David Reich

And so it just makes me think that things are going to be surprising the next time we look at something that's really not looked at before.

So the line of evidence I'm talking about is one based on epigenetic modification of genomes.

So just to explain what that means, the genome is not just a sequence of letters, DNA letters, adenines, thymines, guanines, and cytosine, A-C-T-G.

It also is decorated in anybody's cells by modifications that tell the genes when to be on and off in what conditions.

So an example of such a modification is methylation in cytosine-guanine pairs.

So this turns down a gene and makes it not functional in certain tissues.

And this methylation is bestowed by cellular environments and differs in different cells and also in different species to identify which genes are more active or more passive.

And it's not directly encoded by the ACTGs locally.

It's encoded by something else and sometimes even passed on by your parent directly.

So it's really very interesting.

So this can be read off ancient genomes.

the methylation pattern survives in Denisovan and Neanderthal genomes, and we can actually learn which genes were turned down and turned up.

So work by David Gochmann and Liron Carmel and colleagues created these maps of where in the Denisovan genome

where in modern human genomes, genes are turned on and off.

And there's a lot of technical complexity to this problem, but they identified differentially methylated regions, several thousand sections of the genome that were consistently and very differently turned down or turned up in Neanderthals and modern humans.

And when they looked at the set of differentially methylated region, roughly a thousand of them, that were systematically different on the modern human lineage, and asked what characterized them, was there particular biological activities that was very unusual on the modern human-specific lineage, there was a huge statistical signal that was very, very surprising and very, very unexpected, and it was the vocal tract.

So it was the laryngeal and pharyngeal tract.

And because you can actually learn from little kids with congenital malformations when you knock out a gene, when a gene gets knocked out by an inborn error of genetic transformation, of genetic...

Kids will have, for example, a face that looks different or a vocal tract that looks different and so on.

You know what the effect of knocking out these genes is.