About 74,000 years ago, a volcanic eruption rocked in Indonesia. For a long time, experts thought that the ash from the eruption of Mount Toba threw the Earth into a “volcanic winter” that threatened the survival of the human species. Researchers estimate that the blast was about 5,000 times larger than Mount St. Helen’s in the 1980s. It might sound apocalyptic, but new evidence found in north central India, which would have been coated in Toba’s ash, suggests that the volcano’s effects have been overstated—and ancient hominids were resilient enough to adapt and survive.
The research, published Wednesday in Nature Communications, looks at a progression of stone tools from between 25,000 to 80,000 years ago found in Middle Son Valley near Dhaba. The work builds on research done in 2007 at a different archaeological site in southern India, where some of the same archaeologists also found stone tools from before and after the eruption.
“The big theory out there was that the Toba supereruption created a volcanic winter, so it led to glaciation, it re-sculpted ecosystems, [and] it had tremendous impacts on the atmosphere and landscapes,” Max Planck Institute anthropologist Michael Petraglia tells Lorraine Boissoneault at National Geographic. But the Dhaba site hasn’t turned up evidence for such severe impacts.
Petraglia continues, “It’s much more subtle than what people had imagined. It doesn’t mean there’s no ecological change, but these hunter-gatherers would have been able to adapt to the changes.”
The team hasn’t found fossil remains of ancient humans at the Dhaba site, but signs of ancient human residents come from tools they left behind, like rocks that were fragmented into something sharp. The tools were consistent between 48,000 to 80,000 years ago and resemble tools found in Australia and the Arabian Peninsula. Smaller stone blades were found in the upper, more recent layers of sediment, dating to 25,000 years ago.
Not only does the paper provide evidence that this community survived the eruption and lasted at least another 50,000 years, it also suggests that early humans migrated out of Africa earlier than the generally accepted estimates of 60,000 to 70,000 years ago.
“This paper finally connects the dots between India, southeast Asia, and Australia for modern human dispersal,” Macquarie University geochronologist Kira Westaway, who was not involved in the research but has argued that early humans made it to northern Australia by 65,000 years ago, tells Michael Price at Science magazine.
University of Illinois anthropologist Stanley Ambrose is critical of the study, however, telling National Geographic that he is not convinced by its methods or results. He points out that the researchers only found six glass shards matching the Toba eruption. To Science, he criticizes the way that the researchers determined the age of the tools.
“You can’t call it an archaeological site. You can call it a geological site that has archaeological artifacts in it,” Ambrose tells National Geographic, suggesting that the glass shards and even tools could have been carried to the site by the Son River. And without fossil remains, Ambrose says he is not convinced that the tools were made by the ancestors of modern humans. Neanderthals, for example, used the same techniques to make tools during the Middle Stone Age.
Archaeogeneticist Martin Richards at University of Huddersfield, Queensgate, who was not involved with the work, doesn’t doubt that the tools are as old as the researchers say they are. But Richards agrees that the evidence doesn’t necessarily point to early Homo sapiens.
It might be evidence of “an early wave of modern humans,” Richards tells Science. “Or it might be another kind of early human altogether.”