Running head: EVOLUTIONARY FOUNDATIONS OF POLITICAL IDEOLOGY 1 The dual evolutionary foundations of political ideology Scott Claessens1 Kyle Fischer1 Ananish Chaudhuri2,3 Chris G. Sibley1 Quentin D. Atkinson1,4 1School of Psychology, University of Auckland, New Zealand 2Department of Economics, University of Auckland, New Zealand 3CESIfo, Poschingerstrasse 5 81679 Munich, Germany 4Max Planck Institute for the Science of Human History, Jena, Germany Corresponding author: Quentin D. Atkinson School of Psychology University of Auckland Auckland, 1010 New Zealand Email:
[email protected] ORCID linked to account on Manuscript Tracking System EVOLUTIONARY FOUNDATIONS OF POLITICAL IDEOLOGY 2 1 Abstract 2 What determines our views on taxation and crime, healthcare and religion, welfare and 3 gender roles? And why do opinions about these seemingly disparate aspects of our social 4 lives coalesce the way they do? Research over the last 50 years has suggested that political 5 attitudes and values around the globe are shaped by two ideological dimensions, often 6 referred to as economic and social conservatism. However, it remains unclear why this 7 ideological structure exists. Here, we highlight the striking concordance between these two 8 dimensions of ideology and two key aspects of human sociality: cooperation and group 9 conformity. Humans cooperate to a greater degree than our great ape relatives, paying 10 personal costs to benefit others. Humans also conform to group-wide social norms and punish 11 norm violators in interdependent, culturally marked groups. Together, these two shifts in 12 sociality are posited to have driven the emergence of large-scale complex human societies. 13 We argue that fitness trade-offs and behavioural plasticity have maintained strategic 14 individual differences in both cooperation and group conformity, naturally giving rise to the 15 two dimensions of political ideology.