I think there is zero real evidence for anything resembling a "coastal dispersion". It is a purely mental construct mainly to "explain" very early human presence in Australia and Island SEA.
There is neither archaeological nor genetic continuity along the Indian ocean coast. There is no indication that coastal living was preferable for early HS. Most of relevant archaeological sites in S Asia and Arabia are at a distance from coasts.
What I find also particularly contradicting the "coastal dispersion" theory is that the level of Neanderthal admixture in indigenous coastal people in SA and SEA is statistically very similar to all other Asians. There is no way it would happen if people settled the coast first and then expanded inland northward. It is clear people came to SA from the north first, not from the coast inland.
I am definitely with Petraglia, Dennel, etc. rather than Mellars on this. I think there is ample evidence of presence of early humans in Arabia and SA for a very long time, 400 kY or so. There is no evidence at all that they went completely extinct at any point.
“Coastal route” definitely means different things to different people who have written about it over the years. Some have considered the entire landmass of South Asia as part of a “coastal route”, which in their minds contrasts with the idea that modern humans went into China via the Altai and then southward into island Southeast Asia. Others imagine an almost entirely maritime enterprise, skipping along the coastline in boats the entire way. This is a big area of confusion.
Thanks for this great essay! You really dug into many interesting aspects. It's hard for me to unpack so much quickly. Re Neanderthal gene introgression ... are there longtime indigenous populations in Iran or SE Turkey to check for greater diversity?
Re Denisovan gene introgression ... what are the percentages of Altai vs Elsewhere Denisovan genes in Papuan and Philippine peoples? What about Andaman Islanders?
IIRC, there were models for AMH uniparental phylogenetic dispersion routes into East Asia that differed for the Y chromosome vs mitogenplateau. One was suggested to have come up from SE Asia, the other more likely came over/around the Tibetan/Qinghai plareau. Is there a consensus now for those?
I think the answer to your first question is that the Upper Paleolithic population of Iran has been written over by Neolithic and later population growth to a greater extent than in southern India. I'll be looking closely at the genetics of this area in an upcoming post.
The data don't say definitively that there's zero Altai Denisovan component in genomes from Philippines or Papua, but the value is certainly extremely low. The unique components in these genomes (which have much more Denisovan ancestry than any mainland Asian groups) do overlap with the non-Altai portion of Denisovan introgression in India, but there is a lot of non-overlap also. I think these are multiple Denisovan populations, all very separated. Working out the unique Denisovan component of these genomes from India would be a really good dissertation for somebody.
Onge (Andaman Islands) genomes are seen in this paper as very close to southern India, including Denisovan mixture.
Re: dispersal routes: No consensus. None of these have ever shown particularly good correspondence with archaeological thinking, both geneticists and archaeologists have basically circled around issues of disconnect.
Very informative, as usual!
I think there is zero real evidence for anything resembling a "coastal dispersion". It is a purely mental construct mainly to "explain" very early human presence in Australia and Island SEA.
There is neither archaeological nor genetic continuity along the Indian ocean coast. There is no indication that coastal living was preferable for early HS. Most of relevant archaeological sites in S Asia and Arabia are at a distance from coasts.
What I find also particularly contradicting the "coastal dispersion" theory is that the level of Neanderthal admixture in indigenous coastal people in SA and SEA is statistically very similar to all other Asians. There is no way it would happen if people settled the coast first and then expanded inland northward. It is clear people came to SA from the north first, not from the coast inland.
I am definitely with Petraglia, Dennel, etc. rather than Mellars on this. I think there is ample evidence of presence of early humans in Arabia and SA for a very long time, 400 kY or so. There is no evidence at all that they went completely extinct at any point.
“Coastal route” definitely means different things to different people who have written about it over the years. Some have considered the entire landmass of South Asia as part of a “coastal route”, which in their minds contrasts with the idea that modern humans went into China via the Altai and then southward into island Southeast Asia. Others imagine an almost entirely maritime enterprise, skipping along the coastline in boats the entire way. This is a big area of confusion.
Thanks for your rapid and substantial response! I'm looking eagerly for your upcoming post.
Geneticists and archeologists just warily circling points of disconnect? Not for the first time ... ;)
Thanks for this great essay! You really dug into many interesting aspects. It's hard for me to unpack so much quickly. Re Neanderthal gene introgression ... are there longtime indigenous populations in Iran or SE Turkey to check for greater diversity?
Re Denisovan gene introgression ... what are the percentages of Altai vs Elsewhere Denisovan genes in Papuan and Philippine peoples? What about Andaman Islanders?
IIRC, there were models for AMH uniparental phylogenetic dispersion routes into East Asia that differed for the Y chromosome vs mitogenplateau. One was suggested to have come up from SE Asia, the other more likely came over/around the Tibetan/Qinghai plareau. Is there a consensus now for those?
I think the answer to your first question is that the Upper Paleolithic population of Iran has been written over by Neolithic and later population growth to a greater extent than in southern India. I'll be looking closely at the genetics of this area in an upcoming post.
The data don't say definitively that there's zero Altai Denisovan component in genomes from Philippines or Papua, but the value is certainly extremely low. The unique components in these genomes (which have much more Denisovan ancestry than any mainland Asian groups) do overlap with the non-Altai portion of Denisovan introgression in India, but there is a lot of non-overlap also. I think these are multiple Denisovan populations, all very separated. Working out the unique Denisovan component of these genomes from India would be a really good dissertation for somebody.
Onge (Andaman Islands) genomes are seen in this paper as very close to southern India, including Denisovan mixture.
Re: dispersal routes: No consensus. None of these have ever shown particularly good correspondence with archaeological thinking, both geneticists and archaeologists have basically circled around issues of disconnect.
Edit: mitogenome, not mitogenplateau. I have fat fingers!