Whatever may be thought of the many changes which have taken place, whether they are regarded as the result of distinct and independent creations or as the result of transformations, no geologist can doubt that an immense tract of time was required for the production of these forms. In the Middle Miocene there is not a single species of mammal which corresponds to any of our extant species. If we start from the standpoint of simple palæontology, it would be difficult to assume that the being which shaped the flints at Thenay can have remained unaltered in the midst of all these changes. If, as Gaudry remarks, it can be shown that the flints collected by Bourgeois in the Beauce limestone were really artificially shaped, he as a geologist would not hesitate to recognize in the _Dryopithecus_ the author of this handiwork.[133] But, speaking provisionally, the _Dryopithecus_ which is assumed to have used these flints, and of which we, unfortunately, know only the little which can be gleaned from a few fragments of bone, must remain the object of an interesting hypothesis, so far as his advanced anthropomorphism is concerned. No anthropoid now in existence has shown itself capable of adapting stones, etc., to his personal use. Moreover, the most fanatical advocates of the doctrine of descent are becoming ever more convinced that man cannot be the issue of any extant form of anthropoids. It is true that a close, and in many respects a very close, physical connection may be traced between men and anthropoids, but not the possibility of a direct descent from the one to the other. This is especially shown from the physical development of the larger apes, which only strongly resemble men in their youthful stages, and lose this character more and more as they grow older. The absolute deficiency of any capacity for the further development of the intellectual qualities of our modern species of anthropoids is another proof of this fact; their intelligence is, indeed, higher than that of other mammals, and also of other apes, but they are still far behind the intelligence of man, which is capable of still further development.