Zefferman, M. R. and Mathew, S. (2026). Intergroup violence without essentialist beliefs: the case of Turkana cattle raiders. In Wagner, W., and Moya, C., eds, Culture, Identity, and Essentialism: Anthropological and Psychological Approaches, pages 289–311. Springer Nature. [DOI] [PDF]

Zefferman, M. R., Baumgarten, M. D., Trumble, B. C., and Mathew, S. (2025). Little evidence that posttraumatic stress is associated with diurnal hormone dysregulation in Turkana pastoralists. Evolution, Medicine, and Public Health, 13(1):77–91. [DOI] [PDF]

Smaldino, P. E., Russell, A., Zefferman, M. R., Donath, J., Foster, J. G., Guilbeault, D., Hilbert, M., Hobson, E. A., Lerman, K., Miton, H., Moser, C., Lasser, J., Schmer-Galunder, S., Shapiro, J. N., Zhong, Q., and Patt, D. (2025). Information architectures: a framework for understanding socio-technical systems. npj Complexity, 2(1):1–11. [DOI] [PDF]

* Zefferman, M. R. and Smaldino, P. E. (2024). Historical myths define group boundaries: a mathematical sketch and evidence from Ukraine. Behavioral and Brain Sciences, 47:e196.[DOI] [PDF] [commentary on Sijilmassi et al]

* Mathew, S. and Zefferman, M. R. (2024). Group-structured cultural selection can explain both war and peace. Behavioral and Brain Sciences, 47:e18. [DOI] [commentary on Glowacki]

Zefferman, M. R. (2023). Constraints on cooperation shape hierarchical versus distributed structure in human groups. Scientific Reports, 13(1):1160. [DOI] [PDF]

Zefferman, M. R. and Mathew, S. (2021). Combat stress in a small-scale society suggests divergent evolutionary roots for posttraumatic stress disorder symptoms. Proceedings of the National Academy of Sciences, 118(15):e2020430118. [DOI] [PDF]

* Zefferman, M. R. and Smaldino, P. E. (2020). Integrating models of cognition and culture will require a bit more math. Behavioral and Brain Sciences, 43:e119. [DOI] [commentary on Veissière et al]

Zefferman, M. R. and Mathew, S. (2020). An evolutionary theory of moral injury with insight from Turkana warriors. Evolution and Human Behavior, 41(5):341–353. [DOI] [PDF]

Zefferman, M. R. (2018). Cultural multilevel selection suggests neither large nor small cooperative agreements are likely to solve climate change without changing the game. Sustainability Science, 13(1):109–118. [DOI] [PDF]

Zefferman, M. R. (2016). Mothers teach daughters because daughters teach granddaughters: the evolution of sex-biasedtransmission. Behavioral Ecology, 27(4):1172–1181. [DOI] [PDF]

* Richerson, P., Baldini, R., Bell, A. V., Demps, K., Frost, K., Hillis, V., Mathew, S., Newton, E. K., Naar, N., Newson, L., Ross, C., Smaldino, P. E., Waring, T. M., and Zefferman, M. R. (2016). Cultural group selection follows Darwin’s classic syllogism for the operation of selection. Behavioral and Brain Sciences, 39:e58. [DOI] [authors’ response]

Richerson, P., Baldini, R., Bell, A. V., Demps, K., Frost, K., Hillis, V., Mathew, S., Newton, E. K., Naar, N., Newson, L., Ross, C., Smaldino, P. E., Waring, T. M., and Zefferman, M. R. (2016). Cultural group selection plays an essential role in explaining human cooperation: a sketch of the evidence. Behavioral and Brain Sciences, 39:e30. [DOI] [PDF] [Target article]

* Zefferman, M. R., Baldini, R., and Mathew, S. (2015). Solving the puzzle of human warfare requires an explanation of battle raids and cultural institutions. Proceedings of the National Academy of Sciences, 112(20):E2557–E2557. [DOI] [PDF] [letter on Glowacki and Wrangham]

Zefferman, M. R. and Mathew, S. (2015). An evolutionary theory of large-scale human warfare: Group-structured cultural selection. Evolutionary Anthropology: Issues, News, and Reviews, 24(2):50–61. [DOI][PDF]

* Zefferman, M. R. and Richerson, P. J. (2014). Many important group-level traits are institutions. Behavioral and Brain Sciences, 37(3):280–281. [DOI][PDF] [commentary on Smaldino]

* Zefferman, M. R. (2014). When repentance and forgiveness are possible, direct reciprocity does not explain one-shot generosity, even under arbitrarily high levels of uncertainty. Evolution and Human Behavior, 35(6):548–549. [DOI] [response to Delton and Krasnow]

Zefferman, M. R. (2014). Direct reciprocity under uncertainty does not explain one-shot cooperation, but demonstrates the benefits of a norm psychology. Evolution and Human Behavior, 35(5):358–367. [DOI][PDF]

* Zefferman, M. R. (2013). Should the consensus be essentialist and adaptationist? A commentary on David Sloan Wilson. Cliodynamics, 4(1):120-122. [DOI] [commentary on Wilson]

Zimmerman, M. R., McElreath, R., and Richerson, P. J. (2012). The Evolution of Cooperation. In Hastings, A. and Gross, L., eds, The Encyclopedia of Theoretical Ecology, pages 155–162. University of California Press. [Link]

Olabi, A., Hunter, J., Jackson, P., Segal, M., Spies, R., Wang, C., Lau, C., Ong, C., Alexander, C., Raskob, E., Plichta, J., Zeira, O., Rivera, R., Wang, S., Pottle, B., Leung, C., Vicens, C., Tao, C., Beers, C., Fung, G., Levine, J., Yoo, J., Jackson, J., Saikkonen, K., Zimmerman, M., Cunningham, M., Crum, M., Ishman, N., Voo, N., Cadena, R., Relinger, R., and Wada, S.(2003). Work measurement for estimating food preparation time of a bioregenerative diet. Habitation, 9(1):17–30. [DOI]

Pimentel, D., Herz, M., Glickstein, M., Zimmerman, M., Allen, R., Becker, K., Evans, J., Hussain, B., Sarsfeld, R., Grosfeld, A., and Seidel, T. (2002). Renewable energy: current and potential issues. BioScience, 52(12):1111–1120. [DOI][PDF]

* – Commentaries, letters, and authors’ responses.