"There are conditions and serious diseases occurring in the population today at a rate that simply cannot be explained by the rules of mammalian genetics alone," says Michael K. Skinner, a professor at Washington State University and the founding director of the Center for Reproductive Biology in the School of Biological Sciences.
In other words, the rate at which children in some demographic groups are born too soon, the fact that entire geographic regions suffer from elevated rates of obesity and diabetes, and even the frequency with which American children today are diagnosed with autism cannot be sufficiently explained by the Punnett Squares every high school biology student must master, Skinner says.
"Genetics is part of the story, an important part of the human story," says Skinner. "But epigenetics, that is the other half of the equation."
The Effects of Chronic Stress
An Emory University study released last year suggested just how large epigenetics may loom in one of the country's most egregious racial and ethnic health disparities — premature births. The United States' premature birth problem is the worst in the industrialized world, especially for racial and ethnic minorities. About 10.5 percent of white children were born before 37 weeks gestation in 2012, along with 10.3 percent of Asian babies. But about 11.7 percent of Latino children, 13.6 percent of Native American babies, and 16.8 percent of black infants arrived too soon.
Elizabeth Corwin, dean of research at Emory University's Woodruff School of Nursing, and a team of researchers closely tracked more than 100 women during the last three months of their pregnancies. They found that women of all races and ethnicities who were poor during their pregnancies were more likely to suffer from chronic stress, a biologically detectable and quantifiable condition. The same was also true, says Corwin, of middle-class black women, and all Latinas except for those who were immigrants. In fact, the problem was particularly pronounced in those last two groups.
Black women and Latinas across socioeconomic categories — those with and without insurance, college degrees, and access to the best food and information — were significantly more likely to test positive for elevated levels of stress hormones and conditions that those hormones can set in motion. This made the women more likely to deliver their children early. Chronic stress, the team determined, is the reason approximately 30,000 more African-American babies are born prematurely each year than any other group.
"We all experience stress," Corwin says. "Some weeks, who doesn't feel utterly overwhelmed? But what we found was that chronic stress is something entirely different. It [is] created by some combination of finances, relationships, community, and experiences like racism — actual and perceived."