During the Holocene, human societies grew significantly in scale and complexity, evolving from small groups of hunters and foragers into intricate civilizations. We identify the combination of increased agricultural productivity and advancements in military technology—particularly iron weapons and cavalry during the first millennium BCE—as the key drivers of this transformation.
This visual narrative explores how these forces have intertwined over millennia, shaping social complexity from 10,000 BCE to 1800 CE.
Using the metaphor of blossoms, we depict the rise and fall of polities, while clouds symbolize crucial developments in 
agriculture, 
military technologies, and their combined effects on 
societies.
Glossary
Social complexity refers to the structure and organization of societies, measured by their scale (population, territory, and largest settlement size), hierarchical complexity (levels of administrative, military, and settlement hierarchy), governance specialization (sophistication of governmental institutions), infrastructure, information systems, and systems of economic exchange.
Agricultural productivity is a measure of how intensive agricultural practices were in each polity, proxied by tons of main carbohydrate crop produced per hectare per year.
Military technologies refers to the sophistication and variety of military technologies used by polities, a signal of cooperative investment in military preparedness in response to external threats. We use this as a proxy for the intensity of inter-societal conflict. key military revolutions like 
iron weaponry and 
cavalry are symbolized by petal color.
Publication
Peter Turchin et al., Disentangling the evolutionary drivers of social complexity: A comprehensive test of hypotheses. Sci. Adv. 8, eabn3517(2022). DOI: 10.1126/sciadv.abn3517
