They then move to a consideration of the distribution of mtDNA haplogroups M and U, which "has been taken as a genetic signature for an 'early' (i.e., Middle Paleolithic) colonization of South Asia by modern humans and, consequently, as a confirmation of the 'southern route' hypothesis." They dispute this evidence as well, first on archaeological grounds, since "the earliest evidence of modern human industries and remains is dated to ∼30,000 years," then on the basis of the genetic evidence. For example:
- Alu insertions data are interpreted as supporting an ancient African-PNG relationship, but India is not a part of this relationship (Stoneking et al. 1997).
- Y-chromosome and mtDNA data suggest a connection between the Indian subcontinent and Australia, which is, however, dated to less than 5,000 years ago.
- mtDNA haplotypes in South Asian ethnic groups are most closely related to east Eurasians and do not show any particular ties to African or PNG populations (Kivisild et al. 2003; Cordaux et al. 2003).
- An mtDNA control region motif proposed by Forster et al. (2001) to represent a signature of an early migration from Africa to Sahul through the southern route is not found in South Asia (Cordaux et al. 2003).
[A]lthough they show close affinities, the east Asian and Indian mtDNA gene pools are fairly distinct. This result is consistent with the suggestion that the east Asian and Indian mtDNA pools have been separated from each other for about 30,000 years (Mitochondrial DNA analysis reveals diverse histories of tribal populations from India).
On the basis of the mtDNA and Y-chromosome data presented here, we see no need to accept the view of Cordaux and Stoneking regarding the settlement of South Asia. . . We must infer an early dispersal of AMH with non–Upper Paleolithic technology through Asia to explain the early Australian [archaeological] evidence (Stringer 2000), although we agree with Cordaux and Stoneking that the precise route(s) taken is still unclear (Stringer 2002). But we see no requirement for the South Asian mtDNA gene pool to demonstrate close affinities with either PNG or Africa to discuss an early settlement of this region. Given the continuity of the archeological record within India, from the Middle Paleolithic onward, and the range of estimated dates for Indian haplogroup M, there is no clear reason to preclude the presence of modern humans in this region prior to 30,000 years ago.The debate could be summarized as follows: on the one hand, the genetic evidence reveals a gap between Africa and the Sahul, and a disconnect between South Asia and East Asia, both inconsistent with the theory that early Africans migrated through Asia via a southern route; on the other hand, since archaeological evidence from Australia clearly implies a middle Paleolithic migration from Africa to the Sahul, and the genetic evidence is clearly inconsistent with a northern route, a southern route would seem the only logical possibility -- for Endicott et al, genetic evidence of discontinuity along this route is unclear and open to dispute.
Our results indicate that the frequency distribution of haplogroup M varies across different Indian regions by a significant cline towards the south and the east . . .
The very interesting distributions of some of the most important M haplogroups are mapped in Figure 1 (click on the figure to enlarge it):
I'll have a lot to say about these maps, and what they tell us, in the next installment.