John McIntyre has written a truly unusual article on the historicity of Adam, in which he argues that the idea that Adam was the biological ancestor of all humans dates to Augustine and not to the scriptures themselves. In it, he notes the same thing that Davis Young observed:
[The traditional] account of Adam and Eve was acceptable until prehistoric humans, Homo sapiens, were discovered by the palaeoanthropologists. Since these creatures lived more than 100,000 years before Adam and across the surface of the earth, they could not biologically inherit Original Sin from an Adam living in Mesopotamia in 4000 BC.
This is a serious stumbling block for the literal interpretation of these passages and has led to more than one theologian surmising that Adam is not historical (I should have citations here. I will try to run down a few).
He makes a somewhat bald assumption, however, when he posits Adam and Eve in the garden at 4000 BC because then, the ages of the patriarchs are taken literally. As noted by Carol Hill, Conrad Hyers and others, the numbering system used in the genealogies is likely base sixty and not literal. Further, he sees no problem taking a literal reading of the primeval history and yet makes no mention of how we should read the accounts of the flood and the Tower of Babel, two stories for which there is not a shred of extra-biblical evidence.
He then takes a left turn and states:
Of course, we could accept the traditional Adam of the Christian church. However, in a remarkable way, the recognition that humans have an evolutionary inheritance clarifies the scriptural account of Adam and Eve.
This is a position I held some years back before (after considerable prayer) I had to abandon it in favor of a less literal reading of scripture and in the face of too many questions that I could not answer. Such a position demands a completely literal reading of scripture and yet tacit acceptance of all of modern science. It is nigh on impossible to reconcile the two.
An interesting take on things.