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

Thomas Pollet*, Tim Fawcett, Abraham Buunk, Daniel Nettle

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)765-768
JournalBiology Letters
Issue number6
Early online date8 Jul 2009
Publication statusPublished - 23 Dec 2009
Externally publishedYes


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