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What's in Your Head Is in Your Genes

Dean Hamer is head of the Section on Gene Structure and Regulation at the U.S. National Cancer Institute. He and his colleagues made headlines when they discovered genes linked to behavior, including sexual orientation, thrill seeking, and anxiety. His 1994 book The Science of Desire (with journalist Peter Copeland) was a New York Times "Notable Book of the Year." He and Copeland have written a new book, Living with Our Genes, about temperament--the inborn, genetic factors in personality--and character: the way you learn to play with the genetic cards you're dealt. Amazon.com's Mary Ellen Curtin spoke with Dr. Hamer at the American Association for the Advancement of Science conference in Philadelphia, and by telephone.

Question: What particular scientific advances made you decide to write this book?

Dean Hamer: It was really the discovery for the first time of specific genes that are linked to normal variations in human behavior and personality. Like our own finding of a gene for novelty seeking and one for anxiety. That's a new thing, in psychology and in genetics.

Question: To what extent do you think the cloning revolution is going to affect the application of this knowledge?

Hamer: Immediately it will not have any application because I don't think people are going to be cloning humans. Obviously cloning is not all that exciting, because you'd just be copying people. What you might want to do is to make slightly improved people; one can imagine making an improved version of oneself. That might be attractive to some people, but we're not working on that. I don't think it's going to happen anytime in the near future.

Question: I suppose most of the first changes are likely to be in pharmaceuticals.

Hamer: The first application will be diagnosis. It's not inconceivable that pretty near in the future psychiatrists will still listen to you--that's what's important--but they'll also take a look at your DNA chip and see whether your serotonin transporter is this form or that form, how your dopamine looks, and so forth.

Question: When you say "in the near future," what kind of time frame do you mean?

Hamer: I could see that within the next decade. People are doing experiments right now to see if genotype affects response to psychiatric drugs.

Question: At the AAAS meeting you said that perhaps 60 percent of all 100,000 human genes are expressed in the brain. What do you think all those genes are doing?

Hamer: I think they are setting up the very, very intricate architecture and wiring that are required for proper brain functioning. We have so many different parts of the brain, each of them are anatomically distinct, and the wiring patterns are very complex and very interconnected. And one of the things about the brain is that it's incredibly sensitive to small changes in chemistry...

Question: Which is why I'm drinking a cup of coffee right now!

Hamer: Right. That cup of coffee is changing your adenosine levels, it's changing cyclic AMP [adenosine monophosphate]. You'll feel it physically a little bit, but you'll most of all feel it in your brain because your brain's the most sensitive. It's for this same reason that there are some biochemical abnormalities--phenylketonuria, for example--that hurt your body very little but cause profound mental retardation: because your brain is so sensitive to things working exactly the way they're supposed to work.

Question: If some tens of thousands of human genes are expressed in the brain, do you think people can draw conclusions about what you can and can't expect when, say, selecting or engineering for intelligence?

Hamer: It's going to depend very much on the architecture of a trait. If the trait is actually getting input from tens of thousands of genes, then engineering any one of them is going to have hardly any effect at all. And I think that'll probably be the case for intelligence. I suspect other traits will be simpler. I think some basic emotional traits will probably have a smaller number of genes, so changing one of them might have a noticeable effect. Whether that's a good idea or not is another issue--I'm not convinced that it is.

Question: There has been some recent research about a great increase in certain affective disorders (such as depression) as countries industrialize. What do you think causes that?

Hamer: Well, there's the Unabomber hypothesis--that we've set up a society that's a terrible environment for people, where everybody's regimented and has to work and so forth. I think it may be partly that, and it's partly just because we're more sensitive to it now. People used to hide their depression better. What is clear is that it's obviously not a genetic change--it's way too short a time for our genes to change. That's a clear indication that indeed all these cultural and social factors do have an influence.

Question: What part of your book do you find people are most interested in?

Hamer: It depends on the person. A lot of people are really interested in the sex chapter--the Clinton effect. But people who have problems with anxiety are most interested in that chapter, people who have a weight struggle are interested in that chapter. That's just what I hoped, that people would find a topic that's of importance to them and that everybody will find some topic of all of these that impinges on their life.

Question: What idea presented in the book is hardest for people to grasp?

Hamer: Still the hardest idea is that these genes act quantitatively rather than qualitatively and that genes can influence a trait without determining it. People always have this tendency of wanting to see things in black and white.

Question: Do you think people can really come to understand the quantitative aspects of genetics?

Hamer: Yes, I think people can. I think people use quantitative thinking in their own lives all the time. When people think about their weight, for example, they realize that it's multifactorial, that it depends on how many banana splits you have minus the hours you spend on the treadmill. So it's just a matter of hearing it enough, having it become part of popular culture. I'm a big believer in the educability of people.

Question: So would that be the message you want people to get from the book?

Hamer: That genes are very important for just about everything, but that very important is different from all-determining. There are lots of other things that affect a person's behavior, including lots of things people can change.

Living With Our Genes : Why They Matter More Than You Think by Dean H. Hamer, Peter Copeland
The Science of Desire : The Search for the Gay Gene and the Biology of Behavior by Dean Hamer, Peter F. Copeland


The Human Nature Review
Ian Pitchford and Robert M. Young - Last updated: 28 May, 2005 02:29 PM

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