I find the notion that we inheirited sin through Adam and Eve to be a quaint, silly notion. If you believe in the power of God, why would God create such a flawed creation? Few people believe the stories in Genesis. We can't go out an rape, pillage, burn, and enslave unbelievers b/c God did it in the Old Testament. The story makes some sense in symbolic terms. I don't believe the people believed it literally.
Does an infant have free will? Furthermore, how does one reconcile free will and the concept of the elect? Adam was alone. There was no civilization. Perhaps Adam derives from ancient memories of evolution when Neanderthals and Homo Sapiens both lived. His brain was probably limited compared to our brains today. Original sin does not show up in the genetic code.
Evidence shows that these stories were commissioned after Israel was a nation-state. There are proabbly Canaanite elements in them. Was the earlier human truly Jewish? Science finds otherwise. No, original sin is a concept and not a biological fact. Genetic mutations are a fact. Some people are born severely mentally challenged, do they have original sin.
Besides, Christians should believe in the salvation of Christ. The world is transformed by Christ -- if you have faith. Why be ignorant? When not believed literally, these stories still have resonance. The writers of scripture did not understand blood or flesh the way we do today. Deeper concepts are possible when not read literally. Christians do not have to be stupid. We can be informed.