Evolving Thoughts

For a long time now, I have had troubles with the use of the word “Darwinism”. Not just by creationists and antiscience advocates like IDevotees, but by scientists themselves. You routinely see press releases and book titles that declare the death or some fatal illness of Darwinism, which, in every case, their own theoretical or experimental contributions points up. It is time, I think, to lose the word entirely.

The term has a history that is itself confusing and contradictory. Let’s consider some of the things it has been used to denote:

1. Transmutation of species

1.1 Gradually (gradualism)

1.2 Rapidly (punctuated equilibrium theory)

1.3 Partially (i.e., a population)

1.4 All at once (the entire species morphing into a new species)

2. Natural selection

2.1 As a cause of adaptation

2.2 As a cause of speciation

2.3 As a cause of species stability

3. Competition and struggle

3.1 Between members of the same species

3.2 Between different species

3.3 For existence

3.4 By an act of sheer will

4. Common descent (phylogeny)

4.1 Common descent of related species

4.2 Common descent of all life

5. Neo-Darwinism

5.1 Genetic selection

5.2 Individual selection

5.3 Selfish genes

5.4 Hamiltonian inclusive fitness

5.5 Weismannian Barrier

5.6 Central Dogma of Molecular Biology

6. Opposition to religion

6.1 Atheism

6.2 Chance and accident

6.3 Rejection of Creationism

7. Social and moral nihilism

7.1 Social Darwinism

7.2 Utilitarianism

7.3 Individualism

7.4 Amoralism

7.5 Conservatism

7.6 Socialism

7.7 Racism

7.8 Unwarranted egalitarianism

7.9 Progressivism

8. Philosophical Darwinism

8.1 Population thinking

8.2 Universal Darwinism

9. Anything Darwin believed in contrast to the current writer/speaker

9.1 Inheritance of used, and disinheritance of unused, traits

9.2 Speciation by natural selection

9.3 Pangenesis

9.4 Sexual Selection

Basically, when a term has no definition, or has too many definitions, it cannot be a term capable of being defined. But there is another way the term might have some reference – as a name. That is, as the name of a historical sequence of events. And this sense has a lot more going for it, despite Gould’s and others’ denial. If something has a definition, then it has an essence, but we can see that from actual usage, “Darwinism” has no essence, but instead has a cluster of sometimes contradictory meanings, depending on the speaker and context (for example, “Darwinian” meant historical phylogenies in the context of the transformed cladism debates). But if something is a name, then it can grow, change or even lose meanings and descriptive properties over time.

As a name, “Darwinism” means basically any idea that can be said to have derived by descent, as it were, or transmission as the modern style has it, from Darwin. This enables us to include Huxley (opposed gradualism and selection as the cause of speciation), Wallace (opposed sexual selection), Weismann (opposed inheritance of characters based on parental life history), but at the same time exclude Spencer’s social theories (as they were in place largely before Darwin published) and the notion that all is basically random (since that is a view falsely ascribed to Epicurus by the theists, and is in any case not true of Darwin).

But this sense of the term means that the only meaningful way to talk about Darwinism is as a historical sequence or object, and hence it can not be defined exclusively and uniquely. For example, Haeckel’s Darwinismus was a mystical philosophy of deism, Goethe, Lamarck and Darwin all rolled into one, and the sense in which a good many critics of “Darwinism” today mean it is Haeckel’s anticlericalism against Catholicism. The claim that “Darwinism” is a historical entity is due to David Hull, and I fully agree with him, with some caveats.

Historical entities like any other evolutionary entity retain some aspects of their past. Physics uses the term “mass” today because Newton and others used it in the 17th century. We talk about “selection” because Darwin terms his process “Natural selection” 150 years ago. These are primitive notions embedded in the modern descendants, but they are not definitive sine qua nons. One can be a “Darwinian” in some sense without accepting very much of what Darwin uniquely believed, in virtue of being at the tail end of a long sequence of historical development. As a corollary, anyone who came up with the same idea, in, say, Imperial China, without knowledge of Darwin nor contributing to his ideas, is not Darwinian no matter how exactly his ideas match Darwin’s or ours.

Many scientists like to assert that they are “non-Darwinian” or “post-Darwinian” or “trans-Darwinian” in order to establish the novelty of their own views. Sometimes this occurs by asserting the truth of some view that is opposed to Darwin’s, notably Lamarck. The neo-Lamarckians of the 1880s through to the 1910s saw themselves as completing Darwin by adding into the mix a novel mechanism he rejected. But in fact the view that adult experience affected inheritance was not Lamarck’s alone, and was partially shared by Darwin, and in most other respects they were Darwinians. More recently, the work of people like Eva Jablonka on the existence and evolutionary importance of epigenetic (non-nucleotidal or nuclear) inheritance has been unfortunately termed “The Lamarckian Dimension”. Similar claims are made against neo-Darwinian ideas by developmentalists and ecologists, by cytologists and so on.

If we want a simple notion that can be given the term “Darwinian” uniquely and unambiguously, it can only mean the process of selection (natural, sexual, social, individual, group, genetic, epigenetic, whatever): the three conditions proposed by Lewontin and since elaborated for any process of selection, whether it causes stability, direction change, disruptive change or whatever. They are:

1. Phenotypic variation (that is, the traits of the entity vary from individual to individual)

2. Fitness variation for different phenotypes

3. Hereditability of fitness

As Lewontin himself said, “These three principles embody the principle of evolution by natural selection. While they hold, a population will undergo evolutionary change.” But this is not quite right, either, because selection can be, and often is, a process that causes no change, so “Darwinian” evolution has to include stasis.

When people say that, as they sometimes do, selection equals evolution, they are equivocating on both terms. R. A. Fisher knew this very well, and so he began his classic book in 1930, The Genetical Theory of Natural Selection, with the sentence “Evolution is not Natural Selection”. And as the subsequent debates between Fisher and Wright indicated, some evolution is not caused by natural selection, and some selection does not cause evolution.

So given these caveats, “Darwinian” can only mean “natural selection”, which is historically problematic because Darwin’s real originality lay not in that notion, but in the recognition that life diversified in a historical tree, which we call Common Descent” or “Phylogeny”. Others had proposed selection-like mechanisms (usually of stability, but a couple had said it caused change), but only Darwin recognised that the Linnaean system of classifying “groups within groups” was more than a convenience or logical structure, but a historical outcome.

So let’s retire the term altogether. Replacement terms are easy to come by – phylogeny, selection, drift, mutation, germline inheritance, social biology (sociobiology) and so on. And hence when a critic has trouble with one notion, this will impede the rapid slide to rejection of it all.

Comments

  1. #1 Kapitano
    April 15, 2007

    I recall a similar argument about the need to rebrand Marxism. The term “Marxist” has been used to denote:

    * Whatever Karl Marx (or Frederich Engels) wrote
    * Lenin’s modifications of Marx’s ideas
    * Trotsky’s modifications of Lenin’s ideas
    * What Stalin said Soviet Russia was like
    * What Soviet Russia was really like
    * Whatever Mao wanted to do to China at any one
    * Whatever some people who called themselves Marxists decided to call Marxism at the time
    * etc

    It’s got to the point where the most coherant Marxists (who IMO are in the tradition of Troksky) reject maybe a half of what Marx himself wrote. And I think Marx was a good enough thinker to recognize that this would happen.

    So there’s been various attempts to fix variations on Marxism with a name which clearly denotes them – Kautskyism, Communism, Luxemburgism, Cliffism, Gramsciism etc. Unfortunately – and inevitably – the meanings of these terms spread out as the corresponding ideas were reformulated or dropped and new ones were added. Plus of course a lot of people (especially journalists) just used the words sloppily and without understanding the real issues and debates.

    Political analyses and biological theories aren’t precisely analogous, obviously. But within each of the terms you mention – mutation, sociobiology etc – there is the potential for spread and shift of meaning. And there will always be plenty of people who misuse the terms anyway.

    In short: You can’t make people use words carefully by abandoning words they’ve used carelessly.

  2. #2 John Pieret
    April 15, 2007

    Why is “stasis” not evolution? Surely what appears to be stasis is the population wobbling around some relatively stable phenome and being kept in the vicinity by evolutionary forces, be it stablizing selection or whatever. But that’s still change over time.

    Aren’t I remembering this from something you’ve previously said?

  3. #3 Timothy Chase
    April 15, 2007

    Why is “stasis” not evolution? Surely what appears to be stasis is the population wobbling around some relatively stable phenome and being kept in the vicinity by evolutionary forces, be it stablizing selection or whatever. But that’s still change over time.

    A common definition for “evolution” is “the change in allele frequencies within a population.” Moreover, the word “stasis” itself implies a lack of change – even if there is stabilizing selection.

    I would suggest that you might do better if you kept to “law” and quit trying to horn in on matters of biology and epistemology which are clearly outside of your area of expertise…

    . . . . . . . Just kidding. ;-)

  4. #4 John Pieret
    April 15, 2007

    And if the allele frequencies are wobbling around some statistical norm, they are changing … which is why I put “stasis” in scare quotes to begin with. The question could be put another way: ‘is there such a thing as a population where the allele frequencies don’t change?’

    Are you going to quote Russell on, say, atheism now?

  5. #5 Timothy Chase
    April 15, 2007

    And if the allele frequencies are wobbling around some statistical norm, they are changing … which is why I put “stasis” in scare quotes to begin with. The question could be put another way: ‘is there such a thing as a population where the allele frequencies don’t change?

    Well, typically the full definition would be more along the lines of “the change in allele frequencies over time,” which I presume would mean some sort of a trend or at least random walk such that it doesn’t wobble about a point. As for whether there is a population where the allele frequencies don’t change, “in theory, yes” – but the population would have to be infinite in size.

    Are you going to quote Russell on, say, atheism now?

    Never had much interest in Bertrand Russell.

    I have some background in so-called “modern philosophy” from Descartes to Kant, read a fair amount of Aristotle and to a lesser extent Plato, and focused on early twentieth century empiricism – as well as the debate over foundationalism and coherentialism.

    However, nowadays I am a programmer. Interested in the origin of life and the role of viruses in the evolution of life. For example, roughly forty-nine percent of your genome consists of retroelements, endogenous retroviruses are responsible for creating a barrier in the placenta to the mother’s immune system, endogenous retroviruses engage in retrotransposition, but decay over time giving rise to retrotransposons, including LINEs (~7kbp in length).

    LINEs are capable of autonomous retrotransposition, but due to template switching give rise to SINEs and other retroelements. Due to the poly-tail of both LINEs and SINEs we have the generation of simple sequence repeats, with mononucleotide and dinucleotide repeats being common in promoter and intronic regions but extremely rare in coding regions and trinucleotide repeats being more common in the coding regions for metabolic proteins. The hypermutation of trinucleotide repeats in regulatory proteins in dogs have been responsible for the generation of much the variation found between breeds. PZ wrote something about that a while back. The hypermutation of repeats and their spread throughout the genome is evidently responsible for the evolution of much life’s evolvability.

    Repeats have a tendency for hypermutation, sometimes by as much as a factor of 100,000 greater than the background level of mutation. LINEs and SINEs contribute binding motifs to genes and can give rise to alternate promoters. Moreover, retroviruses and spliceosomal introns appear to have descended from type II introns found in bacteria, and both type I and type II introns are retroelements capable of retrotransposition. Type III introns are apparently a degenerate form of type II.

    Off the top of my head – I have been piecing it together from various papers for a while. A great many other interesting stories in science though.

    For example, metamaterials make possible a negative index of refraction – which should make it possible to create a shield for invisibility – and we are making a fair amount of progress along those lines. Also, according to an article in the April 12th issue of Nature, photosynthesis in plants appears to involve a form of quantum computation due to long-lived coherences which achieves highly efficient energy transfer. “Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems.” Pages 784 to 785. This is a story that has been developing for a while: there are technical papers over the last decade or so on the web.

    Stuff to keep you busy.

  6. #6 Timothy Chase
    April 15, 2007

    Oops!

    The story on photosynthesis actually begins on page 782, not 784.

    Looks like there is a story that might interest PZ in here as well: “A mirror-symmetric cell division that orchestrates neuroepithelial morphogenesis.” Not sure – some of these guys frown on “Nature.”

  7. #7 John Wilkins
    April 15, 2007

    You can’t make people use words carefully by abandoning words they’ve used carelessly

    You can’t make people do anything in language, but you might convince them to be less careless. Sure, these replacement terms will themselves acquire novel and ambiguous meanings, but at the moment they are far more exact than “Darwinism”, which I am arguing is all things to all people, and hence largely meaningless.

    As to “Marxist”, well I am a marxian in some respects (an old word not so tainted), but not and never a Marxist :-)

    On “stasis” – complete stasis is a boundary for evolutionary processes, but in and of itself (rather than as a special case of evolution) it cannot be distinguished from fixism. Hence, I think that we need to ensure that selection is the cause of stasis for it to be considered an evolutionary process; the default assumption is that things are going to change under an evolutionary account – change is the “natural state” and so stasis needs explanation. Under the fixist view, stasis was the natural state, and variation was the explanandum.

  8. #8 Timothy Chase
    April 15, 2007

    On “stasis” – complete stasis is a boundary for evolutionary processes, but in and of itself (rather than as a special case of evolution) it cannot be distinguished from fixism. Hence, I think that we need to ensure that selection is the cause of stasis for it to be considered an evolutionary process…

    So paradoxically, stasis becomes a process, in which case we need to look for a new definition of “evolution.” Frankly I was a little uncomfortable with a definition involving a population in as much as a population is generally thought of as a population belonging to a species, in which case the definition would seem to make “evolution inapplicable above the population level and therefore species level.

  9. #9 Timothy Chase
    April 15, 2007

    Simply in terms of the technical terminology, people are still in the process of clearing up some of the confusion. For example, promoters were divided into basal promoters and upstream promoters, and upstream promoters were distinguished from enhancers both by their distance from the transcription start site (the promoters are closer) and the fact that the upstream promoters are orientation dependent. But this nice, neat division is changing – looking more like a continuem. Likewise the term “gene” is changing, such that we will now speak of protein genes and rna genes, where rna genes do not themselves get transcribed into proteins, but are involved in the regulation of the expression of other genes. Then of course what may be an exon for one gene may be an intron for another. Then there are all of the different kinds of “polymorphisms” – copy number polymorphism, locus polymorphism, promoter polymorphism, promoter number polymorphism, etc.. We seem to have moved a little beyond Darwin’s concept of “variation.” And of course there is the problem of demarcating microsatellites and minisatellites, where the line dividing the two is typically between 5 and 10 bps.

  10. #10 Timothy Chase
    April 15, 2007

    Then you will find different conceptual schema being used to describe what is essentially the same thing. For example, you might speak of enhancers and promoters which are contrasted with regulatory proteins, or alternatively, there are the trans-acting regions (which I presume include both the enhancers and the promoters) and the transfactors – which are normally thought of as refering to the regulatory proteins, but which might also refer to the products of rna genes. The language must adapt to the discoveries, but then it can also make the conceptualization of later discoveries more difficult when it is based upon something which only seems to be an essential and is later shown to be otherwise. One of the problems I keep encountering is simply lining up the different vocabularies and uses of the terms when trying to piece things together from different papers.

  11. #11 chris y
    April 16, 2007

    There was a phrase: “Descent with modification”, which I remember being generally used by some guy. It’ll come to me who that was in a minute. I think it’s a good phrase.

  12. #12 John Wilkins
    April 16, 2007

    Alas, it describes everyones ideas from Maupertuis to Goeffroy, and even Owen’s. Then there are the post-Darwinians like Osborn, Goldschmidt, Teilhard. It’s not that helpful except to identify those who are neither fixists nor Platonists.

  13. #13 Clastito
    April 16, 2007

    Hmm if all points these are the only I can say are truy “Darwinian” that is, related to the core thinking of Charles darwin

    Transmutation of species

    1.1 Gradually (gradualism)

    2. Natural selection

    2.1 As a cause of adaptation
    2.2 As a cause of speciation

    3. Competition and struggle

    3.1 Between members of the same species
    3.2 Between different species

    5.2 Individual selection

    7.3 Individualism
    7.9 Progressivism

    8.1 Population thinking

  14. #14 Timothy Chase
    April 16, 2007

    I seem to remember that he also took the view that speciation was principally sympatric speciation – that is, within the same area. Nowadays we think of speciation as occuring primarily by means of allopatric speciation (in different areas) and parapatric speciation (where the two areas may overlap at the borders). It has been remarked that the Darwin’s study of finches would lend itself to allopatric speciation – which makes the emphasis he placed on sympatric speciation seem somewhat odd. However, there is some suggestion that speciation may actually accelerate if there is some genetic exchange between diverging populations, I believe due to the existence of linkages. Additionally, there is some recent support for sympatric speciation occuring on occasion.

  15. #15 Timothy Chase
    April 16, 2007

    Another point is that he took the view that selection was always “direct selection.” Natural selection could not anticipate the future, and as such it wouldn’t make sense, for example, for selection to select for variability. This is one of the points in which we are seeing some interesting developments. Variability – the ability to mutate – is itself an aspect of the phenotype, presumably. This is where the mutability of repeats may become particularly important, not in terms of the direct selection of the organism or of its immediate descendants, but in the ability of the organism to generate enough variation over several generations such that at least some of its descendants are likely to survive. The degree of mutability can be fine-tuned through point mutations which break up the repeats and thereby render them less susceptible to hypermutation.

    Within a variable environment, such mutability will presumably result in such indirect selection – and in a sense, we are lead to the view that natural selection has a foresight which Darwin himself had not foreseen. At least a couple of quite readable chapters are devoted this in “The Implicit Genome.” There is also some material on the web.