A yet to be published study from London found that genetic make-up constitutes an "important influence" in women's infidelity "with a heritability of 41 percent." But studies purporting to quantify the genetic basis of complex human behavior should be approached with caution.

The media has not been displaying such caution. News of the "infidelity gene" quickly hit headlines around the world: the New York Post declared, "Cheating's in the DNA for Ladies."

Health Talk Canada stated, "Some Women Cheat Because It's In Their Genes." The Melbourne Herald Sun informed its readers, "One in five women cheat - and it's genetic."

India, Ireland, South Africa....

From the superficiality of reports, the media seems to have relied on a brief press release rather than the study itself. (The study is due out in the December Twin Research, a scientific journal.) No analysis of methodology or other key factors has been apparent, for instance.

The press release itself should have raised questions. For example, lead researcher Professor Tim Spector states that the study "lends support to evolutionary psychologists' theories on the origins of human behaviour."

As the author of the popular 2003 book "Your Genes Unzipped: How Your Genetic Inheritance Shapes Your Life", Spector has both a bias and a vested interest in proving these theories true.

Spector also declares, "this study justifies additional genetic and molecular research on human sexual behaviour," thus leading me to wonder if the study is a preamble to increasing the funding to his research.

Neither observation invalidates the study; they merely provide reason for enhanced scrutiny.

Based on the press release, I can neither evaluate the study nor validate its conclusions by uncritically repeating them. But I can offer some of the questions and points of skepticism with which I'll approach the full study when it is readily available.

One concern is the political atmosphere that surrounds current theories of human behavior and the political uses of such "research."

The Spector study is part of the "nature versus nurture" debate, which has been defined as "a popular phrase used to describe debates over the relative degrees to which one's genetic makeup (nature) and one's life experiences (nurture) influence one's traits and behavior."

The extent to which the debate has been politicized can be measured by the furor that surrounds any research indicating there may be innate differences between the races in terms of intelligence and abilities, or that homosexuality may be genetically based.

Many left-wing causes favor an extreme "nurture" argument. Radical feminists go so far as to argue that a so-called predisposition toward motherhood or heterosexuality is actually learned behavior. Thus they seek to deconstruct the institutions of society, such as the family and the free market, in order to reconstruct them to promote the 'correct' set of learned behaviors.

Extreme "nature" arguments, such as those that claim to quantify a genetic tendency toward infidelity, can be no less political. Discussions of "gene therapy" or the genetic screening of children already abound.

Another concern is the possible misuse of methodology.

The "Twin Study," upon which Spector's research is based, is a common methodology for researchers who attempt to uncover a significant or defining contribution of nature. The studies compare identical with non-identical (fraternal) twins in order to look for traits that have greater similarity in identical twins than in the non-identical ones, whose differences make them more susceptible to environmental factors.

Researchers then assume that the greater similarity indicates a genetic basis for the trait, which is assigned a percentage based on its prevalence.

Twin studies are particularly valuable in researching medical conditions such as diabetes. But it is far from clear that the methodology of hard science (medicine) applies with equal force to researching soft sciences (psychology or sociology).

Volumes have been written in opposition to applying the scientific method or mathematical measurements to human behavior, especially in attempting to predict it, as Spector's study seems to do.

Consider merely one objection that has specific application to the Spector's research:

If, as Spector concludes, specific behaviors such as infidelity are genetically based, then his conclusion calls the validity of his research methods into question. Why? Because the home environment is generally considered to be the primary source of nurture-based behavior; it is a primary check on what is nature-based. Behavior that cannot be ascribed to nurture such as behavior learned in the home is automatically ascribed to nature. A negative correlation is assumed.

The home environment is largely defined by the parents' behavior. But according to Spector, that behavior may also be genetically based. The home, therefore, ceases to be a reliable measure of "nurture." In short, Spector's study creates a paradox that calls itself into question.

Other reasons for approaching the "infidelity gene" with skepticism are less philosophical. One is simply that the nature versus nurture debate is notoriously abstract.

No clear lines of measurement have been established between the two concepts of "nature" and "nurture." The human genome has been sequenced, but only a small fraction of its genes are accurately known, and even fewer have known functions.

No one knows how genes may interact. It seems premature to say the least for anyone to talk about an "infidelity gene" let alone to assign precise percentages to its impact on behavior.

The study smacks of sensationalism, not science.

Copyright © 2004 Wendy McElroy.