Could you just add a kind of high-level sketch for us how you went about answering this question of how linguistic diversity has changed over the last 12,000 years?

There's two main ingredients to the modeling strategy I developed in this paper.

The starting point has to do with what seems to be a fundamental constraint of human populations.

If we go back to when the world was mostly hunter-gatherer and fisher, and maybe even mostly forager, meaning that people would essentially source energy from the environment, and as they do it, they will move around through a part of the year, then that fact of subsistence seems to limit the number of total people that you can keep together into a central population.

If you grow to be too large, then you need to undergo fission so that you can continue to nurture all the members of your population.

And if you go below an optimal size, there is a risk that you won't be able to survive.

So there seem to be strong pressures for a range of population sizes, of course, modulated by a large number of factors, including availability of technology, a region of the world, ecology, etc.

Could you say a little bit about this study that I'm alluding to on the human bite and human sound systems?

So that presumably if it was growing at one point and it's now shrinking, there was a peak at some point.

Absolutely.

And I have to say that was the most surprising finding.

We weren't committed to any specific pathway from ancient to contemporary language diversity.

But one extremely robust result that we found is that 12,000 years ago, the total number of languages, uh, keeps growing, following in a way the, the global demographics of humans.

But at some point between 3,000 to 1,000 years before present, you get to see a fantastic peak in global linguistic diversity, which we, I think, dab in the paper as the golden era of linguistic diversity, where perhaps there were anything between 6 to 10 to 15 times the number of languages that exist now.

Which reveals something extremely interesting about r- the recent stages of human culture and language, which is there has been a very rapid bottleneck in global diversity that preexisted the colonial expansions that are relatively recent.

So you're saying a decline that could've started 2,000 years ago or something because?