@Swamidass, you are correct that I am trying to understand how the genetics, population genetics, and paleoanthropology evidence fit together best if we start from the assumption of a first pair. This is, after all, a position that hasn’t been tested, but needs to be. There are a lot of people invested in it.
In order to insure that later lineages (Neanderthals, Denisovans and H Sapiens: N, D, and H) that show signs of having interbred, and knowing that N and D are believed to share common ancestry with H erectus _and that_H erectus migrated into Asia very rapidly and very early on (about 1.8 mya? I don’t know current estimates
), I chose to view H. erectus as the original pair. @Swamidass
is right, though, my goal is to find the best explanation for all
the data. The date 700 kya fits much of it, but I don’t think it does for the (easily forgotten) Denisovans.
I really don’t like the idea of interbreeding between N and H or D and H if they are far distant on the tree, and do not share the same nature (I mean that in a theological sense). I do not want any people now to have more or less share of the genetics of the first pair, where ever that first pair was in time. Sole progenitorship? You can call it that. The main concern is to be sure that we all come from the same stock.
2 mya, 1 mya, 7mya, 400 kya, 200 kya or smaller–if it fits the data best, any of those dates are OK. To be explained: time of origin: ancestry and ability to interbreed, morphology, cultural and technological artifacts, dispersal, population size and local origin, population genetics, and genetics, with the assumption of a first pair.
The last two categories of data are most important because they provide a historical record in a way that the others cannot. As anyone can see, the data are in tension with one another. It depends on which factors one emphasizes as to where one comes down on the time line as most likely. Or one can throw up one’s hands and discard a first pair, or find a solution that does not involve sole progenitorship, or some other solution I haven’t thought of.
BTW, my thanks to Buggs, Venema, Swamidass and Schaffner for a fine discussion. I have kept silent most of the time, but have observed. It has been worthwhile.