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Bone deep: Variation in stable isotope ratios and histomorphometric measurements of bone remodelling within adult humans

Fahy, G.E., Deter, C., Pitfield, R., Miszkiewicz, J.J., Mahoney, P.
Journal of archaeological science 2017 v.87 pp. 10-16
archaeology, bone metabolism, carbon, death, diet, females, femur, human nutrition, males, metacarpus, nitrogen, regression analysis, ribs, skeleton, stable isotopes
Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope studies of ancient human diet increasingly sample several skeletal elements within an individual. Such studies draw upon differences in bone turnover rates to reconstruct diet during different periods of time within an individual's lifetime. Rib and femoral bone, with their respectively fast and slow remodelling rates, are the bones most often sampled to reconstruct shorter and longer term signals of diet prior to death. It is poorly understood if δ¹³C and δ¹⁵N vary between bone types within a single individual, or if this variation corresponds with bone turnover rate (BTR). Here, we determined δ¹³C and δ¹⁵N for ten different bones from ten adult human skeletons (n = 5 males; n = 5 females). Isotope values were compared to the rate that each bone remodeled, calculated from osteon population (OPD) density. Results reveal that isotope ratios varied within each skeleton (δ¹³C: max = −1.58‰; δ¹⁵N: max = 3.05‰). Humeri, metacarpals, and ribs had the highest rate of bone remodelling; the occipital bone had the lowest. A regression analyses revealed that higher rates of bone remodelling are significantly and negatively correlated with lower δ¹⁵N. Our results suggest that the occipital bone, with its slow rate of bone renewal, may prove useful for isotopic studies that reconstruct diet over longer periods of time within an individual's lifetime. Isotope studies that compare individual skeletal elements between populations should standardize their methodology to bones with either a slow or fast turnover rate.