Monday, 20 May 2013

Kin selection as correlated selection

Steven Frank ("Natural selection. VII. History and interpretation of kin selection theory." Journal of Evolutionary Biology 26, in press) sorts out kin selection, group selection, inclusive fitness, direct fitness and all that. While he lucidly explains how correlated selection subsumes all the above concepts as special cases, including genetic relation as one cause of correlation, he stops short of calling the general theory correlated selection. That's because he's interested in understanding the underlying processes and not in squabbling about labels.

Of particular interest to those who followed the recent kerfuffle about a paper by Nowak et al. (2010 "The evolution of eusociality." Nature 466: 1057-1062) will be the following comments revealing a position between the quarreling parties:
"In my view, inclusive fitness has become as much a hindrance as an aid to understanding. I am not saying that inclusive fitness is wrong. Inclusive fitness does provide significant insight into a wide variety of problems. But one must know exactly its limitations, otherwise trouble is inevitable. Realistic biological scenarios arise for which inclusive fitness is important but not sufficient. When one does not clearly recognize the boundaries then, when faced with a solution for which inclusive fitness is not sufficient, it becomes too common to conclude that inclusive fitness and all broader approaches to kin selection analysis fail entirely, and one must discard the whole theory." Frank (in press, p. 21) 
Clearly, Frank is not on the side of those defending inclusive fitness as the general theory with kin and group selection as special cases. He even favors the direct fitness approach. At the same time, however, the statement about throwing out the baby with the bath water (last sentence in above quote) is a criticism of Nowak et al. (2010). Here's another quote showing how Frank conceives the relation between direct and inclusive fitness:
"Direct fitness typically provides a clear and complete analysis, and subsumes inclusive fitness as a special case. Inclusive fitness does have the benefit of an intuitively appealing causal perspective. However, inclusive fitness is more limited and more likely to cause confusion. As understanding of a subject develops, it is natural for yesterday’s general under- standing to become today’s special case." Frank (in press, p. 22)

By the way, Frank sees group selection as equally hindering understanding (p. 23 onwards).

In summary, this could clear up some of the mess around the group/kin selection controversy, but it is confusing that Frank uses the term kin selection as a label for the general theory that comprises all the special cases. After all, kin implies genetic relationship and he clearly does not want to see the theory limited in that way. I'd favor correlated selection as a neutral alternative term.