Amy Parish—a primatologist and self-described Darwinian feminist who has been studying the species for some 30 years—was looking through the enormous windows with me and explaining the finer points of being bonobo. “Everyone knows them as the free-love, sexy apes,” she observed as the troop of nine crossed the verdant enclosure, bisected by a small “stream.” Two younger bonobos climbed up and hung from the bamboo-and-rope sway structures; others flopped onto a rock outcropping to sun themselves. A male groomed a nearly bald female.

At first glance, bonobos look a lot like chimps, just taller and slimmer, with smaller heads and ears. But unlike chimps, whose modus operandi is to duke it out under stress, bonobos “consort” when they come upon food, or when they encounter a new troop of bonobos, or whenever they feel the need to dispel tension and cement social bonds.

And how. In the wild and in captivity, bonobos appear to have sex all the time, with just about anyone. Their sexcapades are not just casual and seemingly indiscriminate; they are remarkably creative. The anthropologist Meredith Small describes watching bonobo sex as “like watching humans at their most extreme and perverse.”

Notably, bonobo females approached by a female and a male simultaneously for sex (it happens) tend to choose girl-on-girl action. Lying one on top of the other or side to side, they press and grind their vulvas together, often shrieking. Their clitorises—richly innervated, larger than a human female’s, and more externalized—probably explain why female bonobos so eagerly practice genito-genital, or G-to-G, contact. It feels good, possibly even better than intercourse with a male.

Female pleasure is central to bonobo society. Early in her career, Parish noticed that female bonobos get groomed a lot more than males do, and that the females eat first. Based on these two indicators of dominance, she began to suspect that bonobos were very different from chimps, long considered the best template for understanding the evolutionary origins of human sexual and social behavior. “Male bonobos are not aggressive toward females, and we don’t see infanticide, or females being sexually coerced,” Parish told me.

Female bonobos are, however, known to attack males, swatting, gouging, smacking, and biting those that cross or merely annoy them. Parish described a male bonobo in Frankfurt with only eight digits intact, and another male that had had its penis nearly severed. Intrigued, Parish looked at zoo veterinary records and discovered that more than 95 percent of serious injuries were inflicted on males by females. Bonobos, Parish realized, are a female-dominant species.

As we stood there watching the bonobos lounge peacefully that sunny day, Parish also told me about an even more sinister side to male-female bonobo relations. Females often initiate sex with males, and the males are often receptive. But sometimes an unenthusiastic male may try to shake off a female, to little avail. A female may “solicit” such a male again and again, putting her arms around him repeatedly as he attempts to slip away, refusing to be refused. Eventually, they have sex.