Wednesday, June 17, 2015

Remembrance of things past--in your genes? Part III: Was Lamarck so laughable?

A favorite sport of those holding to strict Darwinian views (to the extent they understand Darwin),  is to ridicule Jean Baptiste de Lamarck (1744-1829), he of the stretchy giraffe neck.

Lamarck has gotten a very bad name and at least partly undeservedly.  As are we all, he was a product of his time, his academic environment, and the knowledge then available.  He was apparently a quirky personality and got crosswise with other powerful French biologists, notably Georges Cuvier.  For various reasons it became important for Darwinians to distance themselves from Lamarck as an important intellectual ancestor, in particular, to avoid crediting him for his insight about evolution. Intentional PR-spinning to advance Darwinians (and British over French science)?

Lamarck did his best to clarify very explicitly that he was seeking material explanations not being mystical as he is essentially accused of being.  His basic idea of the inheritance of acquired characteristics was not even that new. It was the obvious thing to infer from the data available at the time, and the idea was commonly held as far back as Hippocrates (probably classics scholars can find it elsewhere as well).

In fact, Lamarck was very clear that he wanted a strictly materialistic explanation for species evolution and diversity. This is interesting, and if it weren't for the rather smug glee with which Lamarck is so universally ridiculed by biologists (whether or not they've read his actual work or even much of Darwin's), we might not want to make the following points.  But under the circumstances, we think it's merited, especially in light of the interpretations being given to widespread reports of various sorts of epigenetic inheritance, that is, of DNA marking rather than sequence change during life.

In our two prior posts in this series (here and here), we took the usual view and stated that any suggestion that epigenetic inheritance is Lamarckian inheritance is trying too hard to be revolutionary, because epigenetic inheritance is imposed by the environment, not by some mystic inner drive on the part of the organism as Lamarck is supposed to have suggested as the cause of adaptive evolutionary change. So, as the usual view has it, even if genome marking is inherited, it is not Lamarckian.  But is that actually so?

"Laws of Nature": who was right?
As we use the term, a Law of Nature is a concept that grew out of the so-called Enlightenment period in European culture history beginning around the mid-1600s.  Darwin's view of natural selection was that it was a Law of Nature that Isaac Newton might have been proud to recognize.  In the amended introduction to the 6th edition of the Origin of Species, Darwin added a review of the history of evolutionary thinking, and there he couldn't have expressed his views better: Darwin said that Lamarck "...did the eminent service of arousing attention to the probability of all change in the organic, as well as in the inorganic world, being the result of law, and not of miraculous interposition."  (italics mine).  

But in fact Darwin was quite wrong, reflecting his own ideological commitment, not Lamarck's. This is because Lamarck said something far more important in my view than the way Darwin thought, and in fact the exact opposite. Here's a fundamental point that Newton himself made very clear, about the central characteristic of a Law of Nature: Principia in 1687: 
"Those qualities of bodies that . . . belong to all bodies on which experiments can be made should be taken as qualities of all bodies universally."
That is, if you find something to be true in a local, restricted setting or 'sample', such as dropping an apple or the orbit of the moon around the earth, the same would be true everywhere else that you didn't or couldn't study.  That was the very essence of what it meant for some phenomenon to be a 'law'.   In his books and other writings it is repeatedly crystal clear that Darwin accepted this Newtonian view: natural selection is a law of nature the way the law of gravity is.  Indeed, in the autobiography he penned for his children near the end of his life, he couldn't have been more clear, writing " that the law of natural selection has been discovered..." and "Everything in nature is the result of fixed laws.”

Lamarck was closer to Newton in time than Darwin, but what were his views about laws of nature?  I know not, but Georges Cuvier gave a scathing 'eulogy' upon Lamarck's death, a bitter attack that poisoned posterity about Lamarck's reputation, and Cuvier notes of Lamarck "He had meditated on the general laws of physics and chemistry, on the phenomena of the atmosphere, on those of living bodies, and on the origin of the globe and its revolutions."  If accurate, Lamarck shared the prevailing idea of laws of Nature with Darwin.  Yet, when it came to life, Lamarck in his book said something very cogent, that Darwin and his intellectual descendants seem not fully to realize, even to this day: 
"In dealing with nature, nothing is more dangerous than generalizations, which are nearly always founded on isolated cases: nature varies her methods so greatly that it is difficult to set bounds to them."
Lamarck wrote this basically before the widespread development of statistical thinking, but it is a fact that has still not yet been absorbed by most biologists in evolutionary or biomedical genetics. Lamarck said that when the environment changes, that change in turn induces responses in behavior of organisms. His theory was about the consequent importance of (1) habit, (2) the use and disuse of traits, (3) the inheritance of acquired characters, and (4) the very slow process of adaptive evolution. 

As Lamarck described things, organisms have ways of life that depend on their circumstances.  They seek out resources, like food, that they are able to find, and the resulting 'habits' are essentially their ways of life.  Traits that are used seem to become more important over time but traits that are not used seem to wither or disappear.  Traits acquired during life are passed down to descendants.  The process is very slow, almost unimaginably so.

None of this seems to be at all forced, invented, or strange, and in fact, Darwin adopted all of these ideas in his own way.  As noted above, the idea that one's characteristics were controlled by some sort of transmitted substance is ancient, and the idea of evolution of species was hypothesized in classical times and here and there after that.

[If you are skeptical of our take on this, given Lamarck's clown-like image (due in large part to Darwin and his pals and Cuvier), that would not be surprising.  But that image is wrong, as you can see if you check his book itself and the Introductions by two highly respected evolutionary scholars (the 1984 U of Chicago Press English translation of Lamarck's Zoological Philosophy itself with very informative introductions by Hull and Burkhardt.), or Stephen Jay Gould's The Structure of Evolutionary Theory, or Ernst Mayr's The Growth of Biological Thought.]

So, what was so laughable about Lamarck?
Lamarck is routinely sneered at because, among other things, Darwin and his colleagues were motivated essentially to claim more credit for evolutionary ideas (I'm not the first to suggest this). Lamarck was a human with all the associated failings, but his work is derided because he suggested that the very striving or habits of life caused the associated heritable changes.  By contrast, the Darwinian idea is that new variation arises randomly relative to any need it might or might not have (one can debate how clearly Darwin understood or held such a view).  

However, Lamarck was trying to explain the same phenomena as Darwin, and to do so in terms of natural, historical evolutionary processes, rather than individual events of divine creation.

In our two previous posts in this series we basically took the Darwinian view, that Lamarck was laughable and any attempt to say that epigenetic inheritance was Lamarckian was equally wrong, trying too hard to challenge standard evolutionary theory. In fact, one can argue that epigenetic inheritance really is Lamarckian, based on what he actually said rather than what Darwin said about him, and adjusting for what was known in Lamarck's time.

(1) Habit: How do epigenetic changes arise?  
They arise because of the conditions and behavior of the organism: where they live, what they eat, stresses they are exposed, etc., and how their bodies respond to those exposures.  That is, they are the effects of the habits, as one could say, of the organisms.

And such changes are obviously adaptive if they allow the organism to persist and reproduce! If epigenetic changes are important and persist, over time they will be built into the characteristics of the species. Indeed, there are means by which such traits can eventually be built into the genome in the usual DNA-sequence way (one term for this is 'genetic assimilation').  Over time, nothing strange need be involved for epigenetic changes to be wholly compatible with our understanding of evolution.

(2) What about use and disuse?
In modern theory, 'disuse' means that eventually mutational or gene-expression changes (even if due to epigenetic mechanisms) lead a function or a gene to become more degenerate--as Darwinians would say, because there's no selection pressure to maintain it or even because it's costly if not useful and selection will favor its disappearance. And 'use', of course, would mean of adaptive value.  All perfectly compatible with Darwin (and part of his own theory).

(3) What is epigenetic inheritance?  
When and/or if it occurs, it is the modification of DNA (or the contents of cells) that arises in gametes (sperm or egg) during a parent's life and is transmitted to offspring.  The modifications of interest affect gene usage and hence the traits of the organism.  That is, this is the inheritance of acquired characteristics.

(4) What about the pace of evolution?
As to time, Lamarck was every bit as clear about the slow, gradual nature of evolution.  Both stressed this, recognizing the need to avoid creationist explanations.

So many of Lamarck's basic  ideas were similar to Darwin's (again, historians, not just I, have pointed this out).  What matters is not what someone said 200 years ago.  Instead, the bottom line is that if transgenerational inheritance by way of epigenetic changes acquired during life occurs and is functionally relevant, it is basically Lamarckian, but is also just a different form of 'mutation'.  And the differential proliferation of successful inherited traits, however acquired, will be a natural form of selection.

In that sense, it is Lamarck who is being misrepresented, and whose work in this context, given his context, is not risible.  It doesn't make Lamarckism entirely 'true'; there are wildly wrong things in Lamarck (but also in Darwin).  Cuvier, himself grossly wrong about life in many ways, cruelly portrayed Lamarck as a real nut case.  Despite Lamarck's sometimes free-wheeling ideas, that is not the judgment of history, and in any case, based on what Lamarck wrote in regard to the issues here, if epigenetic inheritance does turn out to have long-term relevance, which is not yet the case in terms of current evidence, it does not in any serious way undermine Darwin. What it does do, is to undermine ideological Darwinism.  And that is a very good thing for science.


Anonymous said...

Speaking of epigenetics, there is another aspect that you did not mention. The promoters of Modern Synthesis (Fisher, Wright, Haldane, Dobzhansky) built a mathematical theory of natural selection entirely based on genes. That puzzled the embryologists, because every cell in a multi-cellular organism had the same genome and yet tissues had different properties. Waddington used the word 'epigenetic' to explain this anomaly in his 1940 articles. Unfortunately, the followers of Fisher/Wright/Haldane prevailed, and they did not abandon their core theory even after genomics era (neutral mutation).

So, now the evolutionary biologists are stuck with the same old issues of theory not being consistent with development, whereas their followers are keen on using 'epigenetic marks' to explain the anomaly. In their mind, if the genomes are different due to epigenetic marks, that takes care of the issues raised by Waddington. If you check the review article mentioned in the first post, they first started with this developmental definition of 'epigenetics' and then expanded to heredity and evolution.


Ken Weiss said...

Yes, these points are known to those who care to know them. Mayr's book essentially dismisses embryology as relevant only to reconstructing phylogeny. Bateson wrestled with how to reconcile Mendelian inheritance with development and with evolution and with repetitive structures. The Soviet scientists wanted inheritance to be Lamarckian because that jibed with Marxist thinking about improvement being possible and people's nature not being inherent and unchangeable. They viewed 'genes' (what was known at the time) as being metaphysical units that western science was basically inventing to support their worldview.

It's hard to shake these various constraints that history places even on scientists.

As to your second paragraph, I think many want to view development as about 'systems' of interacting components, in processes like Turing processes, but the challenge is to make more clear-cut sense of what 'interaction' means. At least, the problem is being confronted by many these days, if not really by the strict-reductionists.

Ken Weiss said...

I would add that there are increasing numbers of authors and papers who are rising to the defense of Lamarck. It seems that some of these may be thinking that he is vindicated by epigenetic inheritance. As I tried to point out in this series, the evidence is still mixed, especially in vertebrates and other complex animals. We should not be falling into the too-regular trap of identifying a hero and accepting more than is justified by the actual facts. After all, today's scientists should not care what some antecedent said--that's for historians.

Anonymous said...

Even without epigenetic inheritance Lamarck is gravely underrated. In Zoological Philosophy there is discussion of overpopulation, proto-life history theory, proto-competitive exclusion, vestigal organs, homologous structures, branching evolutionary pathways, geological uniformitarianism and gradualism, domestication, chimpanzees most like humans, humans imperfectly adapted to bipedalism, animal cries as precursor to speech, ecological change driving biological change, and of course developmental plasticity having a role in evolution. Lamarck deserves credit as a founder of evolutionary biology. There is an overemphasis on Darwin that dismisses predecessors (e.g. Geoffroy St. Hilaire) and turns the origin of evolutionary biology into a kind of creation myth.

Ken Weiss said...

Yes, there is a lot in Lamarck. I think his very clear description of the imperceptibly slow march of time (a clock metaphor) is as perceptive as Darwin's 'no saltations' as a recognition that otherwise spontaneous creation or instant adaptations would suggest external intervention. This clock analogy, similar to what Darwin stressed, is very clear (end of Part I of Lamarck's book).

I'll add that he did have sections referring to his principles as 'laws' so he wasn't so un-law-like as my post suggested, but I was trying to make a point.

And in that spirit, again, one can't attribute too much to Lamarck, writing in 1809 with his particular experience, just as we should honor, but not over-credit, Darwin for his interpretation of his observations a half-century later.

Anonymous said...

Sorry, but you all are obviously wrong about epigenetics. Here is a video of geneticist Greg Cochran explaining why that's so, and epigenetics is mostly a Lamarckian pseudoscience

Anne Buchanan said...

Geneticist Greg Cochran? Last I knew he was a physicist.

Ken Weiss said...

Lamarck's science was not pseudoscience, and anything that was really 'Lamarckian' would be just as much science as anything Darwinian. Lamarck was a product of his time, as was Darwin, as is Cochran (though I would have thought he'd be better described as a polemicist rather than a scientist). If the current claims about epigenetics turn out to be exaggerated or misinterpretations of data, they will be dismissed as such. If too much is being claimed (and, as we suggested in our posts, this is also possible), then so be it. But if or to the extent that these claims turn out to be accurate, it will contribute different forms of inheritance to the evolutionary repertoire. Lots of fields that claim too much can be called 'pseudoscience', and any time is awash in claims that don't turn out to be true. To say that something is 'Lamarckian' in the senses we discussed is not anything particularly objectionable, except perhaps to people who like to object to anything that isn't what they themselves have said.....

Anonymous said...

Can epigenetics explain trends like in this link: ? I think it's pretty much only darwininan evolution and genetics

Ken Weiss said...

Epigenetics can explain what it can explain. Those who claim too much will be shown to be wrong. Similarly of course, if all you see in the world is Darwin then everything will be Darwinian. The legitimate question is whether things claimed to be epigenetically inherited based on life experience can be truly transgenerational. If it is, it is, if not, then it's not.

Anonymous said...

Lamarckian epigenetics does not exist, that's been consensus in the field:

Ken Weiss said...

People seem to prefer commenting without reading. It is clearly and multiply stated in this series of posts that if transgenerational inheritance turns out to be important, then it is. We described the nature of the evidence and of the claims and in a sense of the politics of this area, but we did not say that transgenerational inheritance occurs, or doesn't occur, nor whether , if it does, it is more than a passing curiosity (if it does occur, precedent would generally suggest it will be more widespread than a single isolated instance). As to the 'consensus' of the field, that is an awful criterion, as history shows. Not all that long ago, epigenetic inheritance itself was controversial, but now it's all the rage.

Sometimes the consensus is more or less correct, but other times it is very incorrect. Science is not settled by a vote, at least in its formal description; in practice, the social politics of science, as with other areas of human affairs, consensus has more power than just that of the dispassionate evidence. In transgenerational epigenetic inheritance, there are plenty of people who think it is an important reality, or who are looking for it--even if the consensus thinks otherwise. It would only take a single important example, clearly shown, to change the consensus into a new consensus. We'll see if any of the advocates can prove their case.