Department of Earth and Environmental Sciences at Nagoya University
By sequential sampling and analyzing tooth enamel, we can read the seasonal variations in stable isotope ratios recorded in teeth. Seasonal variations in the stable carbon (δ13C) and oxygen (δ18O) isotopes can be used to infer what the individual consumed, where, and in what season. In other words, this method is suitable for studying the husbandry strategies from livestock remains. However, in the analysis of an isolated tooth, the term of the obtained variation would be short, and difficult to capture the feature of the variation. Analyzing two teeth per individual can provide long-term variation, although this requires the use of well-preserved archaeological materials.
In our new study, we used this intra-individual sequential isotope analysis with M2 and M3 teeth per individual as far as possible to investigate early husbandry strategies in the southern Caucasus. We analyzed the mandibular tooth enamel of goats, sheep, and cattle (only isolated teeth) from the Neolithic settlements, Göytepe (ca. 5650–5460 cal BC) and Hacı Elamxanlı Tepe (ca. 5950–5800 cal BC) located in western Azerbaijan. As reference samples, we also analyzed modern goat and sheep individuals that are known to have grazed in the vicinity of the sites.
In this region, the first full-fledged Neolithic agro-pastoral economy called the Shomutepe-Shulaveri culture, emerged suddenly around 6000 cal BC. Despite their geographical closeness to each other, this is about 2000 to 3000 years later than the emergence of agro-pastoral practices in the Fertile Crescent. It is important to study the delay in this phenomenon in detail in order to understand the process of diffusion of agro-pastoral economy in human society. Therefore, in this study, we focused on how early agro-pastoral economy was practiced in this region under the peculiar environmental conditions colder in winter, adjacent to mountainous regions, that are uncommon in the Fertile Crescent. Livestock management regarding mobility and migration is a key aspect in understanding agro-pastoral societies. Therefore, we attempted to provide isotopic evidence indicative of early husbandry practices in the southern Caucasus.
The obtained data showed several different patterns that may be explained by different modes of husbandry practices:
- Some of the goats and sheep exhibit large amplitudes in δ13C and δ18O variations (see figure above: part a). This was interpreted as a lowland pasturing pattern because the modern goat and sheep showed the same pattern.
- A Neolithic goat and three Neolithic cattle samples exhibited relatively small amplitudes and/or inverse cyclical variation patterns (figure b and d). While these patterns may have been caused by multiple factors, such as drinking water and food/fodder, vertical transhumance has also been proposed to result in the similar isotope patterns (e.g., Henton et al., 2010; Tornero et al., 2016). If animals experience seasonal vertical transhumance between lowlands in winter and highlands in summer, it is expected that the δ13C fluctuation range reduces. In addition, the δ13C value of C4 plant feeders is presumed to decrease if they spend summer in highlands where C4 plants are less.
- Some individuals illustrated a pattern with a larger amplitude of δ18O seasonal variations but a smaller amplitude of δ13C variations (c). It is likely that some factor reduced the variation of δ13C. We proposed a possibility of the use of fodder (C3 plants) collected in a short term and given to livestock thus dampening the seasonal variation in δ13C.
The factors contributing to the patterns of isotopic variation presented in our study may not be limited to transhumance or the use of fodder but are consistent with such possibilities. To verify these hypotheses, other analytical methods, such as strontium isotope analysis, are required to specify pasturing places in different seasons on the basis of a local and regional isoscape. In any case, at least, these various sequential isotopic patterns suggest that a variety of livestock breeding strategies were already adopted by Neolithic inhabitants in the southern Caucasus. Thus, long-term sequential isotope data from plural teeth per individual would provide us more specific seasonal variation patterns.
This research derives from the Azerbaijani-Japanese Archaeological Mission directed by Prof. Yoshihiro Nishiaki (The University of Tokyo) and Dr. Farhad Guliyev (The National Academy of Science, Azerbaijan). The financial support for this study was provided by the JSPS KAKENHI (No. 17H04534), the MEXT KAKENHI (No. 16H06408 and 20H00026), and The Takanashi Foundation for Historical Science.