Fluctuating asymmetry and canalization: An appraisal based on a-b ridge counts among Indian populations with diverse...

The relationship between fluctuating asymmetry, measured as the absolute difference between the right and left a-b ridge counts, and total a-b (R + L) ridge count was studied in an assortment of Indian population samples representing a wide spectrum of socioeconomic and occupational backgrounds. They included marine fishermen, inland and estuarine fishermen as well as migrants and their parental counterparts, tribes, and castes of different hierarchy- lower, middle, and upper. The samples together numbered a total of 3,239 subjects, 2,240 males and 999 females. The results failed to support Jantz and Webb's (1980) hypothesis of a quadratic relationship between fluctuating asymmetry of a-b ridge count and its phenotypic value. Only 3 of 22 samples (about 13%) showed a significant fit with a reasonable degree of consistency over a set of independent random subsamples; even initially only 7 of 22 (about 30%) samples showed a significant fit, or nearly so. Supplementary evidence drawn from these populations with reference to the relationship between fluctuating asymmetry and heterozygosity levels and inbreeding coefficients was also consistent with the interference that fluctuating asymmetry of a-b as it is measured and examined at the population level does not reflect canalization. Am. J. Hum. Biol. 11:367-381, 1999. Copyright 1999 Wiley-Liss, Inc.