Polyethnicity refers to the proximity of people from different ethnic backgrounds within a country or other specific geographic region. It also relates to the ability and willingness of individuals to identify themselves with multiple ethnicities. It occurs when multiple ethnicities inhabit a given area, specifically through means of immigration, intermarriage, trade, conquest, and post-war land-divisions.Professor William H. McNeill states in his series of lectures on polyethnicity that it is the societal norm for cultures to be made up of many ethnic groups. This has had many political and social implications on countries and regions.
Many, if not all, countries have some level of polyethnicity, with countries like the United States and Canada having large levels and countries like Japan and Poland having very small levels (and more specifically, a sense of homogeneity). The amount of polyethnicity prevalent in current society has spurred some arguments against it, which include a belief that it leads to the weakening of each society's strengths, and also a belief that political-ethnic issues in countries with polyethnic populations are better handled with different laws for certain ethnicities.
In 1985 Professor William H. McNeill, a Canadian historian known for his expertise on the subject of polyethnicity, gave a series of three lectures on polyethnicity in ancient and modern cultures at the University of Toronto. The main thesis throughout the lectures was that it has been the cultural norm for societies to be composed of different ethnic groups. McNeill states that the ideal of homogeneous societies may have grown between 1750 and 1920 in Western Europe due to a growth in the belief in a single nationalistic base for the political organization of society. McNeill believes that World War I was the point in time when the desire for homogeneous nations began to weaken.