The opinions relating to the origin of man may be reduced to three. In the first place, we will state that of the monogenists, who behold in all the human types scattered over the world only races and varieties of the same species, and regard mankind as descending, or at least as capable of descending, from a single couple primitively sprung from the hands of the Creator. This opinion is evidently conformable to the Bible narrative; this reflection will not escape the sincere Christian, and we must make it at the risk of exciting the pity or indignation of certain positivists, who reproach us with bringing into scientific questions prejudices and arguments which are extra-scientific.
The opinion of the polygenists is diametrically opposed to the preceding. According to them, the typical differences which exist between the races of men are so decided, so profound, that they could not be the result of the conditions of existence; these differences are then original; men, instead of belonging to a single zoological species, form a genera or even a family, the bimanous family; community of origin is then impossible, and the account in Genesis must be considered as legendary.
Lastly, a third school separates itself entirely from the preceding, and considers the question under discussion as a phase of the general question—the stability of the species. The naturalists connected with this school regard the species as something essentially changeable. They deduce this opinion from the examples of the endless varieties of forms which our domestic animals above all others present. It is possible, by known processes, to obtain, after several generations, products so different from the primitive type, that to judge them by the form only we should believe in the existence of a new species; the continued fecundity between the two varieties alone attesting the specific unity of both types. Would it not be possible, by new methods, or by a better employment of the means already known, to arrive at such a complete transformation that the fecundity between the new and the primitive species should cease to exist, or at least cease to be unlimited? We should have thus obtained a novel species by a simple transformation due to the forces of nature. The result which man might obtain at the end of several generations, nature, left to itself, would inevitably arrive at, after a longer or shorter time, according as circumstances should be more or less favorable. This is admitted by Lamark, and the two Geoffroy Saint-Hilaire; it is admitted also by the English naturalist Darwin. The latter regards all animals actually existing as descending from four or five progenitors; an equal number would suffice for plants. He even adds that, guided by analogy, he would willingly admit that, all organized beings, plants and animals, descend from one single primordial type, and that man should constitute no exception to the general laws; he springs from the ape or some extinct type, and thence from the primitive.
It is to this last school that M. Trémaux belongs: the title of his book sufficiently shows it. He concedes the variability and the transformation of the species; but separates himself distinctly from Darwin relative to the causes which produce this variation.
M. Trémaux' book may be summed up entirely in the statement of the great law of the improvement of beings which is printed in large letters on the front page of the first part: "The improvement of creatures is or becomes proportionate to the degree of elaboration of the soil on which they live! And the soil is in general elaborated in proportion as it belongs to a more recent geological formation." To prove this law, and to deduce from it every possible consequence, is the object of the book.
The first requisite in judging a work is to understand its aim or end. Thus we have endeavored to seize the sense and the bearing which the author attaches to the great law he thinks he has discovered. Such a soil gives such a product, we are told. We understand this when the direct fruits of the earth are in question--that is, of the vegetables which draw directly from the earth the principles which should assimilate them. But as to animals, what influence can the soil exercise over them? This is what M. Trémaux should have explained, and what he has forgotten to tell us. Must we understand that the land, by virtue of its chemical and mineralogical composition, possesses a mysterious action of an unknown nature, determining according to the case the improvement or degeneracy of the species of [{847}] animals? Such is in fact the meaning which many passages seem to attribute to this law. Thus, after having shown that the causes generally assigned cannot explain those typical changes which nature presents, the author adds: "By the action of cross-breeding, food, and climate alone, we shall meet with contradictions at every step. With the action of the sun, the whole globe exhibits the same effects." Since it is neither through food nor by climate that the sun acts, it is by some mysterious agency; and behold us thus, in the nineteenth century, thrown back upon occult causes. May we be permitted to observe that this is not scientific?
Entirely engaged in proving by facts the law which must serve as a oasis to his system, M. Trémaux seems never to have thought of explaining to himself the manner of the earth's action. Thus, beside numerous places which clearly imply an immediate action, others could be quoted which only attribute to the soil an indirect action due to the aliments drawn from it. For example, apropos of cretinism, we read: "This scourge is above all endemical, because in fact those persons who can profit by the products of another soil feel in a lesser degree the unfavorable results of that condition." And further on: "To avoid living permanently on a soil which produces cretinism is the sole remedy, or rather the only palliative, against its pernicious effects on man. It is best to abandon it completely, or at least to make use of products other than those destined to feed its inhabitants." In brief, what is necessary to bring humanity to perfection? "Firstly, To choose carefully those lands whose products are more directly intended for man. Secondly, To have recourse to every proper means of improving the land. Thirdly, Planting with suitable trees those lands which are unfavorable to the growth of human food. Fourthly, To subject to agriculture those forest lands which occupy a favorable soil."
These passages appear clear that it is not of itself, but by its productions, and also doubtless through its climate, the soil acts on man and on the animals. This explanation is more philosophical than novel.
Between the monogenists and the polygenists, the question reduces itself very nearly to this: Can beings differing so much as the Europeans and the Bushmen, the Hottentot and the Australian, descend from the same ancestors? No, reply the polygenists; for the differences are greater than those which characterize certain species. In order to meet this objection, the monogenists have had recourse to what is called the middle theory, and to that of the cross-breeds. The whole of the external circumstances under which the representatives of a species exist, constitute what is called the middle or medium, to which monogenists, supporting themselves on undoubted facts, attribute the power of gradually changing the medium type of a species. The crossing of many types thus modified will give birth to new forms, all, however, belonging to one common kind.