How Genes Affect Personality

There can be no doubt that the prickliest issues in modern genetics are not scientific ones. Ethicisits and geneticists both find themselves forced to examine and reexamine assumptions society makes about people. It is assumed, for example, that all men are created equal, to some measure or another. But what if one man is so naturally predisposed towards violence that he cannot control himself under certain situations in which normal men would exercise control easily? Can society justly imprison a man who, in his own mind, may have done little more than engage in self defense, even if it appears to us to have been aggression?

Geneticists have identified a number of genes that are loosely tied to a general set of personality traits. For example, there is a gene dubbed the “monogamy gene” in men, that controls a batch of hormones that are thought to be correlated with the ability to remain in long term, stable relationships. Another is the aggressiveness gene, which predicts whether a man is likely to become physically violent when angry. The problems in identifying whether a gene “causes” a personality trait are several. The first, and most significant, is that genes are often not expressed. The presence of a gene does not ensure that the individual carrying it will exhibit the symptoms of its presence. Further, even if a gene is expressed, the extent to which it is expressed can vary from one individual to another.

The next problem is that of “polygenic traits,” or traits that are controlled by the group action of a number of genes. Thus, even if most persons who exhibit a particular behavior possess a certain gene, it could be by happenstance. Or, it could simply mean that the presence of that gene is a predictor of the presence of other genes that cause the trait. Yet another issue is that of the environment. Some genes put you at risk for a condition, but do not ensure its presence. The trait will often only appear if certain environmental triggers are present. Autism works that way, as do a number of other behavioral conditions.

Much as it serves no useful purpose to look for genetic differences between races, in hopes of finding indications of “superiority” in one, and “inferiority” in another, it is arguably fruitless to look for the genetic underpinnings of behavior. The results are unreliable, and in the long term, humanity may be better off not prejudicing itself against its members purely on the basis of an assumed genetic predisposition.