The discussion in a comment thread has been phenomenal. One key line of evidence against @glipsnort’s conclusions is worth clarifying.
What @John_Harshman is propounding is the evidence of trans-species variation. This is a legitimate line of evidence that most scientists think rules out a bottleneck of 2 anytime between 6 million years ago and present day. This comes from a paper in in the 1990s by Ayala, and it is the most common evidence cited by scientists against a bottleneck of 2 individuals.
In my view this a valid line of evidence that must be addressed by @glipsnort. He, also, has to come to a far stronger conclusion than mine on this matter, so I do not know if his conclusion will stand.
WLC and I have dealt with this in a particular way.
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I presented evidence (which WLC explains in his new book) which substantially weakens the argument based on this line of reasoning. But I cannot fully dispatch it.
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WLC makes clear that he is thinks there is a larger population of reproductively compatible individuals that may have interbred with Adam and Eve’s lineage.
In my presentations of this work, I am sure to point out both these points. The first is point is important, but the second point renders this line of evidence moot. WLC is not working within BioLogos’s genetic-sole progenitor model of human origins.
In @glipsnort’s case, he should certainly rely heavily on and cite the evidence I offered in #1. However, the escape hatch of #2 is not available to him. He has been excruciatingly clear that by “sole-genetic progenitor” he means to exclude any interbreeding between Adam and Eve’s lineage at all. So when he concludes that the evidence does not rule out a bottleneck couple more ancient than 500,000 years ago, he is making a far stronger conclusion that WLC or I.
Maybe he is right. Demonstrating his case here with @John_Harshman would add significantly to the discussion. @glipsnort is also well equipped and situated to do the requisite genetic analysis to put this argument fully to rest. So I very much look forward to his response hearing his take on trans species variation.
Of course, even if @glipsnort does not make his case, WLC and I have #2 as an escape hatch. We are not working within the confines of @glipsnort’s genetic bottleneck paradigm. Either way, our claims are safe.