Unnatural Selection by Mara Hvistendahl charts how the trend towards choosing boys over girls, largely through sex-selective abortions, is rapidly spreading across the developing world.
While the natural sex ratio at birth is 105 boys born for every 100 girls, in India the figure has risen to 112 boys and in China 121. The Chinese city of Lianyungang recorded an astonishing 163 boys per 100 girls in 2007.
The bias towards boys has been estimated to have caused the "disappearance" of 160 million women and girls in Asia alone over the past few decades. The pattern has now spilled over to Azerbaijan, Georgia and Armenia, the Balkans and Albania, where the sex ratio is 115/100.
The unnatural skewing towards male populations has become so pronounced in recent decades that Hvistendahl, a writer for Science magazine, says it has given rise to a new "Generation XY". She raises the possibility that with so many surplus men – up to a fifth of men will be single in northwestern India by 2020 – large parts of the world could become like America's wild west, with excess testosterone leading to raised levels of crime and violence.
"Historically, societies in which men substantially outnumber women are not nice places to live," Hvistendahl writes.
While parents in some countries seem to prefer boys to girls, it is men who commit most crimes, particularly violent crimes. Men are 4X more likely than women to commit a violent crime here in the US. History suggests that these numbers worsen as the percentage of men rises. This doesn't bode well for the the safety of China's streets or even the world, as China becomes an even stronger military power.