Human evolution has caused human males who have low exposure to female sex pheromones to instinctively want their female family members to be bred by other males.
(Finally figured out how to quote!) Could you expand on this? I'm not sure if I fully understand it. Like do you have any examples supporting this idea?
The human brain has "instincts", which are basically neural pathways that are automatically formed during fetal development. One instinct in heterosexual males is to get sexually aroused by the female form. However as you know this instinct only emerges during puberty. And the reason it emerges during puberty is because hormones are produced in the brain, which "unlock" the heterosexual instinct.
Being sexually aroused by your mom having sex is another instinct. Being repulsed or angered by your mom having sex is also an instinct.
Alpha males who are around many sexually receptive females receive lots of female sex pheromones, which unlock the instincts to not want to see females having sex aka "getting cucked". This is why alpha males will fight someone who tries to flirt with their girl, and why alpha dads don't like boys dating their daughters.
A male who does not receive female sex pheromones causes the "cuck" instinct to be unlocked. Obviously this takes time; if an alpha is alone for a day, they aren't suddenly going to turn into a cuck. But if an alpha suddenly finds themselves without a female companion for say, a year, then they might start to develop a cuck fetish.