Are you sure you got your assumptions correct on how God does things?
Why do you assume Adam and Eve were even in this realm? Maybe there were not made of flesh and blood and they existed in a different realm. There were in direct fellowship with the presence of the Creator were they not? Or maybe they were made flesh and blood and by eating by the Tree of Life, it made their bodes incorruptible against entropy and death.
Or maybe there are a million of other things in terms of details that nobody knows. But right now, as we are, God has created us with 5 senses so we have to reach to Him though these senses. So when i see the Neanderthal bones, i don't just put a fork in my eye and pretend that i never saw it.
This whole creation is a mystery and that's why faith in God is a choice we have to make, which is based on free-will again.
Jesus' resurrected body is also a mystery. He could go through walls but He could also eat food. So maybe that's how Adam and Eve was.
How God does things, is only a limitation from our point of view, not God's.