Cody T. Ross, Santa Fe Institute
Monique Borgerhoff Mulder, University of California, Davis
Seung-Yun Oh, Korea Insurance Research Institute
Samuel Bowles, Santa Fe Institute
Bret Beheim, Max Planck Institute for Evolutionary Anthropology
John Bunce, Max Planck Institute for Evolutionary Anthropology
Mark Caudell, Washington State University
Gregory Clark, University of California, Davis
Heidi Colleran, Max Planck Institute for the Science of Human History
Carmen Cortez, University of California, Davis
Patricia Draper, University of Nebraska - Lincoln
Russell D. Greaves, University of Utah
Michael Gurven, University of California, Santa Barbara
Thomas Headland, SIL International
Janet Headland, SIL International
Kim Hill, Arizona State University
Barry Hewlett, Washington State University
Hillard Kaplan, Chapman UniversityFollow
Jeremy Koster, University of Cincinnati
Karen Kramer, University of Utah
Frank Marlowe, University of Cambridge
Richard McElreath, University of California - Davis
David Nolin, Pennsylvania State University
Marsha Quinlan, Arizona State University
Robert Quinlan, Arizona State University
Caissa Revilla-Minaya, Vanderbilt University
Brooke Scelza, University of California, Los Angeles
Ryan Schacht, East Carolina University
Mary Shenk, Pennsylvania State University
Ray Uehara, SIL International
Eckart Voland, Universität Giessen
Kai Willführ, Carl von Ossietzky University of Oldenburg
Bruce Winterhalder, University of California, Davis
John Ziker, Boise State University
Christopher von Rueden, University of Richmond

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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.


This article was originally published in Journal of the Royal Society Interface, volume 15, issue 144, in 2018.

Peer Reviewed



The Royal Society

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Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.