Strontium isotope analysis for studying the mobility of ancient populations
Reading time:
Written by:
The movements of ancient populations can be studied through the analysis of isotopes present in bones and teeth. Among these, strontium is an interesting indicator for researching an individual's geographical origin and determining if they changed regions during their life. Indeed, by comparing the isotopic signature of human remains to that of their environment, scientists can thus better understand the mobility of ancient populations and their relationship with their territory.
In summary:
- Strontium isotope analysis makes it possible to study the geographical origin and mobility of ancient populations.
- Strontium present in bones and teeth preserves information about the environment in which an individual lived.
- Comparing the isotopic signatures of human remains with those of the environment helps to identify potential displacements during life.
- The analysis of teeth and bones allows us to study different periods of an individual's life.
- The interpretation of the results relies on environmental references and the archaeological context.
How does strontium help study the geographical origin of individuals?
Strontium is an element naturally present in rocks and sediments. Through erosion, it ends up in soils, water, and food resources, and is then incorporated into the tissues of living beings. The ratio between strontium isotopes, particularly strontium 87 and strontium 86 (⁸⁷Sr/⁸⁶Sr), varies according to the geological characteristics of regions. This variation constitutes an isotopic signature that can be compared between archaeological remains and the studied environments.
Strontium analysis in bones and teeth thus makes it possible to determine whether an individual's signature is compatible with that of the region where they were discovered or with that of other territories. It helps to study the geographical origin of individuals, their movements during their lives, and mobility within a group.
This interpretation, however, requires suitable reference data. An isotopic signature does not necessarily correspond to a unique region: several territories can exhibit similar values.
Why analyze bones and teeth?
Bones and teeth are frequently studied in archaeology because their mineralized tissues can be preserved for a long time. However, they do not record the same periods of an individual's life. They are also complementary for studying individual trajectories and the movements of ancient populations.
Bones: information on the final years of life
Bone is made up of an organic matrix, mainly composed of collagen, and a mineral matrix, composed notably of calcium phosphates. It is a living tissue that remodels itself throughout life.
The isotopic composition of bone can therefore reflect, to some extent, the environment to which the individual was exposed in the years preceding their death. The period represented varies depending on the bone studied, the area sampled, and the individual's characteristics.
Teeth: a window into childhood
Teeth are also made of organic and mineral matter. However, dental enamel does not regenerate after its formation. Its isotopic composition thus preserves information about an individual's environment during the tooth's formation period. Comparing the isotopic signatures of dental enamel and bone from the same individual can therefore help identify a change in environment between childhood and the later years of life.
How does a strontium isotope analysis proceed?
Strontium isotope analysis relies on measuring the ratio of ⁸⁷Sr to ⁸⁶Sr isotopes in archaeological remains, and then comparing the results with environmental isotopic signatures. Reference data can come from rocks, soils, sediments, water, or biological resources representative of the studied territories.
The selection of samples depends on the scientific question, the nature of the available remains, and their state of preservation. Bones and teeth are particularly interesting, as they can preserve information about different periods of an individual's life. Sampling is adapted to the tissues studied and the objectives of the analysis, while ensuring the archaeological remains are preserved as much as possible.
What methods are used to analyze strontium?
The measurement of strontium isotopic ratios can be carried out using different mass spectrometry techniques, depending on the desired precision and the nature of the samples. Multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) notably allows for the precise measurement of strontium isotopic ratios.
Laser ablation coupled with mass spectrometry (LA-ICP-MS), in turn, allows for the analysis of targeted areas of a sample. Applied to dental enamel, this technique can be used, in particular, to study variations in isotopic signatures between different areas formed at distinct times in an individual's life. The choice of method and protocol depends on the question being studied, the type of remains, and the information sought. Appropriate reference materials allow for quality control of measurements.
At CIRAM, strontium isotope analysis is part of our archaeometry expertise. Our teams implement analytical methods adapted to samples and scientific issues in order to contribute to the study of the geographical origin and mobility of ancient populations.
Share this article
Are you perhaps asking yourself these questions about strontium?
This method applies in particular to the study of burials, funerary sites, and ancient populations. It helps researchers explore mobility practices, exchanges between communities, and the relationships between populations and their territories.
Yes. Interactions with soil, water, or certain preservation treatments can alter the chemical composition of bones and teeth. Laboratories must therefore assess the state of preservation of the samples and adapt their preparation protocol to limit the risk of contamination.
Yes. These two methods provide different and complementary information. Carbon-14 allows for estimating the age of an organic remnant, while strontium helps in studying the geographical origin of an individual. Combining them helps to place individuals in their chronological and geographical context.
No. Feasibility depends in particular on the nature of the available tissue, its state of preservation, and any potential contamination. Teeth, enamel in particular, often constitute interesting mediums, but each sample requires a prior evaluation.
Related topics
Need more information or have a question?
Our team will get back to you as soon as possible.
