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Slate's Medical Examiner: The Genetics of Desire


This is DAY TO DAY. I'm Alex Chadwick.


And I'm Madeleine Brand. Scientists may have found a gene that determines sex drive. There's a gene that's long been associated with different personality types. Now, it looks like it's also responsible for different sexual personalities. Dr. Sydney Spiesel of the Yale Medical School joins us now to talk about how that gene works. Dr. Spiesel writes the Medical Examiner column for the online magazine Slate, and we are so lucky to have him in studio with us today. Hi, Sid.

Dr. SYDNEY SPIESEL (Yale Medical School): Hi, it's so nice to be here.

BRAND: Now, let's start with what we already know about this gene and how it affects personality types.

Dr. SPIESEL: Years ago, people began to think that genes in this category might be important in determining behavior and styles of behavior. There's some people in the world, as we all know, who like novelty, like things changed.

BRAND: So these are risk takers.

Dr. SPIESEL: These are risk takers, and people who fell into the category of high novelty seeking also seem to have higher chance of having attention deficit disorder. People said, aha, that's a really important area, let's see if we can find a gene that will help us identify the causes of attention deficit, hyperactivity disorder.

BRAND: So researchers have found this link between the gene and human sexuality.

Dr. SPIESEL: Well, yeah, it turned out, at least in this very preliminary study, and I can't stress enough how preliminary this is - the study was done in Israel by two important researchers on the genetics of behavior. One was a guy named Dr. Benzion(ph) and the other was a Dr. Epstein. And it was reported in a journal called Molecular Psychiatry, which is becoming an increasingly important journal.

What they did was they took just under a 150 people for whom they knew the status of the gene. So they send out questionnaires on the Internet asking if they'd be interested in participating in a study of sexuality, and 148 people agreed to do it. It was all done anonymously. And they found, indeed, that people with the variant of the gene that tended to make them novelty seeking, that might've been related to attention deficit disorder, these people were stronger in a collection of sexual attributes, like they were stronger in sexual desire, and higher in arousal and their function seemed to be better. Now, putting all together there seems to be a connection.

BRAND: So, Sid, does this mean that you can't do anything about your sex drive? You're either born with a high sex drive or a low sex drive because you either do or don't have this particular gene?

Dr. SPIESEL: I doubt that that's true. This is probably just one of many, many factors. I'll tell you - can I tell you an interesting thing about this gene?

BRAND: Please.

Dr. SPIESEL: This particular change, the one that's associated with greater sexual desire and so forth, is a relatively new mutation in human history and it probably originated about 40 or 50,000 years ago, right about the time the humans were first immigrating out of Africa. And with most genes, if a change in a gene is clearly helpful, more people with that gene will reproduce and that gene will replace the less valuable one. This is an interesting gene because it seems to have been maintained. These two forms of the gene has seemed to have been maintained in balance for these 40 or 50,000 years. And it looks as if it's to the advantage of the species if both forms of the gene are retained.

BRAND: The high sex drive and the low sex drive.

Dr. SPIESEL: The high sex drive, and it may not be sex drive. You know, another aspect of the gene is that the aspect that's associated with lowered drive and lowered desire is also associated with altruistic behavior, pro-social behavior.

BRAND: So both forms are good for a human society, because you've got half the population out populating, if you will, and the other half taking care of those who are populated.

Dr. SPIESEL: Yeah, although the actual ratio around the world is probably about 80 percent, 70 or 80 percent of the more pro-social, more altruistic, and 30, 20 or 30...

BRAND: And the lucky 20 percent...

Dr. SPIESEL: Yeah.

BRAND: Well, thank you, Sid.

Dr. SPIESEL: My pleasure, always nice to be here.

BRAND: Opinion from Sydney Spiesel. He's a practicing pediatrician and a contributor to Slate.com. Transcript provided by NPR, Copyright NPR.