"A few decades ago it was the fashion to credit the aboriginal peoples of America with a civilization of enormous antiquity. But the whole trend of modern scientific investigation tends to prove that the American continent was one of the last parts of the world to be settled and that at the time of the Spanish conquest the aboriginal cultures were certainly not more than three thousand or so years old. Even this estimate should be understood to include centuries of migratory shiftings and centuries of development along lines which eventually led to the erection of the earlier types of high culture in Middle and South America. Roughly speaking the time of Christ coincides with the period at which the earliest high cultures in this hemisphere