@article{4ce025e58413429f88e8e1252a5d3239,
title = "Greater wealth inequality, less polygyny: Rethinking the polygyny threshold model",
abstract = "Monogamy appears to have become the predominant human mating system with the emergence of highly unequal agricultural populations that replaced relatively egalitarian horticultural populations, challenging the conventional idea - based on the polygyny threshold model - that polygyny should be positively associated with wealth inequality. To address this polygyny paradox, we generalize the standard polygyny threshold model to a mutual mate choice model predicting the fraction of women married polygynously. We then demonstrate two conditions that are jointly sufficient to make monogamy the predominant marriage form, even in highly unequal societies. We assess if these conditions are satisfied using individual-level data from 29 human populations. Our analysis shows that with the shift to stratified agricultural economies: (i) the population frequency of relatively poor individuals increased, increasing wealth inequality, but decreasing the frequency of individuals with sufficient wealth to secure polygynous marriage, and (ii) diminishing marginal fitness returns to additional wives prevent extremely wealthy men from obtaining as many wives as their relative wealth would otherwise predict. These conditions jointly lead to a high population-level frequency of monogamy.",
keywords = "Polygyny, behavioural ecology, evolutionary anthropology, marriage systems, monogamy, wealth inequality",
author = "Ross, {Cody T.} and Mulder, {Monique Borgerhoff} and Oh, {Seung Yun} and Samuel Bowles and Bret Beheim and John Bunce and Mark Caudell and Gregory Clark and Heidi Colleran and Carmen Cortez and Patricia Draper and Greaves, {Russell D.} and Michael Gurven and Thomas Headland and Janet Headland and Kim Hill and Barry Hewlett and Kaplan, {Hillard S.} and Jeremy Koster and Karen Kramer and Frank Marlowe and Richard McElreath and David Nolin and Marsha Quinlan and Robert Quinlan and Caissa Revilla-Minaya and Brooke Scelza and Ryan Schacht and Mary Shenk and Ray Uehara and Eckart Voland and Kai Willfuhr and Bruce Winterhalder and John Ziker",
note = "Funding Information: Data accessibility. Interested readers can replicate our analysis using the model code and data included with this submission. This code and database will be maintained at: https://github.com/ctross/publications/polygynypuzzle. Analysis is conducted using R [81] and RStan [82]. Authors{\textquoteright} contributions. C.T.R., S.-Y.O., S.B. and M.B.M. designed the study, C.T.R. developed the statistical models and analysed the data, B.B. checked and re-factored the statistical code, S.B. and M.B.M. managed the data collection team, and C.T.R., S.Y.O., S.B. and M.B.M. wrote the paper. All other listed authors contributed data and edited the paper. Competing interests. The authors declare that they have no competing financial interests. Funding. This research was supported by the Dynamics of Wealth Inequality project of the Behavioral Sciences Program at the Santa Fe Institute, the United States National Science Foundation (NSF-IBSS grant no. 1329089) and the Max Planck Institute for Evolutionary Anthropology, Department of Human Behavior, Ecology and Culture. Acknowledgements. We acknowledge the cooperation, generosity and friendship of individuals in the communities among whom we conduct research. We thank the three anonymous reviewers for their suggestions that improved the quality of this paper. Members of the workshops on Dynamics of Wealth Inequality and Family",
year = "2018",
month = jul,
day = "1",
doi = "10.1098/rsif.2018.0035",
language = "English (US)",
volume = "15",
journal = "Journal of the Royal Society Interface",
issn = "1742-5689",
publisher = "Royal Society of London",
number = "144",
}