I used each of the 12 different components as "test data" in a supervised ADMIXTURE analysis that used the other 11 components as "reference data". This simple procedure can show what each component appears to be made of, if it is seen in the context of the remaining components. It is a good way to demonstrate relationships between them.
Here are the results:
- Gedrosia appears to be Caucasus + a slice of Siberian
- Both Siberian and Southeast Asian appear to be wholly East Asian
- East Asian on the other hand, appears to be mostly Southeast Asian + minority Siberian
- Northwest African appears to be Caucasus + a minority Sub Saharan
- Atlantic Med appears to be Caucasus + a slice of North European
- North European appears to be Atlantic Med + Gedrosia with a slice of Siberian
- South Asian appears to be Caucasus + East Asian
- East African appears to be Sub Saharan + minority Caucasus
- Southwest Asian appears to be Caucasus
- Sub Saharan appears to be East African
- Caucasus appears Atlantic Med + Gedrosia + slices of Northwest African and Southwest Asian
It could be argued that these results represent a confluence of peoples from all over West Eurasia into the highlands of West Asia where the Caucasus component is modal. But, the Caucasus region is arguably the most linguistically diverse in West Eurasia, and many of its languages do not appear to have come from elsewhere. Also, the Near East (where the Caucasus component is the most important one in most populations) is the birthplace of agriculture, which has demonstrably affected most of West Eurasia. On balance, this analysis seems consistent with population expansions out of West Asia.
The following graph summarizes the relationship between the 12 components. I used color intensity of the edges to indicate admixture intensity:
Finally, a few points to remember:
- the South Asian component appears like a mix of of Caucasus and East Asian; the latter probably acts as a stand-in for the Ancestral South Indians of Reich et al. (2009)
- Similarly, the Gedrosia/Siberian influences on the North European component do not necessarily mean direct influences from these two regions; an explanation for these influences may intersect with the issue of East Eurasian-like ancestry in northern Europe
- It is the Caucasus, rather than Southwest Asian component that seems to donate to the Northwest African and East African ones. That seems to flaunt geography, but probably indicates that the Southwest Asian component, with its strong Semitic associations (see distribution in K12b spreadsheet) represents a more specialized form of the more generalized Caucasus component.
- Some components appear to be "terminal", affected but not much affecting: Southwest Asian, Northwest African, and Southeast Asian. These tend to appear at high K in admixture analyses, and probably represent either recent mixtures (Northwest African) or specialized forms of more generalized ones (Southwest Asian of Caucasus and Southeast Asian of East Asian)
- Finally, remember that living populations show admixture proportions of many of these components. So, for example, the East African population often has Southwest Asian admixture, even though the East African component lacks it. And, as mentioned above, this may reflect the more generalized west Asian admixture that has affected East Africa, as well as the more specific Arabian admixture, associated e.g., with the spread of Semitic languages. Please refer to the K12b spreadsheet for admixture proportions of populations for the 12 components.
And, here is the graph showing how they seem to contribute to each other.
A few observations:
- Amerindian appears wholly Siberian
- East Asian appears Siberian + South Asian + slice of Australasian
- African appears South Asian. I would attribute this to Africans being related to both West and East Eurasians approximately symmetrically, so in this type of experiment, South Asian (which is an ANI/ASI mix) appears like the best match
- Atlantic_Baltic appears Caucasus_Gedrosia + Southern + slice of Amerindian
- Australasian appears South Asian. I would guess that ASI and Australo-Melanesians share deep common ancestry from the earliest settlement of southern parts of Asia.
- Siberian appears East Asian + slice of Amerindian
- Caucasus_Gedrosia and Southern appear Atlantic_Baltic
- South Asian appears an about equal mix of East Asian + Caucasus_Gedrosia + slice of Australasian