Isolation of the southern continents.
This subordination of the southern continents is partly due to the fact that they have only one side of contact or neighborhood with any other land, that is, on the north; yet even here the contact is not close. In Australia the medium of communication is a long bridge of islands; in America, a winding island chain and a mountainous isthmus; in Africa, a broad zone of desert dividing the Mediterranean or Eurasian from the tropical and Negroid part of the continent. Intercourse was not easy, and produced clear effects only in the case of Africa. Enlightenment filtering in here was sadly dimmed as it spread. Moreover it was delayed till the introduction from Asia of the horse and camel, which were not native to Africa, and which, as Ratzel points out, alone made possible the long journey across the Sahara. The opposite or peninsular sides, running out as great spurs from the compacter land-masses of the north, look southward into vacant wastes of water, find no neighbors in those Antarctic seas. Owing to this unfavorable location on the edge of things, they were historically dead until four centuries ago, when oceanic navigation opened up the great sea route of the Southern Hemisphere, and for the first time included them in the world's circle of communication. But even when lifted by the ensuing Europeanizing process, they only emphasize the fundamental dependence of the Southern Hemisphere upon the superior geographical endowments of the Northern.
Effect of continental structure upon historical development.
The build of the land-masses influences fundamentally the movements and hence the development of the races who inhabit them. A simple continental structure gives to those movements a few simple features and a wide monotonous distribution which checks differentiation. A manifold, complex build, varied in relief and ragged in contour, breaks up the moving streams of peoples, turns each branch into a different channel, lends it a distinctive character through isolation, finally brings it up in a cul de sac formed by a peninsula or mountain-rimmed basin, where further movement is checked and the process of local individualization begins. Therefore great simplicity of continental build may result in historical poverty, as in the flat quadrangle of European Russia, the level plateau of Africa, and the smooth Atlantic slope of North America, with its neatly trimmed outline. Complexity, abounding in contrasted environments, tends to produce a varied wealth of historical development. Africa lies on the surface of the ocean, a huge torso of a continent, headless, memberless, inert. Here is no diversity of outward form, no contrast of zonal location, no fructifying variety of geographic conditions. Humanity has forgotten to grow in its stationary soil. Only where the Suez Isthmus formed an umbilical cord uniting ancient Egypt to the mother continent of Asia was Africa vitalized by the pulse of another life. European influences penetrated little beyond the northern coast.
Asia, on the other hand, radiating great peninsulas, festooned with islands, supporting the vast corrugations of its highlands and lowlands, its snow-capped mountains and steaming valleys, stretching from the Equator through all the zones to the ice-blocked shores of the Arctic, knowing drought and deluge, tundra waste and teeming jungle, has offered the manifold environment and segregated areas for individualized civilizations, which have produced such far-reaching historical results. The same fact is true of Europe, and that in an intensified degree. Here a complex development of mountains and highlands built on diverse axes, peninsulas which comprise 27 per cent. and Islands which comprise nearly 8 per cent. of the total area,[772] vast thalassic inlets cleaving the continent to the core, have provided an abundance of those naturally defined regions which serve as cradles of civilization and, reacting upon the continent as a whole, endow it with lasting historical significance.[773] Even Strabo saw this. He begins his description of the inhabited world with Europe, because, as he says, it has such a "polymorphous formation" and is the region most favorable to the mental and social ennoblement of man.[774]
Structure of North and South America.
In North and South America, great simplicity of continental build gave rise to a corresponding simplicity of native ethnic and cultural condition. There is only one marked contrast throughout the length of this double continent, that between its Atlantic and Pacific slopes. On the Atlantic side of the Cordilleras, a vast trough extends through both land-masses from the Arctic Ocean to Patagonia; this has given to migration in each a longitudinal direction and therefore constantly tended to nullify the diversities arising from contrasted zonal conditions. On the Pacific side of North America, there has been an unmistakeable migration southward along the accessible coast from Alaska to the Columbia River, and down the great intermontane valleys of the western highlands from, the Great Basin to Honduras;[775] while South America shows the same meridional movement for 2,000 miles along the Pacific coast and longitudinal valleys of the Andes system. There was little encouragement to cut across the grain of the continents. The eastern range of the Cordilleras drew in general a dividing line between the eastern and western tribes.[776] Though Athapascans from the east overstepped it at a few points in North America, the Great Divide has served effectually to isolate the two groups from one another and to draw that line of linguistic cleavage which Major Powell has set down in Ms map of Indian linguistic stocks. Consequently, Americanists recognize a distinct resemblance among the members of the North Atlantic group of Indians, as among those of the South Atlantic group; but they note an equally distinct contrast between each of them and its corresponding Pacific group. Nor is this contrast superficial; it extends to physical traits, temperament and culture,[777] and appears in the use of the vigesimal system of enumeration in primitive Mexico, Central America, among the Tlingits of the Northwest coast and the Eskimo as also among the Chukches and Ainus of Asia, while in the Atlantic section of North America the decimal system, with one doubtful exception, was alone in use.[778]