You are what you eat
Isotopes have been used to trace the provenance of humans long before the Nexus1492 project came into being. The first archaeological application of strontium isotope analysis on human remains appeared during the mid-1980’s (Ericson 1985) and demonstrated the potential of isotope analyses as a tool to study the geographical origins of humans. Ever since, the archaeological studies employing isotope analysis have been multiplying. The forensic application of isotope analysis for human provenancing followed much later: see “The Adam case” (O’Reilly 2007), “The Scissors sisters case” (Meier-Augenstein and Fraser 2008), “The NN case” (Font et al. 2015). These studies use isotope analysis in bone, teeth and hair of unidentified deceased individuals in order to shed light on their geographical place of residence.
New Isotope Systems
Even though strontium isotope analysis has been a well-established method, the addition of (new) isotope systems, such as lead and neodymium, can provide more details on the area an individual originated from. Various studies have already stressed that a combined isotopic approach is the way to go forward (see Font et al. 2015). We’re currently working on the addition of new isotopic systems and improvement of already established methods at the VU Amsterdam.
With these advancements we will be able to aid the archaeologists within the NEXUS 1492 project to make more detailed interpretations of human mobility patterns. Also, applying these methods within the forensic context will aid to predict with higher accuracy the place of residence and recent movements of unidentified deceased individuals and it will therefore assist the police with the investigations.
Potential of Isotope Studies
The diverse isotopic systems that can be used for provenancing are all related to the isotope composition of the environment, which is transferred into the body through dietary intake, hence “you are what you eat”.
Strontium (Sr), lead (Pb) and neodymium (Nd) isotopes in human tissues reflect the isotopic signatures of the environment were the tissues formed. These ratios can be region specific, which is why we can use isotopes as a tracking tool for recent movements and areas of origin of humans.
The isotope composition of various human tissues provides information on different time periods of an individual’s life. The teeth record the isotope composition of the region of birth or later childhood, as teeth form during these periods. Bones record an average isotope composition of the region(s) of residence of the individual where the bone formed and remodelled. Different type of bones will remodel faster than others, relative to how compact they are. For example; ribs remodel faster (~4-6 years) compared to skull bone (~50 years).
Other tissues such as hair, that continuously grow at an average rate of 1cm/month, record the latest isotope composition of the region where the individual resided. Depending on the length of the hair, information from days to months can be recorded along hair strands. Variations in the isotope composition in human tissues are an indication that mobility and/or changes in diet occurred.
Isotope Studies within Nexus 1492
Within the 1492 Nexus project, only isotopes recorded in teeth are analysed, due to the alteration of the isotope composition of bone as a consequence of diagenetic processes (Bentley 2006).
Dr. Laura Font is applying the isotope methods within the forensic context in modern humans. Within the Nexus 1942 project, she is testing the applicability of lead isotopes in prehistoric teeth, to determine if lead isotopes contribute in improving the interpretations of human mobility within the Caribbean before the contact with Europeans.
Esther Plomp is currently testing whether we can use neodymium isotopes as a provenance tool for humans. Neodymium has been used to track the origins of archaeological artefacts, but has not yet been applied to human remains by other scholars. This is because the concentrations of Nd in teeth are much lower than Sr or Pb which complicates the analyses. She has proven that we can measure Nd isotopes in human teeth, contrary to what previous research has stated, but the method is still in development. After the method has been validated on modern material it will be applied to archaeological populations in the Caribbean.
By Esther Plomp and Laura Font
Bentley, R.A. 2006 Strontium Isotopes from the Earth to the Archaeological Skeleton: A Review, Journal of Archaeological Method and Theory 13 (3), 135-187
Ericson , J.E. 1985 Strontium isotope characterization in the study of prehistoric human ecology, Journal of Human Evolution 14 (5), 504-514
Font, L., G. Jonker, P.A. van Aalderen, E.F. Schiltmans and G.R. Davies. 2015 Provenancing of unidentified World War II casualties: Application of strontium and oxygen isotope analysis in tooth enamel, Science and Justice 55, 10-17.
Meier-Augenstein, W. and I. Fraser. 2008 Forensic isotope analysis leads to identification of a mutilated murder victim, Science and Justice 48, 153–159.
O’Reilly, W. 2007. The ‘Adam’ case, London. In T.J.U. Thompson and S.M. Black, eds. Forensic Human Identification: an Introduction. Boca Raton: CRC Press, 473-484