The arrival of the Crô-Magnons and the introduction of the Aurignacian industry are the first events of the prehistory of Europe to which we can assign a date with any degree of confidence; they correspond geologically with the close of the fourth glaciation and the beginning of Postglacial time, the duration of which has been estimated by geologists from evidence of many different kinds, but which brings us, nevertheless, to substantially similar conclusions. It seems that 25,000 years is a conservative estimate for the duration of the Postglacial Period; this is supported by the independent observations of Lyell, Taylor, Penck and Brückner, and Coleman; it is within the estimates made by Chamberlin and Salisbury, Fairchild, Sardeson, and Spencer; it is somewhat larger than the estimates of Gilbert and Upham.[AJ] Thus, with considerable confidence we may record man of the modern type of _Homo sapiens_ as entering western Europe between 25,000 and 30,000 years ago. The Lower Palæolithic industrial cycle, comprising the Chellean, Acheulean, and Mousterian, seems to have been similar in evolution both around the Mediterranean coasts and in the northern portions of Europe. From the fact that the Crô-Magnons arrived with the Aurignacian industry it would appear that they came through Phœnicia and along the southern coasts of the Mediterranean, through Tunis, into Spain; also perhaps along the northern coasts of the Mediterranean through Italy. Their evolution had probably taken place somewhere on the continent of Asia, for their physical structure is entirely of Asiatic type, and not in the least of African or Ethiopian type; that is, they exhibit no negroid characters whatever. The reason that Breuil considers that the Aurignacian did not come in through central or eastern Europe is that there are no early Aurignacian stations in either region, whereas the Aurignacian is abundantly developed along the Mediterranean coasts, both of Europe and Africa. The passage of the Crô-Magnons along these coasts was, therefore, like the subsequent wave of the true Mediterranean race, dark-haired, long-headed, narrow-faced people, which followed this coast in early Neolithic times, or, again, like the wave of the Arabian or Moslem advance, which pressed forward along the northern coast of Africa and into southwestern Europe. [Illustration: FIG. 131. Entrance to the great _Grotte du Prince_ at the base of the limestone promontory known as the _Baoussé Roussé_, with a view of Mentone in the distance. After Davanne.]