Hierarchical social modularity in gorillas

Bibliographic Collection: 
Publication Type: Journal Article
Authors: Morrison Robin E.; Groenenberg Milou; Breuer Thomas; Manguette Marie L.; Walsh Peter D.
Year of Publication: 2019
Journal: Proceedings of the Royal Society B: Biological Sciences
Volume: 286
Issue: 1906
Pagination: 20190681
Date Published: 2019/07/10
Publication Language: eng

Modern human societies show hierarchical social modularity (HSM) in which lower-order social units like nuclear families are nested inside increasingly larger units. It has been argued that this HSM evolved independently and after the chimpanzee–human split due to greater recognition of, and bonding between, dispersed kin. We used network modularity analysis and hierarchical clustering to quantify community structure within two western lowland gorilla populations. In both communities, we detected two hierarchically nested tiers of social structure which have not been previously quantified. Both tiers map closely to human social tiers. Genetic data from one population suggested that, as in humans, social unit membership was kin structured. The sizes of gorilla social units also showed the kind of consistent scaling ratio between social tiers observed in humans, baboons, toothed whales, and elephants. These results indicate that the hierarchical social organization observed in humans may have evolved far earlier than previously asserted and may not be a product of the social brain evolution unique to the hominin lineage.


doi: 10.1098/rspb.2019.0681

DOI: https://doi.org/10.1098/rspb.2019.0681
Short Title: Proceedings of the Royal Society B: Biological Sciences