:39:29 | |
The Utopian notion of dinosaurs and humans sharing the planet may appeal, | 0:39:31 | 0:39:36 | |
even be plausible to some, | 0:39:36 | 0:39:38 | |
but most palaeontologists see the dinosauroid as an insult to dinosaurs. | 0:39:38 | 0:39:43 | |
There's probably some good ideas there. | 0:39:43 | 0:39:45 | |
The brain was getting bigger, and they probably | 0:39:45 | 0:39:48 | |
would have continued to outcompete other animals. | 0:39:48 | 0:39:51 | |
But for them to become fully erect like humans is a little bit fanciful. | 0:39:53 | 0:39:58 | |
Dinosaurs would have continued to develop, to specialise. | 0:40:00 | 0:40:03 | |
They would have adapted, but they would have adapted | 0:40:03 | 0:40:07 | |
and specialised as dinosaurs, they wouldn't have become primate-like. | 0:40:07 | 0:40:11 | |
The idea that a dinosauroid could exist as a scientific question... | 0:40:11 | 0:40:16 | |
is bogus. It's about as bogus as it gets. | 0:40:16 | 0:40:19 | |
It is fairly arrogant to think the endpoint of evolution | 0:40:19 | 0:40:25 | |
should emulate human beings. | 0:40:25 | 0:40:28 | |
If the asteroid had never hit, | 0:40:32 | 0:40:34 | |
life on Earth could have been very different. | 0:40:34 | 0:40:38 | |
But that's all just crazy speculation. | 0:40:52 | 0:40:55 | |
Everyone now knows that dinosaurs were wiped out 65 million years ago | 0:40:55 | 0:40:59 | |
and none of them survived that catastrophic asteroid impact. | 0:40:59 | 0:41:03 | |
Or did they? | 0:41:03 | 0:41:04 | |
The idea that dinosaurs may have evolved into something else | 0:41:04 | 0:41:07 | |
was one that had been doing the rounds for many years. | 0:41:07 | 0:41:10 | |
But it began to gather momentum when some palaeontologists | 0:41:10 | 0:41:13 | |
began to increasingly suspect that dinosaurs might still be alive. | 0:41:13 | 0:41:18 | |
The Natural History Museum, London. Within these hallowed halls | 0:41:34 | 0:41:40 | |
lies the fossil that first hinted at the origin of birds. | 0:41:40 | 0:41:43 | |
Discovered in Germany 100 ago, | 0:41:43 | 0:41:47 | |
superstitious quarry workers thought it was a fallen angel. | 0:41:47 | 0:41:50 | |
Archaeopteryx turned out to be something almost as remarkable. | 0:41:58 | 0:42:02 | |
The size of a pigeon, it possessed teeth, a long, bony tail, | 0:42:02 | 0:42:06 | |
and claws on its arms. All features of reptiles. | 0:42:06 | 0:42:11 | |
At the same time, it was very much like a bird. | 0:42:11 | 0:42:14 | |
It actually has impressions of the wing feathers, both wings | 0:42:16 | 0:42:20 | |
and long tail feathers, but the tail has a long set of bones | 0:42:20 | 0:42:25 | |
running down it as well, which modern birds don't have at all. | 0:42:25 | 0:42:29 | |
So Archaeopteryx really does seem to be a primitive bird. | 0:42:29 | 0:42:33 | |
These fossils, I find it exciting to look at them | 0:42:34 | 0:42:37 | |
because they have so much scientific information in them, | 0:42:37 | 0:42:41 | |
but they're very beautiful objects to look at in their own right. | 0:42:41 | 0:42:45 | |
They really are an exceptional snapshot record of evolution. | 0:42:45 | 0:42:49 | |
That fossil was to be the key to something that John Ostrom | 0:42:55 | 0:42:58 | |
had been thinking about for decades. | 0:42:58 | 0:43:01 | |
When he'd first described Deinonychus in the 1960s, | 0:43:02 | 0:43:05 | |
he'd noticed that its skeleton was strangely similar to that of a bird. | 0:43:05 | 0:43:10 | |
Archaeopteryx helped him refine his ideas. | 0:43:12 | 0:43:16 | |
Neat animal, isn't it? | 0:43:16 | 0:43:18 | |
I think so. | 0:43:20 | 0:43:22 | |
And what made me even more excited | 0:43:22 | 0:43:25 | |
was when I saw structures in that animal | 0:43:25 | 0:43:28 | |
that I subsequently recognised | 0:43:28 | 0:43:30 | |
in Archaeopteryx. | 0:43:30 | 0:43:33 | |
-This is the Solnhofen Archaeopteryx. -The Solnhofen specimen, yeah. | 0:43:33 | 0:43:38 | |
John Ostrom's crucial realisation was that | 0:43:40 | 0:43:43 | |
his beloved Deinonychus shared many anatomical features with Archaeopteryx. | 0:43:43 | 0:43:49 | |
He compared in detail the skeletons of predatory dinosaurs, | 0:43:49 | 0:43:53 | |
Archaeopteryx and modern birds. | 0:43:53 | 0:43:55 | |
He found a whole set of similarities - most notably in the skull, | 0:43:55 | 0:44:00 | |
the hind limbs and the forearms. | 0:44:00 | 0:44:02 | |
For a start, they all have the same number of fingers. | 0:44:02 | 0:44:07 | |
This is the skeleton of a modern pigeon. | 0:44:07 | 0:44:10 | |
Three fingers in the hand of a modern bird, | 0:44:10 | 0:44:13 | |
three fingers preserved in the hand of Deinonychus, and that particular | 0:44:13 | 0:44:18 | |
kind of hand morphology is also supplemented by | 0:44:18 | 0:44:23 | |
the strange wrist bone that allows for the flexibility | 0:44:23 | 0:44:28 | |
that produces the flapping strokes. | 0:44:28 | 0:44:30 | |
The similarities between birds | 0:44:30 | 0:44:34 | |
and predaceous dinosaurs is amazing to me. | 0:44:34 | 0:44:39 | |
But, as with all groundbreaking new theories, | 0:44:41 | 0:44:44 | |
Ostrom's idea had its detractors. | 0:44:44 | 0:44:47 | |
The dinosaur-bird theory has tremendous popular appeal, | 0:44:49 | 0:44:53 | |
one can vicariously study dinosaurs at the back yard bird feeder, | 0:44:53 | 0:44:58 | |
and one can buy a piece of dinosaur leg at the local Kentucky Fried Chicken. | 0:44:58 | 0:45:04 | |
So it has tremendous appeal to the public. | 0:45:04 | 0:45:08 | |
Unfortunately, it seems to be wrong. | 0:45:08 | 0:45:10 | |
Alan Feduccia argued that birds evolved long before dinosaurs came along. | 0:45:12 | 0:45:17 | |
They descended from much more primitive reptiles, | 0:45:17 | 0:45:20 | |
and any similarity between birds and predatory dinosaurs was superficial. | 0:45:20 | 0:45:24 | |
They resembled each other because they both walked on their hind legs, | 0:45:24 | 0:45:29 | |
not because they were closely related. | 0:45:29 | 0:45:32 | |
Such vocal sceptics were going to need better proof | 0:45:36 | 0:45:39 | |
if they were to be convinced of the dinosaur-to-bird theory. | 0:45:39 | 0:45:43 | |
And in 1999 in Tucson, Arizona, fossil collectors thought | 0:45:50 | 0:45:54 | |
they might have come across a specimen that fitted the bill. | 0:45:54 | 0:45:58 | |
I carried it out to the light | 0:46:04 | 0:46:07 | |
of the sunlight so that I could see it cross lit. | 0:46:07 | 0:46:11 | |
And there were a number of beautiful teeth in this skull. | 0:46:14 | 0:46:18 | |
And that was very exciting. | 0:46:18 | 0:46:20 | |
And then we studied also the tail that was a dinosaur... | 0:46:20 | 0:46:25 | |
a very dinosaur-like tail. | 0:46:25 | 0:46:27 | |
I got this incredible high feeling, | 0:46:27 | 0:46:30 | |
the feeling of discovery - that wonderful time | 0:46:30 | 0:46:33 | |
when everything clicks into position. | 0:46:33 | 0:46:36 | |
The two fossil dealers thought they could be looking at | 0:46:38 | 0:46:41 | |
one of the most important fossils ever found. | 0:46:41 | 0:46:44 | |
A specimen that would prove beyond doubt | 0:46:44 | 0:46:46 | |
one of the most controversial theories in all of evolution. | 0:46:46 | 0:46:51 | |
This fossil, this clearly cross between a bird | 0:46:51 | 0:46:55 | |
and a dinosaur was what everybody had been looking for. | 0:46:55 | 0:47:00 | |
And here it was, right there, right in front of my eyes, | 0:47:00 | 0:47:02 | |
and I was one of the first people to see it. | 0:47:02 | 0:47:04 | |
I looked it over very carefully. | 0:47:07 | 0:47:08 | |
Literally under a magnifying glass. | 0:47:08 | 0:47:10 | |
And I was looking for any tell-tale features, particularly on the tail. | 0:47:10 | 0:47:14 | |
I wanted to look at that tail very carefully | 0:47:14 | 0:47:16 | |
because it was very clearly a dinosaur tail. | 0:47:16 | 0:47:20 | |
The world of palaeontology was gripped | 0:47:22 | 0:47:25 | |
and a team of experts was assembled to investigate. | 0:47:25 | 0:47:28 | |
After several months, they confirmed that it was the missing link. | 0:47:35 | 0:47:39 | |
It had a bird-like front and legs, and a dinosaur-like tail. | 0:47:39 | 0:47:43 | |
They called it Archaeoraptor, | 0:47:47 | 0:47:49 | |
ancient hunter, | 0:47:49 | 0:47:50 | |
and proudly presented it to the world. | 0:47:50 | 0:47:53 | |
Scientists could now say that dinosaurs evolved into birds. | 0:47:56 | 0:48:00 | |
One of the most important theories in evolution was finally proved. | 0:48:00 | 0:48:04 | |
But not everyone was convinced. | 0:48:10 | 0:48:12 | |
At the university of Texas, Tim Rowe had used a CAT scan | 0:48:20 | 0:48:24 | |
to study the fossil. | 0:48:24 | 0:48:26 | |
The results threw up some serious questions about how it fitted together. | 0:48:26 | 0:48:31 | |
I'm going to show you two slices. | 0:48:31 | 0:48:33 | |
The first is this slice here through the skull | 0:48:33 | 0:48:35 | |
and these other elements here, | 0:48:35 | 0:48:38 | |
and the second slice will be back through the ankle and tail, | 0:48:38 | 0:48:41 | |
this critical region here through one of the legs. | 0:48:41 | 0:48:44 | |
When we go to these slices, here's what we see. | 0:48:46 | 0:48:49 | |
Here's the skull. | 0:48:49 | 0:48:51 | |
We can see the skull is part of this upper layer of shale. | 0:48:51 | 0:48:55 | |
And you can see the fracture pattern here, | 0:48:56 | 0:48:59 | |
here's very tight fractures that fit together. | 0:48:59 | 0:49:01 | |
Here, a pair of fractures, one occurring against the next. | 0:49:01 | 0:49:05 | |
A straight fracture. | 0:49:05 | 0:49:06 | |
The pieces on either side are the same thickness. Same density. | 0:49:06 | 0:49:10 | |
But when we get to the edge of the block, | 0:49:10 | 0:49:12 | |
this piece is a little bit thicker | 0:49:12 | 0:49:14 | |
and denser than the piece it's glued against. | 0:49:14 | 0:49:18 | |
As we move to the tail, to the critical area, | 0:49:19 | 0:49:22 | |
we can see that it's completely surrounded by grout, | 0:49:22 | 0:49:25 | |
and that there are no natural ties between the tail piece | 0:49:25 | 0:49:29 | |
and this piece to the right or left. | 0:49:29 | 0:49:32 | |
In fact, it's just swimming in this ocean of grout here. | 0:49:32 | 0:49:35 | |
And as we map through the entire specimen, we found no verifiable fits | 0:49:35 | 0:49:40 | |
between the tail and any of the other parts anywhere else in the specimen. | 0:49:40 | 0:49:44 | |
The scan clearly showed what the naked eye couldn't see. | 0:49:49 | 0:49:53 | |
There was no natural skeletal link between the all-important tail | 0:49:53 | 0:49:57 | |
and the rest of the fossil. | 0:49:57 | 0:49:59 | |
It had simply been glued on with grout. | 0:50:00 | 0:50:04 | |
The vital evidence that seemed to prove the link between birds | 0:50:10 | 0:50:13 | |
and dinosaurs was a fake. | 0:50:13 | 0:50:15 | |
The dinosaur fake was a dreadful blow for supporters of the bird theory. | 0:50:21 | 0:50:26 | |
But scientists who were committed to the idea refused to give up. | 0:50:26 | 0:50:29 | |
They were determined to keep looking for proof. | 0:50:29 | 0:50:33 | |
Although the fossil had been a fake, | 0:50:35 | 0:50:37 | |
its front half was a new kind of primitive bird. | 0:50:37 | 0:50:41 | |
Fossil hunters flocked to the region where it had been found. | 0:50:43 | 0:50:47 | |
And they struck gold. | 0:50:47 | 0:50:49 | |
Extraordinary, well preserved fossils revealed dinosaurs | 0:50:58 | 0:51:02 | |
and birds not only shared features like downy feathers, | 0:51:02 | 0:51:05 | |
but also hollow bones and similar pelvises and hind limbs. | 0:51:05 | 0:51:10 | |
On a remote farm in Colorado, | 0:51:27 | 0:51:30 | |
palaeontologist Brent Breithaupt presented even more proof | 0:51:30 | 0:51:33 | |
of the close relationship between the ancient fossils and birds. | 0:51:33 | 0:51:37 | |
Very good. That should make an excellent track. | 0:51:40 | 0:51:43 | |
Here we have two tracks that we recently made. | 0:51:43 | 0:51:48 | |
This one here is from the Red Gulch Dinosaur Tracksite. | 0:51:48 | 0:51:51 | |
This one here preserves the three-toe impressions, | 0:51:51 | 0:51:56 | |
tridactyl impressions, of the foot of the dinosaurs. | 0:51:56 | 0:52:00 | |
The small to medium sized theropod dinosaurs that lived up there. | 0:52:00 | 0:52:03 | |
Now, over here, we have one that we just got from this site. | 0:52:03 | 0:52:10 | |
Again, a nice tridactyl footprint. | 0:52:10 | 0:52:14 | |
Again, very well preserved. | 0:52:14 | 0:52:16 | |
If we compare both casts, | 0:52:16 | 0:52:19 | |
we can see these particular tracks look very, very much the same. | 0:52:19 | 0:52:24 | |
But these footprints are not of a theropod that died 65 million years ago... | 0:52:25 | 0:52:30 | |
These are only a few hours old. | 0:52:32 | 0:52:34 | |
There's dinosaurs in them there hills. | 0:52:37 | 0:52:39 | |
In fact, dinosaurs are everywhere. | 0:52:42 | 0:52:45 | |
For the first time on network television, | 0:52:54 | 0:52:57 | |
palaeontologist Julia Clarke is about to perform an autopsy on a dinosaur. | 0:52:57 | 0:53:03 | |
Only you are more likely to know it... | 0:53:05 | 0:53:09 | |
as a roast turkey. | 0:53:09 | 0:53:11 | |
Because you see, birds ARE dinosaurs. | 0:53:13 | 0:53:17 | |
So today we're going to dissect the evidence that birds | 0:53:17 | 0:53:21 | |
are living dinosaurs from this turkey. | 0:53:21 | 0:53:24 | |
What we're pulling off here is the major flight muscle, | 0:53:27 | 0:53:30 | |
supracoracoideus that is in velociraptor and oviraptor. | 0:53:30 | 0:53:35 | |
One of the features you see is that the second finger is the longest. | 0:53:37 | 0:53:41 | |
This is a feature we see going back as far as early dinosaurs, | 0:53:41 | 0:53:46 | |
even Triassic forms. | 0:53:46 | 0:53:48 | |
We're all familiar with wishbones, from any kind of turkey meal. | 0:53:54 | 0:53:59 | |
Wishbones actually are one of the most intuitive pieces of evidence | 0:53:59 | 0:54:04 | |
that birds are living dinosaurs, because we have wishbones now | 0:54:04 | 0:54:08 | |
from a variety of theropod dinosaurs, including relatives of tyrannosaurus | 0:54:08 | 0:54:13 | |
and velociraptor, and even earlier dinosaurs such as coelophysis. | 0:54:13 | 0:54:18 | |
Yes, just as we share 98% of our DNA with chimps, | 0:54:22 | 0:54:27 | |
turkeys - in fact all modern birds - | 0:54:27 | 0:54:31 | |
are direct descendants of theropod dinosaurs. | 0:54:31 | 0:54:34 | |
And the freshly-made dinosaur tracks in the hills of Colorado? | 0:54:44 | 0:54:49 | |
Emus. | 0:54:51 | 0:54:52 | |
Inwardly, outwardly, even in the way they move, | 0:54:55 | 0:54:58 | |
the similarities between theropod dinosaurs and birds are numerous. | 0:54:58 | 0:55:03 | |
But, being warm-blooded, their ultimate success | 0:55:03 | 0:55:07 | |
was in an evolutionary solution to the need to keep warm. | 0:55:07 | 0:55:11 | |
Large dinosaurs really don't have a problem with body heat. | 0:55:11 | 0:55:15 | |
If they have a problem, it's getting rid of excess body heat. | 0:55:15 | 0:55:19 | |
But small dinosaurs have this problem. | 0:55:19 | 0:55:21 | |
They're losing their heat all the time. | 0:55:21 | 0:55:23 | |
So it would be a good thing if a small dinosaur was | 0:55:23 | 0:55:26 | |
warm-blooded, for it to have some kind of insulation on its body. | 0:55:26 | 0:55:30 | |
It started with the development of thin, downy filaments. | 0:55:30 | 0:55:35 | |
In time, those filaments strengthened and thickened. | 0:55:35 | 0:55:39 | |
As non-flying birds, emus are one of the best examples | 0:55:39 | 0:55:44 | |
of feathers as they were originally designed. As an insulating layer. | 0:55:44 | 0:55:48 | |
Once you have those long feathers, then of course it does give you | 0:55:49 | 0:55:53 | |
an aerodynamic advantage as well. | 0:55:53 | 0:55:55 | |
And if you have that advantage, then selection starts working on that advantage. | 0:55:55 | 0:56:00 | |
And it may well be that that was forcing these feathers to become longer | 0:56:00 | 0:56:04 | |
and longer until finally that animal not only jumped across the ditch, | 0:56:04 | 0:56:08 | |
it actually flapped its arms and flew across the ditch. | 0:56:08 | 0:56:11 | |
And so it seems that flight, far from being | 0:56:11 | 0:56:13 | |
the reason for the evolution of feathers, may have been a by-product. | 0:56:13 | 0:56:19 | |
But with it, some dinosaurs were already adapting in ways | 0:56:19 | 0:56:22 | |
that would equip them for life after the meteorite impact. | 0:56:22 | 0:56:26 | |
The fact of the matter is that the age of the dinosaurs never actually ended. | 0:56:28 | 0:56:32 | |
Dinosaurs DID survive the cataclysmic event of 65 million years ago. | 0:56:32 | 0:56:37 | |
So when we talk about dinosaurs living with us today, | 0:56:40 | 0:56:44 | |
and the fanciful notion of what it would be like, it's not so much fantasy. | 0:56:44 | 0:56:49 | |
They're right there. | 0:56:49 | 0:56:50 | |
Dinosaurs have not only survived, there are far more species of them | 0:56:50 | 0:56:54 | |
-on the Earth today than there are mammals. -They're not the biggest animals any more, | 0:56:54 | 0:56:59 | |
but still there's over 10,000 living species of descendents of dinosaurs. | 0:56:59 | 0:57:03 | |
They didn't actually go extinct at the end of the Cretaceous period | 0:57:03 | 0:57:07 | |
like everybody thinks. They're outside flying around. | 0:57:07 | 0:57:10 | |
You can't go into a forest without hearing dinosaurs. | 0:57:10 | 0:57:14 | |
In that sense, maybe they won out, | 0:57:14 | 0:57:18 | |
and we just think we're on top. | 0:57:18 | 0:57:21 | |
Over the last half-century, | 0:57:26 | 0:57:29 | |
scientists have hunted all over the world for new clues | 0:57:29 | 0:57:33 | |
to help them piece together the fragments which reveal the life of the dinosaurs. | 0:57:33 | 0:57:38 | |
They've come up with ingenious new ways of working out | 0:57:38 | 0:57:41 | |
how the dinosaurs lived and behaved, | 0:57:41 | 0:57:45 | |
made extraordinary discoveries, | 0:57:45 | 0:57:49 | |
and battled to answer some of the oldest, most vital questions of all. | 0:57:49 | 0:57:55 | |
But there are still things we don't know, | 0:57:59 | 0:58:02 | |
mysteries to be solved, and one of the exciting things | 0:58:02 | 0:58:05 | |
about palaeontology is that, in an instant, | 0:58:05 | 0:58:07 | |
perhaps with just the tiniest of discoveries, | 0:58:07 | 0:58:10 | |
everything we think we know about dinosaurs today | 0:58:10 | 0:58:13 | |
could all change again. | 0:58:13 | 0:58:14 | |
There are always new discoveries out there... | 0:58:14 | 0:58:17 | |
waiting to be found. | 0:58:17 | 0:58:18 | |
Subtitles by Red Bee Media Ltd | 0:58:34 | 0:58:38 | |
Email [email protected] | 0:58:38 | 0:58:41 |