Bonobos are famed for their hypersexuality and the way they use sex as an all-purpose problem solver in every possible situation, permutation and combination. When bonobos come upon a great patch of fruit, for example, and tensions rise over feeding priority, the bonobos will decompress with a quick round of genito-genital rubbing and similar acts: males with females, males with males, females with females, juveniles with adults.

Female bonobos in Congo’s LuiKotale forest use specialized gestures and pantomime to convey their desire for a bit of girl-on-girl frottage, according to a report last year by Pamela Douglas and Liza Moscovice of the Max Planck Institute for Evolutionary Anthropology in Germany. The soliciting female will point backward with a foot toward her sexual swelling and then shimmy her hips in imitation of a rub, at which display the second bonobo will embrace her for the real thing.

“It’s status acknowledgment,” said Barbara Fruth, a bonobo researcher at the Royal Zoological Society in Antwerp, Belgium. “The approaching female is saying, ‘I know you’re higher-ranking than I am, I know you’re superior, but I would like to sit near you and maybe share your food.’”

Bonobos tongue-kiss, practice oral sex, have intercourse face-to-face, and make sex toys. Frances White, a biological anthropologist at the University of Oregon, once watched a female bonobo turn a stick into a kind of knobby “French tickler,” with which she then stimulated herself. “They’re not always family friendly,” Dr. White said.

Such erotic antics have earned bonobos a reputation as laid-back “hippie apes,” a label that researchers say belies the primate’s strategic intelligence and capacity for brutality. Dr. Parish, who studies bonobos in captivity, has seen the young offspring of dominant females flaunt their inherited power by marching over to lesser-ranking female adults, prying their jaws open and extracting the food from their mouths.

She also recounted the time that two females attacked a male at the Stuttgart Zoo in Germany and bit his penis in half. Fortunately, she said, “a microsurgeon at the zoo was able to repair the damage, and the male went on to reproduce.”

Nevertheless, bonobos are far less violent than chimpanzees, and female bonobos clearly benefit from life in a constructed sisterhood. Female chimpanzees cannot pick and choose a partner from among the available males, but must mate with all of them. Female bonobos can reject suitors without fearing for their lives. Infanticide is common among chimpanzees, but unheard-of among bonobos.

The outstanding question for researchers is how the female solidarity routine started.

Male chimpanzees remain in their natal home, so their male-male bonds are built on the standard evolutionary principle of kin selection. Female chimpanzees end up surrounded by nonrelatives in adulthood, so they mind their own business.