This is much less problematic than biologically different types of "human (e.g. Homo sapiens and Neanderthals) interbreeding.
Once again, language here creates problems where there is none. How about still “human” before and after, but now in a different theological era, because they are now under the fallen headship of Adam. There need not be a theological problem here, but it does depend on the full theological system invoked. That is all under development, so it is premature to make judgements at this time.
The God we find in the Bible is making theological distinctions all the time, and the word “human” is not in Genesis. Rather it is “adams” of which Genesis speaks. It is not unreasonable to think that Genesis is telling us the origin of adams from Adam. The fact that we translate this to “human” and “mankind” in our heads may just be confusing everyone. Maybe. In this reading, adams were a subset of Homo sapiens during Genesis, but become everyone by the time of Paul (or earlier). Scripture (and the Gospel) is given to all us adams, so it’s not surprising that we conflate this with “human.” That is a perfectly fine mistranslation for the present, but might fall apart in the distant past.
So all we really need is a willingness to wonder why God might make a distinction between Adam’s descendants and others. That is where things get most interesting, and are least considered. Give it time. =)