About two weeks ago, the BBC’s “Future” website published a long science article touting the importance of epigenetic effects in humans: the idea that various behaviors, traumas, and psychological propensities produced by the environment on parents can be transmitted to their offspring. This is supposed to act in a “Lamarckian” way: the environment modifies the parents’ DNA or proteins by putting chemical markers on them, these modifications get passed on without any change in the genetic code. In other words, it’s the inheritance of an acquired character, something that is generally ruled out by the way genes work.
Click on the screenshot below to see the BBC’s breathless take:
The article gives several reports of the kind of stuff that’s inherited: health problems passed on to the sons of Civil War prisoners (but not their daughters), changes in the stress hormones in the offspring of Holocaust survivors, increase in the mortality of the grandsons of Swedish males who survived a famine and, in mice, increased sensitivity to a chemical odor in offspring and grand-offspring of mice who had learned to fear that odor by getting a shock when they smelled it. The BBC then touts all this as having big implications for humans:
But if these epigenetic changes acquired during life can indeed also be passed on to later generations, the implications would be huge. Your experiences during your lifetime – particularly traumatic ones – would have a very real impact on your family for generations to come. There are a growing number of studies that support the idea that the effects of trauma can reverberate down the generations through epigenetics.
. . .if humans inherit trauma in similar ways, the effect on our DNA could be undone using techniques like cognitive behavioural therapy.
“There’s a malleability to the system,” says Dias [Brian Dias, the author of the mouse study]. “The die is not cast. For the most part, we are not messed up as a human race, even though trauma abounds in our environment.”
At least in some cases, Dias says, healing the effects of trauma in our lifetimes can put a stop to it echoing further down the generations.
Well, we want to heal the effects of trauma in our lifetimes because trauma is painful, and none of these studies show any way to stop the supposed inheritance of trauma save by not exposing parents to trauma in the first place. In other words, the clinical implications of all this work is negligible.
But, as I’ve emphasized repeatedly, studies showing the “legacy of trauma” are more often than not flawed, relying on p-hacking, small sample sizes, and choosing covariates, like sex, until you get one that shows a significant effect. Further, there is no evidence for the inheritance of epigenetic effects in any organism beyond two or three generations, for epigenetic markers get reset, being wiped out during sperm and egg formation.
Finally, almost every study cited by the BBC report—save the Civil War study, which is too new to garner general acceptance— has been subject to criticism, criticism barely mentioned by the BBC. The mouse odor study by Dias and Ressler, for instance, was criticized in Genetics by Gregory Francis, who said that Dias and Ressler’s work was too successful:
The claim that olfactory conditioning could epigenetically transfer to offspring is based on successful findings from both the behavioral and neuroanatomical studies. If that claim was correct, if the effects were accurately estimated by the reported experiments, and if the experiments were run properly and reported fully, then the probability of every test in a set of experiments like these being successful is the product of all the probabilities in Table 1, which is 0.004. The estimated reproducibility of the reported results is so low that we should doubt the validity of the conclusions derived from the reported experiments.
Why was it “too successful”? Francis gives a number of reasons, which include unconscious manipulation of the data, poorly designed studies, and unreported experiments. Regardless, the mouse odorant experiments—and remember, even the effects reported lasted just two generations—should only be mentioned if you include Francis’s caveat. The BBC somehow overlooked that.
In humans, both the Swedish and Dutch famine studies, and the pitifully small sample in the Holocaust study (whose results have largely been disowned by the authors themselves) have been analyzed on a useful post by Kevin Mitchell, a neurogeneticist in Dublin, who rejects all the conclusions and winds up, after reviewing the corpus of highly touted human studies published through May of last year:
In my opinion, there is no convincing evidence showing transgenerational epigenetic inheritance in humans. But – for all the sociological reasons listed above – I don’t expect we’ll stop hearing about it any time soon.
Mitchell also has a useful take on why, given the methodological and statistical issues with the human “epigenetic” findings, they’re still accepted by journals and beloved by the media. The BBC is just one of many examples of the latter; Mitchell cites several breathlessly uncritical articles in the media about epigenetic inheritance in humans.
I’ll reproduce Mitchell’s analysis below about the misguided public love of epigenetic inheritance in humans, but bookmark his article if you want a useful guide to skepticism about such studies:
So, if these data are so terrible, why do these studies get published and cited in the scientific literature and hyped so much in the popular press? There are a few factors at work, which also apply in many other fields:
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- The sociology of peer review. By definition, peer review is done by experts in “the field”. If you are an editor handling a paper on transgenerational epigenetic inheritance in humans (or animals), you’re likely to turn to someone else who has published on the topic to review it. But in this case all the experts in the field are committed to the idea that transgenerational epigenetic inheritance in mammals is a real thing, and are therefore unlikely to question the underlying premise in the process of their review. [To be fair, a similar situation pertains in most fields].
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- Citation practices. Most people citing these studies have probably not read the primary papers or looked in detail at the data. They either just cite the headline claim or they recite someone else’s citation, and then others recite that citation, and so on. It shouldn’t be that way, but it is – people are lazy and trust that someone else has done the work to check whether the paper really shows what it claims to show. And that is how weak claims based on spurious findings somehow become established “facts”. Data become lore.
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- The media love a sexy story. There’s no doubt that epigenetics is exciting. It challenges “dogma”, it’s got mavericks who buck the scientific establishment, it changes EVERYTHING about what we thought we knew about X, Y and Z, it’s even got your grandmother for goodness sake. This all makes great copy, even if it’s based on shaky science.
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- Public appetite. The idea of epigenetic effects resonates strongly among many members of the general public. This is not just because it makes cute stories or is scientifically unexpected. I think it’s because it offers an escape from the spectre of genetic determinism – a spectre that has grown in power as we find more and more “genes for” more and more traits and disorders. Epigenetics seems to reassure (as the headline in TIME magazine put it) that DNA is not your destiny. That you – through the choices you make – can influence your own traits, and even influence those of your children and grandchildren. This is why people like Deepak Chopra have latched onto it, as part of an overall, spiritual idea of self-realisation.
That’s a good and thoughtful analysis.
So caveat lector, and, BBC, you really were derelict in publishing that article. You misled the public about the findings of these studies, as well as about their implications for clinical psychology.
I’ve put a test below where you can analyze what seems to be an error made by the BBC in its analysis.
h/t: Amy
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A TEST FOR READERS
The BBC, in referring to the Civil War trauma that had effects on the offspring of prisoners, rules out one form of cultural transmission by saying this:
But what if this increased risk of death was due to a legacy of the father’s trauma that had nothing to do with DNA? What if traumatised fathers were more likely to abuse their children, leading to long-term health consequences, and sons bore the brunt of it more than daughters?
Once again, comparing the health of children within families helped rule this out. Children born to men before they became PoWs didn’t have a spike in mortality. But the sons of the same men after their PoW camp experience did.
As I interpret this (and I haven’t seen the study), the comparison doesn’t rule out the abuse hypothesis at all. Why not?
Because the traumatic experience of being a POW could have led to abuse that otherwise might not have occurred.
agreed.
PTSD could cause the spike in mortality.
Absence of a father (during captivity) could also.
Etc etc.
Seems the younger children — those born to the men after their POW experience — might also have been exposed to abuse from a younger age and for a more extended time period.
Did they exclude younger children possibly conceived while daddy was a POW? Such children could then be subject to greater abuse, by a rather disgruntled “father”.
I think I’m getting it. I’m not sure how your^^^ comment prompted it.
The POW father would have returned home, the mother would have given birth to children *in addition to the pre-war children*, and *all* children would have potentially been subject to abuse.
Alternatively, pre-war children might have moved out before the father returned.
The excerpt is, in my reading, almost meaningless, but this underlying logical thread is interesting… if that’s what we are supposed to evince from it. So I’m very curious as to what the solution to this, as I see it, logic puzzle, is.
sub
“Epigenetics” or, as we used to call it “adaptations”. Gee. Organisms have genetically inherited mechanisms that allow them to callibrate to particular circumstances (such as cues to feast/famine or socially trustworthy/untrustworthy environments).
Who knew? Well, all of us knew.
What’s interesting to me is that these folk think that something radcial is at stake here, which immediately raises the question of “what the hell was the picture of what they thought was going on before?”
As a non scientist I’m probably out of my depth commenting on this, but I’ll wade in anyway.
I was looking at the Wikipedia article on alleles a while ago and I noticed a section called “epialleles” or some such. No idea what it was about, but I imagine it’s involved with the epigenetics fad. Is this going to be a new craze- attaching the ‘epi’ prefix to everything to make it seems novel and revolutionary? What next, epichromosomes, epinucleotides, epi-DNA?
I fear you are right.
There are ‘epichromosomes’, only they are not called that (thank goodness)! Their are tiny circular chromosomes inside of mitochondria, separate from the regular chromosomes in the nucleus.
Ah! Hoisted! Well, this is why I put the non-scientist disclaimer at the start! Most interesting fact though.
Ugh. Now we are going to be hearing about this as the genetic justification for the harm suffered by people who are descended from people who were traumatized. Of course, there is still no objective standard to rank trauma. Is being having an ancestor who was a slave more traumatic than having one that was a serf?
Children born after the POW experience would be younger and more vulnerable to POW-experience-induced problems with their fathers. Fathers before POW experience would also have bonded with their children, but were less likely, because less capable of doing so after trauma. I thought of these in 2 minutes, I’m sure further thought would kick out more situations with a purely behavioural or experiential cause.
I agree.
Isn’t that contradictory — if one can influence the traits of one’s children and grandchildren through one’s own choices, doesn’t that itself inherently place limits on their ability to influence their own traits through their own “choices” (even assuming such “choice” exists in the first place)?
Maybe this is a silly or naive thought – but, as a whole, are we experiencing more trauma as a species than in the past? My inclination is to think we are not. In which case, if the impacts are so long-lasting, our current state as a species has been defined by our past traumas… So, is that necessarily a bad thing, from an evolutionary perspective?
Good post. Would like to hear more about research in this field. I have read reposts re animals fest or lack of fear of humans because of contact or lack of contact of ancestors tepbor three generations back. Sounds hard to believe. Glad someone is calling the theory into question and taking a close look at the studies.
tepbor – two or three or more generations back
If all the reports of transgenerational ‘inheritance’ of epigenetic modifications were accepted at face value, do they show that the effects are adaptive? If one if descended from the survivors of a famine in Sweden, is one better equipped to resist famine? Or do you just have more cancer or more heart disease? To have epigenetic effects be an explanation for adaptations, it would seem you’d have to show that the effects of a stress are to better adapt the descendants to that stress.
If I understood correctly epigenetics has been mainly reduced to DNA methylation and histone acetylation. I think that is but a minor part of gene expression. Sadly transmission factors appear not to be on the epigenetic menu.
What is rarely mentioned is that epigenetic changes are often not adaptive at all, apart from persisting only a generation or two.
However, this is quite interesting, albeit unsettling: https://www.darpa.mil/news-events/2018-02-01
Assuming that trauma can have a discernible effect on the F1 and F2 generation, I can see how articles about it would serve the public interest as an awareness-gathering tool about potential problems down the line. The children and grandchildren of the Syrian conflict could then continue to have issues, for example.
But that is assuming that this thing is even real. And it may not be very real at all.
Does not look like real. I can immediately predict that the children and grandchildren of the Syrian conflict will continue to have issues while those of the Holocaust will be magically free of any issues.
It would be impossible to tell if the effects on Syrian children are genetic or environmental.
As always, the answer is “yes”. (Or less snarkily, both.)
Thanks for this post. I didn’t realize that covariate mining had become such a widespread gimmick in the literature, particularly in the epigenetics cottage industry. Many, many years ago, I reviewed a paper in a different field (having to do with errors in protein synthesis) which presented a huge table of associations of one fraction of cases of something with another fraction of cases of something—I no longer remember the details. A few of the associations were in boldface and marked “significant at the 5% level”. These few represented, in fact, about 5% of all the entries in the huge Table. I rejected the paper. Later I noticed that it turned up published, with little change and the same argument, in a different journal.
Was the bonneforoni correction used?
The horror! Snowflakes “damaged” by being upset and stressed now have have a “scientific” basis for lawsuits! Since it also damages their children, a sympathetic, but ignorant jury could award millions. Hiring expert witnesses to support their claims should be no problem.
Lamarckian epigenetics is wildly popular among SJWs. It provides a work-around to darwinian inheritance that poses such a threat to their tabula rasa assumptions that rationalize their grand social engineering projects.
Yes. But the right, too, hates darwinian inheritance in all its manifestations.
Not so sure about that, Mike. Creationists obviously reject (their mischaracterization of) darwinism. But many on the right, especially alt-right, tend to if anything overestimate the role of nature vs. nurture.
My alarm comes from how wide anti-science rubbish like lamarckism has spread among the Left which preens about being pro-science.
* The father’s behavior post-PoW could affect the pregnant mother, causing embryological perturbations;
* The ex-PoW father’s behavior could affect his son during a critical developmental stage in early childhood.
The effect of father’s epigenetic trauma on the child might be measured where the child is conceived immediately before the trauma starts and immediately after the trauma has occurred.
I’ll await the data
People hate Darwinian natural selection and want to see it die.
This is just my impression as a college educator taking biology classes on a tuition waiver, but ever since Darwin proposed his theory, incredulity has reigned.
From Goldschmidt, to the saltationists, on down, there has been this thread of disbelief in the incremental nature of mutation and natural selection that just pisses people off.
They hate the contingent nature of life. They want to be special. They ain’t.
“the comparison doesn’t rule out the abuse hypothesis at all. Why not?”
[ I’m assuming everything we need is in the paragraph ]
they claimed that sons born after the PoW experience did not have a “spike in mortality” but neither, presumably, did any daughters, but they don’t say this.
that’s the best single answer I can come up with. Now to read other readers’ answers.
[ correction to answer ]
sons born after the PoW experience DID have a “spike in mortality”.
and they didn’t say if daughters did or didn’t. they’d have to, to start to make sense.
ok, now I’ll look.
Setting aside the somewhat dubious nature of the statistical analysis, as described by Mitchell, the real issue to me is that the effects are all relatively small – either a very small effect on many individuals, or more often, an effect on only a small portion of the study group.
For most people, it means that at least 90% of the time or more, there will no effect on your family, even if these epigenetic effects pan out as real things. It simply does not occur often enough or consistently enough to have a meaningful effect on populations.
I feel a bit inadequate commenting on this because I’m not a scientist. But I wanted to say how interesting I found it because I know less people comment on this sort of post and it makes it seem like they’re not as popular.
Many of the comments of Michaels are as risible as the wild claims of effects lasting for many generations in human populations. Sadly, the stealing of the term epigenetics to denote changes in methylation, ignores the intergenerational maternal and paternal effects now firmly established across the animal and plant kingdoms that are generated by different mechanisms, some of which are also now well established. Some humility on the part of molecular geneticists would be welcome. Oh, and Jerry really needs to read that literature.
As a layperson I read with interest _Evolution in Four Dimensions_. I didn’t find it terribly persuasive – and this was before I had read Jerry’s and other discussions on the matter. What do you find interesting here that he is missing?
Trofim Lysenko resurrected.
https://en.wikipedia.org/wiki/Trofim_Lysenko
Thx, useful (for sad but obvious reasons)!
I don’t see the BBC idea in the test, all they claim is a non-mechanism correlation (can happen in both cases).