In the late 1950s and early 1960s, Mao Zedong of China proposed the "Great Leap Forward" campaign which was supposed to increase the production of steel and propel his country in the higher ranks of industrialized nations. But the leaders were scrambling to find ways to make more steel, grain production has fallen. Tens of millions of Chinese died. A new study finds that the famine also had demographic consequences: A significantly higher proportion of girls born after the famine in the years leading up to it.
Evolutionary biology predicts that when times are tough, it is advantageous to give birth to girls. The reason may be that inferior men are not more likely to get opportunities to mate the males stronger. Shige Song, a social demographer at Queens College of the City University of New York, wanted to see if this effect occurred in people suffering from famine. Other researchers have sought a ratio sex change after two other famines, the Dutch Hunger Winter 1944-1945 and famine in 1942 associated with the siege of Leningrad in the former Soviet Union, but they have found results contradictory.
Song went after more famine: the Great Leap Forward. More than 30 million people died during this event. This is several times the number who died in the two smaller European famines. Chinese famine had many causes. Among them was the emphasis on making more steel took the job away from agricultural work, such as harvesting grain. The disaster began in the fall of 1958 in some areas and was widespread in China by January 1959.It lasted 3 years, until the end of 1961.
song used in a data survey of 310.101 elderly Chinese women aged 15 years 1982-67, which collected information on all of their children. He found that, before the famine, the proportion of male births has increased slowly. (We do not know why this is happening, but the song has used the trend as a baseline to examine changes in the sex ratio associated with starvation.) The sex ratio reached a peak of "masculinity" around 1958, then began to change, falling from 521 men per thousand births in April 1960 to 510 males per thousand births in October 1963. the sex ratio has not begun to swing back toward a higher proportion of men until nearly 2 years after the famine ended, reported online today in the song Proceedings of the Royal Society B.
song think the long duration of the famine may explain why other studies have failed to show similar results. The Dutch famine and Leningrad may have been too short, 7 months and 6 months respectively, to affect the number of baby girls born. "It's not like you skip breakfast for 1 or 2 days, then you influence the sex ratio," he said. "It is a cumulative process. The body has to learn that it is real. "
Tessa Roseboom, a biologist at Academic Medical Center in Amsterdam who studies the Dutch famine, recognizes seven months of famine may simply not long enough to cause change in sex ratio. It also emphasizes that it has birth records for only 2500 babies while studying the song covers more than 830,000. It is not surprising that other researchers have managed to find a consistent effect of sex ratio with the Dutch data, she said, "just because the effect, if there is not very big."
But other research has found that even the short-term fasting can influence the sex, says Douglas Almond, an economist at Columbia University who also studied the famine of the Great Leap forward. He analyzed the women who fast during Ramadan and found that babies which have been designed near the time of fasting are relevant and most skewed female sex change in the ratio is greater than the song found. "I think there is an immediate effect," said Almond. He agrees with the song on the base point, though. "Sex respond to maternal condition and nutrition is a major factor . "
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