CHICAGO — Males have greater reproductive success if they spend more time taking care of kids, not necessarily only their own, according to new research conducted by anthropologists at U.S. Northwestern University.
The researchers found in a previous study that wild male mountain gorillas living in Rwanda help take care of all of the kids that live in their social group, regardless of whether they are the father.
In the new study, they further found that male mountain gorillas who groom and rest more with kids end up having more reproductive opportunities.
“We’ve known for a long time that male mountain gorillas compete with one another to gain access to females and mating opportunities, but these new data suggest that they may have a more diverse strategy. Even after multiple controls for dominance ranks, age and the number of reproductive chances they get, males who have these bonds with kids are much more successful,” said Stacy Rosenbaum, lead author of the study and a post-doctoral fellow in anthropology at the university.
This research suggests an alternative route by which fathering behaviors might have evolved in our own species, Rosenbaum said.
“We traditionally have believed that male caretaking is reliant on a specific social structure, monogamy, because it helps ensure that males are taking care of their own kids. Our data suggest that there is an alternative pathway by which evolution can generate this behavior, even when males may not know who their offspring are,” Rosenbaum said.
This raises the possibility that similar behaviors could have been important in the initial establishment of fathering behaviors in distant human ancestors.
The researchers are also investigating whether hormones might play a role in helping facilitate these male behaviors, as they do in humans.
“In human males, testosterone declines as men become fathers, and this is believed to help focus their attention on the needs of the newborn,” said Christopher Kuzawa, Northwestern University professor of anthropology.
“We’re working on characterizing these males’ hormone profiles across time, to see if events such as the birth of new infants might be related to their testosterone levels,” Rosenbaum said. “We’re fortunate to have data that span many years of their lives.”
The research is scheduled to be published on Monday in Scientific Reports.