How this latest study of mice might translate into the human realm, no one yet knows. For now, though, the study suggests that what a prospective mother eats may affect whether one is more likely to have a girl or a boy. In a study by Elissa Cameron, a behavioral ecologist at the University of Pretoria in South Africa, the blood-glucose levels of female mice were manipulated to test what effect they would have on the sex ratios of the offspring. The results were dramatic: “The mice that received the steroid saw their glucose levels drop compared to untreated mice, and they gave birth to sons 42% of the time versus 54% of the time for sugar-rich mothers.”
The results seem to confirm earlier research that “has shown an association between more male offspring and a spike in blood sugar due to stress or food abundance.” And, it also seems to confirm a hypothesis proposed by biologists Robert Trivers and Dan Willard in the 1970s:
Pregnant animals invest more in offspring that will give them the largest number of grandchildren. For species in which males mate with more than one female, healthy mothers should have more boys, whereas less healthy mothers should have more girls.Although weak female offspring still find someone to mate with, weak males may never mate at all.
Thus, healthy female mice, those with high sugar levels, should be expected to give birth to more sons, and that is exactly what this latest study has found.
So, while there is no guarantee that the results would hold for humans, one can bet that in coming weeks there will be books and articles claiming that you can increase your odds of having a girl or boy with a steady diet of chocolates and sweets or abstinence from them. (Will there be a boom in candy sales in China?)