One point seems quite clear, that monogeny is only possible by extending the date of human origins far back into the Tertiaries. On any short-dated theories of man's appearance upon earth--as for instance that of Prestwich, that palæolithic man probably only existed for some 20,000 or 25,000 years before the neolithic period--some theory like that of Agassiz, of separate creations in separate zoological provinces, follows inevitably. If the immense time from the Miocene to the Recent period has been insufficient to differentiate the Hylobates and Dryopithecus very materially from the existing anthropoid apes, a period such as 40,000 or 50,000 years would have gone a very little way in deriving the Negro from the white, or the white from the Negro. To deny the extension of human origins into the Tertiaries is practically to deny Darwin's theory of evolution altogether, or to contend that man is an exception to the laws by which the rest of the animal creation have come into existence in the course of evolution. The question of the locality in which the human species first originated depends also very materially on the date assigned for human origins. The various speculations which have been hazarded on this subject are almost all based on the supposition that this origin took place in comparatively recent times when geographical and other causes were not materially different from those of the present day. It was for ages the accepted belief that all mankind were descended primarily from a single pair of ancestors, who were miraculously created in Mesopotamia, and secondarily from three pairs who were miraculously preserved in the ark in Armenia. This of course never had any other foundation than the belief in the inspired authority of the Bible, and when it came to be established that this, as regards its scientific and prehistoric speculations, was irreconcilable with the most certain facts of science, the orthodox account of the Creation fell with it. The theory of Asiatic origin was, however, taken up on other grounds, and still lingers in some quarters, mainly among philologists, who, headed by Max Müller, thought they had discovered in Sanscrit and Zend the nearest approach to a common Aryan language. Tracing backwards the lines of migration of these people, the Sanscrit-speaking Hindoos and the Zend-speaking Iranians, they found them intersecting somewhere about the Upper Oxus, and jumped at the conclusion that the great elevated plateau of Pamir, the "roof of the world," had been the birthplace of man, as it was of so many of the great rivers which flowed from it to the north, south, east, and west. This theory, however, has pretty well broken down, since it has been shown that other branches of the Aryan languages, specially the Lithuanian, contain more archaic elements than either Sanscrit or Zend; that language is often no conclusive test of race; that Aryan migrations have quite as often or oftener been from west