Quote:
Originally Posted by
Ygorcs
Wait, I'm confused. So is a largely Basal Eurasian individual part of the same cluster as Dzuduzana2 and sharing more drift with WHG/Villabruna cluster than with any other Paleolithic DNA sample? So weren't Basal Eurasians as divergent and drifted apart from the Common West Eurasian derived branches than was previously thought? Or are we instead seeing just a BE-admixed but still mostly CWE-derived individual?
Its the latter. There is no exact percentage, so what "substantial" means is up to every reader I guess. They won't come up with a too exact estimation anyway, because the resolution seems to be to bad and unreliable, which is why they have troubles making an exact estimate of Neandertal ancestry either.
Quote:
Didn't a recent paper find evidences of a much earlier, more basal Eurasian back-migration to Africa with signals of that gene flow spanning even most of Sub-Saharan Africa? What if those weren't really Eurasians (not mostly anyway), but just a consequence of the fact that the specific Proto-non-African population that colonized all the other continents didn't disappear from Africa as early as was thought, and some of it stayed behind in their original "homeland" in Northeast Asia and the nearest Asian neighborhood (i.e. Arabia and Southern Levant)? Just some thoughts...
Actually the geography is not as important as the position on the tree. Like North Africans are closer to Europeans even though "they live in Africa" than anything East of the Altai. So its not about where they were or are sitting, but what characteristics they had. ANA is likely either a back migration, or a more recent expansion from the North East of Africa. Either way, its a close branch to all Eurasians. Basal Eurasian is simply the next branching event, surely geographically even closer, but whether that means Sinai-Egypt, Sinai-Southern Levante, Southern Levante-Arabia or everything together, nobody really knows. Unless they already have better samples which being not published yet, then the scientists involved might know, but the rest of us not, nobody else.
Quote:
I tended to believe before this that even a moderate increase in the proportion of BE ancestry would bring an individual much further from another with lower BE admixture, roughly as it happens when there is admixture between two very divergent population clusters, like West African vs. European. But that doesn't seem to be the case here, so weren't Basal Eurasians very different from other West Eurasians to begin with?
No, they were not. The biggest and probably only difference is that they main Eurasians had (more) archaic admixture, mainly Neandertal, in the East and South East also Denisovan, while Basal Eurasian had not (as much). So Basal Eurasians are more like the pure modern Homo sapiens branch. There is nothing else. Like the ancestors of Australo-Melanesians moved on, after leaving Africa, to the South East. So there was not even a common evolutionary path for the rest of the main Eurasians. The only thing which made them different from Basal Eurasian is, that Basal Eurasian was restricted to the Near East, possibly North East Africa, and had no(t as much) archaic admixture. That's it, period.
Quote:
Or is it just that the "significant" BE admixture in this new sample is actually not much higher than in Dzudzuana, therefore even lower than what you could find in later populations like Iran_N, CHG, Anatolia_N and Natufian (correct me if I'm wrong, but Anatolia_N was basically modelled by Lazaridis as Dzudzuana + extra BE)?
The resolution and quality of the sample might be questionable and there is no other information than "substantial". I would say 25 percent is substantial. So whatever the exact percentage, what this proves is the early, widespread presence of BEA, nothing else.
Quote:
On a related note, I wonder if between the early LGM and the Mesolithic there was a consistent east-to-west trend: Iran_Meso/CHG-like people, a mix of ANE, Dzudzuana-like and maybe a bit more BE, migrated from Iran to the Caucasus and nearby areas; the former Dzudzuana-like people that lived there migrated westward towards Anatolia; and the WHG-like people that lived in Western Anatolia and Southeasternmost Europe migrated (north)westward into the rest of Europe. We'll see if that scenario holds true when more Paleolithic DNA from Eurasia appear.
Like I wrote before, ANE were the large bodied steppe mammoth hunters, either because the climate became to hostile and cold, or the megafauna was depleted, or they had a demographic growth, whatever was the reason, probably all of this together, they began to push South and West, on a grand scale. And they chased away whoever was in their way or mixed with those. So at the LGM you had one big chain migration event, caused by the climate and the migration of ANE, in West Eurasia Africa. Even Iberomaurusians fit into this, because one group had to push the next. And that is where modern Subsaharan ancestry (and the Negroid phenotype) began to emerge, because ANE pushed Dzudzuana, those pushed their Basal Eurasian neighbours and created a mix, this mixed Levantine group pushed into Africa and spread IBM. The ANA lake dwellers too began to move South, and began to mix with Basal H.s. and archaic groups (Iwo Eleru) in Africa.
The same pattern repeated itself numerous times, it did so with Natufian like expansions into Africa, with the developed Neolithic, and the beginning metal Ages. And with every push from the North the movement of culturally more developed people penetrated more of Africa. In the end this created the Bantu expansion as well. Its right, Basal Eurasian mixed in from the South and when ANE entered the scene, they pushed the whole range of the variation from the Near East down to Africa, so that a lot of the lineages ended up much more South than they orginally were.
Now where they were originally, like E or E1b, we don't know, we can't know. Because if the result of the push was that whole communities were on the move, the present distribution won't prove the past one. Only ancient DNA can.