He has a new paper on that topic, here is the abstract:
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.
We propose a theory in which geographic attributes explain cross-regional institutional differences in (1) the scale of the state, (2) the distribution of power within state hierarchy, and (3) property rights to land. In this theory, geography and technology affect the transparency of farming, and transparency, in turn, affects the elite’s ability to appropriate revenue from the farming sector, thus affecting institutions. We apply the theory to explain differences between the institutions of ancient Egypt, southern Mesopotamia, and northern Mesopotamia, and also discuss its relevance to modern phenomena.
All of a sudden we are seeing ongoing advances, admittedly connected to speculative hypotheses, in our understanding of this era.