Letter | Published:

Social networks and cooperation in hunter-gatherers

Nature 481, 497–501 (26 January 2012) | Download Citation

Subjects

Abstract

Social networks show striking structural regularities1,2, and both theory and evidence suggest that networks may have facilitated the development of large-scale cooperation in humans3,4,5,6,7. Here, we characterize the social networks of the Hadza, a population of hunter-gatherers in Tanzania8. We show that Hadza networks have important properties also seen in modernized social networks, including a skewed degree distribution, degree assortativity, transitivity, reciprocity, geographic decay and homophily. We demonstrate that Hadza camps exhibit high between-group and low within-group variation in public goods game donations. Network ties are also more likely between people who give the same amount, and the similarity in cooperative behaviour extends up to two degrees of separation. Social distance appears to be as important as genetic relatedness and physical proximity in explaining assortativity in cooperation. Our results suggest that certain elements of social network structure may have been present at an early point in human history. Also, early humans may have formed ties with both kin and non-kin, based in part on their tendency to cooperate. Social networks may thus have contributed to the emergence of cooperation.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

Rent or Buy

All prices are NET prices.

References

  1. 1.

    et al. Structure and tie strengths in mobile communication networks. Proc. Natl Acad. Sci. USA 104, 7332–7336 (2007)

  2. 2.

    & Emergence of scaling in random networks. Science 286, 509–512 (1999)

  3. 3.

    , & The evolution of eusociality. Nature 466, 1057–1062 (2010)

  4. 4.

    & The evolution of reciprocity in sizable groups. J. Theor. Biol. 132, 337–356 (1988)

  5. 5.

    & Assortment of encounters and evolution of cooperativeness. Proc. Natl Acad. Sci. USA 79, 1331–1335 (1982)

  6. 6.

    Group competition, reproductive levelling, and the evolution of human altruism. Science 314, 1569–1572 (2006)

  7. 7.

    , , & A simple rule for the evolution of cooperation on graphs and social networks. Nature 441, 502–505 (2006)

  8. 8.

    The Hadza: Hunter-gatherers of Tanzania (University of California Press, 2010)

  9. 9.

    Friendship: Development, Ecology, and Evolution of a Relationship (University of California Press, 2010)

  10. 10.

    & Why culture is common but cultural evolution is rare. Proc. Br. Acad. 88, 73–93 (1996)

  11. 11.

    & The impact of network clustering and assortativity on epidemic behaviour. Theor. Popul. Biol. 77, 71–75 (2010)

  12. 12.

    Empathy and altruism. J. Pers. Soc. Psychol. 32, 1134–1146 (1975)

  13. 13.

    , & Model of genetic variation in human social networks. Proc. Natl Acad. Sci. USA 106, 1720–1724 (2009)

  14. 14.

    , & Correlated genotypes in friendship networks. Proc. Natl Acad. Sci. USA 108, 1993–1997 (2011)

  15. 15.

    & The evolution of indirect reciprocity. Soc. Networks 11, 213–236 (1989)

  16. 16.

    & The evolution of strong reciprocity: cooperation in heterogeneous populations. Theor. Popul. Biol. 65, 17–28 (2004)

  17. 17.

    et al. The complex structure of hunter–gatherer social networks. Proc. R. Soc. Lond. B 274, 2195–2203 (2007)

  18. 18.

    et al. Co-residence patterns in hunter-gatherer societies show unique human social structure. Science 331, 1286–1289 (2011)

  19. 19.

    , & From forest to reservation: transitions in food sharing behavior among the Ache of Paraguay. J. Anthropol. Res. 58, 93–120 (2002)

  20. 20.

    , , , & Geographic constraints on social network groups. PLoS ONE 6, e16939 (2011)

  21. 21.

    et al. Wealth transmission and inequality among hunter-gatherers. Curr. Anthropol. 51, 19–34 (2010)

  22. 22.

    & The nature of human altruism. Nature 425, 785–791 (2003)

  23. 23.

    Clustering and hierarchy in inter-personal relations: testing two graph theoretical models in 742 sociomatrices. Am. Sociol. Rev. 35, 843–851 (1970)

  24. 24.

    & in Moral Sentiments and Material Interests: The Foundations of Cooperation in Economic Life (eds , , & ) 75–113 (MIT Press, 2005)

  25. 25.

    & Non-zero-sum collaboration. reciprocity, and the preference for similarity: developing an adaptive model of close relational functioning. Personal Relationships 11, 135–160 (2004)

  26. 26.

    , & Social network analysis in the study of nonhuman primates: a historical perspective. Am. J. Primatol. 73, 720–730 (2011)

  27. 27.

    Analyzing Animal Societies: Quantitative Methods for Vertebrate Social Analysis (University of Chicago Press, 2008)

  28. 28.

    Five rules for the evolution of cooperation. Science 314, 1560–1563 (2006)

  29. 29.

    , & Dynamic social networks promote cooperation in experiments with humans. Proc. Natl Acad. Sci. USA 108, (2011)

  30. 30.

    & Cooperative behavior cascades in human social networks. Proc. Natl Acad. Sci. USA 107, 5334–5338 (2010)

  31. 31.

    & Sex differences in food preferences of Hadza hunter-gatherers. Evol. Psychol. 7, 601–616 (2009)

  32. 32.

    et al. In search of Homo economicus: behavioral experiments in 15 small-scale societies. Am. Econ. Rev. 91, 73–78 (2001)

  33. 33.

    & Name generators in surveys of personal networks. Soc. Networks 13, 203–221 (1991)

  34. 34.

    , & Hadza meat sharing. Evol. Hum. Behav. 22, 113–142 (2001)

  35. 35.

    in Hunter Gatherers Vol. 1 History, Evolution and Social Change (eds , & ) 222–251 (Berg, 1988)

  36. 36.

    & Longitudinal data analysis using generalized linear models. Biometrika 73, 13–22 (1986)

  37. 37.

    Regression analysis of longitudinal binary data with time-dependent environmental covariates: bias and efficiency. Biostatistics 6, 633–652 (2005)

Download references

Acknowledgements

This work was supported by grant P01-AG031093 from the National Institute on Aging and by the Science of Generosity Initiative of the University of Notre Dame (supported by the John Templeton Foundation). We are grateful for comments from S. Bowles, D. Eisenberg, F. Fu, H. Gintis, J. Henrich, P. Hooper, D. Hruschka, M. Nowak, D. Rand, P. Richerson and C. Tarnita. We thank A. Mabulla, I. Mabulla, M. Peterson, C. Bauchner and L. Meneades for help with data collection and preparation. We are grateful to D. Stafford and A. Hughes for sharing data regarding two villages in Honduras, as used in the Supplementary Information.

Author information

Affiliations

  1. Institute for Quantitative Social Science, Harvard University, Cambridge, Massachusetts 02138, USA

    • Coren L. Apicella
    •  & Nicholas A. Christakis

  2. Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts 02115, USA

    • Coren L. Apicella
    •  & Nicholas A. Christakis

  3. Department of Anthropology, Cambridge University, Cambridge, CB2 3DZ, UK

    • Frank W. Marlowe

  4. Medical Genetics Division, University of California, San Diego, California 92093, USA

    • James H. Fowler

  5. Political Science Department, University of California, San Diego, California 92093, USA

    • James H. Fowler

  6. Department of Sociology, Harvard University, Cambridge, Massachusetts 02138, USA

    • Nicholas A. Christakis

  7. Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA

    • Nicholas A. Christakis

Authors

  1. Search for Coren L. Apicella in:

  2. Search for Frank W. Marlowe in:

  3. Search for James H. Fowler in:

  4. Search for Nicholas A. Christakis in:

Contributions

C.L.A., J.H.F. and N.A.C. designed the study and experiments. C.L.A. and F.W.M. collected data. C.L.A., J.H.F. and N.A.C. analysed the data. C.L.A., J.H.F. and N.A.C. wrote the manuscript. F.W.M. provided technical support. J.H.F. and N.A.C. secured funding.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Nicholas A. Christakis.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains Supplementary Methods, Supplementary Statistics and Results, Supplementary Tables 1-51, Supplementary Figures 1-13 with legends and Supplementary References.

Videos

  1. 1.

    Supplementary Movie 1

    This file contains a 3-D movie of the male and female campmate social networks - see page 9 of the Supplementary Information file for full legend.

  2. 2.

    Supplementary Movie 2

    This file contains a 3-D movie of the male and female campmate social networks - see page 9 of the Supplementary Information file for full legend.

To obtain permission to re-use content from this article visit RightsLink.

About this article

Publication history

Received

Accepted

Published

DOI

https://doi.org/10.1038/nature10736

Further reading Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.