All over the world may be found traces of a Stone Age, ancient or modern, primitive implements of stone and flint analogous to those of the true Chellean period of western Europe but not really identical when very closely compared. These represent the early attempts of the human hand, directed by the primitive mind, to fashion hard materials into forms adapted to the purposes of war, the chase, and domestic life. The result is a series of parallels in form which come under the evolution principle of convergence. Thus, in all the continents except Australia--in Europe, in Asia, and even in North and South America--primitive races have passed through an industrial stage similar to the typical Chellean of western Europe. This we should rather attribute to a similarity in human invention and in human needs than to the theory that the Chellean industry originated at some particular centre and travelled in a slowly enlarging wave over the entire world. [Illustration: FIG. 73. Distribution of the principal Pre-Chellean and Chellean industrial stations in western Europe.] In western Europe the Chellean culture certainly had a development all its own, adapted to a race of bold hunters who lived in the open and whose entire industry developed around the products of the chase. For them flint and quartzite took the place of bronze, iron, or steel. This culture marked a distinct and probably a very long epoch of time in which inventions and multiplications of form were gradually spread from tribe to tribe, exactly as modern inventions, usually originating at a single point and often in the mind of one ingenious individual, gradually spread over the world. [Illustration: FIG. 74. Section of the middle and high terraces at St. Acheul, from southwest to northeast. After Commont, 1908, 1909, modified and redrawn. The Pre-Chellean workers first established themselves here at the time when the Somme was visited by the straight-tusked elephant and other primitive mammals of the warm African-Asiatic fauna. (Compare Fig. 59, p. 122.)]