Stone tools reveal how ancient humans survived volcanic catastrophe

Stone tools unearthed from a site in the Son river valley in Central India reveal that modern humans lived continuously in various pockets of India over the last 80,000 years¹. The toolmakers may also have survived a massive eruption of the Toba volcano in Sumatra, Indonesia around 74,000 years ago, the archaeological finds reveal.

The Toba volcanic eruption blanketed a vast marine and terrestrial area stretching from the Arabian Sea to the South China Sea. India and various regions of South Asia and Europe are thought to have been covered in this thin veil of ash for days to several weeks. The discovery of the stone tools debunks an earlier theory that the eruption nearly decimated all humans in India and in parts of South Asia and Europe.

“The stone tools are more or less identical before and after the Toba eruption, suggesting that the eruption likely had little effect on people living in India at the time,” says lead author of the study Chris Clarkson from the University of Queensland in Australia.

The tools, he says, are very similar to the ones found in Africa and Arabia around the same time. These tools were most likely made by modern humans, meaning that humans like us lived in India very early on, and according to Clarkson, much earlier than previously thought.

The eruption is surmised to have caused an extended volcanic winter that disrupted human dispersal out of Africa and their arrival in Asia and Australia. Researchers have long debated its deleterious effects on the globe-trotting humans. Fossil finds from key regions such as India have been scarce.

Clarkson, teaming up with Indian researchers from the University of Allahabad, the University of Madras and the Banaras Hindu University, explored the middle Son river valley in Madhya Pradesh, where very thick deposits of Toba ash are found in the eroding cliffs. They focused on Dhaba, a site on the river bank very close to the thickest and best preserved Toba ash deposits in the valley.

On excavating three sites in Dhaba, they unearthed the stone tools made using the Levallois technology, a method for removing flakes and stone points of predetermined size by careful preparation of the core. The tools contain predominantly bidirectional and unidirectional cores, flakes, points, blades, notches and scrapers. The tools were made between 80,000 and 40,000 years ago, the researchers say.

The toolmakers were hunter-gatherers who extensively used the resources of the river, Clarkson says. “...They made wooden tools and most likely hunted with stone-tipped spears.” Presence of red ochre, an iron-based pigment used for cave painting, indicates that they probably practiced symbolic or ceremonial activities. Since no organic artefacts survive at the site, it is difficult to say what they ate or what kinds of organic tools they made, Clarkson points out.

The people living at the site stuck to same lifestyle before and after the eruption. This indicates that they were not seriously affected by the eruption. “There may have been some short-term consequences, but we do not see total replacement or big changes in tool kits indicative of a highly altered lifestyle,” he adds.

However, in the absence of any human remains, it is difficult to support the view that the modern humans arrived and settled in North India before the Toba eruption, contends Kumarasamy Thangaraj, a geneticist from the Centre for Cellular and Molecular Biology in Hyderabad.

Thangaraj says genetic evidence suggests that the skin colour mutation, lactate persistence mutation and other variations are common between people of North India and Europe. The age of Europeans, he says, has been estimated to be about 40,000 years.

Clarkson, however, is optimistic about the findings. Beyond India, fossil and archaeological evidence from Israel, Greece, Arabia, Sumatra and China reveal that modern humans were living outside of Africa for a very long time before their main dispersal about 50,000 years ago, he says.

In this context, the Dhaba sites serve as an important bridge linking regions with similar archaeology, he says.

References

1. Clarkson, C. et al. Human occupation of northern India spans the Toba super-eruption ~74,000 years ago. Nat. Comm. 11:961 (2020)Doi: 10.1038/s41467-020-14668-4