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UNC research ties aggressive tendencies in boys to 3 genes

Maybe some boys really were born to be wild.

Researchers at UNC Chapel Hill announced this week they found three genes that appear to affect the probability of a life of crime.

The study looked at roughly 1,100 boys in middle school and high school, ages 12-18.

In 1996 and again in 2002, the participants were asked to take a 12-question survey to gauge their delinquent tendencies. The participants' delinquency scores were matched against their genetics to look for a correlation.

The results clearly showed a genetic basis for aggressive behavior.

The idea that personality and behavior can be predicted by genetics has a dark past. “Bad genes” were the basis for Henry Goddard's theory of eugenics in the early 19th century, and was used to justify racial supremacy.

In the current research, scientists emphasized that having the gene doesn't necessarily mean a child is destined to become a hardened criminal.

“Its not like with some genetic diseases like cystic fibrosis or Huntington's, where when you have the genes the likelihood increases by 5,000-fold,” said Guang Guo, a professor of sociology at UNC and the study's lead author. “If you have the genotype you're not necessarily going to be a delinquent.”

Parenting and other social factors can completely override the influence of the genes, he said.

This is old news for Rain Fawcett, mother of three boys ages 17, 20 and 22. She said it was obvious her boys all came with their own personalities from a young age, with different levels of aggression.

“My oldest boy had a lot of anger,” she said. “He seemed to have come wired that way.”

Rain said she believes natural wiring can be overcome by smart parenting.

“In our family the rule was you don't hurt your brothers, and you don't say hurtful things,” she said. “I taught my boys to find a way to deal with their anger and aggression in a way that didn't hurt others.”

From an evolutionary perspective, aggressive behavior might be beneficial. According to the UNC team's research, which will be published in the August edition of American Sociological Review, boys who tend to be more aggressive could have advantages when it comes to getting a mate, protecting their families and getting enough food.

Studies of violent behavior among wild chimpanzees suggested to the study's authors that “human violence is rooted in pre-human history.” In other words, we could be hard-wired for delinquency based on the social skills we needed to survive before we even evolved into homo sapiens.

Guo was careful not to overstate the potential for applying this knowledge, particularly because the ethical and legal implications could be significant and complex. As an example, Guo suggested the hypothetical of a juvenile delinquent who has had genetic testing and is known to have a high genetic predisposition for aggression.

“Some people might say in court that they're not responsible because they're driven by genes and it could reduce their sentence,” said Guo. “But on the other hand, the gene may indicate that they are more likely to repeat their offense, so that the court would be very reluctant to release them, and that might actually increase the penalty.”

As of right now, there isn't enough research to assess delinquents for genetic traits, said Virginia Pirrelo, Clinical Services administrator for the N.C. Department of Juvenile Justice and Prevention.

She said she was not surprised to hear that genetics may put some boys at higher risk for anti-social behavior, but said other factors could be equally or more influential.

“Environment definitely plays a part,” she said. “But I think a lot of research suggests an interaction between variables, which makes sense.”

The idea of “bad genes” has been around for centuries and is associated with a number of dark periods in U.S. history. In 1927, based on the now-discredited theory of selective human breeding, the U.S. Supreme Court ruled in favor of forced sterilization of the mentally ill and dangerous criminals.

In defense of the decision, Justice Oliver Wendell Holmes wrote: “It is better for all the world if instead of waiting to execute degenerate offspring for their crime…society can prevent those persons who are manifestly unfit from continuing their kind.”

The practice continued until 1942 when the court ruled it unconstitutional.

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