The aim of this essay is to investigate the two major theories trying to explain why do primates have large brains. Even since the seminar study of Jerison in 1973 it has been acknowledged that primate brains are unusually large for their body size. There are three main groups of theories giving more or less persuasive explanations of the evolution of large brains and high cognitive skills in primates. The first group is a group of social theories, postulating that primate cognition is a result of complex social interactions between individuals, and in this essay this group will be represented by the Social Brain Hypothesis proposed by British anthropologist Robin Dunbar. The second group encompasses the ecological theories that are based on a premise that primate intelligence originated from complex interactions with the environment. A “delegate” from this group in my discussion will be the Visual Specialisation Hypothesis introduced by Robert Barton (1998), who argues that primate encephalisation is connected to frugivorous diet and the need of advanced visual abilities. Finally, the Cultural Intelligence Hypothesis, which is a general name to multiple related views, proposes that large-brained primates possess “general intelligence” due to their great behavioural flexibility. This final theory will be included in the comparison just to offer an alternative view to the two mainly discussed theories above.
Robin Dunbar (2003), the founded of the Social Brain Hypothesis theory, argues that primate, and indeed human, intelligence primarily evolved as means of reproducing and surviving in large and complex social groups, rather than as a means to solve ecological challenges. This is tightly associated with the Theory of Mind, or the ability to understand the emotions and thoughts of the other individuals. The Social Brain Hypothesis (SBH) is, however, not denying that the basic