The extraordinarily high percentage of blood group O in "ancient" or otherwise isolated populations also testifies to its great age. (6) Even though the early migrations dispersed the gene for group O blood throughout the world, there are some extraordinary examples of "old" populations existing in our world today. Because of their geographic locations, these societies have remained isolated from interaction with other populations. If A, B and O had developed simultaneously, the isolated population groups would have had all of them. But these "old societies" are group O because genes for the later blood groups never had the opportunity to enter into their populations. They have remained unchanged.