As Henry Reich explains in this installment of Minute Earth, yes, monogamy does exist in the animal kingdom – though fewer creatures practice it than you probably realize.

Monogamy is observed in just over a quarter of primates and only around 3–5% of mammals, overall. How it evolved in humans is still the subject of intense debate, and with good reason. "Monogamy is a problem," University of Cambridge zoologist Dieter Lukas once put it. "Why should the male keep to one female?"

Females, with their extended gestational periods and finite physical resources, can only give birth to healthy offspring periodically. No such biological limitation exists in males, who can, in theory, sow their seed as far and wide as they please. Perhaps this is one explanation for why, as Reich observes, "among all the species monogamy is rare and monogamy without cheating is rarer."

[Minute Earth via Laughing Squid]