Evolution designed an economical system where a single, subconscious "kinship estimate" for each person dictates both altruism towards them and sexual aversion. It's one calculation for two different social behaviors, determining how close your heart should be and how far your genitals should be.

When asked to imagine incestuous acts, women's disgust is uniformly high. Men's responses show a much wider variance. This reflects the catastrophic evolutionary cost of a single bad reproductive choice for a female (nine months of gestation) versus the far lower opportunity cost for a male.

Unlike a spoken apology ("cheap talk"), a blush is an uncontrollable physiological response. It credibly signals to others that you acknowledge breaking a social norm, establishing common knowledge of your remorse and your acceptance of the norm itself. This makes the "apology" authentic.

When a norm is violated publicly, it threatens the common knowledge that the norm exists and is enforced. The resulting public punishment, like a digital-age pillory, isn't just about the transgressor; it's a signal to the entire community that the norm is still in effect, thereby restoring common knowledge.

The widespread and instinctual revulsion toward incest provides a strong case for emotivism. When pressed for a logical reason why it's wrong (beyond pragmatic concerns like birth defects), most people fall back on emotional expressions like 'it's just gross.' This suggests the moral judgment is rooted in a fundamental emotion, not a rational principle.

The speaker introduces "mate suppression" as a twisted biological impulse, particularly prevalent in toxic femininity, to harm the reproductive chances of perceived rivals. This drive manifests in behaviors that sabotage others' attractiveness or access to mates, explaining seemingly irrational social rules that secretly aim to handicap competitors.

Taiwan's historical "minor marriages," where unrelated children were raised as future spouses, show culture can override behavior but not underlying psychology. These unions had more divorces and affairs, demonstrating the persistence of the Westermarck effect's sexual aversion despite societal pressure.

Our anger towards hypocrisy stems from a perceived 'false signal.' A hypocrite gains status (respect, trust) without paying the cost of their claimed principles. This triggers our deep sense of injustice about an unfair exchange, making the violation about social standing more than just morality.

People's conscious, stated reasons for their actions (proximate explanations) often obscure deeper, unconscious evolutionary drivers (ultimate explanations), such as the drive to reduce mating competition while appearing compassionate.