Muriquis Monkeys Live the Egalitarian Life

Steve Kemper, Humans Would Be Better Off If They Monkeyed Around Like the Muriquis, Smithsonian, Sept. 2013.

When [Karen] Strier was first getting to know the muriquis, primatology was still largely focused on just a handful of species that had adapted to life on the ground, including baboons, or that had close evolutionary relationships with humans, such as apes. This emphasis came to shape public perception of primates as essentially aggressive. We picture chest-beating, teeth-flashing dominant male gorillas competing to mate with any female they choose. We picture, as Goodall had witnessed beginning in 1974, chimpanzees invading other territories, biting and beating other chimps to death. Primates, including possibly the most violent one of all—us—seemed to be born ruffians.

...Strier’s research introduced the world to an alternative primate lifestyle. Female muriquis mate with a lot of males and males don’t often fight. Though bonobos, known for their casual sex, are often called the “hippie” primates, the muriquis in Strier’s study site are equally deserving of that reputation. They are peace-loving and tolerant. Strier also showed that the muriquis turn out to be incredibly cooperative, a characteristic that may be just as important in primate societies as vicious rivalry.

Strier’s ideas shook up primatology, making her an influential figure in the field. Her widely used textbook, Primate Behavioral Ecology, is in its fourth edition and “has no peers,” according to the American Society of Primatologists.

And they're relaxed about sex:

They also tend to be easygoing about the other big activity that agitates almost all other primates: sex. Unlike chimpanzees and baboons, male muriquis don’t attack rivals to keep them from females, Strier says. There are no alphas in these societies, so muriqui twosomes don’t have to sneak off to evade punishment by jealous suitors. What’s more, female muriquis don’t need to form coalitions to protect infants from murderous males. Strier has called muriqui mating a “passive affair.” Males don’t chase down females or bully them into sexual submission. Instead, a male waits for an invitation from a female, who selects her partners and copulates openly. Instead of battling each other for access to females, males bond into extensive brotherhoods, and Strier suspects they have replaced fighting with “sperm competition.” In proportion to their slight frames, muriquis have oversized testicles. It may be that the male producing the most sperm has the most tickets in the reproductive raffle.

When Strier first observed these behaviors, she thought muriquis were anomalies in the primate world. But as research documented the behaviors of a broader range of primates, Strier realized there was actually a lot of variation—more than was generally acknowledged. In 1994 she wrote a paper titled “Myth of the Typical Primate” that urged her colleagues to reconsider the emphasis on aggression as a mediator of primate relationships, which “prevailed despite repeated efforts to demonstrate the limitations of such arguments.” She contended that the roots of primate social behavior, including that of people, might be more accurately reflected in the flexibility, tolerance, cooperation and affection that predominate among most primates, and that these qualities are at least as recognizably human as aggressiveness, competition and selfishness. Strier’s paper was pivotal in initiating a new way of thinking about primate behavior.