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. 2009 Dec 23;5(6):765-8.
doi: 10.1098/rsbl.2009.0394. Epub 2009 Jul 8.

Sex-ratio biasing towards daughters among lower-ranking co-wives in Rwanda

Thomas V Pollet  1 , Tim W Fawcett, Abraham P Buunk, Daniel Nettle
Affiliations

Sex-ratio biasing towards daughters among lower-ranking co-wives in Rwanda

Thomas V Pollet et al. Biol Lett. .

Abstract

There is considerable debate as to whether human females bias the sex ratio of their offspring as a function of their own condition. We apply the Trivers-Willard prediction-that mothers in poor condition will overproduce daughters-to a novel measure of condition, namely wife rank within a polygynous marriage. Using a large-scale sample of over 95 000 Rwandan mothers, we show that lower-ranking polygynous wives do indeed have significantly more daughters than higher-ranking polygynous wives and monogamously married women. This effect remains when controlling for potential confounds such as maternal age. We discuss these results in reference to previous work on sex-ratio adjustment in humans.

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Figures

Figure 1.
Figure 1.
Mean son ratio (number of sons ever born/number of children ever born) by marriage type. Bars represent 95 per cent confidence intervals.
See this image and copyright information in PMC

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