Consensus, cooperation and collective intelligence in foraging societies

Consensus-based collective decision-making is a common feature of political life in hunter-gatherer (forager) societies. In this paper, we ask why. Synthesising evidence from anthropology and experimental social psychology, we argue that consensus-based decision-making is an adaptive design feature of groups for efficiently processing information and facilitating good judgements, thereby increasing collective intelligence. Consensus-based decision-making facilitates information flow in several ways: by encouraging high viewpoint diversity; by placing an emphasis on independent judgements; by encouraging leadership that is informal, temporary and knowledge-based; by encouraging inclusive deliberative norms; and by aiding in the construction of a shared reality and meaning among group members. We further argue that consensual political behaviour is part of a coordination game: deliberation preceding decisions serves as a form of pregame talk that refines mutual expectations of effort and reward, signals cooperative intent, elicits cooperation and refines coordination, all of which is hypothesised to result in better group decisions (ie higher collective intelligence). We sketch an evolutionary scenario for the emergence of consensus-based decision-making, which likely prevailed as the modal political form during the Palaeolithic.