From Steuart Campbell
Dan Jones asks “why did humans leave Africa when they did…” (27 October, p 36). I am surprised he did not mention the idea that the supervolcanic explosion of Toba on Sumatra about 70,000 years ago caused a bottleneck in the evolution of all species, especially Homo sapiens.
For at least six years, there was a “volcanic winter” that must have had a profound effect on our ancestors, probably forcing major lifestyle changes. It is surely not a coincidence that within 5000 years our species migrated out of Africa. Species tend to react to environmental factors; perhaps we owe our developmental spurt and exploratory instinct to the Toba catastrophe.
Edinburgh, UK
