Mary Midgley made a contribution to The Guardian’s Comment is Free section last week (February 9th, 2009), Selectionism can only take us so far -Darwin made it clear that he never meant to exalt selection into a kind of ‘universal acid‘. This is in the series concerning the limits of Darwinian explanations.
I have to confess that, having read her article, I cannot understand what it is she is trying convey, and in fact much of what she writes seems to betray a lack of understanding of evolutionary biology.
Natural selection can’t possibly account for everything in evolution any more than human selection can account for everything in a chihuahua.
I suppose my response would be that no-one in their right mind would make such an assertion in the first place. The reasonable biologist would say that the first dogs were products of natural selection, but that human intervention by dog breeders is what has moulded their descendants into the myriad of forms we see today.
Selection only works where there is a given range of candidates. Selectionist theorists take this range for granted, treating the selectees as if they were indefinite, passive objects with no natural tendencies of their own. But (as helpful scientists have lately pointed out) at every stage, from the initial molecules to the most complex living organisms, these participants are themselves specific, active entities.
This is just a hopelessly incorrect understanding of evolutionary theory, I think. I am uncertain what Midgley means by the first sentence of that quotation. I don’t know what Midgley means by “Selectionist theorists”, nor do I know what she means by “helpful scientists”!
[...] a particularly enterprising mouse which suddenly decides to move into a new valley can defeat the best-laid plans of its former evolutionary pressures. And we can see that an alien observer might well suppose that it would be quite easy to turn a person into a kangaroo or a chihuahua into a slug. But in fact no amount of selection will achieve these feats. The moral is that the tendencies of the materials present are every bit as important in evolution as the selective forces.
Evolutionary pressures (presumably this means natural selection) don’t have “plans”, best-laid or otherwise. And as a commenter at the Guardian page pointed out, an alien observer who had the scientific and technological wherewithal to reach our planet would probably have a better understanding of biology than Midgley.
But he made it clear that he was always unhappy about the apparent inadequacy of this cause to explain the whole range of actual effects. When he said that thinking about the problem of the peacock’s tail made him feel positively sick he was clearly expressing this deep uneasiness – this sense that the change was too large to be explained in such a way.
I have always understood his uneasiness was due to the fact that biological observation might not always be easy to explain, and indeed, they are often exploited by the ignorant as weapons to bring the evolutionary edifice down. The “problem” of the peacock’s tail seems to me to not be a problem at all, and is explicable by sexual selection.
In the final two paragraphs, Midgley wanders off into odd territory, analogising the influences that lead to evolutionary change to the Hindu trinity of Shiva, the destroyer, Brahma the creator and Vishnu the preserver (she ascribes this to Lyell). This I don’t get at all, and I think I need that to be explained. My personal view is that in these closing paragraphs, Midgley merely reveals that she just doesn’t like the scientific explanation for how life got to be the way it is – the Wonderful Life that I see around me. One final comment: isn’t it time the commentators who seem so keen to pick at evolutionary theory realised that evolutionary biology has moved on in the last 150 years?