(sound of footsteps)
Maybe it's the power trying to come back on?
(thunder, crashing)
(rooster crowing)
The Jurassic Park movies are built around a dream: Using science, humans could one day
walk among the giant reptiles that used to rule the Earth.
(roar)
Spoiler alert: We already do. Thanks to science, we know our planet is home to 10,000 or so
species of living dinosaurs. We just call them birds.
(roar)
How do we know this is true? Let’s leave the nest, and bring birds’ place on the
tree of life into view.
Everything on Earth with this sort of four-limbed, belly in the front, spine in the back,head
on top arrangement is a tetrapod. Last year we did a whole series on why tetrapod bodies
are shaped this way, so check that out here or down in the description.
Now, starting with a common ancestor of all tetrapods, amphibians branched off first,
then us mammals, followed by turtles, lizards and snakes, and then the group we call archosaurs,
which contains crocodilians, pterosaurs, and finally dinosaurs. Birds are in here.
Zoom in on the dinosaurs and we start to see some familiar faces from John Hammond’s
island. There’s a lot there, but the important part is that the birds we know today didn’t
branch off until way up here.
I don’t know about you, but when I look at a cassowary, I don’t need any convincing
that birds are dinosaurs, but let’s assemble the evidence anyway.
When most of us think of dinosaurs, we think of bones. By comparing the skeletons of things
that are very dinosaur-ish to things that are very bird-ish to the sort of dino-bird-ish
things in between, well, you’re about to look at chickens in a very different way.
The most famous dinobird is our friend Archaeopteryx. Its fossils give us a look at the transition
between scaly-reptiles and birdy-birds, because they share features from both.
Like birds, its forelimbs were enlarged like wings, its pubic bone pointed toward its tail,
along with one of its toes, and it had fused clavicles. That’s right, just like your
Thanksgiving turkey, dinos from T. rex to Archaeopteryx had wishbones.
Now in the reptile column, these dinobirds had long tails, ribs around their belly, claws
on their fingers, and teeth. I’m so glad birds don’t have teeth anymore. Nightmare
fuel.
Dinosaurs became pretty front-heavy as their forelimbs got bigger, and later as they lost
their tails, so in order to not topple over they adopted a sort of crouching posture.
We see it in birds from sparrows to ostriches today.
In one of the most hilarious experiments ever recorded, scientists attached prosthetic tails
to chickens and sure enough, with the added weight in back, they adopted a more dino-like
walk.
We think that how birds move their wings during flight even matches how Velociraptors and
their relatives would snap their forelimbs out to grab prey, but don’t worry, despite
what the movies say, they were only about knee-high.
Oh, and those clever girls should have been covered in feathers!
Scientists have unearthed dozens of fossils showing evidence of feathered dinosaurs, but
for some reason Jurassic Park and other dino movies have a strict no-plumage policy.
Feather forms ranged from simple quills with just a few branches, like what we see in baby
birds, to full-fledged fabulous feathers. Some fossil feathers even tell us what color
they might have been, awww, so fluffy!!
We’re not quite sure when birds took to the air, but extinct dinosaurs were were too
heavy to have used feathers for flight. They probably served other colorful purposes instead.
(crash)
Birds today are tetrachromats, meaning they have four color receptors compared to our
three. Many of them can see down in the ultraviolet range, meaning they see colored plumage, like
these beautiful painted buntings, in ways that we can’t even imagine.
Today, birds use that exotic plumage and their ultra-vision to put on some pretty amazing
mating rituals. Extinct dinosaurs definitely had feathers,
and they probably shared this tetrachromacy, so what’s to say that we wouldn’t find
similar shows at Jurassic Park?
In a previous video, I talked about how the T. rex roar in Jurassic park was made from
a mixture of a baby elephant, a tiger, and an alligator, but what did dinosaurs really
sound like? Birds today create their symphonies using an organ called a syrinx, and their
brains have evolved specially to create and decode those complex songs.
Unfortunately, dinosaurs lacked both of these adaptations. So while we couldn’t teach
a dinosaur to talk like a parrot, it’s likely that they made some interesting noises.
The large hollow crest of Parasaurolophus could have been used as a sort of resonator.
Scientists from Sandia Labs reconstructed what that might have sounded like.
(horn playing)
Why did birds survive as the rest of their reptilian cousins drifted off into the great
fossil pit in the sky? Why don’t we have T. rex-sized parrots?
Well, after the meteor strike in the Yucatan, plants became more scarce, and without enough
food, big-bodied herbivores went extinct along with the large carnivores that ate them. But
smaller meat-eating dinosaurs, the same lineages that led to birds, were able to survive with
smaller bodies and on less food.
"Life… uh, finds a way"
From fossil to feathers, it’s clear that birds make their nest in the tree of life
right next to creatures that haven’t walked the Earth for 65 million years. They aren’t
relatives of dinosaurs, they are dinosaurs.
Stay curious.