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