Your genes are just the odds

By Razib Khan | June 29, 2010 4:55 am

Morning Edition has a strange story today about the exploration of one neuroscientist of his own family’s history, specifically its psychological and neurological quirks. To not put too fine a point on it, the scientist in question finds out that he has a history of violence in his family, and, that he carries a genetic variant implicated in violent behavior under particular conditions, as well as telling neurological patterns found among psychopaths. Here’s the relevant section:

After learning his violent family history, he examined the images and compared them with the brains of psychopaths. His wife’s scan was normal. His mother: normal. His siblings: normal. His children: normal.

“And I took a look at my own PET scan and saw something disturbing that I did not talk about,” he says.

What he didn’t want to reveal was that his orbital cortex looks inactive.

“If you look at the PET scan, I look just like one of those killers.”

Fallon cautions that this is a young field. Scientists are just beginning to study this area of the brain — much less the brains of criminals. Still, he says the evidence is accumulating that some people’s brains predispose them toward violence and that psychopathic tendencies may be passed down from one generation to another.

The Three Ingredients

And that brings us to the next part of Jim Fallon’s family experiment. Along with brain scans, Fallon also tested each family member’s DNA for genes that are associated with violence. He looked at 12 genes related to aggression and violence and zeroed in on the MAO-A gene (monoamine oxidase A). This gene, which has been the target of considerable research, is also known as the “warrior gene” because it regulates serotonin in the brain. Serotonin affects your mood — think Prozac — and many scientists believe that if you have a certain version of the warrior gene, your brain won’t respond to the calming effects of serotonin.

Fallon calls up another slide on his computer. It has a list of family members’ names, and next to them, the results of the genotyping. Everyone in his family has the low-aggression variant of the MAO-A gene, except for one person.

“You see that? I’m 100 percent. I have the pattern, the risky pattern,” he says, then pauses. “In a sense, I’m a born killer.”

Fallon is being a bit dramatic for effect obviously, but as I said to Eric Michael Johnson this is like finding out you have a history of alcoholism in the family, as well as a genetic variant which results in the less efficient metabolization of alcohol. You know what you know, and you know what you have to do to not put yourself in a position where your predispositions could mix with a dangerous set of choices.

Going back to this example and being more practical, what if behavior genomics and neuroscience advance to the point where you can find out the odds of your child having issues with impulse control, heightened aggression, and reduced independent ethical judgement (e.g., guilt as opposed to shame) are all greater than than expectation. All things being equal the research is telling you that instead of having a 0.1% chance of landing in jail for violent crime, your offspring has a 5% chance. There are all sorts of things you might do, and choices you might make. If, for example, you yourself know that guilt is just something you aren’t heavily gifted with, and that gets you intro trouble in the long term (as you make a sequence of ‘rational’ unethical choices on a regular basis), you might choose a profession which is very transparent so that you don’t have to make ethical decisions on a regular basis where short term self-interest is in conflict with long term self-interest & socialized conceptions of right & wrong. Go into finance if you can do math. Become a lawyer if you can’t.

CATEGORIZED UNDER: Behavior Genetics
MORE ABOUT: Behavior Genetics

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Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at


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