Rory McLeod

So what's quite exciting is that the plague strains that we have from Lake Baikal are quite close to the kind of root of the evolutionary tree of all the plague.

So these are really close to being an ancestor to the entire diversity of plague Yersinia pestis, including those Black Death plague strains.

You can kind of think of plague strains as somewhat like cocktails, cocktails of genes.

And some of these genes also interact to make the cocktail significantly more potent.

So in the case of the plague strains that led to the first pandemic and the Black Death, a gene emerges around about 3,800 years ago that allows the plague infection to take on this form of bubonic plague, being transmitted by flea bites and resulting in these horrible buboes that have led to so much suffering and are classically depicted with the Black Death.

That's a much later adaptation, exactly.

So what's happening with these early plague strains in prehistory, well over a thousand years before that emerges, you have a different set of ingredients resulting in potency.

And unfortunately, this different set of ingredients includes a gene that we don't see later on called YPM, which is a super antigen, which is unfortunately especially deadly for children.

Yeah, no, it's really extraordinary that they buried the dead in this particular way.

And it really makes you wonder what would have happened when there weren't people who were survivors who were able to bury the dead like this.

I mean, are we missing a huge amount of other evidence of outbreaks of plague amongst hunter-gatherers simply because everybody died or there wasn't anybody fit or strong enough or in that position to be able to bury the dead?

And it's also just so close in the evolution of plague to when we think plague first emerges as a separate species.