When most people think of torturers, stalkers, robbers, rapists, and murderers, they imagine crazed drooling monsters with maniacal Charles Manson-like eyes. The calm normal-looking image starring back at you from the bathroom mirror reflects a truer representation. The dangerous idea is that all of us contain within our large brains adaptations whose functions are to commit despicable atrocities against our fellow humans — atrocities most would label evil.
The unfortunate fact is that killing has proved to be an effective solution to an array of adaptive problems in the ruthless evolutionary games of survival and reproductive competition: Preventing injury, rape, or death; protecting one's children; eliminating a crucial antagonist; acquiring a rival's resources; securing sexual access to a competitor's mate; preventing an interloper from appropriating one's own mate; and protecting vital resources needed for reproduction.
The idea that evil has evolved is dangerous on several counts. If our brains contain psychological circuits that can trigger murder, genocide, and other forms of malevolence, then perhaps we can't hold those who commit carnage responsible: "It's not my client's fault, your honor, his evolved homicide adaptations made him do it." Understanding causality, however, does not exonerate murderers, whether the tributaries trace back to human evolution history or to modern exposure to alcoholic mothers, violent fathers, or the ills of bullying, poverty, drugs, or computer games. It would be dangerous if the theory of the evolved murderous mind were misused to let killers free.
The evolution of evil is dangerous for a more disconcerting reason. We like to believe that evil can be objectively located in a particular set of evil deeds, or within the subset people who perpetrate horrors on others, regardless of the perspective of the perpetrator or victim. That is not the case. The perspective of the perpetrator and victim differ profoundly. Many view killing a member of one's in-group, for example, to be evil, but take a different view of killing those in the out-group. Some people point to the biblical commandment "thou shalt not kill" as an absolute. Closer biblical inspection reveals that this injunction applied only to murder within one's group.
Conflict with terrorists provides a modern example. Osama bin Laden declared: "The ruling to kill the Americans and their allies — civilians and military — is an individual duty for every Muslim who can do it in any country in which it is possible to do it." What is evil from the perspective of an American who is a potential victim is an act of responsibility and higher moral good from the terrorist's perspective. Similarly, when President Bush identified an "axis of evil," he rendered it moral for Americans to kill those falling under that axis — a judgment undoubtedly considered evil by those whose lives have become imperiled.
At a rough approximation, we view as evil people who inflict massive evolutionary fitness costs on us, our families, or our allies. No one summarized these fitness costs better than the feared conqueror Genghis Khan (1167-1227): "The greatest pleasure is to vanquish your enemies, to chase them before you, to rob them of their wealth, to see their near and dear bathed in tears, to ride their horses and sleep on the bellies of their wives and daughters."
We can be sure that the families of the victims of Genghis Khan saw him as evil. We can be just as sure that his many sons, whose harems he filled with women of the conquered groups, saw him as a venerated benefactor. In modern times, we react with horror at Mr. Khan describing the deep psychological satisfaction he gained from inflicting fitness costs on victims while purloining fitness fruits for himself. But it is sobering to realize that perhaps half a percent of the world's population today are descendants of Genghis Khan.
On reflection, the dangerous idea may not be that murder historically has been advantageous to the reproductive success of killers; nor that we all house homicidal circuits within our brains; nor even that all of us are lineal descendants of ancestors who murdered. The danger comes from people who refuse to recognize that there are dark sides of human nature that cannot be wished away by attributing them to the modern ills of culture, poverty, pathology, or exposure to media violence. The danger comes from failing to gaze into the mirror and come to grips the capacity for evil in all of us.