The Pith: The primary reason for the pervasiveness of sex among complex organisms is to maintain genomic integrity, not to increase genetic variation..

I just read a very strange article in the journal Evolution, Sex reduces genetic variation. In it the authors argue that contrary to conventional wisdom and evolutionary orthodoxy the rationale for the prevalence of sex amongst eukaryotic organisms is not maintenance of genetic variation, but rather a constraint upon genetic variation! This is a very peculiar view, and as someone not immersed in the literature on sex totally surprising to me.

The standard model is simple: sex allows organisms to swap genetic material and generate new combinations. This is at a particular premium for large, complex, and slow-breeding lineages, as is the norm amongst eukaryotes. In contrast, bacteria and their ilk have huge population sizes to draw from, and are quite literally protean in their ability to shift strategies to climb whatever adaptive landscape nature throws at them. Carl has a nice review of a paper in Science which reported just this finding in keeping with expectation. Increase the pathogen pressure, and eukaryotes which exchange genes marginalize those which do not because ...