Life-history theory suggests that the level of fecundity of each organism reflects the effect of the trade-off between the quantity and quality of offspring on its long-run reproductive success. The present research provides evidence that moderate fecundity was conducive to long-run reproductive success in humans. Using a reconstructed genealogy for nearly half a million individuals in Quebec during the 1608–1800 period, the study establishes that, while high fecundity was associated with a larger number of children, perhaps paradoxically, moderate fecundity maximized the number of descendants after several generations. Moreover, the analysis further suggests that evolutionary forces decreased the level of fecundity in the population over this period, consistent with an additional finding that the level of fecundity that maximized long-run reproductive success was below the population mean. The research identifies several mechanisms that contributed to the importance of moderate fecundity for long-run reproductive success. It suggests that, while individuals with lower fecundity had fewer children, the observed hump-shaped effect of fecundity on long-run reproductive success reflects the beneficial effects of lower fecundity on various measures of child quality, such as marriageability and literacy, and thus on the reproductive success of each child.
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The data that support the findings of this study are available from PRDH at the University of Montreal. Restrictions apply to the availability of these data, which were used under license. They are available from the authors upon reasonable request and with permission of PRDH.
The statistical code is available from the authors upon request.
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The data were collected and kindly provided by ‘Le Programme de Recherche en Démographie Historique’ (PRDH) at the University of Montreal. The authors are grateful to B. Desjardins for sharing the data and providing helpful information. Part of this research was conducted while M.K. was a visiting assistant professor at Brown University and a visiting scholar at Harvard University, and funded by the Carlsberg Foundation, the Danish Research Council (reference numbers 1329–00093 and 1327–00245) and the European Union’s Horizon 2020 research and innovation programme (Marie Skłodowska-Curie grant agreement number 753615).
The authors declare no competing interests.
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These authors contributed equally: Oded Galor, Marc Klemp.
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Galor, O., Klemp, M. Human genealogy reveals a selective advantage to moderate fecundity. Nat Ecol Evol 3, 853–857 (2019). https://doi.org/10.1038/s41559-019-0846-x
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