WEBVTT - How Do Birds Sing?

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<v Speaker 1>Welcome to brain Stuff production of iHeart Radio, Hey brain Stuff,

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<v Speaker 1>Lauren vocal bomb here. Convergent evolution is the idea that

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<v Speaker 1>two organisms that aren't very closely related can independently evolve

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<v Speaker 1>a very similar trait. For instance, the last ancestor that

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<v Speaker 1>we shared in common with an octopus probably looked a

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<v Speaker 1>lot like a worm, even though that animal might have

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<v Speaker 1>been able to detect light and dark. It took something

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<v Speaker 1>like seven dred and fifty million years of both human

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<v Speaker 1>and octopus ancestors working on being able to see properly

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<v Speaker 1>to evolve the incredibly similar eye structures that humans and

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<v Speaker 1>octopuses now share nifty. But this isn't how it always happens. Take,

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<v Speaker 1>for instance, the voice box of a bird. It's called

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<v Speaker 1>a syrinx, and no other organism on Earth has one.

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<v Speaker 1>It's something of an evolutionary mystery. Why not? Actually, After all,

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<v Speaker 1>other animals need to be able to communicate, just like

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<v Speaker 1>both cephalopods and mammals need to be able to see

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<v Speaker 1>what they're doing. In fact, the SEARINGX is arguably much

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<v Speaker 1>weirder than the high acuity camera style I we share

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<v Speaker 1>with the octopus because the SEARINGX came out of nowhere.

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<v Speaker 1>Evolutionarily speaking, it could be argued that the synx is

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<v Speaker 1>a bit redundant in bird anatomy, as they also possess larynxes,

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<v Speaker 1>the voice box structure that they share with we mammals

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<v Speaker 1>and some amphibians and reptiles, though it only functions very

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<v Speaker 1>well in mammals and a few lizards. The larynx is

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<v Speaker 1>what enables cows to move, dogs to bark, and babies

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<v Speaker 1>to cry, and it's situated at the top of the throat. However,

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<v Speaker 1>birds use their synx to make their fluty vocalizations. It's

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<v Speaker 1>similar to the larynx and that it's made of folds

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<v Speaker 1>of vocal membranes supported by cartilage. However, the synx is

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<v Speaker 1>buried deep in a bird's chest, right above where their

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<v Speaker 1>tracheo bronchial tube splits off into their lungs. In twenty sixteen,

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<v Speaker 1>paleontologists from the University of Texas in Austin reported that,

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<v Speaker 1>based on fossil evidence, the structure we know as the

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<v Speaker 1>syrinx is around sixties million years old. Since then, the

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<v Speaker 1>research team has been comparing the larynx and syrinx anatomy,

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<v Speaker 1>genetics and development of birds to those of modern reptiles

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<v Speaker 1>and have discovered the evolution of the syrinx is even

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<v Speaker 1>stranger than previously thought. In a paper published in eighteen

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<v Speaker 1>issue of the Proceedings of the National Academy of Sciences,

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<v Speaker 1>the research team reported the function, form, and development of

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<v Speaker 1>the syrinx and the larynx are actually quite different. For starters,

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<v Speaker 1>the vocal cords of the larynx are manipulated by muscles

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<v Speaker 1>attached to the cartilage that supports them. The seynx, on

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<v Speaker 1>the other hand, partially attaches to muscles that in other

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<v Speaker 1>animals fastened the tongue to the bones connecting the arms

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<v Speaker 1>to the rest of the body. Secondly, while baby birds

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<v Speaker 1>and baby lizards are developing different types of cells form

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<v Speaker 1>their respective voice boxes, larynxes are made of a mixture

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<v Speaker 1>of mesoderm and neural crest cells, which are a temporary

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<v Speaker 1>group of cells that arise from the ectoderm, while the

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<v Speaker 1>syrinx is created exclusively using mesoderm cells. So at some point,

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<v Speaker 1>the ancestors of modern birds just started making a new

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<v Speaker 1>voice box, which eventually took over the job of the larynx.

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<v Speaker 1>As a result, now birds can sound like this. This

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<v Speaker 1>research is exciting because although convergent evolution is a really

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<v Speaker 1>cool thing for scientists to wander over, a true evolutionary

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<v Speaker 1>outlier is arguably cooler. Today's episode was written by Jesselyn

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<v Speaker 1>Shields and produced by Tyler Clang. Brain Stuff is a

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<v Speaker 1>production of I Heart Radio's How Stuff Works. For more

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<v Speaker 1>on this and lots of other convergent topics, visit our

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<v Speaker 1>home planet, how stuff works dot com. And for more

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