did all humans literally descend from Adam and Eve?
Some thoughts....
1. The Creation story/stories in Genesis 1-2 certainly give the impression that Adam and Eve were the only "humanoids" created - although the text does not expressly state that.
2. Genesis 6:1-4 COULD mean that other humanoids existed, NOT descendants of Adam and Eve. But traditionally, these are seen not as other people but simply as descendants who were not believers. It's interesting to think that perhaps this is about Neanderthals but that would be pure speculation.
3. In any case, the Flood suggests that only descendants of Adam and Eve survived that, although the text does not state anything specific about the wives of Noah's sons.
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