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Constructing A New Incremental Isotopic Methodology For Human Dental Enamel: A Preliminary Examination

Authors:

Abstract

The application of incremental enamel sampling on human dental enamel allows researchers to observe how isotopic values may vary over an individual’s early life. For archaeologists, this means we can observe how an individual’s diet and geographical mobility may have changed over time. Currently, incremental isotope studies on human enamel primarily use in-situ techniques, which while allowing for small and targeted analysis, are limited in access, precision or applicable isotopes. An alternative is the use of micro-milling techniques, which are more accessible and cost-efficient. Whilst milling techniques are commonly used on faunal dental enamel (i.e., sheep and cattle), the amelogenesis process in human dentition is shorter and more intricate. As such, placing enamel increments, removed by milling, into a chronological order is difficult without the knowledge of that tooth’s specific growth pattern. Whilst the construction of such a methodology is challenging, it is essential to investigate if incremental milling techniques can be viable on human dental enamel, to enable high resolution dietary and mobility reconstructions for humans. The aim of this study is to produce an incremental sampling technique for the enamel of human molars and canines, to reveal variations in strontium (Sr), oxygen (O), and carbon (C) isotopic ratios during the tooth enamel formation period. This technique uses milling guided by thin-sections of the enamel to ensure a developmentally informed sampling strategy. Preliminary results from a combination of both modern and archaeological samples reveals a promising indication that enamel increments can be successfully sampled along a human tooth enamel growth axis. However, the growth pattern of human tooth enamel limits the number of increments that can be milled in a resolvable time series. As such, this study provides a critical evaluation of the proposed technique, and a plan of how to increase the resolution of the methodology in our future research. This project is supported by the European Research Council: LUMIERE - Landscape Use and Mobility In EuRopE - Bridging the gap between cremation and inhumation (Agreement No. 948913
Constructing a New Incremental Isotopic Methodology for
Human Dental Enamel: a Preliminary Examination.
Jacob I. Griffith1,2, Hannah F. James1,2, Hai-Yen Tran3, Barbara Veselka1,2, Christina Cheung1,2, Hugues Gregoir3,4, Christophe Snoeck1,2
1Analytical, Environmental & Geo-Chemistry, Department of Chemistry, Vrije Universiteit Brussel, Belgium.
2Maritime Cultures Research Institute, Department of Art Sciences and Archaeology, Vrije Universiteit Brussel, Belgium.
3Faculty of Medicine, Université Libre de Bruxelles, Belgium
4Belgian Disaster Victim Identification (DVI) Team, Belgium.
Jacob I. Griffith
Jacob.Griffith@vub.be
Orcid:
0000-0002-2585-7233
Contact 1. Wright, L. E. 2013. Examining childhood diets at
Kaminaljuyu, Guatemala, through stable isotopic
analysis of sequential enamel microsamples.
Archaeometry 55, 113-133.
2. Plomp, E., von Holstein, I.C., Kootker, L.M.,
VerdegaalWarmerdam, S.J., Forouzanfar, T. and
Davies, G.R. 2020. Strontium, oxygen, and carbon
isotope variation in modern human dental enamel.
American Journal of Physical Anthropology 172,
586-604.
3. Reid, D.J. and Dean, M.C., 2006. Variation in
modern human enamel formation times. Journal of
human evolution 50, 329-346.
References
Introduction
Canine Iso-Biographies:
Discussion
The following steps are planned to improve the
sampling methodology:
Increase the increment count per-canine and
molar.
Continued analysis of the enamel growth pattern
to better understand the time resolution of, and
in-between, extracted increments.
Future Work
Canine Iso-Biographies
@JBioarch
Acknowledgments
This research is supported by the ERC Starting Grant
LUMIERE (Landscape Use and Mobility In EuRope
Bridging the gap between cremation and inhumation), funded
by European Union’s Horizon 2020 research and innovation
programme under grant agreement number 948913.
Aim: Construct a new hand-milling incremental
sampling protocol to reveal variations in C, O, and
Sr isotopic ratios during the enamel formation
period of human molars and canines.
Sample population: Modern-archaeological
individuals from Charleroi municipality, Belgium.
Preliminary analysis performed on ID:5365 as
87Sr/86Sr bulk values from the M1 (0.7123) and
M3 (0.7110) indicate early-life geographical
mobility.
Incremental isotopes on successional forming
teeth indicate when individual 5365 migrated
into a new geological region.
Milling was guided by thin-sections of the
enamel growth pattern (Striae of Retzius).
Incremental molar sampling methodology
adapted from Wright (2013) and Plomp et al.
(2020).
Iso-Biography: 5365
Canine Incremental Sampling
The iso-biography of individual 5365 demonstrates that intra-tooth
87Sr/86Sr, δ13Cand δ18O variation can be tracked successionally across
three enamel increments of both molars and canines.
The application to canine is novel and was constructed using microscopy
Standardised increment locations were plotted on the enamel growth axis.
Cuspid enamel formation is less overlying than in molars, making selected
increments less likely to over-lap in their time series.
The methodology was re-applied to four individuals.
Microscopy image of
the Striae of Retzius
used to guide sampling
Iso-biographies provide further evidence that
successional isotopic variations can be obtained
from the enamel of human canines through
hand-milling.
Intra 87Sr/86Sr canine values correlate with the
bulk values observed in the M1s and M3s
Intra-tooth variation is also observed in δ13C and
δ18O.
Implications
As enamel growth represents 1.5 years to 5/6
years (Reid & Dean 2006), geographic mobility
and diet can be reconstructed over this period of
early life.
Canine’s form simultaneously to M2s, meaning
they can be utilised in their absence.
Canines are not as usually as worn as molars
and maintain more of the isotopic series
Current Limitations
Limited powdered enamel per-increment often
means that some δ13C and δ18O values cannot
be measured in duplicate
Though increments can be placed in
successional formation,and the age difference
between the increments can be suggested (Reid
& Dean 2006), increments cannot yet be
associated with a specific age.
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