L*******e 发帖数: 2202 | 1 http://www.huffingtonpost.com/2012/06/12/why-are-there-gay-men_
While female sexuality appears to be more fluid, research suggests that male
gayness is an inborn, unalterable, strongly genetically influenced trait.
But considering that the trait discourages the type of sex that leads to
procreation — that is, sex with women — and would therefore seem to thwart
its own chances of being genetically passed on to the next generation, why
are there gay men at all?
Put differently, why haven't gay man genes driven themselves extinct?
This longstanding question is finally being answered by new and ongoing
research. For several years, studies led by Andrea Camperio Ciani at the
University of Padova in Italy and others have found that mothers and
maternal aunts of gay men tend to have significantly more offspring than the
maternal relatives of straight men. The results show strong support for the
"balancing selection hypothesis," which is fast becoming the accepted
theory of the genetic basis of male homosexuality.
The theory holds that the same genetic factors that induce gayness in males
also promote fecundity (high reproductive success) in those males' female
maternal relatives. Through this trade-off, the maternal relatives' "gay man
genes," though they aren't expressed as such, tend to get passed to future
generations in spite of their tendency to make their male inheritors gay.
While no one knows which genes, exactly, these might be, at least one of
them appears to be located on the X chromosome, according to genetic
modeling by Camperio Ciani and his colleagues. Males inherit only one X
chromosome — the one from their mother — and if it includes the gene that
promotes gayness in males and fecundity in females, he is likely to be gay
while his mom and her female relatives are likely to have lots of kids. If a
daughter inherits that same X-linked gene, she herself may not be gay, but
she can pass it on to her sons. [Why Are There Gay Women?]
But how might the "gay man gene" make females more reproductively successful
? A new study by Camperio Ciani and his team addresses the question for the
first time. Previously, the Italian researchers suggested that the "gay man
gene" might simply increase androphilia, or attraction to men, thereby
making the males who possess the gene homosexual and the females who possess
it more promiscuous. But after investigating the characteristics of 161
female maternal relatives of homosexual and heterosexual men, the
researchers have adjusted their hypothesis. Rather than making women more
attracted to men, the "gay man gene" appears to make these women more
attractive to men.
"High fecundity, that means having more babies, is not about pleasure in sex
, nor is it about promiscuity. The androphilic pattern that we found is
about females who increase their reproductive value to attract the best
males," Camperio Ciani told Life's Little Mysteries.
Turns out, the moms and aunts of gay men have an advantage over the moms and
aunts of straight men for several reasons: They are more fertile,
displaying fewer gynecological disorders or complications during pregnancy;
they are more extroverted, as well as funnier, happier and more relaxed; and
they have fewer family problems and social anxieties. "In other words,
compared to the others, [they are] perfect for a male," Camperio Ciani said.
Attracting and choosing from the best males enables these women to produce
more offspring, he noted.
The new study will appear in an upcoming issue of the Journal of Sexual
Medicine.
Of course, no single factor can account for the varied array of sexual
orientations that exist, in men as well as in women. "It is quite possible
that there are several influences on forming a homosexual orientation," said
Gerulf Rieger, a sexual orientation researcher at Cornell University. He
noted that environmental factors — including the level of exposure to
certain hormones in the womb — also play a role in molding male sexuality.
But as for why genetic factors would exist that make men gay, it appears
that these genes make women, as well as gay men, alluring to other men. | m******1 发帖数: 19713 | 2 哈哈,这篇文章来得正是时候。不过,我觉得我的性取向也是天生的,而且没觉得可以
fluid。 | L*******e 发帖数: 2202 | 3 哈哈,这篇解释男性"同志基因"的文章确实没有解释女同基因的问题,所以它附送了一
篇Why Are There Gay Women?
http://www.lifeslittlemysteries.com/2563-gay-women.html
Straight women are much more likely to get themselves knocked up than gay
women. So, in terms of evolution, they would seem to have a much better
chance of passing on their genes, while at the same time it would seem that
the genes that make women gay would quickly vanish from the gene pool. This
raises the question, why are there gay women?
Lesbianism is at least 25 percent genetic, as determined by a 2011 study of
twins conducted in the United Kingdom. The study found that identical twin
sisters (who share 100 percent of their DNA) are more likely to both be
lesbians than are fraternal twin sisters (who share just 50 percent),
proving that, all other environmental factors being equal, genes matter.
While scientists have a theory for how male homosexuality propagates from
one generation to the next, no one has yet produced a viable explanation for
how the genes that promote lesbianism might do the same.
A female's sexual orientation also appears to be partly influenced by her
level of exposure to the male sex hormone androgen when she is in the womb.
Greater hormone exposure correlates with more gender nonconformity early in
her life (as a child, she may be called a "tomboy") as well as a same-sex
orientation later on. However, opinions differ on the extent of the role
played by hormones.
Greatly adding to the confusion about what causes lesbianism is the
slipperiness of female sexuality itself. Unlike men, who are usually
sexually oriented solely toward men or women, and whose sexuality is
essentially fixed from puberty on, women are thought to have greater "erotic
plasticity." Their sexual orientation can be shaped by cultural influences,
altered by positive or negative experiences and intensified by feelings of
love or attachment. This fluidity may emerge from the fact that, across the
board, women are sexually aroused by images of both men and women (while men
are typically only aroused by members of one sex or the other).
Therefore, the question "why are there gay women?" may be better worded as "
why is female sexuality so fluid?" Plenty of women exist at both extremes of
the straight-gay spectrum, but it is the formation of this slippery
spectrum itself that most needs explaining. Evolutionary biologists have yet
to determine what survival or reproductive benefit women's "erotic
plasticity" confers. |
|