The 4.2 ka BP climatic event and its cultural responses

The 4.2 ka event was one of Holocene abrupt-change events and characterized by dry and cool climatic conditions in many parts of the world. The event was reported to have played important roles in the collapses of those major ancient civilizations. This paper first attempts to portray a global picture of this 4.2 ka Event and then reviews those reliably-dated sequences containing 4.2 ka Event retrieved from the domains of four major civilizations. This review further confirms the proposition advocated by the International Stratigraphy Committee that 4.2 ka was the chronological divider between the warmer-wetter middle Holocene and the cooler-drier late Holocene. This review also lends a further support to early proposals that the declines or disruptions of Ancient Egyptian Culture, Mesopotamian Culture, and Ancient Indian Culture at similar to 4.2 ka BP were directly or indirectly associated with the 4.2 ka Event. In Chinese cultural domain, the derailment of nearly all of the well-developed Neolithic cultures at similar to 4.2 ka BP was also chronologically correlated with the proxy data-recorded abrupt climatic change at similar to 4.2 ka BP. But, it should be admitted that either drying or cooling or drying and cooling at similar to 4.2 ka BP might not be sufficient to collapse these well-developed cultures in presently warm and wet southern China. Surely, further studies are needed for constraining the climatic and environmental variables at similar to 4.2 ka BP not only in southern China but also in the adjacent Central Plains of China.