TY - JOUR
T1 - No genetic contribution to variation in human offspring sex ratio: a total population study of 4.7 million births
AU - Zietsch, Brendan P.
AU - Walum, Hasse
AU - Lichtenstein, Paul
AU - Verweij, Karin J. H.
AU - Kuja-Halkola, Ralf
N1 - Funding Information: Acknowledgements. B.P.Z. received funding from The Australian Research Council (grant no. FT160100298). K.J.H.V. is supported by the Foundation Volksbond Rotterdam. Publisher Copyright: © 2020 The Author(s) Published by the Royal Society. All rights reserved. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/2/26
Y1 - 2020/2/26
N2 - The ratio of males to females among an individual's offspring at birth (offspring sex ratio) has long been of great interest to evolutionary biologists. The human offspring sex ratio is around 1 : 1 and is understood primarily in terms of Fisher's principle (R. A. Fisher, The genetical theory of natural selection, 1930), which is based on the insight that in a population with an unequal sex ratio, each individual of the rarer sex will on average have greater reproductive value than each individual of the more common sex. Accordingly, individuals genetically predisposed to produce the rarer sex will tend to have greater fitness and thus genes predisposing to bearing that sex will increase in frequency until the population sex ratio approaches 1 : 1. An assumption of this perspective is that individuals' offspring sex ratio is heritable. However, the heritability in humans remains remarkably uncertain, with inconsistent findings and important power limitations of existing studies. To address this persistent uncertainty, we used data from the entire Swedish-born population born 1932 or later, including 3 543 243 individuals and their 4 753 269 children. To investigate whether offspring sex ratio is influenced by genetic variation, we tested the association between individuals' offspring's sex and their siblings' offspring's sex (n pairs = 14 015 421). We estimated that the heritability for offspring sex ratio was zero, with an upper 95% confidence interval of 0.002, rendering Fisher's principle and several other existing hypotheses untenable as frameworks for understanding human offspring sex ratio.
AB - The ratio of males to females among an individual's offspring at birth (offspring sex ratio) has long been of great interest to evolutionary biologists. The human offspring sex ratio is around 1 : 1 and is understood primarily in terms of Fisher's principle (R. A. Fisher, The genetical theory of natural selection, 1930), which is based on the insight that in a population with an unequal sex ratio, each individual of the rarer sex will on average have greater reproductive value than each individual of the more common sex. Accordingly, individuals genetically predisposed to produce the rarer sex will tend to have greater fitness and thus genes predisposing to bearing that sex will increase in frequency until the population sex ratio approaches 1 : 1. An assumption of this perspective is that individuals' offspring sex ratio is heritable. However, the heritability in humans remains remarkably uncertain, with inconsistent findings and important power limitations of existing studies. To address this persistent uncertainty, we used data from the entire Swedish-born population born 1932 or later, including 3 543 243 individuals and their 4 753 269 children. To investigate whether offspring sex ratio is influenced by genetic variation, we tested the association between individuals' offspring's sex and their siblings' offspring's sex (n pairs = 14 015 421). We estimated that the heritability for offspring sex ratio was zero, with an upper 95% confidence interval of 0.002, rendering Fisher's principle and several other existing hypotheses untenable as frameworks for understanding human offspring sex ratio.
KW - Familial aggregation
KW - Negative frequency-dependent selection
KW - Sex allocation
KW - Steroid hormones
KW - Trivers–Willard
UR - http://www.scopus.com/inward/record.url?scp=85079642093&partnerID=8YFLogxK
U2 - https://doi.org/10.1098/rspb.2019.2849
DO - https://doi.org/10.1098/rspb.2019.2849
M3 - Article
C2 - 32070249
SN - 0962-8452
VL - 287
SP - 20192849
JO - Proceedings. Biological sciences / The Royal Society
JF - Proceedings. Biological sciences / The Royal Society
IS - 1921
M1 - 20192849
ER -