SciencePrehistoric (c. 12,900–11,700 years ago)Northern Hemispherehigh confidence

The Younger Dryas was a period when glacial conditions returned across much of the Northern Hemisphere within about 1,000 years, coinciding with the disappearance of the Clovis people, mammoths, and giant bison.

Notes on verification

Well-corroborated by multiple independent scientific sources (PNAS, ScienceDaily, PBS/NOVA) on timing, duration, and coincidence with Clovis/megafauna disappearance. Causal mechanisms remain debated but are not part of this factual claim. [cascade flags: aggregator_dropped_primary_exists | tier=silver indep_score=1.0 clusters=2 claim_tier=notable]

Sources