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- Male mountain gorillas who spend more time caring for children are more successful at breeding
- Research challenges scientists' assumptions about paternal care in gorillas and other primates
- Researcher: "Our findings suggest an alternative pathway by which evolution would eventually have led to father-in-law behavior in humans."
EVANSTON, Ill. — According to a new study published by anthropologists at Northwestern University, men are more successful in reproduction if they spend more time looking after children – not just theirs.
In a previous study, researchers found that male wild mountain gorillas living in Rwanda are doing something quite unusual for a mammal: they help take care of all the children in their social group, that 's what they do. they are or are not fathers. . The purpose of the new study was to understand why.
"Mountain gorillas and humans are the only great apes in which men regularly develop close social ties with children, so find out what mountain gorillas are doing and why they help us understand how men may have started. to engage in the path of our more committed fatherhood, "said Stacy Rosenbaum, lead author of the study and postdoctoral fellow in anthropology at Northwestern.
Christopher Kuzawa, a co-author of the study, said the findings go against what we usually think of male mountain gorillas – huge, competitive and with breeding in the group dominated by a single alpha male.
"Men spend a lot of time with groups of children – and those who flourish and rest more with them have more opportunities for reproduction," said Kuzawa, a professor of art. Anthropology at Northwestern and faculty member of the Institute for Policy Research of the University. . "One likely interpretation is that women choose to marry men based on these interactions."
Rosenbaum added, "We have long known that male mountain gorillas compete for access to females and offer them mating opportunities, but this new data suggests that they might have a more diverse strategy. Even after multiple checks for the ranks of domination, the age and the number of chances they have to procreate, men who have these ties to children are much more successful. "
This research suggests an alternative path through which paternity behaviors may have evolved in our own species, said Rosenbaum.
"We traditionally believed that child care depends on a specific social structure, monogamy, because it ensures that men take care of their own children." Our data suggest that there is a another path through which evolution can generate this behavior, even when males may not know who their offspring are, "said Rosenbaum.
This raises the possibility that similar behaviors may have been important in the initial establishment of paternity behaviors in distant human ancestors.
Researchers are currently studying whether hormones could help facilitate these male behaviors, as they do in humans. A fundamental work on the hormonal changes that men experience when they become fathers and take care of children was conducted in the Northwestern Anthropology Department.
"In men, testosterone decreases as men become fathers, and this would help focus their attention on the needs of the newborn," said Kuzawa, co-author of a study on this topic in the Proceedings Journal of the National Academy of Sciences in 2011. "Do gorillas that are particularly engaged in interactions with infants experience a similar decrease in testosterone?" Because this would likely hinder their ability to compete with other men, the evidence of a decline in testosterone would clearly indicate that they should like attracting friends. Otherwise, if this does not decrease, it suggests that high levels of testosterone and guarding should only not necessarily be mutually exclusive among mountain gorillas. "
Researchers are eager to explore these new issues. "We are working to characterize the hormonal profiles of these men over time, to see if events such as the birth of newborns could be related to their testosterone levels," said Rosenbaum. "We are fortunate to have data covering many years of their lives."
The lead author of the study, Tara Stoinski of the Dian Fossey Gorilla Fund, added that such work underscores the crucial importance of long-term research.
"In the 1960s, Dian Fossey went to study these mountain gorillas in hopes of better understanding the evolution of humans," Stoinski said. "More than 50 years later, ongoing research on this population still provides information not only about a species at risk of extinction, but also about what it means to be human."
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"Infant care is associated with increased breeding success among male mountain gorillas" will be released Oct. 15 Scientific reports. Besides Rosenbaum, Kuzawa and Stoinski, the paper was co-authored by Linda Vigilant of the Max Planck Institute of Evolutionary Anthropology, Leipzig, Germany.
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