♪ ♪
NARRATOR: Birds live
across our entire planet.
Around 50 billion of them
fill our skies, seas,
and landscapes.
Each of the 11,000
species expertly adapted
for the environments
they inhabit.
But how did they come to be
such an evolutionary triumph?
The answer lies
with their ancestors.
Today's birds are dinosaurs.
They are every bit
as much of a dinosaur
as a T. rex is or
a Brontosaurus is.
NARRATOR: But exactly how
this spectacular evolution took place,
is still somewhat a mystery.
Right now, we
have very little data.
I mean, that's how it
is with paleontology.
You have
hundreds of millions of years
and just a few fossils
scattered around the world.
NARRATOR: Now, a
new breed of scientist
is making spectacular
discoveries...
We scanned it. And
then what we found
was... Whoa.
a lot of skeleton
underneath the rock.
Holy cow!
NARRATOR: to fill in the
gaps of this evolutionary tale...
We thought it's just
going to be a simple thing.
They're like dinosaurs
or they're like birds.
And what we found is
that, they are like neither.
NARRATOR: and
answer one of paleontology's
biggest questions:
why were birds
the only dinosaurs
to survive the asteroid impact
FIELD: The development
of new technologies
has provided us
with a richer picture
of avian evolution than has
ever previously been possible.
NARRATOR: "Dino Birds"...
right now, on "NOVA."
♪ ♪
♪ ♪
NARRATOR: Birds
are full of surprises.
They lay eggs like reptiles,
but have warm
blood like mammals.
Only birds have feathers
and it's one of their most
distinctive characteristics.
NARRATOR: There are
dazzling in their variety...
size, shape and behavior.
We think we know them well,
but beneath those
colorful feathers
lurks an enduring mystery.
Why are birds here?
Scientists have discovered
that they are the sole surviving
branch of the dinosaurs.
When an asteroid wiped
out nearly all animal life
birds somehow survived
while all other
dinosaurs disappeared.
Why? Was it pure chance?
Or did they possess some special
advantage that set them apart?
♪ ♪
Now, new discoveries
in paleontology and
evolutionary biology
might finally be
providing answers.
♪ ♪
FIELD: I think
this is going to be
a great place to see some birds
GUILLERMO
FERNANDEZ: Oh, I agree.
NARRATOR:
Historically, it's fossils
that have revealed
the past to us.
But in the case of birds,
the record is patchy.
Their fossil remains
are notoriously
rare and fragile.
flapping) Hey, over there?
A Eurasian griffon vulture.
FIELD: So you've
got... two griffin vultures,
on top and then one below.
Oh, I can see it. Yeah.
FIELD: I think they're
warming up before they take off.
Do you see it
stretching its wings?
FERNANDEZ: I think so, yeah!
I think that vulture
is about ready to go.
Oh, one just took off!
FERNANDEZ: Oh wow, yeah.
One just took off! Yeah!
FERNANDEZ: He's
flying. FIELD: Oh, Wow!
FERNANDEZ: Beautiful.
FIELD: That is a huge
bird! FERNANDEZ: Beautiful.
FIELD: Oh my goodness!
♪ ♪
This is such an amazing place
to come bird watching.
But these birds are never
going to turn
into fossils, right?
It's not the sort of environment
that is conducive
to fossil formation.
♪ ♪
The bird fossil record
is particularly sparse,
and that's because birds are,
by their very nature,
fragile animals.
♪ ♪
And the very lightweight
nature of bird skeletons,
which tend to be filled with air
to make them even lighter
as a specialization for flight,
and those are features
that tend to conspire against
their preservational potential
in the fossil record.
NARRATOR: This left
the story of bird evolution
virtually unwritten for decades.
Barely a clue to tell us
where today's four main
groups of birds all came from.
But every now and
then fossils do appear,
and when that happens,
a new chapter of
the story is unlocked.
♪ ♪
One of the greatest
of these fossil finds
lies in the heart of London,
in the treasure room
of the Natural History Museum.
FIELD (voiceover):
This is Archaeopteryx,
one of the most amazing
fossils in the world.
NARRATOR: Found just
two years after Charles Darwin
published his ideas
of natural selection,
Archaeopteryx was one of
the many great 19th
century dinosaur discoveries.
Dinosaurs took over the Earth
some 220 million years ago,
evolving from
reptilian relatives.
They inherited from
reptiles the defining features
we associate with
dinosaurs today...
big claws, sharp teeth...
but with one major difference.
Dinosaurs, whether they
walk on four legs or two,
have an upright stance...
their legs below their bodies.
In reptiles however,
the legs extend
horizontally from their bodies.
Over the 140 million years
that dinosaurs ruled the Earth,
countless species came and went.
The approximately
dino bird, Archaeopteryx,
has turned out to be
one of the most important
in the story of bird evolution.
With the discovery
of Archaeopteryx
and some of the first dinosaurs,
even then, the
earliest paleontologist
looked at these
things and are like
birds are dinosaurs.
I mean, the skeletal
similarity is enormous.
Archaeopteryx provides
us with an amazing glimpse
at a combination of features
that we expect to
see in living birds
in the present day... like
large feathered wings...
as well as the kinds of features
that we associate
with dinosaurs:
like a long, bony tail,
jaws full of sharp, pointy teeth
and strong claws.
NARRATOR: It bore
an uncanny resemblance
to a known dinosaur fossil.
♪ ♪
Hello, Dan!
Good morning Olivia!
Good to see you!
Should we go look at
some fossils? Yeah, sure!
Great, let's take a look!
♪ ♪
This is the skeleton
of Compsognathus,
which was a really
important theropod dinosaur
into the 19th century,
because it helped convince
Thomas Henry Huxley
that there might be
an evolutionary link
between birds,
like Archaeopteryx,
and theropod dinosaurs.
♪ ♪
NARRATOR: Compsognathus
and Archaeopteryx
have some
surprising similarities.
They would both have
walked on two legs,
had long arms, long bony tails,
and teeth.
♪ ♪
Features that convinced Huxley
that birds were likely
descended from dinosaurs,
a controversial theory
in the 19th century.
This idea was
rejected for 100 years,
uh, primarily because
dinosaurs did not preserve;
or no known dinosaur at the time
had a fossilized furcula...
that's the wishbone.
But then, you know, in the '70s
the first dinosaur
wishbone was found.
♪ ♪
NARRATOR: The discovery
of dinosaurs with wishbones...
a feature previously
only found in birds...
sealed the deal.
And we now recognize
without a doubt
that Compsognathus,
Archaeopteryx,
and modern bird
all belong to theropod dinosaur,
the group of three-toed,
meat-eating
dinosaurs like T. rex.
NARRATOR: Despite
this evolutionary link,
there are still mysteries.
Creatures with early feathers
that don't look
like modern birds,
and archaic birds...
ancient species,
whose evolutionary
lines are now extinct...
that have bird-like
beaks, but filled with teeth.
But when was the moment
one evolved into the other
when modern
birds first appeared?
How did dinosaurs take flight?
And why did some birds survive
when all other
dinosaurs died out?
♪ ♪
Today, new discoveries are
revealing important new clues.
FIELD: It's an amazing time
to be studying bird evolution.
NARRATOR: On the border
of the Netherlands and Belgium,
quarry excavations
have revealed the world
as it was 67 million years ago,
not long before an
asteroid k*lled off
Welcome to the very last
days of the dinosaur era.
This is it.
JAGT: So what we see here
was basically what was deposited
in a shallow sea, quite warm,
during the last days
of the era of dinosaurs.
We can really compare this
with the Caribbean
or the Indonesian
Archipelago these days.
FIELD: Sounds good. JAGT: Yeah.
FIELD: It's a good
place for vacation.
NARRATOR: These shallow
seas provide the perfect conditions
for fossilization to occur;
a wet environment where sand
and mud cover remains quickly.
Waters filled with
hungry mosasaurs
whose fossils
would come to light,
millions of years later.
FIELD: So this begins
somewhere in the range
of about 67 million years?
JAGT: 67 and a half,
something like that,
and then going up.
NARRATOR: These
layers of rock protected
one of the most incredible
bird fossils ever found;
a chance discovery made
by an amateur fossil hunter
in the year 2000.
This is the level that produced
both bird fossils. Right.
I think it's time to
unwrap the birds.
All right. And here it is.
This is the only known specimen
of Asteriornis maastrichtensis.
I still remember
what my first impression
of this fossil was like,
when I looked at it, uh...
a very positive impression.
NARRATOR: It wasn't until
that Daniel Field began
studying the specimen.
FIELD: This fossil
clearly preserves
a few bird bones.
And those bird bones
are not well preserved.
You can see there's a
broken thigh bone on top
and there's a broken
shinbone underneath.
But these are clearly
the bones of birds.
And so even though
the fossil didn't look
very... beautiful at first,
we thought maybe it
would tell us something
about what birds were like
just before the
asteroid wiped out
the giant bird cousins,
the large dinosaurs.
NARRATOR: Using a CT scanner,
Daniel and his team were
able to digitally remove
the rock, and reveal
what secrets it held within.
What he saw exceeded
his wildest dreams.
♪ ♪
FIELD: When we removed
the low-density rock and saw
this skull staring back at us,
my PhD student Juan and I
could not believe our eyes.
It was a shock. It
was really exciting.
And we realized immediately
that this fossil was going to be
very important because
it could provide us
with information that no other
fossil ever discovered could.
It was very exciting and,
and one of the most exciting
moments of my scientific career.
NARRATOR: This specimen
provides a portrait of a bird
that lived 66.7
million years ago.
This fossil is extraordinary
because it shows
several features that tell us
that it is a member of
the modern bird group.
And the most obvious of
those features is the fact
that it does not have any teeth.
NARRATOR: The remains
of ancient archaic birds
have beaks filled with teeth.
Losing them was a key
stage in the evolution
of dinosaurs into modern birds.
And the fact that this fossil
has a beak very similar,
uh, similar to living
generalist birds
suggests that it probably
would have been happy
eating almost
anything it could find.
NARRATOR: Just like birds
with similar beak shapes do today.
FIELD: In addition to that,
if you look at the leg
bones of this fossil,
they're relatively narrow
and relatively long,
and those are features
that we associate
with predominantly living on
the ground in the present day.
NARRATOR: Around seven or eight
inches tall, with the beak of a chicken
and the head of a duck,
this creature is
one of the oldest
modern birds ever
to be unearthed.
Scientists named the 67 million-
year-old species Asteriornis
after Asteria, the Greek
Titan goddess of falling stars.
It confirms that
modern birds existed
alongside the dinosaurs
before their extinction.
This small bird bears
witness to a world
prowled by T. rex
and Triceratops.
Neither the largest
nor the most dominant,
its omnivorous feeding
habits mean that it's satisfied
with small shellfish and seeds.
It might also
scavenge leftovers;
perhaps even a washed-up
Mosasaur carcass.
With its toothless beak
and variety of food options,
Asteriornis is
well-equipped to survive
in the realm of the dinosaurs.
But with such evolved features,
it's unlikely that it was
the first modern bird.
♪ ♪
At Rockefeller
University in New York,
Erich Jarvis and his team
are taking a different
tactic to find the beginning
of today's birds,
using modern DNA to
map their evolutionary past.
JARVIS: The way we dated
the origin of modern birds
is we took the
genome scale tree,
which is the alignment of DNA
from one species to another.
NARRATOR: This
reveals the genetic code
for certain traits
in modern birds
that they can then look
for in ancient fossils.
Then we took fossil data
that's been collected
from all around the world
and placed those fossil dates
on the tree for like 20 species.
NARRATOR: This tree allows
Erich to see exactly where
different species of living
bird genetically diverged.
But what the team
really wants to find out
is when these
divergences took place.
What does DNA suggest about when
modern birds first appeared?
JARVIS: You look at mutations
that occurred over time.
And from those mutations,
you can get what's
called the molecular clock.
How much time do you
need to have one mutations,
two, three, four, five?
NARRATOR: By estimating
this rate of mutation,
Erich wound back the
clock and put a timestamp
on when certain
characteristics changed.
JARVIS: So from the
combination of this molecular clock,
the tree structure,
and the fossil evidence,
all three of those combined,
we can date when modern
birds originally formed.
And that was 90
million years ago.
NARRATOR: Fossils
confirm that modern birds
and their giant dinosaur
cousins co-existed,
and DNA indicates this wasn't
a short-term arrangement.
They lived alongside one
another for some 25 million years,
perhaps even longer.
And new research is
showing just how similar
the lives of ancient birds
would have been to birds today.
LIDA (translated): This
is the most complete
and best-preserved oviraptor
embryo skeleton in history.
NARRATOR: This is the egg of a
type of dinosaur that lived in Asia
were arranged in a circle.
For some reason,
perhaps because floodwater
covered the entire nest
in sand, they died
quietly in this way.
STEVE BRUSATTE: And
it looks like it was fossilized
right before it
would have hatched.
So in looking at this fossil,
we are glimpsing
the last moments
of a dinosaur's
development in the egg
before it would greet the world.
What we're seeing
with this fossil
is that these dinosaurs would
have developed in their eggs
and hatched from their
eggs just like birds do today.
♪ ♪
NARRATOR: It's the remains of
embryonic dinosaurs and their shells
that have helped
scientists answer
one of the great questions
surrounding bird evolution.
Of all animals alive today,
there are only two
groups of animals
that are warm-blooded:
mammals and birds.
NARRATOR: It's a key feature
of what makes flight possible.
You have more energy
available that allows you
to be more active,
which allows you to
move greater distances.
NARRATOR: Dinosaurs were
first assumed to have cold blood.
O'CONNOR: And so
we are very
interested in knowing
when this warm-bloodedness
evolved in birds.
♪ ♪
NARRATOR: Scientists
have been investigating
the question for decades.
And recently, key evidence
came from dinosaur eggshells.
That eggshell formed within
the body of the mother dinosaur.
NARRATOR: Geochemist
Robin Dawson analyzed minerals
in the fossilized shells
to reveal what
temperature they formed at...
in other words, the
mother's body temperature.
DAWSON: We looked at eggshell
from the major
clades of dinosaurs.
Major groups have body
temperatures that are warmer
than their environment,
which suggests to us
that they actually
had the capability
to have a high metabolism,
raise their body temperature
above their environment,
like their
warm-blooded relatives,
like living birds.
O'CONNOR: For sure,
dinosaurs were warm-blooded,
but actually some
dinosaurs, like Stegosaurs
and duck-billed dinosaurs,
actually secondarily
evolved to be cold-blooded,
which I think why we were
having difficulty deciding
if dinosaurs were
warm-blooded or not,
because, you know, there
was a conflicting signal.
NARRATOR: With warm blood, dinosaurs
would have a lot of energy to expend,
raising interesting questions.
Like, would they have
had enough energy
for a high-intensity
activity like flight?
It's the most physically
demanding form
of vertebrate locomotion.
So you have to be warm-blooded.
NARRATOR: But even if their
metabolism supported flight,
what about the equipment,
like wings and feathers?
For 20 years this
was the only snag
in the dinosaur-bird
evolution theory.
Where did feathers come from?
♪ ♪
In Liaoning, China,
the subsoil of the Chaoyang
Bird Fossil National Geopark
reveals a dinosaur
world that existed
between 112 and
♪ ♪
Buried under volcanic ash,
the fossils are
spectacularly preserved.
The most famous are
housed in a vast building.
A long, winding walkway
hangs above the geological layers
and the fossils they contain.
MAN (translated): We've
discovered many microraptors here,
as well as birds
like Confuciusornis.
NARRATOR: But it's not just the
sheer number of fossils found here.
It's what they've
revealed to the world.
that the microraptor found here
has feathers.
NARRATOR: Feathers...
a discovery that
has revolutionized
the world of paleontology.
Because a microraptor
is not a dino-bird,
but still a dinosaur...
a non-avian theropod.
In the '90s, with the discovery
of feathered dinosaurs,
I mean, it was one of the
most compelling arguments
for the "birds are
dinosaurs" hypothesis.
BRUSATTE: The
discoveries kept coming.
And now there are thousands
of feathered dinosaur
fossils that are known.
And it wasn't only small ones.
NARRATOR: More than 100
years after a link was first made,
birds were finally confirmed
as part of the dinosaur lineage.
And scientists
were one step closer
to understanding
the origins of flight.
But if anything,
this discovery raised
as many questions
as it answered.
Why did dinosaurs develop
feathers in the first place?
What advantage did they provide?
♪ ♪
Paleontologist Xu Xing,
from the Institute of
Vertebrates and Paleontology
in Beijing, discovered
the fossil of a dinosaur
with the answer... Yutyrannus.
XU (translated): Its
body is about the size
of the famous T. Rex.
It was almost nine meters long
and weighed almost 1.5 tons.
So we're talking about a giant.
♪ ♪
NARRATOR: Approximately
this is one of the
oldest fossils that shows
non-flying dinosaurs
with feathers.
Yutyrannus's feathers,
You can see their length
on these blocks of sediment.
We can see that Yutyrannus'
body was covered in feathers,
from head to tail.
♪ ♪
NARRATOR: But they don't look
anything like bird feathers we see today.
They appear to
be more like hair.
most likely hypothesis
is that there was a cold spell
at the beginning of
the Cretaceous period.
Yutyrannus is, in a way, the
woolly mammoth of that time,
with long, fine feathers that
meant it could keep warm.
NARRATOR: Acting
almost like down,
it's been nicknamed
by scientists "dinofuzz."
A stark contrast to the
feathers of flying dinosaurs
like Archaeopteryx and
most modern-day birds.
But with a wealth of
feathered dinosaur fossils
found in just a few years,
scientists have pieced together
a timeline of feather evolution.
The earliest
feathered dinosaurs,
like Yutyrannus,
had straight feathers.
In the next generation
of dinosaurs,
these long hairs separated,
producing simple branches.
In many lineages,
this down then evolved
into more complex
feathers with a central spine,
barbs, and then barbules
fitted with small hooks
holding them
together to form a sail,
a more familiar
symmetrical feather.
But only asymmetric feathers
shaped more like
an airplane wing
are capable of creating pressure
differences, and therefore lift,
allowing for flapping
flight over long distances.
We know the changes
that took place,
but the question remains...
why did they happen and when?
Fossils from Liaoning
once again provide clues,
suggesting that the ancient
bird species Confuciusornis
had another use
for its feathers.
Confuciusornis is
a really special bird.
It's represented by more
than a thousand specimens.
And some of them are
exquisitely preserved.
♪ ♪
NARRATOR: With so many
fossils of this kind of bird,
researchers around the world
have come together to work on
this project.
BAILLEUL (translated): We
realized that there were two types
of specimen within
this species... some with
very long tail feathers
and others with very
short tail feathers.
So we asked ourselves, "Why?"
CHINSAMY-TURAN:
So people postulated
that one of the
morphs was a male
and the other one was a female,
but it couldn't really
be very sure about it.
NARRATOR: Paleontologist Anusuya
Chinsamy-Turan looked inside the bone,
taking a
less-than-millimeter-thick slice
to search for answers.
And one of the first
specimens I sectioned
actually happened to be one
that had the most
unusual bone tissue
inside its marrow cavity,
which we call medullary bone.
NARRATOR: That's the
brown area on this slide.
And medullary
bone is so interesting
because you only
find it in female birds.
And they form it at the
time that they're ovulating
and they use that medullary
bone to calcify the egg shells.
So when I found this, I
said, "Oh, my goodness."
I didn't know which
specimen it had come from
because I only had
the little bits of bone.
And so I contacted
my colleague and I said,
"Can you double check
the specimen number
and see whether the specimen
has long tails or no tail?"
And he came back
to me and he said,
"Actually, the specimen
doesn't have any feathers."
So we could say for sure this
was a female Confuciusornis.
NARRATOR: That
meant the long tail feathers
belonged to male Confuciusornis.
Not needed to aid their flight,
the feathers likely
served a different purpose.
In these marshy landscapes
of northeast China
ago, it's mating season.
Confuciusornis females
have a lot of options.
And the males have to redouble
their efforts to attract them.
Competition is fierce
as they use their
spectacular tail feathers
to attract the best mate.
Ornamentation in dinosaurs
potentially led to feathers
that eventually
supported powered flight.
Then the hypothesis
is that you already have
these aerofoils,
these surface areas.
And so even though
their primary function
was ornamentation,
they must have had some
incipient locomotor function.
Even though they can't fly,
they still use their wings for
their terrestrial locomotion.
And then, eventually,
as these wings evolve
to be bigger and
bigger and have greater
and greater aerodynamic benefit,
they eventually reach a
point where they can be used
for powered flight.
NARRATOR: Today, bird
flight is spectacularly complex.
They soar with ease.
But the transition
from a ground-based
life to one in the skies
would not have been an easy one.
It's something that
scientists are still
trying to understand.
Which of the
newly-found feathered,
and sometimes winged,
dinosaurs could fly?
How did they take
that glorious first leap?
Surprisingly, the oldest
missing puzzle piece,
collected over a century
ago, Archaeopteryx,
is still filling in gaps today.
In a synchrotron
particle accelerator
larger than two football fields,
scientists are analyzing
this precious fossil.
VINCENT FERNANDEZ (translated): The synchrotron
beam comes in through that little window.
It will interact
with our object,
in this case a fossil,
and the images
are recorded by our detectors.
NARRATOR: They
fire a beam of X-rays
more than a million
times brighter
than the sun at the fossil.
FERNANDEZ (translated): Because
the synchrotron beam is very intense,
we can get a
signal strong enough
to penetrate the
entire width of the plate
and virtually extract
the fossil from the rock.
NARRATOR: This creates
a 3D model with resolution
down to one-thousandth
of the thickness of a hair.
VOETEN: When we
first saw the images,
we immediately realized that
the bone walls
of the humerus and the ulna
of Archaeopteryx look a
lot like those of flying birds.
NARRATOR: The bone
walls are thin and hollow,
just like those of modern birds.
VOETEN: That was
our first indication
that Archaeopteryx
must indeed have flown.
NARRATOR: As far back
as 150 million years ago,
dinosaurs' ornamental "wings"
are already
evolving for gliding.
♪ ♪
To fly, Archaeopteryx
has to project itself
from a high point.
It uses its clawed
fingers to climb.
From its high vantage point,
it can spot its prey very
easily, and pounce on them
simply by spreading its wings.
But to truly conquer the skies,
gliding birds needed
to learn to flap.
There are several ideas
of how this happened.
The first, known as
the "tree-down"
hypothesis, suggests that
tree-dwelling birds
flapped their wings
to cushion their landing.
The second, known as
the "ground-up" hypothesis,
emphasizes the use
of wing flapping
associated with running
to escape danger
or catch up with prey.
But recently, another
theory has been suggested,
one that can be
seen in birds today.
♪ ♪
ASHELY HEERS: So these
are our performers today.
This is Olympia in gray here,
this is Annie in brown,
and this is Twinkle
Jemima, or Twinky, for short.
NARRATOR: To analyze the
movement of the wings in detail,
evolutionary
biologist Ashley Heers
needs to see them
in slow motion.
HEERS: Here I've got my
high-speed video camera,
and I can visualize what the
camera is seeing on the laptop.
And so you can see that
she's really using her wings
to brake as she gets
ready to land there.
spend a lot of my time
working with developing
birds, or baby birds,
because they can
also tell us a lot
about the evolution of flight.
And in many ways, they look
similar to some of the fossils
that we see that are
documenting this origin of flight.
And so, in these
developing birds,
we have this really
interesting system
where we can see in real
time how a living animal
goes from a flightless animal
to a flight-capable animal
and everything that
happens in between,
both anatomically
and behaviorally.
NARRATOR: One
of the behaviors seen
is wing-assisted running
on an inclined plane.
HEERS: So on the left here,
we have a four-day
old chukar partridge.
It is flapping its wings
to really drive itself
into the substrate here
and increase
traction with its feet,
so that it can ascend
this steep incline.
NARRATOR: This is
not the only behavior
that hints that dinosaurs were
able to develop flapping flight.
HEERS: They may use their
wings to leap into the air and fly,
either for a very
short distance,
or for thousands of miles.
They also use their wings
to come down out of trees
or off of elevated surfaces,
even to swim, either
across the water
or below the water.
And so living birds
show us that, you know,
they use lots of
different habitats
and they use their wings
for lots of different functions.
NARRATOR: Bird flight developed
as an adaptation
to the environment,
as well as to allow
gliding down from trees
or to evade predators on land.
But what exactly was
this great environmental change?
And when did it allow
birds to take the final leap
to full flight?
♪ ♪
One site in particular
can transport us
back to a time when birds
were taking to the skies.
FIELD: It's amazing to
be driving to Las Hoyas,
one of the world's
most important
early Cretaceous fossil sites,
with some of the most
important early evidence
of birds from the
age of dinosaurs.
♪ ♪
NARRATOR: After 30
years of excavations,
an entire prehistoric
landscape has been uncovered.
what was once a wetland,
where there is an
enormous diversity
of species of both
plants and animals.
And we know that this
wetland was freshwater
because it was completely
isolated from the sea.
NARRATOR: Paleontologist
Jesús Marugán and his team
have uncovered a vast
array of plants, animals
and insects,
all part of a complex
and thriving ecosystem.
Digs here have revealed
thousands of fossils,
all between 125 and
MARUGÁN (in English): You see
all those crabs and small crayfish?
FIELD: Ah, each one of those
blue marks represent a crayfish!
MARUGÁN: Yeah.
FIELD: Amazing
how many they are.
MARUGÁN: It's more than 500.
We have the whole
family, from the larvae...
see how small they are? Yeah.
To the juveniles, to the adults.
Yeah, okay. See, with all
the pincers and everything?
Yes, that's crazy!
You can really
tell they're crayfish!
NARRATOR: To process
this huge amount of data,
Jesús is combining
traditional observation
with the very latest technology.
MARUGÁN (translated):
Smile for the camera!
NARRATOR: They use a
drone to photograph the site
and geotags to help recreate
a 3D model of the environment.
Each colored sphere represents
a species or family of species.
The connections between these
spheres indicate interactions.
are found here in this orange section;
the largest ecosystem.
It tells us that the birds
were not just passing through.
They were an integral
part of this ecosystem.
♪ ♪
NARRATOR: Given
the rarity of bird fossils,
the sheer number found suggests
that birds were thriving here.
But that's not all.
These fossils paint a
picture of archaic birds
that are adapting
to geologic change.
Around 175 million years ago,
the super-continent
known as Pangea broke up.
New continents emerged
and oceans and seas rushed
in through the fault lines.
These new territories,
with their temperate climate,
gave rise to flowering plants,
which provided a
new food source.
BRUSATTE: Those
plants diversified,
all kinds of insects
diversified alongside them,
to pollinate the flowers.
And so birds were
probably part of this
general diversification of
life that started with plants
and bugs and reached all
the way to the dinosaurs.
NARRATOR: Las Hoyas shows archaic
birds evolving right before our eyes,
and a class of ancient bird
called the Enantiornithes
is a perfect example.
Wow, so this is Eoalulavis.
That's it, the original.
A beautifully
preserved skeleton.
FERNANDEZ:
Three-dimensionally preserved.
You can see all the
bones of the forelimbs.
NARRATOR: Eoalulavis is
one of these Enantiornithes,
and it's exceptional
in more ways than one.
In particular, it has developed
a highly sophisticated wing.
FIELD: Eoalulavis.
This complicated name has
some important connotations.
FERNANDEZ: Yeah, exactly.
These fossil bird, back in the
day when he was described,
was the first primitive bird
that preserved the alula.
NARRATOR: The
alula is a small mini-wing
on the leading edge
of the main wing.
It allows the bird to
increase lift at will.
This appendage gives the bird
great maneuverability in flight,
and for take-off and landing.
FIELD: It's incredible that
this alula, which of course
helps birds be more
maneuverable in flight,
was present in Eoalulavis,
because this fossil is 129
million years old. Yeah.
So that, of
course, tells us that
this structure has been around
in bird evolutionary history
for at least that long.
NARRATOR: Thanks
to this dexterity in flight,
Eoalulavis is better
able to spot its prey
and swoop down upon them.
This is not the case
for all winged creatures
that populate the Eden
of Las Hoyas.
Europejara, a gigantic pterosaur
with a wingspan of two
meters, needs plenty of space
on the ground to
take off and land.
And when danger strikes,
that can be the difference
between life and death.
JARVIS: We call this
convergent evolution.
Each time flying
evolved in animals...
whether it be birds, bats,
ancient flying dinosaurs...
the wings evolved in the
upper limb on either side,
not one on the head,
one on the tail or
the foot or whatever.
They evolved using
the upper limbs for flight.
NARRATOR: In this
world 130 million years ago,
dinosaurs, flying
reptiles, archaic birds
and ancestors of
early modern birds
all shared the skies together.
This was bird life at its peak.
A plethora of archaic
species living in trees,
perfectly adapted
to their environments.
Birds were taking
over the skies.
But it wasn't to last.
A cataclysmic event
shook the planet.
A gigantic asteroid
six miles in diameter
collided violently with Earth.
Forests burned and volcanic
ash soon filled the skies,
blocking out the sun.
This was an extreme
survival situation,
one that 75% of Earth's
species weren't ready for.
Among the mammals, the smallest,
some weighing
less than one pound,
managed to escape
the catastrophe,
as well as some reptiles
like turtles and crocodiles.
Birds were also hit hard.
Only the smallest,
such as Asterionis,
survived the chaos.
How is it that all but one
group of birds were wiped out?
What did they have
that no other archaic bird
and no other dinosaur had?
Janavis is a bird
that did not make it.
Its fossil dates back
to a time just before
the asteroid hit.
Close analysis is helping
us to better understand
the reasons for
its disappearance.
JUAN BENITO MORENO: Here
you can see this skeleton of Janavis.
We have some of the bones,
particularly the arm bones
and part of the
vertebral column.
NARRATOR: Equipped with teeth,
Janavis has an imposing stature.
Is this why it didn't
survive the asteroid strike?
The key difference between
Janavis and Asteriornis is size.
Asteriornis is much smaller,
a trait that was
key to its survival
post-asteroid strike.
So larger bodied animals,
through this mass
extinction event,
didn't do very well at all.
So a really big
bird like Janavis,
probably would have been
at a major disadvantage
compared to Asteriornis.
After the extinction event,
getting a meal for an
animal the size of Janavis
probably would not have
been a very easy thing to do.
MORENO: They also had
very different ecologies.
That's true. Janavis
was basically a sea bird.
Like one would have been
fishing and eating fish and squid.
Mm-hmm. Asteriornis
was more like a generalist,
ground-dwelling bird eating whatever
he found at the beach. Mm-hmm.
NARRATOR: With the trees gone,
a large number of tree
dwelling birds could not survive.
Instead it was
ground-dwellers like Asteriornis
that held the advantage.
Archaic birds, although
more numerous,
were devastated by the asteroid.
Their ecosystems were destroyed.
In this hostile environment,
their imposing size,
life in the trees and
specialized diets
led to their extinction.
Only modern
ground-nesting birds,
with more flexible diets,
were resilient enough to
survive a decimated landscape.
The sun starts to shine
again, the dust has cleared,
and it illuminates a
world that's devastated,
a world that's almost empty.
There's no T. rexes anymore,
no Triceratopses anymore.
Most of the other
birds were gone as well.
And so, this would have been
a world of abundant opportunity,
open frontiers.
NARRATOR: In the million
years that follow this apocalypse,
new ecosystems emerge.
Out of the ashes of the dinosaur
world, plant life re-appears.
And a whole system
of coevolution,
between flora and fauna erupts.
With little competition,
the surviving birds
enjoy unprecedented
evolutionary success.
JARVIS: Those few
survivors then exploded
into new species
with the opening up
of new environments to become
most of the 10,000
species we see today.
♪ ♪
NARRATOR: A site in
Denmark bears witness
to this key moment
in bird evolution.
On an inland island to the
north of the Jutland peninsula
lies a geological formation
dating back 55 million years.
Made up of more
than 180 layers
of marine deposits
and volcanic ash,
these mineral
strata form the cliffs
of the small island of Fur.
Hundreds of bird fossils
have been unearthed
in this geological jumble.
Many of them are birds related
to today's cranes and rails.
They show that birds had
begun to thrive once more,
at least on the ground.
But were birds back in
the trees by this time?
To understand that,
we need to find birds
with more complex feet,
specialized for grasping
and perching in trees.
NARRATOR: There
is one that indicates
this change in behavior.
This one actually
looks very interesting,
and it seems like it's
got a more complex foot
that might be
specialized for grasping.
So it's not like a modern
perching birds foot
where you have one,
two, three forward
and one backwards.
It looks like it's
probably got two toes
pointing forwards, and
two pointing backwards.
And that is the condition
that you see in a few
modern groups of birds,
including woodpeckers,
parrots, and cuckoos.
The fact that this bird
seems to show pretty clear
specializations for
perching in trees,
tells us that by 55
million years ago,
this lineage of birds was
probably already experimenting
with a tree-dwelling lifestyle.
NARRATOR: Ten
million years after
the asteroid hit,
the surviving modern
birds have diversified.
New species have appeared.
They have adapted to
colonize trees once more.
They diversified like crazy.
And most of the
birds we know today,
everything from ostriches
to emus to hawks to
hummingbirds to
owls, to songbirds
and everything in between
emerged during
those manic years,
decades, centuries, millennia,
after the asteroid
impact cleared the deck.
NARRATOR: In certain
regions of this reborn world,
and because of their
geographical isolation,
some small surviving birds
grow impressively large.
Reaching gigantic proportions,
they evoke the ghosts
of carnivorous theropods.
One in particular appears
to be especially intimidating.
♪ ♪
The huge bird, named Gastornis,
was discovered
in the Paris basin
in 1855.
It was so big, people assumed
it was a fierce predator.
But was it?
If so, why doesn't it
rule the roost today?
we wanted to do this research
was that in the '90s,
two American studies came
to two diametrically-opposed
conclusions,
one team said it
was herbivorous,
and the other team
said it was carnivorous.
With the advancements
of paleontological tools,
we thought we'd finally be able
to answer this
question definitively.
NARRATOR: After crushing
the fossil Gastornis bones,
Paleornithologist Delphine
Angst extracted carbon-13
so that it could be measured
using a mass spectrometer.
We quite literally
are what we eat,
and levels of
carbon-13 correspond
to the amount, or lack
of, protein in our diets.
ANGST (translated): That's
it, everything's weighed,
we can start the manipulation.
ARNAUD (translated): Great,
the spectro is up and running,
so we're ready to go.
ANGST (translated): Perfect.
The carbon-13 analysis of
the Gastornis bones showed us
without any ambiguity that
it was clearly a herbivore.
Combined with other
results we already had,
it showed us that Gastornis
was 100% a herbivore,
and there's no
possible doubt about it.
NARRATOR: Gastornis
was a peaceful herbivore.
It didn't run, but walked.
Despite being
nearly seven feet tall
and weighing more
than 400 pounds,
it was not a
terrifying predator.
ANGST (translated): It disappointed
a lot of people that were sad
that the image of Gastornis
chasing little horses
through the forest was wrong.
My husband's still mad.
NARRATOR: For
several million years,
it walked its clumsy way across
Europe and North America.
But as with any great story,
the fate of birds
was to change again.
the continents collided,
allowing species to
move into new landscapes.
Previously isolated territories
were populated by new arrivals,
including newly evolved,
predatory mammals;
a terrible threat to the
peaceful giant Gastornis.
Faced with these
faster creatures,
and despite their imposing size,
these large birds are not
sufficiently armed to compete.
They are doomed to extinction.
A recent discovery indicates
that other giant birds suffered
the same fate as Gastornis.
Found in New Zealand,
Kumimanu was a giant
penguin, as revealed by
its flipper bones.
You can see here
a Humboldt penguin.
That's your average-sized
penguin today.
An Emperor penguin,
which is the largest
species alive today.
And then this behemoth
here is Kumimanu.
So it's quite an
impressive bird.
By looking at the proportions,
the thickness, the length,
the width of this specimen,
we can estimate the body size.
And so we believe
Kumimanu probably weighed
about 150 kilograms.
NARRATOR: That's 330 pounds.
In the first 15 million
years after the asteroid hit,
birds are triumphant.
They reclaim the reborn forests
and become rulers
of the skies and seas.
However, many of the giants,
like the colossal penguin
and the giant Gastornis,
eventually disappear.
Competition with mammals
is sounding the death knell
for these great birds.
Resistant to the
many climatic changes
that the Earth would
subsequently undergo,
today there are
four groups of birds.
JARVIS: Land, higher-land birds,
waterbirds, the group that
includes the Columbiformes,
that's pigeons and so forth,
and flamingos and a group
that includes the hummingbirds.
NARRATOR: And one
subgroup in particular
has achieved astonishing
evolutionary success
in recent times.
This is the great
family of passerines.
Nesting in our towns,
parks and gardens,
passerines are part
of our daily lives.
Singing birds
that perch in trees,
they demonstrate
extraordinary adaptability.
Contrary to the saying,
sparrows' brains are
actually quite powerful.
FIELD: Pretty good diversity
of birds around, Lizzie.
Yeah, I think most of them
are probably passerines.
Yeah, that makes
sense, I guess passerines
are the most diverse group
of birds in the world, right?
STEELL: Mm-hm.
FIELD: How many
species are there?
STEELL: There
are more than 6,000,
which is more than half of
living bird diversity today.
FIELD: That's a great view
of Eurasian magpie up there.
Yeah, that's a really
nice representative
of a big group of passerine
birds called Corvides.
FIELD: And Corvids in general, I
guess, are probably most famous
for having some of
the very largest brains,
compared to body size,
of all birds.
So these are things
like crows, jays, ravens
and magpies just like this one,
which make them some of the
most intelligent birds in the world.
So it's easy to think about
magpies and their relatives
as the hominids
of the bird world.
They're the smart ones. Exactly.
NARRATOR: Passerine intelligence
is illustrated by their behavior:
the construction of their
nests, their exceptional memory,
and their ability to
communicate through song.
A skill they share
with us humans,
despite our evolutionary paths
diverging some 300
million years ago.
Something happened in
nature to get this convergence
to be similar between humans
and these modern birds.
So what we and others had found
is that in our forebrain area
evolved this new circuit,
and that circuit
evolved in a similar way
with a direct connection
to the voice circuit
in songbirds, humans,
parrots, and hummingbirds.
Why only these few species?
If you evolve vocal learning,
you're more likely to be eaten,
and you won't survive.
Only if you're at the
top of the food chain
or near the top of the
food chain, you can.
We found that songbirds
and parrots evolved
from apex predators.
NARRATOR: Birds
are beautiful examples
of evolution's power
to create variety.
Today, there are
more species of birds
than there are mammals or
any other terrestrial vertebrates.
They thrive around the world,
perfectly adapted
to the tremendous diversity of
environments and landscapes.
Birds are incredibly
successful today.
And I think it is a
really neat fact of life
that there are double
the number of bird species
than mammal species.
And by that measure, the age
of dinosaurs still continues today.
NARRATOR: Long
live the dinosaurs.
♪ ♪
♪ ♪
♪ ♪
♪ ♪
♪ ♪
♪ ♪
♪ ♪
Welcome to our World! Where we serve you cookies to ensure you get the best viewing experience on our site.
Did you know that you can remove censorship board-wide, use our advanced search functions, be notified when new content is posted, join our memberships, set episodes to show in any order you want & more if you are logged into your account?
Register or sign in here: ucp.php?mode=register
Did you know that you can remove censorship board-wide, use our advanced search functions, be notified when new content is posted, join our memberships, set episodes to show in any order you want & more if you are logged into your account?
Register or sign in here: ucp.php?mode=register
52x03 - Dino Birds
Watch/Buy Amazon
Nova often includes interviews with scientists doing research in the subject areas covered and occasionally includes footage of a particular discovery.
Nova often includes interviews with scientists doing research in the subject areas covered and occasionally includes footage of a particular discovery.