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.

The consistent pattern of men committing mass violence is rooted in biological evolution. Men are wired for aggression and physical confrontation, a trait historically selected for by women seeking protectors. This is a biological reality, not a surprising social anomaly.

Evolutionary roles shaped vision differently. Men developed narrow, focused 'foveal' vision for hunting, making them miss items in their periphery. Women developed wider 'peripheral' vision for gathering, causing them to see more options and temptations. This explains common frustrations in the supermarket aisle.

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.

Beyond stated morals, a pro-life stance can be an unconscious mating strategy. By making abortion less accessible, it raises the consequences of casual sex, which disincentivizes promiscuity and helps secure investment from male partners in long-term relationships.

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.

The "rich gay uncle" hypothesis suggests homosexuality persists by shifting reproductive effort. Instead of having their own children, gay men may invest heavily in their siblings' offspring, promoting the survival of shared genes through kin selection. This is supported in some, but not all, cultures.

In scenarios like Jonathan Haidt's "Mark and Julie" experiment, where incest is harmless and consensual, people still condemn it. This reaction may be less about a moral calculation of harm and more about an individual's fear of being seen publicly opposing a powerful social norm.

When sperm donor half-siblings meet as adults, they may feel attraction. This isn't an innate desire for kin, but a consequence of shared genes creating highly similar preferences. They seem like a "perfect match" because the usual childhood-developed sexual aversion is absent.