The ranking of a monkey within her social environment and the stress accompanying that status dramatically alters the expression of nearly 1,000 genes², a new scientific study reports. The research is the first to demonstrate a link between social status and genetic³ regulation in primates⁵ on a genome-wide scale, revealing a strong, plastic link between social environment and biology. In a comparison of high-ranking rhesus（恒河猴） macaque females with their low-ranking companions, researchers discovered significant differences in the expression of genes involved in the immune response and other functions. When a female's rank improved, her gene¹ expression also changed within a few weeks, suggesting that social forces can rapidly influence genetic regulation.

"We were able to use gene expression to classify individuals based on their rank," said Yoav Gilad, PhD, associate professor of human genetics at the University of Chicago Biological Sciences and senior author of the study in PNAS. "Demonstrating these very plastic and temporal changes was novel and quite interesting."

The research, led by University of Chicago postdoctoral researcher Jenny Tung, was conducted with rhesus macaques housed in groups of five at the Yerkes National Primate⁴ Research Center in Atlanta. As in the wild, each group self-organizes into a dominance hierarchy⁶, defined by which individual yields first during competition over food, water and grooming⁷ partners. In captivity⁸, dominance is determined⁹ by the order of introduction into the group, giving researchers an opportunity to study how changes in rank lead to biological effect.

"In the wild, females would not ordinarily leave the social group they were born into," said Tung, PhD, now an assistant professor of evolutionary¹⁰ anthropology¹¹（人类学） at Duke University. "They inherit their social rank from their mothers. But in this unnatural¹² situation, order of introduction determines rank -- the newcomer is generally lower status."

Previous research on rhesus macaques discovered that social rank influenced components¹³ of the stress response, brain, and immune system. With gene chip technology for measuring the expression of over 6,000 different genes, Tung, Gilad and colleagues at Yerkes, Emory University, and Johns Hopkins looked for the first time in primates at the effects of social rank on genetic function.

Comparing 49 different female monkeys of different rank revealed significant changes in the expression of 987 genes, including 112 genes associated with immune system function. The result fits with data in monkeys where low rank and chronic¹⁴ stress lead to compromised immune function, and, more loosely, with human studies linking low socioeconomic status and high social stress to elevated disease risk.