I cannot enter into all the details required for the complete demonstration of this statement. I limit myself to two facts that I hope will suffice to convince you.
The first is: not a single species of vegetable, not a single species of animal, is found at the same time all over the globe.
The most wide-spread species occupied at first only a small part of the globe, and man must have carried with him not only certain vegetables but also certain annuals, to have them as widely diffused as we find them in our day. Notwithstanding this intelligent and voluntary intervention, you well know that there are certain parts of the globe occupied by man in which neither the vegetables that have accompanied us almost everywhere, nor the animals which we habitually transport, can survive. Man, on the contrary, is cosmopolitan in every sense of the word; that is to say, we find him everywhere, under the ice of the poles, as under the equator.
Hence, if he had originated wherever we find him, he would constitute a single exception among all organic and living beings, whether vegetable or animal.
This reason, by itself, ought to make us accept at least this much: that man has, at all events, peopled a part of the globe by emigration.
But we may go much further; and always, by virtue of the law which I have just stated, we may say that he had his origin in one spot, and that a narrow one.
In fact, when we study animals, we find that the extent occupied by a species, what we call its habitat, is as much less extended as the species is more perfected, more elevated, in the zoological series.
Not only is this true of species, but of types themselves.
Thus, below man, the animal form which most reminds us of the human form is, you know, that of the monkey. Are monkeys among the number of the most widely-distributed animals? No. The monkey-type is found neither in very cold countries nor in the greater part of the temperate regions, but only in the warmest parts of the globe. Besides, a great part of Oceanica contains not a single monkey.
If, now, we no longer consider the type, the entire group of monkeys, but only the species which approaches nearest to us, we see it occupying an area more and more limited. America has not a single species of monkey in common with Africa and Asia. And, when we come to the most perfect monkeys—to those which, by reason of their great resemblance to man, have been called anthropoid, that is, with a human form—we see the area of their habitat is restricted still more and becomes extremely narrow. So the orang-outang, one of those species of monkeys which some have wished to make our ancestor, is found only in the isle of Borneo, or at most, perhaps, in the isle of Sumatra; the gorilla, still another of the species which comes nearest man in his general proportions, occupies only a small part of the western regions of Africa.
