David Reich

We can actually imply directionality to how the modern human specific changes are.

And the directionality is to change the shape of the vocal tract, which is soft tissue not preserved in the skeletal record, to be like the way ours is distinctive from chimpanzees.

So in the shape that we know is very helpful for the articulation of the range of sounds we use that chimpanzees don't have in their laryngeal and pharyngeal tract.

So even though we don't have surviving hard tissue like skeletons from this part of the body, we now have this methylation signature which suggests that these changes have occurred specifically on our lineage and are absent in both the Neanderthal and Denisovan lineages.

So if you think this change in the vocal tract is important in language, which seems possibly reasonable, then maybe that's telling you that there's very important changes that have happened in the last half million or a few hundred thousand years

specifically on our lineage that were absent in Neanderthals and Denisovans.

We don't know that.

We just know that today we have it.

So it could have been only a couple of hundred thousand years ago or a hundred thousand years ago that these changes happened.

Separate 200,000 years ago.

Right, right.

Although there is gene flow between all groups of modern humans, at least at low levels, going to 100,000 years.

It's just most of the separation between Khoisan and other groups happens 200,000 years ago.

So one thing that what you're saying makes me think about is that it doesn't map on in a simple way as an analogy.

So one of them is that the human brain is maybe only three times larger than that of a chimpanzee.

And that's not the kind of increase that computability has had since 40 years ago or something like that, which is many, many orders of magnitude increase.

Not a factor of three, but many, many orders of magnitude increase.

And in fact, I'm aware of studies that have, for example, compared raw computability of chimpanzee babies to human babies.

In fact, it's similar.

For example, ability to solve logic puzzles is pretty similar between chimpanzees and humans.