Potential biases in sampling design and interpretation of intra‐tooth isotope analysis

Abstract

An increasing number of studies dealing with environmental and dietary reconstruction involve measurement of intra-tooth variation of isotope ratios. The sampling procedure typically consists of collecting a sequence of horizontal bands perpendicular to the growth axis of the tooth. The objective is to obtain a temporal sequence of the changes recorded in dental tissues during tooth development. This paper examines some issues associated with this sampling strategy and consequences for interpretation of the data. Time resolution is influenced by the pattern and duration of enamel mineralization, in a way that might, however, depend on the species and the tooth analysed. Although it may be impossible to sample discrete amounts of time, a chronological order seems to be respected, which should be well enough when the objective is to detect changes in isotope ratios with time. Absolute data must be interpreted with caution. Such issues do not affect studies of inter-individual variability as long as the sampling procedure applied to the compared specimens is consistent.A new sampling strategy is tested on modern goat teeth, involving drilling in an oblique direction. The results obtained from obliquely drilled samples are very similar to those obtained from the horizontal sampling procedure. More work is still needed to determine the value of alternative sampling strategies.

Seasonality and season of birth of modern and late Neolithic sheep from south-eastern France using tooth enamel δ18O analysis

“…Sequential sampling was performed in order to reconstruct the isotopic history of the individual over the time of tooth development (Balasse 2002(Balasse , 2003Balasse et al 2002Balasse et al , 2003Fricke & O'Neil 1996;Kohn et al 1998;Sharp & Cerling 1998). Tooth surfaces were cleaned by abrasion.…”

Isotopic paleoecology of Clovis mammoths from Arizona

“…A, C, E, and F are midcrown or cervical portions of the tooth, whereas B and D are developing enamel cones, which formed closer to the time of death. drilled on the inner enamel surface (IES), which records a "time series" of isotopic compositions with less damping of seasonal amplitudes than traditional approaches (49,50). Specimens were mounted on drill plates with the IES facing up, and lines were drilled on the IES in the distal-mesial direction, perpendicular to the height of the tooth, using a Merchantek MicroMill (25).…”

Reconstructing seasonality using d18O in incremental layers of human enamel: a test of the analytical protocol developed for SHRIMP IIe/MC ion microprobe

“…It is nec es sary to con sider a more complex di etary that can pro vide an ad di tional vari able ver sus con stant fac tors into the iso to pic re sults, e.g. the prob lem of d 18 O pre formed wa ter and met a bolic ox y gen in food (Bryant and Froelich, 1996), or mixed sur face wa ter col lects, which dampen the iso to pic vari a tion (Kohn and Cerling, 2002;Balasse, 2003). The hu man enamel does not per fectly fol low the "time --line" of bioapatite min er ali sa tion.…”

“…The iso to pic anal y sis of enamel has been used to study sea sonal di etary hab its of both mod ern and ar chae o log i cal fauna (Fricke and O'Neil, 1996;Stu art-Wil liams and Schwarcz, 1997;Fricke et al, 1998;Balasse, 2003;Blaise and Balasse, 2011;Stevens et al, 2011), how ever, se quen tial intra-tooth isoto pic vari a tion has re ceived lit tle at ten tion in the stud ies of archae o log i cal hu man re mains.…”

“…More over, the ox y gen iso tope com po si tion of enamel re mains fixed (i.e. enamel is no lon ger me tab o lized by the body), pro vid ing a nearly con tin u ous sta ble iso tope re cord that may cover a pe riod from months to years and that can be re tained for thou sands of years af ter fossil iza tion (Kohn and Cerling, 2002).The iso to pic anal y sis of enamel has been used to study sea sonal di etary hab its of both mod ern and ar chae o log i cal fauna (Fricke and O'Neil, 1996;Stu art-Wil liams and Schwarcz, 1997;Fricke et al, 1998;Balasse, 2003;Blaise and Balasse, 2011;Stevens et al, 2011), how ever, se quen tial intra-tooth isoto pic vari a tion has re ceived lit tle at ten tion in the stud ies of archae o log i cal hu man re mains.The ox y gen iso to pic com po si tion of hu man bioapatite is related to the iso to pic com po si tion of lo cal drink ing wa ter (Longinelli, 1984;Luz et al, 1984). In most lo ca tions, avail abil ity of po - Re con struct ing sea son al ity us ing d 18 O in in cre men tal lay ers of hu man enamel...…”