David Reich

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.

And some people argue that humans are not even more intelligent than chimpanzees.

at some fundamental ability to compute, and that what makes human distinctive is social learning abilities, and that that's where a lot of our ability has gone, our ability to see other people, to empathize with other people, to copy other people, to incorporate bodies of information that are learned by other people.

And so I am not an expert in this topic, but it's a very appealing group of ideas that the adaptations that humans have are ones that allow us to access a rich amount of shared knowledge and not just to rely on figuring out each thing.

So that's not obviously the same as just add more computability, but maybe it has some similarities.

So the model that—this is really outside my expertise, but ideas that have been floated, and I will summarize them possibly badly, are that in every group of human beings of hundreds of people, which is the size of a band or sometimes a thousand of people, they accumulate shared cultural knowledge, shared—

knowledge about tools, knowledge about life strategies, and they build up a shared knowledge more and more and more and more.

But if you have a limited size group of people that's not interacting with the sufficiently large group of people, either occasionally this group has an information loss, there's a natural disaster, key elders in the group,