Revisiting a sample of U.S. billionaires: how sample selection and timing of maternal condition influence findings on the Trivers-Willard effect.

Based on evolutionary theory, Trivers & Willard (TW) predicted the existence of mechanisms that lead parents with high levels of resources to bias offspring sex composition to favor sons and parents with low levels of resources to favor daughters. This hypothesis has been tested in samples of we...

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Autor principal:	Sebastian Schnettler
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2013
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/d38e8d77bf434de6adb676c492958f0b
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spelling	oai:doaj.org-article:d38e8d77bf434de6adb676c492958f0b2021-11-18T07:56:29ZRevisiting a sample of U.S. billionaires: how sample selection and timing of maternal condition influence findings on the Trivers-Willard effect.1932-620310.1371/journal.pone.0057446https://doaj.org/article/d38e8d77bf434de6adb676c492958f0b2013-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/23437389/pdf/?tool=EBIhttps://doaj.org/toc/1932-6203Based on evolutionary theory, Trivers & Willard (TW) predicted the existence of mechanisms that lead parents with high levels of resources to bias offspring sex composition to favor sons and parents with low levels of resources to favor daughters. This hypothesis has been tested in samples of wealthy individuals but with mixed results. Here, I argue that both sample selection due to a high number of missing cases and a lacking specification of the timing of wealth accumulation contribute to this equivocal pattern. This study improves on both issues: First, analyses are based on a data set of U.S. billionaires with near-complete information on the sex of offspring. Second, subgroups of billionaires are distinguished according to the timing when they acquired their wealth. Informed by recent insights on the timing of a potential TW effect in animal studies, I state two hypotheses. First, billionaires have a higher share of male offspring than the general population. Second, this effect is larger for heirs and heiresses who are wealthy at the time of conception of all of their children than for self-made billionaires who acquired their wealth during their adult lives, that is, after some or all of their children have already been conceived. Results do not support the first hypothesis for all subgroups of billionaires. But for males, results are weakly consistent with the second hypothesis: Heirs but not self-made billionaires have a higher share of male offspring than the U.S. population. Heiresses, on the other hand, have a much lower share of male offspring than the U.S. average. This hints to a possible interplay of at least two mechanisms affecting sex composition. Implications for future research that would allow disentangling the distinct mechanisms are discussed.Sebastian SchnettlerPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 8, Iss 2, p e57446 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Sebastian Schnettler Revisiting a sample of U.S. billionaires: how sample selection and timing of maternal condition influence findings on the Trivers-Willard effect.
description	Based on evolutionary theory, Trivers & Willard (TW) predicted the existence of mechanisms that lead parents with high levels of resources to bias offspring sex composition to favor sons and parents with low levels of resources to favor daughters. This hypothesis has been tested in samples of wealthy individuals but with mixed results. Here, I argue that both sample selection due to a high number of missing cases and a lacking specification of the timing of wealth accumulation contribute to this equivocal pattern. This study improves on both issues: First, analyses are based on a data set of U.S. billionaires with near-complete information on the sex of offspring. Second, subgroups of billionaires are distinguished according to the timing when they acquired their wealth. Informed by recent insights on the timing of a potential TW effect in animal studies, I state two hypotheses. First, billionaires have a higher share of male offspring than the general population. Second, this effect is larger for heirs and heiresses who are wealthy at the time of conception of all of their children than for self-made billionaires who acquired their wealth during their adult lives, that is, after some or all of their children have already been conceived. Results do not support the first hypothesis for all subgroups of billionaires. But for males, results are weakly consistent with the second hypothesis: Heirs but not self-made billionaires have a higher share of male offspring than the U.S. population. Heiresses, on the other hand, have a much lower share of male offspring than the U.S. average. This hints to a possible interplay of at least two mechanisms affecting sex composition. Implications for future research that would allow disentangling the distinct mechanisms are discussed.
format	article
author	Sebastian Schnettler
author_facet	Sebastian Schnettler
author_sort	Sebastian Schnettler
title	Revisiting a sample of U.S. billionaires: how sample selection and timing of maternal condition influence findings on the Trivers-Willard effect.
title_short	Revisiting a sample of U.S. billionaires: how sample selection and timing of maternal condition influence findings on the Trivers-Willard effect.
title_full	Revisiting a sample of U.S. billionaires: how sample selection and timing of maternal condition influence findings on the Trivers-Willard effect.
title_fullStr	Revisiting a sample of U.S. billionaires: how sample selection and timing of maternal condition influence findings on the Trivers-Willard effect.
title_full_unstemmed	Revisiting a sample of U.S. billionaires: how sample selection and timing of maternal condition influence findings on the Trivers-Willard effect.
title_sort	revisiting a sample of u.s. billionaires: how sample selection and timing of maternal condition influence findings on the trivers-willard effect.
publisher	Public Library of Science (PLoS)
publishDate	2013
url	https://doaj.org/article/d38e8d77bf434de6adb676c492958f0b
work_keys_str_mv	AT sebastianschnettler revisitingasampleofusbillionaireshowsampleselectionandtimingofmaternalconditioninfluencefindingsonthetriverswillardeffect
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Revisiting a sample of U.S. billionaires: how sample selection and timing of maternal condition influence findings on the Trivers-Willard effect.

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