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[escepticos] ¿Cómo andan de dedos?
La próxima vez que deis la mano a alguien, aprovechad
para fijaros en la longitud de sus dedos. Si es varón y
tiene el índice y el anular aproximadamente iguales,
como yo, ojo.
¿Alguien puede garantizar que esto va en serio?
Saludos
JM
------------------------
Handy guide
Do a person's fingers
reveal their sexual orientation?
YOUR early life as a fetus
may have influenced your sexuality as an adult--and
your fingers
tell part of the story.
Researchers in California have used relative finger
lengths to show
that sexual orientation is
partly determined by events in the womb.
In animals, prenatal
exposure to the male sex hormone testosterone seems to
influence
sexual orientation. But it
is not easy to measure fetal hormone levels in humans.
One
indirect way is to look at
the size of a person's fingers. In women, the index
finger, called
the second digit or 2D, is
about the same length as the ring finger, 4D. In men,
the ring
finger is often
considerably longer, leading to a lower 2D:4D ratio.
This sex difference is
clear from infancy, and
researchers attribute it to masculinising hormones
during fetal
development.
Marc Breedlove and his
colleagues at the University of California at Berkeley
wanted to
know if gay people had
different finger length ratios from straight people, so
they
surveyed 720 adults during
street fairs in San Francisco. The researchers
collected
information about gender,
age, sexual orientation, handedness and older siblings.
They also
carefully measured the
lengths of the volunteers' fingers.
They found something
striking in gay women: their index to ring finger
ratios resembled
those of heterosexual men.
This suggests that at least some lesbian women were
exposed
to higher than average
levels of male hormones before birth.
What they found in men is
less clear-cut. The 2D:4D ratio in gay men was not
significantly
different from that in
straight men. But a series of studies in the 1990s had
shown that
the more older brothers a
boy had, the more likely he was to be gay, so the
researchers
sorted the volunteers
according to numbers of older brothers. They found that
all the men
who had two or more older
brothers had significantly smaller 2D:4D ratios. "It
was a big
surprise to me that the
finger measures would follow the epidemiology so
closely," says
Breedlove.
The findings suggest that
homosexuality is partly due to higher levels of
prenatal
testosterone in men as well
as women, he says. But they also show that fetal
hormones
alone don't determine
sexuality. First-born males have indistinguishable
2D:4D ratios,
whether they are gay or
straight, yet some first-born males are gay. So other
factors
clearly come into play,
says Breedlove.
To some researchers, the
idea that gay men are "hypermasculinised" seems
counterintuitive.
John Manning of the
University of Liverpool has found the opposite in gay
men: that their
finger ratios veer more
towards the feminine. He suspects that both very low
and very
high levels of testosterone
in the womb could produce homosexuality. "There may be
more
than one phenotype of male
gays," he says.
Manning also wonders if
Breedlove's data may have been slightly muddied because
the
research did not take
account of ethnicity. He has found big population
variations in 2D:4D
ratios. "The geographical
differences swamp the sex differences," says Manning.
"There's
more difference between a
Pole and a Finn than between a man and a woman."
Source: Nature (vol 404, p
455 )
Alison Motluk
(in http://www.newscientist.com/nl/0401/fingers.html)