East - West Orientation of Historical Empires and Modern States

In a chapter entitled “Spacious Skies and Tilted Axes” Jared Diamond (1997) argues that crops and domestic animals are spread more easily along lines of latitude (along an East-West axis) rather than along lines of longitude (along a North-South axis). Diamond suggests that East-West spread is easier because similar climates and soil types tend to be arranged in east-west oriented bands. Th is geographic pattern is fundamental to natural vegetation types and wild animal distributions, and is best illustrated by a map of the global distribution of biomes (Figure 1). A biome is a major type of ecological community such as the grassland, desert, or temperate seasonal forest (Ricklefs 2001). Although Diamond focused primarily on the spread of crop cultivars and domesticated animals, the same principle should infl uence the military/political, demographic, and cultural dynamics of societies. An obvious example which seems to fi t this pattern is the Mongol empire under Chinggis Khan and his