“The idea of the simple linear development of society from the culture of the paleolithic (Old Stone Age) through the successive stages of the neolithic (New Stone Age), Bronze, and Iron Ages must be given up. Today we find primitive cultures co-existing with advanced modern society on all the continents-the Bushmen of Australia, the Bushmen of South Africa, truly primitive peoples in South America, and in New Guinea; some tribal peoples in the United States. We shall now assume that, some 20,000 or more years ago, while paleolithic peoples held out in Europe, more advanced cultures existed elsewhere on the earth, and that we have inherited a part of what they once possessed, passed down from people to people.”