Hi Dennis, Ben, Steve and Chris,
Thank you very much for your kind responses. With regard to the “created diversity” of the original couple: I assume that the authors of the paper would be willing to countenance the possibility that Adam and Eve may have been genetically engineered over a span of millions of years, via intelligently guided mutations occurring in the genes of their hominid ancestors. One could even call that special creation, if one wanted to. The question which interests me is whether the hypothesis of an original pair (however created), each of whom was a genetic chimera, is consistent with the evidence we observe today. From what you’re telling me, it isn’t.
Let’s leave aside the issue of where this original couple lived: there’s enough ambiguity in Genesis 2 to include the possibility that part of the Garden of Eden was in Ethiopia (the land of Cush). That doesn’t interest me so much.
Dennis seems to be arguing that “created diversity” is scientifically ad hoc (I agree, but I don’t think that’s a fatal flaw), and that this hypothesis fails to explain “how present-day diversity could have largely resided in two individuals.” Ben accuses the authors of misunderstanding the role of recombination in generating genetic diversity. Steve points out an error in the paper regarding Y chromosome diversity, and another error relating to waiting times in the hominid line. More tellingly, “chimera” models of Adam and Eve fail to account for the actual pattern of genetic diversity we observe today - in particular, the existence of rare variants. Additionally, human (and chimp) genetic variation appears to be the result of accumulated mutations. Finally, Chris contends that regardless of whether Adam and Eve were real people, they must have shared a common ancestor with other primates (I agree).
So it looks like monogenism (or monogenesis, as some prefer to call it) - i.e. the hypothesis that there was a single original couple from whom all other humans are descended - is ruled out by the scientific evidence. I’d now like to discuss two other hypotheses.
Back in the sixties, it was common for “progressive” Catholic theologians to argue that Adam may have simply been the leader of a small tribe of people, who were willing to abide by his decision regarding the fate of the human race. Hence, “in Adam all sinned.” That suggestion would work if the set of original ancestors numbered less than 100. But if it numbered 5,000, as Steve is suggesting, then it’s far less plausible. However, Steve appeared to hedge his bets in his video, regarding times beyond about one million years ago. Personally, I firmly believe that Neanderthal man and Denisovan man were truly human, as well as their presumed common ancestor (either Heidelberg man or Homo antecessor) but I’m unpersuaded that the smaller-brained Homo erectus was - which would imply that the first human beings must have lived around one million years ago. So my question is: how sure are we that the size of the human population back then was always more than 1,000 (or for that matter, 100)? What’s the lowest it could plausibly have been, in the light of the genetic evidence?
The other hypothesis I’d like to mention is that proposed by Kenneth Kemp: God infused a rational soul into two particular hominids at the beginning, making them truly human, but He refrained from infusing a rational soul into Adam and Eve’s hominid relatives: theologically speaking, they were just beasts. After the Fall, Adam and Eve mated with these beasts, generating the genetic diversity we observe today in humans. Can anyone see any problems with Kemp’s hypothesis?