In Genesis, the line of Cain was discontinued suddenly, and presumably this change in attitude was related to the murder of his brother Abel. Cain was exiled to the lands east of Eden where he later produced a son also called Enoch who was reportedly the builder of cities, seven in fact, all named after his sons. It is perhaps coincidental that there were seven major cities built by the Sumerians before the Deluge and suggests a common source of origin.
Genesis continues the line of Cain, uneventfully, through Irad, Mehujael, Methusael, and then ends with Lamech. Not content with dropping the line here, the Scriptures left behind a puzzle, a cryptic verse that has been the bane of Biblical scholars. The verse which ends the line of Cain is as follows:
"Lamech said to his wives, Adah and Zellah, hear my voice, O wives of Lamech, give ear to my speech; I have killed a man for wounding me, a boy for injuring me. If Cain be avenged sevenfold, then Lamech seventy-seven fold."
Genesis then drops all mention of the Cainite line and abruptly begins the genealogy of Seth. Obviously the verse contains the clues to this sudden change of policy. If the line was doomed, what were the reasons? The solution to this enigmatic verse which ends the line of Cain probably lies in the existence of the two, even three, parallel lines of descent.
We know that the book of Genesis is a book written by the jews while they were held captive in Babylon under the reign of Nebuchadnessar and that it was based on Babylonian fairytales and legends/myth.
Please see threads "if god exist's" post 36 . and , "proof of god" posts 72-80.and in "modern prophet"
To take it for it's literal meaning as opposed to exegetical fact is naive to say the least. please read above post as it explains why saves me a lot of writing