Archaeological research has used the science of isotopic analysis in order to trace the mobility of people in the past and reconstruct aspects of their diet. This type of analysis, when applied on human remains - bones and teeth – can be used to distinguish individuals that are local to the place of their burial from individuals that are not, and reveal information about their food preferences.
Understanding the migrations and mobility patterns of people, either in a macro-scale (population movement) or in a micro-scale (individual movement), can be very important for understanding past societies. On an individual level, isotopic studies can reveal valuable information on an individual’s place of birth, while on a population level they can help in the reconstruction of the diversity of past communities.
Isotopes are different variants of a chemical element, with the difference being in the number of neutrons they have. The purpose of isotopic analysis of a human bone or tooth is to identify its isotopic signature (the ratio of different isotopes of a specific element). Isotopic analyses in archaeology commonly use strontium, oxygen, carbon and nitrogen isotopes.
Strontium isotope analysis is the most common in studies of mobility, as strontium from the local environment passes into the food web and is consumed by animals and people. According to the principles of isotopic analysis, the remains of every local individual, consuming food from local resources should have a strontium isotope ratio close to those calculated for that region. Later, this individual’s isotope ratio is compared with the isotopic signatures of the area that it was found, as well as other regions, to identify the one that is the closest to.
Oxygen isotope values of human skeletal tissues mainly reflect the individual’s body water isotope composition, which in turn, consists of the consumed drinking water – probably derived from local water sources for most communities in the past. The same principle applies to oxygen isotopes as strontium isotopes, whereby local individuals are expected to have similar oxygen isotope values to the local environment.
For both strontium and oxygen isotopic analyses of archaeological skeletal remains, the human dental enamel is preferred, as it is the most resistant part of the human skeletal. Also, it does not change during someone’s lifetime, so it preserves the isotope composition of the place of the individual’s childhood (Laffoon 2012, 8). This way we can know if people were born in the same place where they died or not.
Text by Eleni Seferidou, based on original published research (see further reading).
Photo: Gareth Davies and Laura Font preparing human teeth samples for isotope analysis in the mass spectrometry lab at the Free University, Amsterdam.The study of strontium isotopes offers new perspectives to better reconstruct the migration and mobility of Indigenous peoples in the Caribbean (photo: Advalvas, VU magazine).
Laffoon, J. E., 2012. Isotopic research in the Ancient Caribbean. Phd diss., Leiden University.
Laffoon, J. E., Davies, G. R., Hoogland, M. L. and Hofman, C. L., 2012. Spatial variation of biologically available strontium isotopes (87Sr/86Sr) in an archipelagic setting: a case study from the Caribbean. Journal of Archaeological Science, 39(7), 2371-2384.
Laffoon, J. E., R.V. Rojas and Hofman, C. L., 2013. Oxygen and carbon isotope analysis of human dental enamel from the Caribbean: implications for investigating individual origins. Archaeometry, 55(4), 742-765.