Are Humans Similar?

Abstract

Abstract Similarities between humans and boobies suggest independent evolution in their respective lineages of functionally equivalent family conflict. Babies and toddlers show anxiety and aggression when newborns arrive and when mothers pay attention to them. Reluctance to share with siblings is normal, as is aggression over property and space, which peaks at 3–4 years and fades during adolescence. Sibling power imbalance exists in all cultures examined, and some sibships in the West exhibit pathological dominance-subordination. Humans pair-bond through courtship, involving displays of age, beauty, wealth, intelligence, and personality. A minority of both sexes court and copulate secretly with extra partners, and 2–17 percent of births are sired by extra males. Male infidelity wins additional offspring; female infidelity may facilitate partner-switching, assure fertilization, secure better genes, and earn concessions to offspring from extra males. Males’ defenses include displaying wealth, guarding or confining partners, aggression to partners and rivals, and reducing investment in dubious offspring.