Just how natural is selection?

Evolution is not natural selection.

So wrote R. A. Fisher, mathematician, biological theorist and unfortunate eugenicist. This is the preface to a book that kick-started, although not on its own, the synthesis of Mendelian genetics and evolutionary theory in 1930: The Genetical Theory of Natural Selection. Fisher was, by all accounts, a thoroughly unpleasant man, not least to his wife, who after being pressured to have 8 children to meet Fisher’s eugenical expectations, finally had enough and left him. Nevertheless, his mathematical contributions effectively set the foundations for population genetics and many statistical techniques.

But the point that he made in 1930, that natural selection is not evolution, is one that should be recited to all undergraduates.1 My mentor (he perhaps would have rejected that claim), David Hull once wrote “Evolution is so simple almost anyone can misunderstand it.” But it depends on what work “evolution” is doing here. Does he mean “evolution by natural selection” or “evolution itself, however realised”? Hull was a clear thinker, but I suspect he meant the former, in the way Fisher described.

This has been the source of much confusion. Many people who consider themselves “Darwinians” hold that all evolutionary change is the result of selection, including local variance, speciation, and large scale phylogenetic trends. And selection is seen as a kind of teleological process leading to an optimal outcome. These debates are largely over in biology itself – apart from anything else, stochasticity is understood in things like genetic drift and contingency, but in the intellectual neighbourhood of evolution that is not done by biologists, but sometimes is, fitness, adaptation, and evolution to a more perfect type, are all still in play as viable ideas.

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