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

Stable carbon (delta C-13) and nitrogen (delta N-15) 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 delta C-13 and delta N-15 vary between bone types within a single individual, or if this variation corresponds with bone turnover rate (BTR). Here, we determined delta C-13 and delta N-15 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 (delta C-13: max = -1.58 parts per thousand; delta N-15: max = 3.05 parts per thousand). 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 delta N-15. 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. (C) 2017 Elsevier Ltd. All rights reserved.