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Of course, everyone knows it’s true, right? It was
reported on National Public Radio, in The Wall Street Journal and
The New York Times, after all. “Research Points Toward
a Gay Gene,” the Journal said. “Report Suggests Homosexuality
Is Linked to Genes,” read the Times.
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Can you believe everything you read in the
paper? Is there such a thing as a gay gene?
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They were all reporting
the release of a study in Science magazine in July 1993 that
purported to find a genetic cause for homosexuality. Though the necessary
caveats were added to the news stories, most people would already
have turned off the radio or turned the page, thinking that homosexuality
is caused by a gene.
But can you believe
everything you read in the paper? Is there such a thing as a gay gene?
In the study the media
was trumpeting, molecular geneticist Dean Hamer and his colleagues
had performed a new kind of behavioral genetics study now becoming
widespread—the so-called “linkage study.” Researchers
identify a behavioral trait that runs in a family and is correlated
to a chromosomal variant found in the genetic material of that family.
Hamer’s study identified a link on the q28 region of the X chromosome
in homosexual males.
Defining
Terms
Even though a trait
may have a chromosomal link, it does not necessarily mean it is genetic.
Genetic traits are those, such as eye colors, that are coded for us
by genes alone.
Each human gene can
be thought of as a book that provides a complex set of instructions
for the synthesis of a single protein. These proteins are then responsible
for forming and operating everything else in the body.
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Demonstrating that any behavioral state is
not only biological but genetic is well beyond our present
research capacity.
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Behavioral traits,
such as weight, are influenced by genetics, but unlike genetic traits,
most behavioral traits are programmed by multiple genes and things
such as the environment in the womb, the mother’s health habits
or postnatal effects of a virus. All of these and more may combine
and influence one another throughout a lifetime. Behavioral traits,
as opposed to simple, single-gene physiologic traits such as eye color,
always interact in this way.
Demonstrating that
any behavioral state is not only biological but genetic is well beyond
our present research capacity. This is especially true for something
so complex and nuanced as homosexuality. One psychiatric researcher,
Brian Suarez, calculated that at least 8,000 people would be required
for a study to confirm a behavioral trait as genetic. No study of
homosexuality has come remotely close to these requirements.
Contested
Evidence
As it is, the Hamer
study is seriously flawed. Four months after its publication in Science,
a critical commentary appeared in the same publication. It took issue
with the many assumptions and questionable use of statistics that
underlie Hamer’s conclusions, but not with his research methods
and raw data, which met acceptable standards for linkage studies.
Genetics researchers
from Yale, Columbia and Louisiana State Universities noted that much
of the Hamer report focused on social and political ramifications
of genetic homosexuality rather than discussing scientific evidence.
They also indicated that the results were not consistent with any
genetic model and should be interpreted cautiously.
Hamer responded, indicating
that his research was not conclusive that Xq28 underlies sexuality,
only that it contributes to it in some families, and that its influence
was statistically detectable in the population that he studied.
Hamer gave another
report in a 1994 issue of Science devoted to behavioral genetics.
He indicated that complex behavioral traits are the product of multiple
genetic and environmental agents. He clarified that “environment”
meant not only social environment but also the flux of hormones during
development, whether you were lying on your right or left side in
the womb and a number of other factors.
Science revisited the topic this year, publishing two articles questioning supposed
links to a gay gene. Both articles reference an independent genetic
study conducted in Canada in 1989 with research continuing today by
four researchers from the University of Western Ontario and Stanford
Medical School. This study used 52 pairs of gay siblings from 48 families
æHamer’s research used 40 homosexual brother pairs. The study
concluded, “It is unclear why our results are so discrepant from
Hamer’s original study. Because our study was larger than that
of Hamer et al., we certainly had adequate power to detect
a genetic effect as large as was reported in that study. Nonetheless,
our data do not support the presence of a gene of large effect influencing
sexual orientation at position Xq28.”
In other words, any
claim to have found a “gay gene” were overblown if not outright
wrong.
Figuring
It All Out
What can we conclude
about the biology of homosexuality? Consider a comprehensive review
article, “Human Sexual Orientation: The Biological Theories Reappraised,”
written by William Byne and Bruce Parsons from Columbia University
in 1993.
The article reviews
135 research studies, prior reviews, academic summaries, books, and
chapters of books—in essence the entire literature on homosexuality,
of which only a small portion is actual research. The abstract summarized
in its findings that there is no evidence at present to substantiate
that biological factors are the primary basis for sexual orientation.
Whatever genetic contribution
to homosexuality exists, it probably contributes not to homosexuality
per se, but rather to some other trait that makes the homosexual “option”
more readily available to some than others.
Most studies to date
have many flaws. Some are caused by the intrusion of political agendas
into what should be objective research, and some are due to the complex
nature of the subject. These flaws must temper any conclusions we
make. It is premature, and will almost certainly prove to be incorrect,
to state that homosexuality is genetic.
Dr.
Jeffrey Satinover is the author of Homosexuality
and the Politics of Truth. He is a former Fellow in Psychiatry
and Child Psychiatry at Yale University. He holds degrees from MIT,
the University of Texas and Harvard. He serves as a medical adviser
to Focus on the Family.
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