The enormous difference between male and female sexual behaviour may be explained, in animals at least, by a tiny organ in the nose rather than by any gender difference in brain circuitry.
So say investigators in the United States, who admit to being
stunned by the finding and the implications for the understanding of
In a study published by the British journal Nature, the
team engineered female lab mice so that the rodents lacked a gene
called TRPC2, effectively short-circuiting the so-called vomeronasal
This tiny organ in the nose is packed with receptor cells that pick
up pheromones - primitive scents that trigger aggression and sexual
responses in land-dwelling vertebrates.
Behaved like men
To the scientists' surprise, the mutant female mice behaved like men
at a Seventies disco night.
They sniffed and ran after females, flounced their pelvises, mounted
and thrust at male mice, issuing ultrasonic squeaks of the kind that
males emit to show lurv.
The behaviour was not all-male, though. The engineered mice mated
with males in a female-typical manner. And, unlike normal males, they
did not attack other males.
But when their babies were born, they again became feckless males,
insouciant about raising their offspring and keen on having more sex.
Usually, female mice spend around 80 percent of their time in their
nest nursing their newborns and while lactating will attack male
intruders and reject any attempt at a cuddle.
But, for the mutant mother mice, it was party time.
Abandoned their babies
Just two days after giving birth, they started to wander away from
the nest and eventually abandoned the babies altogether - and when a
male showed up, they were docile and receptive to courtship.
"These results are flabbergasting," said Catherine Dulac, a
professor of molecular and cellular biology at Harvard University and a
researcher with the Howard Hughes Medical Institute, who led the work.
"Nobody had imagined that a simple [genetic] mutation like this
could induce females to behave so thoroughly like males."
To check whether there could be any factors in the mutant mice that
could induce this dramatic behaviour change, the scientists surgically
removed the vomeronasal organs from the noses of normal female mice -
and the same thing happened.
The findings are important, because they amount to a massive blow to
those who for decades have looked for underlying differences in brain
structure to explain why sexual behaviour between males and females is
Wired the same
The answer appears to be this: in the mice at least, there is no
difference. The hard-wiring of the brains is the same.
"In the big picture, it suggests that the female brain has a
perfectly functional male behaviour circuit" which is repressed by
signals from the vomeronasal organ, said Dulac.
Seen from the perspective of developmental biology, "the finding is
very satisfactory," she added.
"It means you only have to build one brain in a species and that the
one brain is built, more or less, the same in the male and female."
The results do not apply directly to humans, as we and other higher
primates lack a vomeronasal organ. But they may open up new paths of
investigation into gender-specific human behaviour. – (Sapa-AFP)