The human group evidently constitutes one genus; if it consisted only of one species, it would form a single exception in creation. It is, therefore, but natural to presume, that this genus is, like all the others, composed of different species. In the greater number of genera, the various species differ much less from each other than certain human races. A naturalist, who, without touching the question of origin, purely and simply applies to the human genus the general principles of zootaxis, would be inclined to divide this genus into different species. This mode of viewing the subject can only be abandoned, if it were by observation demonstrated that all the difference between human races had been the result of modifications caused in the organisation of man by the influence of media. The monogenists have at first made great efforts to furnish such a demonstration, but without success. Observation has, on the contrary, shown, that though the organisation of man may, in the course of time, and under the influence of external conditions, undergo some modification, yet that these modifications are relatively very slight, and have no relation to the typical differences of human races. Man, transplanted into a new climate, and subjected to a new mode of life, conserves and transmits to posterity all the essential characters of his race, and his descendants do not acquire the character of the indigenous race or races. _Cœlum, non corpus mutant qui trans mare currunt._ The monogenists have objected that the period of distant colonies is too recent; that the observations tending to establish the permanence of human types date scarcely from three or four centuries, and that this lapse of time is insufficient to produce a transformation of races, and that such a transformation has been produced gradually during the long series of centuries elapsed, according to some from the creation of man, and according to others since the Deluge. But the study of the Egyptian paintings has shown, that on the one hand the principal types of the human genus existed then, 2,500 years at least before Jesus Christ, as they exist at this day. Again, the Jewish race, scattered for more than eighteen centuries in the most different climates, is everywhere the same now as it was in Egypt at the time of the Pharaohs. The period of _positive_ observations dates thus, from more than forty centuries and not from three or four.[82]