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A Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires

Citation

Cameron, EZ and Dalerum, F, A Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires , PLoS One, 4, (1:e4195) pp. 1-4. ISSN 1932-6203 (2009) [Refereed Article]

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Copyright Statement

Copyright: 2009 Cameron et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

DOI: doi:10.1371/journal.pone.0004195

Abstract

Background Natural selection should favour the ability of mothers to adjust the sex ratio of offspring in relation to the offspring's potential reproductive success. In polygynous species, mothers in good condition would be advantaged by giving birth to more sons. While studies on mammals in general provide support for the hypothesis, studies on humans provide particularly inconsistent results, possibly because the assumptions of the model do not apply. Methodology/Principal Findings Here, we take a subset of humans in very good condition: the Forbe's billionaire list. First, we test if the assumptions of the model apply, and show that mothers leave more grandchildren through their sons than through their daughters. We then show that billionaires have 60% sons, which is significantly different from the general population, consistent with our hypothesis. However, women who themselves are billionaires have fewer sons than women having children with billionaires, suggesting that maternal testosterone does not explain the observed variation. Furthermore, paternal masculinity as indexed by achievement, could not explain the variation, since there was no variation in sex ratio between self-made or inherited billionaires. Conclusions/Significance Humans in the highest economic bracket leave more grandchildren through sons than through daughters. Therefore, adaptive variation in sex ratios is expected, and human mothers in the highest economic bracket do give birth to more sons, suggesting similar sex ratio manipulation as seen in other mammals.

Item Details

Item Type:Refereed Article
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Behavioural Ecology
Objective Division:Environment
Objective Group:Flora, Fauna and Biodiversity
Objective Field:Sparseland, Permanent Grassland and Arid Zone Flora, Fauna and Biodiversity
Author:Cameron, EZ (Professor Elissa Cameron)
ID Code:67476
Year Published:2009
Web of Science® Times Cited:28
Deposited By:Zoology
Deposited On:2011-03-04
Last Modified:2011-03-11
Downloads:227 View Download Statistics

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