Stone Age People Survived a Supervolcano Eruption by Adapting to Dry Periods, Archaeologists Suggest

Around 74,000 years ago, a massive supervolcano called Toba erupted in Indonesia, creating the largest known natural disaster in the last 2.5 million years.

Now, an archaeological site in northwest Ethiopia, called Shinfa-Metema 1, may point to how humans adapted to the widespread changes in climate induced by the catastrophic eruption. People at this site shifted to eating more fish during dry periods that seem to be linked to the volcano, according to a study published last week in the journal Nature.

“This points to how sophisticated people were in this time period,” John Kappelman, first author of the new study and a paleoanthropologist at the University of Texas at Austin, tells the New York Times’ Carl Zimmer.

“This on-the-ground evidence contradicts the popular model that the ‘volcanic winter’ caused by the Toba eruption almost drove humans and our closely related ancestors to extinction,” Michael Petraglia, an archaeologist at Griffith University in Australia who did not contribute to the findings, tells the Washington Post’s Carolyn Y. Johnson.

“Instead, all evidence from Shinfa-Metema and elsewhere now indicates that human populations were flexible enough in their adaptations to overcome environmental challenges, even those introduced by the Toba volcanic super-eruption of 74,000 years ago,” he adds.

Kappelman’s team first came across the Shinfa-Metema 1 site in 2002. Excavations revealed fossil mammoth teeth and ostrich eggshells, as well as bones with cut marks, writes New Scientist’s Michael Le Page. Archaeologists estimate humans populated the site for five to ten years, during a time with seasonal dry periods.

The researchers dated the pieces of ostrich eggshell to around 74,000 years ago, the time of the Toba eruption. And the same layers of sediment contained rocks with tiny fragments of volcanic glass, suggesting people lived there both before and after the blast in Indonesia, writes CNN’s Katie Hunt.

The site had an unusually high abundance of fish compared to other Stone Age sites, suggesting that people captured more fish as waterholes shrank during the dry season.

“People start to increase the percentage of fish in the diet when Toba comes in. They’re capturing and processing almost four times as much fish [as before the eruption],” Kappelman says to CNN.

“It is sophisticated behavior… to fish, instead of hunting terrestrial mammals,” Kappelman tells the Washington Post. “That kind of behavioral flexibility is kind of a hallmark of modern humans today.”

The researchers also uncovered 16,000 chipped rocks that could be arrowheads, suggesting the site’s inhabitants used bows and arrows to hunt. If confirmed, these artifacts would be the earliest evidence of archery, per the New York Times.

Humans’ apparent adaptability at this site might shed light on early migrations, some researchers say. Modern humans spread out from Africa on multiple occasions more than 100,000 years ago, but people without African ancestry are tied genetically to a dispersal that occurred within the last 100,000 years. Previous research had suggested that early humans migrated during humid periods that offered more plants and food sources.

Instead, the finding that Stone Age people adjusted to arid conditions suggests humans may have ventured out of Africa during dry periods. They could have followed “blue highways” created by seasonal rivers, moving between small waterholes as they depleted each one, according to a statement from the University of Texas at Austin.

Rachel Lupien, a geoscientist at Aarhus University in Denmark who did not contribute to the findings, tells the Washington Post that she isn’t convinced by this theory yet. Comparing the short-term climate at Shinfa-Metema 1 to the climate in other locations, or across thousands of years, overlooks other variables that contribute to climate and rainfall, she says to the publication.

“Of course this new work doesn’t mean that humid corridors were not still important conduits for dispersals out of Africa, but this work adds credible additional possibilities during more arid phases,” Chris Stringer, a paleoanthropologist at the Natural History Museum in London who was not involved in the research, tells CNN.

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Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.