Self-organizing social hierarchy and villages in a challenging society
  We show by Monte Calro (MC) simulation that the hierarchy and villages emerge simultaneously in a challenging society when the population density exceeds a critical value. Our results indicate that among controlling processes of diffusion and fighting of individuals and relaxation of wealth, the trend of individuals challeninging to stronger neighbors plays the pivotal role in the self-organization of the hierarchy and villages. 
Masaru Tsujiguchi and Takashi Odagaki