The podcast explores how humans and animals avoid inbreeding through evolved cues like co-residence, caregiving observation, and smell, with the Westermarck effect playing a central role in developing sexual aversion among siblings raised together. These same mechanisms support altruism within families. When biological relatives meet later in life—such as half-siblings from sperm donation—genetic sexual attraction can occur due to shared traits, not innate desire. Moral opposition to consensual adult incest often relies on intuition rather than logic, illustrated by studies showing people condemn it without coherent justification. While cousin marriage carries relatively low genetic risk, social taboos remain strong. Crying is examined as an evolved social signal of vulnerability, used to elicit empathy or cooperation, especially by those with less power. Tears—even feigned ones—function as strategic tools in social negotiation. The episode concludes with insights into Lieberman’s research and her efforts to democratize access to scientific knowledge.