In recent years, two new genetic technologies have started a scientific and medical revolution. One, relatively well known, is the ability to easily decode the information in our genes. The other, which is only dimly understood by the general public, is our newfound capacity to modify genes at will. These innovations give us the power to predict certain risks to our health, eliminate deadly diseases, and ultimately transform ourselves and the whole of nature. This development raises complex and urgent questions about the kind of society we want and who we really are. A brave new world is just around the corner, and we had better be ready for it or things could go horribly wrong.

The revolution began in benign but spectacular fashion. In June 2000, President Bill Clinton and Prime Minister Tony Blair announced the completion of the first draft of the human genome. According to a White House press statement, this achievement would “lead to new ways to prevent, diagnose, treat, and cure disease.” Many scientists were skeptical, but the public (who footed much of the $3 billion bill) probably found this highly practical justification more acceptable than the mere desire to know, which was in fact a large part of the motivation of many of the scientists involved.

During the 2000s, Clinton’s vision was slowly put into practice, beginning with the development of tests for genetic diseases. As these tests have become widespread, ethical concerns have begun to surface. Bonnie Rochman’s The Gene Machine shows how genetic testing is changing the lives of prospective parents and explores the dilemmas many people now face when deciding whether to have a child who might have a particular disease. Some of these technologies are relatively straightforward, such as the new blood test for Down syndrome or the Dor Yeshorim genetic database for Jews, which enables people to avoid partners with whom they might have a child affected by the lethal Tay-Sachs disease (particularly prevalent in Ashkenazis). But both of these apparently anodyne processes turn out to raise important ethical issues.

Whether we like it or not, the Dor Yeshorim database and other similar initiatives, such as genetic tests for sickle-cell anemia, which largely affects African-Americans, are enabling us to deliberately change the frequency of certain human genes in the population. This is the technical definition of eugenics and might seem shocking, since eugenics is forever associated with the forced sterilization of the mentally ill and Native Americans in the US or the murder of those deemed genetically defective by the Nazis. But the ability to use genetic testing when deciding whether or not to have children is clearly a form of soft eugenics, albeit one carried out voluntarily by…