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Seeing anyone special? Thinking about having kids? When am I going to have some grandchildren?
Many moms nag their adult children about the prospect of grandchildren. But bonobo moms take their maternal harassment to another level: They actively participate in helping their sons find mates.
Even more surprisingly, the pushy tactic gets results. The sons of overbearing mothers are more likely to father offspring, says a group of researchers.
“This is the first time that we can show the impact of the mother’s presence on a very important male fitness trait, which is their fertility,” Martin Surbeck, a primatologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, said in a press statement. “We were surprised to see that the mothers have such a strong, direct influence on the number of grandchildren they get.”
Bonobos are slender apes that live in groups of about a dozen in the lowland rainforests of the Congo Basin. Females and their young form the core of most groups. Males, even as adults, tend to stick with their mother’s group.
“In bonobo social systems, the daughters disperse from the native community and the sons stay,” Surbeck explained. “And for the few daughters that stay in the community, which we don’t have many examples of, we don’t see them receiving any help from their mothers.”
Sons, on the other hand, are coddled. Bonobo moms will make sure their sons attain good social standing, for example. And when it comes to mating, the mothers are on hand as well. In previous research, Surbeck and colleagues found bonobo moms make sure their sons are close to fertile females. The moms will even confront males that try to interrupt their sons’ mating attempts.
In the new study, the researchers combined genetic and demographic data from previous studies where they observed four wild bonobo communities. The analysis, which included paternity tests, revealed bonobo males living in a group with their moms were three times more likely to have kids than males living in groups without their mother’s presence, the team reports Monday in the journal Current Biology. Over the course of the research, about three-quarters of offspring were sired in the mom’s presence.
Why bonobo mothers are so assertive in helping their sons procreate is still unknown, but the researchers suspect moms are trying to ensure the continuation of their family tree.
“These females have found a way to increase their reproductive success without having more offspring themselves,” Surbeck said.