Thursday, 7 April 2011

The "Siberian Belt": unsupervised run

Trying to find clues to the origin of "Forager A", the non-Fertile Crescent element in Europeans and Caucasians, I decided to run an unsupervised analysis of all Northern Eurasian populations. I don't have much faith in components from unsupervised mode actually corresponding to closely related ancestral populations just because ADMIXTURE decided on it's own it's so. Still unsupervised runs are great to get a picture of relationships.
I also included the San, since I wanted to see if they were actually related to "Forager A", Hadza, Mbuti Pygmy, !kung, and Papuans, Melanesians. And why not, also the East Asian populations because of the proposed Altai language family and it's tenuously possible links to Korean and Japanese. And since I was at it, I also threw in those often forgotten populations of the "Siberian" belt, Amerindians.

Remember this is an unsupervised run. Some noise <1% is expected, but I think >1% consistent components across similar populations are significant. I won't immediately name the components ADMIXTURE came up with. Also, these are kind of chunky, particularly for smaller components, so this is just a simple experiment I wanted to share, to get hints about what "Forager A" might actually be, and also for my future East Asian Neolithic run.

These were included to clear any doubts of "San" relatedness of Euro aborigines.
"Forager A" is definitely a Siberian-like population, only aboriginal to Europe, and mostly replaced by the Fertile Crescent expansion I think.
I don't think this means that "Forager A" is about Amerindian women or slaves brought to Europe a few centuries ago by the way... At least it's hard to explain how they would get to Dagestan.
I think "Forager A" is likely "Siberian"-like. As for closer affinities among "Siberians" it could be drift/founding effects making more distantly related populations seem closer? Seems unlikely and there are other theories considered unlikely as well...
"Yoruba" in Druze and others is I think attracting a bit of the Nile Core Component (Northeast African) by the way, since these could be distantly related via the Green Sahara.

This is an unsupervised run though. It is quite chunky. These are small elements.
For now, I'll just say that "Forager A", if thats what unsupervised ADMIXTURE is picking up, looks interesting indeed.
I'll also be doing a supervised, hopefully more homogeneous run.

I also ran East Asian populations in the same run, I'll present them in the next post tomorrow.


  1. There is a considerable amount of American Indian gray that gets into Asia. Usually this kind of thing is said to be the result of the Asian origin of American Indians but I'm wondering about another possibility: Could a demographic expansion from South and Middle America have led to the diffusion of some genes back into Asia?

  2. If you're mentioning grey in Chukchi and other Siberians, I think it's possible since Solutrean (and Clovis) technology was particularly impressive.
    If you're speaking of Han and related Neolithic populations further South, I think a more likely explanation is that the Chinese or East Asian Neolithic is itself a "Siberian Belt"-derived Neolithic expansion. I don't have a large amount of confidence in any of this yet, still I think it's the simplest model to explain what we're seeing.

  3. I had in mind, Chukchi gray. On the same lines, I wonder if the development of agriculture in New Guinea led to some gene flow back to Indonesia and Asia.

  4. I think similarities are maybe more likely due to the common Coastal Migration origin of these populations. Papua's Neolithic was not sufficiently developed I would guess, to undergo major expansion and it was adapted to the highland niche. Still who knows? I do suspect an incipient Neolithic in the related original South Asian populations though, and this might have extended in some form to Indochina, Indonesia? The Fertile Crescent+Coastal Migration element in Southeast Asia and Malays seems too widespread there to be just noise, and maybe some more suitable soil/climate regions were occupied by this mixed Neolithic people...
    I'll see if I can get further clues on this later.