Einstein and the Units of Selection
No, the title of this post is not a typo. I just finished reading through the first three articles in the most recent issue of Philosophy of Science. They are an argument-response-rebuttal between Elisabeth Lloyd ("Why the Gene Will not Return"; "Pluralism without Genic Causes?") and Ken Waters ("Why Genic and Multilevel Selection Theories Are Here to Stay"), who is one of her targets in the original essay. As the biologically-inclined among you will have inferred, this is the latest installment in the long-standing units of selection debate; very roughly, the question in these debates is: Upon what does natural selection operate? Organisms? Genes? Groups of organisms?
Ken Waters' basic response to this question -- which he first articulated in "Tempered Realism about the Force of Selection" (Philosophy of Science 1991) -- is that there is no determinate fact of the matter about whether selection is really acting at the level of the gene or the organism/ genotype. Mathematical models can be constructed in terms of genes and in terms of genotypes, and both kinds of model suffice to represent the facts of dynamic changes in populations. (See "The Dimensions of Selection," P. Godfrey-Smith and R. Lewontin, Philosophy of Science 2002, for an excellent treatment of the niceties of of the situation.) Since these different models do not represent different facts, Waters concludes that we will choose between them on pragmatic grounds. In the language of his current paper, Waters says that different models "parse" the causal structure differently.
For the purposes of this post, I will assume Waters is correct to maintain that there is no fact of the matter about whether the true cause of any particular evolutionary change lies at the level of the gene or the genotype. What I want to do is to compare this situation with Einstein's reaction in (what I consider) an analogous situation.
At the beginning of Einstein's 1905 paper that introduces special relativity, he asks us to imagine a conductor and a magnet in relative motion with respect to each other. If the take the conductor to be at rest and the magnet moving, then Maxwell's theory says that an electromotive force is generated in the conductor, which gives rise to an observable electric current C. If, on the other hand, we assume the conductor is moving and the magnet is at rest, then Maxwell's theory says that no electromotive force is generated in the conductor, but an electric field is generated around the magnet -- and this field induces exactly the same electric current C as before. Einstein's conclusion is that we are not actually dealing with two physically different situations here; rather, our theoretically distinct models are representing one and the same set of facts. This is exactly Einstein's argumentative maneuver in his famous elevator thought-experiment as well: though the pre-Einsteinian theory would distinguish between the cases in which I am being uniformly accelerated through a gravitation-free region and in which I am at rest in a homogenous gravitational field, Einstein maintains that there is in fact no difference between these two cases. This is (one version of) the Principle of Equivalence.
Note that Einstein does not say is that 'we choose between the competing descriptions of the magnet-and-conductor case on pragmatic grounds,' or that 'we parse the causes differently: either as an electromotive force or as a electric field.' Rather, he re-arranges the permitted causal structures of the theory to eliminate these pseudo-differences, so that the theory no longer "leads to asymmetries which do not appear to be inherent in the phenomena." He replaces the separate categories of 'inertial effects' and 'gravitational effects' with a single category (which we could call gravitational-inertial effects) via his principle of equivalence.
What I am curious about is whether Einstein's maneuver can be carried over into the biological case. I am hoping someone better-informed than I am can tell me why this has no prayer of working, or why Einstein's cases are not analgous to the situation in evolutionary biology. Of course, I wouldn't mind hearing suggestions for how this might work, either.
Editorial note. Posting here will probably be sporadic for the next few months: I am going on the job market this year, and that process has been (and, I imagine, will continue to be) time-consuming.