Fl. a = deviations from perfect symmetry in normally symmetric species. Caused by environmental stress (i. e. poor nutrition) during development. Most attractive dancers were also most symmetric. Symmetric men also have more sexual partners, begin intercourse earlier in life, and have more extramarital affairs. Predicts perceived attractiveness by others: facial attractiveness & sex hormones. Attractiveness ratings taken with & without makeup; urine collected for hormone analysis. Makeup eliminated all effects: cheater detection easier to solve. Cross-culturally universal: evolutionary psychology & the sssm. Logical problems involving cheater detection rather than rule verification are. Sssm (standard social science model) drove psychological research for decades; predicated on 3 assumptions: tabula rasa (blank slate, general laws of learning, irrelevance of biology. Cruel step-parent effect can be approached using loas. Increased financial hardship in mixed families: human universals. More potential cultures that have never existed than actual cultures that. Cultures are much more similar to each other than they are different. have.