The deep roots of contemporary institutions and outcomes have been in vogue in the social sciences since at least the turn of the millennium. In an impressive body of work (Why Nations Fail: The Origins of Power, Prosperity, and Poverty), Acemoglu and Robinson traced the deep roots of economic development to so-called inclusive institutions. Although inclusive institutions are not, one to one, the same as either direct or representative democracy, the concepts overlap. There are elements of popular participation and institutional constraints on power in both. In this sense, the Deep Roots of Modern Democracy: Geography and the Diffusion of Political Institutions is a complementary project: Acemoglu and Robinson previously traced the deep roots of comparative economic development to inclusive institutions, and now John Gerring, Brendan Apfeld, Tore Wig, and Andreas Forø Tollefsen trace the deep roots of these institutions (or something quite similar).

The deep roots debate in economics pitted three explanatory frameworks against each other: institutions, geography, and integration (trade, essentially). The outcome of that debate was the dictum that “institutions matter”—more so than geography and trade. In light of this conclusion, the book by Gerring et al. is very interesting. It identifies geographical roots of polit