- [Narrator] Dinosaurs are awesome.

(dinosaur roaring)

We all know it.

When we figured out

these guys were a thing,

we wanted more, more fossils, more art, more, well,

whatever this is.

So we went out and found them.

Fast forward to today,

we're still discovering like never before.

(soft marimba music)

- Paleontology as a science started in the 1800s.

Back then, we understood for the first time

they were a unique and different group of animals.

- [Narrator] Fossil discoveries were happening

long before this distinction, though.

Dinosaur bones were mistaken for mythological creatures

thousands of years before science

could tell us what they really were.

And for generations,

people connected these fossils to living creatures

they already knew.

Until Richard Owen, frenemy of Charles Darwin,

concluded these fossils were different

from any living creature on earth.

- He coined the term dinosaur,

the terrible lizard.

- [Narrator] New type of animal, big step forward.

(dinosaur roaring)

- For the first 100 years,

we knew very, very little about dinosaurs.

We only knew 50 or 100 species or so.

- [Narrator] Discovery started slow,

but the public's curiosity was high.

So a view into this prehistoric world

came from a different perspective, art.

(upbeat jazz music)

Creativity brought dinosaurs to the cultural forefront.

While these drawings, paintings, and sculptures

were initially based on scientific discoveries,

(toilet flushes)

let's just say that didn't last.

Our imaginations might've gotten a headstart,

but technology, it's catching up.

- Paleontology has been undergoing this massive revolution.

- [Narrator] One of those technologies?

CT scanning, giving paleontologists a new look at dinosaurs.

- You can look at the brain size,

you can look at the different parts of the brain,

because basically the bones that demarcate the brain cavity

are very good proxy for what the brain actually looked like.

So there's a ton of new morphological information

that we can get through these high resolution

imaging techniques that are fairly new.

- [Narrator] This in depth view has been a game changer

in the field,

but one classical aspect of paleontology

has also experienced a renaissance.

(shovels scraping)

Finding fossils.

- In the U.S. or Europe,

that's where paleontology first grew as a science,

but other continents,

they have not been explored as much.

There are so many expeditions being conducted right now,

but many, many new dinosaur species

are coming from these places.

- [Narrator] Example, Diego's team in Patagonia

discovering the Patagotitan mayorum,

one of the largest dinosaurs ever found.

Fossil discoveries in China are also answering

an age old question,

dinosaurs' relationship to birds.

- Birds are extremely rare in the fossil record,

and this is for a number of reasons.

One is that birds are all pretty small.

Aerodynamics limits body size, so you can't get that big.

The other thing is that birds have hollow bones.

They get crushed easily,

they get destroyed, and they just don't survive.

So all these fossil birds all come

from ancient lake deposits,

(bell dings)

the perfect environment to preserve

these very delicate fossils.

- [Narrator] Birds evolving from dinosaurs

is not a new idea, but it's the access

to these ancient lake deposits

(bell dings)

that's finally providing the necessary evidence.

- The notion that birds are living dinosaurs

actually dates back to like the second half

of the 19th century.

A guy named Thomas Huxley, based on his observations,

he came up with a hypothesis

that birds descended from small bipedal dinosaurs.

But other scientists opposed this idea

because they said, well, you know,

all birds have a wishbone, right?

This is not known in any dinosaurs.

So birds can't be living dinosaurs.

- [Narrator] Next up, John Ostrom,

who analyzed theropod dinosaurs,

and also hypothesized that birds were living dinosaurs.

- But again, people kind of rejected this hypothesis.

At the time, their new reason was

velociraptors that were supposed to be closely related

to birds were much younger in the fossil record

than Archaeopteryx, the oldest bird.

So they were like,

how could Archaeopteryx have descended from taxa

that don't appear in the fossil record

until like 70 million years later, right?

(engine racing)

- [Narrator] Inconclusive evidence persisted,

until, well, that's what brings us back

to these ancient lake deposits.

- So in 1996, you find

the first feathered dinosaur in China.

So then an enormous amount of field work started to happen,

and this produced these thousands of specimens.

(upbeat music)

- [Narrator] Paleontologists then discovered an area

where fossils predate Archaeopteryx.

And within this area,

they found small feathered dinosaurs with bird-like traits,

including wings here and here,

making his theory much stronger, also.

- There was a little troodontid dinosaur named Mei long

that was discovered, and it's really tiny.

It's like this big,

and it's preserved with its head underneath its wing,

sleeping the same way modern ducks do.

So that's behavioral evidence

that birds are in fact living dinosaurs.

- [Narrator] Today, substantial evidence points

to birds evolving from dinosaurs, specifically theropods,

and showcases the progression of paleontology.

But the discoveries don't stop here.

- There are still new things out there

that once they are discovered

are gonna shake up everything we think we know.

New data will cause us to adjust our existing hypotheses,

so you just kind of have to go with the flow of discoveries.