In 2007, the booming port city of Lianyungang achieved the dubious distinction of having the most extreme gender ratio for children under five in China: 163 boys for every 100 girls. The numbers may not matter much to the preschool set. But in twenty years the skewed sex ratio will pose a colossal challenge. When Lianyungang’s children reach adulthood, their generation will have twenty-four million more men than women. 

The prognosis for China’s neighbors is no less bleak: rampant sex selective abortion has left over 160 million females “missing” from Asia’s population. And gender imbalance reaches far beyond South and East Asia, affecting the Caucasus countries, Eastern Europe, and even some groups in the United States — a rate of diffusion so rapid that the leading expert on the topic compares it to an epidemic. As economic development spurs parents in developing countries to have fewer children and brings them access to sex determination technology, couples are making sure at least one of their children is a son. So many parents now select for boys that they have skewed the sex ratio at birth of the entire world. 

Sex selection did not arise on its own. Largely unknown until now is that the sex ratio imbalance is partly the work of a group of 1960s American activists and scientists who zealously backed the use of prenatal technologies in their haste to solve an earlier global problem. 

What does this mean for our future? The sex ratio imbalance has already led to a spike in sex trafficking and bride buying across Asia, and it may be linked to a recent rise in crime there as well. More far-reaching problems could be on the horizon: From ancient Rome to the American Wild West, historical excesses of men have yielded periods of violence and instability. Traveling to nine countries, Mara Hvistendahl has produced a stunning, impeccably researched book that examines not only the consequences of the misbegotten policies underlying sex selection but also the West’s role in creating them.