Epigenetics is one of those things that seems wild until you pull the camera back a bit. A cell is affected by and responds to its surroundings - this is not controversial. In eukaryotes, this is usually done by way of altering gene expression - up- or down-regulation by means of chemical markers on the cell’s DNA which are created or removed by enzymes which are activated or deactivated by certain substances in the cell or its environment - in other words, the cell’s environment affects gene regulation within the cell by traceable mechanisms*. All cells, save at least one, are descendent of other cells, and cells split by meiosis, in which the chemical environment within and without the cell is shared by the “descendent” cell - so of course this happens with human embryos as well. Of course the expression of your genes is affected by what happened to your parents (well, your mother, at least), because gene expression is affected by what happens to a cell and you are made up of a lineage of cells descended from your mother’s cells. If you ask how one organism could be affected by something it didn’t experience, sure, that could be a quandary, but looking at a line of cells and wondering how later ones could be affected by environmental pressures on earlier ones isn’t nearly as much of a mystery, and we’re all just extended cell lineages.
(As if first time mothers didn’t have enough to worry about - stop stressing so much, it could lead to long-lasting irreversible changes to your fetus!)
* Standard biology disclaimers: this is not the only way this happens, this varies across species and time, nature has no master plan. “Some of the time some genes have some amount of their expression modified somewhat by some mechanisms that are somewhat responsive to some part of the cell’s environment sometimes.”
Being confused about how 2 environments could produce different individuals even though they are given the same DNA is like being confused about how 2 compilers could produce different binaries even though they are given the same source code.
What I don't like when people bend over backwards to hype epigenetics:
1. the lack of historical context and opinion lock-in once expressed: before the human genome project many geneticists thought the number of "genes" (yes its an oversimplification) would be much much larger than what was eventually discovered to be the case. It was a shock to many biologists, that there were just about tens of thousands of genes in the genome, basically "a handful" in terms of control theory. The miracle of life started to look marginal and banal, just like many protested the earth not being the center of the solar system...
2. no highlighting the difference between single-cellular species and multi-cellular species: generational memory effects are obviously observable for single-cell organisms. For multi-cellular organisms, like humans, the concept of generation is ambiguous: is one talking about cellular generations (fertilized egg cell, dividing and the daughter cells dividing again, ...), or about organism-level generations (human parents of human children)? It becomes immediately apparent that the cell lineage from fertilized egg cell, to either sperm cell of the son or egg cells of the daughter, would involve lots of divisions, and the final sperm or egg cell would only have access to vague general variables: blood sugar levels, temperature, some hormonal levels, ...
3. Just like one can not truly study physics, without learning mathematics, and then formulating claims and observations mathematically, to truly study biology and the homeostasis it implements, you need systems biology: a mathematical description of biology. To understand multicellular organisms, one needs to understand the concept of cell types mathematically, and to summarize it in natural language cell types are the stable attractors forcing the cell contents to return to the closest state of the cell type. To make a rough analogy (cell/human, cell type/profession) then in contrary to humans, cell's don'
t have any memory which is independent of their cellular content. So apart from the content of the cell, a cell is amnesiac. Imagine humans without memory, but upon seeing the room in which they work, they can constantly re-understand what role they perform, and any deviation from what is ingrained in your local DNA copy of the genome is responded to. If you find yourself in a room with ovens and lots of dough, and some of the ovens have bread, but for some reason there's a cop's badge on the table, then you know you are a baker, and you throw out the cop's badge. If you are in a special car with red and blue lights, and you are behind the wheel, but there is for some reason an oven sitting on the passenger seat, then you are a cop, and you take the oven out of your police car.
Once you understand how cell types implement the memory necessary so that a neuron in your brain doesn't start to behave like a skin cell on your anus or vice versa, you understand the ridiculous proposition of epigenetics, a quest for the holy grail of all the missing information that the human genome project failed to find... Euhm well sure there is some modulation of transcription by histone modifications etc... but all of that can be modeled in the same language of reactions that is currently used to model Gene Regulatory Networks, with Gillespie simulators etc. Instead of wishing to vindicate ones old (and wrong) forgotten statements from before the human genome project due to psychological lock-in effects, it would be more productive to point out that in practice a lot of known useful data is ignored, so why not first make use of information we know exists before ingraining vague ideas about epigenetics in the next generation of students? stop ignoring the promotor regions and consensus sequences etc when sequencing genomes, there is a wealth of information to be had there, and personalized DNA-driven medicine will never take off until these are by default sequenced as well, as they directly relate to transcription rates! you know, good old classical gene regulatory network data.
The problem with this perspective is that you would expect the effect of a past environmental influence to be overwritten by a future environmental influence. The idea that the effect of the past influence would persist is what is questionable.
no, no it does not strip protien complexes away from the DNA strand.
it involves a localized progression along the DNA surrounded by histones, and regulatory enzymes, displaced from proximity, until the replication fork zooms on through, and it all snaps back together.
the process is error prone, strands may cross over, chromosomes may fail to migrate properly.
>>> (As if first time mothers didn’t have enough to worry about - stop stressing so much, it could lead to long-lasting irreversible changes to your fetus!)
This is plainly not plausible. "Irreversible" doesn't play well with the length of time humans have been a thing.
Ask a parent what they hear when they hear “irreversible” in conjunction with their child. I promise nobody mistook that for “until the heat death of the universe,” but I can add a note if you really think it’s warranted.
But even reversible changes aren’t always “reversed”. They aren’t necessarily minor.
Sure, breaking an arm or skipping high school can be a “reversible” change. But not often not fully “reversed” and/or not done so in a negligible time frame. There are costs. Seems like biological development could be similar.
So one thing missing from the excitement around this line of work: how little these worm effects generalize to mammals.
C. elegans has very unusual biology — direct soma→germline communication pathways, minimal nervous systems, and short generational cycles. Epigenetic inheritance is much easier to observe there than in mice or humans, where mechanisms differ and dilution across meiosis tends to erase these “marks.”
This means that, even if the PA14 avoidance effect replicates, it’s not evidence that humans inherit learned behaviours. It’s evidence that worms are an interesting edge-case system.
> While the Murphy group consistently observed this attraction in their assays, the Hunter group generally did not (Kaletsky et al., 2025). The Vidal-Gadea group also observed that worms that had not been exposed to PA14 were initially attracted to it, suggesting that this is an important piece of the puzzle (Akinosho et al., 2025). Indeed, when tested directly, the Murphy group did not observe attraction using the temperature-shift method (Kaletsky et al., 2025). However, whether the omission of azide alone explains the discrepancy between the studies is not clear. In a handful of assays, the Hunter group used azide but failed to see the initial attraction to PA14, or to observe learned avoidance in the F2 generation.
Every time I look into epigenetic inheritance studies I run into a lot of finicky experiments like this, where the outcomes appear to be highly dependent on several variables that aren’t fully understood.
One group of researchers claims to have pinned down the results, but as someone outside of this world trying to interpret the studies it’s hard to know how well they’ve really controlled these finicky experiments to isolate the single effect (epigenetic inheritance) that they claim explains everything.
By waving away the hard parts you’re missing why it’s not a simple question in the context of this paper (what I was writing about).
The behavioral test they used showed different results under different circumstances. Even variables like temperature might impact the behavior exhibited in the test.
> You always have to distill complicated papers that babble about things to a minimum statement.
Disagree. You always have to read the papers and understand the details.
3. I've been to a few conferences which mixed geneticists with (human) epigenetics guys, and I have never been impressed with the quality of their work. Lots of different measures of "biological clocks". Lots of multiple hypotheses without much correcting for them. No clear theory. I ended up being very skeptical.
I’d be curious to get to the heart of why we believe heritability in behavior is due to genetic changes. It’s way more likely to be due to mimetic changes.
Throwing out a fundamentals text is valid. But you need to point out where OP made a mistake that's so elementary it requires going back to the basics for it to not come across as low dismissal.
the entire OP displays a lack of knowledge regarding epigenetic mechanisms, as well as a lack ot knowledge base required to make an informed appraisal.
the knowledge base required, is extensive for a non biologist, and made difficult to attain without experience interpreting decades long synthesis.
thus the fundamentals are provided, should anyone desire breadcrumbs pursuant to independant edifiction.
I'm a scientist with about four published papers in genetics - not a geneticist myself, but I coauthor. I'm simply reporting my experience with the field.
there is a claim that epigenetic mechanisms in bacteria provide weak support for such in humans, not true it was the basis for realizing that epigenetic mechanisms exist, and was central to understanding regulaion of expression.
there is a claim that meiosis resets the genome and that is absolutely untrue.
regulation would be impossible if epigenetic state was wiped out, the result is most often cancer, or lethal dose effects at the cellular stage of development.
you say you are not a geneticist yet you are criticizing geneticists for presentation of hypotheses while lacking the background.
timing of binding and procession reative to halflife of the expression complex is a critical part of regulation of genetic activity.
i am a scientist as well, molecular geneticist; organic chemist, nuclear physicist. i am a true polymath, this is not a meme, i contract for a body of government agencies, as a science officer, thus my ID and fine details of my work are not up for discussion, nor is any of my work for the last 10 years.
i would however be fine discussing generalities of expression regulation systems if you like.
There has been aruably a more serious blow to the pure Darwinian evolution (this is all epigenetics, after all): non-random occurrence of useful mutations in populations exposed to particular diseases.
I wonder how that works? Speculation: there is some kind of genetic/epigenetic signalling which modulates DNA repair mechanisms, such that certain DNA regions can be marked as more mutation-prone than others. And there may be selective pressure to make genes associated with disease-resistance more mutation-prone, because that’s a gene whose mutation is more likely to be beneficial (compensating mutations for evolution in existing diseases or to respond to new diseases), less likely to be harmful (most of the time, most likely outcome of the “wrong” mutation would be less resistance to diseases, but it probably wouldn’t otherwise be lethal or cause serious disability). But if that is what is actually going on here, is there any actual challenge to Darwin’s views? He didn’t know about DNA; I don’t think he ever claimed all mutations were equally likely (why would he when he had no idea what the actual mechanisms behind them were)
darwin had the idea that many individuals with variation were culled according to relative fitness.
mendel later demonstrated that this variation was passed fractionally, to decendants. this was a conserved probability of fixed combinations
[consult "mendels peas" ]
the two taken together resulted in neo-darwinist mechanisms.
darwin was not wrong, mendel was less wrong, contemporarily we are still scratching the surface of getting it right, primarily what rules apply to what groups, what mechanisms are conserved, what combinations of functions are served by a particular structure, departing from the one gene one function hypothesis.
I don’t really see that as anti-Darwinian. Those genes successfully attach themselves to a new organism and provide advantages such that they are selected for in the population.
The selection is classical, but the mutations are supposed to be random, not skewed towards more useful genetic variants. One can speculate that a purely random (and otherwise neutral, say) prior mutation led to this directionality, but the actual resulting mechanism is AFAIK still unknown.
Natural selection has nothing to do with randomness per se, it’s merely differential selection based on environmental fitness. The fitness function of a given environment can even narrow a range of existing genes without any mutation occurring during the period where the new fitness function is applied. The classic example of this is peppered moths shifting toward the darker range of their preexisting color range during the Industrial Revolution.
Horizontal gene transfer is another way organisms can acquire new traits.
It's clear that purely random mutations don't work in the sense that an infinite number of monkeys won't produce Shakespeare even if you kill of the monkeys that fail.
The monkeys would write Shakespeare if you tested their output character by character instead of waiting till the end. That's how evolution works too - in tiny cumulative achievable steps.
Even if this was going to hold up, it wouldn't make the policies that Lamarck's ideas were designed to promote work. We already empirically know they don't work.
What’s striking about this work is how learned avoidance behaves almost like a biological version of the Reality Drift Equation. Ancestral experience compressing into molecular memory that shapes behavior long before direct exposure. The fact that these worms inherit a kind of preparedness across generations highlights how evolution uses temporal drift to pass forward subtle informational traces of past environments. It’s a reminder that cognition isn’t just in the brain. Even simple organisms carry forward patterned responses that function like inherited signals of meaning.
This relates to policy because it addresses the question of whether we carry epigenetic baggage from prior generations. For example, trauma that our parents, or grandparents experienced could lead to behavior modifications and poorer outcomes in us. If that is the case, it has profound public policy implications.
There is a vast gap between current epigenetic inheritance science in humans and all of the theories that epigenetic inheritance is a substantial carrier of inter generational trauma.
We’re still trying to figure out how much, if any, epigenetic inheritance applies to humans. If we did find some evidence, it wouldn’t be as simple as declaring that the trauma of previous generations harmed offspring. For example, it could be equally likely that offspring of prior generations that endured a lot of stress were actually more stress resilient and therefore received some advantages.
> If that is the case, it has profound public policy implications.
I disagree. As I said above, anyone jumping to conclusions that epigenetic inheritance could only confer negative traits is trying to force another concept (inter-generational trauma) into a convenient scientific carrier to make it appear to be a more valid policy position.
Those are articles about maternal stress during pregnancy.
The trans-generational epigenetic inheritance proponents claim that trauma can induce lasting generational effects spanning multiple levels of descendants, even if it doesn’t occur during to the mother during pregnancy.
The paper this HN submission is talking about claims to have found an effect like this that persists for 4 generations.
A key problem with the inter generational trauma proponents is that they presume the effects will only be negative. However, studies like this one showed a positive adaptation. Evolutionarily, it would make more sense if epigenetic mechanisms generally conferred benefits and learned adaptations, which goes against the narratives that anything negative would produce lasting negative effects. It’s not entirely that simple, but it reveals why the intergenerational trauma equals epigenetic inheritance people are starting with a conclusion and trying to get the science to fit their narrative, which is backward from how it should be.
I agree with you there's a lot hand-wavy jumping to conclusions and claims human effects often feel like pop pseudo-science. However I do think when folks imply that epigenetic effects are negative they tend to point towards things like anxiety and fear. Anxiety very well could have a protective evolutionary benefit if you assume the next generation will also be born in a high-risk environment, but a generation later these qualities would be perceived as a negative consequence.
Another example is famine, it may be advantegous to store visceral fat in a low food environment, but if the famine ends, the next generation is more likely to carry this "advantage" which is now negative:
https://www.sciencedirect.com/science/article/pii/S216183132...
I suppose one would have to follow the cohort and see if the epigenetic changes observed so far carry over into their own children. I do find it interesting that stress in the mother becomes higher BMI in the offspring. It makes sense if you're talking about animals trying to survive in a harsh environment.
> trauma that our parents, or grandparents experienced could lead to behavior modifications and poorer outcomes in us
The nurture part of it is already well established, this is the nature part of it.
However, this is not a net-positive for the folks who already discriminate.
The "faults in our genes" thinking assumes that this is not redeemable by policy changes, so it goes back to eugenics and usually suggests cutting such people out of the gene pool.
The "better nurture" proponents for the next generation (free school lunches, early intervention and magnet schools) will now have to swim up this waterfall before arguing more investment into the uplifting traumatized populations.
We need to believe that Change (with a capital C) is possible right away if start right now.
I would think it's the opposite. Intervention is preventative of further sliding. The alternative - genocide - is expensive; they're generally a luxury of states benefiting from a theft-based windfall.
This would require that it's a one-way door, where bad circumstances persist indefinitely across generations but good circumstances don't. It would also require that to not stretch back too far, since bad circumstances were rather universal before the modern age.
In order for this supposed oddly specific effect to have policy implications, it would have to be simple to identify which individuals are impacted and by how much. And it would have to be impossible to identify such individuals except by looking at their family history.
And there would have to be some policy action that is uniquely beneficial to those people.
an RNA interference scan of maternal gametic DNA would go a long way toward revealing identified epigenetic modifications; also would not be cheap.
this would also be accompanied by interviews, that would reveal high risk factors, as well as very intimate details of family history.
the payoff would have to be large, something more than the wellbeing of a single person from start to end, until we collectively grow up a bit more as a species.
They've discovered that eggs from women with certain medical conditions (including stress and poor diet) produce embryos with shorter telomeres, and in middle age the shorter telomeres lead to premature aging and a raft of health problems.
related: sperm from male rats who drink heavily produces children and grandchildren with reduced brain size and abnormal behavior -- there's an epigenetic male 'fetal alcohol syndrome'
What policy implications? Obviously wealth, class, race, nationality, and genetics are all highly heritable, what's one more twig on the pile of the birth lottery?
It’s also a good argument for not allowing children to be victims of their parents’ circumstances. Which is the heart of compulsory schooling and school lunch and a whole host of other things.
Yes, unscientific people will misuse it to support their racist ideas of black people inheriting trauma from slavery. They already do, but they're also extrapolating way beyond what research actually shows.
An absurd take. The ‘trauma’ people, baggage handlers de nos jours, have already weaponised the phenomenon for political points, before we even know definitively if it exists. Hey ho.
Incidentally, nobody yet I see has suggested that epigenetics could lead to better outcomes. I wonder why?
Me, once again tapping the, "If they had done genetic studies on the Dutch at the beginning of the 19th century, genetic patterns currently associated with exceptional adult height may have instead been associated with exceptional short stature," sign.
What social democracy does to a dude('s growth spurts). If people ever internalized that socioeconomic circumstances have material and profound effects on not only their own health and development, but also that of their children and children's children, both in the positive and negative direction... Man.
I think that nowadays "gene" refers only to a subset of a nucleic acid. Sequences of ACTG (or ACUG in the case of RNA) only, and only in that organism's chromosomes.
If you inherit a virus from your mother, for instance, I think most would call that non-genetic inheritance, even though viruses have genes too. Same goes for methyl and acetyl markers, transcription factors, nutrients, toxins, and whatever else comes along for the ride in the meiotic cell.
Back in the day when they didn't know which cellular chemical was responsible for the majority of heritability I think the usage was indeed more general. But now we have "the central dogma of biology" which puts nucleic acids on a pedestal. Convenient to have rules so you can keep track of their many exceptions.
Could you restate this? I believe "genetic" usually refers to only the sequence of linear bases, while epigenetics refers to histone acetylation, and base methylation (And other things perhaps). These are also heritable, and regulate protein expression in a way that, like genetics, affects phenotype.
But there might be other ways that some traits get inherited, eg by changing the cellular environment in the sperm/egg itself which could affect the offspring while keeping the genes the same.
Maybe he's trying to go to the earliest idea of "gen-es" aka the reasons for the traits of an individual. The idea existed before the discovery of cells kernels and DNA right ? so in a way, if there are other mechanisms involved in passing traits to children, it could be termed as gen-something
Yes, that depends on the definition. Lamarck could fit into it, but he had no clue about DNA, genes and so forth; neither had Darwin. He babbled about gemmulae.
Even the definition of a gene is not very accurate. Many important sequences yield a miRNA or another RNA. Only few sequences yield a mRNA. Some "genes" are just integrated viruses/phages/transposons etc... that were modified. One of the most fascinating one was the retrovirus in regards to the mammalian placenta: https://pmc.ncbi.nlm.nih.gov/articles/PMC4332834/ but there are many more examples. We are all DNA hybrids at the end of the day. The whole species concepts makes very little sense these days, IMO. I can see the use case for eukaryotes, but it makes no sense to me for bacteria yet alone viruses.
Epigenetic inheritance is a mechanism whereby traits could be passed from one generation to the next without modifying the underlying genetic DNA. The mechanism would alter the expression of different parts of DNA.
It’s a very young field with a lot of open questions. The concept has been adopted and abused in the mainstream so you have to be careful to separate the science from the pseudoscience.
That depends on the definition. But, if we use the modern definition, it emerged (or re-emerged) in the 1990s. It's not old, indeed, but I also would no longer call it "very young". It's soon 40 years in the modern definition, and much older if we include prior discussions.
Epigenetics is one of those things that seems wild until you pull the camera back a bit. A cell is affected by and responds to its surroundings - this is not controversial. In eukaryotes, this is usually done by way of altering gene expression - up- or down-regulation by means of chemical markers on the cell’s DNA which are created or removed by enzymes which are activated or deactivated by certain substances in the cell or its environment - in other words, the cell’s environment affects gene regulation within the cell by traceable mechanisms*. All cells, save at least one, are descendent of other cells, and cells split by meiosis, in which the chemical environment within and without the cell is shared by the “descendent” cell - so of course this happens with human embryos as well. Of course the expression of your genes is affected by what happened to your parents (well, your mother, at least), because gene expression is affected by what happens to a cell and you are made up of a lineage of cells descended from your mother’s cells. If you ask how one organism could be affected by something it didn’t experience, sure, that could be a quandary, but looking at a line of cells and wondering how later ones could be affected by environmental pressures on earlier ones isn’t nearly as much of a mystery, and we’re all just extended cell lineages.
(As if first time mothers didn’t have enough to worry about - stop stressing so much, it could lead to long-lasting irreversible changes to your fetus!)
* Standard biology disclaimers: this is not the only way this happens, this varies across species and time, nature has no master plan. “Some of the time some genes have some amount of their expression modified somewhat by some mechanisms that are somewhat responsive to some part of the cell’s environment sometimes.”
Being confused about how 2 environments could produce different individuals even though they are given the same DNA is like being confused about how 2 compilers could produce different binaries even though they are given the same source code.
What I don't like when people bend over backwards to hype epigenetics:
1. the lack of historical context and opinion lock-in once expressed: before the human genome project many geneticists thought the number of "genes" (yes its an oversimplification) would be much much larger than what was eventually discovered to be the case. It was a shock to many biologists, that there were just about tens of thousands of genes in the genome, basically "a handful" in terms of control theory. The miracle of life started to look marginal and banal, just like many protested the earth not being the center of the solar system...
2. no highlighting the difference between single-cellular species and multi-cellular species: generational memory effects are obviously observable for single-cell organisms. For multi-cellular organisms, like humans, the concept of generation is ambiguous: is one talking about cellular generations (fertilized egg cell, dividing and the daughter cells dividing again, ...), or about organism-level generations (human parents of human children)? It becomes immediately apparent that the cell lineage from fertilized egg cell, to either sperm cell of the son or egg cells of the daughter, would involve lots of divisions, and the final sperm or egg cell would only have access to vague general variables: blood sugar levels, temperature, some hormonal levels, ...
3. Just like one can not truly study physics, without learning mathematics, and then formulating claims and observations mathematically, to truly study biology and the homeostasis it implements, you need systems biology: a mathematical description of biology. To understand multicellular organisms, one needs to understand the concept of cell types mathematically, and to summarize it in natural language cell types are the stable attractors forcing the cell contents to return to the closest state of the cell type. To make a rough analogy (cell/human, cell type/profession) then in contrary to humans, cell's don' t have any memory which is independent of their cellular content. So apart from the content of the cell, a cell is amnesiac. Imagine humans without memory, but upon seeing the room in which they work, they can constantly re-understand what role they perform, and any deviation from what is ingrained in your local DNA copy of the genome is responded to. If you find yourself in a room with ovens and lots of dough, and some of the ovens have bread, but for some reason there's a cop's badge on the table, then you know you are a baker, and you throw out the cop's badge. If you are in a special car with red and blue lights, and you are behind the wheel, but there is for some reason an oven sitting on the passenger seat, then you are a cop, and you take the oven out of your police car.
Once you understand how cell types implement the memory necessary so that a neuron in your brain doesn't start to behave like a skin cell on your anus or vice versa, you understand the ridiculous proposition of epigenetics, a quest for the holy grail of all the missing information that the human genome project failed to find... Euhm well sure there is some modulation of transcription by histone modifications etc... but all of that can be modeled in the same language of reactions that is currently used to model Gene Regulatory Networks, with Gillespie simulators etc. Instead of wishing to vindicate ones old (and wrong) forgotten statements from before the human genome project due to psychological lock-in effects, it would be more productive to point out that in practice a lot of known useful data is ignored, so why not first make use of information we know exists before ingraining vague ideas about epigenetics in the next generation of students? stop ignoring the promotor regions and consensus sequences etc when sequencing genomes, there is a wealth of information to be had there, and personalized DNA-driven medicine will never take off until these are by default sequenced as well, as they directly relate to transcription rates! you know, good old classical gene regulatory network data.
The problem with this perspective is that you would expect the effect of a past environmental influence to be overwritten by a future environmental influence. The idea that the effect of the past influence would persist is what is questionable.
Great writeup!
And as someone less knowledgeable about biological sciences than others, I think learned even more from your disclaimers!
p.s. If you know any good sources for adults to catch up on some biology basics, let me know.
Does meiosis involve a reset mechanism of any kind?
The reset happens in the days following fertilization. Pretty much 100% of human DNA gets demethylated then.
no, no it does not strip protien complexes away from the DNA strand.
it involves a localized progression along the DNA surrounded by histones, and regulatory enzymes, displaced from proximity, until the replication fork zooms on through, and it all snaps back together.
the process is error prone, strands may cross over, chromosomes may fail to migrate properly.
>>> (As if first time mothers didn’t have enough to worry about - stop stressing so much, it could lead to long-lasting irreversible changes to your fetus!)
This is plainly not plausible. "Irreversible" doesn't play well with the length of time humans have been a thing.
Ask a parent what they hear when they hear “irreversible” in conjunction with their child. I promise nobody mistook that for “until the heat death of the universe,” but I can add a note if you really think it’s warranted.
You definitely make a good point.
But even reversible changes aren’t always “reversed”. They aren’t necessarily minor.
Sure, breaking an arm or skipping high school can be a “reversible” change. But not often not fully “reversed” and/or not done so in a negligible time frame. There are costs. Seems like biological development could be similar.
Worms are great, but they're not your grandma.
So one thing missing from the excitement around this line of work: how little these worm effects generalize to mammals.
C. elegans has very unusual biology — direct soma→germline communication pathways, minimal nervous systems, and short generational cycles. Epigenetic inheritance is much easier to observe there than in mice or humans, where mechanisms differ and dilution across meiosis tends to erase these “marks.”
This means that, even if the PA14 avoidance effect replicates, it’s not evidence that humans inherit learned behaviours. It’s evidence that worms are an interesting edge-case system.
> While the Murphy group consistently observed this attraction in their assays, the Hunter group generally did not (Kaletsky et al., 2025). The Vidal-Gadea group also observed that worms that had not been exposed to PA14 were initially attracted to it, suggesting that this is an important piece of the puzzle (Akinosho et al., 2025). Indeed, when tested directly, the Murphy group did not observe attraction using the temperature-shift method (Kaletsky et al., 2025). However, whether the omission of azide alone explains the discrepancy between the studies is not clear. In a handful of assays, the Hunter group used azide but failed to see the initial attraction to PA14, or to observe learned avoidance in the F2 generation.
Every time I look into epigenetic inheritance studies I run into a lot of finicky experiments like this, where the outcomes appear to be highly dependent on several variables that aren’t fully understood.
One group of researchers claims to have pinned down the results, but as someone outside of this world trying to interpret the studies it’s hard to know how well they’ve really controlled these finicky experiments to isolate the single effect (epigenetic inheritance) that they claim explains everything.
It can be simplified to this question:
- Do C. elegans offspring show a modified behaviour unrelated to a changed genome sequence?
That is a fairly simple question. The answer to it should be simple too.
You always have to distill complicated papers that babble about things to a minimum statement.
By waving away the hard parts you’re missing why it’s not a simple question in the context of this paper (what I was writing about).
The behavioral test they used showed different results under different circumstances. Even variables like temperature might impact the behavior exhibited in the test.
> You always have to distill complicated papers that babble about things to a minimum statement.
Disagree. You always have to read the papers and understand the details.
> That is a fairly simple question. The answer to it should be simple too.
This hardly follows.
Agreed. Also, "simple isn't easy".
> That is a fairly simple question. The answer to it should be simple too.
"Is P equal to NP" is also a simple question.
The answer should be simple, too -- either yes or no. OP did not imply proving it would be simple.
I'm pretty sure that you won't be able to claim your 1 million dollars from the Clay Mathematics Institute by just answering yes or no.
That's why I'm going to go with a friend. I'll say yes, he'll say no, and we'll split the winnings. Easy money.
OP did imply that the paper contained the simple answer, though.
It’s easy to say that the truth is simple if you ignore everything about exploring whether or not a paper is an accurate representation of the truth.
1. Pretty obviously, epigenetics in bacteria provides only very weak support for epigenetics in humans.
2. The case against epigenetics in humans is laid out nicely by Razib Khan: https://www.razibkhan.com/p/you-cant-take-it-with-you-straig...
3. I've been to a few conferences which mixed geneticists with (human) epigenetics guys, and I have never been impressed with the quality of their work. Lots of different measures of "biological clocks". Lots of multiple hypotheses without much correcting for them. No clear theory. I ended up being very skeptical.
I’d be curious to get to the heart of why we believe heritability in behavior is due to genetic changes. It’s way more likely to be due to mimetic changes.
in terse, behaviour is dependent on neural activity; neural activity is dependent on expressivity, and penetrance of genetic constituency.
https://en.wikipedia.org/wiki/Behavioural_genetics
https://assets.cambridge.org/97811084/87979/frontmatter/9781... [PDF]
here is some reading for you:
https://www.sciencedirect.com/science/chapter/edited-volume/...
https://pmc.ncbi.nlm.nih.gov/articles/PMC12204592/
https://sciencevivid.com/epigenetics/
Throwing out a fundamentals text is valid. But you need to point out where OP made a mistake that's so elementary it requires going back to the basics for it to not come across as low dismissal.
the entire OP displays a lack of knowledge regarding epigenetic mechanisms, as well as a lack ot knowledge base required to make an informed appraisal.
the knowledge base required, is extensive for a non biologist, and made difficult to attain without experience interpreting decades long synthesis.
thus the fundamentals are provided, should anyone desire breadcrumbs pursuant to independant edifiction.
I'm a scientist with about four published papers in genetics - not a geneticist myself, but I coauthor. I'm simply reporting my experience with the field.
human gene regulation is dependent on methylation events and acetylation events, as well as conformal events with respect to the strand.
there is no meiotic reset to default.
you should hang with some oncogeneticists for fresh perspective.
And absolutely none of that refutes the claims from Kahn that started this thread.
no thats wrong.
there is a claim that epigenetic mechanisms in bacteria provide weak support for such in humans, not true it was the basis for realizing that epigenetic mechanisms exist, and was central to understanding regulaion of expression.
there is a claim that meiosis resets the genome and that is absolutely untrue. regulation would be impossible if epigenetic state was wiped out, the result is most often cancer, or lethal dose effects at the cellular stage of development.
you say you are not a geneticist yet you are criticizing geneticists for presentation of hypotheses while lacking the background.
timing of binding and procession reative to halflife of the expression complex is a critical part of regulation of genetic activity.
i am a scientist as well, molecular geneticist; organic chemist, nuclear physicist. i am a true polymath, this is not a meme, i contract for a body of government agencies, as a science officer, thus my ID and fine details of my work are not up for discussion, nor is any of my work for the last 10 years.
i would however be fine discussing generalities of expression regulation systems if you like.
So Lamarck wasn't entirely incorrect either. Darwin would have been fascinated by these results.
There has been aruably a more serious blow to the pure Darwinian evolution (this is all epigenetics, after all): non-random occurrence of useful mutations in populations exposed to particular diseases.
https://pubmed.ncbi.nlm.nih.gov/40854136/
I wonder how that works? Speculation: there is some kind of genetic/epigenetic signalling which modulates DNA repair mechanisms, such that certain DNA regions can be marked as more mutation-prone than others. And there may be selective pressure to make genes associated with disease-resistance more mutation-prone, because that’s a gene whose mutation is more likely to be beneficial (compensating mutations for evolution in existing diseases or to respond to new diseases), less likely to be harmful (most of the time, most likely outcome of the “wrong” mutation would be less resistance to diseases, but it probably wouldn’t otherwise be lethal or cause serious disability). But if that is what is actually going on here, is there any actual challenge to Darwin’s views? He didn’t know about DNA; I don’t think he ever claimed all mutations were equally likely (why would he when he had no idea what the actual mechanisms behind them were)
darwin had the idea that many individuals with variation were culled according to relative fitness.
mendel later demonstrated that this variation was passed fractionally, to decendants. this was a conserved probability of fixed combinations [consult "mendels peas" ]
the two taken together resulted in neo-darwinist mechanisms. darwin was not wrong, mendel was less wrong, contemporarily we are still scratching the surface of getting it right, primarily what rules apply to what groups, what mechanisms are conserved, what combinations of functions are served by a particular structure, departing from the one gene one function hypothesis.
I don’t really see that as anti-Darwinian. Those genes successfully attach themselves to a new organism and provide advantages such that they are selected for in the population.
The selection is classical, but the mutations are supposed to be random, not skewed towards more useful genetic variants. One can speculate that a purely random (and otherwise neutral, say) prior mutation led to this directionality, but the actual resulting mechanism is AFAIK still unknown.
Natural selection has nothing to do with randomness per se, it’s merely differential selection based on environmental fitness. The fitness function of a given environment can even narrow a range of existing genes without any mutation occurring during the period where the new fitness function is applied. The classic example of this is peppered moths shifting toward the darker range of their preexisting color range during the Industrial Revolution.
Horizontal gene transfer is another way organisms can acquire new traits.
plasmids
https://en.wikipedia.org/wiki/Plasmid
It's clear that purely random mutations don't work in the sense that an infinite number of monkeys won't produce Shakespeare even if you kill of the monkeys that fail.
The monkeys would write Shakespeare if you tested their output character by character instead of waiting till the end. That's how evolution works too - in tiny cumulative achievable steps.
Lysenko wasn't entirely wrong then, crazy.
In Lamarkian evolution features that organisms use either accentuate or attenuate. That's not how epigenetics works in general.
Even if this was going to hold up, it wouldn't make the policies that Lamarck's ideas were designed to promote work. We already empirically know they don't work.
viewing genetics as dogmatic darwinist purity isnt the state of the art.
current genetic theory is a synthesis, loosely referred to as neo-darwinism
https://en.wikipedia.org/wiki/Neo-Darwinism
What’s striking about this work is how learned avoidance behaves almost like a biological version of the Reality Drift Equation. Ancestral experience compressing into molecular memory that shapes behavior long before direct exposure. The fact that these worms inherit a kind of preparedness across generations highlights how evolution uses temporal drift to pass forward subtle informational traces of past environments. It’s a reminder that cognition isn’t just in the brain. Even simple organisms carry forward patterned responses that function like inherited signals of meaning.
Honest question: isn’t all inheritance transgenerational?
Sure, but epigenetics is inheritance that does not have an associated genetic sequence change. The DNA sequence is identical.
This relates to policy because it addresses the question of whether we carry epigenetic baggage from prior generations. For example, trauma that our parents, or grandparents experienced could lead to behavior modifications and poorer outcomes in us. If that is the case, it has profound public policy implications.
There is a vast gap between current epigenetic inheritance science in humans and all of the theories that epigenetic inheritance is a substantial carrier of inter generational trauma.
We’re still trying to figure out how much, if any, epigenetic inheritance applies to humans. If we did find some evidence, it wouldn’t be as simple as declaring that the trauma of previous generations harmed offspring. For example, it could be equally likely that offspring of prior generations that endured a lot of stress were actually more stress resilient and therefore received some advantages.
> If that is the case, it has profound public policy implications.
I disagree. As I said above, anyone jumping to conclusions that epigenetic inheritance could only confer negative traits is trying to force another concept (inter-generational trauma) into a convenient scientific carrier to make it appear to be a more valid policy position.
There's some long running research on the effect in humans like this:
https://theconversation.com/moms-prenatal-hardship-turns-bab...
https://pubmed.ncbi.nlm.nih.gov/26098974/
Those are articles about maternal stress during pregnancy.
The trans-generational epigenetic inheritance proponents claim that trauma can induce lasting generational effects spanning multiple levels of descendants, even if it doesn’t occur during to the mother during pregnancy.
The paper this HN submission is talking about claims to have found an effect like this that persists for 4 generations.
A key problem with the inter generational trauma proponents is that they presume the effects will only be negative. However, studies like this one showed a positive adaptation. Evolutionarily, it would make more sense if epigenetic mechanisms generally conferred benefits and learned adaptations, which goes against the narratives that anything negative would produce lasting negative effects. It’s not entirely that simple, but it reveals why the intergenerational trauma equals epigenetic inheritance people are starting with a conclusion and trying to get the science to fit their narrative, which is backward from how it should be.
I agree with you there's a lot hand-wavy jumping to conclusions and claims human effects often feel like pop pseudo-science. However I do think when folks imply that epigenetic effects are negative they tend to point towards things like anxiety and fear. Anxiety very well could have a protective evolutionary benefit if you assume the next generation will also be born in a high-risk environment, but a generation later these qualities would be perceived as a negative consequence.
Another example is famine, it may be advantegous to store visceral fat in a low food environment, but if the famine ends, the next generation is more likely to carry this "advantage" which is now negative: https://www.sciencedirect.com/science/article/pii/S216183132...
I suppose one would have to follow the cohort and see if the epigenetic changes observed so far carry over into their own children. I do find it interesting that stress in the mother becomes higher BMI in the offspring. It makes sense if you're talking about animals trying to survive in a harsh environment.
> trauma that our parents, or grandparents experienced could lead to behavior modifications and poorer outcomes in us
The nurture part of it is already well established, this is the nature part of it.
However, this is not a net-positive for the folks who already discriminate.
The "faults in our genes" thinking assumes that this is not redeemable by policy changes, so it goes back to eugenics and usually suggests cutting such people out of the gene pool.
The "better nurture" proponents for the next generation (free school lunches, early intervention and magnet schools) will now have to swim up this waterfall before arguing more investment into the uplifting traumatized populations.
We need to believe that Change (with a capital C) is possible right away if start right now.
I would think it's the opposite. Intervention is preventative of further sliding. The alternative - genocide - is expensive; they're generally a luxury of states benefiting from a theft-based windfall.
This would require that it's a one-way door, where bad circumstances persist indefinitely across generations but good circumstances don't. It would also require that to not stretch back too far, since bad circumstances were rather universal before the modern age.
In order for this supposed oddly specific effect to have policy implications, it would have to be simple to identify which individuals are impacted and by how much. And it would have to be impossible to identify such individuals except by looking at their family history.
And there would have to be some policy action that is uniquely beneficial to those people.
an RNA interference scan of maternal gametic DNA would go a long way toward revealing identified epigenetic modifications; also would not be cheap.
this would also be accompanied by interviews, that would reveal high risk factors, as well as very intimate details of family history.
the payoff would have to be large, something more than the wellbeing of a single person from start to end, until we collectively grow up a bit more as a species.
They've discovered that eggs from women with certain medical conditions (including stress and poor diet) produce embryos with shorter telomeres, and in middle age the shorter telomeres lead to premature aging and a raft of health problems.
related: sperm from male rats who drink heavily produces children and grandchildren with reduced brain size and abnormal behavior -- there's an epigenetic male 'fetal alcohol syndrome'
But fortunately “We provide proof-of-concept that DNA resetting can be modulated in embryos where it is deficient, using currently available drugs, to influence telomere length at birth" https://www.adelaide.edu.au/robinson-research-institute/news...
What policy implications? Obviously wealth, class, race, nationality, and genetics are all highly heritable, what's one more twig on the pile of the birth lottery?
This sort of thing is always a call for generational guilt and reparations.
It’s also a good argument for not allowing children to be victims of their parents’ circumstances. Which is the heart of compulsory schooling and school lunch and a whole host of other things.
Yes, unscientific people will misuse it to support their racist ideas of black people inheriting trauma from slavery. They already do, but they're also extrapolating way beyond what research actually shows.
An absurd take. The ‘trauma’ people, baggage handlers de nos jours, have already weaponised the phenomenon for political points, before we even know definitively if it exists. Hey ho.
Incidentally, nobody yet I see has suggested that epigenetics could lead to better outcomes. I wonder why?
Me, once again tapping the, "If they had done genetic studies on the Dutch at the beginning of the 19th century, genetic patterns currently associated with exceptional adult height may have instead been associated with exceptional short stature," sign.
What social democracy does to a dude('s growth spurts). If people ever internalized that socioeconomic circumstances have material and profound effects on not only their own health and development, but also that of their children and children's children, both in the positive and negative direction... Man.
The consequences could be terrible if it were intentionally weaponised by a government looks at the Russian empire.
If it's inheritable wouldn't that make it by definition genetic?
I think that nowadays "gene" refers only to a subset of a nucleic acid. Sequences of ACTG (or ACUG in the case of RNA) only, and only in that organism's chromosomes.
If you inherit a virus from your mother, for instance, I think most would call that non-genetic inheritance, even though viruses have genes too. Same goes for methyl and acetyl markers, transcription factors, nutrients, toxins, and whatever else comes along for the ride in the meiotic cell.
Got it. I had thought that actual genes were only a part of what was considered "genetics."
Back in the day when they didn't know which cellular chemical was responsible for the majority of heritability I think the usage was indeed more general. But now we have "the central dogma of biology" which puts nucleic acids on a pedestal. Convenient to have rules so you can keep track of their many exceptions.
No. If the change happens without altering the DNA (or RNA) sequence it's not genetic it's epigenetic.
epi- = outside
Better translation of epi- : on top of.
Could you restate this? I believe "genetic" usually refers to only the sequence of linear bases, while epigenetics refers to histone acetylation, and base methylation (And other things perhaps). These are also heritable, and regulate protein expression in a way that, like genetics, affects phenotype.
It’s not a tautology. Check out the work of Michael Levin (easily accessible on YouTube) for examples of non-genetic heritability.
It's genomic, technically.
Genetic would mean that genes get modified.
But there might be other ways that some traits get inherited, eg by changing the cellular environment in the sperm/egg itself which could affect the offspring while keeping the genes the same.
Maybe he's trying to go to the earliest idea of "gen-es" aka the reasons for the traits of an individual. The idea existed before the discovery of cells kernels and DNA right ? so in a way, if there are other mechanisms involved in passing traits to children, it could be termed as gen-something
Yes, that depends on the definition. Lamarck could fit into it, but he had no clue about DNA, genes and so forth; neither had Darwin. He babbled about gemmulae.
Even the definition of a gene is not very accurate. Many important sequences yield a miRNA or another RNA. Only few sequences yield a mRNA. Some "genes" are just integrated viruses/phages/transposons etc... that were modified. One of the most fascinating one was the retrovirus in regards to the mammalian placenta: https://pmc.ncbi.nlm.nih.gov/articles/PMC4332834/ but there are many more examples. We are all DNA hybrids at the end of the day. The whole species concepts makes very little sense these days, IMO. I can see the use case for eukaryotes, but it makes no sense to me for bacteria yet alone viruses.
Epigenetic inheritance is a mechanism whereby traits could be passed from one generation to the next without modifying the underlying genetic DNA. The mechanism would alter the expression of different parts of DNA.
It’s a very young field with a lot of open questions. The concept has been adopted and abused in the mainstream so you have to be careful to separate the science from the pseudoscience.
> It’s a very young field
https://en.wikipedia.org/wiki/Epigenetics#Definitions
That depends on the definition. But, if we use the modern definition, it emerged (or re-emerged) in the 1990s. It's not old, indeed, but I also would no longer call it "very young". It's soon 40 years in the modern definition, and much older if we include prior discussions.
A young field can be immature, regardless of age.
E.g., I would regard computer science as a very young field.