"In several of the ingenious theories relating to the development and origin of American cultures in general, it has been contended that considerable migrations both of peoples and of cultural elements passed along this coastal highway from north to south. If, however, the archaeological evidence is to be depended on, such great sweeping movements, involving many elements of foreign culture, could hardly have taken place, for no trace of their passage or modifying effect is apparent.... We can feel fairly sure that the prehistoric peoples of each area were in the main the direct ancestors of the local tribes of today.... "In comparison with the relative simplicity of the archaeological record on the Pacific coast, that of the eastern portion of the continent is complex, and might indeed be best described as a palimpsest. This complexity leads inevitably to the conclusion that here there have been numerous and far-reaching ethnic movements, resulting in a stratification of cultures." W. H. Holmes has compiled a map marking the limits of eleven areas which can be recognised by their archaeological remains[804]. He points out that the culture units are, as a matter of course, not usually well-defined. Cultures are bound to over-lap and blend along the borders and more especially along lines of ready communication. In some cases evidence has been reported of early cultures radically distinct from the type adopted as characteristic of the areas, and ancestral forms grading into the later and into the historic forms are thought to have been recognised. Holmes frankly acknowledges the tentative character of the scheme, which forms part of a synthesis that he is preparing of the antiquities of the whole American continent.