"So where did Cain's wife come from again???
From people that existed in that area."
If Cain was the son of the first humans (Adam and Eve), what other people were in the area? That only leaves the option that the Bible left out some important information, like other humans God created out of the mud, or Adam & Eve were not the only thing going.
So where did bacteria come from again?
I have no idea. Maybe God made it. Maybe Aliens implanted it. The point is Noah did not have a pet dinosaur and the sky was not pink.