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 Scientists said on Thursday a study of chimpanzees in Tanzania
spanning 17 years found that males that subjected females to
long-term aggressive behavior, often including physical attacks,
greatly improved their chances of fathering babies with them.
"It is certainly not a happy message," said Arizona State University
evolutionary anthropologist Ian Gilby, one of the researchers.
"Males who directed aggression toward females at high rates were
more likely to sire those females' offspring than less violent males
were. This effect was particularly strong for high ranking males (in
the chimpanzee community)," Gilby added.
The study involved an ape species that is a close genetic cousin of
humans but the researchers were wary about making conclusions about
the origins of sexual violence in people.
The researchers knew from detailed long-term observations of this
chimp community in Tanzania's Gombe National Park which ones had
mated with one another as well as the paternity of 31 babies born
during the study period from 1995 through 2011 based on DNA
collected from fecal matter.
"The hypothesis is that females are intimidated by long-term
aggression from the male so that they acquiesce or even solicit
mating from the male when they are fertile, and avoid mating with
other males in his presence for fear of further aggression from the
male," said Duke University evolutionary anthropologist Anne Pusey,
one of the researchers.
The aggressive behavior by the males included violent physical
attacks including biting and striking that sometimes caused wounds
as well as chasing the female and engaging in outbursts in which the
male charges and strikes nearby foliage.
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Mating did not take place during or immediately after the bullying.
In fact, it was serial aggressive behavior over two or three years
that was particularly effective in later securing fatherhood.
The researchers found that females at their time of peak fertility
actively sought to mate with the males that bullied them.
The researchers noted that the evolutionary lineage for humans and
chimps split some 7 million years ago and that the mating systems
for the two species are different.
"Nevertheless, recognizing the adaptive value of male-female
aggression in chimpanzees may inevitably help us to understand, and
hopefully prevent, similar behavior among humans," Gilby said.
The research was published in the scientific journal Current
Biology.
(Reporting by Will Dunham; Editing by Sandra Maler)
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