A partial quote from one of Leo's posts that may be of interest :
" Moreover, several antediluvian conditions described in Gen. 4-6 are otherwise indicated as still existing, with no knowledge of a Flood that wiped them from existence. Cain (Gen. 4:17-26) was the eponymous ancestor of the Kenites (a population related to the Midianites famous for metal-working), and Tubal-Cain in v. 21 was the "ancestor of all metal-workers," referring also to the famous Tabal metal-workers of the North (cf. Gen. 10:2, where another eponymous ancestor is given). Gen. 6:4 discusses the Nephilim as "being on earth in those days and later as well," and we find in Num. and other Pentateuchal writings how they were still living in the time of the Israelites, same thing with the Rephaim giants who were still living in the time of Abraham (Gen. 14).
So it is not so much a matter of people that the Flood missed, but a stratum of primeval traditions that knew nothing of a Flood.
Leolaia