THE shape of women鈥檚 breasts may have evolved to reduce the risk of mothers
smothering their infants while they are feeding, suggests a British researcher.
鈥淧artly because of the obsession with breasts as a sex object, there are big,
big gaps in our knowledge of how they actually work,鈥� says Gillian Bentley, a
biological anthropologist at University College London.
Evolutionary biologists have long speculated on the reason for the shape of
the human breast. Compared to the breasts of other primates, they are unusually
large. Mothers among our close relatives, such as chimpanzees and bonobos, are
all but flat-chested.
Because breasts don鈥檛 develop until puberty, biologists have suggested that
they help the female attract a mate and keep him interested in her welfare and
that of her children. Those with larger breasts were more successful, the theory
goes, and produced more offspring.
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But that explanation didn鈥檛 ring true for Bentley. For one thing, she points
out that the fascination with breasts is hardly universal. 鈥淎mong many cultures
where the breast is uncovered it isn鈥檛 such a source of erotic imagery,鈥� she
says.
The alternative explanation came to Bentley while she was feeding
her daughter. Bentley looked down and realised that if her breast didn鈥檛
protrude, her daughter鈥檚 nose would be buried in flesh while she was trying to
suckle. She would be in danger of being smothered. Could the breast have evolved
and enlarged precisely to give infants room to breathe?
Most primate infants aren鈥檛 at risk of suffocation, she realised, because
they have a protruding jaw and lips. So she suggests that the breast co-evolved
with human facial features. As the face became flatter, the breast became larger
to compensate. 鈥淚f infants were dying, that would have provided a very strong
selection,鈥� she says.
