I would not, however, deny that local conditions may favour the deepening of some particular skin-colour, the tendency to obesity, the development of the chest muscles, the lengthening of the arms or the lower limbs, the increase or decrease of physical strength. But, I repeat, these are not essential points; and to judge from the very slight difference made by the alteration of local conditions in the shape of the body, there is no reason to believe that they have ever had very much influence. This is an argument of considerable weight. Although we do not know what cataclysmal changes may have been effected in the physical organization of the races before the dawn of history, we may at least observe that this period extends only to about half the age attributed to our species. If for three or four thousand years the darkness is impenetrable, we still have another period of three thousand years, of which we can go right back to the beginning in the case of certain nations. Everything tends to show that the races which were then known, and which have remained relatively pure since that time, have not greatly changed in their outward appearance, although some of them no longer live in the same places, and so are no longer affected by the same external causes. Take, for example, the Arabs of the stock of Ishmael. We still find them, just as they are represented in the Egyptian monuments, not only in the parched deserts of their own land, but in the fertile, and often damp, regions of Malabar and the Coromandel Coast, in the islands of the Indies, and on many points of the north coast of Africa, where they are, as a fact, more mixed than anywhere else. Traces of them are still found in some parts of Roussillon, Languedoc, and the Spanish coast, although almost two centuries have passed away since their invasion. If the mere influence of environment had the power, as is supposed, of setting up and taking away the limits between organic types, it would have not allowed these to persist so long. The change of place would have been followed by a corresponding change of form.