Two recent articles from American Journal of Physical Anthropology are using stable isotope analysis to look at variations in dietary habits. Both look at population differences, one from the perspective of change through time and one from an individual life history perspective. Understanding diet is important as it can tell us a lot about the intra-group variation as well as how cultural change affected people. Since the bones themselves are being used, we are looking at directly what they ate rather than at bones of animals or plant residues and inferring diet. There are many intricacies to a culture that can be teased apart by looking at diet, such as differences between sexes and ages, or between specific population groups, and these can vary drastically through time.
The first article is by Lightfoot, Slaus, and O’Connell (2012), and examines changes in diet due to changes in culture. They posit that “diet encodes social and cultural values… Food not only fulﬁlls the nutritional needs of the body, but also deﬁnes ‘us’ and ‘them’.” Therefore, when societies change due to forces like immigration or invasion, the diet may also change regardless of unchanging food availability or resources in the area. The area under investigation is the Ravni Kotari region in Croatia, which experienced substantial social and cultural change in the Roman and Early Medieval periods with the arrival and exit of various groups. They compare changes in the skeletal remains against the observed dietary trends seen in the archaeological record in order to determine whether diet is changing with technology and culture, as well as the extent to which these changes were adopted.
Archeobotanical and zooarcheological studies from Croatia are limited, however we do know from animal bones and the presence of tools that farming increased in the Roman period and that new animals were introduced in the Early Medieval period. Wear on dentition suggests that farming became increasingly important in the Early Medieval period, with increased diet of carbohydrates. Due to a lack of information, stable isotope analysis can be critical on filling in the gaps of how diet was actually shifting and the extend to which change affected dietary habits. The sample includes 413 skeletons from 10 sites. Carbon and nitrogen isotope ratios were determined based on samples of bones from the ribs. The analysis showed that the diet was broadly stable, with a focus on C3 plants, minor C4 and some marine foodstuffs. During the Roman period there is an increase in N15 levels, suggested increased marine diet. This could be due either to changing social perception of marine resources given the Roman inclination towards them, or due to increased population pressure and need for more food. In the Early Medieval there is an increase in C13, which is accounted for by increased consumption of millet. With worsening weather patterns and collapse of Rome might have led to increased use of this hearty agricultural crop. They conclude that the results “indicate that there was dietary variation between periods, rather than coexistence of different diets consumed by different people within the population, or no dietary change between periods”. This means that with invasion and immigration the population was changing its diet as a whole, although the reason for this change, whether cultural, technological, economical or environmental, is not known.
The second article is written by Reitsema and Vercellotti (2012). Their goal is to look at the diets of sub-groups in Medieval Italy. The authors note that the majority of known information about medieval diet comes from historical sources which primarily deal with the sociopolitical and religious elite. Information about the general population is more often inferred from limited historical accounts and archaeology. However, “these sources indicate that medieval food access followed strict delineations based on age, sex, and status”. It is these delineations and variations within the population that the researchers seek to find using stable isotope analysis.
The sample is taken from the Medieval site of Trino Vercellese, dating from the 8th to 13th centuries. 30 individuals were used from the over 700 available including 20 adult males and 10 adult females. Based on burial goods they determined that 4 females and 10 males were high status, and 6 females and 10 males were low status. Samples were taken from ribs which would indicate adult diet and from a molar which would indicate childhood diet. Overall they found that N15 ratios were fairly low, suggesting a diet in primarily land terrestrial meats rather than fish. They found that high-status children had diets more consistent with their classes, whereas low-status children were more variable. Diet among children was more similar, and disparities increased with age. Adults females had little variation in diet between the classes. However, males of higher status consumed more proteins than males of low status. Low status males were the only group to show high consumption of the C4 grain millet which raises their C13 ratio. It is interesting to see the variation in the diets, which suggests that low status males had the most variable and lowest protein based diets, although this only becomes apparent in adulthood. The reason is likely that high status individuals can afford meat, and low status women are given meat in order to be more productive at childbirth.
These two studies use stable isotope analysis to reveal dietary trends, but use them in very different ways. Both looking at the broad trends of diet as well as the intragroup variation are important. In addition to this, both studies look at the archaeological and historical evidence, as well as the broader social context. It is nice to see the ‘science’ integrated into the discipline!
Lightfoot E, Slaus M, & O’Connell TC (2012). Changing cultures, changing cuisines: Cultural transitions and dietary change in iron age, roman, and early medieval croatia. American journal of physical anthropology, 148 (4), 543-56 PMID: 22552855
Reitsema LJ, & Vercellotti G (2012). Stable isotope evidence for sex- and status-based variations in diet and life history at medieval Trino Vercellese, Italy. American journal of physical anthropology, 148 (4), 589-600 PMID: 22553011