The Ant and the Grasshopper: Seasonality and the Invention of Agriculture
Review and Resubmit at Quarterly Journal of Economics

During the Neolithic Revolution, seven populations independently invented agriculture. In this paper, I argue that this innovation was a response to a large increase in climatic seasonality. Hunter-gatherers in the most affected regions became sedentary in order to store food and smooth their consumption. I present a model capturing the key incentives for adopting agriculture, and I test the resulting predictions against a global panel dataset of climate conditions and Neolithic adoption dates. I find that invention and adoption were both systematically more likely in places with higher seasonality. The findings of this paper imply that seasonality patterns 10,000 years ago were amongst the major determinants of the present day global distribution of crop productivities, ethnic groups, cultural traditions, and political institutions.

Militarism and the Mongols: The Persistent Cultural Effects of Pastoral Occupation.

The Mongol Empire was the largest contiguous empire in world history, at the height of its power stretching from China to Turkey. I show that areas that suffered through Mongol rule in the 13th century are still more militaristic today, as evidenced by the answers given by the inhabitants of 273 sub-national regions in the course of the World Value Survey. To address the possibility of endogeneity between differences in pre-existing cultural attitudes, and the decision of Mongols over which areas to occupy, I use distance to the Eurasian Steppe as instrument for invasions by Mongols. The power of the instrument derives from the fact that Mongol warfare was highly livestock-intensive, and all major expeditions had to start from their Steppe homeland. The exclusion restriction is justified by the loss of geopolitical relevance the Steppe suffered after the invention of gunpowder made horse archers obsolete. For the past 500 years, regions closer to the Steppe have been no more likely to suffer invasion than  those facing other ecosystems --- and yet their inhabitants still bear the cultural scars of distant invaders. 

What Have the Romans Ever Done for Us? Aqueduct Suitability and the Administration of Empire

The ancient Romans built over a thousand aqueducts throughout the Empire, supplying  water for private, agricultural, and manufacturing use. To what extent did the engineering superiority of the Romans promote peaceful relations with their subjects? Provinces with many aqueducts were usually under civilian administration, while provinces with fewer aqueducts were generally administered by the commander of the local legion. To limit the possibility of reverse causality between efficient capital investments and sentiment towards the occupiers, I use cross-sectional variation in rainfall and the availability of  natural springs to construct a measure for the usefulness of Roman hydraulic technology. I find that provinces with a greater fraction of dry land within 30km of a suitable spring had more aqueducts, and were also more likely to be under civilian administration.