MM, you are mistaken.
"The question of whether the first couple of chapters of Genesis are literal or story-telling makes no difference, really."
Unless you mean they make no difference to an atheist.
The lineage of Adam is absolutely necessary. Through Adam, we have all inherited a sin nature that can only be dealt with by the sacrifice of God Himself, through Jesus dieing on the cross.
If we instead evolved from apes, some of us would be of a line that had no sin. Also, if humans were from apes, the other humans would see how severly God dealt with Adam and Eve, that they would never do the same. That would open the door for prejudism.
"The lineage of Adam is absolutely necessary. Through Adam, we have all inherited a sin nature that can only be dealt with by the sacrifice of God Himself, through Jesus dieing on the cross.
"
OK, I'll grant you that, in terms of Christianity. However, the allegory would still make sense, given that humans created through evolutionary means would still be imperfect creatures, subject to error. Indeed, evolutionary origins of humanity would produce constant small errors in design, resulting in that very imperfection.
But, I realize that many Christians are convinced that the Genesis 1 and 2 accounts are literal. That's fine, if it helps them with their faith. Many other Christians, however, are not necessarily believers in the literality of the Genesis creation accounts. They still believe in the sinful nature of man and the need for salvation.
My point is that it doesn't matter, because being Christian means accepting those two things, along with a short list of others. Belief in man's sinful nature and the need for salvation through Jesus is the core of Christianity. The Genesis account is not. Either path leads to the same conclusion.
So, since Jesus has died, we no longer have to worry about that inherited sin, do we?