So asks Time’s Krista Mahr. I think both the article and the research paper on which it’s based seems to be really stretching to analogize this to human prostitution:
According to the paper, “Payment for Sex in a Macaque Mating Market,” published in the December issue of Animal Behavior, males in a group of about 50 long-tailed macaques in Kalimantan Tengah, Indonesia, traded grooming services for sex with females; researchers, who studied the monkeys for some 20 months, found that males offered their payment up-front, as a kind of pre-sex ritual. It worked. After the females were groomed by male partners, female sexual activity more than doubled, from an average of 1.5 times an hour to 3.5 times. The study also showed that the number of minutes that males spent grooming hinged on the number of females available at the time: The better a male’s odds of getting lucky, the less nit-picking time the females received.
If you think about human society, “paying for sex” denotes a pretty specific kind of social practice—prostitution—and isn’t a catchall phrase to cover every mutually beneficial relationship that involves sex. You could probably do a study of married human couples that would show that sex is more likely after a husband is nice to his wife than after he’s been a jerk; I don’t think you’d call that a study about “paying for sex” among married couples.