Are some people just natural-born killers? Modern research raises some disturbing questions

Genetic counseling was not commonplace in 1978, but the Dutch woman who came to University Hospital in Nijmegen, the Netherlands, hoped geneticists could help her learn what was wrong with so many of the men in her family, including her own son. They had mild developmental disabilities and, more disturbingly, they were repeatedly violent — responsible for acts of arson, assault, attempted rape and attempted murder. It was such an obvious problem that 16 years earlier, an uncle had drawn up a family tree of male brutality that went back to the 1870s.

That family’s case launched studies that didn’t bear fruit until the early 1990s, when researchers found a specific gene mutation on all of the X chromosomes of all the violent men. Some women in the family had the mutation, too, but since women have two X chromosomes, it appeared that the other one functioned normally and made up for the defect. In other words, the men appeared to be genetically predisposed to violence. ...


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