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NARRATOR: For millions of
years, they ruled the Earth.

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The dinosaurs were the
largest creatures ever

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to walk the face of the planet.

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[THUNDER CRACKS]

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Today, only their fossilized
bones remain in the badlands

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of Montana and North Dakota.

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This is a dinosaurs graveyard.

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Everywhere bones jut
from rocks and buttes.

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But why, after
150 million years,

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did the dinosaurs die out?

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Does this line of
crumbling rock mark the end

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of the age of the dinosaurs?

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Do these barren hills hold
a snapshot of the moment

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when a species died forever?

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And is the doom of the
dinosaurs linked to a literally

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earth-shattering discovery
made by an oil prospector

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off the coast of Mexico?

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Mysteries from the files
of Arthur C Clarke,

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author of "2001" and inventor
of the communications satellite.

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Now in retreat in Sri Lanka,
he ponders the riddles

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of this and other worlds.

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[THEME MUSIC]

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I'd like you to meet some
extraordinary survivors.

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A few years ago, turtles
like these faced extinction.

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Their eggs were the favorite
food of local people,

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and only a few were
allowed to hatch.

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Today, they're protected
in sanctuaries like this,

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and hundreds of
thousands of them

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have been able to grow to
safety before being released

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back into the Indian Ocean.

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And they are survivors
in another sense.

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Turtles almost like
these flourished along

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with the dinosaurs
in prehistoric times.

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As you can see, the
turtles are still with us,

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but the dinosaurs died
out 65 million years ago.

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No one knows why.

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It's the biggest
whodunnit of all time,

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and rival teams of
scientists have been trying

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to find the murder weapon.

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NARRATOR: In this remote
country, the badlands

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of Montana and North
Dakota, the Hell Creek rocks

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are the pages of an
open for dinosaur

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hunters and paleontologists
like Kirk Johnson.

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Within these rocks lie clues
to the Earth's history,

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and Johnson believes, to
the extinction of dinosaurs.

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It's here among the fossils that
he hopes to find the answer,

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in the bones of the
dinosaurs, and in the now

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petrified leaves that they ate.

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Now, that's a spectacular
example of one of the two

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[INAUDIBLE]
liriodendrites bradacci,

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which is the most common
species at this locality.

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Let's see what we have here.

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See the bones sticking
right out the top here?

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A vertebrae of one
of the dinosaurs.

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You see it's
cracking up already.

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We leave it here, it's
just gonna weather out.

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So we'll pull it out and
take it back to the museum/

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I'm gonna just
lift it right off.

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There it is.

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Oh, that's beautiful.

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Look at that.

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So we'll get a jacket
on here in a second,

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but we've got the backbone of
a hadrosaur, it looks like,

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That's incredible.

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And these are the beasts
that did not survive

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the end of the Cretaceous.

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NARRATOR: Johnson
believes that, amazingly,

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the date of the dinosaurs' death
is written on the landscape.

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Fossil hunters had noticed
that, at a certain level

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on the hillside,
the fossils ran out.

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When they looked closer, they
found a strange, narrow line.

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They realized this marked
the division between the age

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of the living dinosaurs, the
Cretaceous, and the first era

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after their death, the Tertiary.

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Even closer analysis revealed
that this line containing

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iridium, a substance
normally never found

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on the surface of the Earth.

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Right here is the boundary
between the Cretaceous Period

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and the Tertiary Period.

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That is to say that the
rocks that were deposited

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as sediments above this
layer were deposited

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after 65 million years ago.

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The rocks that are deposited
as sediment before this layer

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was deposited before
65 million years ago.

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So if I wanna find
dinosaur fossils,

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I go down the hill from where
I am now into lower layers,

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into the older rocks.

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If I wanna look at fossils that
were formed from animals that

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were alive after the
extinction of the dinosaurs,

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I go up the hill.

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So it's a matter of walking
up the hill and down the hill,

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up through time and
back through time.

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The iridium layer was first
discovered in 1979 or 80

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by Walter and Louie
Alvarez in Italy.

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And they did further study, and
found the layer again in New

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Zealand, and also in Denmark.

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Since that time,
the iridium layer

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has been found in more than
150 sites around the world.

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NARRATOR: The
scientists were baffled

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to find so much iridium in such
a thin line all over the world.

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Some believe they knew
where it came from.

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It had to have been
brought from outer space.

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The source must've been
a gigantic meteorite

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colliding with the Earth.

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In the scenario of
the asteroid impact,

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we suspect something like this.

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Within hours, the rebound
of the asteroid impact

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has spread a cloud of dust
up into the upper atmosphere,

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blocking the sunlight
from striking the Earth.

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Over a period of months,
the plants will cease

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getting sunlight, and will die.

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And the that animals
rely on the plants,

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such as the large
herbivorous dinosaurs,

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will have no
reliable food source.

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So the large animals die.

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The animals that are supported
by these herbivorous dinosaurs,

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like large, carnivorous
tyrannosaur rex,

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similarly will succumb
to a lack of food,

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or either to direct
environmental effects

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of the asteroid impact.

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The fact that we see huge
levels of extinction of plants

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at this level, as represented
by the disappearance of plant

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pollen and the disappearance
of many species of plant

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leaves, and the fact that
dinosaur bones are only found

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below the level suggests
to me very strongly

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that the asteroid impact and
its resulting fallout ash layer

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were the direct cause for the
extinction of the dinosaurs.

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NARRATOR: The Meteorite Theory
was first advanced in 1980,

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but unknown to the
scientists, the evidence

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to support it had been
found years before.

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A geologist was
prospecting for oil and gas

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off the Yucatan
Peninsula of Mexico.

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Using a magnetometer
slung under a helicopter,

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Dr. Glen Penfield was
carrying out surveys

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of the Earth's magnetic field.

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We were for small excursions or
anomalies, areas in the Earth's

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magnetic field that are out
of the ordinary, that are not

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from the simple, predicted
model of the overall Earth

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magnetic field.

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So we take those measurements,
and we take in every one

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second, say, and record
it on tape and on paper,

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and then we could make
a profile of those.

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We could make a map of them, and
we could see what the Earth's

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magnetic field looked like,
and by interpretation,

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what is underneath the surface.

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This is the Yucatan
Peninsula of Mexico.

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And it was in this area
that I first noticed

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these extraordinary anomalies.

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We were flying east-west lines
about 400 kilometers long,

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first in the offshore, and
then on the onshore portion

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of the platform.

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I started to see, when we
were 100 kilometers or so off

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the coast, a pattern of
very small, irregular,

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high frequency
excursions in the field,

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which looked just like noise.

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They looked just like
the sort of thing

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that we reject data for, a
possible solar disturbance

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or something.

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Suddenly, I began to
see anomalies that

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were much shorter,
very quick reversals

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in the Earth's magnetic field.

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The form of a half a
bullseye begin to emerge.

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NARRATOR: Penfield
compared his findings

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with another map, which measured
the density of the rocks

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below the surface
of the Yucatan.

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It confirmed that
the half bullseye was

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the rim of a gigantic crater,
so deep beneath the Earth

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it had lain undiscovered
for millions of years.

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When I put the
two maps together

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there was just one
of those aha moments.

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I suddenly saw this, and saw a
feature 230 kilometers across

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with a high degree of symmetry,
and unlike anything I'd

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ever seen in my either
academic training

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or my professional work.

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And I suddenly knew.

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I looked at that, and I knew
that this was the signature

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of a meteor crater.

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NARRATOR: Now, scientists like
Luis Marin from the National

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University of Mexico
are trying to discover

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just how big the crater was.

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At Chicxulub in the
Yucatan Peninsula,

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Marin is using
deep drilling rigs

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to bring rock cores
from below the Earth's

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surface, where he thinks
evidence of the crater may lie.

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The question of the size
is very important in terms

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of the energy released.

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If the crater is on the
order of 300 kilometers,

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we probably can tie
this into the extinction

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of the dinosaurs.

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The energy released at
the moment of impact

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is greater than the nuclear
arsenal we have worldwide.

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It would be as if a
billion nuclear bombs

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like the one in Hiroshima
were exploded instantaneously.

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We'd have a huge fireball
that would have come out,

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and then slowly things
would have cooled down.

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NARRATOR: Marrin
bases this estimate

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on the explosive energy needed
to make a crater so vast.

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And his core sample showed
that when the meteorite struck,

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it crashed through the
sea into limestone.

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The geology of
Yucatan is unique.

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There was no worse
place that could have

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been hit by this meteorite.

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And it's perhaps the worst
environmental catastrophe

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the planet has experienced.

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Some of the possible effects
due to the vaporization

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of this rock include acid rain.

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It includes sending
enormous dust

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clouds into the atmosphere.

220
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We're looking for
the impact debris,

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in other words, the material
that resulted after the impact.

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This is a sample that we have.

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And this is what's
left of the meteorite.

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It was in a sample such as this
that we found the evidence that

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convinced the scientific
community that Chicxulub

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was an impact structure.

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00:12:00,140 --> 00:12:04,300


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What we have here is after
the meteorite or comet hit

230
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the Earth, it produced
molten rock due to the speed

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00:12:10,350 --> 00:12:12,530
at which it hit the Earth.

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And then very quickly--
remember, we're

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in water-- it turned into rock.

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This produces glasses
and impact rock,

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which is what we see here.

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The other pieces we see here are
pieces of the basement, pieces

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of the material way
below that, were ripped

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00:12:28,630 --> 00:12:30,710
apart due to the collision.

239
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And this is what we want.

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00:12:35,210 --> 00:12:38,060
NARRATOR: Once Marrin finds out
how deeply the rocks blasted

242
00:12:38,060 --> 00:12:41,030
by the meteorite lie,
he can reconstruct

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the exact shape of the crater.

244
00:12:42,755 --> 00:12:46,350


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00:12:46,350 --> 00:12:49,080
And his discoveries
so far have convinced

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00:12:49,080 --> 00:12:51,410
him that the
Chicxulub impact could

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have wiped out the dinosaurs.

248
00:12:52,915 --> 00:12:56,260


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00:12:56,260 --> 00:12:59,580
We have, on the one hand, a one
in a billion chance of having

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00:12:59,580 --> 00:13:00,860
an impact hitting the Earth.

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And at the same time, we have
just whole species being wiped

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00:13:04,490 --> 00:13:05,900
out, including the dinosaurs.

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00:13:05,900 --> 00:13:10,010
In my mind, there's no question
that Chicxulub was the cause

254
00:13:10,010 --> 00:13:11,140
of the demise of the dinosaurs.

255
00:13:11,140 --> 00:13:18,487


256
00:13:18,487 --> 00:13:19,620
NARRATOR: But some
paleontologists

257
00:13:19,620 --> 00:13:23,840
don't agree that dinosaurs
were wiped out suddenly.

258
00:13:23,840 --> 00:13:27,850
They claim that they died
out over a long period.

259
00:13:27,850 --> 00:13:31,410
This man, Peter Sheehan of
the Public Museum in Milwaukee

260
00:13:31,410 --> 00:13:33,980
is putting that
theory to the test.

261
00:13:33,980 --> 00:13:35,930
He organized a
team of excavators

262
00:13:35,930 --> 00:13:38,610
to comb the outcrops
in the badlands.

263
00:13:38,610 --> 00:13:41,650
The dinosaur bones they found
there would either confirm

264
00:13:41,650 --> 00:13:44,100
the theory of a
gradual extinction,

265
00:13:44,100 --> 00:13:46,930
or would point to
a sudden death.

266
00:13:46,930 --> 00:13:48,660
What we were trying
to do is set up

267
00:13:48,660 --> 00:13:52,130
an ecological study modeled
after modern environments.

268
00:13:52,130 --> 00:13:55,140
And when modern environments
are under stress,

269
00:13:55,140 --> 00:13:57,760
we find that the
communities change slowly,

270
00:13:57,760 --> 00:14:00,980
and the relative proportions of
animals in those communities,

271
00:14:00,980 --> 00:14:03,260
some animals become more
common, other animals

272
00:14:03,260 --> 00:14:06,200
become less common when
there's a stressed environment.

273
00:14:06,200 --> 00:14:08,870
So if the animals in
the Hell Creek formation

274
00:14:08,870 --> 00:14:10,730
were dying out
gradually, we would

275
00:14:10,730 --> 00:14:13,300
expect to find changes in
the relative proportions of

276
00:14:13,300 --> 00:14:15,530
dinosaurs in those communities.

277
00:14:15,530 --> 00:14:17,760
NARRATOR: At Hell Creek,
Sheehan's team dug at three

278
00:14:17,760 --> 00:14:19,570
different levels in the rock.

279
00:14:19,570 --> 00:14:22,680
This covered a time span
of two million years.

280
00:14:22,680 --> 00:14:25,200
If the dinosaurs had
been dying of gradually,

281
00:14:25,200 --> 00:14:27,350
the bones would
have shown changes.

282
00:14:27,350 --> 00:14:29,470
There are about eight
families of different kinds

283
00:14:29,470 --> 00:14:31,720
of dinosaurs that have been
found in the Hell Creek.

284
00:14:31,720 --> 00:14:34,150
The most common
family is the group

285
00:14:34,150 --> 00:14:37,770
of ceratopsians, including
triceratops and torosaur.

286
00:14:37,770 --> 00:14:40,110
These are animals with
large shields and frills

287
00:14:40,110 --> 00:14:41,330
on the back of their head.

288
00:14:41,330 --> 00:14:43,710
They were herbivores,
plant eaters.

289
00:14:43,710 --> 00:14:47,760
They had a large horn on
the front of their skull.

290
00:14:47,760 --> 00:14:50,281
These were the most common
dinosaurs in the lower, middle,

291
00:14:50,281 --> 00:14:50,980
and upper.

292
00:14:50,980 --> 00:14:52,850
They were always
the most common.

293
00:14:52,850 --> 00:14:55,310
More than half of the
all fossils we found

294
00:14:55,310 --> 00:14:56,910
belong to the ceratopsians.

295
00:14:56,910 --> 00:14:59,530
And the next most common
group were the hadrosaurs.

296
00:14:59,530 --> 00:15:01,710
Hadrosaurs are duck
billed dinosaurs.

297
00:15:01,710 --> 00:15:03,280
They're also plant eaters.

298
00:15:03,280 --> 00:15:07,220
The most abundant meat eater was
tyrannosaurus, the largest meat

299
00:15:07,220 --> 00:15:08,020
eater of all time.

300
00:15:08,020 --> 00:15:10,890
This is the vertebra
of a tyrannosaurid.

301
00:15:10,890 --> 00:15:14,250
A smaller meat eater
were the dromaeosaurs.

302
00:15:14,250 --> 00:15:18,450
Dromaeosaurs are clawed
animals, still carnivores,

303
00:15:18,450 --> 00:15:23,750
but they have nice claws related
to their meat eating abilities.

304
00:15:23,750 --> 00:15:28,580
And they were always a
lesser animal in importance.

305
00:15:28,580 --> 00:15:30,720
NARRATOR: When his fossil
hunters had finished,

306
00:15:30,720 --> 00:15:34,510
Sheehan found no signs of
a community under stress.

307
00:15:34,510 --> 00:15:36,320
Throughout those
two million years,

308
00:15:36,320 --> 00:15:40,180
the dinosaur
population was stable.

309
00:15:40,180 --> 00:15:43,100
There was no evidence that
doom had been approaching

310
00:15:43,100 --> 00:15:44,780
over a long period of time.

311
00:15:44,780 --> 00:15:49,470


312
00:15:49,470 --> 00:15:51,840
It seems to have been a
very abrupt extinction,

313
00:15:51,840 --> 00:15:55,070
and it totally wiped out
the largest life form

314
00:15:55,070 --> 00:15:59,140
on the surface of the Earth,
and gave rise to a completely

315
00:15:59,140 --> 00:16:00,000
new set of communities.

316
00:16:00,000 --> 00:16:07,600


317
00:16:07,600 --> 00:16:10,980
I find the giant meteorite
theory convincing,

318
00:16:10,980 --> 00:16:12,740
but then I'm biased,
because it was

319
00:16:12,740 --> 00:16:17,660
first proposed in 1980 by my
good friend Louie Alvarez.

320
00:16:17,660 --> 00:16:20,590
He was a Nobel Prize winner,
and one of the great scientists

321
00:16:20,590 --> 00:16:22,190
of his generation.

322
00:16:22,190 --> 00:16:24,570
Louie and his
geologist son Walter

323
00:16:24,570 --> 00:16:28,220
called this meteorite impact
the greatest catastrophe

324
00:16:28,220 --> 00:16:32,400
in the history of the Earth,
until of course, the next one,

325
00:16:32,400 --> 00:16:34,180
because sooner or
later, something

326
00:16:34,180 --> 00:16:36,830
similar will happen again.

327
00:16:36,830 --> 00:16:39,380
But some scientists have other
theories about the extinction

328
00:16:39,380 --> 00:16:40,870
of the dinosaurs.

329
00:16:40,870 --> 00:16:44,660
They blame disease, volcanic
eruptions, drastic climate

330
00:16:44,660 --> 00:16:48,210
change, the wholesale
destruction of vegetation,

331
00:16:48,210 --> 00:16:50,200
and even constipation.

332
00:16:50,200 --> 00:16:52,110
All these theories
are plausible,

333
00:16:52,110 --> 00:16:55,390
and are fiercely defended.

334
00:16:55,390 --> 00:16:56,590
NARRATOR: The world
of the dinosaurs

335
00:16:56,590 --> 00:16:58,570
was anything but friendly.

336
00:16:58,570 --> 00:17:01,050
Paleontologists are
trying to reconstruct

337
00:17:01,050 --> 00:17:03,630
the creatures' environment
to see if the picture will

338
00:17:03,630 --> 00:17:05,390
yield any clues.

339
00:17:05,390 --> 00:17:09,540
What emerges is a far cry from
the safe world of theme parks.

340
00:17:09,540 --> 00:17:12,869
The dinosaurs' planet shuddered
with volcanic activity,

341
00:17:12,869 --> 00:17:15,890
and baked beneath
relentless sunshine.

342
00:17:15,890 --> 00:17:18,050
Its inhabitants
struggled to reproduce

343
00:17:18,050 --> 00:17:21,589
in large enough numbers
to guarantee survival.

344
00:17:21,589 --> 00:17:23,950
All dinosaurs were
hatched from eggs,

345
00:17:23,950 --> 00:17:25,360
and it's in the
fossilized eggshells

346
00:17:25,360 --> 00:17:28,860
that science now
searches for clues.

347
00:17:28,860 --> 00:17:32,280
In the field, Professor Heinrich
Erben seeks out the places

348
00:17:32,280 --> 00:17:34,200
where the dinosaurs nested.

349
00:17:34,200 --> 00:17:36,430
There, he finds the
fossilized shells which

350
00:17:36,430 --> 00:17:38,850
form the basis of his research.

351
00:17:38,850 --> 00:17:40,320
Professor Erben
has been studying

352
00:17:40,320 --> 00:17:42,060
the thickness of the shells.

353
00:17:42,060 --> 00:17:46,280
He believes they became so thin
that not enough dinosaurs could

354
00:17:46,280 --> 00:17:46,980
hatch out.

355
00:17:46,980 --> 00:17:49,270
[SPEAKING GERMAN]

356
00:17:49,270 --> 00:17:51,200
What caused the
thinning of the egg

357
00:17:51,200 --> 00:17:54,470
shells is of course
a crucial question.

358
00:17:54,470 --> 00:18:00,450
We know that the same happens
today also in the living birds

359
00:18:00,450 --> 00:18:03,560
and in the eggs
of living reptiles

360
00:18:03,560 --> 00:18:05,590
under certain conditions.

361
00:18:05,590 --> 00:18:08,470
We know that the thinning
of the egg shells

362
00:18:08,470 --> 00:18:13,430
is due to a deficiency
of a certain enzyme

363
00:18:13,430 --> 00:18:15,910
called carboanhydrase.

364
00:18:15,910 --> 00:18:20,090
This is due usually to stress.

365
00:18:20,090 --> 00:18:24,680
In the case of the
dinosaurs, it appears

366
00:18:24,680 --> 00:18:32,510
that very probably change in
the vegetation is responsible.

367
00:18:32,510 --> 00:18:34,390
NARRATOR: Erben believes
that the thinning came

368
00:18:34,390 --> 00:18:36,890
with an altered climate,
and that changes

369
00:18:36,890 --> 00:18:40,920
in plant life at the time of
the extinction bear him out.

370
00:18:40,920 --> 00:18:42,870
From his collection
of shell fragments,

371
00:18:42,870 --> 00:18:46,040
he's even deduced how
the embryos perished.

372
00:18:46,040 --> 00:18:50,640
They simply dried out
in the heat of the day.

373
00:18:50,640 --> 00:18:55,800
If the egg shell is too
thin, then there is the danger

374
00:18:55,800 --> 00:19:00,410
that there is an
excessive evaporation

375
00:19:00,410 --> 00:19:06,440
of the inner liquid
content of the egg,

376
00:19:06,440 --> 00:19:09,680
and then the embryo
simply dries completely,

377
00:19:09,680 --> 00:19:14,320
and of course perishes.

378
00:19:14,320 --> 00:19:16,470
NARRATOR: Erben's
colleague, Abdul Ashraf,

379
00:19:16,470 --> 00:19:19,520
also looks for clues
in dinosaur egg shells.

380
00:19:19,520 --> 00:19:22,650
But he analyzes their
chemical composition.

381
00:19:22,650 --> 00:19:24,880
His team grinds
them down to powder,

382
00:19:24,880 --> 00:19:28,280
and puts them through
spectrophotometer analysis.

383
00:19:28,280 --> 00:19:31,360
This reveals the chemicals
present in the air at the time

384
00:19:31,360 --> 00:19:33,040
the egg was formed.

385
00:19:33,040 --> 00:19:37,986
Any poisonous elements or toxic
compounds will show up here.

386
00:19:37,986 --> 00:19:43,660
This process, this analysis we
have found many rare elements,

387
00:19:43,660 --> 00:19:50,320
like vanadium, like iridium, and
also other poisons like leads.

388
00:19:50,320 --> 00:19:54,320
We can see these
things in the x-rays.

389
00:19:54,320 --> 00:19:57,230
NARRATOR: The rare elements
revealed by Ashraf's analysis

390
00:19:57,230 --> 00:20:00,100
include poisonous compounds
normally only found

391
00:20:00,100 --> 00:20:03,450
in volcanoes and meteorites.

392
00:20:03,450 --> 00:20:06,490
The toxins come
maybe from volcanoes

393
00:20:06,490 --> 00:20:12,950
or from asteroids in this time.

394
00:20:12,950 --> 00:20:14,020
NARRATOR: His verdict?

395
00:20:14,020 --> 00:20:16,830
Death by poisoning.

396
00:20:16,830 --> 00:20:21,000
The egg shells contain a lethal
cocktail of vanadium, iridium,

397
00:20:21,000 --> 00:20:25,325
and lead, strong enough to kill
off the species over a period.

398
00:20:25,325 --> 00:20:33,290


399
00:20:33,290 --> 00:20:35,340
Whatever wiped out
the dinosaurs did not

400
00:20:35,340 --> 00:20:37,400
affect their nearest relations.

401
00:20:37,400 --> 00:20:40,670
Crocodiles and alligators
were also around at the time,

402
00:20:40,670 --> 00:20:43,350
and scientists want to
discover why they survived

403
00:20:43,350 --> 00:20:45,330
when the dinosaurs died.

404
00:20:45,330 --> 00:20:47,930
For Professor Mark Ferguson
at Manchester University

405
00:20:47,930 --> 00:20:50,470
in England, alligator
eggs incubated

406
00:20:50,470 --> 00:20:54,620
at different temperatures
provided a breakthrough.

407
00:20:54,620 --> 00:20:56,820
I incubate eggs at 30
degrees centigrade,

408
00:20:56,820 --> 00:20:58,580
for example, a bunch
of eggs like this,

409
00:20:58,580 --> 00:21:00,300
they all turn out to be females.

410
00:21:00,300 --> 00:21:02,710
But exactly the same eggs,
even from the same clutch

411
00:21:02,710 --> 00:21:06,880
incubated at 33 degrees
centigrade give you 100% males.

412
00:21:06,880 --> 00:21:11,710
So 30 degrees centigrade,
all females, 33, all males.

413
00:21:11,710 --> 00:21:13,160
NARRATOR: For Ferguson's
research team,

414
00:21:13,160 --> 00:21:15,620
that discovery was
just the beginning.

415
00:21:15,620 --> 00:21:17,990
They also found that the
temperature at which the eggs

416
00:21:17,990 --> 00:21:20,310
were incubated
affected more than just

417
00:21:20,310 --> 00:21:21,755
the sex of the creature inside.

418
00:21:21,755 --> 00:21:25,910


419
00:21:25,910 --> 00:21:28,980
If it's a cool year, then
the animals are smaller.

420
00:21:28,980 --> 00:21:30,250
They don't eat as much food.

421
00:21:30,250 --> 00:21:31,350
They're well adapted.

422
00:21:31,350 --> 00:21:33,600
If it's nice, warm
weather, they grow larger.

423
00:21:33,600 --> 00:21:34,970
There's a plentiful food supply.

424
00:21:34,970 --> 00:21:37,450
So they can adapt their
metabolic rate and their body

425
00:21:37,450 --> 00:21:40,110
size to a changing
environment very quickly

426
00:21:40,110 --> 00:21:41,250
in the same generation, in fact.

427
00:21:41,250 --> 00:21:44,020


428
00:21:44,020 --> 00:21:46,780
NARRATOR: Ferguson concluded
that, unlike crocodiles,

429
00:21:46,780 --> 00:21:49,950
dinosaurs could not
adapt quickly to change.

430
00:21:49,950 --> 00:21:52,540
Because of their more
advanced genetic makeup,

431
00:21:52,540 --> 00:21:56,420
they had to rely
on slow evolution.

432
00:21:56,420 --> 00:21:58,390
Now, you can't
change your growth

433
00:21:58,390 --> 00:22:01,570
by going in a sauna for six
months, and come out longer,

434
00:22:01,570 --> 00:22:03,290
but an alligator can.

435
00:22:03,290 --> 00:22:06,320
So what happens is that
dinosaurs, because they had

436
00:22:06,320 --> 00:22:08,180
these chromosomal-based
mechanisms,

437
00:22:08,180 --> 00:22:11,160
couldn't adapt quickly to
the changing environment.

438
00:22:11,160 --> 00:22:12,260
It gets cooler.

439
00:22:12,260 --> 00:22:14,350
What happens in
alligators and crocodiles?

440
00:22:14,350 --> 00:22:16,000
They scale done
their metabolic rate.

441
00:22:16,000 --> 00:22:18,150
They scale done their
maximum body size.

442
00:22:18,150 --> 00:22:20,490
They can adapt in
a few generations.

443
00:22:20,490 --> 00:22:24,140
Dinosaurs, much more highly
evolved, much more like us.

444
00:22:24,140 --> 00:22:26,990
They have to mutate the
genes, have natural selection.

445
00:22:26,990 --> 00:22:29,590
Takes thousands and
millions of years.

446
00:22:29,590 --> 00:22:31,715
So they adapted too slowly,
and they went extinct.

447
00:22:31,715 --> 00:22:34,410


448
00:22:34,410 --> 00:22:36,440
NARRATOR: Another
survivor, the tortoise,

449
00:22:36,440 --> 00:22:38,870
provided researchers
with a theory.

450
00:22:38,870 --> 00:22:41,540
Doctor LR Croft had been
working on human eyes

451
00:22:41,540 --> 00:22:44,090
to understand
cataract blindness.

452
00:22:44,090 --> 00:22:47,450
He analyzed proteins from the
eyes of different creatures.

453
00:22:47,450 --> 00:22:51,000
It was then that clues to
a 65 million year mystery

454
00:22:51,000 --> 00:22:52,595
stared him in the face.

455
00:22:52,595 --> 00:22:57,170
We isolated the proteins from
both reptiles and from mammals.

456
00:22:57,170 --> 00:23:01,540
And after purifying them, and
putting them into test tubes,

457
00:23:01,540 --> 00:23:04,610
we exposed them
both to heat, and we

458
00:23:04,610 --> 00:23:05,670
exposed them to sunlight.

459
00:23:05,670 --> 00:23:08,740
And in fact, we used the roof
of the University of Salford

460
00:23:08,740 --> 00:23:12,810
and we left it on the
roof for two weeks.

461
00:23:12,810 --> 00:23:14,940
NARRATOR: Two weeks
exposure to the sun

462
00:23:14,940 --> 00:23:17,880
brought about a dramatic
change, and suggested

463
00:23:17,880 --> 00:23:20,450
a whole new scenario for
the dinosaurs' extinction.

464
00:23:20,450 --> 00:23:24,830


465
00:23:24,830 --> 00:23:28,190
Well, we've had two weeks
of sunshine here in Salford,

466
00:23:28,190 --> 00:23:31,970
and you can see now that the
protein from the reptile lenses

467
00:23:31,970 --> 00:23:33,550
has gone cloudy.

468
00:23:33,550 --> 00:23:36,920
The protein from the
mammalian lens is clear.

469
00:23:36,920 --> 00:23:40,140
Now, this would indicate
that reptiles in sunlight

470
00:23:40,140 --> 00:23:42,390
are susceptible to cataract.

471
00:23:42,390 --> 00:23:45,900
Now, if there was an
increase in solar radiation,

472
00:23:45,900 --> 00:23:49,520
the dinosaurs, having this
protein, like the reptiles,

473
00:23:49,520 --> 00:23:53,820
would have become extinct
because of cataract blindness.

474
00:23:53,820 --> 00:23:57,860
You can see here that he
can retract into his shell

475
00:23:57,860 --> 00:23:59,780
and get protection
from the sunlight.

476
00:23:59,780 --> 00:24:03,390
Now, if you looked at
those reptiles that survive

477
00:24:03,390 --> 00:24:07,770
the great extinction,
the lizards, the snakes,

478
00:24:07,770 --> 00:24:10,170
the tortoises, and
the turtles, they

479
00:24:10,170 --> 00:24:13,120
can all escape them sunlight.

480
00:24:13,120 --> 00:24:15,970
Dinosaurs, of course
being large, couldn't.

481
00:24:15,970 --> 00:24:18,920
And having this
unstable protein,

482
00:24:18,920 --> 00:24:22,510
they would have been much more
likely to have had cataract.

483
00:24:22,510 --> 00:24:28,770
So the theory is that the
dinosaurs became blind due

484
00:24:28,770 --> 00:24:31,560
to cataract at an
earlier and earlier stage

485
00:24:31,560 --> 00:24:33,750
as the temperatures increased.

486
00:24:33,750 --> 00:24:36,510
NARRATOR: Croft says blindness
would've meant disaster,

487
00:24:36,510 --> 00:24:38,890
unable to escape
easily from predators

488
00:24:38,890 --> 00:24:41,540
or to find food and a
mate, the whole species

489
00:24:41,540 --> 00:24:43,330
would eventually die out.

490
00:24:43,330 --> 00:24:45,090
The dinosaurs would
have been doomed.

491
00:24:45,090 --> 00:24:54,140


492
00:24:54,140 --> 00:24:57,420
The solution to this
fascinating detective story

493
00:24:57,420 --> 00:25:00,170
may turn out to be
quite complicated.

494
00:25:00,170 --> 00:25:04,550
It may indeed be a combination
of several theories.

495
00:25:04,550 --> 00:25:08,640
In any event, the dinosaurs
didn't die out completely.

496
00:25:08,640 --> 00:25:10,780
The smart ones became birds.

497
00:25:10,780 --> 00:25:32,080


498
00:25:32,080 --> 00:25:34,830
[THEME MUSIC]

499
00:25:34,830 --> 00:26:00,167