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Dalzero A, Beheim BA, Kaplan H, Stieglitz J, Hooper PL, Ross CT, Gurven M, Lukas D. Cross-cousin marriage among Tsimane forager-horticulturalists during demographic transition and market integration. Evol Hum Sci 2024; 6:e18. [PMID: 38572226 PMCID: PMC10988167 DOI: 10.1017/ehs.2024.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 02/02/2024] [Accepted: 02/12/2024] [Indexed: 04/05/2024] Open
Abstract
Although still prevalent in many human societies, the practice of cousin marriage has precipitously declined in populations undergoing rapid demographic and socioeconomic change. However, it is still unclear whether changes in the structure of the marriage pool or changes in the fitness-relevant consequences of cousin marriage more strongly influence the frequency of cousin marriage. Here, we use genealogical data collected by the Tsimane Health and Life History Project to show that there is a small but measurable decline in the frequency of first cross-cousin marriage since the mid-twentieth century. Such changes are linked to concomitant changes in the pool of potential spouses in recent decades. We find only very modest differences in fitness-relevant demographic measures between first cousin and non-cousin marriages. These differences have been diminishing as the Tsimane have become more market integrated. The factors that influence preferences for cousin marriage appear to be less prevalent now than in the past, but cultural inertia might slow the pace of change in marriage norms. Overall, our findings suggest that cultural changes in marriage practices reflect underlying societal changes that shape the pool of potential spouses.
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Affiliation(s)
- Arianna Dalzero
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Bret A. Beheim
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Hillard Kaplan
- Economic Science Institute, Chapman University, Orange, California, USA
| | - Jonathan Stieglitz
- Toulouse School of Economics and Institute for Advanced Study, University of Toulouse 1 Capitole, Toulouse, France
| | - Paul L. Hooper
- Economic Science Institute, Chapman University, Orange, California, USA
- Department of Anthropology, University of New Mexico, Albuquerque, New Mexico, USA
| | - Cody T. Ross
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Michael Gurven
- Department of Anthropology, University of California, Santa Barbara, California, USA
| | - Dieter Lukas
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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