As I’ve been mentioning for years, we live in an age of growing antiquarianism in terms of thinking about cause and effect of social outcomes. When I was young, there was much interest in how things had changed from the 1960s onward. The Sixties were seen as a big deal.
But now, leading historical savants like Ta-Nehisi Coates act as if they have been living in an underground fallout shelter since 1959. They’ve never heard of the Sixties. What possible influence could the last 50 years have on the present? If you want to understand the Obama Era you need to obsess over New Deal redlining.
The enthusiasm for epigenetics — i.e., a Lamarckian/Lysenkoist theory that the past, especially politically exploitable traumas such as the Holocaust or slavery, can damage genes for multiple generations — is related to this antiquarian turn.
For example, The Guardian reported in 2015:
Trauma research about the impact of the Holocaust on subsequent generations varies; some studies conclude there is no effect of trauma two generations on, while others claim that breast milk of survivors was affected by stress hormones that impacted on the physiology of the next generation. Some in the field of epigenetics say the intergenerational effects of the Holocaust are very pronounced and that the atrocities altered the DNA of victims’ descendants, so that they have different stress hormone profiles to their peers. …
This kind of thing doesn’t mean that epigenetic effects never ever happen. For all I know, they could happen now and then.
But there’s a lot of confusion about the implication of the theory of epigenetics.
A. Strong Form of Epigenetics: Sometimes it’s discussed as if it’s a Lamarckian way that impacts future generations that haven’t been conceived yet via genetic means.
B. Weak Form of Epigentics: But other times, epigenetics is discussed as if it’s a way that people who are already conceived have their Nature impacted by their Nurture. This latter approach is mildly interesting but not terribly revolutionary. It’s nice to know more detailed ways that Nurture can have its effect, but it’s not exactly validating Lamarckism.
For example, in the NYT article below, two studies on the possible epigenetic impact of wartime starvation are cited. The first, about the children of Civil War POWs, cites detriments suffered by the not-yet-conceived children of the victims: if true and representative, that would be the more interesting Strong Form.
The second study cited, about people who were fetuses during the Dutch famine of 1944-45, cites detriments suffered by already conceived victims. That’s the technical Weak Form.
I’d also suggest that there might be a Medium Form of epigenetic theory: unlike in classical Lamarckism, in which a giraffe who stretches his neck to reach leaves higher up on a tree will conceive longer-necked offspring, in the Medium Form of epigenetic theory, Nurture can mostly just do damage to Nature. If you suffer a famine, the children you conceive later might have some genetic problems due to the long-lasting physical effects of your trauma. That would be kind of interesting but not remarkable: it’s easier to break things than build them. (Darwin’s theory of natural selection made the leap that every so often a breakage turns out to be useful.)
From the New York Times Science section, which often tries to push back gently against popular delusions:
Headlines suggest that the epigenetic marks of trauma can be passed from one generation to the next. But the evidence, at least in humans, is circumstantial at best.
By Benedict Carey, Dec. 10, 2018
In mid-October, researchers in California published a study of Civil War prisoners that came to a remarkable conclusion. Male children of abused war prisoners were about 10 percent more likely to die than their peers were in any given year after middle age, the study reported.
The findings, the authors concluded, supported an “epigenetic explanation.” The idea is that trauma can leave a chemical mark on a person’s genes, which then is passed down to subsequent generations. The mark doesn’t directly damage the gene; there’s no mutation. Instead it alters the mechanism by which the gene is converted into functioning proteins, or expressed. The alteration isn’t genetic. It’s epigenetic.
The field of epigenetics gained momentum about a decade ago, when scientists reported that children who were exposed in the womb to the Dutch Hunger Winter, a period of famine toward the end of World War II, carried a particular chemical mark, or epigenetic signature, on one of their genes. The researchers later linked that finding to differences in the children’s health later in life, including higher-than-average body mass.
Here’s Carl Zimmer’s article on the epigenetic effects of the Dutch Hunger Winter. But I don’t understand the argument that the effects of starvation on already conceived individuals in the womb is evidence for epigenetic transmission across generations, thus destabilizing our model of Nature and Nurture. Famine when you were in utero is, obviously, a failure of Nurture (in the guise of not enough nutrients and other gestational problems).
If epigenetic effects are real, they should be evident in children conceived after the Dutch Hunger Winter, not in children conceived before.
I’d be more impressed by the epigenetic explanation if they proved that the children and, ideally, the grandchildren of those who were fetuses during the Dutch Hunger Winter suffered mysterious detriments. This Dutch Hunger example seems to be quite different from the Civil War POW example, which focused on the children conceived after (I hope) the Civil War.
But even the Civil War example could have a straightforward Nurture explanation: guys who suffered badly in POW camps and then returned to typical farm jobs might have on average suffered more long-lasting ill health due to their mistreatment and thus grew less food on average than guys who came through the Civil War okay, which in turn meant their kids had less food on average growing up than is ideal, which is bad for you.
Another issue, of course, is possible publication bias:
– Let’s look at the children of abused Civil War POWs. Bingo! Publish!
– Let’s look at the children of, say, abused Bataan Death March POWs. Uh, oh, no effect … Let’s leave that one in the bottom of the file cabinet …
The excitement since then has only intensified, generating more studies — of the descendants of Holocaust survivors, of victims of poverty — that hint at the heritability of trauma. If these studies hold up, they would suggest that we inherit some trace of our parents’ and even grandparents’ experience, particularly their suffering, which in turn modifies our own day-to-day health — and perhaps our children’s, too.
But behind the scenes, the work has touched off a bitter dispute among researchers that could stunt the enterprise in its infancy. Critics contend that the biology implied by such studies simply is not plausible. Epigenetics researchers counter that their evidence is solid, even if the biology is not worked out.
“These are, in fact, extraordinary claims, and they are being advanced on less than ordinary evidence,” said Kevin Mitchell, an associate professor of genetics and neurology at Trinity College, Dublin. “This is a malady in modern science: the more extraordinary and sensational and apparently revolutionary the claim, the lower the bar for the evidence on which it is based, when the opposite should be true.”