Thank heaven for little girls, for without them, little boys would turn to lives of crime.

In a recent review paper published in the Proceedings of the National Academy of Sciences, a team of British and Chinese researchers argue that sex selection in countries like China and India may have already set the stage for national crises by creating a surplus of men and a shortage of women.

Therese Hesketh, an author of the paper and researcher in child health at University College London, said the worst case scenario could be societal instability.

“Excess young men congregating together are known to be prone,” she said, “to violent crime, what we call ‘antisocial behavior.’ And prostitution rates will go up, trafficking rates will go up.”

In the new paper, Hesketh and co-author Zhu Wei Xing from the Zhejiang Normal University note that the human sex ratio at birth—the number of males born for every 100 females—typically runs between 105 and 107 across human populations. In countries such as China and India, where a strong preference for sons over daughters prevails, sex-selective abortion has caused a spike in the sex ratio.

The authors assert that over the next 20 years, in parts of China and India, there will be a 12 to 15 percent excess of young men—men who will have to remain single in societies that also place a high value on marriage. Because women will be able to select high status males to marry, the men who remain single are most likely to be members of the lower classes or those who are otherwise undesirable.

These unmarried, low-status males are the people most likely to be perpetrators of violent crime, the authors suggest. Previous research has shown a strong correlation between sex ratio and violence.

“Both sociological/criminological literature and historical literature demonstrate the link to increased vice, violence, crime, use of arms, riots, etc. in the presence of substantial numbers of mateless young adult men in society,” said an email from Valerie Hudson, a political scientist at Brigham Young University whose work on the effects of increased sex ratios was cited in the new study.

Hudson indicated that there were not only sociological but also biological underpinnings for the relationship between sex ratios and violence.

“Biologists have told us that circulating testosterone declines when a man makes a commitment to a woman, and further declines with the birth of his children to this woman,” she said.

The decline in testosterone helps to mitigate aggression in young men, Hudson said.

High sex ratios could increase the value of women, though it is unclear whether women themselves will benefit or if only the men who “win” them will be able to capitalize on the falling supply of women. In China and other countries without a dowry system, the women themselves will likely feel the increase in their value, said Hesketh.

But Hudson is skeptical.

“It is hard to see positive consequences for women, in contrast to what economists would have us believe about scarcity inevitably leading to a better situation for women,” she said. “That has never happened, ever.”

Hesketh said she expects the problem to be short-lived, resolving itself within two generations. Countries are working to lower their sex ratios by outlawing sex-selective abortion, improving the status of women, and ensuring that women can inherit property, she said.

Furthermore, marriage is so highly valued in China and India that Hesketh expects parents to realize that they may be better off having girls, who are likely to find husbands, than boys, who may not be able to find wives.

But for at least the next two decades or so, she said, there will be a surplus of young men in these countries.

“In the short term there are problems with these disenfranchised young men,” Hesketh said. “At the moment, we don’t really know to what extent that will be a problem.”

Originally published September 6, 2006


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