20,000 to 9700 BCE · Africanspan
The ice age ended in fits, with four reversals along the way
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Glaciers began retreating around the eighteenth millennium BCE and the relief did not hold. Cold returned with the Oldest Dryas at or a little before 16,000 BCE and stayed for three thousand years. Warmth came back between about 12,700 and 10,900 BCE across two intervals that geologists call the Bolling and the Allerod, separated by a short cold snap, the Older Dryas, running roughly from 12,100 to 11,900 BCE. Then ice age conditions returned once more with the Younger Dryas at about 10,900 BCE, and only when that ended around 9700 BCE did the Holocene begin. Read as a list it looks like bookkeeping. Lived through, each reversal opened or closed whole regions to human settlement inside a few generations. Populations moved, split, merged and worked out new ways to eat. Farming, herding and the larger settled communities that followed took shape inside this instability rather than after it.
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