Infidelity Gene: Sensational, but Science?

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a respected UK newspaper, announced last Wednesday, “Cheating Women
May Blame Their Genes.”

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.

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.”

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.”


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
, a scientific journal.) No analysis of methodology
or other key factors has been apparent, for instance.

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.”

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.

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.

observation invalidates the study; they merely provide reason for
enhanced scrutiny.

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.

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

Spector study is part of the “nature versus nurture” debate, which
has been defined
“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.”

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.

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.

“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.

concern is the possible misuse of methodology.

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

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

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).

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.

merely one objection that has specific application to the Spector’s

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.

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

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

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.

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.

study smacks of sensationalism, not science.

8, 2005

McElroy [send her mail]
is the editor of
and a research fellow for The
Independent Institute
in Oakland, Calif. She is the author and
editor of many books and articles, including the new book, Liberty
for Women: Freedom and Feminism in the 21st Century

(Ivan R. Dee/Independent Institute, 2002).

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