The 4.2 kiloyear event

The title of this post is the weird name scientists have given to a prolonged drought that devastated the tropics, probably worldwide, beginning about 2,200 BC. Wikipedia says it may have lasted for the entire century, but some estimates have it considerably shorter, maybe 30 years. Anyway, that was enough. Important civilizations collapsed, including the Egyptian Old Kingdom and the Akkadian empire in Mesopotamia.

You may be struck by the omission in the Wikipedia article of any discussion of the cause. That is because the cause is unknown. One hypothesis is that it resulted from a meteorite strike, although the mechanism would be unclear. I'm surprised, actually, that there isn't more consternation about the mystery of the cause. Some doubt that a single global event really happened, and argue that more localized and temporally limited events have been conflated.

In any case, that a prolonged drought did occur in Egypt, resulting in reduced flow of the Nile and severe food shortages, is incontrovertible. Perhaps you are thinking that this event was the inspiration for the story of Joseph, that we have just read. If it is in any way, that just highlights the fictitious nature of the story. The Pharaoh at that time was Pepi II. The drought continued throughout his reign, but he did not consolidate power as a result. On the contrary, the kingdom went into decline and collapsed completely after his death, disintegrating into local fiefdoms. After a prolonged period of civil war, Egypt was reunified some 200 years later. So, the story of the captivity which follows the death of the unnamed Pharaoh in the story of Joseph is impossible. Pepi's immediate successor only lasted 1 year; a series of similarly short and obscure reigns was followed by the interregnum.

For us, of course, the lesson is that abrupt climate change can bring about the collapse of civilizations. We don't know why the 4.2 kiloyear event happened, but we do know the consequence.