The Biologos forum has been discussing Adam and Eve. The discussion is framed as a question of whether they are historical or literary figures, and, if historical, how their existence can be brought into harmony with the theory of evolution. It’s not obvious that the initial division (historical/literary) is a good one- how does one apply it to, say, the Johnny Depp title character in Donnie Brasco, the “Jim Garrison” character in Oliver Stone’s JFK or, more classically, to Robin Hood or the Sheriff of Nottingham? The division of historical and literary is pretty clearly inadequate here. One might suspect that, for similar reasons, the pre-Abrahamic Book of Genesis is a paradigm case of when this division is inadequate (the Catholic teaching on Genesis of the last 100 years or so, for example, presupposes that this division is inadequate.)
But leave all that aside. The real problem is that the Biologos essay is indecisive and scattershot. This is why PZ Myers and Jerry Coyne smell blood, and fire away at the essay in their characteristic style (follow the links here. I’m not linking to those guys). Any success that PZ and Jerry might have is due to this: we are very prone to assume toubling and problematic assumptions into our discussion of Adam and Eve, and these assumptions need to be pointed out in the beginning, or our whole discourse will either be an expression of our own indecisiveness and confusion, or the false triumphalism of killing strawmen.
First, belief in a historical Adam and Eve is a belief in monogenism. Monogenism states that all human beings from some point in the past until now descend from a single set of parents (The literal truth of Genesis would probably require that this point in the past go back at least to Abraham, say 2100-1800 BC). It is helpful to contrast monogenism to different claims that make more assumptions, like
1.) We descend from one set of parents, and we have no other parents. In other words, when Adam and Eve existed, they were the only human beings on earth. This commits us to more than is required for monogenism. One can argue, of course, that the Genesis account requires this addition, but it must be recognized as an addition. Note carefully that the special creation of Adam by God does not require that he be the only man who existed at the time, any more than the special creation of Christ requires that Christ be the only man who existed at the time. Scripture relates any number of miracles where God does something that is also done by natural processes, but by using other means (e.g. making non-living things alive, making water into wine, etc.)
2.) We descend from some first man who has had a male descendant in every generation. This is the definition of the “Y-Chromosome Adam“, and (adjusting for sex) the “mitochondrial Eve”. Assume that Adam’s daughter went off, east of Eden, and married some human outside of her family. Then Adam could not be a “Y- Chromosome Adam” for that line of persons, though he is clearly responsible for the line. All that would be required for the “literal” truth of Genesis is that at some point in time, all lines not descended from Adam either died off or merged with him. Given that we know as a fact that this has happened for at least one man, who also exists under the additional stipulation of having only male descendants, there is nothing odd whatsoever in assuming the far more possible case of a man being the parent of the whole human race who did not exist under this restriction.