FLUCTUATING ASYMMETRY AND
THE 2ND: 4TH DIGIT RATIO IN
I have always found it advantageous to keep an empirical project going alongside whatever theoretical work I am trying to do, fieldwork, for example, in Jamaica. It provides several kinds of relief from the theoretical work and gives you something to do when you are not otherwise particularly creative. In any case, as an early graduate student at Harvard, I watched pigeons in my spare time and then studied lizards as part of my thesis (and as a means of visiting Jamaica frequently). In more recent years, most of my academic position being in an anthropology department, I have tried to study our own species. In particular, in January 1996 with a team of scientists and students, we measured nearly three hundred school children in Jamaica from head to toe for degree of bodily symmetry. We are especially interested in each individual's degree of fluctuating asymmetry and differences between traits in degrees of fluctuating asymmetry. My interest in this topic came about in the following way.
In 1990 Bill Hamilton visited the University of California at Santa Cruz to deliver a talk. Since he had done the most exciting piece of work on sexual selection in the 1980s—namely, work suggesting that a key aim of mate choice in many species is to identify relatively parasite-resistant genes via degree of development of such secondary traits as bright color and complex song—I said to him, “What's new in sexual selection, Bill?” Hamilton replied, “Fluctuating asymmetry. ” I said, “Fluctuating who?” and he repeated, “Fluctuating asymmetry. ” I had never heard the term before.
Fluctuating asymmetry refers to minor deviations from perfect bilateral symmetry (in bilaterally symmetrical species) that vary randomly from right to left and tend in a population to cancel out and give true symmetry. In other words, the trait lacks and directional bias in the population. Hamilton directed me to a paper just published by the great Danish ornithologist