I've prepared a bunch of exam questions for students in my molecular evolution course. I gave them out two weeks before the exam and I promised them that I would post some of these questions on my blog to see how you would answer them. I'm hoping that you, dear readers, will show my students that there really is some controversy.Here's the third question.
Read the following statements by Richard Dawkins from his latest book, The Greatest Show on Earth (2009, pages 332 and 333).My students have read the Spandrel's paper so they are aware of the arguments made by Gould & Lewontin. Some of you may not be as familiar with those arguments so let me remind you of what Gould & Lewontin said back in 1978-79.When the neutral theory of molecular evolution was first proposed by, among others, the great Japanese geneticist Motoo Kimura, it was controversial. Some version of it is now widely accepted and, without going into the detailed evidence here, I am going to accept it in this book. Since I have a reputation as an arch-“adaptationist” (allegedly obsessed with natural selection as the major or even the only driving force of evolution) you can have some confidence that if even I support the neutral theory it is unlikely that many other biologists will oppose it!Dawkins doubts that any mutation giving rise to a visible phenotype can be neutral ("ultra-Darwinists like me incline against the idea"). Such mutations are only important in molecular evolution. Do you agree with him? Does Neutral Theory only apply to invisible mutations that can only be detected by molecular geneticists? Be sure to bring up the enormous variations in phenotypic characteristics among different human populations.
... When a gene mutates into one of its synonyms, you might as well not bother to call it a mutation at all. Indeed, it isn’t a mutation, as far as the consequences on the body are concerned. And for the same reason it isn’t a mutation at all as far as natural selection is concerned. But it is a mutation as far as molecular geneticists are concerned, for they can see it using their methods.
At this point, some evolutionists will protest that we are caricaturing their view of adaptation. After all, do they not admit genetic drift, allometry, and a variety of reasons for non-adaptive evolution? They do, to be sure, but we make a different point. In natural history, all possible things happen sometimes; you generally do not support your favored phenomenon by declaring rivals impossible in theory. Rather, you acknowledge the rival but circumscribe its domain of action so narrowly that it cannot have any importance in the affairs of nature. Then, you often congratulate yourself for being such an undogmatic and ecumenical chap. We maintain that alternatives to selection for best overall design have generally been relegated to unimportance by this mode of argument. Have we not all heard the catechism about genetic drift: it can only be important in populations so small that they are likely to become extinct before playing any sustained evolutionary role?To which I would add the following argument: "We've all heard about Neutral Theory but it only applies to inconsequential mutations detectable only by molecular geneticists."
