Monkeys and humans belong to the same order of primates, they belong to the monkey family and we belong to the human family, and in terms of kinship humans and monkeys are close relatives. However, why are they repeatedly unpleasant? Monkeys have their own way of life, so why do they engage in housebreaking and prostitution?

Fany Brotcorne, a primate expert at the University of Liege in Belgium, has conducted a study on monkey robbery, and found that a group of long-tailed macaques living near a temple in Indonesia have been extorting tourists for a long time by taking valuable items from them, such as mobile phones, cameras and hats. They then waited for tourists to pay a "ransom" of food to get their belongings back. To find out why, Brotcorne's team spent nearly four months observing four different groups of monkeys around the temple. The age structure of the monkeys in these four groups differed, as did their exposure to visitors. The observations showed that the two monkey groups with the most exposure to tourists had the highest rates of extortion and robbery, while the monkey groups that were further away from the crowd were also the more peaceful.

In addition, the probability of robbing tourists was related to the age structure of the monkeys in the group, with the more young males in the group, the higher the probability of participating in robbery. Within the group, young males have a lower status within the group, and the higher ranking individuals in the group occupy the most food-rich territory, which they have no right to get their hands on. The young males have no choice but to expand new avenues in order to obtain quality food. Once one of them has acquired a new food item, it can easily be spread among the group. Many new food acquisitions in monkey groups often come from the exploits of young males.

‘It is not difficult for monkeys to learn from each other and imitate each other, for example, if one monkey commits a robbery and another monkey imitates it. However, for a certain behavior, such as "robbery", to spread among the monkeys so that all other monkeys learn and accept it, it is not simply an individual imitation, but a social learning behavior.