Problems of sampling and inference in the study of fluctuating dental asymmetry.

Randomly distributed or "fluctuating" dental asymmetry has been accorded evolutionary meaning and interpreted as a result of environmental stress. However, except for congenital malformation syndromes, the determinants of human crown size asymmetry are still equivocal. Both a computer simulated sampling experiment using a combined sample size of N = 3000, and the requirements of adequate statistical power show that sample sizes of several hundred are needed to detect population differences in dental asymmetry. Using the largest available sample of children with defined prenatal stresses, we are unable to find systematic increases in crown size asymmetry. Given sampling limitations and the current inability to link increased human dental asymmetry to defined prenatal stresses, we suggest that fluctuating dental asymmetry is not yet established as a useful and reliable measure of general stress in human populations.