Did a supervolcano nearly wipe out humanity?

Probably not, though the debate is not fully settled. About 74,000 years ago the Toba volcano on Sumatra, in Indonesia, produced what is estimated as a VEI 8 eruption, the largest known explosive eruption of the Quaternary. A supervolcano is simply a volcano that has produced a VEI 8, the top of the scale. Toba's ash covered more than 38 million square kilometres to a depth of at least a centimetre, about 7.5 percent of the Earth's surface, and the eruption lasted perhaps 9 to 14 days.

In 1972 an analysis of human hemoglobins found very few variants, and to explain that, the human population must have been as low as a few thousand until very recently. In 1993 the science journalist Ann Gibbons linked the cold of the last Ice Age, possibly worsened by Toba, to suppressed population growth. In 1998 the anthropologist Stanley Ambrose hypothesised that Toba caused a human population crash to only a few thousand survivors. That is the Toba catastrophe theory: a volcanic winter of six to ten years, a cooling episode of 1,000 years, and a genetic bottleneck in humans.

The theory has not held up well. Climate models of a sulfur emission 100 times Pinatubo's give a maximum global cooling of 3.5 degrees Celsius that fades within 5 years, and do not support a millennium of cold. At the Jurreru Valley in southern India, stone tools above and below the ash layer were very similar, suggesting the eruption did not wipe out the local people. Other Homo lineages, Neanderthals and Denisovans, also survived. Some researchers consider the theory disproven, though another Indian site, the Middle Son Valley, shows a major population decline.