- 2 January 2008
- Magazine issue 2637
SEX has probably been a commodity for as long as human society has existed, and perhaps even longer. The "oldest profession" seemingly has pre-human evolutionary roots. "When the opportunity arises, male macaque monkeys groom females to 'pay' for sex," says Michael Gumert of Nanyang Technological University, Singapore.
Gumert looked at research on a 50-strong group of long-tailed macaques in Kalimantan Tengah, Indonesia, that covered a 20-month period. He found there was an increase in sexual activity after bouts of male-to-female grooming. On average, females had sex 1.5 times per hour, but immediately after being groomed by a male partner, this rate jumped to 3.5 times per hour. After grooming, the female was also less likely to offer herself to males other than her grooming partner (Animal Behaviour, DOI: 10.1016/j.anbehav.2007.03.009).
"My interest in this study stemmed from Trivers's theory of reciprocal altruism," says Gumert. In the early 1970s,