Grooming is a common everyday activity of many members of the order Primates. Grooming consists of going through the fur, using either the hands or teeth, to remove debris. Some species of primates have specific adaptations for grooming. For example, in prosimians, the incisors and canines of the lower jaw jut out, forming a comblike structure. Other species, such as tarsiers (Tarsius), have a distinctive grooming claw on the second digit of the foot that aids in grooming.
There are two main types of grooming, auto-grooming and allogrooming. Auto- or self-grooming consists of an individual grooming itself, while allogrooming is an interactive process in which one or more primates groom each other. While autogrooming is mainly used for self-cleansing, allogrooming may not be and is of particular social importance. In addition to simply cleaning the recipient’s fur, allogrooming is an important mechanism for strengthening social relationships as well as being a display of affection. Allogrooming is used to reinforce social bonds between mating males and females as well as same-sex friendships.
During the process of grooming, individuals sit close to one another and are in constant touch. As a result of this close contact, relationships are strengthened and tensions are reduced. Recently, allogrooming among primates has been compared to massages. In humans, massaging newborns helps make babies healthier and calmer. In primates, grooming is done from the moment of birth throughout adulthood. It can be used to calm emotions following aggressive outbursts, and primates become much calmer when they are groomed by their partners or relatives. Among some species, the amount of grooming received is directly correlated with social rank. Higher-ranking individuals receive more grooming than individuals of lower rank.
The social-cognitive skills obtained via allogrooming may allow primates to live together in a cohesive fashion. Allogrooming also probably contributes to survival in large groups. Primates learn at a young age to keep some group members at enough of a distance to prevent ecological and reproductive costs, while at the same time not drive them away altogether. Allogrooming is also a means of communication. In some species such as chimpanzees (Pan troglodytes), prolonged periods of allogrooming occur when an old friend rejoins the group. In addition, some go so far as to suggest that grooming in primates helped promote language development and may have given rise to the evolution of gossip.
Grooming serves as much more than just a means of cleansing the fur and obtaining tiny treats (such as lice). It is also used to strengthen bonds, communicate, reduce tensions, and as a display of affection. In other words, grooming is the social glue of primate groups.
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