Could you tell me if the following position would be within the confines of dogmatic Church teaching?
According to some scientist, the level of genetic variation present in humans today rules out a founding population with fewer than several thousand individuals. Lets assume these scientist are correct (and they may not be).
What makes a “human” and what makes an “almost, but not quite yet human”? The difference is presumably the presence (or not) of a human soul sent directly from God. A physically human large brained upright walking ape without a soul directly infused by God is not fully human, it may be human physically with human-compatible DNA, but is not human spiritually since it does not have a human soul. A physically human large brained upright walking ape with a human soul is human, both physically and spiritually.
Start with a population of un-souled upright apes, call them pre-human because they are not quite human yet. God puts human souls into two of them, Adam and Eve. Adding a soul does not change the original pre-human DNA at all. We now have a pair of humans, Adam and Eve, from a population of pre-humans. Adam and Eve only mate with each other and have human children with souls (put in directly by God at conception per CCC). The children find mates outside their immediate family so they mate with some of the pre-humans – an activity even more likely in a post-fallen world. This is possible because their DNA is compatible with pre-human DNA; the mating is open to the possibility of creating life. God gives a soul to all hybrid human/pre-human offspring so all the children with at least one human parent are also human, i.e. they have a soul. Because only the descendants of the initial pair mate with pre-humans, all the children from such matings are descended from both Adam and Eve since they will have genes from both as their grandparents, great-grandparents etc.
Also, perhaps the pre-humans found the “souled” humans attractive perhaps because of aspects of the soul having positive influences on behavior, albeit a fallen soul. Because of the aforementioned selection process, over time (perhaps 50,000 – 75,000 years) the number of humans increases and the number of pre-humans declines until the pre-humans are extinct. In the process the humans acquire the genes from the pre-humans that are reflected in the current human population.
In scientific terms we have a large interbreeding population, as shown by the current level of genetic diversity in humans. Theologically all humans are descended from both first ensouled pair.
This is a possible scenario that is compatible with current scientific knowledge and with many interpretations of Genesis. The Fall would have occurred between the creation of Adam and Eve and the conception of their first child. The fallen state is transmitted from Adam to his descendants.