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

<h4>Background</h4>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 stud...

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Autores principales:	Elissa Z Cameron, Fredrik Dalerum
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2009
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/795802c04dc64d809adbedf5444b929f
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spelling	oai:doaj.org-article:795802c04dc64d809adbedf5444b929f2021-11-25T06:17:47ZA Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires.1932-620310.1371/journal.pone.0004195https://doaj.org/article/795802c04dc64d809adbedf5444b929f2009-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/19142225/?tool=EBIhttps://doaj.org/toc/1932-6203<h4>Background</h4>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.<h4>Methodology/principal findings</h4>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.<h4>Conclusions/significance</h4>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.Elissa Z CameronFredrik DalerumPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 4, Iss 1, p e4195 (2009)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Elissa Z Cameron Fredrik Dalerum A Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires.
description	<h4>Background</h4>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.<h4>Methodology/principal findings</h4>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.<h4>Conclusions/significance</h4>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.
format	article
author	Elissa Z Cameron Fredrik Dalerum
author_facet	Elissa Z Cameron Fredrik Dalerum
author_sort	Elissa Z Cameron
title	A Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires.
title_short	A Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires.
title_full	A Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires.
title_fullStr	A Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires.
title_full_unstemmed	A Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires.
title_sort	trivers-willard effect in contemporary humans: male-biased sex ratios among billionaires.
publisher	Public Library of Science (PLoS)
publishDate	2009
url	https://doaj.org/article/795802c04dc64d809adbedf5444b929f
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A Trivers-Willard effect in contemporary humans: male-biased sex ratios among billionaires.

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