- Men have bigger brains to help them in
the search for sexual partners, a study suggests.
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- The theory emerged following the latest
research into why men have larger brains than women.
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- Researchers now plan to test their working
hypothesis - that the extra brain mass is used for visuospatial skills.
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- They point to evidence that men can read
maps better than women and have a better awareness of their surroundings.
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- These essential tools in the search for
sexual partners would mean that large-brained men would be more likely
to make it through the perils of natural selection.
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- More grey matter
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- The researchers found that humans are
not the only primates where males have larger brains than females.
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- They conclude this means men's larger
brains did not come about through development of the higher cognitive abilities
that distinguish humans from other primates.
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- Instead, they say, it could be because
they have better visuospatial skills.
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- Men's brains are on average one tenth
larger than women's, with a mean weight of 1347g compared to 1223g.
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- Professor Dean Falk, of Albany University
New York, wanted to see if the difference existed in other primates too.
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- She and colleagues examined rhesus monkeys
and discovered a similar disparity in brain size between the sexes.
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- The significance of comparing rhesus
monkeys to humans lies in earlier studies of voles.
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- Some species of vole are polygynous -
meaning they go in search of sexual partners during mating season - while
others are not.
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- Scientists who have studied voles have
found differences between the sexes in such species.
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- Professor Falk said: "They have
shown that in those species and only in those species you have extensive
differences between the sexes in their mapping skills and their visuospatial
skills with males outperforming females.
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- "We were wondering if the difference
we see in humans - with men have bigger brains than women - and an equivalent
difference we see in rhesus monkeys had something to do with the visuospatial
skills."
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- Men consistently outperform women at
such visuospatial tasks such as the mental rotation of figures and map
reading. This could be what they use the additional brain mass for.
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- Sex search
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- Usually in primates other than humans,
one sex leaves the birth group in search of a mate to prevent inbreeding,
Professor Falk said.
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- "When rhesus monkeys reach puberty
it's the males who change birth groups and travel away.
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- "It's possible that in terms of
our own evolution many millions of years ago that in our own species it
was men who did the wandering."
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- The researchers plan to test their theory
by examining rhesus monkeys' visuospatial skills.
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- They will also look at macaque monkeys,
where it is the female who wanders away from the birth group, Professor
Falk said.
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- "Whatever they wander for,"
she added, it was likely to help them survive natural selection because
they would be "perpetuating their genes into the future".
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- "It's good to have good visuospatial
skills - anything that allows the individual to live longer and reproduce
itself."
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