Instability and violence in Imperial Rome: A “laboratory” for studying social contagion?

Imperial Rome with its >50% assassination rate of emperors, many of whom are depicted in history as ‘deranged’, initially appears a chaotic period of history beyond the purview of science. But time series analysis indicates this violence occurred non‐randomly: reign length was autocorrelated and demonstrated ‘memory persistence,’ and short reigns occurred in clusters. Additionally, deviations from average reign‐length occurred in patterns matching the Empire's rise and decline. A model is proposed for how army‐backed usurpation and post‐coup instability likely generated the observed cycles. The five‐century span of Imperial Rome likely makes it the longest‐lived regime with fair documentation, and potentially provides a ‘laboratory’ with ongoing relevance for studying transmission of violence and instability. © 2016 Wiley Periodicals, Inc. Complexity 21: 613–622, 2016