I actually don't fault them at all for believing this. The only way to know that A causes B, is if you consistently observe the absence of A, paired together wi

I actually don't fault them at all for believing this. The only way to know that A causes B, is if you consistently observe the absence of A, paired together with the absence of B. Ie, you need a control group of women in their teens/20s/30s who are not having sex. In societies that frown upon premarital sex, this control group is easily found. But in a society that practices free love, this control group doesn't exist at all. Even worse, the people who you think are in the control group (the wife of the guy who went on expedition, and the "truly hideous" women), are actually having sex secretly, and thus further misleading everyone else. I wonder how many such "obvious truths" we ourselves are missing out on, simply because we haven't done any structured experiments relating to their absence.