Did agriculture lead to complex societies or was it something less nurturing? Cliodynamics provides an alternative cause: war. From Klint Finley at Wired:

“The standard theory, which [Peter] Turchin calls the ‘bottom up’ theory, is that humans invented agriculture around 10,000 years ago, providing resource surpluses that freed people up for other ventures. But what Turchin and his team have found is that the bottom-up theory is wrong, or at least incomplete. ‘Competitions between societies, which historically took the form of warfare, drive the evolution of complex societies,’ he says.

To test the two competing theories, Turchin and company designed two mathematical models for predicting the spread of complex societies. One based only on agriculture, ecology and geography. The other included those three factors, plus warfare. Then, they used data from historical atlases to determine whether these models matched up with the way the different states and empires actually evolved.

The model that included warfare predicted about 65 percent of the historical variance, while the agricultural model explained only about 16 percent, suggesting that warfare was more important in the spread of social norms that lead to complex societies.”