Ait Benhaddou Kasbah or Ksar in Morocco, GavinD,

In a recent PLOS One paper, a team of evolutionary biologists at Stanford examined why most human cultures have a class structure instead of being egalitarian; they conclude that the very inequities of the class system were the driver for its global spread.

By modeling the destabilizing effects associated with the unequal distribution of resources in stratified societies, SFI External Professor and Science Board Co-Chair Marcus Feldman and collaborators compared demographic stability and rates of migration to determine why hierarchical societies historically outnumber their egalitarian counterparts. 

They found that higher migration rates arise when resources are scarce and members of a population go in search of additional resources. Such migration often results in the creation of new stratified societies.

"This is the first study to demonstrate a specific mechanism by which stratified societies may have taken over most of the world," Feldman said.

Read the PLOS One paper (September 21, 2011)

Read the Stanford University News article (September 23, 2011)

Read the Science a GoGo article (September 29, 2011)