Global, abrupt, century-scale climate changes occurred at 12.7, 8.2, 5.2 and 4.2 kaBP. Each abrupt climate change forced radical social adaptations to changed environmental conditions: societal collapse, habitat-tracking, and/or or subsistence technology innovation. The effects of these climate changes are available archaeologically for quantification in the early agricultural villages, states, and empires of west Asia.

The Younger Dryas forced hunter-gatherer collapse across west Asia and the adoption of agriculture. Why this did not happen elsewhere forces consideration of the unque situation of post-Pleistocene west Asia.

The 8.2 kaBP event forced habitat-tracking into arid southern Mesopotamia and the first adoption of irrigation agriculture, the abandonment of PPNB agricultural villages from the Euphrates to the Mediterranean, and perhaps the alteration of Nile Valley settlement.

The 5.2 kaBP event caused the collapse of dry-farming cities, villages, and southern colonies in northern Mesopotamia, and the nucleation of regional settlement in southern Mesopotamia’s earliest civilization. Synchronous alterations of Egyptian settlement and social organization were likely caused by the same century-scale aridification event

The 4.2 kaBP event forced the collapse of dry-farming agriculture states and empires in southeastern Europe, Egypt, Palestine, Mesopotamia and the Indus, the widespread adoption of pastoral nomadism across West Asia, and habitat-tracking into the still-productive irrigated plains of Mesopotamia and the Indus Valley.

The variable signature of these events in the proxy records suggests each event’s unique causality. The magnitude of these changes in the proxy records challenges understanding of the Little Ice Age proxy records’ magnitudes---because the instrumental variability for the Little Ice Age is so slight.