The Role of Primate Sociality in Evolutionary Theory

The Role of Primate Sociality in Evolutionary Theory

Some animals, and more specifically primates, have been noted for having brains of an uncommonly large size. One explanation for this phenomenon is the 'social brain' or 'social intelligence' hypothesis, which states that brain sizes have increased in order to handle the demands of sociality (Lindenfors 2005; Pérez-Barbería et al. 2007). The increase in brain size can be attributed to the computational power needed to track others in the group and ensure individual and species survival (Müller & Soligo 2005; Pérez-Barbería et al. 2007). Sociality in primates - and thus also in humans - has then some evolutionary basis.

This review will discuss the impact and possible reasons underlying the evolution of sociality, in relation to primates as a close approximation to humans. In particular, it will address the question of whether sociality in primates evolved as a means of survival. Each article will be rated on a five star scale, where one star represents one mark. Five stars would indicate that the article is highly relevant to the topic, while four stars would indicate a very good association with the topic. Three stars would show a mild association with the topic, while two would indicate that the article displays only a passing reference. One star would mean that the article does not display much relevance or only a part of the article is really relevant to the topic.

Social bonds of female baboons enhance infant survival

This article aimed to produce evidence to support the theory that social bonds have a unique positive influence on primate adaptability, regardless of other factors. The evidence was collected from a 16 year study of the Kenyan wild baboon population Papio cynocephalus. Social contact was defined by three estimates: the amount of time a baboon would be within five metres of another baboon, the amount of time a baboon would be grooming others and the amount of time it would be groomed by others. These factors encompass the social activities of the baboon population and are considered to be an accurate measure of primate sociality. The three estimates were then combined to form a combined sociality index score.

Female baboons engaging more frequently with other adult baboons, as well as those occupying definite social positions in the group hierarchy, were found to be most likely to succeed in raising their young. Females with higher index scores also produced children with marginally higher survival rates than those females with lower scores.

Furthermore these observations were found to be independent of other factors (e.g. female dominance) implying that primate sociality plays an important evolutionary role.

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Silk, JB, Alberts, SC, Altmann, J 2003. Social bonds of female baboons enhance infant survival. Science 302: 1231-1234.

Primate Sociality in Evolutionary Context

The aim of this article was to examine sociality from an evolutionary perspective and see whether it affected certain factors that influence sociality. These factors were an individual's weight, eating habits, movement patterns and use of environment. Rodents were used to create a model that could later be extrapolated to investigate primates, where a rodent genus was considered social if male and female social interactions occurred outside mating times and formed some kind of network with at least one adult animal. Rodents were considered a suitable group for examination as they are the largest group of mammals and display a wide range of characteristics over the given factors.

Data was collected from all rodent genera for which sociality could be measured using these four factors. The study concluded that these four factors, all impacting on animal sociality, were highly influenced by the evolution of the rodent. Large animals, those living in trees, and animals feeding on fruits, vegetables or animal matter were found to display the highest degree of sociality. This is believed to have evolved as a means for all animals to obtain food and hence be able to survive. This research implies that animals that mostly or exclusively consume fruit are instrumental in the development of social networks.

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Müller, AE & Soligo, C 2005. Primate sociality in evolutionary context. American Journal of Physical Anthropology 128: 399-419.

Neocortex evolution in primates: the 'social brain' is for females

This study used the size of the neocortex, the component handling complex mental processes in animal brains, to explore