Summary

At work one day, Hayward comments on how the author does not look good, but the author says he has not been sleeping well. Conversation about whether the author knew a border guard from his old station who had shot and killed a migrant leads to Hayward confessing that when he was a young cop, he killed someone, “an old and quiet pain spreading across his face” (146). The author comments that he hopes he never has to carry that kind of pain.

The author summarizes the science and the process that led to the discovery of the so-called “warrior gene,” an enzyme deficiency specifically in men that can indicate a predisposition to violence. The author also suggests that there is research showing that the gene, and the predisposition, are both activated by a childhood history of violence and trauma. He adds that...