Key ideas from Debra Lieberman

• Humans evolved sophisticated kinship detection systems using cues like maternal breastfeeding and co-residence duration to identify genetic relatives and develop sexual aversion toward them
• "The longer the duration of co-residence during early childhood, the more certain you are that an individual is a genetic relative" - Debra, explaining the Westermark effect
• Crying functions as a negotiation tool used by lower-leveraged individuals to communicate value states and influence others to stop imposing costs or deliver benefits
• Women cry more than men not due to weakness but because they're typically less physically formidable, making tears a more effective strategy than anger for negotiation
• Incest porn's popularity doesn't contradict disgust mechanisms because viewers lack the kinship cues that would trigger aversion - "it's just two people who are naked having sex"
• Cousin marriage remains prevalent worldwide because genetic risks drop dramatically from 0.5 relatedness (siblings) to 0.125 (cousins), making biological concerns minimal