In many species, older females – mothers and grandmothers – play a fundamental role in sustaining the family structure . Of course it occurs among humans, but also in other primates such as bonobos ( Pan paniscus ), in whose society the role of females in ensuring offspring and maintaining the family clan is even more important than previously believed.
A scientific study from the department of Primatology at the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) has shown that bonobo mothers act as celestines so that their male children more easily find fertile females with whom to mate and have sexual intercourse . This ensures that they will have more grandchildren. The results of this curious investigation have been published in the journal Current Biology .
In many facets, bonobos are considered the primate species with the most behavioral similarities to humans , more even than chimpanzees. We now know that females are decisive for the organization of family groups, as confirmed by this new study. In addition to exercising matriarchy in many daily activities, bonobas assert their status and hierarchical position in the clan to ensure that their male descendants can flirt with females that are in full reproductive phase. For that they even get in the way in the event that another male outside the family tries to take the partner from his son. According to Professor Martin Surbeck, one of the authors of the study, “it is the first time that we can show the impact of the mother’s presence in influencing such a crucial male trait as fertility. We were surprised to see that mothers have such direct and decisive power in the number of grandchildren that they manage to help bring to the world ”.
The team responsible for the research carried out their field work with wild bonobo populations in the Democratic Republic of the Congo , and also studied groups of chimpanzees in the Ivory Coast, Tanzania and Uganda. The scientists found that both bonobo mothers and chimpanzee mothers tried to help their offspring, but found that the former were much more successful because the females occupy the highest hierarchies in their communities . In contrast, chimpanzee communities are dominated by males competing to assert themselves as alpha individuals.
“Bonobo moms act a bit like passports or social facilitators. As the sons are very close to them, they can access positions within the group that allow them to interact more with other females, including copulating more easily. Near a very attractive young and fertile female there are always mothers around, and in their shadow are their little males waiting for their opportunity ”, says Surbeck. The study authors found that in the case of bonobo, if a mother lost her hierarchical position, her son also descended in rank and consequently had less success in their mating attempts.
Interestingly, bonobo mothers did not go the extra mile for their daughters in this regard, nor did they assist them with raising their offspring. Surbeck’s hypothesis is that since young bonobo males remain in the community and daughters leave to emancipate themselves, their mothers are not worth the time from an evolutionary perspective.
The team of researchers believe these are tests to demonstrate the so-called ” grandmother hypothesis “: that a female who has already passed the reproductive phase can perpetuate her genes if she ensures the reproductive success of her offspring. It is an idea that anthropologists wield for human societies and that Surbeck estimates could also work among bonobo populations. “The interesting thing is that among bonobos, this mechanism is used by older females, but curiously not through their daughters but through their sons.”
