Relationship between social status and wound-healing in wild baboons

Results of a study by University of Notre Dame biologist Beth Archie and colleagues from Princeton University and Duke University finds that male baboons that have a high rank within their society recover more quickly from injuries, and are less likely to become ill than other males.

The finding is somewhat surprising, given that top-ranked males also experience high stress, which should suppress immune responses.

Archie, Jeanne Altmann of Princeton and Susan Alberts of Duke examined health records from the Amboseli Baboon Research Project in Kenya. They published their results in this week's issue of the journal Proceedings of the National Academy of Sciences.

The scientists also found that social status is a better predictor of wound-healing than age.

"The power of this study is in identifying the biological mechanisms that may confer health benefits to high-ranking members of society," says George Gilchrist, program director in the National Science Foundation's (NSF) Directorate for Biological Sciences, which co-funded the research with NSF's Directorate for Social, Behavioral & Economic Sciences.

"We know that humans have such benefits, but it took meticulous long-term research on baboon society to tease out the specific mechanisms," says Gilchrist. "The question remains of causation: is one a society leader because of stronger immune function or vice versa?"

Although research on health and disease in animals in laboratory settings has been extensive, this study is one of the most comprehensive conducted on animals in a natural setting, the scientists say.

The researchers examined 27 years of data on naturally-occurring illnesses and injuries in wild male baboons. They investigated how differences in age, physical condition, stress, reproductive effort and testosterone levels contribute to status-related differences in immune function.

Previous research found that high testosterone levels and intense reproductive efforts can suppress immune function and are highest among high-ranking males.

However, Archie and colleagues found that high-ranking males were less likely to become ill and recovered faster from injuries and illnesses than low-ranking males.

The authors suggest that chronic stress, old age and poor physical condition associated with low rank may suppress immune function in low-ranking males.

"The complex interplay among social context, physiology and immune system-mediated health costs and benefits illustrates the power of interdisciplinary research," says Carolyn Ehardt, program director in NSF's biological anthropology program.

"This research begins to tease apart the trade-offs in both high- and low-status in primates--including ourselves--which may lead to a new understanding of the effects of social status on death and disease."