We might be inclined to believe some ancient civilizations have lasted for a thousand years. The reality is that it's much shorter than that.

In fact, based on the calculations of University of Cambridge's researcher Luke Kemp, the average lifespan of ancient civilizations is 336 years:

Only civilizations that existed between 3000 BC and 1000 AD are included in this graph, and the data is drawn from studies on the size and longevity of empires and a survey on ancient civilizations.

You can see a full list of the civilizations represented on the graph here. Some civilizations have survived noticeably longer than others. The Kushite Kingdom, an ancient kingdom in northern Africa, for instance, lasted from 785 BC to 350 AD — a total of 1,150 years — and is one of the longest-lasting civilizations on the graph. By contrast, the period known as Classical Greece only lasted for 265 years.

Kemp's study also touches upon how a complicated host of factors may have contributed to the death of these ancient civilizations, including climate change and socio-economic inequity. Perhaps somewhat worrying is the fact that many of these factors, which serve as indicators of whether a civilization may be on its way to collapsing, now seem to be present in our own modern societies right now.

[Read more at BBC]