It IS the world's oldest profession...

Ask yourself... how long do YOU have to groom your mate?

MACAQUE MONKEYS 'PAY' FOR SEX
Male macaque monkeys "pay" for sex with females by grooming them, according to scientists. The monkeys' version of the "world's oldest profession" is also a rare example of market forces acting in nature, with the availability of females affecting the "price" of mating. In areas where there are fewer females, males are forced to groom their partners for up to twice
as long before they are able to have sex, the research found.

Sexual activity among a 50-strong group of long-tailed macaques in Kalimantan Tengah, Indonesia, increased after bouts of male-to-female grooming, according to findings published in Animal Behaviour journal and reported in New Scientist.

On average, females had sex 1.5 times an hour, but it jumped to 3.5 times an hour immediately after the female monkey was groomed by their male partner. The females were also less likely to look elsewhere for sex after being groomed. Michael Gumert, of Nanyang Technological University, Singapore, said unlike examples of "reciprocal altruism" – in which one organism provides a service to another in return for getting something back at a later date – the value of sex fluctuated like any other economic commodity. The macaques' behaviour is thought to be an example of a "biological market".