_Trade, or Exchange of Goods_.--In Mr. Clark Wissler's book on _Man and Culture_, he has shown quite conclusively that there are certain culture areas whereby certain inventions, discoveries, or customs have originated and spread over a given territory. This recognition of a centre of origin of custom or invention is in accordance with the whole process of social development. For instance, in a given area occupied by modern civilized people, there are a very few who invent or originate things, and others follow through imitation or suggestion. So it was with the discoveries and inventions of primitive man. For example, we know that in Oklahoma and Arkansas, as well as in other places in the United States, certain stone quarries or mines are found that produce a certain kind of flint or chert used in making arrow-heads or spearheads and axes. Tribes that developed these traded with other tribes that did not have them, so that from these centres implements were scattered all over the West. A person may pick up on a single village site or battle-ground different implements coming from a dozen or more different quarries or centres and made by different tribes hundreds of miles apart in residence. This diffusion of knowledge and things of material {105} workmanship, or of methods of life, is through a system of borrowing, trading, or swapping--or perhaps sometimes through conquest and robbery; but as soon as an article of any kind could be made which could be subjected to general use of different tribes in different localities, it began to travel from a centre and to be used over a wide area. Certain tribes became special workers in specialized lines. Thus some were bead-makers, others expert tanners of hides, others makers of bows and arrows of peculiar quality, and others makers of stone implements. The incidental swapping of goods by tribes finally led to a systematic method of a travelling trader who brought goods from one tribe to another, exchanging as he went. This early trade had an effect in more rapid extension of culture, because in that case one tribe could have the invention, discovery, and art of all tribes. In connection with this is to be noted the slow change of custom regarding religious belief and ceremony or tribal consciousness. The pride of family and race development, the assumption of superiority leading to race aversion, interfered with intelligence and the spread of ideas and customs; but most economic processes that were not bound up with religious ceremonies or tribal customs were easily exchanged and readily accepted between the tribes.