ENVIRONMENT

Surviving the Great Eruption

~74,000 years ago

Palaeolithic · Middle Stone Age · Last glacial

Around 74,000 years ago the Toba caldera in Sumatra produced the largest known eruption of the last two and a half million years, scattering ash across half the planet. For decades it was blamed for a global volcanic winter said to have driven humanity to the edge of extinction. The evidence now points the other way: an East African lake core that carries the ash records no such winter, and at two South African sites the same microscopic glass lies within layers of unbroken, thriving human occupation.

Why it matters

A good story met the stratigraphy and lost. The Toba catastrophe once explained our species' low genetic diversity in one dramatic stroke; finer records dissolved the catastrophe, and genetic studies no longer support a bottleneck at that date. People fished the shrinking waterholes of an Ethiopian river through the ash years and kept living on the South African coast. The eruption remains a superb time marker, a single glass layer pinning sites an ocean apart to one moment.

Dating & uncertainty

The eruption itself is well dated to about 74,000 years ago, and its microscopic glass is found from Sumatra to South Africa. What remains debated is its bite: high-resolution climate archives and archaeological continuity have dismantled the once-popular idea that Toba caused a global volcanic winter and a human near-extinction. Something did register, all the same. Just above the ash, the Lake Malawi record shows a brief rise in charcoal and drought-tolerant grasses, meaning less rain and the loss of at least some mountain vegetation, but nothing resembling a winter.

Sources

1. Smith et al. (2018), Nature · Humans thrived in South Africa through the Toba eruption about 74,000 years agodoi:10.1038/nature25967
2. Yost et al. (2018), Journal of Human Evolution · Subdecadal phytolith and charcoal records from Lake Malawi, East Africa imply minimal effects on human evolution from the ~74 ka Toba supereruptiondoi:10.1016/j.jhevol.2017.11.005
3. Kappelman et al. (2024), Nature · Adaptive foraging behaviours in the Horn of Africa during Toba supereruptiondoi:10.1038/s41586-024-07208-3

Our species’ history as one day

18:21:425 h 38 min before midnight

if the 315,000 years of Homo sapiens were compressed into a single day