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from "Born that way" theory
Italian Researchers Believe That
Genetic Factors May Increase Fertility In Mothers Of Gay Males
October 14, 2004 - A team of researchers at the University of Padova in
Italy believe they have may have found a genetic factor in women that both
boosts fertility and produces homosexual sons. The study "Evidence for
maternally inherited factors favouring male homosexuality and promoting female
fecundity," was published in the latest issue of the British Proceedings of the
Royal Society: Biological Sciences.
Researchers led by Dr. Francesca Corna submitted questionnaires to 98 homosexual
and 100 heterosexual men in Northern Italy.
An analysis of the data showed that maternal relatives of homosexuals had
slightly higher reproductive success-- in the admittedly limited-size sample of
this study-- than those of heterosexuals, and that the differences did not
appear in the paternal line. They did not study lesbians.
The team noted that mothers of gay men produced an average of 2.7 babies
compared to 2.3 born to mothers of straight men.
Researcher Dr. Camperio-Ciani says that whatever genetic factors are involved,
this does not involve a single gene.
The New Scientist reported the findings this way: "The researchers discovered
that women tend to have more children when they inherit the same--as yet
unidentified--genetic factors linked to homosexuality in men. This fertility
boost more than compensates for the lack of offspring fathered by gay men, and
keeps the gay genetic factors in circulation."
Camperio-Ciani says this maternal effect, however, impacts only 7% of the
population at most. Maternal and immune effects account for only 21%, leaving
79% percent of the causation of homosexuality still a mystery. According to
Camperio-Ciani, "Genes must develop in an environment, so if the environment
changes, genes go in a new direction. Our findings are only one piece of a much
larger puzzle on the nature of human sexuality."
The researchers stressed that there was ample room left for the influence of
non-biological factors linked to culture and upbringing.
A report in Nature magazine provided additional commentary on this study.
Michael Hopkin wrote: "Besides having more fecund mothers and aunts, homosexual
men had more fellow homosexuals in their maternal family, again hinting that
their sexuality is influenced by their mother's genes. What's more, homosexual
men were more likely to have older brothers, which supports a separate theory
that homosexuality is linked to changes in the mother's immune system during
previous male pregnancies."
The journal Nature concluded:
"...this study shows that, although there may not be a 'gay gene,' it is possible
that genetic factors can influence sexuality. 'We strongly believe that this set
of genes influences sexual expression, but they don't determine it,' said
Camperio-Ciani says."
Updated: 8 February 2008
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