Some thoughts on the conceptual immune system of the “Synthesis”

As noted in Bad Takes #3, there is a long tradition of dismissing internalist theories on the false grounds that such theories are appeals to teleology or mystical inner urges. If an alternative theory can be dismissed in this manner a priori, as an absurdity, then no further effort is required: no complex theoretical modeling is required, no time-consuming experiments, and no difficult analyses of empirical data. Instead, one simply considers a caricature of the alternative theory, dismisses it as absurd, and — without suffering a moment of cognitive dissonance — one goes back to assuming that selection is the ultimate source of meaning and explanation in biology.

Indeed, 20th-century neo-Darwinism developed its own conceptual immune system, based on a series of facile arguments, each representing some type of excluded-middle or false-dilemma fallacy.

To reject thisArgue against this versionIgnoring this version
SaltationEvolution only takes leaps; new features must arise fully formedEvolution normally includes steps or jumps reflecting distinctive variations
CatastrophismThe emergence of key innovations or higher taxa requires catastrophes (revolutions)Non-normal catastrophes play a disproportionate role in major evolutionary episodes
MutationismEvolution is driven by mutation pressure without selectionThe timing and character of evolutionary changes may reflect the timing and character of mutation events
OrthogenesisEvolution moves in a pre-determined straight line due to mystical inner urgesThe course of evolution strongly reflects developmental channeling of variation

Before proceeding further, please bear in mind that a theory is different from the bad arguments used to support the theory and to reject alternatives. Strawman arguments about mutationism and orthogenesis are not part of a neo-Darwinian theory of evolution: instead they belong to a culture or thought-collective associated with the neo-Darwinian theory.

When our focus is on identifying and evaluating theories, our main concern is the third column rather than the second one. Critics of neo-Darwinism rarely state ideas in the second column, and often state ideas in the third column. If our goal is to understand reality, we consider the best version of a theory, not the stupid version: a genuine approach to scientific inquiry requires a focus on the third column.

However, if we want to understand how a thought-collective perpetuates itself decade after decade, we need to understand propaganda. In Synthesis propaganda, these excluded-middle arguments are used to maintain the all-important TINA doctrine: There Is No Alternative.

The first line of defense against alternative ways of thinking is to claim that they are inherently flawed or patently absurd, using the straw-man arguments above. Within the Synthesis propaganda system, critics of neo-Darwinism are depicted as the victims of mental disabilities (e.g., typological thinking) that cause them to behave irrationally and hold views with obvious flaws. For instance, students are taught that mutationism is the obviously flawed view that evolution takes place by dramatic mutations alone without selection. The answer to the question of why Thomas Hunt Morgan would believe such an obviously wrong theory is that he had a mental block about selection. Poor man. This is the same Thomas Hunt Morgan who won a Nobel prize for his work in genetics.

With most readers, this kind of argumentation suffices to maintain ideological conformity. However, sometimes there are doubters or rebels or merely deep thinkers who imagine that there might be something of value in alternatives to neo-Darwinism.

In this case, the priests of the Synthesis religion must offer a more sophisticated argument to maintain the faith of doubters and to hold off critics. One common approach is appropriation: conceding some aspect of the alternative view, but describing it in different language, grounding it in the sacred texts and associating it with illustrious ancestors, and insisting that the alternative is not the same thing as any historical alternative to neo-Darwinism.

For instance, when confronted with evidence that evolution may sometimes reflect developmental channeling of variation, the priest of the Synthesis may admit that the evidence exists, but insist that it is not very compelling, that this is definitely not orthogenesis, and anyway, that this possibility was foreseen by his holiness Pope Ernstius of Harvard himself, therefore it is already part of the Synthesis canon. Futuyma (2017) makes precisely this argument, citing the following passage from Mayr:

“Every group of animals is ‘predisposed’ to vary in certain of its structures, and to be amazingly stable in others . . . Only part of these differences can be explained by the differences in selection pressures to which the organisms are exposed; the remainder are due to the developmental and evolutionary limitation set by the organisms’ genotype and its epigenetic system . . . the epigenotype sets severe limits to the phenotypic expression of such [random] mutations; it restricts the phenotypic potential.  The understanding of this limitation facilitates the understanding of evolutionary parallelism and polyphyletic evolution.”

Mayr (1963) p. 608

A better source to cite for this kind of internalist thinking would have been Eimer or indeed, dozens of other non-Darwinian scientists who advocated much more forcefully for a role of internal developmental biases. However, to cite Eimer would be to go outside the Synthesis tradition.

Mayr typically was disdainful of internalist theories and evo-devo, and he repeatedly invoked the contrary neo-Darwinian position that, because natural populations have infinite variability, when the same thing happens twice in evolution, this must be because it is the uniquely apt solution. In the above passage, Mayr has gone off-script. However, Futuyma, (2017) is happy to accept the above statement as justification to fully appropriate developmental bias on behalf of the Synthesis tradition: “The idea that development can influence the direction of evolution was fully congenial to the architects of the ES.” Note that this is a statement about people and not about scientific theories, i.e., there is no explanation of how developmental bias follows from the Castle experiment or how it would be consistent with the shifting-gene-frequencies theory.

In this kind of traditionalist thinking, the focus is not on maintaining a coherent scientific position, but on nurturing a pious attitude of deference to traditional authorities. The core belief is not in the completeness and correctness of a theory, but in the fullness and authority of a Synthesis tradition: traditional authorities were always right — or almost always—, and any deficiencies in their thinking are forgivable consequences of the limited evidence available to them at the time. They foresaw most things, and to criticize them for failing to foresee all things would be unfair.

Likewise, consider the issue of gradualism vs. saltationism. At one extreme is the position of natura non facit salta, i.e., nature does not take leaps. Thinkers such as Fisher and Darwin thought that, for practical purposes, all evolutionary changes are composed from infinitesimal effects. Darwin said that his theory would “utterly break down” if any organ could not have been formed by a succession of infinitesimal changes. The intermediate position of historic saltationists such as Bateson and T.H. Huxley is that evolution has some jumps. The contrary extreme from gradualism, in which evolution is (for practical purposes) all large jumps, is found only as a strawman theory.

As explained in Why size matters, the gradualist position is not arbitrary for neo-Darwinism and other views that assume empirical adaptationism. If selection and variation are like the potter and the clay, with variation merely providing raw materials and selection providing shape and direction, then variation has to be composed of fine particles. If all change is small, it is possible to argue that selection governs evolution and can do anything, working from infinitesimal variation in every trait. But if evolutionary change comes in chunks, this immediately takes something out of the control of selection—the character and timing of discrete variations—, and then we need some kind of theory for the character and timing of variations in order to have a workable theory of evolution.

In other words, empirical adaptationism necessarily provokes theories of gradualism (in the sense of infinitesimalism). This is not just a logical conclusion, it is how scholars such as Mayr or Gould have reconstructed the actual development of Darwin’s thinking. Likewise, the empirical conclusion that saltations actually occur in evolution provokes the search for internalist theories that address the generation of non-infinitesimal variations. This is not just a logical conclusion, it is why Bateson cataloged distinctive variations in order to study evolution.

Darwin provided some early examples of the excluded-middle arguments outlined above. In his writings, he nearly always embellishes his case against discrete evolutionary steps by referring to them with dramatic language as “monstrosities”:

I reflected much on the chance of favorable monstrosities (i.e., great and sudden variations) arising.  I have, of course, no objection to this, indeed it would be a great aid, but I did not allude [in OOS] to the subject for, after much labor, I could find nothing which satisfied me of the probability of such occurrences. There seems to me in almost every case too much, too complex, and too beautiful adaptation, in every structure, to believe in its sudden production.

Why “great and sudden”? Why not “modest”? Why not “medium-sized and sudden”? Describing saltations in provocative and negative language is a common rhetorical trick, e.g., Wright associates them literally with “miracles”:

“From assisting Prof. Castle, I learned at firsthand the efficacy of mass selection in changing permanently a character subject merely to quantitative variability. Because of this and a distaste for miracles in science, I started with full acceptance of Darwin’s contention that evolution depends mainly on quantitative variability rather than on favorable major mutations. ” (Wright S. 1978. The Relation Of Livestock Breeding To Theories Of Evolution. Journal Of Animal Science 46:1192-200.)

Note that Wright misrepresents Darwin’s position as calling for “mainly” quantitative variability rather than exclusively infinitesimal variation.

This reliance on strawman arguments makes it difficult to determine what Darwin’s followers actually believe.  Clearly they are against monstrosities, but how large of a non-monstrosity will they tolerate?   Clearly Wright is against miracles and for quantitative variability, but what exactly does that mean?  When gradualism fails, will he claim that there are no miracles and insist he was right all along?  

Today the issue has been turned on its head. Saltation is still presented as the straw-man theory that all evolutionary changes are dramatic leaps, or in which major taxon-defining traits must appear in a single step (e.g., Coyne).  The contemporary scientists who conclude in favor of saltationism on empirical or theoretical grounds insist that they are not saltationists, and they sincerely hold the erroneous belief that their position is consistent with neo-Darwinism.

In a famous review paper, Orr and Coyne (1991) ransacked the classic empirical case for gradualism, concluding that it was based on hardly any evidence at all, that it was biased, and that there was contrary evidence for non-gradual effects. But instead of describing their results accurately by saying that the neo-Darwinian position is rejected and the saltationist one is upheld, they say this:

We hasten to add, however, that we are not ‘macromutationists’ who believe that adaptations are nearly always based on major genes. The neo-Darwinian view could well be correct. It is almost certainly true, however, that some adaptations involve many genes of small effect and others involve major genes. The question we address is, How often does adaptation involve a major gene?

Likewise, evo-devo thinker Wallace Arthur (2004) describes a saltationist position and then insists that he wants to “make clear that I am not a ‘saltationist’ like Goldschmidt” (p. 107).

This is what happens when you teach people that neo-Darwinism is always right and there are no scientific alternatives, without first defining neo-Darwinism as a substantive falsifiable position: the student absorbs the lesson that neo-Darwinism is always right and then they define it post hoc, based on whatever seems right. For instance, note how the issue is framed by researchers cited by Chouard:

Many researchers have welcomed the return to favour of large-effect mutations and have resurrected Goldschmidt’s long reviled idea of the hopeful monster. But they can’t ignore the small-effect mutations. “We need much more data before the issue of large versus small can be settled”, says Coyne. Kingsley, like Coyne favours a middle-ground view, in which neither large- nor small-effect mutations are ruled out. “Our work has too often been portrayed as saying that Darwin was wrong” about big leaps in adaptation, he says. But in fact, none of the traits his group has studied is completely due to the effects of a single gene.

Instead of defending the all-small position of genuine neo-Darwinian gradualism, the traditionalists now defend the not-all-large (i.e., some-small) position that you “can’t ignore the small-effect mutations.”

Likewise, in response to Shapiro’s criticism that molecular saltations speak against Darwinism, Dean (2012) objects thus:

His stance is patently unfair. Thomas Huxley famously criticized Darwin for championing too gradualist a view of phenotypic evolution. Today’s Darwinists accept Huxley’s criticism . . . Horizontal gene transfer, symbiotic genome fusions, massive genome restructuring (to remarkably little phenotypic effect in day lilies and muntjac deer), and dramatic phenotypic changes based on only a few amino acid replacements are just some of the supposedly non-Darwinian phenomena routinely studied by Darwinists.

Here the author has gone all the way to a purely cultural position on neo-Darwinism: there is no fixed scientific theory attached to the brand, only a cultural tradition consisting of people (Darwinians) whose beliefs may change at any time. If neo-Darwinian people start studying saltations, this makes saltations part of neo-Darwinian brand.

I could go on, but those examples should be sufficient to make the point that evolutionary discourse is littered with blatant strawman arguments and outrageous goal-post-shifting. When apologists for tradition shift from merely rejecting strawmen to appropriating the excluded middle on behalf of tradition, this represents a genuine scientific shift that is masked by conservative rhetoric. Being able to see through the misleading rhetoric is a skill that can be learned. In the current climate of evolutionary discourse, it is a necessary skill.

References

  • Arthur W. 2004. Biased Embryos and Evolution. Cambridge: Cambridge University Press.
  • Dean (2012) Review of Evolution: a View from the 21st Century. Microbe Magazine. (available via the wayback)
  • Mayr E. 1963. Animal Species and Evolution. Cambridge, Massachusetts: Harvard University Press.
  • Orr HA, Coyne JA. 1992. The Genetics of Adaptation: A Reassessment. American Naturalist 140:725-742.

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