It was a moment that smashed assumptions with the force of a wrecking ball. She approached the sexy older male who seemed to arrive from out of nowhere, his black-and-white coat gleaming in the light. She put herself directly in his path, shook her head provocatively, then turned and bent over to “present” herself to him. She eagerly pressed her backside against his groin and the two gyrated against each other. Spectators watched as the two built toward a climax, and then they went their separate ways. The sexual display took the scientific community completely by surprise.

 

When primatologist Sarah Hrdy described this behavior among female hanuman langurs—or Semnopithecus entellus, a monkey species from western India—in the late 1970s, it erupted into the kind of controversy usually reserved for lewd performances at the MTV Video Music Awards. Ever since Darwin there had been an assumption among evolutionary biologists that females were coy and choosy in their sexual behavior while males were the ardent, promiscuous sex.