Correction: Earlier verions of this book review incorrectly said that the United States has the highest homicide rate in the world. In her book, Mara Hvistendahl describes the United States as the most violent industrialized nation in the world. This version has been corrected.

Any readers out there with anxiety deficit disorder? Is there someone still sleeping peacefully despite the economy, wars, climate change, natural disasters, honeybee disappearance and other frightening scourges you are powerless to change? Have I got a book for you!

In “Unnatural Selection,” Mara Hvistendahl, a Beijing-based journalist specializing in science, warns of an impending hormonal tsunami of surplus Asian men, deprived of their demographic mates by sex-selective abortions and creating a world of male violence and sexual predation. In this world, “roid rage” from extra testosterone and the decline in the calming power of marriage could lead to an epidemic of young men driven to delinquency, crime and murder — and that’s just the beginning.

As Hvistendahl reports in her massively well-documented book, male births are far outnumbering female births in East Asia, South Asia and West Asia, all the way to Albania. While the normal sex ratio at birth is about 105 males to 100 females, in the county of Suining, China, for example, 152 boys are born for every 100 girls. These surplus boys may feel happy when they are small, but they will grow up condemned to singlehood. According to the French demographer Christophe Guilmoto, we are facing an epidemic of “rampant demographic masculinization” that will have “grave effects for future generations.”

In the first two-thirds of her book, Hvistendahl explores the reasons for such a cataclysmic population shift. When scientists and sociologists first began to draw attention to this imbalance in the 1990s, they thought that large-scale female infanticide had reemerged and that infant girls were being killed. But slowly they realized that female offspring were being identified in the fetal state by amniocentesis and ultrasound, and aborted by parental wish.

Feminists blame the gender imbalance on patriarchal cultural prejudice against girls and daughters. But Hvistendahl, who has not only done her research but has also carried out extensive investigative journalism in several countries, blames much more complex geopolitical and economic forces, including imperialist political decisions, American medical technology and the drive for population control.

‘Unnatural Selection: Choosing Boys Over Girls, and the Consequences of a World Full of Men by Mara Hvistendahl. PublicAffairs. 314 pp. $26.99. (PublicAffairs)

She traces the development and marketing of amniocentesis and American ultrasound machinery, the rise of genetic counseling, and drastic government policies to curb population, such as China’s one-baby policy, instituted in 1980. The international availability of prenatal screening in the 1980s and government tolerance or support of abortion as a means of birth control made it possible for parents to choose the sex of their children. Hvistendahl identifies the common elements from country to country: First, rapid development allows prenatal screening; second, abortion is easily available; third, the practice starts with elite groups and trickles down to the general population.

Despite these factors, the most significant cause of the imbalance is still the widespread desire for male children, especially among elite groups with access to advanced medical technology. Population-control experts realized that in many countries, people kept on having children until they had a son; Guilmoto notes that “there is a general trend of son preference” in much of the world. Demographers and Asian policymakers realized that if couples could have a male child early, they would stop having multiple children. In the words of New York Times journalist Elisabeth Bumiller, sex selection is “a powerful example of what can happen when modern technology collides with the forces of a traditional society.”

In the last section of her book, “The Womanless World,” Hvistendahl examines the dire costs of such a gender imbalance: the traffic in foreign brides and rises in polyandry, child marriage, prostitution, sex tourism, sexually transmitted disease and social violence. Of course, the United States is the most violent industrialized nation in the world, and some historians believe that the male-dominated frontier, especially the Wild West, planted “the seeds of a nation’s violence” and its macho values.

Tracing American violence to the frontier seems simplistic to me, but overall Hvistendahl is convincing, backing up her details with in-depth interviews with scientists from China to California. But is her book alarming or alarmist? After all, scientific change has unintended consequences, both positive and negative. Scarcity and the law of supply and demand may give women more bargaining power in marital choice. In India, “interregional marriage is breaking down the caste hierarchy.” In Vietnam, bought brides are valuable because they can get money to return to their families, and in China, families now prefer daughters who can marry abroad and send money home. The government policies that encouraged the imbalance may be changed to reverse it. South Korea achieved a normal birth rate in 2007 as a result of “gender-sensitive policies.”

Hvistendahl argues that we need a regulatory agency to monitor U.S. fertility clinics and new medical technologies in that field. Some scholars, however, do not think gender imbalance and sex determination have such high-risk consequences that we ought to halt prenatal screenings and other new and important technologies. Arno G. Motulsky, a geneticist at the University of Washington, noted that although Alaska, for example, has more males than females, it “has not encountered serious societal dislocations.” (Late-night comedians might disagree.) Amitai Etzioni, who worried about gender imbalance in an article for Science in 1968, has now changed his mind and has not found “enough compelling damage that would lead us to stop science.” And Hvistendahl herself acknowledges that anti-abortion groups could use the data to block abortions for American women, and she feels uneasy about “treading onto unexpected political ground.”

Is Hvsitendahl a whistleblower, warning us of a terrible disaster we must take action to avert — and if so, what kind of action would that be? Or is she a Cassandra, describing an unavoidable destiny for humankind that we cannot prevent? In either case, she has written a disturbing, engrossing book that we can add to the tottering shelf of problems that keep us up at night.

Elaine Showalter , a professor emeritus at Princeton University, has written extensively about gender and science.

Demographics review by Elaine Showalter