Author:
Ian J. RickardDepartment of Animal and Plant Sciences, University of Sheffield, Sheffield, UK

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Abstract

The ‘generalized Trivers-Willard hypothesis’ (gTWH) proposes that heritable traits associated with reproductive success of one sex will be positively associated with a genetic tendency to produce offspring of that sex. However, unlike the original Trivers-Willard hypothesis, the predictions of gTWH are proposed to be borne out regardless of environmental conditions. This is a problem because it ignores the influence of the hypothetical genetic variance in offspring sex-ratio on population operational sex-ratio and thus offspring's likely success in finding a mate. Accordingly, there is a notable lack of evidence to support the existence of such heritable variation in offspring sex-ratio in humans or other mammals. The genetic tendency for all individuals within populations of birds and mammals to produce a male offspring with the same probability as one another is well-established. In fact it is a cornerstone of population sex-ratio theory, upon which is built hypotheses of facultative (environmental) sex-ratio adjustment, including the original Trivers-Willard hypothesis. I therefore suggest that any phenotypic correlations between offspring sex-ratio and traits that may be associated with the reproductive success of offspring of one sex are most likely to be environmental in origin.

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Journal of Evolutionary Psychology 
Language English
Size  
Year of
Foundation
2007 (2003)
Publication
Programme
changed title
Volumes
per Year
 
Issues
per Year
 
Founder Akadémiai Kiadó
Founder's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Publisher's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Responsible
Publisher
Chief Executive Officer, Akadémiai Kiadó
ISSN 1789-2082 (Print)
ISSN 2060-5587 (Online)

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