I do have one sincere question: if Paleolithic women were having that much sex, why was pregnancy (relatively) so rare? For that matter, with no pill or condoms even sex with a single mate a few times a week would presumably account for more frequent pregnancies.

I agree with Chris Crawford that the advent of civilization, not just agriculture, instituted patriarchy--which is nothing but the institutionalization of arbitrary power---which John Locke correctly asserted to be the very definition of injustice. To redeem civilization we must abandon patriarchy and all other forms of oppression by realizing that the etic of justice can only be mutual respect, without no regard for anything but our common humanity.