Turchin has made contributions to the fields of population ecology, cultural evolution, and historical dynamics. He is one of the founders of cliodynamics, the scientific discipline at the intersection of historical macrosociology, cliometrics, and mathematical modeling of social processes. Turchin developed an original theory explaining how large historical empires evolve by the mechanism of multilevel selection. His research on secular cycles has contributed to our understanding of the collapse of complex societies as has his re-interpretation of Ibn Khaldun's asabiyya notion as "collective solidarity". Of special importance is his study of the hypothesis that population pressure causes increased warfare. This hypothesis has been criticized on empirical grounds. Studies focusing on specific historical societies and analyses of cross-cultural data have failed to find positive correlation between population density and incidence of warfare. Turchin, in collaboration with Korotayev, has shown that such negative results do not falsify the population-warfare hypothesis. Population and warfare are dynamical variables. If their interaction causes sustained oscillations, then we do not in general expect to find strong correlation between the two variables measured at the same time. Turchin and Korotayev have explored mathematically what the dynamical patterns of interaction between population and warfare might be in stateless and state societies. Next, they tested the model predictions in several empirical case studies: early modern England, Han and Tang China, and the Roman Empire. Their empirical results have supported the population-warfare theory: Turchin and Korotayev have found that there is a tendency for population numbers and internal warfare intensity to oscillate with the same period but shifted in phase. Furthermore, they have demonstrated that the rates of change of the two variables behave precisely as predicted by the theory: population rate of change is negatively affected by warfare intensity, while warfare rate of change is positively affected by population density. In 2010 Turchin published research using 40 combined social indicators to predict that there would be worldwide social unrest in the 2020s. He subsequently cited the success of Donald Trump's 2016 presidential campaign as evidence that “negative trends seem to be accelerating” and that there has been an “unprecedented collapse of social norms governing civilized discourse”.
Publications
Turchin has published over 200 scientific articles and at least seven books. Books Selected journal articles
