Societies evolve in steps

From Nature:

Human societies progress in small steps just as biological evolution does, according to a study of the structure and language of societies in South East Asia and the Pacific Ocean.

“One of the big debates in anthropology has been whether there are any recurring patterns or processes in the way societies change over time,” says Tom Currie of University College London, who led the study published in Nature today¹. He and his team wanted to know whether societies increase in complexity through a limited number of different forms — from tribe, to chiefdom, state and empire — or whether different societies each have their own pattern. Their analysis, which uses quantitative methods borrowed from genetics, supports a popular model of political evolution which suggests that societies show a gradual increase in complexity. But the data also back up another theory — societies can decrease in complexity, too, either by the same pattern of small steps or by bigger crashes.

More here.