Bad takes #1. We have long known.

An anonymous reviewer responded to the manuscript of Stoltzfus and Yampolsky (2009) with the claim that “we have long known that mutation is important in evolution,” citing the following passage from Haldane (1932).

A selector of sufficient knowledge and power might perhaps obtain from the genes at present available in the human species a race combining an average intellect equal to that of Shakespeare with the stature of Carnera. But he could not produce a race of angels. For the moral character or for the wings, he would have to await or produce suitable mutations

Actually, this passage demonstrates the opposite of what the reviewer implies, and so we included it in the final version of the paper. What is Haldane suggesting?

I can’t resist a good story, so let’s begin with this 1930s photo of Italian boxer Primo Carnera, his friend and fellow heavyweight champ Max Baer, and Hollywood actress Myrna Loy. Baer dated Loy in real life. They made a movie together, the three of them (thus the staged publicity photo). Baer, one of the greatest punchers of all time, became a hero to a generation of Jewish sports fans when he (being half-Jewish) demolished Max Schmeling, Hitler’s champion (after that, Hitler outlawed boxing with Jews). He literally killed one of his opponents, and repeatedly sent Carnera to the floor during their single fight.

Primo Carnera, Myrna Loy, and Max Baer in a publicity photo from the 1930s

But the point of this picture is that, although Baer was a formidable man, Carnera makes him look small. Other fighters were afraid to get in the ring with him. Furthermore, although Carnera was huge — 30 cm taller and 50 kg heavy than the average Italian of his generation —, he was not the aberrant product of a hormonal imbalance. This photo shows a huge man who is stocky but well proportioned, muscular, and surprisingly lean. Again, he was not a misshapen monster, but a man at the far extremes of normal human stature, which is precisely Haldane’s point.

Selective breeding to the quantitative extremes of known human ability, Haldane proposes, could produce a race combining the extreme of Carnera’s magnificent stature with Shakespeare’s magnificent verbal ability.

Haldane contrasts this with a different mode of evolution dependent on new mutations, which might produce a race of angels, if one could wait long enough for the mutations to happen. That is, Haldane is contrasting (1) a mode of evolution that could combine the known extremes of human ability with (2) a mode of evolution that could generate imaginary fictitious not-at-all-real creatures. Both Haldane and Fisher argued that a mode of change dependent on new mutations would be too slow to account for the observed facts of evolution. They argued instead that evolution must take place on the basis of abundant standing variation.

That is, in the passage above, Haldane is not endorsing a mode of mutation-dependent evolution, but gently mocking it, in contrast to a mode of evolution that, based on quantitative standing variation, could produce a race of magnificently eloquent champions.

Thus, the reviewer’s comment was a bad take on Haldane, misrepresenting his intention.

In addition, the “we have always known” comment represents a more general category of bad take that substitutes, in place of a specific target of criticism, a much broader, fuzzier, or more generic claim.

Of course, the reviewer is correct that scientists in the mainstream Modern Synthesis tradition have always known that mutation is important in evolution. More precisely, the importance assigned to mutation was that it is ultimately necessary, because without mutations, evolution would grind to a halt. Haldane, Fisher, Ford, Huxley, Dobzhansky, and others said this explicitly.

However, they did not say that mutation is important as a dispositional factor. Instead, they argued explicitly against this idea, e.g., Haldane (1927) is the original source of the “mutation pressure is a weak force” argument (see Bad takes #2).

The theory of biases in the introduction process, by contrast, says that mutation is important in evolution as a dispositional cause, a cause that makes some outcomes more likely than others, and that this importance is achieved (mechanistically) by way of biases in the introduction process.

So, the reviewer is making an implicit bait-and-switch argument. The theory of biases in the introduction of variation is a specific population-genetic theory with specific conditions and implications, and the reviewer is responding to this by saying “we have always known that mutation is important,” but this is not the same thing: the traditional importance assigned to mutation is not “dispositional cause that makes some outcomes more likely than others” but “ultimate source of raw materials without which evolution would grind to a halt.”

Finally, this bad take is part of a family of bad takes in which the novelty of a claim X is rejected on the grounds that X sounds vaguely like X’, or that X can be categorized as a member of some larger and fuzzier class of claims (see Bad Takes #5: Contingency). This is often the case with “we have long known” arguments. If the theory was in fact old, the reviewer would not have made a vague “we have long known” argument, but would have cited the original source of the theory, e.g., “Of course the theory of biases in the introduction process is not new, because Haldane proposed exactly the same theory 70 years ago and worked out its implications!” In fact, no such antecedent exists, which is why, to defend tradition, the reviewer must resort to a bait-and-switch argument.

For more bad takes on this topic

This is part of a series of posts focusing on bad takes on the topic of biases in the introduction of variation, covering both the theory and the evidence.

References

Haldane JBS. 1932. The Causes of Evolution. New York: Longmans, Green and Co.

Stoltzfus A, Yampolsky LY. 2009. Climbing mount probable: mutation as a cause of nonrandomness in evolution. J Hered 100:637-647.


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