In 2011, Smith and his wife were taking a National Geographic-organized trip to South Africa’s Pinnacle Point, an archaeological site overlooking the Indian Ocean, when they met Arizona State University archaeologist Curtis Marean. But to better understand what was happening in Africa, researchers needed to find archaeological sites interspersed with Toba ash. Sediments from Africa’s Lake Malawi also suggest that the eruption didn’t markedly change the region’s climate. Previously, researchers in India had found evidence of early humans (though not necessarily anatomically modern Homo sapiens) living through the eruption. Given Toba’s potential role in shaping humankind, researchers have worked to understand precisely how early humans reacted to it. Toba also threw huge amounts of dust and sulfur into the atmosphere, potentially cooling Earth’s surface and building on a cooling event that was already creating glaciers and lowering the planet’s sea levels. In a flash, the supervolcano belched out a thousand cubic miles of rock and dust, sending debris miles into the air and leaving a scar in the earth more than 60 miles wide. Why so meager? Some scientists had suggested that our ancestors were devastated by the Toba eruption. Genetic evidence shows that modern humans descend from a population that numbered only in the thousands when it ventured out of Africa some 60,000 years ago. The discovery, announced on Monday in the journal Nature, strengthens the case that the intense eruption didn’t pose an existential threat to our ancestors, perhaps because humans in Africa took refuge along the coast. However, some humans not only survived but thrived after Toba, judging by the artifacts they created during and after the eruption. “Toba is the largest eruption on Earth in the last two million years,” says Gene Smith, a geologist at the University of Nevada Las Vegas. Some scientists have even suggested that the Toba supereruption was so powerful, it pushed our ancestors to the brink of extinction around the time humans were first venturing out of Africa. The eruption’s effects were felt as far away as southern Africa, where they would have impacted early humans. On the island of Sumatra some 74,000 years ago, an erupting supervolcano wreaked havoc, sending up plumes of ash and debris that spread for thousands of miles and caused temperatures to plummet.
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