Bilateral asymmetry in skeletal growth and maturation as an indicator of environmental stress

This study examined the efficacy of bilateral asymmetry in epiphyseal union as an indicator of environmental stress affecting the skeleton. We compare d the extent of asymmetry in the postcranial skeleton between two cemetery samples excavated from Medieval Kulubnarti, Sudanese Nubia. Past studies ha ve strongly suggested that these ancient Nubians experienced environmental stress-the early Christian period (550-750 AD) population to a greater exte nt than the late Christian period (750-1450 AD) population. We hypothesized that if bilateral asymmetry is a reflection of stress, then it should be p resent or greater in the more stressed population, the early Christian peri od population, while absent or found to a lesser extent in the less stresse d population, the late Christian period population. We computed two mean values, representative of right-side and left-side epi physeal union, for each individual in both cemetery samples, and tested for significant differences. Bilateral asymmetry was significant in the combin ed cemetery sample of 90 individuals (P < 0.019). When cemetery samples wer e tested separately, bilateral asymmetry was significant for the early Chri stian period sample (P < 0.001), but not for the late Christian period samp le. There were no differences attributable to sex. Finally, we discuss why we conclude that environmental stress was favored over a biomechanic explan ation as the cause for asymmetry. To the extent that our results support pr evious findings that early Christian period individuals were more affected by environmental stress than late Christian period individuals, it is reaso nable to consider bilateral asymmetry in skeletal growth and maturation a g ood indicator of environmental stress. (C) 1999 Wiley-Liss, Inc.