Do pigmentation and the melanocortin system modulate aggression and sexuality in humans as they do in other animals?

► In 40 species of wild vertebrates, darker pigmented individuals are more aggressive and sexually active. ► Cross fostering studies and pharmacological dose manipulations establish the role of the melatonin system. ► We review the human literature within and between populations and find similar relationships with pigmentation. ► Darker individuals average higher levels of crime, sexual activity including HIV/AIDS, and lower IQ.