Being low on the pecking order often means poorer health — but why?
Megan Mendenhall, Duke Univ.
Jenny Tung, 36
Genetics and evolutionary anthropology
He played so much because he found it “a big, fat, hairy challenge,” Wenny said, proposing that Jenny, too, is drawn to challenges by their difficulty.
Jenny Tung protests. Yet she doesn’t deny that her research tackles a big, hairy question: Why does a tough social life go along with worsening health, even a greater risk of death?
Tung, 36, combines evolutionary anthropology and genomics at Duke University to answer this “why,” from the tiniest details of what social adversity does to DNA to the vast evolutionary forces that shape connections between genes and social life.
Social scientists have long observed that people of high social status tend to live longer than those on society’s bottom rung — by a decade or more in some studies.
But basic questions remain: Why does a low-status life undermine health and how is biology involved? Maybe wealthier people take better care of themselves, paying for the best health care or finding safer jobs. Or healthier humans might find it easier to become wealthier and more successful.
Monkeys, however, haven’t evolved health care or what a human would call a job. The animals offer Tung the chance to see more clearly how social hierarchies affect DNA, and thus health.
In one of her more striking papers, Tung and colleagues found that shifting the social rank of female rhesus macaques changes how prone their immune systems are to chronic inflammation (SN: 12/24/16, p. 7). In humans, chronic inflammation appears to be a risk factor for heart disease and other illnesses.
The researchers monitored macaque immune systems and gene activity of captive females living in groups and then shuffled all animals of particular rank into a new cluster so different hierarchies formed. Tung put all the formerly top females into the same group, for instance, so that only one of them would continue to enjoy life as number one.
Overall, a female’s immune status improved or faltered according to whether her social status rose or fell, Tung and colleagues reported in 2016 in Science. Testing to see which genes became more or less active as a monkey’s social fortunes changed has revealed some biochemical pathways that may turn out to explain the physical costs of a sinking status.
For studying social influences on gene regulation, “Jenny is certainly among those at the forefront of technical genetic sophistication,” says Steve Cole of UCLA’s medical school. He studies social impacts on gene regulation in people and has found healthful effects from life satisfaction and worrisome impacts of loneliness. Tung, he says, is the only researcher in the field who has experimentally manipulated monkey social status.
Captive monkeys, however, live relatively plush lives. To see if rank and tough starts in life loom as large in the wild with its extra perils, Tung turned to data from baboons she has visited in Kenya’s Amboseli National Park. Generations of monkeys have been observed there since 1971.
For 196 Amboseli female baboons, Tung and colleagues checked for six forms of hardship early in life, such as a severe drought or the deprivations encountered by a daughter of a low-ranked mom. Baboons that suffered at least three of these disadvantages as youngsters died on average 10 years earlier than those with no more than one misfortune, the researchers reported in 2016 in Nature Communications. Even in the wild, social adversity plays a role in lifelong health.
In upcoming papers, Tung says, her new findings may begin to clarify whether a tough social life, at least among monkeys, causes poor health or is a consequence of it.
“Jenny is not cut from any familiar mold as a scientist,” says Susan Alberts, chair of Duke’s evolutionary anthropology department and one of Tung’s mentors. She calls Tung “inherently interdisciplinary.”
Tung herself remembers being asked as a student whether she saw her future science self at a computer pushing computational boundaries, or standing in the field watching animals, or wearing a white coat at a lab bench. “I didn’t want to give any of those up,” she says.
She traces her thinking back at least to freshman year at Duke, when an interdisciplinary seminar introduced her to an evolutionary framework for considering values such as altruism. The framework “felt sensible … like an empirically driven, scientifically minded way of explaining hard problems in the world,” she says.
Now she’s using that framework to tackle a long-standing social-adversity question that she’s intensely curious about. So what if it’s big and hairy.
N. Snyder-Mackler et al. Social status alters immune regulation and response to infection in macaques. Science. Vol. 354, November 25, 2016, p. 1041. doi: 10.1126/science.aah3580.
J. Tung et al. Cumulative early life adversity predicts longevity in wild baboons. Nature Communications. Published online April 19, 2016. doi:10.1038/ncomms11181.
R. Ehrenberg. Low social status leads to off-kilter immune system. Science News. Vol. 190, December 24, 2016, p. 7.
N. Seppa. Chronic stress can wreak havoc on the body. Science News. Vol. 187, March 7, 2015, p.18.
B. Bower. Baboon bosses get stressed for success. Science News. Vol. 180, August 13, 2011, p.11.