ESM_Refs from Human societal development: is it an evolutionary transition in individuality?

An evolutionary transition in individuality (ETI) occurs when a previously independent organism becomes a lower level unit within a higher hierarchical level (for example, cells in an organism, ants in a colony). Using archaeological and historical accounts from the last 12 000 years, I empirically examine the proposition that human society increasingly functions as a higher hierarchical level within which individuals integrate as lower level units. I evaluate human societal development with respect to three criteria that together indicate complexity in biological systems and serve as an operationalization scheme for ETIs: size, inseparability and specialization. The <i>size</i> of the largest polity has increased seven orders of magnitude, from hundreds to billions. <i>Inseparability</i> became nearly complete since Mesopotamian city-states, following the first appearance of intricate <i>specialization</i> (division of labour). <i>Connectivity</i> within a polity has increased rapidly during the last few centuries, and particularly within the last few decades. In view of these results, I formulate the following hypothesis: <i>human society is undergoing an evolutionary transition in individuality,</i> driven by socio-cultural-technological processes. This proposition requires a detailed theoretical basis and further empirical testing. I propose four predictions derived from the hypothesis that may be used to test it.This article is part of the theme issue ‘Human socio-cultural evolution in light of evolutionary transitions’.