A sociological study of the famine that happened during China’s Great Leap Forward suggests that, like many other species, humans modify their birth rates to reflect times of feast or famine. Specifically, more girls are born in starving communities than boys.
This and other types of environmentally based birth modifications have been observed elsewhere in the animal kingdom. Alligator offspring’s sex are determined by the temperature of the environment just prior to birth. Studies also show that “handedness” – whether you predominantly use your left or right hand – can be affected by stress on the mother prior to birth. But this is the first indication that such modifications happen on a large-scale based on poverty of resources. That a community-wide change can be observed in time of poverty has huge implications for social science.
The report does not have a definite conclusion as to why the disparity in gender production. But one possibility suggested is that, since malnourished males produce less offspring than comparably malnourished females, this may be nature’s way of maintaining the continuation of the species.