The Eurasians before us all

Razib alerts us to Alan R. Rogers, Nathan S. Harris and Alan A. Achenbach: "Neanderthal-Denisovan ancestors interbred with a distantly related hominin".

R-H-A get a little loose with some of their dates toward the end. Their conclusion collapses the main story to 700 thousand years ago. But they have the "Neander'sovan" ancestors breaking into its Neander and Denisovan tribes 735 BC. It could be that they are insecure about the precision of their dates; they did have to revise an earlier paper they'd submitted. So I'll try again here.

Para-humans about two million years back colonised Eurasia - probably from Africa. Another wave exited Africa ~750 thousand years ago. The group did not at first do well outside their home; their lineage shows a bottleneck of only about five hundred souls. They did however interbreed with these para-humans, adopting some hybrids for their own. That hybridisation seems to have helped, as the "Neander'sovans" expanded, becoming two groups: Neanders and Denisovans. By the "Marine Isotope Stage 13" interglacial 522-472 kBC, the Neanders at least numbered 16000, maintaining that level to 453 kBC.

The para-humans did not all die out at once; some survived out East, and interbred again with the Denisovans (I'm not clear on which Denisovans; they'd split too, famously). Meanwhile out west the Neander population dwindled to 3400 people.

Maybe less, from our perspective: R-H-A note (from Kay Prüfer et al. 2017) that a tribe in Vindija is the one which contributed to our DNA where another group at the Altai did not. The African exodus during the Eemian affected mainly Vindija. Chen, Wolf, Fu, Li, and Akey doi 10.1016/j.cell.2020.01.012 called this the "introgressing" subset, as opposed to the Altai Neanders who never touched us. But Vindija and the others seem not far apart at this time.

I don't know what hit the Neanders in the middle 400s kBC. They'd already survived some cold patches. Freakin' Yellowstone blew 630 kBC and that's not even on the map here (like Toba). Were the 400s kBC Neanders and Denisovans between them too successful - did they thin down too much of the accustomed game? But then we'd have to ask what was special about the 400s over the 600-500s.