Since, as a matter of fact, cultural resemblances abound between peoples of diverse stock, their interpretation commonly narrows to a choice between two alternatives. Either they are due to like causes, whether these can be determined or not; or they are the result of borrowing. A predilection for one or the other explanation has lain at the bottom of much ethnological discussion in the past; and at present influential schools both in England and in continental Europe clamorously insist that all cultural parallels are due to diffusion from a single center. It is inevitable to envisage this moot-problem at the start, since uncompromising championship of either alternative has far-reaching practical consequences. For if every parallel is due to borrowing, then sociological laws, which can be inferred only from independently developing likenesses, are barred. Then the history of religion or social life or technology consists exclusively in a statement of the place of origin of beliefs, customs and implements, and a recital of their travels to different parts of the globe. On the other hand, if borrowing covers only part of the observed parallels, an explanation from like causes becomes at least the ideal goal in an investigation of the remainder.[20] An illustration will exhibit the manner in which problems originally historical become psychological and sociological. Tyler in his _Early History of Mankind_ has pointed out that the bellows used by the negro blacksmiths of continental Africa are of a quite different type from those used by natives of Madagascar. The bellows used by the Madagascar blacksmiths, on the other hand, are exactly like those in use by the Malays of Sumatra and in other parts of the Malay Archipelago. This indication that the natives of Madagascar are of Malay origin is in accordance with other anthropological and ethnological data in regard to these peoples, which prove the fact, now well established, that they are not of African origin. Similarly Boas' study of the Raven cycle of American Indian mythology indicated that these stories originated in the northern part of British Columbia and traveled southward along the coast. One of the evidences of the direction of this progress is the gradual diminution of complexity in the stories as they traveled into regions farther removed from the point of origin. All this, in so far as it seeks to determine the point of origin, direction, speed, and character of changes that take place in cultural materials in the process of diffusion, is clearly history and ethnology.