Climate Change and the Migration of a Pastoralist People c. 3500 cal. Years BP Inferred from Palaeofire and Lipid Biomarker Records in the Montane Western Ghats, India

Human migration in response to past climate change has been recorded globally. The pastoralist Todas are believed to have colonised the higher elevations (>2000 m asl) of the Nilgiris, Western Ghats, India, after similar to 2000 cal. yr BP. During the late Quaternary, climate-induced vegetation shifts in tropical montane forest-grassland mosaic of the Nilgiris have been well-documented using stable carbon isotopes and pollen, but there have been no corresponding investigations of human activity. We used several proxies to infer the human ecology of this region. Radiocarbon-dated (similar to 22,000 cal. yr BP to the present) peat from Sandynallah (2200 m asl) was used to reconstruct fire history, animal abundance, and human presence since the Last Glacial Maximum (LGM). While macro-charcoal records fires at the LGM, macro- and micro-charcoal indicate intense fire at similar to 3500 cal. yr BP, coprophilous fungal spores indicate abundant herbivorous mammals, n-alkane signatures point to arid grassland vegetation, and steroid biomarkers show human faecal remains for the first time. We infer that a pastoralist people, most likely the Todas, migrated to the montane Nilgiris along with their buffaloes in response to prolonged or abrupt climate change in peninsular India similar to 3500 cal yr BP or similar to 1500 years prior to what historical accounts assume.

Automated summary

Human migration to the Nilgiris mountains in response to climate change around 3500 years ago is inferred based on analysis of peat samples. The presence of buffalo remains suggests that pastoralist communities, possibly the Todas, migrated to this region during that time period.