Ask any new dad, and he'll tell you — having a new baby in the house is no picnic.
Anthropology professor Patricia Whitten recently uncovered evidence that, in communities of the earliest primates, newborns stress out the guys. "I'm looking at different aspects of hormones and behavior in wild primates to understand humans better," says Whitten, who specializes in the links between behavior, biology and reproduction.
Whitten's lab at Emory has an international reputation for the analysis of steroid levels in fecal samples of wild primates. The data can help reveal all sorts of complex social dramas, from the emotional impact on baboons after a relative is killed by a lion, to the secrets of monkey mating strategies.
In 1998, she began collaborating with Diane Brockman of the University of North Carolina in a study of sifaka lemurs in Madagascar. Lemurs are prosimian primates –believed to be the forerunners of more advanced primates like apes and monkeys.
The study results, recently published by the Proceedings of the Royal Society B, found that male sifaka become more anxious during the annual birthing season. Whitten initially thought that the rise in glucocorticoid levels in males could be tied to an environmental factor. She was surprised that the data pointed instead to the presence of a new infant.
Males are Nurturing, but Stressed
Field observations revealed another surprise: male sifaka play a nurturing role with infants, grooming and caring for them. But the correlation between higher stress in males and the birthing season remains a mystery.
One hypothesis is that the males are worried about aggression by males from neighboring groups: Sifaka males roam and visit other groups of sifaka during the birthing season. Sometimes the visitors challenge the dominant male of a group. Occasionally, they will even kill infants.
For Whitten, the complex dramas revealed by the initial study raise more questions. For instance, why do the female sifaka sometimes allow visiting males to hold their newborns? "The females are dominant, so they are choosing which males are trustworthy – but sometimes they don't seem to be choosing that well," Whitten says.
Whitten is well-known for her groundbreaking studies of wild vervet monkeys, but the prosimian primates – believed to have originated 65 million years ago – offer her a glimpse further back.
"In anthropology, we commonly talk about one million years of evolution, or five million," Whitten says. "If we start looking at behavior going back 65 million years, think how much more deeply ingrained that may be."
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