Adventures in Physiology: Poor Women Make Richer Breastmilk for DaughtersCarolyn Castiglia
A study released this week in the American Journal of Physical Anthropology shows that “poor mothers will invest more resources in daughters, who stand a greater chance of increasing their status through marriage than do sons.” The study focused on mothers in Kenya, so it’s unclear if the same results would be shown in the US, but the most fascinating part about the study is not just that these poor Kenyan women consciously treat their daughters better, their bodies actually produce richer breastmilk for their daughters as opposed to sons.
The study was helmed by Masako Fujita, a Michigan State University anthropologist. She and her team also discovered that “mothers who were better off financially favored sons over daughters.” They say the results of this study “support a 1973 hypothesis that predicts poor mothers will favor their daughters.” It appears one of the reasons the Kenyan mothers studied favor daughters is because in the villages where they live, men can have multiple wives. So it makes sense that raising a healthy girl who can be married off would potentially increase the family’s wealth and therefore health and well-being. An abstract of the complete study goes on to say, “Economically sufficient mothers will breastfeed sons more frequently than daughters, whereas poor mothers will breastfeed daughters more frequently than sons, and economically sufficient mothers will produce breast milk with higher fat concentration for sons than daughters, whereas poor mothers will produce breast milk with higher fat concentration for daughters than sons.”
According to the University of Michigan, this study “is one of the first to explore parents’ unequal biological investment in their children, such as the nutritional content of breast milk.”