Age-related variation in isotopic indicators of diet at medieval Kulubnarti, Sudanese Nubia

This study compares trends in dietary composition in two large cemetery populations from the site of Kulubinarti (AD 550-800) in Sudanese Nubia, Bone collagen and bone apatite carbonate were analysed to characterise stable carbon, nitrogen and oxygen isotopes. Previous research on these cemeteries has suggested marked differences in nutritional status and health between the populations. Contrary to expectations, there were no significant relationships between any isotopic indicators related to sex or cemetery of burial, suggesting no isotopically-measurable differences in diet. However, collagen delta C-13 and delta(IN)-I-15 were significantly related to age, suggesting age-related differences in protein intake or other factors. Weaning trends are gradual and variable, with the range in delta N-15 values exceeding 4%, among infants/young children (0-3yrs) and standard deviations exceeding 1 parts per thousand in collagen (C-13 and delta N-15 for both infants/young children and subadults (4-17yrs), This suggests varied wearing strategies among both populations and variable diets prior to adulthood. Also observed was a distinct range of isotopic carbon and nitrogen values among individuals classified as subadults (4-17yrs), who are depleted in collagen delta C-13 and delta N-15 relative to adults. However, both infants/young children and subacults are slightly enriched in delta O-18 relative to adults, which suggests the presence of non-local individuals or age-rolated variation in water sources. While most isotopic studies of age-related dietary trends have focused on reconstructing the weaning process, this study presents findings that indicate tripartite isotopic trends distinguishing infancy, subadulthood and adulthood as separate dietary categories. Broad similarities are evident between the results presented here and those from several earlier studies of smaller populations and to nutritional studies of modern communities, These findings suggest that further research into health disparities at Kulubnarti should focus on non-dietary causal factors, and more generally, that greater attention should be paid to subadulthood in palaeodiet studies. Copyright (c) 2006 John Wiley & Sons, Ltd.