The events of Genesis 3 were clearly of a sexual nature, Adam and Eve felt shame afterwards, Eve was pregnant and they needed clothes to protect themselves from the lusts of the non-adamites around them.
Cain murdered his brother and then left to marry and build a city with these non-adamites, who were the mixed-race branches of the tree of the experience of good and evil.
His descendants were still around after the flood, as Rephaim, Kennites, Anakim and others and they were all to be found in the land where Canaan lived.
His posterity interbred with them and continued their line up to where Esau Edom married into them and his offspring became the rulers of Judea by the time of Christ.
This is why Christ called them devils and held them responsible for the death of all the prophets from Abel onwards.
Sven Longshanks and William Finck – Bible Basics Part 8