Originally Posted by arf

I would have to say Race by far. The reason would be throughout history there have always been conflicts between nations of a different race, whenever two races met either one would go to war or try to enslave the other. Racism is not as bad (thats is people are more tolerant) now but really only in places where there are a diverse group of people living there and that community has existed for a while, though even then it still exist. Even now some families would frown upon or abosolutely forbid inter-racial marriages. I believe that humans have yet to fully outgrow a natural instinct to fear that which is different, that mix with their situtation in life, upbringing, jealousy and other factors contribute to racism. Also it's not just all racism, most people feel more comfortable with people of their own race. I live in Australia which is a pretty diverse place but their are still places where it is pre-dominanly one or two types of race and lot's of countries have a chinatown or little italy of some sort.