East-West Orientation of Historical Empires and Modern States

Abstract

Jared Diamond (1997) hypothesized that if environment is important in limiting the spread of cultures, cultural units would also tend to extend more broadly along lines of latitude than along lines of longitude. We test this hypothesis by studying the range shapes of (a) historical empires and (b) modern states. Our analysis of the 62 largest empires in history supports this conjecture: there is a statistically significant tendency to expand more east-west than north-south. Modern states also show this trend, although the results are not statistically significant.