Thus do all the varied lines of evidence proceeding from history, ethnology, and philology converge upon Western Asia as the cradle of the human race--the centre from which the families of mankind departed to people the earth; and we are constrained to regard the early populations of that region as furnishing the _typical_ standard or average sample of our species.
Proceeding from a purely zoological stand-point, we should be led to an opposite conclusion. Looking to the general phenomena of the geographical distribution of animals, and the natural rather than the artificial conditions of human existence, and arguing solely on naturalistic grounds, we should be constrained to place the centre of our race in the tropics; and of the intertropical regions those which are the habitat of the anthropoid (or anthropomorphic) ape, as Western Africa and the southern extremity of Asia. In the protoplasts of his species the mere zoologist sees but so many naked bipeds, with the capabilities, indeed, of working out for their future behoof the essentials of clothing, the use of fire, and the like, but in the first instance unfit for any climate except the mildest, and incapable of sustenance on any soil except the most luxuriant. He consequently fixes upon the tropics as the cradle of our race; and those who assume the lineal descent of the human species from the quadrumana fix upon those intertropical points which are the habitats of the anthropomorphic apes.
The law which governs the distribution and development of vegetable and animal life would also lead us to fix upon the tropical regions as the geographical centre of our race. That law may be thus stated: _The degree of perfection of the types of life, and the diversity and number of species, are proportional to the intensity of heat._ In this progress, as Humboldt has remarked, we find organic life and vigor gradually augmenting with the increase of temperature. And the number of species increases as we approach the equator, and decreases as we retire from it.[389]
In the Frigid Zone life seems almost extinguished during the greater part of the year by the rigors of an almost perpetual winter. The vegetation of the polar regions is stunted, dull, and monotonous in color, and inadequate to sustain animal life. The plains are covered with mosses and lichens, and here and there a few herbs and shrubs (saxifrages, gentians, papaver, etc.), but no stately forest trees. In short, the general characteristic of these cold regions is the preponderance of cryptogamous plants. In the Temperate Zone we have a marked superiority in vegetable life. Here we have grassy pastures, cerealia, and dicotyledonous trees--the oak, ash, beech, maple, chestnut, walnut, the apple, pear, plum, etc. The number of genera and species is greatly increased, and the superior types acquire a fuller development. The preponderance of phanerogamous plants, the richer coloring, and the appearance of evergreen trees, are the signs of an immense progress. But the soft tints, the medium forms, and the wintry sleep extending through half the year, clearly indicate that the perfection of physical nature is not attained.[390] It is in the heat of the Torrid Zone where nature puts forth all her energy, and displays her greatest resources. "The cryptogamous plants attain, in arborescent forms, the proportions of our forest trees. The grasses which we know in our climates only under the humble forms they put on in our fields, rise, in the elegant and majestic bamboo, to the height of sixty or seventy feet. A single tree is a garden, wherein a hundred different plants intertwine their branches, and display their brilliant flowers on a ground of verdure, where their varied hues and forms of leaves are richly blended." And here the perfection of vegetable life is attained in the graceful palms which stand at the head and crown the vegetable kingdom. This is the region of a perpetual summer, where nature makes ample provision for the support of animal life, and the date, the cocoa-nut, the banana, the plantain, the sugar-cane, the pine-apple, supply all the wants of uncivilized man.