Dr. Erich Jarvis

years in a way that adults would not be able to experience.

And so you get a hybrid.

And the lowest common denominator is going to be what they share.

And so the phonemes that they've retained in each of their languages is what's going to be, I imagine, used the most.

One of the things that differ in the speech pathways of us and these song pathways of birds is some of the connections are fundamentally different than the surrounding circuits, like a direct cortical connection from the areas that control vocalizations in the cortex to the motor neurons that control the larynx in humans or the syrinx in birds.

And so we actually made a prediction that since some of these connections differ, we're going to find genes that control neuro-connectivity and that specialize in that function that differ.

And that's exactly what we found.

The genes that control what we call axon guidance and formation and connections.

And what was interesting, it was sort of in the opposite direction than we expected.

That is, some of these genes, actually a number of them that control neuro-connectivity were turned off in the speech circuit.

And it didn't make sense to us at first.

And so we started to realize the function of these genes are to repel connections from forming.

So repulsive molecules.

And so when you turn them off, they allow certain connections to form that normally would have not formed.

So by turning it off, you got to gain a function for speech.

Other genes that surprised us were genes involved in calcium buffering, neuroprotection.

like a parvalbumin or a heat shock protein.

So when your brain gets hot, these proteins turn on.

And we couldn't figure out for a long time, why is that the case?

And then the idea popped to me one day and said, ah, when I heard the larynx is the fastest firing muscles in the body, all right?