20,000–9700 BCE: (Global History Period Two — From Around the Height of the Last Glacial Maximum to the Beginning of the Holocene, a New Global Age Marked by…

20,000–9700 BCE: (Global History Period Two — From Around the Height of the Last Glacial Maximum to the Beginning of the Holocene, a New Global Age Marked by Recurrent Climatic Challenges to Ancestral Ways of Life, the Last Glacial Maximum Giving Way to a First Glacial Retreat Around the Eighteenth Millennium BCE Followed by the Return of Colder Conditions in the Oldest Dryas Before 16,000 BCE, Then Warming During the Bølling and Allerød Interstadials of 12,700–10,900 BCE Interrupted by the Older Dryas of 12,100–11,900 BCE, a Final Return of Ice Age Conditions in the Younger Dryas of 10,900–9700 BCE Before the Holocene Began): From around the height of the Last Glacial Maximum down to the beginning of the Holocene epoch around 9700 BCE, a new global age ensued — one marked by recurrent climatic challenges to ancestral ways of life. Around the eighteenth millennium BCE, the Last Glacial Maximum gave way to a first retreat of glaciation, but this respite did not last. With the onset of the Oldest Dryas period, colder Ice Age conditions resumed around or slightly before 16,000 BCE. Three millennia later, between around 12,700 and 10,900 BCE, a shift to warmer climate took place during the successive Bølling and Allerød interstadials — though with a brief intervening colder period, the Older Dryas, of around 12,100 to 11,900 BCE, separating the two warm phases. A last return of Ice Age conditions came with the commencement around 10,900 BCE of the Younger Dryas period. Only with the end of this phase around 9700 BCE did the Ice Age finally come to a full close and the Holocene epoch begin. The climate of this period was not a slow, steady warming. It was a series of violent oscillations — warmings and coolings, advances and retreats — that whipsawed human communities around the globe for ten thousand years. Each warming phase opened new lands, new resources, new possibilities; each cooling phase closed them again, forcing populations to adapt, to migrate, to innovate or perish. It was within this crucible of climatic instability that some of the most consequential innovations in human history took shape — the domestication of plants and animals, the development of new subsistence strategies, the emergence of more complex social formations. The instability was not an obstacle to human progress. It was the engine of it.