That's actually what troubles me. There's seems no real concern in the text nor in any of the non-canon books. I'm not looking for wild conspiracy theories as I'm secure in the creation of all by God alone. But you have to admit, it is an interesting question that raises all sorts of questions. Were these Adams offspring who had been sent from Gods presence prior to Cains sin? We're they simply continued creation of God but not deemed or included as Gods true people? Are they simply spiritual demons that he's afraid of, now that he's no longer protected by God?
It says that when Adam named all of the creatures, that no acceptable mate was found. Is this to assume they hoped some animal would be good for Adam? Or, is this to suggest that there were other <mates> but that obviously wouldn't work for procreation? Or does it simply mean, there were none other like Adam, period?
What I have been taught is important when coming to an understanding of the Bible is to note what kind of story that is being presented to you at any given point in time.
Is it history? Or is it an allegory, or perhaps maybe even a new understanding of an archaic myth that came from the mists of human origins? Maybe there is no final answer to any of those questions, and nobody really is such an expert on this as to tell you what to conclude.
Always though, for every page, chapter and verse, for every jot and iota, the Bible gives us theology. All the rest is a backdrop to God revealing himself to us, and also revealing us to ourselves, so that we may come to some kind of understanding of who we are and what we are created to be.
And here, I do think you have come upon one of the central themes. Might man find a suitable mate among the animals? Who are we really? Are we actually animals, and therefore might find mates among animals, among the beasts of the fields?
It seems amusing at one level, to think that Adam might find a mate, a sexual partner even, among the animals, but much of modern science says that that is exactly who we are—just another species of animal!
Indeed, the most magnficent beast of the field, a walking, talking, highly intelligent and insightful snake, comes into the story directly after Adam deems no animal a suitable mate, and Eve was created to fill that void.
This does not seem to be a very scientific sort of event, woman coming from the side of the man, but it does tell us about the basic unity of man and a woman, their relationship as side to side partners.
And yet the beast that most resembles men, in this case the walking, talking snake of taste, does show himself to be a possibility of a mate for Eve, even if Adam had already rejected all the beasts. He is able to talk to Eve, to really relate to her, through an appeal to a desire, to the appeal of physical beauty, of what is pleasing to the palate, what is beautiful to contemplate even.
Such is the voice of God even—for beasts. To listen to their desires rather than to God speaking to their minds through commands that go against desires is the nature of the beast.
But for humans, this is a recipe for death. Murder, slavery, and will to power result from mankind listening to our desires. We listen to the voice of God, we are higher than the angels. We allow the beast to take the drivers seat, there is no beast capable of the evil that we are capable of.
This is the kind of thing that was of interest to the earliest rabbis and the earliest church fathers. In a world in which our brightest and best tell us we are nothing other than animals, maybe it ought to be of interest to us as well, those of us who still study theology.
Questions from empirical science were of little concern for the earliest students of the Bible, because they had a whole different kind of way of looking at the world than what we do.
Just exactly how it came to be so that there were other people for Cain to deal with is simply outside of the text. The story doesn't really delve into how that could be so, because it is just not that kind of story. I imagine that scientists have a better explanation of how that could be so, much more than the Bible even interests itself in answering.
There is no theological theme that is pertinent to that kind of question, and the Bible is theology to the jot and iota.
