By the side of this creating influence we must recognise in the medium a parallel destructive influence. Now, we can appreciate this every day. The present tells us about the past; we cannot doubt but that species formerly disappeared exactly as we see them still disappear under our eyes by the manifestation of some new condition of the medium; these may be sudden; volcanic phenomena, floods, extreme variations of temperature, diseases, famines, enemies--all these hypotheses are possible, and all equally reasonable: the _dodo_ has disappeared some years ago, having been destroyed by the hand of man; they say that the _apterix_ will soon disappear in the same way, devoured by cats. But actions only moderately destructive were doubtless otherwise very important, and we find here all the phenomena which have been so well described, and so well explained by Darwin[320] under the name of _vital competition_. By this we see, even since the most ancient historic periods, that certain savage animals, like the lion,[321] crocodile,[322] and hippopotamus,[323] retire before mankind; that the black rat is disappearing in Europe to give place to the field mouse, and that a race of savages disappears when their country begins to be inhabited by a more civilised race, even when the victors in this organic, as well as political, struggle, are not able to reproach themselves with any cruelty. Now, let us apply to man the theory of the origin of species which we wish to be dominant, for there is no reason to think that man forms any exception to the common rule. Before all things, we must remember that human races cannot lend themselves to any classification in natural series. It is also as impossible for the naturalist to point out a race at the present day from which all the others are derived, either parallelly or successively, as for the historian to discover in the past any trace of a homogeneous humanity. If even such an uniformity had ever existed, how would the remembrance of it have been kept, for it is evident that this primitive form, constituting at the beginning all the human genus, would be the same _inferior_ form, such as the Negro or the Bosjesman, for instance, nature rising in general from inferiority to perfection. This was for a long time Prichard’s idea, and certain monogenists think the same at the present day. This hypothesis, entering at its basis into the doctrine of evolution, has nothing in itself which is startling; we can only say one thing against it, and that is in its admitting as proved that filiation which would connect one with the other all the groups composing in our times the genus _homo_. For our part, we wish simply to extend the same manner of viewing the matter, to generalise it, and to place it in relation with this immense unknown which is behind us, and of which monogenists do not take enough notice. We maintain that there has existed in the night of time a certain species, less perfect than the most imperfect