John Farrell wrote about the problem that modern theories of polygenism pose to the Christian doctrine of the fall. The article was picked up by Bill Vallicella and Mike Liccione. Any time one mentions this controversy, the discussion threatens to explode in ten different directions at once, so I’ll cut to what I take to be the final answer, which I see as having three parts: (a) No revision of doctrine is necessary (b) defending the old doctrine does not require dialectical backflips and hair-splitting; and (c) The revision that is called for is not a revision in doctrine but a move from the simplest set of facts congruent with a doctrine to a less simple set of facts congruent with the same doctrine. The difference here is crucial: a change in doctrine would be like moving from evolution to creationism; a change in facts congruent with one doctrine would be like moving from incremental to macro evolution or from Paley’s design theory to Dembski’s.
The best science is that there was never a time when there was only one generating couple on earth. Right off the bat, there are difficulties in bringing this finding into conflict with the Scriptural text, since Cain finds people outside of Eden as soon as he is cast out of it. We can, of course, adopt the ancient Rabbinical commentary on this that Cain in fact finds only his brothers and sisters, though this interpretation is perhaps not the simplest one, and it also creates its own problems (What are his siblings doing outside of Eden anyway? There appear to be a good many persons with a good deal of technical skill out there.) Even after we take into account the mythical character of the story, it is not clear that the intention of the author was to have Adam enter into a world without human beings. It is true that Eve is called “the mother of all the living”, but in everyday language we mean more than one thing by this, which should become clear in a moment.
The difficulties in parsing out the Scriptural narrative make us cast about for a more unequivocal statement, and all sides agree that we find it in Humani Generis:
[T]he faithful cannot embrace that opinion which maintains that either after Adam there existed on this earth true men who did not take their origin through natural generation from him as from the first parent of all, or that Adam represents a certain number of first parents.
Usually, authors include the next sentence that gives the reason why one can’t hold either position, but this skips too quickly over what exactly Pius is condemning. Just look at the words of the first condemned opinion:
After Adam there existed on this earth true men who did not take their origin through natural generation from him as from the first parent of all.
This is a statement about the world after Adam. But when something happens over a period of time (as opposed to being a single event) to speak of what happened after it is usually to speak of what happened after it ended not after it began. For example, if you say “after Marcus Aurelius the persecution of Christians ended”, you are talking about what happened after Marcus died. After can also mean “after the beginning”, as in “After Constantine, the Christians received more rights”, but even this is ambiguous, since one is really trying to speak of something that happened during Constantine’s reign and not necessarily at its inception.
Why is this significant? Take two hypotheses:
1.) There were no men anywhere on earth. Then Adam was created. Then all later persons descend from him.
2.) There are men on earth. Then Adam was created. By the time he died, all living persons had him as an ancestor.
Pius’s condemnation doesn’t apply to either hypothesis. Said another way, if we want to decide between these hypotheses – even as faithful Catholics – we are going to appeal to something other than Pius’s condemnation. All other things being equal, of course, the first hypothesis is the simpler one and so is the reasonable one to adopt, and for the Church Fathers and almost every scriptural commentator up until very recently, this ceteris paribus clause still had force. There was, however, always reasons to question it: one could have always wondered where Cain’s wives and male citizens came from (as the Clarence Darrow character does in Inherit The Wind), or he could fall across a finding in physical science that the human population was always greater than 1. Either argument gives a reason to abandon the simplest hypothesis. The need to “revise theology” is therefore not a need to move from one doctrine to another, but from a simpler explanation of the doctrine to a less simple explanation. By “simple” I mean more or less the doctrine one would form at first glance, all other things being equal. Again, the motion is not from one doctrine to another but from a simpler to a less simple set of facts under the same doctrine. We are not moving from monogenism to polygenism, but from a simpler account of monogenism (all after Adam descended from him, and there were no others) to a more complex monogenism (all after Adam descended from Adam, but there were others.)