Extramarital sex is the principal factor in high violent crime rates in the Americas (North, South, and Central). This surprising conclusion calls for some explanation. As promised, here it is.

The first point to make is that most violent crime involves young male perpetrators on male victims. The violence is thus between potential competitors over women (1). Such violence can prove deadly. In their study of homicides in Detroit, Canadian researchers found that the leading cause of homicides was seemingly unmotivated aggression that police classify as "trivial altercations." For instance, two men accidentally jostle each other in a bar, there is a scuffle, and someone gets fatally stabbed. Men who lose face in such encounters fall in the pecking order and become less desirable as dates. In trivial altercations, men are indirectly fighting over women.

In contrast, men who are married and out of the dating arena have remarkably low rates of violence. Divorce is of interest here because formerly-married men find themselves dating again. When that happens, their involvement in violent crime rises also. This is not too surprising because dating takes place in singles bars and night clubs where alcohol is consumed and inhibition is lowered. A substantial proportion of violent crime occurs close to such venues.

Researchers have also looked at the physiological implications of divorce. Divorced men have unusually high levels of the male hormone testosterone coursing through their veins. This is significant because the increased aggression of all male vertebrates during the mating season is due to a spurt in testosterone output. It is the reason that robins sing to warn off other males and fight to defend their territory.

Psychologists are fond of arguing that testosterone has less effect on human behavior than is true of other species but they may protest too much. Testosterone increases in men who find themselves dating again and it is actually increased by sexual intercourse. Mating increases testosterone and aggression for humans as for other species.

All of this goes some way towards explaining why countries that have a large population of dating men by reason of high non marriage, or single motherhood, would have high rates of violent crime, as is the case for the Americas.

The connection between dating and violent crime is also supported by age patterns. Young adulthood sees a peak in dating activity, in testosterone levels, and in violent crime. This does not, of course, mean that all young men go about clubbing each other, or their dates, like cartoon Neanderthals. Violent crimes are comparatively rare but testosterone "poisoning" nevertheless makes young men more reckless and crime-prone. Associating with reproductive competitors at night spots where sexually attractive women can be encountered likely increases testosterone production and with it the risk of reckless, or hotheaded, actions.

One can thus compile a long list of reasons that dating men are more likely to commit assaults, and even murders. The mere facts of staying out late at night, and consuming alcohol create huge increases in the probability of committing violent offences.

Women are also at greater risk of violence in sexually permissive societies because they meet strangers who are a potential threat to them. In more restrictive societies, young women are constantly chaperoned to protect them from all sexual opportunities, potentially abusive ones included. In the absence of dating, there can be no date rape.

Where women cohabit without formal marriage, they are also at greater risk of domestic violence than if they are married. A key reason is that common-law unions are much briefer than marriages and women are at greatly increased risk of violence around the time that the union is breaking up.

The connection between violent crime and dating might initially seem implausible but the more one thinks about it, the more compelling it becomes. Viewing crime from this perspective is illuminating in the sense that it helps explain why some countries are so much more violent than others. Yet, it is of limited practical usefulness. In a free society, we cannot legislate marriage, or ban extramarital sex, any more than we can legislate going to bed early, or abstaining from alcohol, laws that would, by themselves, take huge bites out of crime.

1. Barber, N. (2006). Why is violent crime so common in the Americas? Aggressive Behavior, 32, 442-450.

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