Dr. Erich Jarvis

The second thing that's useful to know

is that all vocal learning species use their learned sounds for this emotional, affective kind of communication.

But only a few of them, like humans and some parrots and dolphins, use it for the semantic kind of communication we call speech.

And that has led a number of people to hypothesize that the evolution of spoken language of speech evolved first for singing, for this more like emotional kind of made attraction, like the Jennifer Lopez, the Ricky Martin kind of songs and so forth.

And then later on, it became used for abstract communication like we're doing now.

You ask a great question because we both know some colleagues like Winrich Freibold at Rockefeller University who study facial expression and the neurobiology behind it.

Non-human primates have a lot of diversity in their facial expression like we humans do.

And what we know about the neurobiology

of brain regions controlling those muscles of the face is that these non-human primates and some other species that don't learn how to imitate vocalizations, they have strong connections from the cortical regions to the motor neurons that control facial expressions.

And even though it's more diverse than these non-human primates, there was already a pre-existing diversity of communication, whether it's intentional or unconscious, through facial expression in our ancestors.

And on top of that, we humans now add the voice along with those facial expressions.

So it's like an email too.

You're emailing and someone says something by email.

Someone can interpret that angrily or gently and it becomes ambiguous.

The facial expressions get rid of that ambiguity.

What I think is going on is to explain what you're asking is about

I'm going to take it from the perspective of reading something.

You read something on a paper, the signal from the paper goes through your eyes, it goes to the back of your brain to your visual cortical regions eventually, that visual signal then goes to your speech pathway in the motor cortex in front here in Broca's area, and you silently speak what you read in your brain without moving your muscles.

Sometimes, actually, if you put electrodes, EMG electrodes, on your laryngeal muscles, even on birds you can do this, you'll see activity there while reading or trying to speak silently even though no sound's coming out.

And so your speech pathway is now speaking what you're reading.