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Wednesday, July 2, 2008

What if... Y-DNA K diversified after Toba?

Karafet 2008 dates some haplogroups on the assumption that age(CT)=70,000 BP, following the rapid coastal migration hypothesis.

Largely inspired by Petraglia 2007, who strongly suggests continuity in the Paleolithic of India before and after the Toba ash layer, I dare make a different assumption: age(K)=72,000 BP (after the Toba catastrophe), to see how he corresponding estimates would vary, I must then add 52% to all of Karafet's ages.


CT 106.4 KY
> CF 104.7 KY
> DE 98.8 KY
>> E 79.8 KY

>>>>> E1b1 72.2 KY

>> F 73 KY

>>> IJ 58.5 KY

>>>> I 33.7 KY

>>> K 72 KY (assumed)

>>>> P 51.7 KY

>>>>> R 40.7 KY

>>>>>> R1 28.2 KY


CF would then have diversified in South Asia, right in time for the earliest known blade tools of the subcontinent (c. 103,000 BP)

Not just K but also its immediate ancestor, macro-haplogroup F, would have diversified right after the Toba event, which would have been followed, as per my hypothesis, by a rapid expansion out of South Asia.

P diversified (into the precursors of Q and R) in Central Asia (as it's normally acknowledged) and the date of c. 52,000 BP fits reasonably well with the TL dates for sites in Altai. Probably R remained in the south of Central Asia, while Q went to the NE (Altai?).

R diversified (into the precursors of R1 and R2) c. 41,000 BP (according to this model), and could even have taken part (as pre-R1) in the Aurignacian colonization of Europe. This is a risky assumption but certainly Central Asian, Iranian and Anatolian sites have been claimed as proto-Aurignacian.

The estimate for R1 of c. 28,000 BP fits just too well with Gravettian. If so pre-R1b would have headed west and pre-R1a eastwards. Karafet does not provide age estimates for the succesive nodes in this branch though.

What about I? IJ would seem to have diversified c. 58,000 BP, and that surely happened in West Asia. But I is mostly a European clade, what implies some sort of founder effect. The estimate for the divergence of the I node (into the precursors of I1 and I2) of c. 33,000 BP is no good date: too late to be Aurignacian and too early for Gravettian possibly.

As with IJ, I have no clear what to say about E, just that E1b1 (its main subclade and the most important African haplogroup), if the c. 72,000 BP age is correct, would also seem to have benefitted from whatever niche-opening effects the Toba event had in Africa.

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