Other writers—and among them Mr. Morgan—have suggested that prohibitions of the marriage of near kin have arisen from observation of the injurious results of such unions.[1895] But most investigators who have considered the subject believe that this knowledge could be gained only by lengthened observation, and, to quote Dr. Peschel, is “unattainable by unsettled and childishly heedless races,” among whom, nevertheless, a horror of incest is developed most strongly.[1896] Sir Henry Maine, on the other hand, thinks that the men who discovered the use of fire and selected the wild forms of certain animals for domestication and of vegetables for cultivation, might also have been able to find out that children of unsound constitution were born of nearly related parents.[1897] In the next chapter, I shall have occasion to mention some instances which possibly may point in this direction, but in no case does such knowledge appear to be generally diffused among backward races. Mr. Curr has been unable to discover on what ground consanguineous marriages are held to be objectionable by the Australians, their replies to questions on this head invariably being, “Our tribe always did as we do in this matter.” Yet they are well aware, he says, that the aim of the exogamous restrictions is to prevent the union of nearly related individuals.[1898] Dr. Sims writes that no other reason for the avoidance of marriage between near relations has been stated to him by the indigenous Bateke than that of “shame.” Mr. Bridges informs me that the Yahgans point simply to the fact of relationship as the reason; and, when Azara asked the Charruas why a brother and sister never intermarried, they replied that they did not know why.[1899] It is conceivable that the experience of the injurious results of such marriages, once acquired, might afterwards have fallen into oblivion, although the prohibition continued to exist. But Azara expressly states that the Charruas have no law forbidding incestuous alliances, yet he has never seen nor heard of any among them.