Reactionary fringe meets mutation-biased adaptation. 5.3. How history is distorted.
According to Bateson (1894). natural selection is “obviously” a “true cause.” Punnett (1905) explains that mutations are heritable while environmental fluctuations are not, concluding that “Evolution takes place through the action of selection on these mutations” (p. 53). De Vries begins his major 1905 English treatise by writing that
Darwin discovered the great principle which rules the evolution of organisms. It is the principle of natural selection. It is the sifting out of all organisms of minor worth through the struggle for life. It is only a sieve, and not a force of nature (p. 6)
Morgan (1916), in his closing summary, writes:
Evolution has taken place by the incorporation into the race of those mutations that are beneficial to the life and reproduction of the organism (p. 194)
The views of these early geneticists were published, read, and discussed. All 4 were awarded the Royal Society’s Darwin prize in the period from 1900 to 1930.
So, why does the evolutionary literature continue to tell a story in which the early geneticists (“mutationists”) reject selection and believe in evolution by mutation alone (e.g., Dawkins 1987, p. 305 of The Blind Watchmaker; Cronin 1991, p. 47 of The Ant and the Peacock; Ayala and Fitch 1997; Eldredge 2001, p. 67 of The Triumph of Evolution; Segerstråle 2002, Oxford Encyclopedia of Evolution 2, pp. 807 to 810; Charlesworth and Charlesworth 2009)?
How does history get distorted? Why do the distortions persist? Is there a process for correcting them?
According to another story, opponents of Darwinism suffered from a condition called “typological thinking” or “essentialism,” preventing them from using “population thinking” to understand systematics and evolution. Historian Mary Winsor (2006) begins her piece (below) by explaining that the Essentialism Story was “fabricated” by Ernst Mayr.
Mayr’s self-serving accounts of history are so notorious that historians have a name for them– “Synthesis Historiography” or SH (Amundson, 2005), i.e., telling history in ways that turn out right for the Modern Synthesis.
The Essentialism Story, the Mutationism Myth, and the Eclipse of Darwinism are all parts of SH. In SH, all truths must come from Darwin and his followers, and this makes the early geneticists problematic, because they were crucial in the development of genetical thinking about evolution. Between 1900 and 1920, they conceptualized the multiple-factor theory, the biological species concept, the Hardy-Weinberg equilibrium, the allelic selection model, and the probability of fixation (Stoltzfus and Cable, 2014; Provine, 1971).
So, SH turns history on its head: the early geneticists are said to have rejected selection; the period of dramatic discovery and innovation from 1900 to 1920 is depicted as a period of darkness and confusion, the Eclipse of Darwinism, when the world was deprived of His light; and the credit for introducing 20th-century views of mutation and heredity to evolutionary biology is awarded to 19th-century physiologist August Weismann (though genuine historians object that Mayr’s story does not reflect Weismann’s views: see Winther, 2001, or Griesemer, 1989).
The above timeline of “notable people who have contributed to evolutionary thought” from a popular education resource illustrates SH. I have added a pink rectangle enclosing the birth year of anyone 25 to 60 years old– the prime of a scientist’s life– when genetics was discovered, thus implicating de Vries (1848), Johannsen (1857), Bateson (1861), Cuénot (1866), Morgan (1866), and Punnett (1875). No timelines begin in the box.
Normality drift and back-projection
Mayr’s historical fictions are brazen, but most distortions emerge in a subtle and passive way, when ordinary scientists assume, incorrectly, that the old language was intended to cover current results, that the old theories were broadly conceived to cover all reasonable possibilities, and that dead authorities looked at evolution the way we do. I have done it myself.
For instance, contemporary scientists may use “Darwinian evolution” or “Darwinian adaptation” (e.g., here or here) for lucky mutant models of de Vriesian aptation, not realizing that Darwin and his Synthesis-era followers deprecated this mode of change, previously called “pre-adaptation” or “random pre-adaptation” (see Stoltzfus, 2017). When Darwin was criticized for providing “not a theory of the Origin of Species at all, but only a theory on the causes which lead to the relative success and failure of such new forms as may be born into the world,” his response was “That may be a very good theory, but it is not mine” (for a scholarly analysis of Darwin’s position on the creativity of selection, see Beatty, 2010, 2016).
Another example is provided by the continued use of the phrase “Fisher’s geometrical model” (e.g., here, here, or here) for a model that, in its current form, rejects Fisher’s assumptions and subverts his conclusion (see Stoltzfus, 2017 supplement). In the original model, the size of an allelic effect determines the chance of being beneficial, which is negatively correlated with effect-size– the smallest effects having the highest chance. The model was used to argue that the smallest changes are the most likely, in support of natura non facit saltum.
Fifty years later, Kimura re-cast Fisher’s argument in a stochastic origin-fixation framework, which creates a second effect, positively correlated with effect size, due to the higher chance of fixation of beneficial mutations with larger effect-sizes. The combination of divergent effects results in an intermediate optimum, undermining Fisher’s original conclusion, and undermining the original gradualist intent of Fisher’s argument.
This distortion is mainly a matter of normality drift, but the literature also reveals signs of back-projection, i.e., the anachronistic belief that Fisher shared Kimura’s mutationist view (e.g., p. 121 of Orr, 2005).
Back-projection is both pernicious and difficult to avoid. I have done it myself, in regard to the following passages
“Probably the most effective aid in establishing new genes lies in their repeated production by independent mutations. A gene produced twice by mutation has twice as good a chance to survive as if produced only once.” (Shull, 1936, Evolution, p. 140)
“There is another result, clearly established by the genetic work on Drosophila, that is favorable to the final establishment of a new type of character if it is beneficial. Most, perhaps all, of the mutations appear more than once. This improves their chances of becoming incorporated in the species, and if the mutation produces a character that favors survival the chance of its becoming established is still further increased.” (Morgan, 1925, Evolution and Genetics, p. 140 to 141).
Previously, I cited the “twice as good a chance” passage from Shull to suggest that the early geneticists intuited the proportional effect of biases in the introduction process. Indeed, the passages above indicate that Morgan and Shull thought that the chances of introduction are consequential for evolution. Other writings show that they were interested in the potential for internal biases in evolution, e.g., Shull (1935) wrote “What the world most needs, then, is not a good five-cent cigar, but a workable– and correct– theory of orthogenesis.”
So, it would seem obvious that they would put the pieces together and propose a theory of variation-biased evolution, implicating biases in the introduction process.
Yet, they did not. In the passages above, Shull and Morgan are simply not working out a theory for variation-biased evolution: they are making a plausibility argument in which evolution by mutation and selection is rendered more plausible by the fact that mutant alleles may be introduced multiple times, rather than having only a single chance to succeed or fail. In retrospect, this is embarrassingly obvious.
Remember the parable of the blind men and the elephant, or the example of chaotic dynamics hidden in familiar equation systems: until we know a theory, we just don’t know it, even if we can see most of the parts.
The cure for back-projection
Finally, let us return to TREE’s hatchet piece, whose authors reject the idea that the theory of Yampolsky and Stoltzfus is new:
Haldane (1927, 1933) fully presents the implications of biases in the introduction process, 70 years before Yampolsky and Stoltzfus, and this theory was then invoked by Mayr and Simpson to explain how variation imposes biases on adaptation. Clearly, this is already part of the Modern Synthesis.
I’m just kidding! They do not say that, because
Instead, they say something indirect and misleading:
“It is simply not true that the architects of the modern synthesis were unaware of the potential role of novel mutations in the evolutionary process because mutational bias was already discussed in Haldane’s and Dobzhansky’s early papers [19,74,75]. For instance, Dobzhansky discussed the possible role of mutation bias (expressed as ‘similarity in germ plasms’) as a potential explanation for parallel geographic variation in various species of lady-bird beetles”
The first mistake in this framing is to focus on a part or a premise of the theory, while neglecting the inner logic that leads from premises to conclusions. They are implying that, if someone notices that not all mutation rates are the same (mutation bias), they automagically grasp the implications of biases in the introduction process. This is a fallacy. Before we know a theory, we are like the blind men in the parable who identify the parts of the elephant but not the whole creature.
The second false step involves the conflation of people and theories that is central to Synthesis apologetics. Theories are not made of people. Even if some historic person knows the implications of biases in the introduction process, and likes the Modern Synthesis, this does not mean that the former theory is magically incorporated into the latter theory.
Nevertheless, let us consider what the cited sources– Haldane (1927, 1933) and Dobzhansky (1933)– have to say about the possible role of biases in the appearance of novel mutations in determining the course of evolution.
Haldane (1927) addresses the probability of fixation for a new mutation, and a mutation-selection balance model. He invokes opposing-pressures thinking, not biases in the introduction process, concluding that:
“Mutation therefore determines the course of evolution as regards factors of negligible advantage or disadvantage to the species. It can only lead to results of importance when its frequency becomes large.”
That is, Haldane derives the classic view that mutational effects require neutral evolution or high mutation rates. Strike one.
The second piece, Haldane (1933), begins by listing its 3 topics:
- “(1) Evolution due to a mutation rate so large as to cause the spread of a disadvantageous character . . .
- (2) Primary effects of the spread of genes nearly neutral from the point of view of selection . . .
- (3) Secondary effects of frequent disadvantageous mutations.”
None is the right topic. Strike two.
What about “Geographical Variation in Lady-beetles” by Dobzhansky (1933)? Though Dobzhansky was publishing work in experimental genetics at this time, here he is reporting a quantitative survey of variation in the patterns of spots on the elytra (wing-covers) of different species of lady-bird beetles. He finds similar patterns of variation in different species, and suggests an explanation:
“As stated above, there is observed a parallelism in the variability of the related species and genera. Homologous varieties of different species may be more similar to each other in appearance than the different varieties of the same species. This parallelism is, probably, due to the essential similarity of the germ-plasms of the related species. “
This is more promising. Dobzhansky is referring somewhat obliquely to the effect of parallel tendencies of variation in generating parallel patterns of intra-specific variation. The context makes clear that Dobzhansky (1933) likes the law of homologous series in variation proposed by Nikolai Vavilov (1922 [PDF]), cited as a “rule” on page 1:
“Large groups of related species and genera exhibit parallel series of patterns, upholding the rule of homologous series in variation, formulated by Vavilov (1922)”
What a “homologous” or “parallel” series means is that one species has varieties or races A, B, and C, and a second closely related species has corresponding varieties A’, B’, and C’. Vavilov’s (1922 [PDF]) theory held that
“Variation does not take place in all directions, by chance and without order, but in distinct systems and classes analogous to those of crystallography and chemistry. The same great divisions into orders and classes manifest regularities and repetitions of systems” (p. 84)
That is, Vavilov imagined something like the periodic table of the elements, but for systematics. He proposed a research program of identifying the pattern of variant forms characteristic of a taxon, and then looking for the forms that complete the pattern.
In other words, Dobzhansky is not advocating the Modern Synthesis, but a pre-Synthesis mutationist theory. This is an excellent illustration of why it is a mistake to use people as proxies for theories.
Furthermore, Vavilov’s theory is not explicit about population genetics, so one does not know, for instance, whether the proposed effects require high mutation rates or neutral evolution.
Thus (returning to the argument in TREE’s hatchet piece), for Dobzhansky or Haldane to know and even to like some of the thinking of the mutationists does not magically induce knowledge of the theory of Yampolsky and Stoltzfus (2001), much less make it part of the Modern Synthesis, which clearly was a repudiation of mutationism. Strike three.
In conclusion, when the authors of TREE’s hatchet piece write
“It is simply not true that the architects of the modern synthesis were unaware of the potential role of novel mutations in the evolutionary process”
they have deceived the reader.
What is happening here? Why would the authors of a refereed paper go out of their way to make a historical argument that is complete bullshit?
The answer, of course, is that the authors have thoroughly deceived themselves. To understand how, imagine that we have a strong prior belief that everything valuable comes from tradition and traditional authorities, e.g., we might believe that
“. . . the major problems of the field have been solved. We understand both the nature of the mutational processes that generate novel genetic variants and the populational processes which cause them to change in frequency over time — most importantly, natural selection and random genetic drift, respectively . . . no serious evolutionist will now defend once prevalent views such as orthogenesis (predetermined evolution) or the inheritance of acquired characteristics . . . we will never again come up with concepts as fundamental as those formulated by the ‘founding fathers’ of population genetics (Fisher, Wright and Haldane), or do experiments as path-breaking as Dobzhansky’s demonstration of natural selection acting on polymorphic chromosome inversions.”Charlesworth B. 1996. The good fairy godmother of evolutionary genetics. Curr Biol 6:220.
When our faith in the fullness and authority of tradition reaches this upper bound, we will respond to the claim of a new principle with unyielding skepticism, as if it were a claim of finding a unicorn or being abducted by aliens. When faced with evidence that Haldane found a unicorn (i.e., argued against the efficacy of tendencies of variation) or that Fisher was abducted by aliens (i.e., ignored the potential importance of biases in the introduction process), we will be confident that the evidence must have some other explanation, even if we can not prove it.
Thus, the deceptive attributions in TREE’s hatchet piece arise because the authors are operating near the Charlesworth limit. They have an unwavering confidence that contemporary scientists cannot possibly have formulated a new principle, and that traditional authorities must have known this earlier. Any ancient text that mentions mutation bias or new mutations simply strengthens this prior belief.
When we confront a scientific issue that is more than a generation old, we necessarily become historians. In such a context, getting the science right depends on getting the history right, and this requires an awareness of two factors. The first is that the literature features a multitude of individually minor instances of normality drift and back-projection, whose cumulative effects may be profoundly distorting.
The second is that the Synthesis literature is rife with outrageously self-serving accounts of history. When such stories are repeated countless times, people come to believe they are well established, and that they can only be overturned by extraordinary evidence. However, Synthesis Historiography is propaganda, not scholarship. The term to describe well meaning people who repeat propaganda is “useful idiot.” We have a scholarly obligation not to repeat dubious historical claims, until we see evidence.
What does evidence look like? In recent posts, we have seen multiple examples of statements from historic texts that clearly convey the inner logic of theories, and which reveal the know-like-love relationships of persons to theories.
Most scientists do not have time to pore over the historical literature searching for this kind of evidence. However, being a rigorous consumer of evidence is much easier than being a producer: one simply demands that textual evidence demonstrates exactly what is being claimed, i.e., one treats meta-scientific claims as carefully as one would treat a scientific claim.