The children of Adam and Eve are only noted as the males. Their daughters are not mentioned. The traditional understanding is that Cain married some of his sisters who are not mentioned. The incest laws had not been made at this time, and presumably much of the defects therein were not to have happened except that the fall damaged the body in various ways.
The explicit rejection of Polygenesim follows on the book of Tobit where the statement is made concerning the bringing forth of children for God – that they all come from Adam and Eve.
Tobit 8:6 “You made Adam and you gave him his wife Eve to be his help and support; and from these two the human race descended … Now, Lord, you know that I take this wife of mine not because of lust, but for a noble purpose…”
Notice Tobit is marrying a fairly near relative as is the custom of the Jewish tribes.
The consistent teaching of the church which was again ratified by the encyclical on human generation – is that there was only one such couple from whom the entire human race descended. One can’t posit multiple Adams and Multiple Eves in parallel for the reason that then at least some of the human beings would not have been physically related to Adam in his sin, and St. Paul’s comment that all “sinned in Adam” would appear to be false since this clearly relates to the physical descent of the body from Adam.
Eg: The church has not infallibly defined the doctrine with clarifications regarding far fetched possibilities, but there is a demand that in some way we are all related to a “first couple”.
In the many theories of Evolution, Polygenism is one way people think it “could” have happened. But, from what I understand of the various theories – it is not a very likely candidate for the evolution of human bodies in any event.
Fossil records, as far as I have observed, show that although one can argue the slow modification of a limb or other appendages within an existing species – that the genetic modification which leads to a new species does not typically come from many slow and parallel mutations.
Generally speaking, the new species appears rapidly at a given point suggesting that it had a single parent/couple and that it became dominant because of the adaptation.
eg: in plants, a new species of weed is typically marked by a singular genetic modification which can’t breed with the old species by the very fact that the change is no longer compatible with the old species. Eg: Genes are designed to protect the integrity of their copying, and have self defense mechanisms to severely reduce the odds of mutations entering the Gene pool.
Just so, if two separate mutations were to occur both of which were the building blocks of “Human” than these independent strains of Humanity are even Less likely to accept each other as compatible genetically. The far more likely path, theoretically, is siblings from the same parent.
Just so, in plants, a new plant species becomes self reproducing by making a genetic mutation which is at least able to reproduce with another plant having the SAME genetic mutation and I suppose as coming from the same parent plant which originated the mutation.
This extra step is called polyploidy.
Humans are even more advanced than plants, but
just so, Adam and Eve, as Genesis states – had Eve come from Adam – that mirrors closely the more common way (at least that I have verified has any validity at ALL) that a new species MIGHT come into existence.
Eg: Adam and Eve from the point of evolution would need to be sort of “twins” from the same non-human/semi-human parent who transmitted the changed genetics to her offspring.
Or at very least (and far less likely), the human child of the non-human parent would have needed to mate (or be “raped” by) its originating non-human parent who has the genetic change (at least in the reproductive system) in the first place.
The Sister or Brother in that case (and still only in rare instances) could mate with their sibling and produce a new species. Eve would have received her physical humanity from Adam in either event (or possibly vice versa) whereas the “spirit” or “soul” has nothing to do with the inheritance of a physical body and is not at all affected by the theory of evolution.
Both views lead to the same conclusion, that which is human came through a single parent of some kind.
As to my opinion, I don’t rule out miracles … either…
But I tend to think polygenism is a weak theory regardless…