Determining isotopic life history trajectories using bone density fractionation and stable isotope measurements: A new approach

Abstract

A number of recent studies have attempted to trace diet at different stages of an individual's life by comparing isotope ratios of bone from different gross anatomical sites within the skeleton. In this study we develop this approach further by separating bone of differing mineral densities within one skeletal element, where each density fraction represents a different period of time. Isotope ratios are measured for these fractions. Each density fraction represents a period of bone formation and maturation, where younger (more recently formed) bone is less well-mineralized and therefore less dense than relatively older packets of bone. In an adult, bone is therefore able to partition approximately the last 15 years of life. Bone fractions were recovered by stepped ultracentrifugation in a series of organic solvents of increasing density, and then collagen was recovered by decalcification in dilute acid, and stable carbon isotope ratios ((13)C/(12)C) were measured. Bone density microstructure was checked for bacterial remodelling using backscattered electron imaging in a scanning electron microscope. Our results indicate that the bone density fractionation method is applicable to archaeological material, here extending to a maximum of 5,000 years BP, and that collagen can successfully be extracted from such fractions. The carbon isotope values for bone fractions of different densities patterned out as expected in one modern control bone and in specimens from five archaeological human skeletons, including three precolonial hunter-gatherers and two 18th/19th century individuals. The latter two are known (from previous assessments) to have undergone marked changes in diet during their lifetimes. Postmortem alteration was evident in some of the specimens examined. The bone density fractionation approach has allowed greater resolution of diet than has hitherto been possible and has provided access to the elusive last years and months of an individual's life.

Reconstruction of breastfeeding and weaning practices using stable isotope and trace element analyses: A review

“…Many osteons and packets of differing ages or maturation states exist together in one bone element, and the mineral density of younger ones are lower than that of older ones (Fratzl et al, 2004). Bell et al (2001) separated fractions of differing mineral densities within one skeletal element, in which each density fraction represented a different period of time, and applied stable carbon isotope analysis to collagens extracted from these fractions. Although they did not reconstruct BWPs, their analyses of one modern bovine bone and five archaeological human skeletons indicated that this method is potentially valuable for investigating dietary changes over years.…”

“…Although they did not reconstruct BWPs, their analyses of one modern bovine bone and five archaeological human skeletons indicated that this method is potentially valuable for investigating dietary changes over years. The methods proposed by Waters-Rist et al (2010) and Bell et al (2001) are partial if not thorough solutions for the osteological paradox in BWP reconstruction. In BWP reconstruction, these methods are only applicable to subadult bones because the macro-and microstructures of bone reflecting diets in infancy would not remain until adulthood as a result of the continuous remodeling of bone (Hedges et al, 2007;.…”

Mapping Human Movement using Stable Oxygen Isotopic Ratio Mass Spectrometry: Potential Application to Forensic Science Demonstrated by a Modern Horse-Human Study

“…However, this type of signature is geographically crude as an indicator of movement, but one that might be usefully exploited amongst other isotopic signatures. New methodologies concerning temporal sampling of the incremental tissues of bone and teeth have been developed (11)(12)(13) including the recovery of bone collagen formed close to death (14).…”

Modified Bone Density Fractionation Method for Palaeodietary Studies

“…Herman and Richelle 8 first introduced the density fractionation method, which is a well-established method in mineral analysis, to modern bone and dental tissues with respect to age, nutrition and disease using mixtures of toluene and bromoform. Bell et al 9 drew the idea of fractionating bone density from a contemporary biomedical research tool to archaeological bone. 10 They applied this method to bones, which are known to undergo significant diet change during their lifetime.…”

“…In order to apply the bone density fractionation method to palaeodietary research, two main factors should be assured: the factors influencing density differences and those related to obtaining reliable particle size. First, differences in bone density may occur for two main reasons, i.e., bone maturation caused by metabolism in vivo 9,12 and exogenous mineralization caused by microbacterial attack after burial. 13,14 The increase in bone density in vivo is closely related to bone formation and maturation, during the continuous remodelling of bone that occurs throughout life.…”