In an episode of Dear White People that Mashable declared required viewing for “every ally,” the show’s Black protagonist, Sam, engages in a heated argument with her white ex, Gabe, about his hamfisted attempt to highlight racial injustice by making a documentary called Am I Racist?. The argument reaches a crescendo when Gabe tells Sam she needs to be more vulnerable about her experience of racism, and Sam fires back by describing her trauma, which she says isn’t just psychological, but bodily:
SAM: Have you heard of epigenetics?
GABE: No… Are you gonna tell me what it is?
SAM: Yup. Joelle was talking about it the other day. Shit, what was she saying? Oh right, it’s the inheritance of pain. Basically, scientists have figured out that people who experience intense trauma, like slavery, pass that down through their DNA, so pain and suffering is literally in my blood.
GABE: How do you spell that?
GABE: I’m Googling it.
SAM: You don’t need to Google it. I just told you what it is.
These few minutes of dialogue illustrate a popular lay understanding of the science of epigenetics and trauma, specifically the idea that highly stressful events can cause changes to a person’s biology that they pass down to their children and grandchildren. Journalist James Greig recently argued that trauma is the “dominant frame for thinking about unhappiness,” and British epidemiologist George Davey Smith has called epigenetics “the currently fashionable response to any question to which you do not know the answer.” So naturally, transgenerational epigenetic inheritance of trauma has become a trendy idea, especially at the intersection of social justice and wellness circles.
Public interest in epigenetics has grown steadily since the mid-2000s, when the news media began reporting on influential studies in the field with tantalizing headlines like, “A PAINFUL LEGACY: Parents’ Emotional Trauma May Change Their Children’s Biology” and “Study of Holocaust Survivors Finds Trauma Passed on to Children’s Genes.” But the field is in its infancy, and there’s an enormous amount scientists don’t know, which is why journalists usually temper the bold claims in headlines with words of caution from experts. Neuroscientist Johannes Bohacek of ETH Zurich told Science that “the jury is still out on humans” (many of the studies in this field are conducted on mice), and Columbia University biologist Katherine Crocker warned that “there’s a lot of overinterpretation of initial results.”
However, these words of caution haven’t prevented runaway interpretations of the science from proliferating on social media, where you’ll routinely encounter claims that “trauma changes your DNA” and that you can “genetically inherit your parents’ pain.” “Today, thanks to lots of research and studies, we know that what [our ancestors] went through affected them so greatly it altered their DNA at a biological level,” reads a characteristic example on Twitter with more than 47,000 likes. “In other words, your ancestors needed therapy so badly that you need therapy as a result of sharing that traumatized DNA.”
But the idea that people with stressed ancestors inherit “traumatized DNA” is an enormous leap from the modest conclusions in the scientific literature, which are themselves controversial. Oliver Rando of the University of Massachusetts Medical School, who uses mice to study intergenerational information transfer, thinks it’s “quite clear” from the research that “your ancestors’ experience can affect some traits in future generations,” and Tracy Bale, Professor of Pharmacology at the University of Maryland School of Medicine and Director of the Center for Epigenetic Research in Child Health and Brain Development, says there’s “every reason to believe, in both humans and animals, that parental experiences across the lifespan can impart meaningful biological effects on their offspring.”
Some scientists don’t accept these conclusions (more on that later), but even among those who do, big, unanswered questions remain: What kind of information does an ancestor pass to their descendants? How does this all happen? And what are the ultimate effects in humans?
What kind of information a stressed ancestor passes to their descendants is a “million-dollar question,” Rando says. He favors the view that ancestors pass on “low-bandwidth” or “coarse-grained” information — some general sense of how stressful the world is, essentially. He thinks it’s “unlikely” that ancestors pass on complex or “high-bandwidth” information like specific information about the nature of the trauma. “Certainly a lot of skepticism in the field centers around the fact that none of us have figured out how these systems work,” Rando says, and Bale agrees that “the controversy is in the biology.” “You could get changes in someone’s immune system because dad’s traumatic experience imparted some signal when sperm met egg,” she explains. “We don’t really know what that signal might be, but it could be an important signal that tells the egg something.”
For example, this signal might speed up or slow down embryonic development, and if development is sped up, “you may miss out on some of the fine-tuning processes that are important, for instance in the brain,” she continues. “You’re still going to get a baby with 10 fingers and 10 toes, but you might not recognize that the synapses in their brain make that child a little bit more sensitive to their environment or a little less sensitive to their environment.” Bale clarifies that, in humans, this is a complete hypothetical: “Do we know [the end result] in humans? God, no. We’re far away from being able to determine that.”
But perhaps all these questions about mechanisms and effects are premature, and we need to back up to an even more fundamental question: Does transgenerational epigenetic inheritance even occur in humans? Kevin Mitchell, Associate Professor of Genetics and Neuroscience at Trinity College, Dublin, is highly doubtful. “I find that literature completely unconvincing,” he says. “I’ve looked through many of these papers to try to see if there’s anything there, any good evidence for it at all, and there isn’t.”
Mitchell describes these papers as “awful” and says they’re “poster children for questionable research practices.” He’s detailed their methodological and theoretical problems on his blog, Wiring the Brain, in accessible terms (see, for example, his posts here and here). He hasn’t cherry-picked especially bad papers, either, adding that he’s “looked at the most cited papers in the field” in both mice and humans.
One significant problem, he says, is that researchers embark without a specific hypothesis and instead “dredge for statistical significance” by conducting multiple tests, reporting on any difference between groups without correcting for this multiple testing. “It’s basically like, ‘We think something might be happening, let’s take a look. Did we get a hit? Good, we’ll publish the hits. Did we get a miss? Into the bin,’” he explains. “It really undermines the credibility of the field as a whole.”
Mitchell isn’t a lone skeptic, either. John Greally, Director of the Center for Epigenomics at the Albert Einstein College of Medicine in New York City, has called transgenerational epigenetic inheritance in humans an “attractive but poorly-founded idea” and criticized studies in the field for being “uninterpretable.” “I’d like to see us be more bold and brave and move from preliminary association studies to definitive studies,” he told Science, “and be open to the idea that there may be nothing there.”
That’s the exact conclusion Mitchell has reached. “When you look into the data, there’s nothing there at all,” he says. “Some critics look at the published data and argue that the effects aren’t so large or long-lasting as to be really meaningful. I’d go further and say there are no real effects there to discuss at all. I don’t see any convincing evidence that transgenerational epigenetic inheritance occurs in mammals, especially not in humans.”
You can begin to see the myriad problems, then, with claims on social media that humans can inherit “pain” or a “need for therapy” from their ancestors. “It’s pretty clear that epigenetics aren’t the dominant contributor to diseases like diabetes or to things like anxiety or depression,” Rando says. “People shouldn’t feel doomed by the fact that their parents came out of civil wars.” These interpretations also jump to the conclusion that inherited effects will be negative. “One assumption people seem to make when extrapolating from mouse studies is that, if your human ancestors were stressed, you’ll have a baseline of stress and anxiety,” Rando says. “But it may be the case that if your ancestors were stressed, you’re more likely to be resilient.”
On social media, you not only encounter claims that descendants inherit thoughts, memories and pain from their ancestors, but “epigenetics” is also seized on to explain phenomena as complex as personality disorders, bigoted attitudes and targeted violence. “If we can inherit trauma from our ancestors, it also stands to reason that white people can inherit sociopathy and a tendency towards violence against others,” read one tweet that racked up more than 15,000 likes before it was deleted; another user came to Nick Cannon’s defense by saying “epigenetics dictates that trauma can be passed down through generations; therefore, it is not far-fetched that oppressive behavior can also be passed down through generations of white families.” (Cannon had recently been fired for calling Jews and white people “savages” with a “deficiency” that causes them to be violent.)
The idea that “epigenetics” means you could inherit something as complex as sociopathy or a belief in white supremacy “doesn’t really track,” Rando says, and Bale says the logic here is a “big leap.” Mitchell dismisses these interpretations much more strongly: “It’s just so simplistic and naive and so reductionist, the idea that incredibly complex socio-historical phenomena can be reduced to a few chemical marks on our DNA,” he says, adding that whether a group of people become colonized or colonizers, slaves or slave owners, depends on a historical “accumulation of accidents,” not biology. “They’re just different trajectories that different cultures went down, where it’s the cumulative cultural history that’s important,” he continues. “There’s no indication that there’s underlying biological differences between those sets of people that set them down those trajectories.”
These interpretations aren’t just wrong, he says, but trivializing: “There are really long-lasting socio-cultural effects of those historical trajectories — of whether you were colonized or not — and to me it trivializes it to reach for reductive biological explanations, for which there is no evidence.”
Why, then, have people seized on “epigenetics” to explain everything from their own neuroses to white supremacy?
There are all sorts of answers to this question, many of which Mitchell discusses on his blog, but the public has certainly had some encouragement from “experts.” For example, in 2015, Deepak Chopra and Rudolph E. Tanzi, a doctor of medicine and Professor of Neurology respectively, published a book with the central claim that “you are the user and controller of your genes, the author of your biological story.” By 2017, Mark Wolynn, “a leading expert on inherited family trauma,” was confidently claiming that “the latest epigenetic research tells us […] we biologically inherit fears, anxieties and obsessive thoughts from our parents and grandparents.” It’s easy to see how someone might be persuaded by these ideas, especially if they’re also reading headline after headline in publications like ABC Science and Discover Magazine that suggest epigenetics really does herald a new scientific paradigm.
These ideas can also have a strong emotional resonance: As anyone at the end of a long line of traumatized people knows, the resulting problems can seem so deep and intractable it’s like they really do live in your bones and blood. And of course, the effects of trauma and abuse do ripple out through the ages, and breaking the cycle is no small task. Virtually no one disagrees about this.
But we don’t need to appeal to epigenetics to make this point. “There’s tons of evidence that trauma in one generation can affect the next generation, but just through psychological mechanisms,” Mitchell says. “There’s no need to invoke these really complicated molecular mechanisms. It just doesn’t add anything to the story, and there’s no real evidence for it.”
“The intergenerational effects of trauma are very real,” Bale concurs, “but there’s no magical memory of it in our DNA.”