Assessing impact of short-term climatic change on human populations of the Near East using combined histological and isotopic methods

• Applicant: Dr. Carsten Witzel
• Subject Area: Egyptology and Ancient Near Eastern Studies ; Evolution, Anthropology ; Prehistory and World Archaeology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545078333

Understanding how climate change impacted human societies in the past has become a primary research topic in archaeology. Usage of available proxies for climate reconstruction (speleothems, lake sediments, etc.) enables, in a correlative approach, to identify interconnections between the recorded climate fluctuations and developments in past societies. However, the proxies available so far have relatively low temporal resolution. Additionally, the data miss to document how people themselves were affected as biological beings by any of these climate fluctuations. Therefore, fully reliable causal association of changing climate with any shifts in human behaviour or material culture remains very difficult if not impossible.The most common climatic proxy is the proportion of stable oxygen isotopes, 18O and 16O, expressed as the δ18O value. With raising temperature, water evaporation rate increases and as the water particles with the lighter isotope 16O evaporate easier, the δ18O value in remaining water is higher. Through water consumption this isotopic signature affects the body water composition and is incorporated also in forming human enamel. Tracing the changes in histologically identified incremental enamel layers, enables insights into changes in temperature and humidity during the several years of the tooth forming period early in life. By analyzing ten individuals for short-term climate fluctuations locally at the archaeological sites using high-resolution (bi-weekly) sequences of δ18O measurements obtained by Sensitive High-Resolution Ion Microprobe (SHRIMP) in the incremental layers of human enamel we will develop and test a new approach of research on climate variability in the past. Additionally, we will also use other proxies as 87Sr/86Sr ratios and trace element concentrations to understand how signals from individual mobility and/or variable drinking water sources may interfere with the signal from climate variability. We will focus on two periods that are widely considered as affected by prolonged droughts, i.e. the transition from the Early to Middle Bronze Age (c. 2200-2000 BCE) and the transition from the Late Bronze Age to the Iron Age (c. 1200-800 BCE). By comparing two regions with different ecology, i.e. the relatively humid dry farming zone of Northern Mesopotamia and the Iranian Central Plateau with lower precipitation and farming usually based on small-scale irrigation, we will be able to differentiate between regional and global trends in climatic conditions. At the same time we can assess the extent to which people are affected directly on an individual and a community basis with respect to growth and development. Patterns of effects would amalgamate to adaptive behavioural shifts finally responsible for societal change. The ultimate effect of the project may be a powerful new tool enhancing our ability to identify the impact of short-term climate fluctuations on past human populations.

• DFG Programme: Research Grants
• International Connection: Poland
• Cooperation Partner: Professor Dr. Arkadiusz Soltysiak