Biomolecular archaeology, an alternative when analysing anthropological remains

The research by Maite Iris García-Collado deals with knowledge about the diet of the population that inhabited the hamlet of Boadilla, a settlement of peasants in the Visigoth period (6th-8th centuries CE) located on the outskirts of the current municipality of Illescas, in Toledo. Biomolecular analysis not only allows the diet of a population group to be reconstructed, it also offers a real alternative when recounting the history of anthropological assemblages, as there would be limited potential if traditional methods alone were used to study them.

The work of this UPV/EHU researcher aimed to show that the techniques of biomolecular archaeology could offer a useful alternative in obtaining fresh data about various social and economic aspects of the rural societies on the Iberian Peninsula during the Early Middle ages, and thus restore the historical value of these anthropological assemblages. So firstly a traditional anthropological study was conducted to ascertain the size of the population buried at Boadilla and its demographic profile (age and sex), which determined that it was a stable population in which all the age categories were represented. Secondly, carbon and nitrogen stable isotope analyses were carried out on part of the population selected randomly. “This technique is based on the premise that the chemical composition of the food we eat ends up reflected in the chemical composition of our body tissue. So if we analyse the composition of the anthropological remains of an archaeological population, we can find out about their diet,” explained Maite Iris García-Collado.

Little is known about rural habitats during this period because written sources hardly reveal anything about them and the archaeological remains left behind and scant and not very visible. “In contexts of this type, cemeteries that occupied extensive areas are frequently found; the tombs form irregular lines in which one or more individuals were interred successively, often accompanied by different kinds of objects,” remarked the researcher. Yet the anthropological material from these cemeteries, in other words, the bones and teeth of the individuals that inhabited these hamlets have received little attention, because they are often fragmented and poorly preserved. This has been an obstacle in finding out about these populations, because it was assumed that the information that could be obtained from their anthropological remains was very limited. Now, this research has demonstrated that the application of this type of analysis not only allows the diet of a population group to be reconstructed, it also offers a real alternative when recounting the history of anthropological assemblages, as there would be limited potential if traditional methods alone were used to study them.

Cereals-based diet

According to the carbon isotopes, the diet of the population buried at Boadilla was based on winter cereals, a category that included wheat, barley, rye and oats. However, short-cycle cereals, which in this time period are restricted to millet and foxtail millet, also made up a considerable part of the diet of that community. "This is significant because this study and other previous ones indicate that the production and consumption of these lesser cereals could be a characteristic trait of groups of peasants with a certain autonomy and who exercised control over their production. Millets are highly nutritious, ecologically efficient cereals, but have been little appreciated traditionally. That is why they do not meet the logic in which a superior power controls the products that are cultivated, but make more sense in contexts in which the peasants themselves can decide to diversity their harvests,” stressed García-Collado. With respect to proteins of animal origin (meat, eggs, milk, dairy products) which have been detected through nitrogen isotopes, they were consumed in a limited, occasional way. It has also been possible to rule out the consumption of fish.

The next step was to analyse the variability of the diet within the population. “We spotted no difference with respect to the consumption of cereals across the various age categories. Yet we did identify a model with respect to the consumption of proteins of animal origin,” said the UPV/EHU researcher. According to the results of the nitrogen isotopes, the younger individuals (between the ages of 2 and 8) were the ones that consumed the fewest products of animal origin. The consumption of meat, eggs, dairy products and other derived products increased slightly between the ages of 8 and 14 and during adolescence reached the same level as the adults (after the age of 14). “That means that access to products of this type was determined by age and that access to them by younger individuals was severely restricted. Furthermore, we learn that it was after the age of about 14 that adolescents began to be treated like adults,” she pointed out.

Another interesting question investigated was the existence of differences in the diet between the individuals buried with personal adornment or tools of everyday use and those who were buried without anything like that. “These objects, which were sometimes placed alongside the bodies, have often been thought to indicate the social position of the individual. But if that was the case, there would not have been significant differences between the diets of the more or less important individuals,” concluded García-Collado. Furthermore, it was possible to confirm that the diets of the individuals buried in the same tomb tended to be similar, an argument in favour of the hypothesis that these funerary structures were used as pantheons for large family groups.

Finally, an assemblage of samples of domestic animals was also analysed, since determining the eating models of these animals is useful for characterising the stockbreeding practised in that hamlet. “The most interesting result is that they adopted different strategies for each species. Cows, sheep and goats probably grazed on land close to the hamlet, which contributed towards the fertilising the croplands. By contrast, horses were most likely sent to open pastures further away from the settlement,” explained the researcher.

Further information

This work is part of the PhD thesis by Maite Iris García-Collado, doctoral student in the UPV/EHU’s Department of Archaeology, and is the result of collaboration between the UPV/EHU’s Cultural Heritage and Landscapes Research Group and the Università degli studi della Campania ‘Luigi Vanvitelli’ (Italy). It is also part of the special thematic issue on the study of diet in the past on the Iberian Peninsula based on archaeological sources, and which was published by the Archaeological and Anthropological Sciences journal, edited by the researchers Olalla López-Costas (University of Santiago de Compostela) and Michelle Alexander (University of York).