Dinosaurs written in rocks | Diego Pol | TEDxRiodelaPlata

How can we rebuild the history of our planet? Which questions can we answer looking at the traces left by the past? Diego Pol, one of the most prestigious paleontologists in the world, invites us to walk together the fascinating road of discovery, with some very big and some very small dinosaurs.

This talk was given at a TEDx event using the TED conference format but independently organized by a local community. Learn more at: http://ted.com/tedx

My first encounter with a fossil
was when I was 12,

during a trip to Santa Cruz
I made with my family,

in the Argentinean Patagonia.

I had been in museums several times

with rooms full of dinosaurs
that fascinated me.

But this was the first time
I saw fossil on the field,

in the middle of nowhere.

An animal that lived
millions of years ago

and that probably
no one had seen before.

The animal I found was similar to this one
and we usually call them sand dollars.

They are related to sea urchins,

and were very common in the sea
that invaded Patagonia

about 15 million years ago.

At that moment, I didn't know this,
I didn't know what it was

and I tried to pull it out immediately.

And I discovered something
I didn't know about fossils:

They are extremely fragile.

The sand dollar broke, fell to the sand,

and my paleontologist career
was starting with left foot.

But my interest for fossils,
my fascination for those ancient beings

and imagining how our planet
was in the past,

kept captivating me.

And lead me to study dinosaurs

and animals that lived
millions of years ago

in the remote past of our planet.

About 100 million years ago,

our planet was very different.

It was so different that
not only humans didn't exist,

but also the whole planet was dominated
by dinosaurs and other reptiles.

And this was 100 million years ago,

which is something that we,
paleontologists, mention daily,

but that it's very hard to conceptualize.

If you look around, you will see
10,000 people in this stadium,

which is a lot of people.

Now imagine that each of you

represents an stadium like
this one, with 10,000 people.

10,000 times 10,000, that's 100 million,

that's a quantity that
doesn't fit in our heads.

And that, multiplied by a year,

think about everything that
happened in the last year,

it's an amount of time
that it's very hard to imagine.

Well, life has lead me to study

how was the world
100 million years ago.

I've walked through deserts,

and I've studied fossils
from all over the world

trying to inquire how was
the past of our planet

in different regions.

Places such as Mongolia,
Southern China, South Africa,

studying fantastic fossils.

But it also lead me
to a very special place

which is Patagonia.

And when we say Patagonia

we naturally think about
one of those landscapes

made of forests, lakes,
close to the Andes.

But for us, paleontologists,

Patagonia is this, a wonderful desert

full of fossils to be discovered.

Fortunately, we know
a lot of dinosaurs from there,

it's one of the best places
to look for dinosaurs.

Most of them

are from the last period
of dinosaurs on Earth,

what we call the Cretaceous Period.

This was about 70 million years ago.

We know a lot of fossils from Patagonia

and we know that
in the Southern Hemisphere

the dominant carnivores

belonged to a family
called Abelisaurs.

While at the same time,
in the Northern Hemisphere,

there were other families of carnivores

such as the Tyrannosaurs,

in which we can find
the famous Tyrannosaurs Rex.

And the difference between North
and South wasn't surprising,

because at that time,
a big ocean divided and isolated

the two hemispheres.

But what happened before
this well-known period?

During what we call the Jurassic Period,
about 100 million years ago.

At that time, all continents
were together,

forming a big continent named Pangea.

And we know very little about
what happened then

in the Southern Hemisphere.

And it is a key moment to understand

the evolution of dinosaurs in our planet.

It is a key moment, specially
170 million years ago,

when dinosaurs dominated our planet
completely for the first time.

For the first time, they
reached gigantic sizes,

for the first time they differ
each other, and conquered groups

of herbivores, carnivores
and omnivores worldwide.

We have been working on this
for the last 10 years

with a group of colleagues,
students and interns,

to explore the Jurassic
rocks of Patagonia.

And this takes me
to one of the stories

of the discoveries we did
in the last few years.

We found it four years ago
in hills like these, walking.

A very hot afternoon,

after walking all day, just before
returning to the camp,

I was walking and I saw some meters
away something that called my attention

among the rocks, on the floor.

And I came closer,

and as I came closer
it became clearer what it was;

a dinosaur skull.

I came closer, I stood next to it,
I kneeled down, I literally froze.

I wondered what it was,
at the same time I knew it.

After years of studying dinosaur's bones

I knew exactly that it was the backside
of a carnivorous dinosaur.

But I couldn't really believe it.

I knew it was
a once-in-a-lifetime discovery.

After I told the rest of the team

and after celebrating,

we started working

to protect that fossil
in order to extract it.

After some days, we could
cover it with layers of cast,

like we do to take them to the museum,

and we took it downhill.

But the expedition was ending.

We didn't have the necessary
equipment nor the time

to make a big excavation

and we had to go back to the museum
until the next season,

as winter was coming.

It was a long year, waiting,

until we could organize
the next expedition.

We needed to open the excavation
to see if there was something else.

Was it just the skull we already found,

or were there any other remains?

After that long year,

the first day of the expedition

we noticed that the full
skeleton was there.

It was something very unusual
for a dinosaur finding,

a full skeleton, incredibly preserved

in life position.

Clearly the animal died by a lake,

and was covered by thin layers of mud

preserving his skeleton intact.

That's when the excavation
really begins,

to start taking out layer by layer

the sediments that buried this dinosaur.

It's a very exciting moment,

for the first time,
it's coming back to surface

an animal that lived in that exact
same place, 170 million years ago.

This animal must have died,

must have been covered
by layers of sediments

that kept accumulating

until they formed meters
and meters of layers of sediments.

Those sediments became sedimentary rocks

and in the same process

bones became fossils
due to chemical reactions.

Then, those buried rocks
rose up to the surface

due to a fracture of the Earth Crust

and some lifts of the whole block.

Then, rain and wind eroded those layers,

one by one,

until they uncovered the layer
that contained this dinosaur,

at the same time,

that same summer
we were walking on those hills

looking for those dinosaurs.

So when you think of all the things
that must have happened

you notice how unique that moment is

and it's very exciting

to discover the bones of a new species,

completely unknown until that moment.

It's a long work

that takes a lot of hours under the sun,

the merciless Patagonian wind,

and then we could take
all those fossils covered in cast

to the laboratory.

In the museum's lab

another extremely long phase begins,

in which technicians,
with infinite patience

remove grain by grain

all the rocks that cover
the bones of these dinosaurs.

And that's when we can see,
for the first time, the full skeleton

and we could see this dinosaur
which we called Eoabelisaurus.

Studying the anatomy of these fossils

we saw that it was related,

it was an ancestor of the Abelisaurs,
those Southern Hemisphere carnivores.

This discovery showed us

that this family was originated

about 100 million years
earlier than we thought.

Before the two hemispheres separated,
divided by a big ocean.

At the times of Pangea,
when all continents were together.

Not all discoveries
follow the same track.

Some of them are actually done
in the laboratory

and we don't know what we have
until we get there.

For example, from these rocks
we took to the museum

knowing that they have fossils,
but not exactly what is inside them;

after nine months of working in the lab

we discovered fossils of a dinosaur

that were inside those rock blocks.

The skeleton was quite complete

and had a very well preserved skull

and very strange teeth.

Hand-shaped teeth,

and that's why we call
this dinosaur Manidens.

Now, this dinosaur is very particular
for something very special:

It's one of the smallest
dinosaurs in the world.

What I have here is a reproduction
of this dinosaur's skull.

It's a very, very small dinosaur,
one of the smallest in the world.

Its compete skeleton
is no more than 50 cm long

from head to tail.

And this mini dinosaur
didn't look at all

to the ones we found or knew
in the Northern Hemisphere.

By studying its remains we could see

that its closer relatives
had been found in South Africa,

inside rocks of the same age.

And that was not that surprising,
because if you see the map,

South Africa and the Patagonia
were very close to each other

in the times of Pangea.

The Atlantic Ocean
hadn't been formed yet,

which today separates both continents.

But again, we had a case

of animals restricted
to the Southern Hemisphere

that had nothing to do
with the Northern Hemisphere.

We started finding other cases
that matched this pattern

and that lead us to study

with colleagues that were working
on other animals living at that time,

on fossil plants found in that region.

And also with colleagues studying rocks
which are very important

because they inform us about
the environments at that time.

By studying climate models,

what we saw is that
at this time of Pangea

in which all continents were joined

the climate dynamics was very peculiar.

There was a big desert
in the Equatorial area

of the super continent.

And it was clear that all this fauna
that we were finding

was on the South
of the big Equatorial desert.

It was a big desert isolating that fauna,

making it evolve independently

and separately from
the Northern Hemisphere fauna.

The lack of water had isolated them.

It was not a desert full of water.

And when we think about dinosaurs

and we find fascinating things
about their anatomy,

we realize that they are fantastic
and fascinating beings.

They challenged the limits

of body size in life's history;

they diversified and conquered
all the ecosystems

for millions of years.

But the most important thing

is that they lead us to understand
chapters like this one

in the history of our planet.

And we, paleontologists,

dedicate a big part of our life
learning to read those stories.

Stories written in rocks,

formed for million of years
in our planet,

catching every once in a while
animals and plants

that lived in the past.

The Earth is a big book, full of pages,

written throughout 4.5 billion years.

And life plays a key role in this story

during the last 3.8 billion years.

Millions of pages are yet to be read.

And if we really want to know our planet,

its climates, its ecosystems,

the problems we currently experience,

it's crucial to know its history.

Because knowing the past
is a key to understand the present,

and also to project the future.

Thank you.

(Applause)