Biological anthropologists and evolutionary psychologists commonly take it for granted that human monogamy has a biological basis. Desmond Morris was an influential early advocate. His 1967 ...

To survive, animals compete for resources, be it food, mating partners or territory. But a ground breaking recent study shows chimpanzees and gorillas form friendships, some lasting at least 20 years.

Relative to body weight, that's three times larger than gorillas' but five times smaller than chimpanzees'. Mating strategy explains this drastic variation in reproductive organ size. Gorillas are ...