IN CHINA they are called “bare branches”: young men without wives or offspring, frustrated, rootless, drifting, disruptive. And there are a hell of a lot of them. Five years ago the Chinese Academy of Social Sciences in Beijing calculated that one Chinese man in six was unlikely to find a female partner. That’s about 111 million unattached males. In other words, there are twice as many bare branches in China as there are people in the whole of Britain.

The excess of young men over women in India is almost as vast. And in both countries the sex ratio seems to be getting more skewed by the year. In China now, 120 male babies are born for every 100 females. In some Indian villages the figure is nearer 150. The average figure around the globe is 105. In short, large areas of Asia seem to be going through a vast demographic shift that is unprecedented in history.

How has this bizarre imbalance come about? What are the social consequences, given that more than two billion people live in India and China? And what can be done about it? These are the questions asked (and answered, though not to everybody’s satisfaction) in a new book titled, appropriately enough, Bare Branches. But it is the book’s subtitle, “The Security Implications of Asia’s Surplus Male Population”, that has caused the real stir. For it hints ominously at the main thrust of the argument — that “the masculinisation of Asia’s sex ratios” is likely to lead to “inherently unstable” societies that are high in crime and violence and a potential threat to neighbouring countries as well.

The book’s assertions appear well-founded in recent Chinese experience. Back in 1997 the magazine Beijing Luntan was already noting that, given the increasing imbalance between males and females “forced marriages, girls stolen for wives, bigamy, prostitution and rape appear unavoidable.” Bride bartering or kidnapping is already commonplace in rural areas; prostitution is rife in the cities. China’s crime-rate has tripled in 20 years (an astonishing 923,000 serious crimes were reported in the first three months of this year), and it appears that the vast majority of offences are committed by rootless, disaffected young men.

Nevertheless, the book’s ticking time-bomb thesis has provoked scepticism, if not outright denunciation, in some academic and governmental circles. Official agencies in both China and the United States don’t dispute the figures, but say that the skewed sex ratio in many Asian countries (Taiwan, Bangladesh and Pakistan are in a similar position) can be controlled and, eventually, returned to normality. But the evidence amassed by the authors — two political scientists called Valerie Hudson and Andrea den Boer — seems to warrant serious debate.

They discuss first why Asian parents still exhibit a strong preference for boys over girls. The reasons vary from country to country. In India the dowry tradition, outlawed but still widespread, imposes a crippling financial penalty on poor families with daughters. That tradition doesn’t exist in China. There, the problem is much more about the absence of any pension system. That triggers chronic insecurity about old age, allied to a deep-rooted feeling that it is sons, not daughters, who support parents in their twilight years.

In recent years the Chinese Government has organised a huge advertising blitz to counter this. One commonly-seen poster shows a mother complaining about how she is neglected by her three sons, while another mother is given a helping hand by her assiduously caring daughter. But ancient prejudices die hard.

“In urban areas there is increasing recognition of a daughter’s value, because she can be educated and earn an income,” Andrea den Boer says. “But China is still overwhelmingly rural, and in rural areas there is no sense of a daughter contributing to the family’s economic wellbeing, since she will marry and move away.”

This bias towards sons has been present for centuries in India and China. But it was when comparatively cheap sex-prediction technology such as portable ultrasound machines became available in the late 1980s that birth sex ratio really started to go awry. Clearly, many pregnant women were choosing abortion when they learnt that the foetus was female.

“I don’t think the Chinese Government minded at first that the technology was used in this way, because the primary concern was to keep the birth rate down,” den Boer says. “But when skewed sex ratios became obvious in the 1990s, sex-prediction was made illegal.” The evidence from China and India, however, is that it still goes on, surreptitiously, on a massive scale.

This much of Bare Branches is largely uncontested, inside and outside the countries concerned. Indeed, the Chinese Government has recently restructured its population bureau to focus on what it sees as its two most urgent demographic problems: the increasingly grey population, who will have to be supported economically by fewer and fewer young people (an imbalance partly caused by the “one child” policy imposed since 1979); and the unbalanced sex ratio.

But it is when the authors discuss the “security implications” of having tens of millions of unattached young men drifting round Asia that their book becomes more contentious. The very phrase “surplus males”, for instance — with its “good for nothing” implication — has been stridently criticised by some academics.

“Yes, it has received a bad press in some quarters,” den Boer admits. “And I agree that it is, in many ways, an offensive term. We didn’t mean it to be, but it is difficult to come up with a corresponding male counterpart to the 100 million missing females — which is what we are really concerned about. In no way did we want to suggest that these are superfluous males.”