Mixing of human race happens only through sex, not through migration. Migration simply kills a sense of unity among people. Living in a place where you find people (expat community) from across the world, majority seems to be indifferent to someone who doesn't belong to their nationality or religion or race. It is hilarious as well as disturbing to see people in public transportations like buses and metro trains offering seats to people belonging to own nationalities ignoring someone who are standing near to them. The only exceptions is the men from the Middle Eastern countries who even bid you good bye. Inter-racial, inter-religious marriages could help change the situation by raising up children beyond geographical and racial lines.