"It is better to be hated for what you are then to be loved for what your not"
-Andre Gide

Adoption Studies

Another way that researchers have found proof of genetic influences on aggression is through adoption studies. By examining children of with aggressive biological parents who were adopted into either good or bad homes along with children of non-aggressive biological parents adopted into good or bad homes, we can make inferences about the influence of genetics versus the influence of the environment.

The results of many adoption studies show that for those children who have "good genes," that is, those who had non-aggressive biological parents, the home environment made little difference. Whether they were raised in high-class suburbs or crime-ridden ghettos, these children had few deviations for the normal rate of aggression. The same goes for those children born of aggressive parents, raised in good homes. They showed no extreme aggression. The problematic combination is that of children with aggressive biological parents and a poor adoptive environment. While these results are not set in stone, anti social and aggressive behavior rises dramatically in the situation of children with "aggression genes" raised in a poor environment. Some of these kids might turn out fine, but they have an increased risk for aggressive behaviors. Age is also an important factor according to a study by Gregory Carey & Donna R. Miles. Self-reports and parental ratings showed that while the family environment and genes are important in youth, at later ages the influence of genes increased but that of family environment decreased.

So what do these results tell us about aggression and genetics? They show that while genetics have an influence on aggressive behavior, it is not "aggressive genes" that are inherited whose presence will cause criminal tendencies and whose absence will result in a perfect child, but rather that genes can trigger a genetic sensitivity to the environment, causing the combination of bad genes and a bad environment to have bad results.