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In 2011 I was having dinner with an old friend who was an engineer at Intel. He also has a Ph.D. from MIT. Smart guy. But when I mentioned casually offhand that we were all a few percent Neanderthal (outside of Africa), he was surprised. I was a bit shocked, as I explained that this was a huge science story. The Neanderthal genome had been published the previous year. How could my friend not have known?
He was totally unembarrassed, and told me I overestimated how closely the public followed genetics and paleontology. I’m sure he was right. But it’s hard to remember sometimes.
We’ve gone further beyond where we were in 2010. We now have a really good grasp of a lot of population dynamics in Eurasia over the past 20,000 years. Probably the best place to start is with this preprint, The genetic structure of the world’s first farmers. But the general outlines were already evident a few years back in Toward a new history and geography of human genes informed by ancient DNA.
Most of the world’s population seems to descend from a mixing of a set of groups which 10,000 years ago were distinct. How distinct? We’re talking about Fst values on the order of 0.10, which means that ~10% of the variation genetically is partitioned across two pairwise populations. That’s about what you see between Europeans and Chinese today. Some of the Fst values were a bit higher, some lower, but the 0.10 seems about right.
To make it easy for some of you, I’ve labeled and placed the approximate locations of ancestral groups to modern Northern Europeans ~10,000 years ago. What I’m trying to represent is a map which shows the modal regions of distribution of ancestors that Northern Europeans today had 10,000 years ago. So, for example, since ~15% of the ancestry of Northern Europeans is “Ancient North Eurasian” (ANE), a lot of ancestors of Northern Europeans alive today would be living somewhere in the broad expanse of Central Eurasia (now, because of various demographic events the number of ANE was probably lower than farmers, perhaps lower than the 15% contribution to the modern genomes).
A substantial proportion of the ancestry of Northern Europeans is “European hunter-gatherer,” dating to the Pleistocene. But here’s the kicker: most of that ancestry dates to after the LGM, to about ~15,000 years ago. The really deep Pleistocene ancestry in Europe is only found at very low levels now.
The final issue is that a lot of the phenotypes that we racially code are recent. This probably explains why groups like the Kalash and Nuristanis can look more like Europeans than South Asians, but they’re genetically more like South Asians.
What does any of this have to do with non-scientific things? I don’t really know. My interest in population structure is intellectual, not personal. But a certain type of person should probably stop talking about how white people have been in Europe for 40,000 years. First, the ancestors of modern Europeans 40,000 years ago were almost all residing outside of Europe. An assertion that holds until 15,000 years ago. And most would still be resident outside of Europe 8,000 years ago as depending on how you count/calculate* And, perhaps more importantly, the typical phenotype of Northern Europeans probably really coalesced only around ~5,000 years ago.
* Definitely true for Southern Europeans, but conditional on Northern Europeans depending on where you draw Europe’s eastern boundary.
Addendum: I stole the title from John McWhorter’s book, Our Magnificent Bastard Tongue.
Also, this is not to say that
1) population structure today is trivial in a phylogenetic sense, it isn’t.
2) it is not to say that population structure functionally irrelevant, it isn’t.