The Case for Adam & Eve as a Group of Ancient Ancestors
(A scenario of Evolutionary Creationism)

In this variation, somewhere around the time of the population bottleneck in human history, God revealed himself in a single event to a group of humans, and they fell into sin. The Adam and Eve story in Genesis 2-3 is symbolic of what happened to this larger group. We are all descendants of this group.

Proponents of the variation argue that this group, even if it is not a single pair, at least constitutes the sole ancestors of humanity. This avoids the theological difficulties raised by the representative scenarios in which humanity has ancestors besides those who received the first revelation.

This view is consistent with most of the fossil and genetic evidence, including some of the genetic diversity of humans today. God could have used the mechanisms of evolution to bring about this group of humans and then spiritually transformed them via his revelation, or he could have performed some degree of physical and genetic transformation on this group at the same time.

But this variation doesn’t eliminate all difficulties. The genetic evidence for the population bottleneck in human ancestors indicates that the bottleneck was probably 10,000 individuals or more, a far larger population that could have been living together in one place a time when humans lived in much smaller hunter/gatherer bands. If God had revealed himself to this many individuals at once, this would have had to happen to many different small groups at the same time. In terms of genetics the size of this group of ancestors could in principle be reduced to about 75 individuals, a small enough number that God’s revelation could have happened to a single group. This number is just large enough to account for the genetic diversity in the human population today without the need for God to have performed miracles in subsequent generations. This number assumes that when God transformed this group from hominids into the first true humans he created all of the necessary genetic diversity in it and then ensured that this group had enough descendant to maintain that level of genetic diversity into later generations. 

- From Origins, revised edition by Deborah and Loren Haarsma, pages 261-262