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NetNomad
12-30-2018, 07:07 AM
What to make of this study?

Carriers of mitochondrial DNA macrohaplogroup L3 basal lineages migrated back to Africa from Asia around 70,000 years ago
by Vicente M. Cabrera (corresponding author), Patricia Marrero, Khaled K. Abu-Amero, and Jose M. Larruga

Abstract
Background
The main unequivocal conclusion after three decades of phylogeographic mtDNA studies is the African origin of all extant modern humans. In addition, a southern coastal route has been argued for to explain the Eurasian colonization of these African pioneers. Based on the age of macrohaplogroup L3, from which all maternal Eurasian and the majority of African lineages originated, the out-of-Africa event has been dated around 60-70 kya. On the opposite side, we have proposed a northern route through Central Asia across the Levant for that expansion and, consistent with the fossil record, we have dated it around 125 kya. To help bridge differences between the molecular and fossil record ages, in this article we assess the possibility that mtDNA macrohaplogroup L3 matured in Eurasia and returned to Africa as basal L3 lineages around 70 kya.

Results
The coalescence ages of all Eurasian (M,N) and African (L3 ) lineages, both around 71 kya, are not significantly different. The oldest M and N Eurasian clades are found in southeastern Asia instead near of Africa as expected by the southern route hypothesis. The split of the Y-chromosome composite DE haplogroup is very similar to the age of mtDNA L3. An Eurasian origin and back migration to Africa has been proposed for the African Y-chromosome haplogroup E. Inside Africa, frequency distributions of maternal L3 and paternal E lineages are positively correlated. This correlation is not fully explained by geographic or ethnic affinities. This correlation rather seems to be the result of a joint and global replacement of the old autochthonous male and female African lineages by the new Eurasian incomers.

Conclusions
These results are congruent with a model proposing an out-of-Africa migration into Asia, following a northern route, of early anatomically modern humans carrying pre-L3 mtDNA lineages around 125 kya, subsequent diversification of pre-L3 into the basal lineages of L3, a return to Africa of Eurasian fully modern humans around 70 kya carrying the basal L3 lineages and the subsequent diversification of Eurasian-remaining L3 lineages into the M and N lineages in the outside-of-Africa context, and a second Eurasian global expansion by 60 kya, most probably, out of southeast Asia. Climatic conditions and the presence of Neanderthals and other hominins might have played significant roles in these human movements. Moreover, recent studies based on ancient DNA and whole-genome sequencing are also compatible with this hypothesis.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6009813/bin/12862_2018_1211_Fig1_HTML.jpgFig. 1
Geographic origin and dispersion of mtDNA L haplogroups: a Sequential expansion of L haplogroups inside Africa and exit of the L3 precursor to Eurasia. b Return to Africa and expansion to Asia of basal L3 lineages with subsequent differentiation in both continents. The geographic ranges of Neanderthals, Denisovans and Erectus are estimates only

Full paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6009813/

NetNomad
01-03-2019, 03:20 AM
Any comments?

Megalophias
01-03-2019, 03:44 AM
:noidea: With events that long ago who the heck knows. Seems to me like lower TMRCAs further west could be due to average colder and drier conditions hence lower long-term population sizes, though that wouldn't apply to South Asia.

parasar
01-03-2019, 04:03 AM
Ancient DNA can perhaps provide some resolution.
On the Y side my thinking has been that M168 is Eurasian.
The general scenario supposes it to be African:
https://upload.wikimedia.org/wikipedia/commons/3/3d/Y-DNA_tree.GIF

Mandoos
01-03-2019, 04:26 AM
:noidea: With events that long ago who the heck knows. Seems to me like lower TMRCAs further west could be due to average colder and drier conditions hence lower long-term population sizes, though that wouldn't apply to South Asia.

south Asia was also relatively dry/inhabitable following the Toba catastrophe by the time L3 might have arrived there.

GailT
01-04-2019, 04:06 PM
Any comments?

In my opinion, this paper is pure speculative nonsense. The age estimates are wrong, and the diversity of L3 in Africa clearly indicates an African origin of L3. It is an extraordinary and wildly improbable claim with no evidence to support it.

parasar
01-04-2019, 04:17 PM
south Asia was also relatively dry/inhabitable following the Toba catastrophe by the time L3 might have arrived there.

That is why we are seeing N and M and Y lines radiate out of SE Asia. My thinking would be that the radiation is from regions east of Toba where YTT had less of an effect.

In South Africa:
Modern humans flourished through ancient supervolcano eruption 74,000 years ago
https://www.sciencedaily.com/releases/2018/03/180312132956.htm