We start, therefore, with this undoubted fact, that a period of 6000 or 7000 years has been insufficient to make any perceptible change in the types of pure races, whether of the animal or of human species. And doubtless this period might be greatly extended if we had historical records of the growth of Egyptian civilization in the times prior to Menes, for in the earliest records we find accounts of wars both with the Nahsu and the Lebu, implying large populations of those races already existing both to the south and west of the valley of the Nile. These positive dates carry us back so far that it is of little use to investigate minutely the differences of races shown by the remains of the neolithic period. They were very marked and numerous, but we have no evidence to show that they were different from those of more recent times, or that their date can be certainly said to be much older than the oldest Egyptian records. All we can infer with certainty is, that whether the neolithic period be of longer or shorter duration, no changes have taken place in the animal fauna contemporary with man which cannot be traced to human agency or other known causes. No new species have appeared, or old ones disappeared, in the course of natural evolution, as was the case during the quaternary and preceding geological periods. The neolithic is, however, a mere drop in the ocean of time compared with the earlier periods in which the existence of palæolithic man can be traced by his remains; and as far back as we can go we find ourselves confronted by the same fact of a diversity of races. As we have seen in the chapter on Quaternary man, Europe, where alone skulls and skeletons of the palæolithic age have been discovered, affords at least three very distinct types--that of Canstadt, of Cro-Magnon, and of Furfooz.