Quantitative historical analysis uncovers a single dimension of complexity that structures global variation in human social organization. - Turchin, P; Currie, T; Whitehouse, H; François, P; Feeney, K; Mullins, D; Hoyer, D; Collins, C; Grohmann, S; Savage, P; Mendel-Gleason, G; Turner, E; et al. (Proceedings of the National Academy of Sciences, 2018)