Bone collagen is a common material used for stable isotope analysis in archaeology, palaeontology, and ecology to generate insights about an individual's life history. The extent of intra-bone isotopic variation has generally been assumed to be small, and bone sample size is minimized to avoid unnecessary sample destruction. In this study, we extracted hundreds of subsamples ( n = 1226) from various regions of the midshaft of two kangaroo tibiae and two cattle radii to systematically assess the extent of isotopic variation in bone collagen δ 13 C and δ 15 N within a single skeletal element. We found that within a single element, δ 13 C varied by up to 10.6 ‰ and δ 15 N by up to 3.6 ‰. Isotopic variation within an element likely reflects the range of isotopic compositions of foods that were regularly consumed throughout life, with variation in remodeling rates throughout the bone driving intra-element isotopic variation. As bone sample size decreases, the probability of obtaining an isotopic composition that differs significantly from the lifetime average increases. Rather than conceptualizing stable isotope measurements from bone collagen as being akin to those derived from tissues such as muscle, liver, or skin, they may be better understood as being similar to sequentially sampled hair or tooth samples that have lost their specific temporal information. • Long-bone collagen was incrementally sampled at high spatial resolution to assess extent of isotopic variation. • Within a skeletal element, δ 13 C varied by up to 10.6 ‰ and δ 15 N by up to 3.6 ‰. • δ value variation within bones may reflect remodeling rate patterns, and should be further researched. • Taking larger or multiple bone samples helps ensure δ values accurately reflect long-term average dietary intake.
Hall et al. (Sun,) studied this question.