The chief source of the change which swept over western Europe lay in the brain power of the Crô-Magnons, as seen not only in the large size of the brain as a whole but principally in the almost modern forehead and forebrain. It was a race which had evolved in Asia and which was in no way connected by any ancestral links with the Neanderthals; a race with a brain capable of ideas, of reasoning, of imagination, and more highly endowed with artistic sense and ability than any uncivilized race which has ever been discovered. No trace of artistic instinct whatever has been found among the Neanderthals; we have seen developing among them only a sense of symmetry and proportion in the fashioning of their implements. After prolonged study of the works of the Crô-Magnons one cannot avoid the conclusions that their capacity was nearly if not quite as high as our own; that they were capable of advanced education; that they had a strongly developed æsthetic as well as a religious sense; that their society was quite highly differentiated along the lines of talent for work of different kinds. One derives this impression especially from the conditions surrounding the development of their art, which are still mysterious and an interpretation of which we shall attempt to give in the following chapter. CULTURAL, RACIAL, AND CLIMATIC DIVISIONS The Upper Palæolithic covers the greater part of the 'Reindeer Epoch' as it was conceived by Lartet and Christy, who began their systematic study and exploration of the caves of Dordogne in 1863. They were soon joined by Massénat and the Marquis de Vibraye, while Dupont took up the work in Belgium and Piette made the artistic development, especially in the Pyrenees, his chosen field. Lartet was the first to perceive that the culture of the grotto of Aurignac was quite distinct from that of the Lower Palæolithic in northern France; he also recognized in the shelter of Laugerie Haute, in Dordogne, that there was still another culture, which is now known as the Solutrean; also that in the shelter of Laugerie Basse, in Dordogne, there was yet another industry, that which we now know as Magdalenian. M. de Mortillet was the first to recognize the superiority of the Solutrean industry in stone, which in this period reached its height, and its succession by the Magdalenian period, in which the industry in bone and horn reached a climax; but he failed to recognize the very important preceding position of the Aurignacian, and it was not until 1906 that the clear presentation by Breuil of the entire distinctness of the Aurignacian industry led to the adoption by the Archæological Congress at Geneva of three cultural divisions of the Upper Palæolithic. In the meantime Piette had discovered that in the Mas d'Azil there was a distinct cultural phase, the Azilian, following the Magdalenian, and thus a fourfold division of the Upper Palæolithic (Breuil,(7) Obermaier(8)) was established, as follows: