Genetic Knowledge Explains. It Doesn’t Predict.

I’m Sara Katsanis and I am an instructor and a researcher at Duke Science and Society, and I research how genetic information is used or applied in medical testing, and D.N.A. forensics, and law enforcement.

Clearly genetics isn’t everything that contributes to how we look and how we behave. But there are certain traits that we can trace back to genetic roots. We can look at a genome and we can find genes that have certain characteristics. Maybe it’s a gene that receives salt on the surface of a cell, or maybe it’s a gene that makes skin color. We can see that a person who has albino doesn’t have melanin – does not produce skin pigment. So that is a genetic trait, and that is something that you can look at the genome and you can make a decision – say yes, that is clearly genetic.

We’re starting to see research come out looking at behavioral traits, which is far more difficult to measure than brown color or no color. When you’re looking at traits, it’s much more difficult to measure. Aggression and passiveness is one of those traits that people have tried to look at. When you’re looking at aggression and passivity, there is far more environmental input to how somebody portrays their personality. But it would be hard to sit here and argue that it’s entirely environmental.

There’s probably a significant amount of genetics that goes into behavioral traits. Unlike melanin, I doubt it’s one gene – it’s probably a network of genes that interact in different ways. Some of them are neurotransmitters, some of them are hormone receptors, hormone producers, there’s all sorts of different things that might go into how somebody acts and behaves. So just that is difficult to measure, all those different genes is hard to measure, much less all of the environmental factors that go into it – which is, is a person abused, is a person neglected, is a person with financial security, there are socioeconomic differences, there’s all sorts of things that might go into how a person behaves. What are the family dynamics? Are they a middle child or a young child or an old child? I mean, an eldest child. We see all sorts of differences, as only child or a family of 12.

All of these things are going to have an impact on how people behave. Now, all that said, there is evidence of particular genes and genotypes that are linked or associated with specific traits, like aggression. Each of those are – the ones that are studied, like MAOA, have not been well formulated enough to be predictive, to have predictive value. So we can look retroactively at individuals that express a particular genotype and say, “if that person with that genotype was abused as a child, then that person is going to become, or has become, aggressive as an adult.” And you can look at that same cohort and say those people with that genotype that weren’t abused are not aggressive as adults.

But it’s never going to be a one-to-one ratio, there’s always going to be some outliers and some differences. And when you’re measuring abuse – level of abuse – how do you do that? Is it if your parents are wonderful parents, but you have an older sibling that beat you up every Sunday – is that abuse? I don’t know, I’m not a psychologist, I can’t really quantitate that. But quantitating those kind of behaviors is very very difficult. So we see a genetic component underlying because we have these studies, and we see these associations, and there’s certainly a genetic component to how a person behaves, but there’s a lot we don’t know. We don’t know all the genes, we don’t know how to measure environmental impacts, and it’s certainly not predictive.

The other thing to consider when it comes to these genotype associations that have been made to aggression – those same associations have been made to people more likely to take risks, like credit scores. Highest credit scores are people that don’t have this assertion, and low credit scores are those that are people who have taken a lot of risks, and made some errors. You also see that maybe it’s not aggression, but assertiveness. Maybe if you’re not abused and you have this genotype, you’re more likely to become a high-powered CEO or Professor, rather than a serial killer or murderer.

To me, the underlying purpose of doing the research to understand behavioral traits is not for predictive value of using some sort of task to predict who is going to be a serial killer and who isn’t. Rather, it’s important to understand the mechanisms of the brain, and to know what turns on, what turns off, and how this thing works. We have so much to learn with regard to the brain. We know very little about the human genome, we know even less about the brain, even though we’re 20 years into the human genome, we’re only a few years into the BRAIN Initiative. We know very little. Understanding how the genetics influence the brain and how those neurotransmitters turn on and off, how the hormones work, this is all really important research, and part of that is doing behavioral genetics and understanding those underpinnings.

Using it to do predictive testing is far-fetched and has a lot of social implications that are going to require a lot of thinking and discussion before they’re put into action. I know that certain institutes might want to push for testing, might benefit from testing. Certainly our criminal justice system wants to do whatever we can to keep serial killers off the street. But there’s a – we have a social obligation to protect individuals, not to label them with a scarlet “S” for “potential serial killer.” So I think that that we’re a long, long, long way off from doing that kind of predictive testing, but it’s extremely valuable to understand the genetic underlying mechanisms of human behavior. This is all – this is what Leonardo da Vinci wanted to do. This is what, you know, all of the prior scientists are trying to understand – the human, and what makes us human, what makes us a human being. So that certainly genetics is a part of that, and that research is very important.