''Meanwhile we may note that a detailed analysis of 571 modern Negro crania, made by advanced mathematical techniques, has shown that these crania gravitate between two poles, a Mediterranean Caucasoid and a Pygmy one. The former type is again divisible into an ordinary Mediterranean and a Western Asian type, which suggests more than a single northern point of origin for the Caucasoid element. As we shall in greater detail in Chapter 8 and 9, the Negroes resemble Caucasoids closely a number of genetic traits that are inherited in a simple fashion. Examples of these are fingerprints, types of earwax, and the major blood groups. The Negroes also have some of the same local, predominantly African, blood types as the Pymies.
This evidence suggests that the Negroes are not a primary sub-species but rather a product of mixture between invading Caucasoids and Pygmies who lived on the edges of the forest, which at the end of the Pleistocene extended farther north and east than it does now.''Since I'm not one to reject old theories just because they're old, I decided to test this particular idea. I used the San ascertainment panel of the Harvard HGDP dataset, and plotted all African populations, together with West and East Eurasian ones in a PCA plot:
Nor can the results be explained in terms of more recent common ancestry of African farmers with Eurasians in general, because African populations fall in a clear cline towards West Eurasian populations.
While I would hesitate to say that the above results prove the correctness of Coon's theory, they're certainly quite consistent with it. It may very well be that Y-haplogroup E1b1 bearers from East Africa, descended from Y-haplogroup DE-YAP from Eurasia are ultimately responsible for the introduction of the Caucasoid component into Africa.