HIGH ENTHUSIASM AND LOW R‐SQUARED

Asymmetry, Developmental Stability, and Evolution, by Anders P M0ller and John P Swaddle, is an enthusiast's guide to the idea that subtle deviations from perfect symmetry can indicate the quality of individuals, or of the environments they inhabit. M0ller and Swaddle argue that the value of these deviations as indicators of fitness is considerable, despite a body of evidence that the relationship is usually weak when it occurs, and is often undetectable. Population biology is periodically swept by such enthusiasms, by which I mean an idea which captures our imagination because it seems to explain a great deal, although it is supported by little confirmatory evidence. This jump to conclusions would not be a bad thing if our enthusiasms panned out more often, the way that, for example, the enthusiasm which greeted Watson and Crick has. However, in our field, yesterday's enthusiasm is more often today's cautionary tale about the complexity of the phenomena we try to explain. My own field of evolutionary genetics is unfortunately an example of this process. The central problem of what maintains the genetic variation essential to all evolutionary change is unsolved, despite more than century of work. Enthusiasms have arisen for mutation as the major source, then for genetic drift, then for overdominant selection, then for coadapted gene complexes, then for mutation-drift balance, for marginal overdominance, for mutation-selection balance, and well, you get the idea. Although this list is peculiar to my field, I trust that its recitation may bring a shudder of recognition to those in other fields. All this meandering is not without its good points. Enthusiasm can inspire critical tests of the new idea, or informative theorizing, increasing our understanding of the options. However, too many scientists are prepared to assume the validity of the latest idea rather than seek such critical tests. The result is that enthusiasm can have a distorting effect on a whole field, as it frequently leads to shoddy thinking and illmotivated research. There are always more people ready to don skinny ties or baggy pants when others do so than to take a hard look at their fit. My experience with scientific enthusiasm dates to my first days in graduate school, where I found my advisor in the grip of an enthusiasm for marginal overdominance as an explanation for allozyme polymorphisms. The data from some of the most active labs in the field was consistently revealing significant correlations between heterozygosity and whatever