Cultural assemblage theory: Synthesizing cultural diversity through four processes of community ecology

Evolutionary approaches have provided a powerful framework for explaining how cultural traits emerge, spread, and persist. However, much cultural evolution research remains centred on trait-frequency change within populations and can understate historical contingency, spatial structure, and interactions among coexisting cultural traits. We propose cultural assemblage theory, a community-ecological perspective that treats culture as assemblages of interacting traits, practices, institutions, and beliefs. Building on Vellend’s synthesis in community ecology, we translate four fundamental processes into cultural terms, and argue that their joint action can parsimoniously explain cultural diversity patterns across space and time. Cultural selection captures non-random adoption and retention driven by ecological and social payoffs and learning biases; cultural drift describes stochastic turnover and loss in effectively small cultural populations; cultural dispersal encompasses transmission across boundaries via migration, exchange, and media; and cultural speciation refers to lineage splitting and long-term diversification under isolation, path dependence, and local adaptation. Further, interactions among cultural traits shape assemblage structure and can mediate the four processes. This framework reorganises disparate strands of cultural evolution research into a common process-based language, facilitates comparative inference about the drivers of cultural diversity, and provides a theoretical basis for conserving vulnerable cultural lineages under accelerating global homogenisation.