These bonobos surprised the researchers with their skewed reproductive results.
While it may not be the most exact description, some experts from a study on bonobos nicknamed an adult male within one community ‘Brad Pitt’ because he was found to have fathered the most children and been with the most females. Bonobos, along with chimpanzees, are the closest living relatives to humans and are often studied in order to study human nature. This last study, which involved ‘Brad Pitt’s’ community as well as 5 chimpanzee communities, revealed interesting information about mating patterns.
In the study, researchers looked at paternity information for infants born over a 12-year period and found that Camillo, an adult male found in a bonobo community in the Democratic Republic of Congo, had sired more than 60 percent of the infants. This means that a reproductive skew and the tendency for females to mate with the same male is present in the community, but it’s not entirely clear why.
“The funny thing under such a scenario would be that most of the females would have the same preference for Camillo, the alpha male and ‘Brad Pitt’ of the bonobos at our research site,” said Martin Surbeck of the Max Planck Institute for Evolutionary Anthropology in Germany.
The study started as a look at whether the friendly relationships formed between males and females within bonobo communities led to greater paternity success for the male. Since bonobos are known to be non-aggressive and peaceful primates, unlike their chimpanzee cousins, and researchers assumed that this loving nature and the freedom of choice for females would mean greater distribution between paternal mates. Their assumptions wound up being wholly wrong.
Researchers tested the paternity of 24 bonobo offspring born between 2002 and 2013 living within the same community. They found that a shocking 62 percent of babies were sired by Camillo; by comparison, the chimpanzee that sired the most children out of the 5 groups studied had only fathered 51% of the offspring. Male chimpanzees, who often resort to violence to coerce females to have sex with them and compete aggressively with other males, were originally thought to have a smaller paternal pool because of this competition.
“Unlike chimpanzees, where all adult males outrank all adult females, and even the lowest-ranking males can coerce females into mating, there appears to be a greater role for female choice in bonobos,” said Kevin Langergraber, who works with Arizona State University’s School of Human Evolution and Social Change and ASU’s Institute of Human Origins. “Perhaps they choose high-ranking males.”
Experts are now speculating that the freedom to choose a sexual partner has led females to consistently choose who they deem the alpha male. In this case, that’s Camillo. Despite spending tons of time observing both bonobos and chimpanzees, researchers say they were still beyond surprised at the findings of this study. Since only one community was studied, they will have to replicate this experiment with other communities to see if the reproductive skew exists elsewhere.
As for Camillo, researchers say he spends most of his free time with his mother. Mothers play an important part in the life of their male offspring and in the larger community because they often solve disputes. It has been observed that an involved mother has even been able to facilitate sexual relations between their son and another female, even if the son is low-ranking in the community because of their ability to problem solve and their desire to extend their lineage.