I recently noticed a Discovery Channel news item about the observation that monkeys "pay" for sex. A group of scientists studying longtailed macaques have noticed that males will groom females in return for mating privileges—sort of "friends with benefits" only the benefits have to go both ways. According to the article, macaques use their teeth and hands to pick through the fur of another macaque to remove dirt, tangles and parasites. In return for anywhere from a few seconds to several minutes of this activity, the females are receptive to mating. The article observes that lower ranking males have to groom more than higher ranking males to get the same results. Likewise, higher ranking females can get away with being more demanding.
The article equates grooming with money, but I think men who are looking for meaning in this would do better to consider grooming as just another form of housework. There is nothing sexier than a guy running a vacuum cleaner!