Scientists seem to have proved that sucking up to the boss just to win his support or the support of the others dates back to our monkey ancestors. And like in humans, the motivation can be food, sex, power and so on.

Being picked off the dead skin and bugs from the fur must provoke a great pleasure rewarded with backing in fights. "Scientists have wondered for decades, 'Why should a monkey spend time cleaning the fur of another,'" said Gabriele Schino of the National Research Council in Rome.

Two decades ago, psychologist Robert Seyfarth suspected that monkeys groom each other for support. Subsequent studies were inconsistent and irrelevant. So Schino made a meta-analysis on 36 studies effectuated on 14 different primate species. In their social groups, primates often fight over food, access to mate or to get up on the hierarchy.

In a conflict between two parties, a third party can choose which side it will back. (as well documented on chimps, e.g.). Grooming creates links among individuals and frequent groomers will receive more frequent support from those carried on by them.

The study also showed that Old World monkeys (all the monkeys found in Africa and Asia like macaques (photo), baboons, colobus, langurs, guenons) practice the groom-for-support behavior more than New World monkeys, found in Mexico and Central and South America, like capuchins, marmosets, uakari, howler monkeys.

This proves that this behavior is a highly evolved feature, less developed on the more primitive group of the New World Monkeys. Chimps also groom a lot and their interested grooming has been proved to be beneficial. After hunting, meat that is full of precious protein will be offered by males to female grooming partners.

And low hierarchy males in some monkey species could benefit of sex, forbidden by alpha male, from benevolent female satisfied by previous grooming orgies.