Now the SERPENT was more subtil than any beast of the field which the Lord God had made. And he said unto the woman,
that the sons of God saw THE DAUGHTERS OF MEN that they were fair; and they took them wives of all which they chose.
Now there was a day when the sons of God came to present themselves before the Lord, and Satan came also among them.
the sons of god mentioned here are the same sons of god as in genesis six. they are the sons of adam. neandertals, the men spoken of, were created in the first creation in genesis one.
the flood was needed due to all the interbreeding between the two species.
8 But Noah found grace in the eyes of the Lord.
9 These are the generations of Noah: Noah was a just man and perfect in his generations, and Noah walked with God. 10 And Noah begat three sons, Shem, Ham, and Japheth.
noah was perfect, i.e. complete, in his GENE(s)erations, including his sons.