Last winter, while reporting a feature for this magazine, I was sitting in the Stanford office of Atul Butte, a pediatrician-slash-computer-scientist-slash-wunderkind, and he was touting the promise of the personal genetics revolution. Health care is on the brink of being totally transformed by the insights given to medicine by being able to see, and increasingly understand, the human genome, including new insights about how the genes that cause disease do (or don’t) get expressed. As he talked, one very particular question struck me like lightening and has stuck with me ever since. The medical establishment has long regarded the family-history questionnaire — the endless checklist you fill out at the doctor’s office — as a Rosetta Stone for an individual’s predisposition to disease. But given everything that science is learning about how gene mutations correspond to disease and everything that public health officials now know about how lifestyle and environment, especially diet and exercise, correlate to good health, and everything researchers are gleaning about how genes and the environment interact, just how useful is that ancestral information anyway?
Let’s consider the negative case first. You may share certain genetic predispositions for disease with your grandmother, but it’s not intuitively clear that the health of that grandmother should be a reliable guide to your future health: Genes are activated by complex, environmental factors and your grandmother lived in an entirely different world from yours — without the Cheesecake Factory and a Burger King at every rest stop, yes, but also without FitBits and Spin classes and a kale smoothie on every menu. Back then, people smoked — and I mean smoked. Like, several packs a day of unfiltered cigarettes smoked, inside and with the windows closed. (Even if your grandmother didn’t, she was probably surrounded all day by people who did.) And unless your ancestors were Greek fisherpeople, you are basically sure to have had ancestors who, for at least a couple of generations, indulged in their fair share of such American pleasures as the two-martini lunch, the all-you-can-eat buffet, and cheese fries. People so desperately want meaningful health prognostications that they look to the past to tell the future, but “your grandmother was eating steak every night back then,” Butte told me. If someone did that today, and died from a heart attack at 65, no one would be looking at heredity for a cause. Given all that, how much bearing does it have on your own future health, really, to know whether your grandma died of diabetes or lung disease?
It’s a convincing argument. And besides, Butte added in a later email, it’s not clear how well people remember or understand the diseases of their forebears. It can be impossible to tease truth out of disease data recollected in the present by patients with unreliable memories about people who died or were sick in the past, at a time when medicine was considerably more crude. “I certainly speculate,” Buttewrote, “that family histories don’t make much sense given how little diseases were diagnosed or properly labeled back then.”
How do we know what grandma actually died of? It wasn’t so long ago that epilepsy was called “falling sickness” and tuberculosis “consumption,” but how many of us remember — or are even aware of — the meanings of those synonyms when answering questionnaires in the doctor’s office? And then there is the fact that politeness kept certain families from ever knowing for sure what made loved ones sick. On my mother’s side, a great-grandmother died on the operating table from what in my family was euphemistically referred to as “female trouble” — which may mean I have inherited a predisposition for cervical cancer, uterine cancer, or ovarian cancer. Or it may mean she died during a botched abortion, in which case I’m all good in the hereditary female trouble zones, but aghast at the other narrative questions that arise.
Because of how patchy family histories can be, and because they are so pressed for time, and because there’s no consensus on what comprises a family medical history anyway, only 63 percent of family doctors take a family history on three quarters of their patients, according to a study published a decade ago in The Journal of General Internal Medicine. When these doctors do ask about family health conditions, they devote three minutes on average to the chore on a first-time visit and two minutes subsequently. The evidence was building: It seemed to me more and more obvious that family histories would soon become a relic of medicine’s past, like leeches — or blood-letting.
But of course there is positive case for family histories, too. Armed with my hypothesis that dramatically changed environments and personal habits make them obsolete, I started shopping it around. First stop was my own brother, a pulmonologist at a hospital in Cambridge, Massachusetts, and an expert in critical care. I am a humanities geek, and with the brashness of the neophyte, I tossed my question at him. “Family histories,” I posed. “Useless and out of date?”
My brother, usually an even-tempered type, practically reached out and throttled me through Gmail. Family history is crucial, he wrote, for diagnostic and screening purposes. “Does this patient who is short of breath have asthma? If they meet some criteria for asthma but not others, but their mother, brothers, and grandfather have asthma, then the diagnosis is more likely to be asthma in their case.” Doctors know to screen a 40-year-old for colon cancer if they know that patient’s parent or grandparent developed colon cancer at a young age and they know to test for diabetes if diabetes runs in the family. For my brother, a practicing physian who actually sees really sick people every day, a family history is a useful, if not entirely foolproof or definitive, piece of information that contributes to his decision on what to do next.
Certain scientists go even further. Joe Nadeau is a geneticist who runs a lab at the Pacific Northwest Diabetes Research Institute. The explosion of scientific knowledge about the genetic workings of disease actually argues for more attention to family medical history, not less, because “What happens in your family is an approximation of what happens to you,” he told me. “The conventional family history is still the best predictor of disease risk.” But it’s the reason Nadeau believes this that’s most interesting: not that he thinks environmental factors are trivial, but that they have become actually baked into our genes.
Why does Nadeau believe this? Because his subspecialty is epigenetics, the investigation of how (and under what circumstances) the environment and our experiences — diet, nutrition, famine, trauma, exercise, love, stress, exposure to toxins, pollution, poverty — activate or suppress the genes that trigger disease. And one of the most mind-blowing discoveries in epigenetics over the past ten years has been this one: Humans don’t inherit only their genes from their ancestors. They also inherit the residual effects of some of their grandparents’ life experiences on those genes. If your grandfather lived through a childhood trauma or did a lot of drugs or experienced starvation or had a parent with depression, those events likely made marks on his genes that may have been passed along to you — and not just superficially in the way your father was raised and nurtured and the way he raised and nurtured you, but at the level of your cells, making you biologically more or less vulnerable to cardiovascular disease, obesity, addiction, or depression. “Inherited molecules other than DNA,” reads Nadeau’s website, contribute to “phenotypic variation and disease risk.”
Evolution holds that species change slowly, over thousands of years, thanks to random genetic mutations that occur, eventually, across populations if they’re advantageous to the species itself. Our genes, therefore, are more or less stable; my DNA connects me, indisputably, to my Ashkenazi relatives a thousand years ago and it contains some information about my vulnerability to disease, based on gene mutations I have inherited down the line. But genes can also be “marked” by the various proteins they’re wrapped in or bundled with — scientists talk about these proteins having the ability to turn genes “on” or “off” — in reaction to the environment around them. (The classic example here is this: When one identical twin has schizophrenia, the other twin will have it just 50 percent of the time. Twins may have the exact same DNA, but their environments differ, switching on the disease just half the time.) Now a growing body of research indicates that the “markers” are sometimes hereditary, too. (The questions of when, why, and in what circumstances represent the frontier of epigenetics.)
A man who lived through a famine as a prepubescent boy may have children and grandchildren who are less likely than other people to die of cardiovascular disease and stroke. A man who suffered child abuse may be likelier to have a son who commits suicide. A male rat exposed to a powerful toxin has generations of male children with low fertility, even though those children were not exposed to the toxin themselves. A female rat who is not nurturing has children with an overactive anxiety response. And these are not just “nurture” effects, the result of a particular parenting style. In rats and plants (and in suicide victims), scientists have looked at the cells of the study subjects and found their gene markers to be stuck in the “on” position.
All of which suggests that the conventional family medical history is not only relevant, it probably doesn’t go far enough. Your own health may rest on knowing whether your grandfather worked in a coal mine or survived the Holocaust, whether your grandmother was an only child or one of 12, whether your mother picked fruit or lived near a Superfund site. Even as you rigorously adhere to a Paleo regimen, your body may still think you’re starving or smoking or eating your grandmother’s pork-and-dumplings diet. “Maybe the old saw of ‘we are what we eat’ doesn’t go far enough,” writes Nessa Carey in her 2012 book The Epigenetics Revolution. “Maybe we’re also what our parents ate and what their parents ate before them.”
If you’re even a casual kind of health nut or fitness freak, you probably believe that you can defy your genetic destiny — that your devotion to a Paleo diet and a Spinning regimen is going to save you not just from your grandfather’s wheeze and his potbelly but also his fatal heart attack. But on the question of just how much of your health is in your own hands, and how much you’re actually trapped not only by your grandpa’s genes, but also by his unhealthy personal habits, you probably have less control than you think.