
Lv99_BixNood
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When a male bonobo oversteps his bounds — say, by hopping into a tree and shaking the branches while others are trying to feed — females in the troop tend to act fast.
They kick him, they chase him, they scream at him — getting so loud, according to behavioral ecologist Barbara Fruth, “you have to block your ears.”
Male bonobos are decidedly bigger than females. Yet unlike in so many other species with large differences in size between the sexes, when it comes to deciding when to mate and who gets first dibs at food, female bonobos tend to be the ones in charge.
For decades, it has been a mystery why females in this species of great apes, one of humanity’s closest living relatives, are perched so high in the hierarchy.
Now, scientists say they’ve found the secret to this paradox: Female bonobos maintain power by forming alliances to suppress male aggression.
“Male dominance is not evolutionarily inevitable,” said Harvard behavioral ecologist Martin Surbeck, who worked with Fruth on a study published Thursday in the journal Communications Biology.
The research shows that physical size and strength alone don’t determine power among these cousins of ours, offering potential lessons for humanity itself.
“Women are often victims of male violence around the globe,” said Laura Lewis, a postdoctoral fellow and biological anthropologist at the University of California at Berkeley who was not involved in the research. “This study could provide insight into how women could build power to better protect ourselves from male violence — by forming and maintaining coalitions, or alliances, with one another, just like our bonobo cousins.”
For their study, Fruth, Surbeck and their colleagues examined 30 years of observations of conflicts in six bonobo communities in the rainforests of the Democratic Republic of Congo.
At first, Surbeck thought the fact that females hold such sway in bonobo societies was tied to reproduction. Perhaps, he thought, females assert dominance by concealing ovulation from their male counterparts, giving them control over mating opportunities.
The power of female coalition formation came as a surprise to him. The vast majority of coalitions — 85 percent — involved females ganging up on males. And of the nearly 1,800 conflicts observed between males and females, females won about three-fifths of them.
Such attacks can leave males alone and injured for days or weeks. Witnessing one, Surbeck said, “really makes you like, ‘Gosh, male bonobo, I would not overstep certain boundaries.’”
“They’re scary as well for observers,” he added. “It’s a very efficient way to put the man in their place.”
Christopher Krupenye, a professor at Johns Hopkins University who studies cognition in great apes, praised the study for compiling a huge amount of data to find this statistical link.
But he added that more observations of how bonobo communities change over time are needed to determine whether coalition formation really gives the females power, or is simply a result of their already having power.
“In concert with related work in chimpanzees and other primates, it seems very likely that coalitions have been a tool for building and maintaining power for millions of years, dating back at least to our common ancestor with the other apes,” he said.
Why bonobos, of all animals, are so effective at forming female alliances remains unclear.
“I’m still puzzled,” said Fruth, a professor at Germany’s Max Planck Institute of Animal Behavior and senior author on the paper. “We might never know, but it gives me a glimmer of hope that females of our closest living relatives, in our evolutionary line, teamed up to take the reins of power alongside males.”
(((Bonobos))) at it again