Sex ratios at birth vary with environmental harshness but not maternal condition

Abstract The sex ratio at birth (SRB) may be patterned by maternal condition and/or environmental stressors. However, despite decades of research, empirical results from across the social and biological sciences are equivocal on this topic. Using longitudinal individual-level data from a US populati...

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Autores principales:	Ryan Schacht, Douglas Tharp, Ken R. Smith
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2019
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/0a0e9ff2ef8944dd922b6849507cec7f
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spelling	oai:doaj.org-article:0a0e9ff2ef8944dd922b6849507cec7f2021-12-02T15:09:24ZSex ratios at birth vary with environmental harshness but not maternal condition10.1038/s41598-019-45316-72045-2322https://doaj.org/article/0a0e9ff2ef8944dd922b6849507cec7f2019-06-01T00:00:00Zhttps://doi.org/10.1038/s41598-019-45316-7https://doaj.org/toc/2045-2322Abstract The sex ratio at birth (SRB) may be patterned by maternal condition and/or environmental stressors. However, despite decades of research, empirical results from across the social and biological sciences are equivocal on this topic. Using longitudinal individual-level data from a US population during the interwar period (1918–1939), inclusive of three distinct eras (Spanish Flu, Roaring ‘20 s, and the Great Depression), we evaluate predictions from two theoretical frameworks used to study patterning in SRB – (1) ‘frail males’ and (2) adaptive sex-biased investment theory (Trivers-Willard). The first approach centers on greater male susceptibility to exogenous stressors and argues that offspring survival should be expected to differ between ‘good’ and ‘bad’ times. The second approach contends that mothers themselves play a direct role in manipulating offspring SRB, and that those in better condition should invest more in sons. In-line with ‘frail male’ predictions, we find that boys are less likely to be born during the environmentally challenging times of the Spanish Flu and Great Depression. However, we find no evidence that maternal condition is associated with sex ratios at birth, a result inconsistent with the Trivers-Willard hypothesis.Ryan SchachtDouglas TharpKen R. SmithNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 9, Iss 1, Pp 1-7 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Ryan Schacht Douglas Tharp Ken R. Smith Sex ratios at birth vary with environmental harshness but not maternal condition
description	Abstract The sex ratio at birth (SRB) may be patterned by maternal condition and/or environmental stressors. However, despite decades of research, empirical results from across the social and biological sciences are equivocal on this topic. Using longitudinal individual-level data from a US population during the interwar period (1918–1939), inclusive of three distinct eras (Spanish Flu, Roaring ‘20 s, and the Great Depression), we evaluate predictions from two theoretical frameworks used to study patterning in SRB – (1) ‘frail males’ and (2) adaptive sex-biased investment theory (Trivers-Willard). The first approach centers on greater male susceptibility to exogenous stressors and argues that offspring survival should be expected to differ between ‘good’ and ‘bad’ times. The second approach contends that mothers themselves play a direct role in manipulating offspring SRB, and that those in better condition should invest more in sons. In-line with ‘frail male’ predictions, we find that boys are less likely to be born during the environmentally challenging times of the Spanish Flu and Great Depression. However, we find no evidence that maternal condition is associated with sex ratios at birth, a result inconsistent with the Trivers-Willard hypothesis.
format	article
author	Ryan Schacht Douglas Tharp Ken R. Smith
author_facet	Ryan Schacht Douglas Tharp Ken R. Smith
author_sort	Ryan Schacht
title	Sex ratios at birth vary with environmental harshness but not maternal condition
title_short	Sex ratios at birth vary with environmental harshness but not maternal condition
title_full	Sex ratios at birth vary with environmental harshness but not maternal condition
title_fullStr	Sex ratios at birth vary with environmental harshness but not maternal condition
title_full_unstemmed	Sex ratios at birth vary with environmental harshness but not maternal condition
title_sort	sex ratios at birth vary with environmental harshness but not maternal condition
publisher	Nature Portfolio
publishDate	2019
url	https://doaj.org/article/0a0e9ff2ef8944dd922b6849507cec7f
work_keys_str_mv	AT ryanschacht sexratiosatbirthvarywithenvironmentalharshnessbutnotmaternalcondition AT douglastharp sexratiosatbirthvarywithenvironmentalharshnessbutnotmaternalcondition AT kenrsmith sexratiosatbirthvarywithenvironmentalharshnessbutnotmaternalcondition
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Sex ratios at birth vary with environmental harshness but not maternal condition

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