One more time: no, epigenetics is not Lamarckism

The standard model, so to speak, in evolutionary theory is known as the Modern Synthesis (MS), which was shaped during the 1920s, ‘30s and ‘40s by the founders of modern population genetics (Ronald Fisher, J.B.S. Haldane, and Sewall Wright) and by some other legendary names of modern biology (the geneticist Theodosius Dobzhansky, the naturalist Ernst Mayr, the paleontologist George Gaylord Simpson, the botanist Ledyard Stebbins, and the eclectic Julian Huxley). As is well known, the MS was the result of the unification between the original theory of evolution by natural selection, proposed by Charles Darwin and Alfred Russel Wallace in 1858, and the then emerging discipline of genetics, resulting from the re-discovery of the work of Gregor Mendel.

The MS marked the death knell of Lamarckism, an obscure and confused set of ideas arching all the way back to the 18th century, and proposed by Jean-Baptiste de Lamarck. Lamarck, obviously writing in pre-Darwinian as well as pre-Mendelian terms, proposed two fundamental concepts: (i) that living organisms are somehow capable of positively (we would say, adaptively) react to changes in the external environment, through some sort of internal vital impulse; and (ii) that the new traits resulting from the action of this force could be passed from one generation to the other. At the least, that’s the most plausible interpretation of the rather obscure and unclear stuff Lamarck actually wrote. (Note that almost nobody writing today — myself included — has actually read Lamarck, in the original 18th century French. I have read parts of his work in English, and spoken to a couple of people who are actually familiar with the original.)

But Lamarckism has an uncanny ability to be the zombie of evolutionary biology: no matter how many times one thinks he has killed it, it keeps coming back and wreak havoc. This has happened again in recent years because of the emerging field of epigenetic studies, particularly epigenetic inheritance. Epi-genetic literally means “above” or “beyond” the gene, and it refers to non-genetic phenomena that take place inside living cells and that alter organismal development. Epigenetic effects have been known for decades, are well studied, for instance, in the field of cancer biology, and are entirely uncontroversial.

What is controversial, however, is the subset of epigenetic phenomena that appear to be heritable from one generation to the next. Initial reports of epigenetic inheritance, decades ago, where greeted with skepticism by the scientific community, precisely because they “smelled” rather too suspiciously of Lamarckism.

By now, overwhelming scientific evidence of the reality of epigenetic inheritance is available, and the concept is one of the pillars of the Extended Evolutionary Synthesis (EES), the updated version of the MS that is taking shape and to which I made modest contributions — including by way of experimental studies of epigenetic inheritance.

Epigenetic inheritance, however, has nothing to do with Lamarckism, as the similarity between the two ideas is only superficial, and can be deeply misleading. Yet, plenty of professional biologists keep falling for it, sometimes writing very confused and entirely unhelpful articles for the general public. That’s what happened recently in the usually excellent Aeon magazine, which published “On epigenetics: we need both Darwin’s and Lamarck’s theories,” by Washington State University’s Michael Skinner.

Do we really need both Darwin and Lamarck? Hello no, we don’t, and it’s time to stop repeating such ill-informed nonsense. To see why, let me tell you a bit more about epigenetic effects.

Let’s take the most commonly studied class of epigenetic phenomena: DNA methylation. In many organisms (though it is far from clear just how frequent this phenomenon is) DNA strands inside cells are “marked” by a number of simple chemical molecules, known as methyl groups, which act as signals for certain proteins to ignore a particular sequence of DNA, which thus is not transcribed into RNA. As a result, that gene does not produce a protein, and hence has no phenotypic effect, until the methyl group is removed and the cellular machinery receives the okay to proceed with transcription.

In other words, methyl groups, which are themselves placed and erased by proteins (in turn, obviously, encoded by genes), act as regulators or modulators of gene expression. The specific pattern of methylation varies from cell lineage to cell lineage during development, and it is a major mechanism through which living organisms generate different cell types (say, muscles vs bones) in different places and at different times. When methylation goes astray, for instance, a given cell may lose the brakes that preclude uncontrolled cell division, and a cancer is born.

Moreover — and here is the real kicker as far as evolution is concerned — in some (but by all means not all) organisms, epigenetic mechanisms have two additional properties: (i) they can be modified by environmental effects, and (ii) they are heritable. An example of (i) is the alteration in methylation patterns (and hence, remember, in gene expression) when the organism is exposed to an external stress, such as high temperatures, or starvation. The extent to which (ii) occurs is still debated, with many confirmed examples from plants and insects, and a few tantalizing ones from mammals. (But we also have plenty of instances of organisms where the methylation pattern is automatically reset every generation, which means that no alteration induced by the environment is actually transmitted to the next generation.)

Superficially, (i) and (ii) sound like Lamarckism: we have an internally generated response of the organism to an external change, as well as a mechanism of inheritance of the induced traits. But the analogy is, in fact, only superficial. First, because environmentally-triggered epigenetic changes are not inherently adaptive, that is, they are not necessarily good for the organism. Rather, they are just like standard mutations of DNA sequences (which can also be induced by external factors, such as temperature, or radiation). Indeed, biologists refer to changes in epigenetic factors as “epi-mutations,” in direct analogy with genetic mutations. Remember, by contrast, that Lamarck thought that living organisms are capable of responding positively to alterations in the external environment. The standard example is the elongation of the neck in giraffes, allegedly to counter the fact that the leaves they feed on got higher and higher up the trees. (This may not be the actual reason why giraffes have long necks, by the way.)

Second, what is inherited is not the phenotypic change — as Lamarck thought — but rather the methylation pattern (or whatever other epigenetic mechanism is at play, there are several). This is, again, directly analogous to genetic mutations, where what is inherited is the information encoded in the genes, not the phenotypic outcomes that result from the action of such genes.

In other words, epigenetic inheritance should be properly treated as an additional layer (or, more precisely, set of layers) of information that is sensitive to environmental changes and passed from one generation to another. Additional, that is, to the standard channel of genetic inheritance, but not qualitatively different from it. Eva Jablonka — who unfortunately herself has often flirted with the L-word — correctly labelled this phenomenon in her book with Marion Lamb, Evolution in Four Dimensions. Evolution is then made possible by four channels of inheritance, acting partially independently and partially in reciprocal feedback loops: genetic, epigenetic, behavioral and symbolic (i.e., language).

In agreement with what I just explained, many of Skinner’s own examples in the Aeon article are of maladaptive epigenetic changes. For instance, he writes:

“Findings published by my group in Science in 2005 showed the ability of environmental chemicals to promote inheritance of disease in rats through three generations, to great-grand offspring and beyond, in the absence of any continued exposures. … An example is when Graham Burdge and his team at the University of Southampton in the United Kingdom reported that excessive nutrition in rats created epigenetically induced metabolic abnormalities three generations out. … A number of studies have indicated that environmental stress can promote epigenetic alterations that are transmitted to and induce pathologies in subsequent generations. … A recent study by Gerlinde Metz and her colleagues at the University of Lethbridge in Canada demonstrated that restraining pregnant rats or, alternatively, forcing them to swim, produced epigenetic damage that put newborns at risk. … Several studies now support the role of environmental stress in promoting the epigenetic transgenerational inheritance of disease.”

Right, so none of these examples would be recognized by Lamarck as an instance of what he was talking about. What is going on is fascinating, but it is in a sense not that different from the standard genetic story: cells encode information for the development of the organism; this information is inherited, but can be altered by the environment; the alterations that are — by chance — adaptive are retained by natural selection, while the rest are eliminated from the population. This is pure Darwinian natural selection at work. Indeed, biologists have understood for some time now that the Darwinian theory is neutral with respect to the specific mechanisms of inheritance: natural selection works regardless of which underlying mechanisms generate the phenotype variation that is being selected, and regardless of how those same mechanisms assure that the pertinent information gets passed from one generation to the next.

So, no, we don’t need Darwinism and Lamarckism, we just need Darwinism, to which the MS added a lot of mechanisms and theoretical understanding back in the 1920s-40s, and to which the EES is adding even more now.

Skinner sees himself as nothing less than the proponent of a new theory of evolution, which he summarizes in a diagram (fig. 2 of his Aeon piece), and that he grandly refers to as the “Unified Theory of Evolution.” He seems blissfully unaware that lots of people have already worked out a new theory — the EES — and that Lamarckism just doesn’t enter into it.

Skinner even fancies himself as triggering a “paradigm shift” in evolutionary biology — referring to the famous account of how science makes progress, proposed back in the ‘60s by Thomas Kuhn (and largely rejected by modern philosophers of science, who Skinner, evidently, has not read). Indeed, I have published a detailed account showing why evolutionary biology has never actually seen, and likely will never see, anything resembling a paradigm shift.

I’m picking on Skinner not because he is the only one writing such things, but because his article is the most recent, highly visible, example of this sort of misunderstanding of evolution on the part of some scientists, a misunderstanding that in turns leads to misinformation of the public. A public, one might add, that is already skeptical and confused about evolution in particular and science in general. We scientists and science popularizers really ought — morally — to do much better than this.

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37 thoughts on “One more time: no, epigenetics is not Lamarckism

  1. Thomas Jones

    Thank you for this OP. My ignorance of the subject is profound, but your essays on it are always helpful, even though my grasp of the subject remains rudimentary at best.

    It so happens that I read the Skinner piece in Aeon and remember wondering what you might think of it since I lack the background to evaluate it.

    One sentence in your OP today caught my attention, and my mind paused on it and added a qualifier to your wording: “. . . epigenetic inheritance . . . is sensitive to environmental changes and passed [but not invariably so] from one generation to another.”

    Would this addition be in keeping with your intent here, or have I misinterpreted it? I guess what I’m asking is related to your points (i) and (ii) of these additional properties of epigenetic mechanisms. Am I correct in my reading that (ii) doesn’t necessarily follow (i) in all cases?

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  2. Pingback: Is Lamarkism Really Dead? | Psybertron Asks

  3. Mark H Martens

    On showing a model of ‘the Origins and nature of life’ to a guy called Harold Morowitcz a few years back, he said to me; “It sounds Lamarckian.” In the moment I could not parse out what he meant, only later did I do a wikipedia review of ‘Lamarckism’ realized that he had meant it as a put-down.

    Why?

    Because it allowed him to ‘dismiss this amateur theory’ I suppose without needing to properly analyze the mechanisms and content any further. Experience with socializing new models has shown me that this is how many ‘experts in the current paradigm’ work. (It looks like Kuhn was on point about Academia here). The new model of cognition explains it thus; “Other models of understanding are chronically marginalised by experts in the current paradigm.” (Giovanni’s rule, I call it.)

    Anyway, thinking more about the model later, though I knew nothing of the epigenetics research you refer to above, I realized that among the mechanisms I showed was a process that could indeed be characterized as ‘effectively Lamarckian’. At least, it DOES meet this process description…
    (i) that living organisms are somehow capable of positively (we would say, adaptively) react to changes in the external environment, through some sort of internal vital impulse; and
    (ii) that the new traits resulting from the action of this force could be passed from one generation to the other.

    I understand everything you refer to Massimo, and concede your sound thinking. But EES will NOT suffice, and new models ARE needed. Especially, a better characterization of the mechanics of evolution IS called for.

    Mark Martens

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  4. Massimo Post author

    Thomas,

    Right, (ii), meaning inheritance, doesn’t necessarily follow (i), meaning environmental effects on epigenetic factors. Indeed, (i) is far more common than the combination of (ii), because it happens all the time during development.

    Mark,

    “But EES will NOT suffice, and new models ARE needed. Especially, a better characterization of the mechanics of evolution IS called for.”

    Why?

    Liked by 1 person

  5. synred

    Hi Massimo,

    Could it be that the tendency to pass on certain traits via epigenetics could be selected for?

    E.g., starvation. It might be that passing on a trait for high efficiency use of calories for of few generations after periods of famine might be advantageous if famines tended to last a few generations (in most cases).

    Of course that most epi-inheritance seems to be bad argues against this, but it seemspossible mechanism w/o invoking vitalism.

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  6. SocraticGadfly

    Isn’t part of EES, by definition, working on advancing understanding of the mechanics of evolution in places where the “traditional neo-Darwinian synthesis” has been found wanting in some particulars, though, as far as we know, NOT in the big picture?

    That’s kind of my understanding, Massimo, re Mark’s statement, and that some people have recognized that need ever since Margulis et al showed there was some reality to symbiosis.

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  7. Massimo Post author

    Synred,

    “Could it be that the tendency to pass on certain traits via epigenetics could be selected for?”

    Yes, but that’s not difference from the genetic “channel.” In both cases the underlying variation is random (not adaptive, as posited by Lamarck), and selection sifts the good from the bad.

    Liked by 1 person

  8. SocraticGadfly

    Massimo, regarding your answer to Cousin Arthur, in cases like epigenetically heritable tendencies, say, for example obesity for a variety of reasons (such as the Dutch Hongerwinter) is it fair to say that at times, what is “adaptable” genetically and what is “adaptable” epigenetically, if not in a full clash, at least don’t fully square up?

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  9. brodix

    ” Lamarck, obviously writing in pre-Darwinian as well as pre-Mendelian terms, proposed two fundamental concepts: (i) that living organisms are somehow capable of positively (we would say, adaptively) react to changes in the external environment, through some sort of internal vital impulse; and (ii) that the new traits resulting from the action of this force could be passed from one generation to the other.”

    If this guy was writing this in the 18th century, he might well have been wrong, but he certainly deserves a little respect for a point of view, from a level of ignorance, which might well be worth considering in context.

    Think of it as projecting conscious intentionality on the genes, which given they are biologically vital, isn’t entirely illogical. As social creatures, we adapt positively to our environment and attempt to pass these lessons onto our prodigy. Is this entirely emergent behavior, or are there biological precedents? Obviously we keep learning.

    It seems as much a political issue within the field, as anything, where any hint of intentionality is assumed to be theological. Yet even theology is a projection of conscious intention. Aka, anthropomorphism. Which is possibly as illogical being applied to natural selection, as it is to the universe, but it is a fact that our conscious awareness and the intentions it manifests are the lens through with all people view everything and hints of it cannot be erased. There is no “view from nowhere,” irrespective of the presumptions of the scientific establishment.

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  10. synred

    Is it possible the ‘the Midnight Toad’ experiments (apart from somebody inking the pads) are an epigenetic effect. The gene for ‘pads’ was there in toad ancestors, so may be it got turned off epi-genetically when they moved to dry land and then turned back on when forced back into water by Krammer .

    Could it be normal evolution by selection, but a faster — not having to wait around for a mutation to show up, but just remove the epi-genetic factor suppressing pad growth.

    https://www.amazon.com/Case-Midwife-Toad-Arthur-Koestler/dp/1939438454

    I read this book a long time ago and don’t remember it that well.

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  11. Massimo Post author

    Socratic,

    “is it fair to say that at times, what is “adaptable” genetically and what is “adaptable” epigenetically, if not in a full clash, at least don’t fully square up?”

    Yes. That’s why the epigenetic inheritance channel is important to the EES: it is distinct from the genetic one — though it interacts with it — and may therefore yield sometimes contrasting and sometimes boosting outcomes.

    Brodix,

    “Think of it as projecting conscious intentionality on the genes, which given they are biologically vital, isn’t entirely illogical”

    Actually, yes, it is entirely illogical, given what we known of genes, epigenes, and the like.

    “It seems as much a political issue within the field, as anything, where any hint of intentionality is assumed to be theological”

    I wrote in the past of the difference between teleology (not acceptable within science) and teleonomy (perfectly understood within biology). So no, this isn’t political, it’s philosophical.

    Synred,

    Yes, the infamous midnight toad experiments may have been early evidence of epigenetic inheritance, but they are permanently marred by the demonstrated fraud perpetrated by the author.

    “Could it be normal evolution by selection, but a faster — not having to wait around for a mutation to show up, but just remove the epi-genetic factor suppressing pad growth”

    Yes, another reason epigenetic inhertance is relevant to the EES is that, although often its effects last only a few generations, it is faster and more responsive than the genetic channel (because epimutations are far more common than genetic mutations). So the two may contribute at different scales of evolutionary response.

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  12. SocraticGadfly

    OK, Massimo, you made me want to ask about something else.

    Your “different clocks” remind me of mitochondrial DNA and that it has a different evolution rate than nuclear DNA. Is there any such thing as mitochondrial epigenetics?

    Liked by 1 person

  13. synred

    There are people (Koestler) who think/thought the fraud might have be perpetrated by somebody else.(e.g., a Hostile Nazi lab assistant ?)..

    It might be worthwhile to repeat the experiment with modern tools. I gather there were attempts, but they didn’t get funded or something.

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  14. synred

    Yes, another reason epigenetic inheritance is relevant

    Such things might occur in other similar cases, e.g., blind cave fish. Say say set up a tank where a light indicates where the ‘feeding station’ is placed and move that about … see if eyes get turned back on in a few generations … as a fish born w/o the epi-factor suppressing eyes might have a big advantage …

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  15. Mark H Martens

    Hey Massimo, regarding this matter:

    [“But EES will NOT suffice, and new models ARE needed. Especially, a better characterization of the mechanics of evolution IS called for.”
    Why?]

    Ok, I remember a youtube video of Christopher Hitchens who said to some Fox News talk jockey (Sean Hannity I think it was),… “Sean, you come across like a guy who has paid no attention to the arguments AGAINST his position.”

    Now unless you are claiming to be a Fox news reporter, I have to assume you already know the answer to that question. Probably better than I. For example, I read a book called ‘What Darwin got wrong.’ Can’t remember the Guy’s name, but you probably know it. Princeton dude. Anyway, I could see that some of his arguments were persuasive.

    However none of that mattered to me, I knew new models were called for,
    not because I was an expert on the EES, nor because I discovered persuasive exceptions to it,
    but
    because I found new models, without exceptions.
    And because they highlight the limitations of the current paradigm.

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  16. brodix

    Massimo,

    “Actually, yes, it is entirely illogical, given what we known of genes, epigenes, and the like.”

    The point isn’t what we know today, but what was known in Lamarck’s time. We acquire knowledge by projecting what we do know, on what we don’t know and then calibrating the fit. Even theism was a theory, before it was a religion.

    Which doesn’t mean I’m advocating theism. I’m the one who keeps pointing out it is an example of platonism, where the ideal is presumed to be an absolute.

    What do we know, if not ourselves and so it makes sense to first project ourselves, aka anthropomorphism, onto other aspects of nature and see what fits and what doesn’t.

    When we don’t understand the process is when we just take the products for granted, like some brand name and assume they makes us wise. There might well be ideas today that are dogma, but eventually will prove inadequate. This doesn’t mean they are wrong, so much as insufficient. It’s like the Ford Model T isn’t wrong, but it is insufficient for today’s highways.

    Just as today’s cars wouldn’t exist without those earlier models, so too wouldn’t our intellectual tool box of today exist, without first having used those earlier concepts.

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  17. Thomas Jones

    Mark, that last comment strikes me as puerile snark. A simple query on the book indicates that it was roundly criticized after its publication in 2010. Any reader here can query it. And I’m not sure why you single it out as supporting whatever point it is you’re trying to make.

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  18. davidlduffy

    Out of many examples now published, this one is quite interesting because it may well apply to human disease risk:

    http://www.cell.com/cell-metabolism/fulltext/S1550-4131(15)00275-2

    Inbred rats (so there are no genetic changes from generation to generation) were underfed for 50 generations – the last generation are smaller at birth and more susceptible to diabetes. When returned to a normal diet for two generations, their metabolisms remain altered – there are epigenetic changes around important genes like that for insulin that persist across generations. But are the epigenetic changes transmitted via the germline? Not necessarily, because the epigenetic programming of the fetus can happen via changes in the uterine environment eg glucose in the maternal circulation, size of the uterus and pelvis restricting intrauterine growth. This kind of thing is important to the arguments about “thrifty genotype” – a traditional genetic hypothesis about risk of diabetes etc in India and Melanesia, and the “thrifty phenotype” explanation, where such risk is purely environmental, although transmitted through families.

    In the case of imprinting (different effects of an allele depending on the parent of origin, also epigenetic), we do know how the methylation marks are transmitted intergenerationally, and most here would know about how this fits in “sex wars”.

    And an adequate amount of dietary folic acid is required to allow DNA methylation to occur, so starvation may lead to an inability to mark DNA. Again, this is very interesting biology, but doesn’t offer much in the way of a global role in evolution.

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