"naturalists" and "Adamites" and "ultra-natural" - you're joking, right? That "Sethite view" has been debunked since its invention.
The most fatal flaw in the specious "Sethite" view is the emergence of the Nephilim as a result of the unions. (likewise, "giants" does not resolve the difficulties.) It is the offspring of these peculiar unions in
Genesis 6:4 which seems to be cited as a primary cause for the flood.
Procreation by parents of differing religious views do not produce unnatural offspring. Believers marrying unbelievers may produce "monsters," but hardly superhuman, or unnatural, children! It was this unnatural procreation and the resulting abnormal creatures that were designated as a principal reason for the judgment of the flood.
The very absence of any such adulteration of the human genealogy in Noah's case is also documented in
Genesis 6:9: Noah's family tree was distinctively unblemished. The term used,
tamiym, is used for
physical blemishes.
1
Why were the offspring uniquely designated "mighty" and "men of renown?" This description characterizing the children is not accounted for if the fathers were merely men, even if godly.
A further difficulty seems to be that the offspring were only
men; no "women of reknown" are mentioned. (Was there a chromosome deficiency among the Sethites? Were there
only "Y" chromosomes available in this line?)
2
1.
Exodus 12:5,
29;
Leviticus 1:3,
10;
3:1,
6;
4:3,
23;
5:15,
18,
25;
22:19,
21;
23:12;
Numbers 6:14; et al. Over 60 references, usually referring to the freedom from physical blemishes of offerings.
2. Each human gamete has 23 pairs of chromosomes: the male has both "Y" (shorter) and "X" (longer) chromosomes; the female, only "X" chromosomes. The sex of a fertilized egg is determined by the sperm fertilizing the egg: "X+Y" for a male child; "X+X" for a female. Thus, the male supplies thesex-determining chromosome.