Most Powerful Supervolcano Eruption In The Last 28 Million Years Had No Effect On Human Evolution
The explosion of the Mount Toba supervolcano, located on the modern island of Sumatra, some 74,000 years ago, was Earth’s largest eruption in the past 28 million years. Estimated 1,700 cubic-miles of rock, a volume comparable to almost 3 million Empire State Buildings, erupted, forming a lake visible even from space.
Toba was at least two magnitudes larger (and ten times more powerful) than Tambora, considered the largest eruption witnessed by modern humans. The eruption of Tambora in 1815 was followed by years of unusual chaotic weather in Europe, Asia and America, as the volcanic ash and gases changed Earth’s climate. Toba sent even more ash into the atmosphere.
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In 1998, anthropologist Stanley Ambrose made the connection between the reduced genetic variability found in modern humans and the Toba eruption. Genetic evidence indicates that around 74,000 years ago the human population suddenly collapsed. The exact cause of this genetic bottleneck is unknown, but a volcanic winter following the Toba eruption could explain the reduced genetic variability. Most early humans in Europe and Asia didn’t make it, as the climate and environment suddenly changed, and only a small group, with limited genetic variability, survived by chance in Africa. We, as modern humans, descend from those few survivors.
However, recent discoveries suggest otherwise. The discovery of 65,000-year-old stone tools in northern Australia was quite a sensation. Humankind must have left Africa much earlier than previously thought, migrating between 75,000 and 60,000 years ago into Asia. Two human teeth, excavated in the Lida Ajer archaeological site, a cave located in Sumatra, even suggest that humans lived on Sumatra when Toba erupted. Using modern dating techniques, the researchers were able to date the human remains to 63,000-73,000 years, just in time for the Toba eruption.
Archaeological digs in India show that there are no significant differences in stone artifacts fabricated by early men before and after the eruption. Also, stone tools excavated near the river Son in central India are similar to stone tools used in the Near East and Australia. This cultural continuity over time and such a vast area doesn’t fit the hypothesis that the Toba eruption caused a widespread population and societal collapse.
Nowadays, anthropologists favor an alternative hypothesis to explain the observed genetic bottleneck. Some 65,000 years ago, favorable conditions in Africa led to population growth, and between 65,000 and 75,000 years ago smaller groups of modern humans left Africa. In Europe and Asia they encountered older hominids, like Neanderthals and Denisovans. Competition for limited resources contributed to keeping the number of newcomers low. The relatively small number of modern humans surviving those migration waves could explain the low genetic diversity, without invoking any volcanic catastrophe.