Directional and fluctuating asymmetry in the palmar interdigital ridge-counts

Directional and fluctuating asymmetry of the palmar interdigital ridge-counts (c-d, b-c and a-b) was evaluated using a sample of 1186 male and 1042 female Germans. The c-d and b-c ridge-counts show higher right side values while the a-b count shows a higher left side value. Sex differences in asymmetry are significant, females exhibiting larger left values than males for all three counts. Directional asymmetries of the different areas exhibit weak negative correlations. Fluctuating asymmetry (magnitude of L-R) is highest for the c-d count, followed by the a-b. Both c-d and a-b ridge-counts exhibit a significant quadratic relationship between magnitude of L-R and R+L, but b-c does not. The quadratic relationship shows that individuals with extreme phenotypes are more asymmetrical than those closer to the mean. This in turn may be interpreted to mean that fluctuating asymmetry is a reflection of developmental stability.