A report on Yahoo says male monkeys "pay" for sex by grooming females (physically, not on the Internet, that is). It's being offered as evidence that prostitution has evolutionary roots. Now theres two little issues I have with this.
1. It's natural to shit in a ditch. Genocide is "natural" - chimps do it. Killing and eating your young is "natural" - polar bears in German zoos do it. Natural as defined by "an animal does it" or even "our primitive ancestors probably did it" has nothing to do with "it's a good idea" or "we should keep doing it". Which is what seems to be the author (of the piece and possibly the report)'s rather smug message.
2. How exactly is grooming parallel behaviour to paying? I could understand the implication if the male chimps gave the females food in exchange for sex. But surely grooming is more like petting. And no-one considers themselves a prostitute because they don't like to have sex without a bit of foreplay. Actually if you look at social evolution it is widely accepted that as ape social groups grew in size, chatting replaced grooming as the glue of social cohesion. So the grooming behaviour would be akin to chatting a woman up. Again talking to your sexual partners does not make you a prostitute.
The report goes on to "back up" the initial theory by pointing out that females require less grooming when there are other females around. But then maybe they just don't like all their mates watching them being chatted up. Or maybe they want to get it over with and go hang out with their female friends.
Drawing conclusions that fit your own sexist preconceptions is a real waste of time in an area of science that could really use a lot more attention.