Six years ago I wrote a post (Denisovans interbred with Homo erectus) based on an article that suggested that Denisovans had admixed with a "ghost" population that had split from the line that links us and Denisovans, around 1 Millioni years ago. In my post I guessed that this ancestor was no other than Homo erectus.
A very recent paper (see full text: Neanderthal-Denisovan ancestors interbred with a distantly related hominin, Alan R. Rogers, Nathan S. Harris and Alan A. Achenbac. Science Advances 20 Feb 2020:Vol. 6, no. 8, eaay5483 DOI: 10.1126/sciadv.aay5483) came to that same conclusion after some interesting genetic analysis.
The Abstract of this paper says:
"... We show here that hundreds of thousands of years earlier, the ancestors of Neanderthals and Denisovans interbred with their own Eurasian predecessors—members of a "superarchaic" population that separated from other humans about 2 million years ago. The superarchaic population was large, with an effective size between 20 and 50 thousand individuals. We confirm previous findings that (i) Denisovans also interbred with superarchaics, (ii) Neanderthals and Denisovans separated early in the middle Pleistocene, (iii) their ancestors endured a bottleneck of population size, and (iv) the Neanderthal population was large at first but then declined in size. We provide qualified support for the view that (v) Neanderthals interbred with the ancestors of modern humans."
The paper looks into the "large-brained hominins" living in Europe, that made Acheulean stone tools some 600,000 year. It calls them Neanderthal ancestors. They come from the "neandersovan" group, from which Neanderthals and Denisovans descend. And which split from our modern human lineage around 750 kya. The neandersovans left Africa and walked into Eurasia, which was not an empty territory. It had already been colonized some 1.85 Million years ago by other hominins, the "superarchaic" population.
Did they mix?
Yes, they did.
The authors consider that "If superarchaics separated from an African population, then this separation must have preceded the arrival of superarchaics in Eurasia. Nonetheless, our 1.8 to 2.2 Ma interval includes the 1.85 Ma date of the earliest Eurasian archaeological remains at Dmanisi. Thus, superarchaics may descend from the earliest human dispersal into Eurasia, as represented by the Dmanisi fossils. On the other hand, some authors prefer a higher mutation rate of 0.5 × 10−9 per year. Under this clock, the lower end of our confidence interval would be 1.6 Ma ago. Thus, our results are also consistent with the view that superarchaics entered Eurasia after the earliest remains at Dmanisi.".
So depending on the mutation rate adopted, they could have mixed with the descendants of the Dmanisi people from Georgia or from a later group. Dmanisi may be Homo habilis or Homo erectus.
The paper proposes that there were "... only three expansions of humans from Africa into Eurasia: an expansion of early Homo at about 1.9 Ma ago, an expansion of neandersovans at about 700 ka ago, and an expansion of modern humans at about 50 ka ago.". This first expansion led to the superarchaic population in Eurasia that mixed with the second wave of "neandersovans" 700 kya.
The scenario painted in the paper is the following: "Our results indicate that neandersovans interbred with superarchaics early in the middle Pleistocene, shortly after expanding into Eurasia. This is the earliest known admixture between hominin populations. Furthermore, the two populations involved were more distantly related than any pair of human populations previously known to interbreed. According to our estimates, neandersovans and superarchaics had been separate for about 1.2 Ma. Later, when superarchaics exchanged genes with Denisovans, the two populations had been separate even longer. By comparison, the Neanderthals and Denisovans who interbred with modern humans had been separate less than 0.7 Ma.".
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2014 by Austin Whittall ©
