Life at the bottom of the social hierarchy stinks, especially if you're a rhesus macaque. Being unpopular makes it harder to find a mate, plus you're more likely to be stressed out. Low social status among rhesus monkeys even seems to lead to an overactive immune system. The result: unpopular monkeys may be more likely to become ill. This is more than just a correlation of poor health hurting social rank; researchers from Duke University have noted that a drop in social status directly influences immune-system-related gene expression in macaques.
Researchers placed 49 female rhesus macaques into brand-new social groups. These macaques had all been of medium status in their initial groups, but being thrown together led to the negotiation of a new social hierarchy, with some at the top and some at the bottom. The researchers later took blood samples from the monkeys in order to analyze the expression of over six thousand different genes. 535 of the sampled genes were more highly expressed in high-ranking macaques, and 452 more highly expressed in the low-ranking macaques. A significant number of the genes in the latter, low-ranking category relate to immune function and inflammation, suggesting that lower-ranked macaques tended to have overactive immune systems, which leaves them more susceptible to disease.
Using the gene expression data alone, researchers could predict a macaque's social rank—high, medium, or low—with 80 percent accuracy. However, on a bright note, this change in genes wasn't permanent. When the researchers again shook up the ranks, the monkeys' gene expression changed once more to correspond to their new status. They concluded that it is status that affects gene expression, rather than the other way around.
Could we have the same problem? We're not rhesus macaques, but low socioeconomic status has long been correlated with poor health in human beings. One famous study notably found that that low-ranking British civil servants suffer higher rates of illness and death than their superiors. Of course, rank has more nuance within highly complex human society than it does in macaque bands, but perhaps we should still take note of this message from our distant cousins: that feeling worthless to your group could literally make you sick.
photo by Einar Fredriksen