The last glacial period, which lasted roughly 110,000 years, suffered a sharp final reversal: a roughly thousand-year cold snap known as the Younger Dryas. At the end of that interval — around 9700 BCE in Greenland ice-core dating — average temperatures across the Northern Hemisphere climbed steeply over only a few decades. This sharp boundary is the formally defined base of the Holocene Epoch.

The Holocene is not in itself unusual; it is one of dozens of interglacial intervals during the Pleistocene. What is unusual is what we have fitted into it: every agriculture, every city, every writing system, every civilisation we know. The climate became warm enough to make farming workable, stable enough to make crops carryable across years, and broad enough — as ice sheets retreated — to open large new landscapes to humans. Tentative plant cultivation in the Near East during the preceding millennia matured into true agriculture in the Holocene window; within a few thousand years, large settled places such as Göbekli Tepe, Jericho, and Çatalhöyük appear.

In 2009 the International Commission on Stratigraphy formally fixed the base of the Holocene at a specific layer in the Greenland NGRIP ice core, dated to 11,700 ± 99 years before AD 2000. In 2018 it was further subdivided into three ages: Greenlandian, Northgrippian, and Meghalayan. The Anthropocene debate begins from here: is the human era a subdivision inside the Holocene, or a separate epoch that has ended it?