TIME: Almanac 1993/TIME Almanac 1993.iso/time/090991/0909300.000

Text File | 1992-08-28 | 7.6 KB | 165 lines

                                                                                SCIENCE, Page 60

Are Gay Men Born That Way?


A new study suggests that there is a structural difference between
the brains of homosexual and heterosexual men, but that is just
part of the story

By CHRISTINE GORMAN -- Reported by J. Madeleine Nash/Los Angeles


    Gay men often claim that even as children they knew they
were somehow "different" from other boys. Many say that sense
even preceded puberty. And yet, though researchers have tried
for decades to identify a biological basis for homosexuality --
which seems to be present in all human societies -- they have
mostly come up dry. Tantalizing clues have surfaced: gays are
more likely to be left-handed, for instance. But in the end,
there has been little proof that biology is sexual destiny.

    Now new research offers evidence that there may indeed be
a physiological basis for sexual orientation. In a study of 41
brains taken from people who died before age 60, Simon LeVay, a
biologist at San Diego's Salk Institute for Biological Studies,
found that one tiny region in the brain of homosexual men was
more like that in women than that in heterosexual men.
"Sexuality is an important part of who we are," notes LeVay, who
is gay. "And now we have a specific part of the brain to look
at and to study."

    That specific part is found at the front of the
hypothalamus in an area of the brain that is known to help
regulate male sexual behavior. Within this site, LeVay looked
at four different groupings of cells, technically referred to
as the interstitial nuclei of the anterior hypothalamus, or INAH
for short. Other researchers had already reported that INAH 2
and 3 were larger in men than in women. LeVay hypothesized that
one or both of them might vary with sexual orientation as well.

    Routine autopsies provided the tissue LeVay needed. All 19
homosexual men had died of AIDS. So had six of the 16 presumed
heterosexual men and one of the six women. Although LeVay hoped
to include lesbians in his study, he was unable to obtain brains
from women identified as such. After careful examination of the
brain samples, he found that the INAH-3 areas of most of the
women and homosexual men were about the same size. In straight
men this region was on average twice as large -- or about the
size of a grain of sand.

    In the past, much research on sexual orientation has
focused on the role of interpersonal relationships in early
childhood. Psychological literature is replete with material
suggesting that male homosexuality is triggered by relationships
with an overly protective mother or with a distant, even hostile
father. "Here is a whole other way of looking at the question,"
says LeVay. "These children may already be determined to become
homosexual or heterosexual. The development plan that is laid
out for them may be what causes them to develop certain troubled
relationships with their parents."

    LeVay's findings are certain to trigger a good deal of
controversy. Many technical aspects of the study are subject to
question, as the author concedes. He cannot be certain, for
instance, that all the heterosexual men in the control group
were heterosexual. And since the AIDS virus attacks the brain,
the size difference could be an artifact of the disease. It is
also possible that the difference actually has nothing to do
with sexual orientation or that it is the result rather than the
cause of homosexuality.

    "My freshman biology students know enough to sink this
study," declares Anne Fausto-Sterling, professor of medical
science at Brown University. Others are more receptive to
LeVay's work. "It makes sense," says Laura Allen, a
neuroanatomist at the University of California, Los Angeles.
Finding a difference in the INAH, which influences male sexual
behavior, "is what one would expect." The finding also has
social implications. "People who believe that sexual orientation
is a choice help legitimize discrimination against homosexuals,"
says Melissa Hines, a UCLA psychologist. "But if it is
immutable, or partly so, then that argues for legal
protections."

    The new study is the second to find some sort of
difference between the hypothalami of gay and straight men. Last
year a Dutch research team discovered that another group of
neurons in this tiny gland is larger in homosexual than in
straight men. But some scientists believe this structure governs
daily rhythms rather than sexual behavior, so it is difficult
to see any significance in the finding. Investigations of right-
and left-handedness have also provided evidence of a
physiological distinction. Sandra Witelson, a professor of
psychiatry at McMaster University in Hamilton, Ont., has found
more left-handers among homosexual women in her studies than
among heterosexual women. Others have made the same observation
among men. Since hand preference may be determined in part by
the influence of sex hormones on the brain during gestation,
Witelson believes these early hormonal influences could also
play a role in sexual orientation.

    Animal studies provide a good deal of evidence for a
biological basis of sexual orientation. Through careful
manipulation of hormone levels in newborn rats, Roger Gorski,
a neuroendocrinologist at UCLA, has been able to produce male
rodents that demonstrate feminine behavior. Other researchers,
working with mice, have noted that female fetuses that develop
between two male fetuses in a litter appear to be masculinized
to some degree by their brothers' testosterone. They look more
like males than females, mature more slowly, have fewer
reproductive cycles as adults and are less attractive to male
mice.

    In many species, particularly among mammals,
homosexual-like activity is an integral part of social
interaction. As any cattle rancher can attest, cows frequently
mount each other. Apparently this ensures that all the females
coordinate their reproductive cycles and then produce their
calves at the same time. Female rhesus monkeys mount other
females as a way of establishing a dominant rank in their
troop's hierarchy.

    Researchers estimate that a third of American males
experiment sexually with each other during their teen years,
even though approximately 9 out of 10 eventually settle into
relationships with girls. But both men and women may switch
gears later on or be bisexual throughout life. "There are some
people in whom sexual orientation does not maintain itself,"
says June Reinisch, director of the Kinsey Institute for
Research in Sex, Gender and Reproduction at Indiana University.
"It's not a matter of what they prefer, it's whom they fall in
love with." She cites the example of a woman who fell in love
with and was married to a man for 10 years, then at the age of
30 fell in love with a woman and spent 11 years in that
relationship, and at 41 fell in love with a man. Clearly, even
if sexual orientation does have a biological basis in the brain,
it is not necessarily fixed. "All of us believe that genetic and
hormonal influences are involved in homosexuality," says
Reinisch, "but there's also an interaction with the
environment."

    Over the years much research on homosexuality has been
motivated by a desire to eradicate the behavior rather than
understand, let alone celebrate, diversity. (A notorious German
biologist, for instance, claims that prenatal hormone injections
could act as a "vaccine" against homosexuality.) LeVay and
others hope their work will enable humans to view homosexuality
the way other species seem to see it: as a normal variation of
sexual behavior.