Sub-stage· The columns of time
Northgrippian
6,237 BCE → 2,251 BCE
The middle age of the Holocene, four thousand years in which cities, writing, metal and the first states all appear, in succession and largely without borrowing.
What the evidence shows
It takes its name from the North Greenland Ice Core Project, whose ice fixes its lower boundary at 8,200 years ago; the upper one, at 4,200, is drawn in a cave in India instead. Its span happens to contain almost everything a history of civilisation would list at the start, which is an accident of where the geological markers fall rather than a claim about causation. The two disciplines divide the same time for different reasons, and it is worth noticing when their divisions coincide, because they usually do not.
Bounds and conventions
Defined by ice chemistry, not by human events. A reader who sees the first cities appear inside this age should resist reading the age as their cause: it opens on an abrupt climate signal in Greenland ice and closes on a drought recorded half a world away.
NGRIP1 GSSP, 8,236 years b2k.