Nurturing friendships is the best strategy for chimpanzees | Sciences

Our closest cousins ​​among the great apes, chimpanzees and bonobos, took two completely opposite evolutionary paths when preparing for their reproductive success. Chimpanzees walk the thorny path of violence and coercion to ensure offspring: males who outsmart females the most, for example, are more likely to mate. Bonobos, on the other hand, continued the Silk Road: the males do not know when the fertile period of the female is, who in turn leads the group in the maternal system, betting on mating a lot to increase the chances of procreation.

But there’s a strange side to biologists: If the selfish gene thinks only of reproduction at all costs, in unfettered competition between males, why would chimpanzees dedicate themselves to pampering, petting and caressing, picking up lice and mutually grooming their fur? What evolutionary sense does it mean to strengthen friendships with those who will take your chance at childbearing? Joseph Feldblum, principal zoologist at the University of Michigan, explains, “We would only expect to see these strong and friendly social relationships or relationships if they offered some kind of benefit to individuals. Males would not spend that much time caring for other males and give up trying to find females or food unless they get some kind of gain from it.”

On Tuesday, Feldblum published a study in the scientific journal prison cell He tests the idea with a surprising result: Males cultivate friendships because they work. Thanks to decades of data collected in Gombe National Park (Tanzania) since the days of Jane Goodall, scientists have been able to analyze the ancestors of males who are related to other mates, compared to those who do not. And they get two results: the first is not surprising, and the thing that was already known: the males with the greatest contact with the alpha male in the community gain possibilities for reproduction. It makes sense: in this patriarchal system, the alpha controls the female and allows its friends to mate. “Pulling a president’s ass is nothing new,” says study co-author Ann Posey, from Duke University (USA), who has spent three decades organizing and digitizing this unique data set. “We’ve shown it has always been worth it,” he adds.

However, scientists have found that males who spend more time with other middle-ranking males in society double their chances of having offspring. The probability of a male chimpanzee having children increases by 50% if he maintains at least two strong friendships with other equivalent individuals. With the exception of alpha, ranking in the group hierarchy does not affect the chances of reproductive success, but rather the presence of many friends to devote time and attention to. The strategy is not violent competition, but peer cooperation.

bonobos and people

In other words, contrary to what it means to simplify the evolutionary perspective, the winning strategy is not to be the strongest or most aggressive, but rather to be the most enthusiastic about friendships. Feldblum believes more studies are needed to understand how these social connections lead to success. Perhaps it is the ability to form aggressive alliances with mates that aids males with their mating opportunities, and it is precisely the formation of these bonds that is responsible for reducing the need for repeated aggression. But we still need to investigate.”

The primate scientist asks, “If your ally is present, are you more likely to mate with a female in heat, or does the presence of allies around you protect you from harassment from other males? Or, as your ally will support you in the event of a conflict, your stress levels are lower And can you devote more energy to mating efforts?” The researchers note that this is the first time that the effect of social contact on male reproductive capacity has been studied, because this perspective has always applied only to females.

Researchers believe that having a clearer idea of ​​the benefits of these social relationships in chimpanzees provides clues about the development of friendship between humans, explains Ian Gilby, the study’s lead author. “Together with bonobos, chimpanzees are our closest living relatives and help us identify unique features of human social life. This study indicates that strong bonds between males have deep evolutionary roots and provide the basis for the most complex relationships we see in humans,” says Gilbey. from Arizona State University in a press release. “This study also underscores the value of long-term studies, which are essential to understanding the biology of a species that lives for many decades and reproduces slowly,” he adds.

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