Famine Mothers Are More Likely to Give Birth to a Female Child
According to a study, during the famine of the 60s in China, the male to female birth ratio fell drastically. In this study it was concluded that when the food supplies are short, the chances of a woman giving birth to a female child is more.
The study was originally carried out by Shige Song, a demographer and sociologist from City University of New York. He analyzed the data from over 300,000 Chinese women that gave birth from September 1929 to July 1982. However, in this data was even included the period when Great Leap Forward Famine took place that caused millions of death.
While analyzing the data, Song found that just one year after the famine the percentage of male birth had fallen drastically-from 109 boys to 100 girls in April 1960 to 104 boys to 100 girls by October 1963. After further examining the data, he found that it was until July 1965 that it took the ratio to return to its normal pre-famine levels.
His analysis was published in Proceedings of the Royal Society * which backs the sex-ratio adjustment hypothesis. According to this hypothesis, the species under harsh environmental conditions alter the gender of their offspring. Besides, malnourished and unhealthy men have lesser children than equally undernourished women. Thus, the hypothesis states that in order to sustain the population and keep it growing, females must bear fewer boys.
Though, studies on animals like the red deer solidify the stance of this hypothesis, still there aren’t enough evidence in case of humans that can make this hypothesis more solid. In fact, earlier studies on data collected from Dutch Hunger Winter (1944-45) and Siege of Leningrad in Soviet Union (1942), have failed to give any results.
However, Song believes that since he was able to clearly observe the effects of Chinese Famine on human birth rate, which was quite severe, took place for a longer duration and affected more individuals, he had a well documented data and population statistics to work with. Besides, he further added that it also gave him the idea regarding how much time it takes to trigger the effect, which was about minimum of one year in China’s case.
The data which Song studied was originally collected in the year 1982 by China State Family Planning Commission while doing a population fertility survey. In this survey they asked the females about their whole childbearing history. Song further adds that he fully believes in the authenticity of this data as there’s no reason for the women toile about the gender of their child. Besides, the One-child policy of China was introduced much later in the year 1978 that can no way affect the data collected because most of the families prefer a male child over female. The policy was actually in its initial phase while the data was being collected and at that time the ultrasound technology wasn’t commonly available.
Cheng Huang, a population economist & demographer at Emory University in Atlanta, Georgia said “I am convinced that the change of sex ratio shown in the study is causally related to famine exposure.” Lambert Lumey, an epidemiologist at Columbia University in New York said- “At this point we don’t know the reason for the dip.” He further suggested that Shige Song might have made his case stronger if he had also examined the male to female birth ratios at certain Chinese regions which faced famine at different times.
* Shige Song, “Does famine influence sex ratio at birth? Evidence from the 1959-1961 Great Leap Forward Famine in China”, Proceedings of The Royal Society (2012)