Isotope study suggests men and women had equal access to resources 6,000 years ago

Using isotopic geochemistry, a team from the University of Geneva (UNIGE) has revealed new information about the Barmaz necropolis in Valais (Switzerland): 14% of the people buried 6,000 years ago at this site were not local. What’s more, the study suggests that this Middle Neolithic agro-pastoral society – one of the earliest known in western Switzerland – was relatively egalitarian.

Carbon, nitrogen and sulfur isotope ratios found in the bones reveal that all members of the community, including people from elsewhere, had access to the same food sources. These results are published in Journal of Archaeological Science: Reports.

The Neolithic marked the beginning of animal husbandry and agriculture. In Switzerland, this period lasts between 5500 and 2200 BC. The first agro-pastoral communities gradually transitioned from a predatory economy – in which hunting and gathering provided the nutrients necessary for survival – to a production economy.

This radically changed the eating habits and functioning dynamics of Neolithic populations. The bones and teeth of individuals preserve chemical traces that scientists are now able to detect and interpret.

The aim of the study, carried out by Déborah Rosselet-Christ, a PhD student in the Laboratory of African Archeology and Anthropology at the UNIGE Faculty of Science, is to apply isotopic analysis to human remains dating from the Neolithic period and learn more about their diet and mobility.

The levels of certain isotopes of carbon, nitrogen, sulfur and strontium depend on the environment in which each individual lives and eats. Isotopes are atoms that have the same number of electrons and protons but different numbers of neutrons. This very precise and delicate technique is applied for the first time to alpine agro-pastoral populations from the Middle Neolithic period in the western part of Switzerland.

Mobility according to the second molar

The Barmaz site at Collombey-Muraz in the Chablais region of Valais, excavated in the 1950s and 1990s, is one of the oldest human remains of agro-pastoral societies in western Switzerland. It includes two necropolises containing the bones of about seventy individuals. Déborah Rosselet-Christ, the study’s first author, selected 49 of them (as many women as men) for her master’s degree, systematically taking collagen samples from certain bones as well as enamel fragments from their second molars.

“The second molar is a tooth whose crown forms between the third and eighth year,” explains the researcher.

“Once tooth enamel is formed, it does not regenerate for the rest of its life. Its chemical composition therefore reflects the environment in which its owner lived in childhood. Strontium (Sr) is a good indicator of mobility. The abundance ratio between its two isotopes – that is, their proportion – varies greatly depending on the age of the surrounding rocks.

Analysis of the strontium isotope ratios of 49 individuals from Barmaz revealed a high degree of homogeneity in most of them and significantly different values ​​in only 14% of the samples, indicating a different origin.

“This technique makes it possible to determine that these are individuals who did not spend the first years of their lives in the place where they were buried, but it is more difficult to determine where they came from,” says Jocelyne Desideri, Associate Professor at the Laboratory of African Archeology and Anthropology at the Faculty of Science, UNIGE. last author of the article.

“Our results show that people were on the move at that time. This is no surprise, as several studies have pointed to the same phenomenon in other places and at other times in the Neolithic period.”

Diet recorded in collagen

Collagen is used to determine carbon (δ13C), nitrogen (δ15N) and sulfur (δ34S) isotope ratios. Each measurement provides information on specific aspects of the diet, such as categories of plants according to the type of photosynthesis they use, the amount of animal protein or the intake of aquatic animals.

Since bones are constantly being renewed, the results only relate to the last few years of an individual’s life. This means that the researchers were able to infer that these former inhabitants of the Barmaz region had a diet based on terrestrial (rather than aquatic) sources with a very high consumption of animal protein.

“What’s more interesting is that we didn’t measure any differences between men and women,” notes Déborah Rosselet-Christ.

“Nor between locals and non-locals. So these results suggest equal access to food resources between different members of the group, regardless of their origin or sex. But this is not always the case. For example, there are differences in diet between the sexes in Neolithic populations in the south of France. “

A clearer picture of agropastoral societies

However, the researchers were able to demonstrate that non-local people were buried in only one of the necropolises (Barmaz I) and higher levels of the nitrogen isotope were measured in the other (Barmaz II). Since the two necropolises were contemporaneous (and only 150 meters apart), the second observation raises the question of whether there was a difference in social status between the two groups of the deceased.

“Our isotopic measurements are an interesting complement to other approaches used in archaeology,” says Jocelyne Desideri. “They help clarify the picture we are trying to paint of the life of these early Alpine agro-pastoral societies, the relationships between individuals and their mobility.”

Déborah Rosselet-Christ is currently pursuing this work as part of her PhD thesis, co-supervised by Jocelyne Desideri and Massimo Chiaradia (Senior Lecturer, Institute of Earth Sciences).

Working with a multidisciplinary team specializing in genetics, palaeopathology, calculus and morphology, he is expanding his field of study to include additional sites in Valais and Val d’Aosta, Italy, covering the wider Neolithic period and the use of other isotopes, such as neodymium, which are potentially interesting in a prehistoric archaeological context.