Article

The social and cultural roots of whale and dolphin brains

  • Nature Ecology & Evolution 116991705 (2017)
  • doi:10.1038/s41559-017-0336-y
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Abstract

Encephalization, or brain expansion, underpins humans’ sophisticated social cognition, including language, joint attention, shared goals, teaching, consensus decision-making and empathy. These abilities promote and stabilize cooperative social interactions, and have allowed us to create a ‘cognitive’ or ‘cultural’ niche and colonize almost every terrestrial ecosystem. Cetaceans (whales and dolphins) also have exceptionally large and anatomically sophisticated brains. Here, by evaluating a comprehensive database of brain size, social structures and cultural behaviours across cetacean species, we ask whether cetacean brains are similarly associated with a marine cultural niche. We show that cetacean encephalization is predicted by both social structure and by a quadratic relationship with group size. Moreover, brain size predicts the breadth of social and cultural behaviours, as well as ecological factors (diversity of prey types and to a lesser extent latitudinal range). The apparent coevolution of brains, social structure and behavioural richness of marine mammals provides a unique and striking parallel to the large brains and hyper-sociality of humans and other primates. Our results suggest that cetacean social cognition might similarly have arisen to provide the capacity to learn and use a diverse set of behavioural strategies in response to the challenges of social living.

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Acknowledgements

We thank R. Sears of the Mingan Island Cetacean Study for early encouragement of this work. K.C.R.F. is supported by a postdoctoral fellowship from the Natural Sciences and Engineering Research Council of Canada; S.S. is supported by a Royal Society University Research Fellowship (UF110641).

Author information

Author notes

  1. Kieran C. R. Fox and Michael Muthukrishna contributed equally to this work.

Affiliations

  1. Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, 94305, USA

    • Kieran C. R. Fox
  2. Department of Psychological and Behavioural Science, London School of Economics and Political Science, London, WC2A 2AE, UK

    • Michael Muthukrishna
  3. Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA

    • Michael Muthukrishna
  4. School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK

    • Susanne Shultz

Authors

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Contributions

K.C.R.F., M.M. and S.S. conceived the project and wrote the manuscript. K.C.R.F. and M.M. collated the data, with some assistance from S.S. S.S. primarily conducted statistical analyses, with some assistance from M.M. and K.C.R.F.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Susanne Shultz.

Electronic supplementary material

  1. Supplementary Information

    Supplementary Figures 1–7; Supplementary Tables 3–8.

  2. Supplementary Table 1

    Main database of basic cetacean physical and social data.

  3. Supplementary Table 2

    Database of cetacean social and prosocial behaviour.