The Red Man's Continent [12]
Africa shows how an equatorial position retards evolution. The still more marked backwardness of Australia with its kangaroos and duck-billed platypuses shows how much greater is the retardation when a continent is also small and isolated. Today, no less than in the past, the tetrahedral form of the earth and the relation of the tetrahedron to the poles and to the equator preserve the conditions that favor rapid evolution. They are the dominant factors in determining that America shall be one of the two great centers of civilization.
If North and South America be counted as one major land mass, and Europe, Asia, and Africa as another, the two present the same general features. Yet their mountains, plains, and coastal indentations are so arranged that what is on the east in one is on the west in the other. Their similarity is somewhat like that of a man's two hands placed palms down on a table.
On a map of the world place a finger of one hand on the western end of Alaska and a finger of the other on the northeastern tip of Asia and follow the main bones of the two continents. See how the chief mountain systems, the Pacific "cordilleras," trend away from one another, southeastward and southwestward. In the centers of the continents they expand into vast plateaus. That of America in the Rocky Mountain region of the United States reaches a width of over a thousand miles, while that of Asia in Tibet and western China expands to far greater proportions.
From the plateaus the two cordilleras swing abruptly Atlantic- ward. The Eurasian cordillera extends through the Hindu Kush, Caucasus, and Asia Minor ranges to southern Europe and the Alps. Then it passes on into Spain and ends in the volcanoes of the Canary Islands. The American cordillera swings eastward in Mexico and continues as the isolated ranges of the West Indies until it ends in the volcanoes of Martinique. Central America appears at first sight to be a continuation of the great cordillera, but really it is something quite different--a mass of volcanic material poured out in the gap where the main chain of mountains breaks down for a space. In neither hemisphere, however, is the main southward sweep of the mountains really lost. In the Old World the cordillera revives in the mountains of Syria and southern Arabia and then runs southward along the whole length of eastern Africa. In America it likewise revives in the mighty Andes, which take their rise fifteen hundred miles east of the broken end of the northern cordillera in Mexico. In the Andes even more distinctly than in Africa the cordillera forms a mighty wall running north and south. It expands into the plateau of Peru and Bolivia, just as its African compeer expands into that of Abyssinia, but this is a mere incident. The main bone, so to speak, keeps on in each case till it disappears in the great southern ocean. Even there, however, it is not wholly lost, for it revives in the cold, lofty continent of Antarctica, where it coalesces once more with the other great tetrahedral ridges of Africa and Australia.
It is easy to see that these great cordilleras have turned most of the earth's chief rivers toward the Atlantic and the Arctic Oceans. That is why these two oceans with an area of only forty-three million square miles receive the drainage from twenty million square miles of land, while the far larger Indian and Pacific Oceans with an area of ninety-one million square miles receive the rivers of only ten million square miles. The world's streams of civilization, like the rivers of water, have flowed from the great cordilleras toward the Atlantic. Half of the world's people, to be sure, are lodged in the relatively small areas known as China and India on the Pacific side of the Old World cordillera. Nevertheless the active streams of civilization have flowed mainly on the other side--the side where man apparently originated. From the earliest times the mountains have served to determine man's chief migrations. Their rugged fastnesses hinder human movements and thereby give rise to a strong tendency to
If North and South America be counted as one major land mass, and Europe, Asia, and Africa as another, the two present the same general features. Yet their mountains, plains, and coastal indentations are so arranged that what is on the east in one is on the west in the other. Their similarity is somewhat like that of a man's two hands placed palms down on a table.
On a map of the world place a finger of one hand on the western end of Alaska and a finger of the other on the northeastern tip of Asia and follow the main bones of the two continents. See how the chief mountain systems, the Pacific "cordilleras," trend away from one another, southeastward and southwestward. In the centers of the continents they expand into vast plateaus. That of America in the Rocky Mountain region of the United States reaches a width of over a thousand miles, while that of Asia in Tibet and western China expands to far greater proportions.
From the plateaus the two cordilleras swing abruptly Atlantic- ward. The Eurasian cordillera extends through the Hindu Kush, Caucasus, and Asia Minor ranges to southern Europe and the Alps. Then it passes on into Spain and ends in the volcanoes of the Canary Islands. The American cordillera swings eastward in Mexico and continues as the isolated ranges of the West Indies until it ends in the volcanoes of Martinique. Central America appears at first sight to be a continuation of the great cordillera, but really it is something quite different--a mass of volcanic material poured out in the gap where the main chain of mountains breaks down for a space. In neither hemisphere, however, is the main southward sweep of the mountains really lost. In the Old World the cordillera revives in the mountains of Syria and southern Arabia and then runs southward along the whole length of eastern Africa. In America it likewise revives in the mighty Andes, which take their rise fifteen hundred miles east of the broken end of the northern cordillera in Mexico. In the Andes even more distinctly than in Africa the cordillera forms a mighty wall running north and south. It expands into the plateau of Peru and Bolivia, just as its African compeer expands into that of Abyssinia, but this is a mere incident. The main bone, so to speak, keeps on in each case till it disappears in the great southern ocean. Even there, however, it is not wholly lost, for it revives in the cold, lofty continent of Antarctica, where it coalesces once more with the other great tetrahedral ridges of Africa and Australia.
It is easy to see that these great cordilleras have turned most of the earth's chief rivers toward the Atlantic and the Arctic Oceans. That is why these two oceans with an area of only forty-three million square miles receive the drainage from twenty million square miles of land, while the far larger Indian and Pacific Oceans with an area of ninety-one million square miles receive the rivers of only ten million square miles. The world's streams of civilization, like the rivers of water, have flowed from the great cordilleras toward the Atlantic. Half of the world's people, to be sure, are lodged in the relatively small areas known as China and India on the Pacific side of the Old World cordillera. Nevertheless the active streams of civilization have flowed mainly on the other side--the side where man apparently originated. From the earliest times the mountains have served to determine man's chief migrations. Their rugged fastnesses hinder human movements and thereby give rise to a strong tendency to