The age-related distribution of dental indicators of growth disturbance in ancient lower nubia: an etiological model from the ethnographic record

The etiology of growth disturbance in early childhood is complex. Since skeletal indicators of growth disturbance are non-specific, attempts to understand this syndrome in ancient populations must rely on a biocultural approach. This paper presents a biocultural approach to data from Lower Nubia. Accentuated striae of Retzius, an indicator of disruption in enamel formation, are used to determine the age-related distribution of growth disturbance in two ancient Lower Nubian populations. This data is then discussed in the context of a modern Sudanese analogy. The sample consists of 105 first permanent molars (M1) from the Meroitic (100 b.c. to a.d. 300) and X-Group (a.d. 300 to 600) periods. Etched ground sections were made, and the location of accentuated striae along the dentioenamel junction (DEJ) was determined for the mesiobuccal and distolingual cusps. Location scores were converted to percentages of DEJ length, and compiled into frequency distributions. Published ages for M1 crown completion were then used to develop an age scale. Age-segments, each comprising 20% of M1 crown development, were compared to determine age-related patterns of accentuated stria occurrence. Interpopulation comparisons were made with the Kolmogorov-Smirnov two-sample test. There is no significant difference in the age of accentuated stria formation between populations (for either cusp). Frequencies remain low during the first half-year of life, and then rise dramatically in the second year of life. Accentuated stria formation remains high during the major portion of the third year of life. A tentative reconstruction based upon previous ancient Nubian data and modern Sudanese data suggests that the second-year rise may reflect a weaning "crisis" occurring in the context of a pattern of multiparous reproduction, extended lactation, and infectious disease. Further research is needed before this hypothesis can be tested.