Male macaque monkeys pay for sex by grooming females, according to a recent study that suggests the primates may treat sex as a commodity.
“In primate societies, grooming is the underlying fabric of it all,” Dr. Michael Gumert, a primatologist at the Nanyang Technological University in Singapore, said in a telephone interview Saturday.
“It’s a sign of friendship and family, and it’s also something that can be exchanged for sexual services,” Gumert said.
(via Nerdshit).