The social brain: scale-invariant layering of Erdős-Rényi networks in small-scale human societies

Michael S. Harré*, Mikhail Prokopenko

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


The cognitive ability to form social links that can bind individuals together into large cooperative groups for safety and resource sharing was a key development in human evolutionary and social history. The 'social brain hypo' argues that the size of these social groups is based on a neurologically constrained capacity for maintaining long-term stable relationships. No model to date has been able to combine a specific socio-cognitive mechanism with the discrete scale invariance observed in ethnographic studies. We show that these properties result in nested layers of self-organizing Erdos-Rényi networks formed by each individual's ability to maintain only a small number of social links. Each set of links plays a specific role in the formation of different social groups. The scale invariance in our model is distinct from previous 'scale-free networks' studied using much larger social groups; here, the scale invariance is in the relationship between group sizes, rather than in the link degree distribution. We also compare our model with a dominance-based hierarchy and conclude that humans were probably egalitarian in hunter- gatherer-like societies, maintaining an average maximum of four or five social links connecting all members in a largest social network of around 132 people.

Original languageEnglish
Article number20160044
Pages (from-to)1-6
Number of pages6
JournalJournal of the Royal Society Interface
Issue number118
Publication statusPublished - 1 May 2016
Externally publishedYes


  • Erdos-Rényi networks
  • social networks
  • discrete scale invariance
  • social brain hypothesis


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