Research on discrimination‏

geez - just walk into a neighborhood bar and see how the locals act about anyone consideerred an "outsider" coming in.

It's all about feeling threatened - kind of like territory rights.

Birds of feather stick together. For security creatures stick together or stay near other harmless creatures eg. deer would stand near a giraffe or a zebra if a lion is near but if the danger is gone the deer would most likely be near its family. That is at a low level.

You will notice several minorities would get along quite well. But those same minorities could have national conflicts with each other. When the British were in control in India the Hindus and Pakistanis banded together against British rule. Once the British left the Hindus and the Muslims were at each other's throats. The dominant common enemy usually leads to cooperation and once the uniting factor, the common enemy, disappears the various groups seek their own kind and factionalism again becomes a factor. However, over time the various groups could assimilate and could become one whole nation as the various groups learn and accept the differences and appreciate them. The short term leads to social fracturing but the long term effect would be assimilation.