For the past few years, social scientists have been buzzing over a particular topic in molecular biology—gene regulation. The hype has been building steam for some time, but recently, it rocketed to the forefront of public discussion due to a widely circulated piece in the New Yorker. Articles on the topic are almost always fascinating: They often give the impression that this particular area of biology stands poised to solve huge mysteries of human development. While that conclusion may be appropriate in fields like medicine and other related disciplines, a number of enthusiasts have openly speculated about its ability to also explain lingering social ills like poverty, crime, and obesity. The trouble is, this last bit isn’t really a feeling shared by many of the genetics experts.
Social scientists’ excitement surrounds what we can refer to broadly as transgenerational epigenetics. To understand why social scientists have become enamored with it, we must first consider basic genetics. Many metaphors exist for describing and understanding the genome; they all capture the reality that genes provide the information for building and running biological machinery like the human body.
From the moment sperm manages to infiltrate an egg cell, genes (segments of our DNA that ultimately produce proteins) are at work knitting together the necessary components to make life possible. This requires exquisite coordination. Even though every cell in your body (minus red blood cells) carries your complete genetic code, not every gene is “turned on” all at once all over the body. As Mark Ptashne, who holds the Ludwig Chair of Molecular Biology at Memorial Sloan-Kettering Cancer Center in New York, explains:
“Development of an organism from a fertilized egg is driven primarily by the actions of regulatory proteins called transcription factors. In sequential waves and combinations, these proteins bind to specific DNA sequences—called cis- regulatory sequences—associated with specific genes, and encourage (activate) or discourage (repress) transcription into mRNA of those genes (2–4).”
The transcription factors that Ptashne mentions in large part ensure that the genes are expressed appropriately. Uncoordinated simultaneous gene expression would be akin to trying to write this article by hitting every letter (or gene) on the keyboard at once; an indecipherable word (or protein) salad would result. Typing letters in a coordinated sequence, as with coordinated gene expression, allows for meaningful words, sentences, and paragraphs (proteins) to be constructed.
What could this have to do with social science? Consider a landmark study, conducted in 2004 and published in Nature Neuroscience, which practically started the conversation over transgenerational epigenetics. The authors analyzed whether different nurturing styles might influence stress responses in offspring. The findings suggested that different types of nurturing from participant moms impinged on how babies developed by directly tinkering with their gene expression. Let that sink in: Our experiences—such as how our parents treat us—may alter how our genes are expressed, thus impacting our physiological and psychological development. The weightier implication, though, was that these epigenetic “markers” in the genome might also be transmitted to future generations (thus, the “transgenerational” moniker).
That’s right, the most compelling evidence for transgenerational epigenetics is in rodents, not humans.
Many social scientists felt vindicated by the findings, assuming it represented a triumph of the “social” over the “biological.” But the true nature of findings like these should inspire caution. In a new afterword published this year to his tour de force from 2002, The Blank Slate, Harvard psychologist Steven Pinker reminds us why we shouldn’t carelessly fling ourselves on the transgenerational epigenetics bandwagon:
“Also inflating the epigenetics bubble is a set of findings that genuinely are surprising, namely that some epigenetic markers attached to the DNA strand as a result of environmental signals (generally stressors such as starvation or maternal neglect) can be passed from mother to offspring. These intergenerational effects on gene expression are sometimes misunderstood as Lamarckian, but they’re not, because they don’t change the DNA sequence, are reversed after one or two generations, are themselves under the control of the genes, and probably represent a Darwinian adaptation by which organisms prepare their offspring for stressful conditions that persist on the order of a generation. (It’s also possible that they are merely a form of temporary damage.) Moreover, most of the transgenerational epigenetic effects have been demonstrated in rodents, who reproduce every few months; the extrapolations to long-lived humans are in most instances conjectural or based on unreliably small samples. Biologists are starting to express their exasperation with the use of epigenetics as “the currently fashionable response to any question to which you do not know the answer,” as the epidemiologist George Davey Smith (2011) has put it. Other deflations of the epigenetics bubble may be found in Coyne, 2015; Heard & Martienssen, 2014; Juengst, Fishman, McGowan, & Settersten, 2014; Moffitt & Beckley, 2015; and Haig, 2007.”
That’s right, the most compelling evidence for transgenerational epigenetics is in rodents, not humans. We are fans of animal research, but as Pinker noted, the strengths of it (fast reproductive cycles allowing for the study of numerous generations in a short window of time) may also curtail its applicability to humans in this particular case. Additionally, scientists can randomly manipulate a rodent pup’s exposure to different parenting/rearing strategies. But doing this with human babies would never fly with a university ethics committee.
When you can’t do experiments, you have to be very careful about something called confounding. Confounding is a pernicious problem that can make one thing look like it’s causing something else when, in actuality, it’s not. Epigenetics research, like all scientific areas, has to guard closely against confounding. Experiments deal nicely with this problem. Associational studies in humans, though, are much more vulnerable to it.
While working on this article, Pinker reminded us of another key point. When social scientists say “environment” they mean something very different than when biologists say “environment.” To a geneticist, environment is anything that isn’t DNA (in essence, the cellular environment of DNA). To a social scientist, though, the environment captures everything from the way your parents raised you to the international political climate. The cellular environment might be relevant for understanding environmental regulation of gene expression, but this does not necessarily mean that social environments (like neighborhoods) have a similar impact. More time and research is needed to unpack the latter possibility.
“Many of our expert epigenetics research colleagues are deeply embarrassed by the warm, uncritical response their work has attracted from the social sciences,” say Terrie Moffitt, a distinguished clinical psychologist at Duke University, and Amber Beckley, a criminologist also at Duke. “A biologist attendee at a July 2014 Washington, DC workshop on the social and behavioral implications of epigenetics gasped, ‘The biologists there were horrified at the thought . . . we really don’t understand the basic biology well enough yet to do this!’” (For additional epigenetics caution from other experts, see here).
We’ve witnessed the incursion of epigenetic-hype into our own field of criminology and criminal justice. Recently, we debated scholars in the top criminology journal who argued we should scrap basic behavioral genetics research in no small part because epigenetics was forcing us to “rethink biology” and how genes influence behavior. Reflecting on our debate, we found it ironic that criminology—a field that up until now had been reluctant to discuss genetic influences on behavior—had inexplicably experienced a metamorphosis. Now, epigenetics represented the clear path forward.
On closer inspection, of course, the genesis of this newfound enthusiasm was no mystery. As we mentioned, it resides in the hope that epigenetics heralds the victory of “environmental” over “biological/genetic.” Don’t forget, though, that epigenetics is not a way to hurdle over basic evolutionary principles. Nor does it allow one the luxury of ignoring the rich insights of quantitative genetics and inheritance research. These studies have shown that genetic influences on human outcomes are ubiquitous. Nothing we may learn about transgenerational epigenetics will change that.
Brian Boutwell is an associate professor of criminology and criminal justice at St. Louis University where he is also appointed in the Department of Epidemiology.
J.C. Barnes is an associate professor in the School of Criminal Justice at the University of Cincinnati.