by Lana Williams
American Journal of Physical Anthropology 145: 125-136 (2011)
Co-authored with CD White & FJ Longstaffe
A recent trend in stable isotopic analysis involves the reconstruction of short-term variations in diet using hair... more
A recent trend in stable isotopic analysis involves the reconstruction of short-term variations in diet using hair segments. However, bulk hair samples typically contain a growth cycle error, which may conceal or confound the most recently incorporated isotopic infor- mation. It is assumed that, at any given time, $85–90% of scalp hairs are actively growing, while the remaining 10–15% have transitioned into a resting or inactive phase, which lasts up to 4 months before hairs are shed. This study uses growth phase to determine the effects of age, sex, and health status on carbon and nitrogen isotopic ratios of hair analyzed in sequential segments. For this study, we selected archaeological hair samples from 10 individuals from Dakhleh Oasis, Egypt. Isotopic analyses of actively growing hair segments were com- pared to those for mixed growth phase segments from each individual. These data demonstrate the presence of growth cycle error and show that an understanding of structural–functional relationships is essential for inter- preting normal versus pathological changes in hair fol- licle and fiber production. In situations where diet change and mobility produce variations in an individual’s isotopic composition, elimination of positional–temporal error in sequential segment hair analyses can facilitate greater understanding of intraindividual metabolic reactions and changes in hair growth cycles. Phase identification may aid in determining the presence of pathological conditions in individuals, especially in those lacking skeletal indica- tions, and provide a more precise estimation of seasonal dietary patterns, access to changing food resources, and metabolic equilibration to a new locality.
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