Routes to Language





Larger Social Groups


Meaningful Signals

Machiavellian Intelligence

Likely Emergence:


About 3 million years ago


Extended Childhood


References and other reading

Aiello, L. and Dunbar, R., 1993. Neocortex Size, Group Size, and the Evolution of Language. Current Anthropology, 34(2), pp.184-193.

Byrne, R., 2000. Evolution of Primate Cognition. Cognitive Science, 24(3), pp.543-570.

Dávid-Barrett, T. and Dunbar, R., 2013. Processing power limits social group size: computational evidence for the cognitive costs of sociality. Proceedings of the Royal Society B: Biological Sciences, 280(1765), p.1.

Grove, M., 2011. Space, time, and group size: a model of constraints on primate social foraging. Animal Behaviour, 83(2), pp.411-419.

Hammel, E., 2005. Kinship-based politics and the optimal size of kin groups. Proceedings of the National Academy of Sciences, 102(33), pp.11951-11956.

Lehmann, J., Korstjens, A. and Dunbar, R., 2007. Group size, grooming and social cohesion in primates. Animal Behaviour, 74(6), pp.1617-1629.

Pagel, M., 2011. How Language Transformed Humanity. [, Accessed Mar. 2020.]


'Larger Social Groups' refers to the phenomenon of a number of primate species, including the Australopithecus, living and socialising in groups with an increasingly large number of individuals. More specifically, Aiello & Dunbar (1993) maintain that the upper limit of individuals that can exist in an average hunter-gatherer Australopithecine group is about 66.  After this, it becomes likely that members will not be able to budget enough time to maintain social bonds and it is necessary for the group to split up into subgroups. (Lehmann, Korstkjens & Dunbar, 2007). E.A. Hammel (2005) refers to this as a process of fission and fusion which demonstrates a 'Malthusian effect'. Simply, this means that large social groups may no longer be efficient for species beyond a point.


Research using simulated models of human behaviour have shown that "increases in the kinds of information processed allow organisms to break through glass ceilings that otherwise limit social groups". (David-Barrett, 2013, p.1). This is due to what David-Barrett identifies as the Social Complexity Hypothesis, where the kinds of information which can be processed in the brain limit group size. Therefore, a higher demand for communicative complexity leads to more sophisticated cognitive strategies, which is turn facilitate larger groups. Larger groups demand more complex communication, as all members must be co-ordinated when grooming, scavenging and surviving predation. This leads to increased encephalisation and specifically, a larger neocortex in mammal brains. (David-Barrett, op cit). Consequently, this creates a bidirectional relationship between group size and neocortex ratio.


However, recent literature has identified other variables limiting group size. Grove (2011) argues that group size is largely determined by the group's ability to forage for food (Ecological Constraint Hypothesis) and also by Dunbar's theory of time constraints. (Aiello & Dunbar, op cit). Grove concludes that group size will inevitably be affected by one of these variables, or there is a risk of group fission. Therefore, it would appear that larger groups can be costly and evolve differently depending on the species.


Nevertheless, Aiello & Dunbar (Ibid) found group size and neocortex ratio to increase linearly from Australopithecus, across early homo species. This coincided with the development of communicative readiness in archaic Homo Sapiens, such as a low larynx and Machiavellian Intelligence. (Byrne, 2000). This likely resulted in the ability for Homo Sapiens to produce meaningful signals, which evolutionary biologist Mark Pagel (2011) refers to as "the most powerful, dangerous and subversive trait that natural selection has ever devised".


While there is current debate surrounding other species' abilities to use language, it appears likely that further research on changes in group sizes across other mammals over time would be enlightening.


Christina Sharpless, 2020