It was one of my scenarii (Y-G and Y-H) but I avow I based it on nothing factual, unless te fact that Y-E and Y-J din't seem to me the BE bearers! BTW I don't know the %'s of BE among South Asians, and as said Angela, this componant could be transmitted rather by women... Concerning the almost necessary refugium I have no precise idea.
We can't say where the original centre was, but we can say where they had to be about 30.000 years ago. They had to be in the Levante and especially Southern Arabia. Now I'd say they were there all the time. Concerning haplogroups, original Afro-Asiatics were with more than 90 percent probability E1b1b, yet some Semitic groups now have very little of that haplogroup and in some regions the percentages changed very recently. And now look where E1b1b was probably dominant for a pretty long time again, it seems to me Southern Arabia again.
So whereever the ultimate origin was, the Southern Levante and Southern Arabia was very early heavily Basal Eurasian, it must have been, there is no logical way around that. Now some studies placed it there, originally, others looked for the Sinai or Egypt, but that's the direction, that is where we have to search for it. South Asia was no source, it was for the most time a sink. Its like searching for the origin of East Asians (Mongoloid) in South East Asia. No, won't work out.
To me already the pre-Natufian Near Easterners show the same trend, going in a Proto-Mediterranean direction and they lived South of the zone which demanded a stronger climatic adaptation in the LGM. Those above grew larger and more robust, that was the core West Eurasian population and I guess we will find within later pre-Dzudzuana-like populations all the GHIJ-haplogroups of the core, which was further altered and polished by QR-ANE and E-Basal Eurasian and together, after the fusion, modern Western Eurasian were formed. Today all West Eurasians (Caucasoid) have both ANE and BEA ancestral components because of that.
South Asians on the other hand go in a completely different directions, yet they are the Southern link to the East, but not much closer than East Asians, rather the link to Australo-Melanesia. That was always the most likely scenario, and modern genetics just proved it. There is no way you can place AASI in a tree with BEA, its impossible. AASI was core Eurasian, with increased Neandertal admixture, and they even picked up additional Denisovan. Actually its even possible they had admixture from a third unknown archaic population, but that's more kind of a definition, because whats "Denisovan" to begin with, how do you define it, if it was very old and widespread over most of Asia? So let's say they had Denisovan, probably a specific regional variant of it, not shared by East Asians probably and unknown whether it was shared with more Eastern Negritos or Australo-Melanesians.
These statistics test the hypothesis of an equal rate of derived allele sharing of East Asians and X with Africans. Mondal et al. also report statistics with a European population in place of East Asians, but it is already known that Asian populations have a greater amount of Neandertal ancestry than Europeans
Why is that so? Also because of Basal Eurasian.
Because the main if not only important distinction of BEA and main Eurasian is actually the reduced amount of archaic introgression. There is no other important one, certainly no phenotypical beside that, considering
the timing of the original split.
In the study they quote Mondial's findings:
Mondal et al.?s new claim of more archaic ancestry in South Asian populations than in East Asians. In Mondal et al.?s computation, these statistics are negative when X is any Indian group or Andamanese, a result they interpret as evidence of more archaic ancestry than in East Asians. As they find no evidence of excess allele sharing with Neanderthals or Denisovans, they argue that the contribution is from an unsampled archaic lineage.
They didn't replicate that in the study I'm quoting from:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6433599/
But if anything, South Asians have more archaic introgression than Europeans, not less!
South Asia is both by uniparentals, as well as autosomally, archaeologically and biogeographically completely out of question as the BEA homeland. One can't look at the data and claim that seriously, its impossible.
However, there is no way the bridge between the Caucasus and North Africa was not Basal Eurasian, that on the other is not completely but almost impossible too. The Levante-Arabia-Sinai-Egypt must be in the focus therefore. And like I said, there is a great deal of physical and cultural continuity in the Near East and Levante, with occasional contacts, but no replacement towards Eurasia, to the Sinai-Egypt. And how quickly haplogroups could spread and replace pre-existing variation in quick sweeps, by founder effects, economical advantages, natural catastrophies and genocidal activities, should be obvious by now. Usually in some of the core source regions from which explansions started the diversity actually decreased, because one founder population replaced them all.
I don't think that places like Yemen had the same haplogroup frequencies 40.000, 25.000, 10.000 or even 4.000 years ago. Not at all. This needs to be investigated and will be quite illuminating. Because Basal Eurasians needs to have been very close to main Eurasian, but still with a natural barrier at a distance. The ideal scenario is indeed Southern Levante-Arabia or Sinai-Egypt for that. I would be extremely surprised if its any other place. And I would be similarly suprised if it wasn't haplogroup E, because if it would have been one of the main core West Eurasian lineages out of the GHIJ group, how's that supposed to have happened?
What was the core West Eurasian group then? The splits and timings are even worse than otherwise. But that's more open to debate, I know.