Lulu Miller

But crawling up from underground...

were the earliest mammals.

They were tiny.

They were like little mice.

Some of which had spent most of their lives climbing up trees, running from dinosaurs, burning up oxygen at an incredible rate.

And so they had evolved this really powerful muscle called the diaphragm that sits below the lungs that allowed them to take in air and push it out rapidly and powerfully.

This would kind of change everything.

Because even though you had these tiny little itty bitty mammals that had their tiny squeaks, over time as they evolved into bigger mammals with bigger lungs and bigger, more powerful diaphragms, you'd get bigger sounds, more air.

And John says at the same time, that valve, that slit in the throat.

Little bits of cartilage appear on it and so do these folds.

John says all of this means that the voice is becoming more and more of a tool for those things that drive evolution.

Like asserting dominance, fighting off rivals, showing affection, wooing mates.

The voice starts communicating basic emotions.

And the other thing is that mammals.

The way that their young feed is on.

Mammary glands.

A breast.

That's new with mammals.

is an amazing system of muscles in the mammalian face and throat and tongue.

And so if you're an animal with a big complex brain, John says you can start doing things like... Hitting the tongue against the back of the teeth for tuh and duh.