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

Abstract

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. © 1999 Wiley‐Liss, Inc.

Canalization, developmental stability, and morphological integration in primate limbs

“…In other words, the mechanisms behind canalization and developmental stability are closely related. This conclusion is at odds with claims made in other studies which examined the relationship between phenotypic variance and FA in suites of traits (Debat et al, 2000;Reddy, 1999). Neither of these studies, however, examined the relationship between heritability and FA.…”

“…Canalization has not been extensively studied in humans and other primates. A few studies have addressed the relationship between phenotypic extremeness and fluctuating asymmetry (FA) in humans (Livshits and Smouse, 1993;Reddy, 1999). Reddy (1999) argued that the frequent failure to demonstrate such a relationship implies that developmental stability and canalization are decoupled.…”

“…In contrast to canalization, a fair amount of work has been done by biological anthropologists on developmental stability. Some of these studies have been attempts to understand the causes of FA from patterns at the morphological level (Corruccini and Potter, 1981;Hallgrímsson, 1993Hallgrímsson, , 1999Jantz and Webb, 1980;Reddy, 1999;Saunders and Mayhall, 1982). Others have addressed the relationship between FA and heterozygosity (Comuzzie and Crawford, 1990;Corruccini and Potter, 1981;Hutchison and Cheverud, 1995;Kobyliansky and Livshits, 1989;Livshits and Kobyliansky, 1991) with conflicting results.…”

Effect of inbreeding depression on growth and fluctuating asymmetry in Turkish young males

“…FA has been used as an indicator of individual quality and developmental stability in studies of natural and sexual selection. Research conducted on different species showed that overall FA to be higher in inbred populations than in outbred populations (e.g., Ben-David et al, 1992;Carter et al, 2009;Mukherjee, 1990;Reddy, 1999;Schaefer et al, 2006), but some others have not confirmed this trend (e.g., Fowler and Whitlock, 1994;Kruuj et al, 2003; for review see Vøllestad et al, 1999).…”