Please do. Let’s get the evidence straight.
As far as i know, we cannot find the entire Neandertal genome in human variation, just a small portion of it. Neither can we find the entire Denisovan genome in human variation either, just a tiny fraction of it. That means we do not expect any specific portion of the Denisovan genome, e.g. that tiny portion which was inherited possibly from an ancient hominin, to be in human variation. As far as I can tell, that portion of the genome is not found in extant humans.
Moreover, it only seems that a portion of the Homo sapien genome (i.e. loci) shows signs of interbreeding. Is that not correct?
If I misunderstand that status of the evidence. If I do, by all means please correct me. It is important to get this straight.
I do not know if the sole-genetic progenitor model specifies what happens to “humans” that do not ultimately contribute to extant humans. There are several shades of gray…
- Are genealogical ancestors that are not genetic ancestors allowed to descend from other lines?
- Are descendents of Adam and Eve that do not become ancestors of extant humans allowed to interbreed? (e.g. as put forth in all AIG models because of Nephilim)
- And as we have already covered, is interbreeding that contributes to extant humans allowed? (e.g. genealogical Adams)
Unless we can show that the variation from a 1 mya hominin appears in extant humans, and this is not incomplete sorting, then #2 and #1 are live possibilities. It would mean that there could be a bottleneck of a single couple in our lineage. Keep in mind also that we have no idea if that specific Denisovan was in our lineage or not. All we know is that there some fragments of human variation that seems to match that knuckle. As far as I can tell, there are severals ways this could have happened, not all of which would rule out sole-genetic progentiorship within the last 700 kya.
Of course, please do correct me if I am wrong or missed something important here.
True, and that is why I’ve pointed out 700 kya as a date that might stand the test of time, and also 2 mya. Conversely, 500 kya might ultimately be too early, even if we cannot definitively rule it out at this point.
As for what ultimately happened, and what the evidence will ultimately show, we can make guesses and take bets, but we should start by explaining honestly what the data shows us right now.
Of course it is also possible I misunderstood something in the introgression data (see above). Please do correct me if that is the case.