Local- and regional-scale impacts of the ∼74 ka Toba supervolcanic eruption on hominin populations and habitats in India

The Toba supervolcanic eruption of ∼74,000 years ago is argued to have devastated Homo sapiens populations, causing a human population bottleneck. Through a combination of rapid global climatic deterioration and ecological disruption following the widespread ash-fall, this dramatic eruption, the largest in at least the last 2 million years, is hypothesized to have shaped the genetic structure and diversity of human populations today. Past assessments of Toba’s human impacts, however, have been predominantly theoretical. Using archaeological and geological evidence from sites in India, this study addresses Toba’s local-scale impacts on hominin technology, behavior, demography and habitats in two valleys in India (the Jurreru and Middle Son valleys). Using paleoclimatological and volcanological data, regional-scale impacts throughout India are inferred. A refugia hypothesis is presented that argues for variation in the scale of Toba’s impact throughout India, driven by regional differences in monsoonal dynamics, geography and topography. Areas of north-west India, the Indo-Gangetic Plain and parts of the Deccan to the east of the Western Ghats are argued to have been the most affected, whereas areas of southern and eastern India may have preserved the largest refugia for hominin populations.