Counting up the numbers of boys and girls in a country has never been so troublesome. On Monday the medical journal the Lancet published a report estimating that prenatal selection and selective abortion in India was likely to be causing half a million girls to be culled every year. Within 24 hours, the Indian medical association weighed in to dispute the Lancet's figures as out-of-date and exaggerated. The Indian government has made no formal statement, but is said to be incandescent with rage.
There are good reasons for all this sensitivity. The abnormally unbalanced gender ratios of some Asian countries - either due to abortion, sex-selective technologies such as ultrasound or old-fashioned infanticide - have been the subject of academic controversy since the late 1980s. Just recently, however, they come to be cloaked in a more sinister hue. One of the latest growth areas in the academy is in "security demographics", where scholars are invited to predict the potentially dire implications of demographic change, and one of the most gloomy prognostications is rooted in what could happen when sex ratios spin out of kilter.
"Bare branches" is the Chinese term for the poor young men who are left with no prospect of finding a partner or starting a family. In their influential 2004 book of the same name, the American political scientists Valerie M Hudson and Andrea M den Boer argued that these men were an accident waiting to happen. The pair found evidence of a huge number of "missing females" in eight different Asian countries, but the vast majority were from India and China, where two-fifths of the world's population now live. In 1999, they noted, the Chinese academy of social sciences admitted that the birth-sex ratio in that country had reached 120 boys for every 100 girls, and that the number of surplus Chinese males was now 111 million.
These legions of surplus males, according to Hudson and Den Boer, are often poor or unemployed, and lack bargaining power in the market for marriage. The consequences of this vast demographic shift, according to the authors, could be dire. As economies turn bad, those surplus males are likely to generate crime and violence. The only way for countries to absorb the growing surfeit of young males, they argue, might be to amass huge armies and go to war to use up the excess men.
Hudson and Den Boer's thesis makes intriguing reading, but it is nothing more than an imaginative worst-case scenario. India has sought to stem the tide of sex selection by banning the use of technology to determine the sex of foetuses, but technology can usually outwit regulation. And although doctors in India must not tell the couples the sex of their foetus, many have developed coded signals for the job instead. The real reasons for the disparity lie in the hand-to-mouth agrarian culture of many parts of India, where men's physical labour counts for more than that of women and marriage dowries are excruciatingly expensive. The answer to bare branches lies not in bans, but in rapid development into the kind of world that has more time for the delicate charms of little girls.