Women are tougher than men, and men are more at risk of dying younger, so those in poorer communities are more likely to give birth to daughters to ensure survival, suggests new research, reports the Telegraph.
A database of more than 95,000 Rwandan mums was analysed, and researchers found that lower-ranking wives in polygynous marriages – who get a smaller share of their husband’s resources – had more baby girls that higher-ranking wives and women in monogamous marriages.
“Mothers in poor condition, here lower-ranking wives in a polygynous marriage, may overproduce daughters because these give them greater fitness returns than sons,” said one of the researchers, social psychologist Dr Thomas Pollet from the Netherlands’ Groningen University.
Married, better-educated and younger mums are more likely to give birth to baby boys, previous researcher has also shown.
The idea that poorer mums have more girls seems to occur in a range of species, including insects, birds, pigs, sheep, dogs, mink and deer.