scmp.com, 01-07-2015, door Stephen Chen
It's a hormone thing: Chinese scientists find explanation
for women's smaller brain size
Male brains are about 10 per cent bigger than female brains, and now a group of
Chinese scientists think they have found the reason why, thus solving a riddle
that has confounded researchers for decades.
Oestrogen, the female sex hormone, was found capable of suppressing key genes
that regulate brain size, they reported in their paper, which was published in
the latest issue of the journal BMC Evolutionary Biology.
The team analysed seven genes that regulate the brain size of both humans and
non-human primates, and found that four were able to chemically bind with
The genes were then cloned and inserted into human embryonic kidney cells, where
they bonded with oestrogen in a way that impeded the way in which they function.
“Puberty plays an important role in shaping up the difference in brain
development between males and females,” the team said, adding that the
underlying mechanism behind this had been “unclear".
The study provided an explanation, because the sex hormones take effect at this
stage in a person's development.
The study was led by Professor Su Bing, who works for the State Key laboratory
of Genetic Resources and Evolution at the Kunming Institute of Zoology.
The institute operates under the Chinese Academy of Sciences. Kunming is the
capital city of southwest China’s subtropical Yunnan province.
To confirm the results, the researchers conducted extensive experiments on
The impact of oestrogen on the size of the brain was observed in three primate
species: chimpanzees, rhesus macaques and marmosets.
The researchers did not relate the brain size difference between men and women
to their intelligence.
“Why natural selection would favour a relatively smaller brain size in females
is not clear,” they wrote in the paper.
“One possible explanation is the different social roles of males and females,
which would lead to different selective pressures during evolution.”