Awhile back I was mulling over a quandary -- the situation of just how fortuitous it was that "evolutionary Eve" and "evolutionary Adam" just happened to evolve at the same time. It would have been too bad for posterity if evolutionary Adam had not evolved at the right time. For example, what if by the time he had evolved evolutionary Eve had already gone through menopause and was too old to bear children? Or what if he had evolved too soon and was unable to produce seed to bear offspring by the time evolutionary Eve came along?
It is extremely fortuitous that this double evolution happened just right not only in this case, but in fact had to happen thousands and thousands of times just right for all the species that multiply by heterosexual procreation.
Or maybe it didn't happen that way at all!