Migrations in Siberia
The story of how our early human ancestors originated in Africa and then colonised the Earth is an evolving one. And now scientists have added a new piece to the puzzle, as Adam Murphy has been finding out from geneticist Eske Willerslev…
Adam - When we think of northeastern Siberia, the most northeastern part of Russia, we think of a cold place where humans couldn't live. Plenty of people do live there though, and while archaeological records go back 30,000 years, the genetics of the people who live there can’t be traced back past about 10,000 years. Published in Nature, new work took DNA from milk teeth found in the region and uncovered evidence of a previously unknown group of humans called the Yana people. These people would predate the ancestors of Native Americans into Siberia, and fill in a huge gap in the story of human migration. I spoke to Eske Willerslev from the University of Cambridge about what got him interested in a story like this in the first place.
Eske - Well I've always been interested in the peopling of northeastern Siberia, because when I was young, in my late teens and early 20s, I spent time as an explorer and also a trapper in northeastern Siberia, so that was before I became a scientist. But I was always wondering back then: why do we have all these people speaking different languages, having different lifestyles, and what are their relationship to Native Americans, which are just on the other side of the Bering Strait?
Adam - What did he find out then?
Eske - We basically have uncovered the population history of northeastern Siberia. And there has been a lot of mystery connected to that story, because the archaeological record goes back more than 30,000 years for this area, while if you look at contemporary people and their genetics it suggests that the history is no older than about 10,000 years. So by sequencing ancient skeleton remains we have found out that there has been at least three migration waves of people into northeastern Siberia, and the earliest one dating back to 31,000 years. This is from two tiny milk teeth found at a site called the Yana site, close to the Yana River, and these people are a people that we didn't know before. It's a very old people that diversified approximately at the same time when Europeans and Asians are developing as distinct groups. So there is actually kind of a third branch leading up to these Yana people but that are now extinct.
Adam - These Yana people helped puzzle out the story of modern Siberians and also of Native Americans.
Eske - So Native Americans, many people thought that the ancestors of Native Americans must have been the first people in Siberia, but they're not; they're actually the second migration coming up there, and they are mixing up and replacing these Yana people. And then there's a third migration happening within the last 10,000 years, and this is the one giving rise to most Siberian people today.
Adam - But getting DNA out of 30,000 year old milk teeth can't be easy. How did they manage it?
Eske - Well, that was also a challenge, because normally we'd use the root of the tooth. And the crown, we basically don't believe there's much DNA in it, so we are keeping that and returning it to the museums and so forth. But in this case there was almost no root material left in these tiny, tiny milk teeth. So we asked permission to basically pulverise the crown, and we got that permission, and there was beautiful DNA preserved in the crown of these teeth. And from there we reconstructed very high quality genomes.
Adam - The climate of that part of the world isn't exactly the most inviting. How did these people adapt to live there?
Eske - That is the interesting part, I think, because we always think of northeastern Siberia as one of the most hostile environments. I mean, it's one of the coldest areas on Earth, temperatures go down to below -60°C, and it's just not a place where we expected humans would like to be. And therefore the general view has also been that the population history of northeastern Siberia has been very simple, right; it's not like many migrations, or many different people wanted to go up there; but we can see this is definitely wrong. It's just as, you can say, dynamic as is the pre-history of Europe, for example. And it's probably because one thing in the equation we forget about when we think about northeastern Siberia today is that, back in the ice age times, this was an area for a diverse fauna of big mammals. There was woolly mammoths, rhinoceros, horses, bison, etc. And what we can see is that the Yana people up there 31,000 years ago were living as big game hunters. They were mainly living from woolly mammoth and woolly rhinoceros. So it's probably been a very productive place, and even though it's cold, and windy, and you’re probably freezing your butt off up there, well at least there was a lot of food.