CLIMATE × HUMAN EVOLUTION

The Toba Eruption

~74,000 years ago

Phanerozoic · Cenozoic · Quaternary · Pleistocene · Late Pleistocene

Sumatra produced the largest eruption of the last two million years, spreading ash from India to the floor of the Indian Ocean. For decades it was blamed for nearly extinguishing humanity. Two South African sites nine kilometres apart contain the volcanic glass, layer by layer, and show people living there straight through it without a break.

Why it matters

A famous catastrophe is being taken apart by the same kind of evidence that built it. Climate simulations run at both the high and low ends of the sulfur estimates now put almost no chance of Africa cooling by more than four degrees, and the archaeology agrees. Watching a certainty become a question is what the science of deep time mostly consists of.

Dating & uncertaintyDisputed

The eruption is firmly dated. Its consequences are not: the claim that it nearly extinguished our species has been undercut by sites in South Africa that show no break in occupation across the ash layer, and by climate models that find little cooling in Africa even at the high end of sulfur estimates.

Sources

1. Smith et al. (2018), Nature · Humans thrived in South Africa through the Toba eruption about 74,000 years ago
2. Black et al. (2021), PNAS · Global climate disruption and regional climate shelters after the Toba supereruption
3. Ge et al. (2020), Quaternary International · Understanding the overestimated impact of the Toba volcanic super-eruption

Earth history as one day

23:59:581.4 s before midnight

if Earth’s 4.54 billion years were compressed into a single day