Isotopes are atoms of different weights of a specific element, based on the different number of neutrons in the nucleus. The analysis of stable isotopes such as carbon, nitrogen, sulphur, strontium, and oxygen can be used to study past human diet and mobility. Isotopes enter our bodies from what we eat and drink and are incorporated into the bones and teeth at different times in the life cycle. Bones are remodeled during an individual’s lifetime and the isotopes in bone collagen will reflect at least the last 10 years of an individual’s life. Isotopes in dentine or enamel of teeth are incorporated when the tooth is formed so the individual’s age for the event varies dependent on the tooth, as well as on which part of the tooth is analyzed. This way an individual’s diet can be assessed at different life stages depending on the items analyzed.
Human food choices are culturally defined in an environmental framework, with dietary patterns being highly dependent on ecological constraints, particularly in the case of past populations. Carbon and nitrogen stable isotope analysis of human remains from archaeological contexts is a scientific method widely used for assessing past dietary patterns. The method is based on the observation that the isotopic composition of human tissue, such as bone collagen or tooth enamel, largely reflects that of dietary protein. Additionally, the method recognizes that classes of dietary resources (i.e., plants, herbivores, omnivores and carnivores) have characteristically different isotopic ratios, and present a systematic difference between the isotopic composition of the consumer and the ingested food resource (i.e., fractionation factor).
The comparative analysis of dietary patterns can reveal social aspects of the lifeways of past populations. This is highly relevant for archaeological research because it offers a tool to discuss past relations to food at various levels, such as weaning, gender and age, culture, group identity, and differential access to food resources.
Strontium, sulphur and oxygen isotopes can be used to study mobility by the identification of local and extra local (migrants) in an archaeological context.
Of importance for all of these types of analyses is to have a local and temporal reference panel of terrestrial, marine and lacustrine fauna, as well as signatures of the local bedrock and water in the case of strontium and oxygen isotopic analyses.