Fascinating new paper by Lewis Davis at Union College (gated) arguing that the need for collaboration in early agricultural societies with highly variable rainfall led to the development of cultural norms of not fighting over water:

The link between rainfall variation and individual responsibility draws on an extensive theoretical and empirical literature on risk sharing among agricultural households in less developed countries…. I develop a model of informal risk sharing in which attitudes toward collective responsibility are endogenous, determined by the efforts of parents to socialize their children. Parents are willing to incur socialization costs because greater levels of collective responsibility permit their children to credibly commit to larger transfers in an informal risk sharing arrangement. The model predicts the equilibrium level of collective responsibility will be greater where nature is more capricious.

Much math follows, leading to the conclusion that high rainfall variability leads to the general development of more cooperation, less fighting. The tip here came from Tyler Cowan, who makes fun of England and has links to several earlier, ungated versions of the paper. (link fixed, thanks TB for the corrective)