Do you know about epigenetics?

I didn’t until recently, and it is important. But please let me know if this is not news!
Epigenetics is concerned with maternal characteristics acquired from the environment but passed on, contra Darwin. That is, some characteristics aquired by a woman can be inherited by later generations. (but see comment # 4)

Components of the mechanism whereby the environment can so change your DNA’s expression are possessed only by women, or so it is said. I haven’t yet looked to see if anyone working in the area has raised the question of the intersexed.

One reason it is important is what it means for a number of topics of concern to feminists. For example, violence toward a woman can affect later generations, ones yet to be born. Similarly, starvation can also alter one’s DNA; the effects of (attempted) genocide may be visited on later generations. We probably are far from the end to new effects from the holocaust. The possible negative effects of rape may be worse than we now know.

I have seen various estimate of how many generations can be affected; apparently it may be 5. I have not seen yet a good account of the characteristics passed on, but it looks as though at least some unhealthful characteristics should be on the list. If a trauma causes a woman high blood pressure, her children may be born with a tendency to high blood pressure and/ be vulnerable to stress.

Some references: some references accessible to non-scientists:

http://www.britannica.com/blogs/2009/02/the-rebirth-of-lamarckism-the-rise-of-epigenetics/

29 thoughts on “Do you know about epigenetics?

  1. “… affectionate mothering alters the expression of genes…”

    What doesn’t in a developing mammal? My dog nursed a roommate’s kittens who had been prematurely weened. The kittens and Max bonded. Max would go out when the sun started coming down, stand on the front porch, and then the kittens would climb down from the tree in our front yard and go inside with their “mother”.

    Of course, a male dog couldn’t function as a wet nurse, but human males can hold bottles and hold kittens close to them. This is a well-known phenomenon, yes?

    Humans have a long childhood. The process of imprinting or bonding or attaching is a process of being a trustworthy and reliable enough caregiver for an infant, and is a neurological process in which the relationship between the infant and the caregiver creates the architecture that forms the basis of the infant’s ability to trust, empathize, and develop human attachments and a relatedness to other humans. I was read a neurologist’s explanation that the basic neurological processes for the young is like a series of tumblers, and the key to helping the human child develop is to realize that each child comes with its own combinations. No doubt, the expressions of genes is a vital process in development.

    I seriously doubt that men are unable to be just as successful with forming attachment as most women are. Mothers (biological or surrogate) who are sociopaths may or not bond with an infant, the temperament of the child and other factors may help or hinder in the face of an unreliable and untrustworthy adult caregiver. And before I accept another “mommy magic” supposition (epigenetic or whatnot), I’m going to have to see a whole lot more than a couple of articles.

  2. Not really news, although I doubt many Americans have heard about it. Most epigenetic effects are reset at reproduction, but some can indeed be inherited. There is a little book called “Epigenetics” that will explain it. But yes, some acquired characteristics can be inherited through epigenetics. We have known about short-term gene switching for a few decades, but long-term gene regulation through alterations to the genome (but not the genes themseves) is a relatively recent discovery. Be carefuly, though: just because a trait is partly or even largely determined by genetic or epigenetic factors, that doesn’t mean that the trait cannot be altered in a given individual. Genetic or epigenetic is not the same thing as permanent and immutable.

  3. Ruth makes an important point and I would add that it would be worth being careful about the claim that “components of the mechanism…are possessed only by women.” It’s true that the majority of inheritable epigenetic effects come from the ovum, but there is at least some evidence that limited components of a father’s epigenome can also be inheritable (see http://www.ncbi.nlm.nih.gov/pubmed/20448473). We all, no matter our chromosomes (XX, XY, XXY etc.), have epigenetic processes occurring – it is just that there are differences in heritability of those traits because of the different development and contributions of the ovum and sperm. Hope that helps!

  4. Also, epigenetic effects are not limited to in utero organisms. Iirc, boys who are underfed at pre-puberty have permanently lowered risks for cardiovascular disease because of epigenetic changes. Most EG effects appear early on, I think. The Dutch Famine study is probably the most famous example of that (1944?).

  5. I just took a course on Coursera in epigenetics, and these comments from the professor are worth repeating:

    “One important thing to remember is that extremely rarely are epigenetic marks passed between generations. We talk about this a lot in week 5, but essentially we only know for sure of cases in mice, none yet proven in humans.

    … Even for those epigenetic marks that appear to be heritable in mice, these events aren’t acquired after birth, but rather established early in embryogenesis. The debate has been sparked again since we now know that the environment e.g. diet, can alter epigenetic makeup, but again it makes has a very small effect, and only during critical windows in time when epigenetic marks are being established in utero.”

    Echoing this quote and some comments above, most of epigenetics is not about traits that are passed between generations. It’s about features of gene expression that are inherited when a cell divides (e.g. when your skin cells give rise to other skin cells rather than to lung cells), but these features are mostly “cleared” for a new generation.

  6. I’m no expert here, but I think it is important to distinguish what affects gene expression and what affects the DNA itself. My understanding is that epigenetics is focused on the non-DNA stuff in a cell (or organism?) that accompanies DNA and affects gene expression without changing the DNA. The original post was a bit ambiguous on this. (Though it is also my sense that the term ‘epigenetics’ is used in different ways and is somewhat controversial, so I may be only sensitive to one usage.)

  7. Waddington coined the term in 1942. There has been much debate over what it refers to. Early on, roughly, it was about anything that was not DNA that impacted development. Then our understanding of gene expression got much more more sophisticated and complicated. There are still differences in understanding of the term, but for, those folks who work in genetics and genomics especially, it pretty much refers to stuff that happens to DNA that do not influence the order of nucleotides, that impact its expression, and that can be passed from one cellular generation to the next. Things get more complicated depending on whether we are thinking about single celled versus multicellular organisms, and how those organisms reproduce. For creatures like us, considerations of epigenetic changes that may happen in gametes are very cool for many reasons, one of which is that they challenge how we think about heritability and evolution. Wikipedia is not bad on this topic, if folks are looking for a starting place (a good group of references). Also–look to Science and Nature for discussion pieces.

    Be careful of linking our understanding of epigenetics to human sex and gender. It is useful to think of it at the level of cell division. Admittedly, ova are very cool cells, and epigenetic changes there are cool in interesting evolutionary ways. But, there are epigenetics of single-celled organisms, asexual organisms and cells that are not gametes or on their way to becoming gametes.

  8. @7: “most of epigenetics is not about traits that are passed between generations”

    Yes and no. If the changed gene expression pathways produce behavior that effects the ontogenesis of the next generation in such a way as to reliably produce altered gene expression that produces behavior that …, then I think you can responsibly talk about inherited acquired traits. It just takes a developmental systems view such that reliably reproduced environments are part of the developmental system. That’s how I would read Oyama, Griifiths and Gray, Jablonka and Lamb, and so on. Of course that’s not a non-controversial position. Pigliucci and Muller, The Extended Synthesis, take a sober look at all this.

  9. I recommend the article in Nature that John has provided a link to. The idea that the changes epigenetics studies just concern cellular changes has had a strong grip on a part of the literature, but it is increasingly recognized that the effects can be passed on to later generations. I think John’s article explains this clearly.

    That the range of the effects is quite wide is clear from this article. The abstract also tells us:

    Epigenetics is one of the most scientifically important, and legally and ethically significant, cutting-edge subjects of scientific discovery. Epigenetics link environmental and genetic influences on the traits and characteristics of an individual, and new discoveries reveal that a large range of environmental, dietary, behavioral, and medical experiences can significantly affect the future development and health of an individual and their offspring. This article describes and analyzes the ethical and legal implications of these new scientific findings.

    I have noticed that every article talks about maternal features. I’m afraid my well-practiced apriori hypothesis generating mechanism went into action before I noticed it. I don’t know why the restriction is there. Given the history of citing the mother as cause, this bears further investigation.

    It is extremely disheartening to find out how little we know about major scourges. The idea that present environmantal features may account for traits of later generations is very, very exciting. E.g., a psychiatrist told me last week that he thinks our understanding of the genesis of mental illness is going to be radically revised by epigenetics. The fact that groups’ cancer profile changes when they come to Western counties may be explained in an enriching way.

  10. Thanks to every one for the great and useful comments!

    It occurs to me that epigenetics also counts against the creationist types who maintain that scientists working on the theory of evolution opposes changes in its ‘doctrines’ as much as, or even more than, religions do.

  11. DC: i’m concerned your professor may not be entirely up to date.

    Has anyone studied the time it takes for a new approach to make its way into undergrad courses? Given we are looking at a very recent change, we seem to have a great topic for a thesis. Ot 2 or 3. It might be politically extremely useful in a country where so many seem to think research is pretty useless. Here the potential for important discoveries is quite clear.

  12. “Doting mothers have prudish daughters, whereas the daughters of inattentive rats cavort around like mini Mae Wests.”

    Really? The neurological processes of attachment can explain this. It’s one thing to look at the processes of attachment on a chemical/biological scale, and another thing entirely to project the Virgin/Whore dichotomy onto rats, which, in a bizarre way, reinforces this dichotomy for women.

    “… a psychiatrist told me last week that he thinks our understanding of the genesis of mental illness is going to be radically revised by epigenetics…”

    That’s what bio-bio-bio psychiatrists do. There is always the next thing that will finally prove something, something… so that the drugs can work like a guided missile and all other factors of human mind and mood and the complexities of being a social animal can be ignored. A field of medicine that doesn’t require itself to use it’s medical degree to test for medical conditions with psychiatric symptoms before giving a psychiatric diagnosis, and that has a ridiculously unscientific taxonony is one that should not be given too much of the benefit of the doubt, especially when it comes to predicting the future.

    http://taxonpsych.blogspot.com/2013/06/descriptive-validity-of-dsm-5.html?updated-min=2013-01-01T00:00:00-08:00&updated-max=2014-01-01T00:00:00-08:00&max-results=50

    Say a woman has been diagnosed with “post-partum depression” and is prescribed an antidepressant that— paradoxically enough— causes anhedonia. So she’s prescribed a series of cocktails of psyche drugs in different dosages and different combinations, but nothing works. So she is now “treatment resistant”. Meanwhile, she doesn’t have the energy to be responsive enough to her infant, but has enough to hate herself for failing as a mother, and as a woman. She is alone with the baby all day and has little to no social support. And she is still anemic, but believes that her primary problem is being mentally ill and unable to be responsive to medication. And no one can scientifically tell her exactly what effects a drug has on her brain, much less a combination of drugs.

    Might this have something to do with epigenetics? Perhaps a lot, but without a great deal of work teasing apart causes and effects on a chemical/biological level before assuming a causal relationship or even a category of suffering we have good and bad rats for models with all the patriarchal douchebaggery we could ever want.

  13. SGSterrett – i thought the contrast between Darwin and Lamarck on the inheritability of acquired traits was very standard. Still, one might think there’s still a lot of room for questioning my aside. I’d love to know what you have in mind.

  14. Felonious, let me just say that some of your unqualified generalizations seem questionable. And the use of conjectured examples provides almost no support for claims about actual practice.

    I think actually that a lot of psycho-theory is politically suspect, and fails to give us helpful guidelines for treating mental suffering. But that’s not really the topic here.

  15. Hi, Dr. Jacobson. At times it seems your posts are coming from the mind of your avatar? I think it’s because the cat is looking down toward the text.

    I, too, am interested in your wondering about “has anyone studied the time it takes for a new approach to make its way into undergrad courses?” Hopefully someone will chime in. I have always had strong opinions about that (it doesn’t seem the new approach does make its way, very often) but unfortunately no credibility or data to support those opinions. Also looking forward to Dr. Sterrett posting again since I had roughly the same idea you do.

  16. Hi, Anne,

    Certainly Darwin was concerned to emphasize the difference between his own theory of the preservation of natural selection and lamarck’s theory. One reason Darwin wanted to emphasize the contrast was because there were scientists who did not distinguish natural selection from Lamarck’s theory. In particular, he was chagrined that Lyell, whose works he admired so much and whom he expected to appreciate his theory of natural selection, did not clearly distinguish natural selection from Lamarck’s. However — Darwin didn’t think that natural selection was the _only_ means by which changes occurred.

    As to what I have in mind in saying I did not think that epigenetics was “contra Darwin.” I am thinking of Darwin’s discussion of the effect of what he calls “conditions of life” in _Origin of Species_ in his discussions of the difference between wild and domesticated versions of the same species. It is also discussed in more detail in his _Variation of Plants and Animals under Domestication_. Of course Darwin did not have the notion of gene, genome, or DNA, but in these works by Darwin, that kind of change would be referred to as a change in the reproductive system of the organism.

    There are many passages showing Darwin recognized that there were direct effects on an organism, and that they could possibly affect offspring, but he wanted to discourage putting much weight on it as the sole explanation for how well adapted plants and animals are to their environments. And he repeatedly stressed our ignorance on the matter. Here is one such passage from chapter V (“of The Origin; there are many others:

    “When a variation is of the slightest use to a being, we cannot tell how much of it to attribute to the accumulative action of natural selection, and how much to the conditions of life. Thus, it is well known to furriers that animals of the same species have thicker and better fur the more severe the climate is under which they have lived; but who can tell how much of this difference may be due to the warmest-clad individuals having been favoured and preserved during many generations, and how much to the direct action of the severe climate? for it would appear that climate has some direct action on the hair of our domestic quadrupeds.”

  17. P.S.: I realize that the quote I gave in the previous post did not specifically mention heritability, but you will find that Darwin does allow that such changes might be heritable. In the terminology of the Origin, this would be called the indirect effect of the conditions of life on the reproductive system. Chapters I and V discuss it. Quotes taken out of context do not do it justice, as his reasoning is subtle and his distinctions are many.

  18. The first paragraph of my post in comment 21. was the mangled, unedited version. Sorry, the first paragraph should have read:

    “Certainly Darwin was concerned to emphasize the difference between his theory of natural selection and Lamarck’s theory. One reason Darwin wanted to emphasize the contrast was because there were scientists who did not distinguish natural selection from Lamarck’s theory. In particular, he was chagrined that Lyell, whose works he admired so much and whom he expected to appreciate his theory of natural selection, did not clearly distinguish what he was attributing to natural selection from Lamarck’s account. However — Darwin didn’t think that natural selection was the _only_ means by which adaptation was to be explained.”

  19. Thanks Susan, I’ll have a good look at the texts.

    I was thinking that there are implication for creationists views of Darwinism, but a quick look at the web shows that epigenetics is beloved by a number of alternative medicine people.

    It looks like there is very important stuff to be said and it might be taken up by anyone wanting to be more of a public intellectual.

  20. Yes, I think so. Evelyn Fox Keller has been talking about it for a number of years, though there has of course been a lot of resistance in some circles.

  21. In Philosophy of Biology circles, the standard “go to” text about this subject is Eva Jablonka and Marion J. Lamb’s Epigenetic Inheritance and Evolution – the Lamarckian Dimension, Oxford University Press, 1995. (I assume this is what John P. was referring to.) Although this book is now 20 years old, it was and is extremely eye opening for many people. As Susan S. intimates above, lots of bits and pieces was known about epigenetic inheritance already, but a very interesting and powerful case was put together by Jablonka and Lamb.

  22. Some excellent up-to-date scientific assessments can be found at http://www.scribd.com/doc/137312200/Transgenerational-epigenetic-inheritance-how-important-is-it. See especially Marcus Pembrey’s comments–he’s done some very interesting work on this, and has compelling evidence for paternal (and more bizarrely, grand-paternal) effects. The comments tend to be extremely cautious, reflecting the point alluded to in the discussion, that this is highly contentious stuff, and strongly resisted by evolutionists who think it smacks of Lamarckianism (the most inviolable taboo in contemporary biology). Whether epigenetic inheritance should count as Lamarckian is another equally contentious issue. But there’s little doubt that it happens, probably quite a bit.

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