Wed, May 22, 2019 page7

• Pushy bonobo mothers manage their sons’ sex lives

  MATRIARCHAL MUSCLE: High-ranking mothers help their sons find mates and keep guard as they mate, ensuring more offspring, but do not do the same for daughters

  • AFP, WASHINGTON
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  Anyone who has experienced a mother pushing them to get a move on and produce grandkids might just sympathize with this.

  A new study has described the outsized role bonobo moms play in their sons’ sex lives: from pulling rank to ensure their male offspring get to meet attractive ovulating females, to interfering with male rivals’ attempts to mate.

  The paper was published on Monday in the journal Current Biology and found that bonobo males whose mothers were alive and remained in their group were three times more likely to father children.

  

  A juvenile male bonobo, right, is groomed by his mother in the Kokolopori Bonobo Reserve in the Tshuapa District of the Democratic Republic of the Congo in an undated photograph provided by the Max Planck Institute for Evolutionary Anthropology on Monday.

  Photo: AFP / Max Planck Institute for Evolutionary Anthropology / Martin Surbeck

  The authors credited the success of the “wingmoms” on the nature of bonobos’ female-dominant societies, which have long been known for their altruistic and peaceful character, in contrast to more violent and patriarchal chimpanzees.

  “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,” coauthor Martin Surbeck, a primatologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, said in a statement.

  “We were surprised to see that the mothers have such a strong, direct influence on the number of grandchildren they get,” he said.

  For the study, Surbeck and colleagues observed wild bonobo populations in the Democratic Republic of the Congo, as well as wild populations of chimpanzees in Ivory Coast, Tanzania and Uganda. To verify paternity, they collected the primates’ droppings for DNA analysis.

  They found that while both bonobo and chimpanzee mothers attempted to assist their sons, bonobos were far more successful because their communities’ highest ranks are dominated by females.

  Chimpanzee communities are dominated by males who compete for alpha status.

  “The bonobo moms act a bit like social passports,” Surbeck said. “The sons, in close proximity to their moms, are also very central in the group and access positions in the group that allow them to interact more with other females, including copulation.”

  “If there’s a female who’s very attractive, you see moms stick around them, and in the shadow of their moms are the males,” he added.

  By contrast, the researchers found that if a mother lost her high rank, her son also fell in rank and was subsequently less successful in his mating attempts.

  In addition to intervening in their sons’ rivals attempt to mate, bonobo mothers also protected their own sons from the efforts of rivals to disrupt courting and sex, but they did not do so for their daughters, nor did they help their daughters raise offspring.

  Surbeck believes that, since bonobo daughters leave the community and males remain behind, it might simply not be worth the mothers’ time and efforts from an evolutionary perspective.

  One thing the team believes they might now have tentative evidence for is the so-called “grandmother hypothesis”: that a post-reproductive female can increase her own lifespan and continue her genes by ensuring her offspring’s reproductive success.

  It is an idea that anthropologists have applied to humans and Surbeck believes it could also be the case for bonobos.
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