Humans are not monogamous. Among others, Islamic and traditional Mormon societies practice polygamy. Osama bin Laden had several wives, and Mitt Romney's ancestors moved to Mexico to practice polygamy after the U.S. government forced Utah to stop it. Bob Marley had 11 children by several different women; I've had three wives and several girlfriends.
Although many societies impose monogamy, it has not evolved. Evolution requires genetic changes to an entire population, whereas monogamy, where it occurs, is a non-genetically produced cultural tradition. In her book "Anatomy of Love," anthropologist Helen Fisher pointed out that economic factors largely determine human mating patterns. Sociologists have shown that in the U.S., monogamous families of a husband and wife have been steadily declining.
Where it occurs, monogamy in humans is a cultural and even individual choice; it is not genetically determined.
Henry A. Hespenheide
The writer is a professor emeritus in UCLA's department of ecology and evolutionary biology.