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Dinosaurs.


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Masters of the planet
for 160 million years.


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The biggest, baddest animals
ever to walk the Earth.


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They had claws a foot long.


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And enormous, bone-crushing jaws


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with teeth the size
of carving knives.


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Weighing up to 80 tons,
the ground would literally shake
when they moved.


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But how do we know
so much about them?


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For over 40 years,
Horizon and the BBC have followed


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the world's palaeontologists
on their quest to find out


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what these elusive creatures
were really like.


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As a palaeontologist,
I love digging up the possibility


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of monsters of my childhood,


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looking for strange beasts
that once roamed where I live now.


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Over time, with only bones
and tiny fragments of information


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to go on, scientists have managed
to piece together


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the complex jigsaw puzzle
that is the life of the dinosaurs.


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There have been astonishing
new finds,


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controversial theories...


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And extraordinary revelations
about these giant reptiles.


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Quick, agile, fast-moving.


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15,000lbs of gut-crunching terror.


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These tantalising clues
and breakthrough new technology
have enabled scientists


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to reach for the answers
to the biggest questions of all.


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Do we really know
what happened to the dinosaurs?


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And is there a chance that some
might still be alive today?


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When Horizon first began reporting
on dinosaurs over 40 years ago,


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palaeontology was a science
based on a lot of speculation


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and not that much evidence.


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Scientists really had just bits
and pieces to go on.


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So it's hardly surprising that the
dinosaurs we came to know and love


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were really just a mixture of fact
and fantasy.


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The largest flesh eater
the world has ever seen.


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I'm not afraid!


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All children now learn
at an early age,


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but are reluctant to believe
that tyrannosaurus


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and all the other dinosaurs followed
a well-trod trail to oblivion.


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I see a little hole up in his nose.


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They've heard other stories
about dinosaurs too,


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many of which are myths,


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replacing the fairy stories
of earlier generations.


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For our limited knowledge
of these pre-historic monsters


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provides numerous questions,
but very few answers.


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CHILDREN LAUGH


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Look at that. Nine feet tall.
What a monster.


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For years, scientists had grappled
with fundamental questions.


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They didn't know what dinosaurs ate,
how they bred.


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Sometimes they weren't even sure
how the skeletons fitted together.


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They also couldn't work out


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whether one of the major
groups of dinosaurs,


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the sauropods,
lived on land or in water.


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But one of the first major finds
covered by Horizon


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revealed evidence of sauropod
behaviour frozen in time.


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Footprints.


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In the bed of the Paluxy
river in Texas are tracks made


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by dinosaurs 70 million years ago,


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when the hard limestone rock was mud.


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This is evidence that convinces
the most doubting tourist.


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Some are tracks of the meat-eating
dinosaurs,


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Others of the heavy, long-necked,
long-tailed dinosaurs.


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It is these which pose a problem.


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Were the creatures who made
these tracks swamp dwellers,


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or did they move around on land?


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30 years ago, the river was dammed
and the tracks photographed


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and carefully plotted.
The shallowness of the footprints


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and the absence of tail marks
suggested a herd of the animals


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living in water sufficiently deep
to keep their tails out of the mud.


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It's difficult to believe
that such huge creatures


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weighing up to 80 tons could
support themselves out of water.


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But here is evidence for just that,
a tail mark.


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If these creatures could support
themselves out of water


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on one occasion, couldn't
they be ordinary land dwellers


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who occasionally ventured
to the swamps?


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At the time, a single tail mark
was not enough to convince


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the palaeontologists that sauropods
were anything but aquatic.


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But as more skeletons
were discovered,


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their similarities to animals
living on land became clearer.


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So then we have long straight limbs
and a long neck,


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adaptations not for a hippo-like
existence,


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but for living on land,
feeding high on trees.


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Scientists looked again
at the fossil footprints...


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And turned to living animals to try
and determine how fast


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the sauropods could move.


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Dinosaur bones are only one source
of information.


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Present day animals are another.


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Neil Alexander is Professor
of Zoology at Leeds University.


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His main research interest
is analysing how animals move.


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Recently he's found a way of applying
his work


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to answering a seemingly
impossible question.


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How fast did dinosaurs walk?


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On the beach at Southport,
some vital evidence was laid out.


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These are replicas of some of
the biggest footprints ever found.


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They were found in Texas,
and they're not new footprints.


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They're footprints made something
like 100 million years ago,


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preserved as fossils.


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Now, these big fellows,
these are the hind feet.


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It was a four legged animal,


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and these hind feet


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are about three feet long.
Stride length here of eight feet


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from right hind foot down
to right hind foot down again.


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The dinosaur footprints are only
part of the information needed.


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Now something called a Froude number
has to be worked out.


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It's a mathematical formula relating
the size of an animal's legs


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to the way its stride increases
as it moves faster.


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Now we're going along
at about five miles an hour,


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and the horse is walking.


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Each foot is moving
in its own time.


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There are no two feet
going together.


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We're going to speed up a bit,
and then you'll see the gait change.


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If we go up now to about ten miles
an hour, there we are...


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The diagonally opposite feet
are moving together.


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Now if we speed up again
and go further, there we are...


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Going through a canter
into a full gallop.


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In the gallop, we've got the
two forefeet moving about together,


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the two hind feet moving, again,
about together.


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And now we must be going
at something like 20 miles an hour.


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Professor Alexander has studied
dozens of animals,


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from tiny gerbils to huge elephants,
and worked out their Froude numbers.


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From these, he's able to estimate


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what the Froude number
for any animal of any size will be.


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And so we find out what the Froude
number is for the dinosaur,


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and how fast the dinosaur was going.


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And it's awful slow.


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Two miles an hour.


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Now, two miles an hour,
that's a slow walk for a man.


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For something with legs
three times as long as a man,


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it's a very slow walk indeed.


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Professor Alexander's work
had reinforced the widely held view


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that dinosaurs were slow,
lumbering reptiles.


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But the discovery of
a new kind of dinosaur


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would change our thinking.


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We have right over here
one that I discovered myself,


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which I think is one of
the most interesting dinosaurs


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that's ever been found.
In fact, I also think


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it's one of the most important
dinosaurs ever found.


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Let me show you
some interesting things


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about this fellow. First of all,
it's a carnivorous dinosaur.


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But not a big one
like tyrannosaurus,


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it's just a little fella,


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probably about four or five feet
high,


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maybe about eight or nine feet
in length.


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Weighed maybe about 175 pounds,
about your weight or mine.


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One of the curious things about him
is the construction of his foot.


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And the peculiar thing about this
is the very large, sickle-like claw


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on the one toe.


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And remember that in addition
to this long bony claw,


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there was a horny sheath
that fit over that


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so that the total claw
was probably half again as long.


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Obviously not designed for walking,


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and quite certainly
an offensive weapon.


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This strange structure


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which we had never seen before
in any of the carnivorous dinosaurs


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is the reason I coined
the name for this that I did.
Terrible claw. Deinonychus.


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But he was a fella


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I wouldn't want to meet on a dark
street at night, I'll tell ya.


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John Ostrum realised Deinonychus
was a ground-breaking dinosaur,


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one that overturned long-held ideas
about how they moved.


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So the picture that we get
from Deinonychus


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seems to be completely different


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from the old picture that we had
of dinosaurs as sort of sluggish,


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sun-basking animals
like modern lizards


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and turtles. Deinonychus
seems to be a very quick, agile,


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fast-moving, two-legged predator.


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Good balance control means
a high neurological development.


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This discovery is what sort of
pushed me over the brink


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into looking at dinosaurs
in a whole new light.


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Other dinosaurs too were suddenly
seen as fast-moving, agile creatures.


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And Ostrum's new ideas about them
developed like this.


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In the animal world, there's
a major division. In one group,


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there are mammals which are active,
hot-blooded creatures.


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In the other are reptiles,
which are generally less active


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and cold-blooded.


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Where do dinosaurs fit?


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Since like mammals,
they were very active,


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Ostrum reasoned perhaps
they were hot-blooded too.


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This idea was revolutionary.


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Was it really possible
that dinosaurs,


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ancient reptiles,
could be warm-blooded?


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It would be another 30 years
before deep bone analysis


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revealed that he might be right.


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For years, palaeontologists
have been looking


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at the outsides of dinosaurs.


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+On the outsides, we can understand
how dinosaurs evolved


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and their anatomy changed over time,


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but deep inside the bones,
we can trace dinosaur life.


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By analysing thin cross-sections
of fossilised dinosaur bone,


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Kristi Curry Rogers
is helping to rewrite


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what we know about dinosaurs
from the inside out.


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I think let's go with this one.


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And the smaller one.


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Those two look good. OK.


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One of the things we see


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when we crack open dinosaur bones is
a story of a very fast growth rate


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throughout life history.
We see that dinosaurs


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were growing very, very quickly on
a par with modern mammals and birds,


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not like reptiles at all.


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This is a great example
from a young Apatosaurus,


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a young, large sauropod dinosaur.


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All of these white spaces we see
are places where blood vessels


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used to flow through this bone
when the animal was still alive.


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This is completely different
than the bone


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we might see of a reptile,
like a crocodile, or a turtle.


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Instead this is lot more similar
to those bones of mammals and birds.


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What she's discovered from deep
within the dinosaur bones


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has reinforced the idea
that at least some of them
were warm-blooded.


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Dinosaurs, just like other
modern animals,


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probably were fairly well adapted
for whatever
thermoregulatory strategy.


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I think they were
perfectly well adapted to deal


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with the problems
of maintaining a body temperature.


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Advances in technology
were allowing scientists
to break new ground,


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proving that dinosaurs
weren't just giant lizards


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but a truly unique kind of reptile.


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But like a detective
looking for clues,


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finding a whole dinosaur skeleton
was the palaeontologists' dream


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and, in 1990, an American
fossil-hunter hit the jackpot.


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For Pete Larson, and his then
girlfriend Susan,


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the day had started as an ordinary,
everyday fossil hunt.


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We were out actually digging
on a triceratops skull


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that my ten-year-old son Matthew
had found.


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We were just having a grand old time,
it was a very nice, small
triceratops skull.


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And all of a sudden, Susan walks up
with a couple of bone fragments.


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And I said, "Is there more?"


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And she said, "There's lots more."


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Nothing could have prepared them
for what they'd found.


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I looked up the face of the cliff
and saw an expanse
about eight feet wide


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and perhaps two feet deep
with bones jutting out everywhere.


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And as I crawled up
to the top of this exposure,


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I saw three articulated vertebra.


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I knew they had to come from a T rex
because of the size of the curve
of those bones,


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they were obviously
parts of vertebrae


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from a meat-eating dinosaur.


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And when I saw those three
articulated vertebrae,


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I knew this was going to be the most
important specimen we'd ever dug up.


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I just knew it.


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Pete Larson marvelled at the size
of the partially-exposed
killer dinosaur.


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And nicknamed it "Sue"
after his girlfriend.


237
00:16:13,360 --> 00:16:16,600
It was like clawing our way
to the top of Mount Everest,


238
00:16:16,600 --> 00:16:19,360
and as we were uncovering it,
we could see the top,


239
00:16:19,360 --> 00:16:23,240
and as we got her out of the
ground, we were there.


240
00:16:23,240 --> 00:16:25,760
We had climbed
the Mount Everest of palaeontology.


241
00:16:34,600 --> 00:16:39,000
We got the biggest, baddest of all
the T rexs that ever was.


242
00:16:40,880 --> 00:16:42,840
And it got even better.


243
00:16:45,000 --> 00:16:48,400
Sue was extremely well preserved
and nearly complete,


244
00:16:48,400 --> 00:16:52,120
exactly what Pete Larson
had dreamed of finding.


245
00:16:52,120 --> 00:16:57,680
At long last, here was a chance
to study the world's
ultimate killing machine


246
00:16:57,680 --> 00:16:59,640
in extraordinary detail


247
00:16:59,640 --> 00:17:02,480
and all from just this one specimen.


248
00:17:33,600 --> 00:17:36,920
Deep within Sue's
well-preserved skull,


249
00:17:36,920 --> 00:17:41,480
scientists were about to discover
something they'd never seen before.


250
00:17:46,480 --> 00:17:51,760
And cutting edge technology
would allow them to see it
in exquisite detail.


251
00:17:53,080 --> 00:17:57,000
Basically, when it comes down to it,
I was told to describe
the thing inside and out


252
00:17:57,000 --> 00:17:58,360
I took that literally.


253
00:17:58,360 --> 00:18:00,760
I knew they wouldn't let me break
the skull apart


254
00:18:00,760 --> 00:18:03,240
so CT scanning is the answer.


255
00:18:08,440 --> 00:18:12,080
CT scanning is an advanced
x-ray imaging technique.


256
00:18:14,400 --> 00:18:16,720
It allowed Chris Brochu to build up


257
00:18:16,720 --> 00:18:19,600
computer images of
slices through the head


258
00:18:19,600 --> 00:18:22,040
which he moulded together to produce


259
00:18:22,040 --> 00:18:25,160
a three-dimensional likeness
of a T rex skull.


260
00:18:31,520 --> 00:18:36,360
Then, painstakingly, millimetre by
millimetre, he followed the contours


261
00:18:36,360 --> 00:18:41,560
on the inside of the skull to reveal
the structure of a T rex brain.


262
00:18:52,400 --> 00:18:55,720
The first time I saw
the individual slices themselves,


263
00:18:55,720 --> 00:18:57,800
they didn't seem all that exciting.


264
00:18:57,800 --> 00:19:00,160
It wasn't until I built
the first animation,


265
00:19:00,160 --> 00:19:03,560
the first flip through a bunch of
slices all going through the skull,


266
00:19:03,560 --> 00:19:06,160
that was when it really struck me


267
00:19:06,160 --> 00:19:08,320
that there were a lot of things
here to see.


268
00:19:10,600 --> 00:19:16,160
The CT scans revealed something
scientists had never before been
able to see in such detail.


269
00:19:20,600 --> 00:19:24,280
Protruding from the delicate network
of brain tissue,


270
00:19:24,280 --> 00:19:25,680
was the optic nerve.


271
00:19:28,360 --> 00:19:32,040
This nerve was
responsible for relaying information


272
00:19:32,040 --> 00:19:35,200
from the eyes to
the visual centres in the brain.


273
00:19:37,280 --> 00:19:40,520
And it was big enough to carry
a LOT of information.


274
00:19:43,360 --> 00:19:46,000
The scans seemed to confirm T rex
did indeed


275
00:19:46,000 --> 00:19:49,680
have a key attribute
of a skilled predator.


276
00:19:49,680 --> 00:19:54,200
It would have been able to seek out
its prey at a distance


277
00:19:54,200 --> 00:19:57,920
and destroy it with
the accuracy of an assassin.


278
00:20:04,040 --> 00:20:08,040
T rex could see its prey, but
that didn't automatically make it


279
00:20:08,040 --> 00:20:09,880
an efficient killer.


280
00:20:09,880 --> 00:20:12,120
To get to grips
with its enormous jaws,


281
00:20:12,120 --> 00:20:15,120
scientists devised
a risky experiment.


282
00:20:15,120 --> 00:20:16,880
Watcha, watcha.


283
00:20:19,240 --> 00:20:21,320
Gators and crocodiles
make a great model


284
00:20:21,320 --> 00:20:23,280
for studying
the feeding biomechanics


285
00:20:23,280 --> 00:20:24,920
of extinct theropod dinosaurs.


286
00:20:24,920 --> 00:20:29,320
They have very similar musculature,
and the basic leverage of their jaws


287
00:20:29,320 --> 00:20:33,640
and things like that are just a good
analogy for tyrannosaur feeding.


288
00:20:36,760 --> 00:20:38,880
OK, grab that pole!


289
00:20:38,880 --> 00:20:39,920
Let's go.


290
00:20:42,600 --> 00:20:46,880
Watch your feet, watch your feet.
Remember she can run forward.


291
00:20:46,880 --> 00:20:50,120
One, two, three...go, go, go!


292
00:20:50,120 --> 00:20:51,880
Watch your feet, Ray.


293
00:20:51,880 --> 00:20:55,880
This is a female American crocodile,
Stevie.


294
00:20:55,880 --> 00:20:59,600
A youngster at 31 years old, she's
only half the size she could become.


295
00:20:59,600 --> 00:21:04,360
She may be small,
but her strength is obvious.


296
00:21:04,360 --> 00:21:08,880
Stay in line with her.
Back up, back up, back up!


297
00:21:10,120 --> 00:21:13,560
Back up. Who's got tape?
I have tape.


298
00:21:13,560 --> 00:21:14,920
She's heavy.


299
00:21:14,920 --> 00:21:19,160
Because her jaws are thought to
work in a similar way to T rex jaws,


300
00:21:19,160 --> 00:21:22,320
Erickson plans to measure her bite
to see what it may reveal


301
00:21:22,320 --> 00:21:24,160
about the power
behind a T rex bite.


302
00:21:26,320 --> 00:21:28,920
Yet, as she's small
and he's not tested her before,


303
00:21:28,920 --> 00:21:32,040
he has no idea what
kind of results he'll get.


304
00:21:32,040 --> 00:21:34,320
All the way with that...


305
00:21:34,320 --> 00:21:36,680
I'm all set.


306
00:21:36,680 --> 00:21:39,920
Erickson needs to get the crocodile
to crunch onto


307
00:21:39,920 --> 00:21:42,320
a specially-designed
pressure sensor,


308
00:21:42,320 --> 00:21:45,160
which will record the force
of the bite.


309
00:21:45,160 --> 00:21:46,760
OK, everybody ready?


310
00:21:46,760 --> 00:21:50,240
The tricky bit is getting
the timing right.


311
00:21:50,240 --> 00:21:52,680
The bite needs to be
a spontaneous one.


312
00:21:58,560 --> 00:22:00,520
Here we go. Hang on.


313
00:22:06,480 --> 00:22:10,040
819lbs. Good bite.


314
00:22:10,040 --> 00:22:13,800
An 800-lb bite is comparable to
what a lion could do or


315
00:22:13,800 --> 00:22:17,560
a spotted hyena, which is the bone
crushing champion among mammals.


316
00:22:17,560 --> 00:22:20,720
A very small crocodilian is
capable of doing bite forces


317
00:22:20,720 --> 00:22:24,760
equal to what some of
these large carnivoran mammals do.


318
00:22:24,760 --> 00:22:28,200
If you matched up an equal-sized
crocodile say to a large lion,


319
00:22:28,200 --> 00:22:31,040
the crocodile will bite three times
more forcefully.


320
00:22:31,040 --> 00:22:33,360
Watch your legs.


321
00:22:34,800 --> 00:22:37,800
If jaws like these give
crocodiles a bite force


322
00:22:37,800 --> 00:22:40,000
well above what their weight
implies,


323
00:22:40,000 --> 00:22:43,800
then Erickson believes the same must
have been true of T rex jaws.


324
00:22:43,800 --> 00:22:48,160
His work suggested
the power of a T rex bite


325
00:22:48,160 --> 00:22:52,080
may have been on a scale beyond
anything we have ever seen.


326
00:22:52,080 --> 00:22:53,520
It's not a natural thing


327
00:22:53,520 --> 00:22:57,040
to stick your hand inside
the mouth of a crocodile, but...


328
00:22:57,040 --> 00:22:59,840
Probably shouldn't
try this at home, kids.


329
00:22:59,840 --> 00:23:01,920
To get an idea of how much
more powerful,


330
00:23:01,920 --> 00:23:06,480
Erickson worked on doing more than
just scale up the bite.


331
00:23:06,480 --> 00:23:08,800
Snout width is 14.2.


332
00:23:08,800 --> 00:23:12,920
He measured every physical detail
of his crocodiles to try to map


333
00:23:12,920 --> 00:23:15,800
the differences in skull shape
and body weight


334
00:23:15,800 --> 00:23:19,080
compared to an animal
the size and shape of a T rex.


335
00:23:19,080 --> 00:23:22,120
50.2 head length...


336
00:23:22,120 --> 00:23:26,920
Erickson's preliminary maximum
estimate of a T rex bite


337
00:23:26,920 --> 00:23:30,160
could be as much
as 40,000lbs of force.


338
00:23:32,880 --> 00:23:36,000
That's about 50 times more powerful
than our crocodile.


339
00:23:37,400 --> 00:23:40,680
T rex would have had easily
the most powerful bite


340
00:23:40,680 --> 00:23:43,080
of any animal that has ever lived.


341
00:23:58,320 --> 00:24:01,200
The combination of new finds
and advanced technology


342
00:24:01,200 --> 00:24:04,880
has enabled palaeontologists
to interpret fossils


343
00:24:04,880 --> 00:24:07,280
with greater certainty.


344
00:24:07,280 --> 00:24:10,280
We now know more than ever before


345
00:24:10,280 --> 00:24:13,680
about what dinosaurs looked like,


346
00:24:13,680 --> 00:24:19,400
how fast they grew,
their skill as predators,


347
00:24:19,400 --> 00:24:20,800
and how they moved.


348
00:24:24,920 --> 00:24:28,360
All building a convincing picture


349
00:24:28,360 --> 00:24:31,040
of how the dinosaurs came
to dominate the Earth


350
00:24:31,040 --> 00:24:32,680
for over 160 million years.


351
00:24:41,200 --> 00:24:44,200
160 million years
is a pretty long time


352
00:24:44,200 --> 00:24:47,160
and makes dinosaurs some of the most
successful animals


353
00:24:47,160 --> 00:24:48,920
ever to have walked the Earth.


354
00:24:48,920 --> 00:24:53,200
After all, modern humans have
only been around for
a couple of hundred thousand years.


355
00:24:53,200 --> 00:24:56,480
Evidence of dinosaur life fills
the geological record


356
00:24:56,480 --> 00:24:59,680
but then suddenly,
65 million years ago,


357
00:24:59,680 --> 00:25:01,280
it all disappeared.


358
00:25:01,280 --> 00:25:03,000
The dinosaurs vanished.


359
00:25:07,920 --> 00:25:12,040
Scientists spent years scrutinising
dinosaur bones, looking for answers.


360
00:25:12,040 --> 00:25:16,200
You got something?
Yeah, this is a vertebrae...


361
00:25:18,400 --> 00:25:22,120
They struggled to come up with ideas
to explain the mass extinction.


362
00:25:22,120 --> 00:25:25,280
Perhaps the climate deteriorated,
becoming too hot...


363
00:25:31,760 --> 00:25:32,800
..or too cold.


364
00:25:34,040 --> 00:25:37,040
Or suddenly too wet...


365
00:25:39,000 --> 00:25:40,560
..or too dry.


366
00:25:45,000 --> 00:25:48,040
There were problems
maybe of reproduction


367
00:25:48,040 --> 00:25:51,880
or maybe their eggs were
eaten by the tiny furry mammals.


368
00:25:56,280 --> 00:25:57,520
IT BURPS


369
00:26:00,160 --> 00:26:04,880
Maybe it was God's will or
lack of standing room in the ark.


370
00:26:10,200 --> 00:26:13,520
But it was only when they turned
their attention to rocks,


371
00:26:13,520 --> 00:26:17,480
rather than bones, that scientists
had a breakthrough.


372
00:26:18,800 --> 00:26:23,280
Geologists searching for clues
to the extinction discovered


373
00:26:23,280 --> 00:26:26,920
an unusual layer of clay in
the geological record that marked


374
00:26:26,920 --> 00:26:31,400
the boundary between the time of the
dinosaurs and the time of mammals.


375
00:26:31,400 --> 00:26:35,400
Nobel prize winning physicist
Luiz Alvarez and his team


376
00:26:35,400 --> 00:26:37,160
took up the challenge.


377
00:26:38,440 --> 00:26:41,200
You see this clay layer here,
about a half-inch thick.


378
00:26:41,200 --> 00:26:43,560
That's when the dinosaurs went out.


379
00:26:43,560 --> 00:26:47,160
We really don't know how long
it took, why it's there.


380
00:26:47,160 --> 00:26:51,680
So I said, "Maybe some of the tricks
I know as a physicist


381
00:26:51,680 --> 00:26:54,240
"might help unravel that story."


382
00:26:54,240 --> 00:26:58,320
And we talked about it
for the next couple of weeks


383
00:26:58,320 --> 00:27:01,440
and finally decided to look for
iridium


384
00:27:01,440 --> 00:27:05,400
as a measure of the deposition rate.


385
00:27:08,040 --> 00:27:10,240
A small quantity of the metal
iridium


386
00:27:10,240 --> 00:27:13,560
constantly falls to Earth
from space,


387
00:27:13,560 --> 00:27:16,280
and the team
expected to find only trace amounts.


388
00:27:17,800 --> 00:27:20,920
But their tests showed
something astonishing.


389
00:27:20,920 --> 00:27:23,160
There was so much iridium in
the clay layer


390
00:27:23,160 --> 00:27:26,160
there could only be one source.


391
00:27:28,880 --> 00:27:32,480
Alvarez's radical idea was that
it had been brought to Earth


392
00:27:32,480 --> 00:27:33,960
by a meteorite.


393
00:27:36,000 --> 00:27:40,640
The vast majority of iridium-bearing
meteorites started life as asteroids.


394
00:27:40,640 --> 00:27:43,920
Most of them, in an orbit between
Mars and Jupiter,


395
00:27:43,920 --> 00:27:45,960
never come anywhere near the Earth.


396
00:27:45,960 --> 00:27:48,200
But the theory goes that a few
are occasionally


397
00:27:48,200 --> 00:27:52,480
swung out of line by the enormous
gravitational pull of Jupiter.


398
00:27:54,080 --> 00:27:58,200
A very few of these finish up in
an orbit which crosses the Earth's.


399
00:27:58,200 --> 00:28:02,280
Most of time they pass harmlessly by,
but every now and then, they collide.


400
00:28:04,440 --> 00:28:08,440
Alvarez's theory is that
65 million years ago a huge asteroid,


401
00:28:08,440 --> 00:28:12,960
six miles wide, smashed into
the Earth with devastating effects.


402
00:28:19,520 --> 00:28:23,840
It was this collision, he believes,
that covered the Earth with iridium


403
00:28:23,840 --> 00:28:26,000
and wiped out the dinosaurs.


404
00:28:26,000 --> 00:28:27,840
It's not all that far-fetched.


405
00:28:27,840 --> 00:28:29,320
Only 25,000 years ago,


406
00:28:29,320 --> 00:28:33,200
a much smaller collision caused
Meteor Crater in Arizona.


407
00:28:34,560 --> 00:28:37,960
There are larger impact craters
on the Earth's surface.


408
00:28:37,960 --> 00:28:40,160
Many have been eroded away over time,


409
00:28:40,160 --> 00:28:43,240
and are rather difficult
to recognise.


410
00:28:43,240 --> 00:28:46,160
Nevertheless, so far, over
the whole world, more than 200


411
00:28:46,160 --> 00:28:47,800
have been identified,


412
00:28:47,800 --> 00:28:52,560
but none of these is both the right
age and size for Alvarez's theory.


413
00:28:52,560 --> 00:28:54,480
However, there's an alternative.


414
00:28:54,480 --> 00:28:56,560
The asteroid may have landed
in the sea.


415
00:28:56,560 --> 00:28:58,360
Dr Cesare Emiliani.


416
00:28:58,360 --> 00:29:00,040
We have no evidence at all


417
00:29:00,040 --> 00:29:04,480
of a crater of the size that
this asteroid this should have made


418
00:29:04,480 --> 00:29:07,040
either on land or on
the ocean floor.


419
00:29:07,040 --> 00:29:10,120
This is a map that shows
the structure of the ocean floor.


420
00:29:10,120 --> 00:29:11,920
On the other hand,


421
00:29:11,920 --> 00:29:15,400
we have evidence indicating
that plant life on the continents,


422
00:29:15,400 --> 00:29:20,480
in a broad area ranging from
the Urals to the Rockies,


423
00:29:20,480 --> 00:29:24,680
suffered somewhat,
at the end of the Cretaceous.


424
00:29:24,680 --> 00:29:29,880
While plant life west of the Urals,
from the Urals to the Rockies,


425
00:29:29,880 --> 00:29:31,480
around the North Atlantic,


426
00:29:31,480 --> 00:29:33,800
suffered very little
or nothing at all.


427
00:29:33,800 --> 00:29:38,000
That would seem to indicate that
the point of impact of the asteroid


428
00:29:38,000 --> 00:29:41,120
was somewhere between
the Urals and the Rockies.


429
00:29:41,120 --> 00:29:45,200
We have no crater on land, we have
no crater on the visible ocean floor


430
00:29:45,200 --> 00:29:50,680
but a portion of the ocean floor
since then has disappeared
under the continent.


431
00:29:50,680 --> 00:29:54,280
Because the oceanic crust moves
towards the continents


432
00:29:54,280 --> 00:29:56,960
and then dives under the continents.


433
00:29:56,960 --> 00:29:59,800
There is a substantial chance that
the asteroid


434
00:29:59,800 --> 00:30:02,280
might have hit an area
of the ocean floor


435
00:30:02,280 --> 00:30:04,320
that has since disappeared.


436
00:30:04,320 --> 00:30:08,560
If one were to make a wild guess as
to where the asteroid may have hit,


437
00:30:08,560 --> 00:30:11,560
one would say somewhere in
the North Pacific, round here.


438
00:30:15,960 --> 00:30:19,360
Without finding a crater,
it was hard to prove that it was


439
00:30:19,360 --> 00:30:21,920
an asteroid that had
killed off the dinosaurs.


440
00:30:26,640 --> 00:30:29,400
But, by 1997, scientists realised


441
00:30:29,400 --> 00:30:32,560
they'd been looking
in the wrong place.


442
00:30:32,560 --> 00:30:36,920
A number of circular structures
had been found in the Caribbean.


443
00:30:36,920 --> 00:30:41,720
The shape of islands, circular
structures on the sea floor,


444
00:30:41,720 --> 00:30:43,600
circular geophysical anomalies.


445
00:30:43,600 --> 00:30:47,080
When you're looking for an impact
crater, usually the obvious thing,


446
00:30:47,080 --> 00:30:50,680
because most craters are round, is
looking for something big and round.


447
00:30:52,720 --> 00:30:57,320
One of Hildebrand's suspects was on
the Yucatan peninsula of Mexico.


448
00:30:57,320 --> 00:31:01,200
There the state oil company,
Petrolinas Mexicana, had detected


449
00:31:01,200 --> 00:31:04,320
a strange circular anomaly
in the Earth's gravity field.


450
00:31:11,560 --> 00:31:14,800
Chixulub, the dead centre
of the big round hole,


451
00:31:14,800 --> 00:31:19,560
but at the surface there's
no sign of a catastrophe.


452
00:31:28,800 --> 00:31:32,040
The 200km-wide crater is hidden.


453
00:31:32,040 --> 00:31:35,240
It's buried hundreds of metres
beneath the Earth's surface,


454
00:31:35,240 --> 00:31:39,280
so Hildebrand had to investigate it
in some other way.


455
00:31:39,280 --> 00:31:43,560
We've taken another 1,400
measurements and combined
them with the data that


456
00:31:43,560 --> 00:31:48,720
Petroleos Mexicanos already had to
make this map of the gravity field.


457
00:31:48,720 --> 00:31:52,800
Here you can see all this
concentric circular structure


458
00:31:52,800 --> 00:31:55,040
that represents the crater.


459
00:31:55,040 --> 00:31:59,040
From here to here is about 180km.


460
00:31:59,040 --> 00:32:03,200
Petroleos Mexicanos had known
about this big buried structure
for decades.


461
00:32:03,200 --> 00:32:08,080
They'd drilled several wells into it
for oil exploration,
beginning in 1952.


462
00:32:10,120 --> 00:32:13,880
When they did so, they found what
they thought was volcanic rock.


463
00:32:13,880 --> 00:32:17,920
But this contains shock quartz
and impact glass and so on.


464
00:32:17,920 --> 00:32:20,760
These are the classic signs,


465
00:32:20,760 --> 00:32:23,440
the deposits you'd expect
in a big impact crater.


466
00:32:23,440 --> 00:32:27,120
The rock proved to be precisely
65 million years old -


467
00:32:27,120 --> 00:32:29,360
the age of the mass extinction.


468
00:32:29,360 --> 00:32:34,560
Here at last was the first
confirmation that Chicxulub
was ground zero.


469
00:32:36,720 --> 00:32:41,480
Hildebrand confirmed the theory
proposed 17 years earlier


470
00:32:41,480 --> 00:32:46,560
that a devastating asteroid had hit
Earth 65 million years ago.


471
00:32:53,320 --> 00:32:57,840
By 2004, scientists believed they
had proof that the impact


472
00:32:57,840 --> 00:33:00,120
had caused a massive explosion...


473
00:33:02,240 --> 00:33:08,960
..quickly followed by an enormous
shock wave that had destroyed
life for hundreds of miles around


474
00:33:19,840 --> 00:33:23,720
And there was more.
Investigations of the layer of rock


475
00:33:23,720 --> 00:33:26,400
that marks the time when
the dinosaurs disappeared -


476
00:33:26,400 --> 00:33:28,120
known as the KT boundary -


477
00:33:28,120 --> 00:33:33,240
revealed further evidence of what
had happened in the aftermath.


478
00:33:33,240 --> 00:33:35,400
These are called spherals.


479
00:33:35,400 --> 00:33:39,880
They're actually made of
round rock globules,
so we know they're condensed


480
00:33:39,880 --> 00:33:46,320
from a very hot vapour cloud.
And some of the mineralogy in there


481
00:33:46,320 --> 00:33:51,080
tells us these globules originated
at very high temperatures.


482
00:33:52,520 --> 00:33:53,720
That's exciting.


483
00:33:53,720 --> 00:33:57,520
You know something hot happened
and hot is associated
with an impact.


484
00:34:00,840 --> 00:34:04,560
The spherals were evidence
that the fireball had vaporised


485
00:34:04,560 --> 00:34:07,040
billions of tons of rock.


486
00:34:07,040 --> 00:34:11,440
In outer space, the vapour condensed
into tiny droplets which fell back


487
00:34:11,440 --> 00:34:15,120
all over the Earth
as white hot spherals.


488
00:34:20,280 --> 00:34:24,000
From America to New Zealand
there seemed to be


489
00:34:24,000 --> 00:34:28,000
evidence of massive burning
at time of impact.


490
00:34:28,000 --> 00:34:31,080
It looked as if the world's forests
had spontaneously ignited,


491
00:34:31,080 --> 00:34:36,240
as the spherals heated
the atmosphere by up to
1,000 degrees centigrade.


492
00:34:38,000 --> 00:34:42,440
If we're looking at 600, 1,000
degrees, then this would instantly


493
00:34:42,440 --> 00:34:45,840
have ignited all the plant matter
across the world


494
00:34:45,840 --> 00:34:51,880
and it just would have
been sent up in flames.


495
00:34:51,880 --> 00:34:57,040
The impact was also thought
to have created vicious acid rain.


496
00:34:59,840 --> 00:35:03,680
The fireball had release chemicals,
which turned the water deadly.


497
00:35:05,120 --> 00:35:08,000
It was suggested that
the acid rain had a pH


498
00:35:08,000 --> 00:35:10,160
so low it was like battery acid.


499
00:35:10,160 --> 00:35:12,600
If you had something that low,


500
00:35:12,600 --> 00:35:15,040
it would literally burn
everything on the land


501
00:35:15,040 --> 00:35:18,200
from plants, to dinosaurs
to everything else.


502
00:35:19,800 --> 00:35:23,480
Then there was the final clue
from the KT boundary -


503
00:35:23,480 --> 00:35:26,440
a high concentration of fern spores.


504
00:35:31,240 --> 00:35:37,480
Ferns flourish whenever all other
plants have been killed off by
some environmental devastation.


505
00:35:39,920 --> 00:35:44,880
So the predominance of fern spores -
known as a fern spike -


506
00:35:44,880 --> 00:35:48,280
suggested something had wiped out
every plant on the planet.


507
00:35:51,080 --> 00:35:55,000
Fern spikes were found all over
the world, such as in New Zealand.


508
00:35:55,000 --> 00:35:57,960
This, I think, became stronger
and stronger evidence


509
00:35:57,960 --> 00:36:01,080
that there was something LIKE
global darkness caused by an impact.


510
00:36:04,160 --> 00:36:08,000
So the theory grew up
that vast amounts of dust
created by the impact


511
00:36:08,000 --> 00:36:10,480
must have blocked out the sun.


512
00:36:11,760 --> 00:36:17,040
This could have plunged
the world into freezing darkness
for months or years.


513
00:36:19,880 --> 00:36:24,560
Any dinosaurs that escaped burning
either froze or starved to death.


514
00:36:34,720 --> 00:36:37,960
The mystery surrounding the death
of the dinosaurs


515
00:36:37,960 --> 00:36:41,360
finally appeared
to have been solved.


516
00:36:43,960 --> 00:36:46,880
A number of factors may have
influenced the extinction,


517
00:36:46,880 --> 00:36:51,520
but research had shown that
the impact at Chicxulub
WAS the crucial factor.


518
00:36:59,040 --> 00:37:02,760
We should probably be thankful
for that mighty asteroid -


519
00:37:02,760 --> 00:37:05,400
if the dinosaurs hadn't
been wiped out,


520
00:37:05,400 --> 00:37:08,440
mammals may never have flourished
and we might not exist.


521
00:37:08,440 --> 00:37:11,680
So what would have happened if
an asteroid hadn't hit the Earth


522
00:37:11,680 --> 00:37:14,400
and the dinosaurs had survived?


523
00:37:14,400 --> 00:37:18,640
It's a thought that's given rise
to some novel ideas.


524
00:37:18,640 --> 00:37:22,480
I think that some dinosaurs, like
some mammals would have become


525
00:37:22,480 --> 00:37:25,360
increasingly intelligent
at a geometric rate,


526
00:37:25,360 --> 00:37:26,920
as did our own ancestors,


527
00:37:26,920 --> 00:37:30,920
and I think, possibly, by this
time the dinosaurs themselves


528
00:37:30,920 --> 00:37:34,560
would have approached our own level
of brain development.


529
00:37:34,560 --> 00:37:36,560
A sculptor at our museum


530
00:37:36,560 --> 00:37:39,880
and myself have collaborated over
the last several months in trying


531
00:37:39,880 --> 00:37:43,400
to estimate what the appearance
of one of these highly encephalised


532
00:37:43,400 --> 00:37:46,680
or intelligent dinosaurs might have
been, a dinosaur for the 1980s,


533
00:37:46,680 --> 00:37:50,600
and here is an example of what
we think it may have looked like.


534
00:37:56,640 --> 00:37:59,920
Their model of a 20th-century
dinosaur incorporates


535
00:37:59,920 --> 00:38:03,320
many features of the original
reptiles - the binocular vision,


536
00:38:03,320 --> 00:38:08,280
the absence of an external ear,
a deep chest cavity with ribs


537
00:38:08,280 --> 00:38:10,240
all the way down the abdomen,


538
00:38:10,240 --> 00:38:13,600
opposable fingers and
no external genitalia.


539
00:38:13,600 --> 00:38:16,680
But it looks closer to a human being
than a brontosaurus.


540
00:38:16,680 --> 00:38:20,280
In building it, have they perhaps
unwittingly favoured our own kind?


541
00:38:20,280 --> 00:38:21,720
I don't think so.


542
00:38:21,720 --> 00:38:26,880
I think just as the birds,
bats and flying reptiles all have


543
00:38:26,880 --> 00:38:31,800
a crudely avian form, so too there
is a meaning to the human form.


544
00:38:31,800 --> 00:38:34,840
So that we are, in effect,
adapted to interact with


545
00:38:34,840 --> 00:38:38,720
an environment as highly
encephalised bipeds


546
00:38:38,720 --> 00:38:41,200
or walking animals with
a very large brain.


547
00:38:41,200 --> 00:38:45,200
So perhaps were it not for a chance
collision with an asteroid,


548
00:38:45,200 --> 00:38:48,320
creatures like this could be
ruling the world today


549
00:38:48,320 --> 00:38:51,120
just as they did all those
millions of years ago.


550
00:38:53,480 --> 00:38:56,480
Let's imagine that the dinosaurs
really did become some sort


551
00:38:56,480 --> 00:38:59,680
of dinosauroid, the great rock
doesn't fall out of the sky,


552
00:38:59,680 --> 00:39:02,840
there's a bright light in the sky,
the dinosaur says, "What's that?


553
00:39:02,840 --> 00:39:07,440
"No idea". The mass extinction
is postponed. In fact, cancelled.


554
00:39:07,440 --> 00:39:08,800
So what's happening then?


555
00:39:08,800 --> 00:39:11,760
We've got the Apes rapidly evolving
and they're beginning to


556
00:39:11,760 --> 00:39:14,920
look over their shoulders because
just conceivably there are also


557
00:39:14,920 --> 00:39:18,520
these dinosauroids doing
rather similar things.


558
00:39:18,520 --> 00:39:20,600
What would have happened?


559
00:39:20,600 --> 00:39:24,320
Would it have been an evolutionary
race? Maybe there would
have been a winner?


560
00:39:24,320 --> 00:39:29,160
Or maybe, unbelievably, madly, there
could have been a co-operation.


561
00:39:31,040 --> 00:39:36,320
The Utopian notion
of dinosaurs and humans
sharing the planet may appeal,


562
00:39:36,320 --> 00:39:38,400
even be plausible to some,


563
00:39:38,400 --> 00:39:43,760
but most palaeontologists
see the dinosauroid as an insult
to dinosaurs.


564
00:39:43,760 --> 00:39:45,840
There's probably some
good ideas there.


565
00:39:45,840 --> 00:39:48,240
The brain was getting bigger,
and they probably


566
00:39:48,240 --> 00:39:51,720
would have continued to
outcompete other animals.


567
00:39:53,920 --> 00:39:58,880
But for them to become
fully erect like humans
is a little bit fanciful.


568
00:40:00,120 --> 00:40:03,240
Dinosaurs would have continued
to develop, to specialise.


569
00:40:03,240 --> 00:40:07,080
They would have adapted,
but they would have adapted


570
00:40:07,080 --> 00:40:11,240
and specialised as dinosaurs, they
wouldn't have become primate-like.


571
00:40:11,240 --> 00:40:16,320
The idea that a dinosauroid could
exist as a scientific question...


572
00:40:16,320 --> 00:40:19,520
is bogus.
It's about as bogus as it gets.


573
00:40:19,520 --> 00:40:25,200
It is fairly arrogant to think
the endpoint of evolution


574
00:40:25,200 --> 00:40:28,280
should emulate human beings.


575
00:40:32,600 --> 00:40:34,680
If the asteroid had never hit,


576
00:40:34,680 --> 00:40:38,600
life on Earth could have been
very different.


577
00:40:52,520 --> 00:40:55,400
But that's all just
crazy speculation.


578
00:40:55,400 --> 00:40:59,440
Everyone now knows that dinosaurs
were wiped out 65 million years ago


579
00:40:59,440 --> 00:41:03,000
and none of them survived that
catastrophic asteroid impact.


580
00:41:03,000 --> 00:41:04,600
Or did they?


581
00:41:04,600 --> 00:41:07,760
The idea that dinosaurs may
have evolved into something else


582
00:41:07,760 --> 00:41:10,400
was one that had been doing
the rounds for many years.


583
00:41:10,400 --> 00:41:13,720
But it began to gather momentum
when some palaeontologists


584
00:41:13,720 --> 00:41:18,680
began to increasingly suspect
that dinosaurs might still be alive.


585
00:41:34,840 --> 00:41:40,000
The Natural History Museum, London.
Within these hallowed halls


586
00:41:40,000 --> 00:41:43,640
lies the fossil that first
hinted at the origin of birds.


587
00:41:43,640 --> 00:41:47,000
Discovered in Germany 100 ago,


588
00:41:47,000 --> 00:41:50,040
superstitious quarry workers
thought it was a fallen angel.


589
00:41:58,040 --> 00:42:02,560
Archaeopteryx turned out to be
something almost as remarkable.


590
00:42:02,560 --> 00:42:06,840
The size of a pigeon, it possessed
teeth, a long, bony tail,


591
00:42:06,840 --> 00:42:11,280
and claws on its arms.
All features of reptiles.


592
00:42:11,280 --> 00:42:14,440
At the same time,
it was very much like a bird.


593
00:42:16,040 --> 00:42:20,160
It actually has impressions of
the wing feathers, both wings


594
00:42:20,160 --> 00:42:25,200
and long tail feathers,
but the tail has a long set of bones


595
00:42:25,200 --> 00:42:29,080
running down it as well, which
modern birds don't have at all.


596
00:42:29,080 --> 00:42:33,040
So Archaeopteryx really does
seem to be a primitive bird.


597
00:42:34,400 --> 00:42:37,640
These fossils, I find it exciting
to look at them


598
00:42:37,640 --> 00:42:41,680
because they have so much
scientific information in them,


599
00:42:41,680 --> 00:42:45,280
but they're very beautiful objects
to look at in their own right.


600
00:42:45,280 --> 00:42:49,640
They really are an exceptional
snapshot record of evolution.


601
00:42:55,000 --> 00:42:58,600
That fossil was to be the key
to something that John Ostrom


602
00:42:58,600 --> 00:43:01,200
had been thinking about for decades.


603
00:43:02,640 --> 00:43:05,200
When he'd first described
Deinonychus in the 1960s,


604
00:43:05,200 --> 00:43:10,800
he'd noticed that its skeleton was
strangely similar to that of a bird.


605
00:43:12,800 --> 00:43:16,080
Archaeopteryx helped him
refine his ideas.


606
00:43:16,080 --> 00:43:18,240
Neat animal, isn't it?


607
00:43:20,200 --> 00:43:22,040
I think so.


608
00:43:22,040 --> 00:43:25,360
And what made me even more excited


609
00:43:25,360 --> 00:43:28,080
was when I saw structures
in that animal


610
00:43:28,080 --> 00:43:30,360
that I subsequently recognised


611
00:43:30,360 --> 00:43:33,520
in Archaeopteryx.


612
00:43:33,520 --> 00:43:38,520
This is the Solnhofen Archaeopteryx.
The Solnhofen specimen, yeah.


613
00:43:40,240 --> 00:43:43,280
John Ostrom's crucial
realisation was that


614
00:43:43,280 --> 00:43:49,680
his beloved Deinonychus
shared many anatomical features
with Archaeopteryx.


615
00:43:49,680 --> 00:43:53,800
He compared in detail the skeletons
of predatory dinosaurs,


616
00:43:53,800 --> 00:43:55,680
Archaeopteryx and modern birds.


617
00:43:55,680 --> 00:44:00,600
He found a whole
set of similarities -
most notably in the skull,


618
00:44:00,600 --> 00:44:02,280
the hind limbs and the forearms.


619
00:44:02,280 --> 00:44:07,160
For a start, they all have
the same number of fingers.


620
00:44:07,160 --> 00:44:10,080
This is the skeleton
of a modern pigeon.


621
00:44:10,080 --> 00:44:13,120
Three fingers in the hand
of a modern bird,


622
00:44:13,120 --> 00:44:18,680
three fingers preserved in the hand
of Deinonychus, and that particular


623
00:44:18,680 --> 00:44:23,920
kind of hand morphology
is also supplemented by


624
00:44:23,920 --> 00:44:28,400
the strange wrist bone that
allows for the flexibility


625
00:44:28,400 --> 00:44:30,720
that produces the flapping strokes.


626
00:44:30,720 --> 00:44:34,200
The similarities between birds


627
00:44:34,200 --> 00:44:39,000
and predaceous dinosaurs
is amazing to me.


628
00:44:41,400 --> 00:44:44,720
But, as with all
groundbreaking new theories,


629
00:44:44,720 --> 00:44:47,320
Ostrom's idea had its detractors.


630
00:44:49,320 --> 00:44:53,480
The dinosaur-bird theory has
tremendous popular appeal,


631
00:44:53,480 --> 00:44:58,240
one can vicariously study dinosaurs
at the back yard bird feeder,


632
00:44:58,240 --> 00:45:04,360
and one can buy a piece
of dinosaur leg at the local
Kentucky Fried Chicken.


633
00:45:04,360 --> 00:45:08,400
So it has tremendous appeal
to the public.


634
00:45:08,400 --> 00:45:10,400
Unfortunately, it seems to be wrong.


635
00:45:12,520 --> 00:45:17,720
Alan Feduccia argued that
birds evolved long before
dinosaurs came along.


636
00:45:17,720 --> 00:45:20,680
They descended from much more
primitive reptiles,


637
00:45:20,680 --> 00:45:24,840
and any similarity between birds and
predatory dinosaurs was superficial.


638
00:45:24,840 --> 00:45:29,440
They resembled each other because
they both walked on their hind legs,


639
00:45:29,440 --> 00:45:32,040
not because
they were closely related.


640
00:45:36,120 --> 00:45:39,520
Such vocal sceptics were going
to need better proof


641
00:45:39,520 --> 00:45:43,920
if they were to be convinced
of the dinosaur-to-bird theory.


642
00:45:50,480 --> 00:45:54,800
And in 1999 in Tucson, Arizona,
fossil collectors thought


643
00:45:54,800 --> 00:45:58,120
they might have come across
a specimen that fitted the bill.


644
00:46:04,640 --> 00:46:07,840
I carried it out to the light


645
00:46:07,840 --> 00:46:11,040
of the sunlight so
that I could see it cross lit.


646
00:46:14,800 --> 00:46:18,200
And there were a number of
beautiful teeth in this skull.


647
00:46:18,200 --> 00:46:20,360
And that was very exciting.


648
00:46:20,360 --> 00:46:25,400
And then we studied also the tail
that was a dinosaur...


649
00:46:25,400 --> 00:46:27,080
a very dinosaur-like tail.


650
00:46:27,080 --> 00:46:30,320
I got this incredible high feeling,


651
00:46:30,320 --> 00:46:33,960
the feeling of discovery -
that wonderful time


652
00:46:33,960 --> 00:46:36,800
when everything clicks
into position.


653
00:46:38,640 --> 00:46:41,520
The two fossil dealers thought
they could be looking at


654
00:46:41,520 --> 00:46:44,440
one of the most
important fossils ever found.


655
00:46:44,440 --> 00:46:46,800
A specimen that would prove
beyond doubt


656
00:46:46,800 --> 00:46:51,400
one of the most controversial
theories in all of evolution.


657
00:46:51,400 --> 00:46:55,560
This fossil,
this clearly cross between a bird


658
00:46:55,560 --> 00:47:00,080
and a dinosaur was what everybody
had been looking for.


659
00:47:00,080 --> 00:47:02,840
And here it was, right there,
right in front of my eyes,


660
00:47:02,840 --> 00:47:04,920
and I was one of the first
people to see it.


661
00:47:07,080 --> 00:47:08,840
I looked it over very carefully.


662
00:47:08,840 --> 00:47:10,720
Literally under a magnifying glass.


663
00:47:10,720 --> 00:47:14,560
And I was looking for any tell-tale
features, particularly on the tail.


664
00:47:14,560 --> 00:47:16,720
I wanted to look at that tail
very carefully


665
00:47:16,720 --> 00:47:20,040
because it was very clearly
a dinosaur tail.


666
00:47:22,160 --> 00:47:25,200
The world of palaeontology
was gripped


667
00:47:25,200 --> 00:47:28,640
and a team of experts was
assembled to investigate.


668
00:47:35,120 --> 00:47:39,520
After several months, they confirmed
that it was the missing link.


669
00:47:39,520 --> 00:47:43,560
It had a bird-like front and legs,
and a dinosaur-like tail.


670
00:47:47,400 --> 00:47:49,480
They called it Archaeoraptor,


671
00:47:49,480 --> 00:47:50,960
ancient hunter,


672
00:47:50,960 --> 00:47:53,200
and proudly presented it
to the world.


673
00:47:56,320 --> 00:48:00,240
Scientists could now say that
dinosaurs evolved into birds.


674
00:48:00,240 --> 00:48:04,320
One of the most important theories
in evolution was finally proved.


675
00:48:10,680 --> 00:48:12,720
But not everyone was convinced.


676
00:48:20,320 --> 00:48:24,320
At the university of Texas,
Tim Rowe had used a CAT scan


677
00:48:24,320 --> 00:48:26,200
to study the fossil.


678
00:48:26,200 --> 00:48:31,560
The results threw up
some serious questions about
how it fitted together.


679
00:48:31,560 --> 00:48:33,200
I'm going to show you two slices.


680
00:48:33,200 --> 00:48:35,760
The first is this slice here
through the skull


681
00:48:35,760 --> 00:48:38,080
and these other elements here,


682
00:48:38,080 --> 00:48:41,840
and the second slice will be back
through the ankle and tail,


683
00:48:41,840 --> 00:48:44,960
this critical region here
through one of the legs.


684
00:48:46,800 --> 00:48:49,480
When we go to these slices,
here's what we see.


685
00:48:49,480 --> 00:48:51,400
Here's the skull.


686
00:48:51,400 --> 00:48:55,120
We can see the skull is part
of this upper layer of shale.


687
00:48:56,240 --> 00:48:59,040
And you can see
the fracture pattern here,


688
00:48:59,040 --> 00:49:01,840
here's very tight fractures
that fit together.


689
00:49:01,840 --> 00:49:05,160
Here, a pair of fractures,
one occurring against the next.


690
00:49:05,160 --> 00:49:06,240
A straight fracture.


691
00:49:06,240 --> 00:49:10,480
The pieces on either side are
the same thickness. Same density.


692
00:49:10,480 --> 00:49:12,520
But when we get to the edge
of the block,


693
00:49:12,520 --> 00:49:14,320
this piece is a little bit thicker


694
00:49:14,320 --> 00:49:18,160
and denser than the piece
it's glued against.


695
00:49:19,640 --> 00:49:22,400
As we move to the tail,
to the critical area,


696
00:49:22,400 --> 00:49:25,920
we can see that it's completely
surrounded by grout,


697
00:49:25,920 --> 00:49:29,240
and that there are no natural
ties between the tail piece


698
00:49:29,240 --> 00:49:32,440
and this piece to the right or left.


699
00:49:32,440 --> 00:49:35,320
In fact, it's just swimming
in this ocean of grout here.


700
00:49:35,320 --> 00:49:40,160
And as we map through the entire
specimen, we found no verifiable fits


701
00:49:40,160 --> 00:49:44,760
between the tail and any of the other
parts anywhere else in the specimen.


702
00:49:49,680 --> 00:49:53,600
The scan clearly showed
what the naked eye couldn't see.


703
00:49:53,600 --> 00:49:57,560
There was no natural skeletal link
between the all-important tail


704
00:49:57,560 --> 00:49:59,360
and the rest of the fossil.


705
00:50:00,560 --> 00:50:04,080
It had simply been glued on
with grout.


706
00:50:10,720 --> 00:50:13,640
The vital evidence that seemed to
prove the link between birds


707
00:50:13,640 --> 00:50:15,880
and dinosaurs was a fake.


708
00:50:21,560 --> 00:50:26,160
The dinosaur fake was
a dreadful blow for supporters
of the bird theory.


709
00:50:26,160 --> 00:50:29,720
But scientists who were committed
to the idea refused to give up.


710
00:50:29,720 --> 00:50:33,080
They were determined to keep
looking for proof.


711
00:50:35,560 --> 00:50:37,680
Although the fossil had been a fake,


712
00:50:37,680 --> 00:50:41,200
its front half was
a new kind of primitive bird.


713
00:50:43,520 --> 00:50:47,040
Fossil hunters flocked to the region
where it had been found.


714
00:50:47,040 --> 00:50:49,120
And they struck gold.


715
00:50:58,600 --> 00:51:02,600
Extraordinary, well preserved
fossils revealed dinosaurs


716
00:51:02,600 --> 00:51:05,640
and birds not only shared
features like downy feathers,


717
00:51:05,640 --> 00:51:10,360
but also hollow bones and
similar pelvises and hind limbs.


718
00:51:27,240 --> 00:51:30,160
On a remote farm in Colorado,


719
00:51:30,160 --> 00:51:33,080
palaeontologist Brent Breithaupt
presented even more proof


720
00:51:33,080 --> 00:51:37,120
of the close relationship between
the ancient fossils and birds.


721
00:51:40,880 --> 00:51:43,880
Very good. That should make
an excellent track.


722
00:51:43,880 --> 00:51:48,000
Here we have two tracks
that we recently made.


723
00:51:48,000 --> 00:51:51,400
This one here is from the Red Gulch
Dinosaur Tracksite.


724
00:51:51,400 --> 00:51:56,400
This one here preserves
the three-toe impressions,


725
00:51:56,400 --> 00:52:00,200
tridactyl impressions,
of the foot of the dinosaurs.


726
00:52:00,200 --> 00:52:03,920
The small to medium sized theropod
dinosaurs that lived up there.


727
00:52:03,920 --> 00:52:10,960
Now, over here, we have one
that we just got from this site.


728
00:52:10,960 --> 00:52:14,040
Again, a nice tridactyl footprint.


729
00:52:14,040 --> 00:52:16,200
Again, very well preserved.


730
00:52:16,200 --> 00:52:19,840
If we compare both casts,


731
00:52:19,840 --> 00:52:24,520
we can see these particular tracks
look very, very much the same.


732
00:52:25,720 --> 00:52:30,840
But these footprints are
not of a theropod that died
65 million years ago...


733
00:52:32,320 --> 00:52:34,840
These are only a few hours old.


734
00:52:37,160 --> 00:52:39,840
There's dinosaurs
in them there hills.


735
00:52:42,160 --> 00:52:45,400
In fact, dinosaurs are everywhere.


736
00:52:54,080 --> 00:52:57,040
For the first time
on network television,


737
00:52:57,040 --> 00:53:03,160
palaeontologist Julia Clarke
is about to perform
an autopsy on a dinosaur.


738
00:53:05,480 --> 00:53:09,760
Only you are more likely
to know it...


739
00:53:09,760 --> 00:53:11,600
as a roast turkey.


740
00:53:13,640 --> 00:53:17,320
Because you see,
birds ARE dinosaurs.


741
00:53:17,320 --> 00:53:21,320
So today we're going to dissect
the evidence that birds


742
00:53:21,320 --> 00:53:24,240
are living dinosaurs
from this turkey.


743
00:53:27,280 --> 00:53:30,760
What we're pulling off here
is the major flight muscle,


744
00:53:30,760 --> 00:53:35,320
supracoracoideus that is in
velociraptor and oviraptor.


745
00:53:37,080 --> 00:53:41,880
One of the features you see is that
the second finger is the longest.


746
00:53:41,880 --> 00:53:46,160
This is a feature we see going back
as far as early dinosaurs,


747
00:53:46,160 --> 00:53:48,320
even Triassic forms.


748
00:53:54,920 --> 00:53:59,560
We're all familiar with wishbones,
from any kind of turkey meal.


749
00:53:59,560 --> 00:54:04,680
Wishbones actually are one of the
most intuitive pieces of evidence


750
00:54:04,680 --> 00:54:08,240
that birds are living dinosaurs,
because we have wishbones now


751
00:54:08,240 --> 00:54:13,720
from a variety of theropod dinosaurs,
including relatives of tyrannosaurus


752
00:54:13,720 --> 00:54:18,360
and velociraptor, and even earlier
dinosaurs such as coelophysis.


753
00:54:22,080 --> 00:54:27,440
Yes, just as we share 98%
of our DNA with chimps,


754
00:54:27,440 --> 00:54:31,160
turkeys - in fact all modern birds -


755
00:54:31,160 --> 00:54:34,600
are direct descendants
of theropod dinosaurs.


756
00:54:44,520 --> 00:54:49,160
And the freshly-made dinosaur
tracks in the hills of Colorado?


757
00:54:51,320 --> 00:54:52,720
Emus.


758
00:54:55,160 --> 00:54:58,840
Inwardly, outwardly,
even in the way they move,


759
00:54:58,840 --> 00:55:03,400
the similarities between
theropod dinosaurs and birds
are numerous.


760
00:55:03,400 --> 00:55:07,600
But, being warm-blooded,
their ultimate success


761
00:55:07,600 --> 00:55:11,960
was in an evolutionary solution
to the need to keep warm.


762
00:55:11,960 --> 00:55:15,680
Large dinosaurs really don't have
a problem with body heat.


763
00:55:15,680 --> 00:55:19,320
If they have a problem, it's
getting rid of excess body heat.


764
00:55:19,320 --> 00:55:21,520
But small dinosaurs
have this problem.


765
00:55:21,520 --> 00:55:23,760
They're losing their heat
all the time.


766
00:55:23,760 --> 00:55:26,400
So it would be a good thing
if a small dinosaur was


767
00:55:26,400 --> 00:55:30,440
warm-blooded, for it to have some
kind of insulation on its body.


768
00:55:30,440 --> 00:55:35,480
It started with the development
of thin, downy filaments.


769
00:55:35,480 --> 00:55:39,560
In time, those filaments
strengthened and thickened.


770
00:55:39,560 --> 00:55:44,240
As non-flying birds,
emus are one of the best examples


771
00:55:44,240 --> 00:55:48,160
of feathers as they were originally
designed. As an insulating layer.


772
00:55:49,880 --> 00:55:53,520
Once you have those long feathers,
then of course it does give you


773
00:55:53,520 --> 00:55:55,600
an aerodynamic advantage as well.


774
00:55:55,600 --> 00:56:00,240
And if you have that advantage,
then selection starts working
on that advantage.


775
00:56:00,240 --> 00:56:04,360
And it may well be that that
was forcing these feathers
to become longer


776
00:56:04,360 --> 00:56:08,120
and longer until finally that animal
not only jumped across the ditch,


777
00:56:08,120 --> 00:56:11,840
it actually flapped its arms
and flew across the ditch.


778
00:56:11,840 --> 00:56:13,960
And so it seems that flight,
far from being


779
00:56:13,960 --> 00:56:19,160
the reason for the evolution
of feathers, may have been
a by-product.


780
00:56:19,160 --> 00:56:22,120
But with it, some dinosaurs
were already adapting in ways


781
00:56:22,120 --> 00:56:26,000
that would equip them for life
after the meteorite impact.


782
00:56:28,600 --> 00:56:32,800
The fact of the matter is
that the age of the dinosaurs
never actually ended.


783
00:56:32,800 --> 00:56:37,880
Dinosaurs DID survive
the cataclysmic event of
65 million years ago.


784
00:56:40,480 --> 00:56:44,160
So when we talk about dinosaurs
living with us today,


785
00:56:44,160 --> 00:56:49,320
and the fanciful notion
of what it would be like,
it's not so much fantasy.


786
00:56:49,320 --> 00:56:50,920
They're right there.


787
00:56:50,920 --> 00:56:54,160
Dinosaurs have not only survived,
there are far more species of them


788
00:56:54,160 --> 00:56:59,360
on the Earth today than there are
mammals. They're not the biggest
animals any more,


789
00:56:59,360 --> 00:57:03,680
but still there's over 10,000 living
species of descendents of dinosaurs.


790
00:57:03,680 --> 00:57:07,400
They didn't actually go extinct
at the end of the Cretaceous period


791
00:57:07,400 --> 00:57:10,160
like everybody thinks.
They're outside flying around.


792
00:57:10,160 --> 00:57:14,040
You can't go into a forest
without hearing dinosaurs.


793
00:57:14,040 --> 00:57:18,760
In that sense, maybe they won out,


794
00:57:18,760 --> 00:57:21,040
and we just think we're on top.


795
00:57:26,840 --> 00:57:29,560
Over the last half-century,


796
00:57:29,560 --> 00:57:33,080
scientists have hunted all over
the world for new clues


797
00:57:33,080 --> 00:57:38,480
to help them piece together
the fragments which reveal
the life of the dinosaurs.


798
00:57:38,480 --> 00:57:41,720
They've come up with
ingenious new ways of working out


799
00:57:41,720 --> 00:57:45,120
how the dinosaurs lived and behaved,


800
00:57:45,120 --> 00:57:49,960
made extraordinary discoveries,


801
00:57:49,960 --> 00:57:55,600
and battled to answer some of the
oldest, most vital questions of all.


802
00:57:59,080 --> 00:58:02,120
But there are still things
we don't know,


803
00:58:02,120 --> 00:58:05,000
mysteries to be solved,
and one of the exciting things


804
00:58:05,000 --> 00:58:07,560
about palaeontology is that,
in an instant,


805
00:58:07,560 --> 00:58:10,240
perhaps with just the tiniest
of discoveries,


806
00:58:10,240 --> 00:58:13,520
everything we think we know
about dinosaurs today


807
00:58:13,520 --> 00:58:14,920
could all change again.


808
00:58:14,920 --> 00:58:17,440
There are always new discoveries
out there...


809
00:58:17,440 --> 00:58:18,840
waiting to be found.


810
00:58:34,960 --> 00:58:38,320
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811
00:58:38,320 --> 00:58:41,520
Email subtitling@bbc.co.uk