Is the argument for this claim that women are so naturally sexually slavish that their brain's higher functions are becoming vestigial and unnecessary? If that's the case, how would that apply to horny polygamous Chads?

I realize that men are inclined to be polygamous by nature because they don't have to bear the burden of pregnancy and childbirth but, IF the argument is that being a slave to sexual instinct makes you shallow-minded, why wouldn't men just be equally shallow (if not more so) if reproduction is a much less precarious role for males that requires less brain power for watching out for danger and taking care of children?

OR is the argument that women are socialized to be shallow thinkers from a polygamous and materialistic culture, while, historically, men had more opportunities to pursue education?

OR is the argument that primitive women tended to have a more sessile lifestyle taking care of children while primitive men tended to be hunter gatherers?

Are none of these resemblant of the actual argument that women are shallow thinkers? If so, what is the actual argument?