Female baboons²（狒狒） that maintain closer ties with other members of their troop live substantially longer than do those whose social bonds are less stable, a recent study has found. The researchers say that the findings, reported online on July 1st in Current Biology, a Cell Press publication, add to evidence in animals from mice to humans that social bonds have real adaptive value（适应值） . "Our results suggest that close, stable social relationships have significant reproductive benefits," said Joan Silk of the University of California, Los Angeles. "The data add to a growing body of evidence from humans and other animals that females with a strong, supportive social network are healthier and have greater reproductive success."

Silk said that she and her colleagues were surprised to discover that the effects are at least partially³ independent of a given female's status in the group. In other words, the benefits of social ties don't just derive⁴ from（源自，来自） greater competitive ability or greater access to resources for those of higher dominance rank.

"Given that high-ranking females have priority of access to food resources, one might have predicted that rank would be the primary factor influencing longevity⁵," said Dorothy Cheney of the University of Pennsylvania. "Our results indicate instead that the quality of a female's social bonds with other females is more important, suggesting that subordinate females may be able to offset⁶ the competitive disadvantage of low rank through their social relationships."

The quality and stability of baboon¹ relationships trump⁷ quantity, the researchers say. Females who were able to maintain the same grooming⁸ partners from one year to the next lived longer and had more surviving offspring（后代，子孙） .

Baboons most often form close bonds with relatives, the researchers said, and the stability of those connections is partly a matter of luck since lions and leopards⁹ often prey¹⁰ upon baboons. But it appears that isn't the whole story. The researchers found that 80 percent of females that switched close grooming partners from one year to the next did so despite that fact that their earlier companion was still in the group.

Silk and Cheney said they aren't exactly sure how the relationships lead baboons to live longer lives, but it might have something to do with lower stress levels in those with dedicated¹¹ grooming partners. It's also possible that females with such networks are more likely to be resting and foraging¹²（觅食） near other animals, making them less vulnerable to predators¹³.

The findings in baboons may lend humans some added insight into our own social lives, the researchers said.

"Having friends is important for us and for female baboons—and maybe for some of the same reasons," Silk said. "Our findings are strikingly similar to evidence from humans showing that social ties have important effects on our mental and physical health and our longevity. We suspect that the human motivation to form close and lasting¹⁴ friendships has a very long evolutionary¹⁵ history."