The Toba supervolcanic event caused a bottleneck in the human population by _______.

The Toba eruption sent enormous amounts of ash and sulfur aerosols into the atmosphere, which reduced sunlight and caused a period of global cooling. This volcanic-winter effect may have stressed human populations and contributed to a population bottleneck. So the best choice is “inducing an ice age”; the eruption did not raise global temperatures or cause the bottleneck mainly by burning villages with lava.

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