Stephen Oppenheimer, whose book, The Real Eve, inspired me to get once again involved in this sort of research, does in fact see evidence for exactly this sort of event in the eruption of Mt. Toba, which would have precipitated a “nuclear winter” in South Asia that could have been devastating for any humans living in the area:
Even today, a metres-thick ash layer is found throughout the region, and is associated in two Indian locations with Middle and Upper Paleolithic tools. An important prediction of this conjunction of tools and ash is that a deep and wide genetically sterile furrow would have split East from West; India wouldWhile the significance of Toba for the history of modern humans is still being debated (current evidence suggests that HMP didn’t begin its journey until well after the eruption), the genetic evidence unearthed by Oppenheimer does suggest that some sort of equally disastrous event (see previous post), centered in the same area, may well have occurred. I had a fair amount to say about Oppenheimer and his ideas in my “Echoes” essay, but this will be the first occasion I've had to present the genetic evidence he uses to support his scenario. Whether such findings can be related to Toba specifically, or some other, comparable event, is probably beside the point.
eventually recover by recolonization from either side. Such a furrow does exist in the genetic map of Asia, as we shall see (my emphasis -- p. 169).
The first thing Oppenheimer notes is an apparent discrepancy in the distribution of mtDNA haplogroups M and N (which he nicknames “Manju” and “Nasreen”):
The genetic discrepancy is paralleled by morphological and linguistic distinctions:
In West Eurasia there is only Nasreen; in most of East Eurasia [i.e., east of Toba] there are even mixtures of Nasreen and Manju, but on the east coast of India there is nearly all Manju. The latter is consistent with near local extinction following the Toba explosion with recovery only of Manju on the east coast.
In Nepal, Burma and Eastern India we come across the first Mongoloid East Asian faces. These populations generally speak East Asian languages [including tone languages -- VG], contrasting strongly with their neighbors who mostly speak Indo-Aryan or Dravidian languages (my emphasis -- pp. 181-182).Oppenheimer next proceeds to a consideration of the most important of Nasreen’s “daughters,” haplogroup R, which he dubs Rohani:
Turning to evidence from the male line, as found in the Y chromosome, Oppenheimer finds a yawning gap in the distribution of the Y haplogroup referred to as YAP (which he calls “Abel”):
What is perhaps most interesting about the unique Indian flowerings of the Manju and Rohani clans is a hint that they represent a local recovery from the Toba disaster . . . A devastated India could have been recolonized from the west by Rohani types and from the east more by Manju types (183).
A puzzling aspect of the Abel trail is the big gap in his distribution between West Eurasia and the Far East and, notably, his complete absence from India. That he was on the beachcombing trail is evident from the presence of Asian YAP in the Andaman Islands, Cambodia and Japan (my emphasis -- p. 188).While Oppenheimer’s evidence could be considered somewhat out-of-date (his book appeared in 2003), results consistent with the mtDNA discrepancy he highlighted can be seen in a recently published paper, Phylogeographic distribution of mitochondrial DNA macrohaplogroup M in India, by Suvendu Maji, S. Krithika and T.S. Vasulu (2009), where we see a map of haplogroup M distribution very similar to the one displayed on p. 181 of Oppenheimer’s book:
Of the 13 different mainland tribal groups represented in the leftmost map, 10 are located in the Eastern and Southern portions of India and only 3 elsewhere, consistent with the distribution reported by Oppenheimer -- and reflecting, for him, the effects of a devastating ancient event, centered to the East and South of the Indian subcontinent.