Two challenges to this doctrine arise from modern science, one fairly old and the other very recent.
I am currently exploring the genetic evidence that is said to rule out an original pair of modern humans. In talking with genetic scientists, I’ve found that there is enormous confusion about this question today. Popularizers have misrepresented the arguments, thereby inviting misguided responses. The issues are very technical and difficult to understand. I’m just beginning to get my feet wet and don’t want to misrepresent the science. I want to know how firm the evidence is and what it would cost intellectually to maintain the traditional view. For example, one scientist estimates that for the entire human race to have originated from an isolated pair 100,000 years ago, the mutation rate would have to be five times what it is observed today. Is that too outlandish to affirm? More.
See also: Geneticist defends possible Adam and Eve in Nature: Ecology and Evolution
Adam, Eve, Richard Buggs, and Dennis Venema: Could Adam and Eve have existed?
Are Adam and Eve genetically possible? The latest: Richard Buggs (yes) replies to Dennis Venema (no)
Adam and Eve and Ann Gauger
Ann Gauger on stacking the deck against Eve