_three principal divisions of human speech_. Hence the trilingual inscriptions of Behistun, Persepolis, etc., which consist of an Indo-European, a Tâtar, and a Semitic column."[388] 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]