Life at the bottom of the social hierarchy stinks, especially if you're a rhesus macaque. Not only do you have fewer reproductive opportunities, but you're more likely to be stressed out and sick. In fact, low social rank in this species of monkeys even seems to affect gene expression, particularly of genes relating to the immune system. Far from being simply a correlation of poor health hurting social rank, researchers were able to see how a drop in social status directly influenced the macaque's gene expression and general health.

Researchers put 49 female rhesus macaques into new social groups, shaking up their social ranks. They then sampled white blood cells from the monkeys to analyze the expression of 6,097 different genes. 535 of the sampled genes were more highly expressed in high-ranking macaques, and 452 in the low-ranking macaques. A significant number of the genes in the latter category relate to immune function, suggesting that lower-ranked macaques tended toward overactive immune systems. Using the gene expression data alone, researchers could predict a macaque's social rank with 80 percent accuracy.

Could human societies have the same problem? A low socioeconomic status has long been correlated with poor health, but it seems hasty to draw conclusions about us from this macaque study. Still, we share enough our our biology with other primates that it deserves further investigation, among geneticists, biologists, and public health officials alike.

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