Diana makes a great point about the need for loose restrictions on human migration. In general, resistance I have seen to immigration in the United States and Europe comes partially from irrational fears or ignorance of basic economic principals. However, the primary motivation I have observed stems from blind racial, sectarian, and nationalistic passions. Such idiocy should have been abandoned in the 19th century. Nation-states themselves are merely artifacts of the Congress of Vienna and need to be completely rethought in the 21st century. They only serve to deepen the imbalances and poverty that already exist.