The Silk Road was an ancient network of trade routes that crossed central Asia, constituting the primary link between the Middle East and East Asia during late antiquity and the early Middle Ages. It is frequently cited as one of the most important and long-lasting conduits for bio-cultural exchange in human history and continues to play a crucial role in Asian geopolitics today. To avoid crossing the deserts and high mountains of arid central Asia, travellers used the more temperate corridors through the mountain foothills (piedmonts). The PALAEOSILKROAD project set out to test the hypothesis that at least some of these corridors were used earlier still, by hunter-gatherers in the Stone Age. The extremity of the most arid phases of the last glacial cycle (the late Pleistocene, 110-11 500 years ago) makes such a strategy likely. Because we know from genomic studies that these dispersals are in large part responsible for the origins and makeup of modern Asian peoples, uncovering their archaeological traces is of utmost importance.
Since all current models of dispersal through the region suffer from the low quality and density of the input data, the PALAEOSILKROAD project aimed to discover new Palaeolithic sites in the foothills of the Qaratau, Tian Shan, Dzhungarian Alatau, and Southern (Kazakh) Altai mountains in Kazakhstan, together known as the Inner Asian Mountain Corridor (IAMC). Our second objective was to use these new data to examine how humans adapted to the climatic fluctuations of the last glacial cycle (ca. 110-11 500 years ago).
To achieve these goals, we combined novel remote-sensing techniques with traditional geomorphically-informed foot-survey to discover and explore 95 unknown caves and rockshelters. A subset of these were selected for excavation, revealing several occupations from ca. 50 to five thousand years ago. Together with the open air sites recorded by the project, we have now increased the data density in the study region fivefold. The new sites offer a continuous record for reconstructing occupation history and matching it to climatic oscillations of the Late Pleistocene. Although our conclusions are still preliminary, we see an emerging role for caves in piedmonts as refuges for people during periods of climatic deterioration, such as the Last Glacial Maximum.
Another important objective of the project was to investigate biases in the archaeological record and their causes. We concluded that, although caves are important biological archives, the conditions for their formation in this semi-arid region might limit the number of possible sites. Tectonic spring sites emerge as an important, yet so far untapped focus for future research. These results will help orient future efforts to discover new archaeological sites and interpret spatial and temporal gaps in the archaeological record of this crucial region.
We also carried out the first studies of the distribution of raw materials used by ancient people in the IMAC to fashion their tools. Given the diversity of rock types in Kazakhstan, we had to develop new and objective methods to study and compare their quality, so that we could understand the choices of material transport made by ancient people. These methods have been adopted for other regions and the data generated will contribute to future models linking dispersal to economic decisions and everyday mobility.
Finally, we modelled the success of dispersal through the corridor as a function of social strategies. The evolutionary agent-based model we produced suggests that a high degree of individual cooperation among the dispersing groups would be required to survive in the harshest climatic conditions of the last glacial cycle in the IMAC.
