and down the mountain valleys toexchange their pastoral prod- ucts, such as hides, wool, and the like, for what the town can furnish in the way of necessary implements or cloth. A man born at an altitude of 12,000 feet who is accustomed from child- hood to steep mountain ascents and who knows no other en- vironment cannot possibly look upon the greater part of his region as a barrier. To him it is all the world there is, and it is good, If, as happens in the Central Andes, all the peoples he comes in contact with are of like nature, follow the same occupations, live in the same type of house, make their living in the same way, his exchanges with them and all his knowl- edge lead him to look upon a high plateau and high mountain valley as the natural home of man. Because the mountain zone is broad in Peru and Bolivia, there was scope for the develop- ment of an extensive civilization. We find much the same type of life among the primitive inhabitants from the top of the woodland zone on the east to the desert zone on the west. Were that zone narrow, the population upon one side would have little influence on that of the other and indeed might have been drawn off to lower elevations. As it is, they have developed a distinctive civilization which we may say has been held together and has developed in part because of the very breadth and height of the zone.
Farther south the Puna de Atacama has such rigorous cli- matic conditions that the population is forcibly excluded every winter. Yet in spite of this exclusion there is a bond be- tween the populations on the two sides, and it has existed down to this day by reason of the fact that the country was settled by pioneers from the north and west. We need to cor- rect the common view that mountains perforce exercise a dividing influence, for an opposite conclusion is drawn from a study of many fields besides the Central Andes. In the Pyre- nees, the people living in different valleys frequently made agreements regarding pasture nights and the dues to be paid by their respective flocks while on their annual migrations. From the thirteenth century down to the eighteenth there are many evidences of the unifying influence of these moun- tain valleys upon the people inhabiting them. Favoring
