Razib continues his exploration of the interplay of linguistic diversity/homogeneity and socio-economic disparity/prosperity. In a response to a comment, he posted his "bullet points" on
1) a common language across large spaces fosters economies of scale. in other words, it fosters coordination and cooperative by reducing the friction in flow of information.
2) a common language also removes some of the raw material for intergroup conflict. conflict is zero sum, #1 is ideally non-zero sum.