ABSTRACT
In 1993, Dunbar extrapolated the theory that group size in non-human primates is dependent upon neocortex size to the human context. The concept is that the “current neocortex size sets a limit on the number of relationships that it [an animal] can maintain through time, and hence limits the maximum size of its group” [1]. Dunbar applied this to humans, suggesting that the number of relationships we can keep track of in a social network is dependent upon our current neocortex size. Using an equation developed to predict primate mean group size, the best-fit reduced major axis regression equation between neocortex ratio and mean group size, he finds a predicted group size of 147.8 (95% CI = 100.2-231.1). Dunbar himself admits that in using this equation he is “extrapolating well beyond the range of neocortex ratios on which it is based” [1], and therefore the large confidence interval was not unexpected. However, using other equations based on neocortex size, he found similar results ranging from 107.6 to 248.6.
