By Shen Gao
An age-old question involving social status and biology asks whether one’s social status can make one more healthy or more vulnerable to illnesses.
A study recently published in the Nov. 25 issue of Science gets at this specific question through an experiment, and concluded that living at the bottom of the social ladder may very well make you more susceptible to sickness.
Jenny Tung, an evolutionary biologist at Duke University, worked with colleagues and carried out an experiment with 45 female rhesus monkeys at the Yerkes National Primate Research Center field station in Georgia. Because rhesus monkeys are highly social, they make for good experimental subjects.
The scientists separated the monkeys into groups of five, but added monkeys separately into the group. This way, it resulted in the oldest member of the group being on the top of the social ladder while the newest member has the lowest rank.
The groups were observed for a year, and the researchers took notes on their behaviors, and collected blood samples to gauge changes in the cellular and genetic activities in the monkeys as compared to their social rank.
The researchers later regrouped the monkeys, grouping monkeys of the same rank together into five. The monkeys still maintained pecking orders—social status hierarchy—and the researchers still collected blood samples and observed their behaviors.
It turns out that low-ranking monkeys were harassed more and lacked a friend to hang out with. Subordinate monkeys, compared to high-ranking monkeys, participated less in grooming behaviors, which means that they get less of the social bonding that makes them feel good.
The low-ranking monkeys also had different proportions of immune system cells in their blood. In addition to their genetic activities, a physiological profile was presented that resembled harmful chronic inflammation. Cole explains that this type of inflammation aids the development of many chronic illnesses, including Alzheimer’s and cardiovascular disease.
Robert Sapolsky, who wrote a perspective in the same issue of Science, said, “at the end of the day, being a chronically subordinate nonhuman primate and being a human mired at the bottom of the socioeconomic scale are similar in the most fundamental ways. You have remarkably little control and predictability in your life, your outlets for frustration are limited, and it’s relatively hard to access social support. That’s the prescription for chronic, stress-related maladies.”