Sex-ratio biasing towards daughters among lower-ranking co-wives in Rwanda.
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.
Pollet
Thomas V
TV
Department of Social Psychology, University of Groningen, Grote Kruisstraat II, 1, 9712TS Groningen, The Netherlands. T.V.Pollet@rug.nl
Fawcett
Tim W
TW
Buunk
Abraham P
AP
Nettle
Daniel
D
D005260:Female; D006608:Hierarchy, Social; D006801:Humans; D008297:Male; D008393:Marriage; D012432:Rwanda; D012744:Sex Ratio