Abstract
Previous research favours the idea that modern humans spread worldwide from Africa. For instance, through autosomal diversity, an area of origin for this worldwide expansion is indicated to entirely be within Africa. It remained to be seen if this indication happens for certain variables such as Y-chromosomal diversity. There is disagreement regarding where in Africa the origin is. Support for a region could reflect non-African ancestry rather than the expansion. The present research considered whether some genetic and cranial variables indicate the expansion, and, furthermore, where in Africa the expansion started. Variables included, for example, autosomal diversity (in sub-Saharan Africa) which was adjusted for non-African ancestry, Y-chromosomal diversity, and cranial sexual size dimorphism. For each, it was seen if the estimated area of origin was solely in Africa. Moreover, to generally estimate the origin, a centroid was calculated from potential origins which were obtained in the present, and past, research. The area of origin was completely within Africa for each variable except one – for Y-chromosomal diversity, the area was possibly in Asia only. The centroid of the potential origins was in southern Africa. The autosomal diversity of sub-Saharan African populations, adjusted for non-African ancestry, indicated a southern African origin. This adjusted diversity appeared to start declining from about 2,000-3,000 km away from the origin; the non-linearity may be explained by travels after the expansion, or the expansion entering locations in Africa which were already populated, to differing extents, by modern humans. Southern Africa is perhaps where the expansion began.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Above all, added a bit more on Y-chromosomal diversity. Also, now referring to Chiaroni et al. (2009) as using Y-chromosomal haplogroup diversity (whereas, before, I referred to haplotype diversity).
16 The intention was to list, in column two, only research which included a p-value (with respect to distance from Africa having an association with a variable). The author of the present research thought such a p-value was given in Tishkoff et al. (2009), but, upon looking through Tishkoff et al. (2009) again, may have been mistaken. So, criteria regarding column two was changed – research concerning a fall/rise in a variable as distance from Africa ascends did not have to include a p-value.
19 To clarify, Tishkoff et al. (2009) did find their peak point (autosomal microsatellite repeat length diversity) to be around the Angola/Namibia border – in the vicinity of the seaboard.
