The indirect evidence of a former stage of unrestricted sexual relations, based on the existence of certain customs assumed to be its survival, particularly female kinship, exogamy, and polyandry, turns out on examination to be even less convincing than that obtained from direct observation. Primitive man is usually influenced by extremely simple motives; and the great fault of speculation has been the assignment of remote and complex causes for phenomena which are often capable of easier explanation. "The most important features of the life of a community," Starcke observes, "are due to forces at once simple and universal."[333] [333] _Primitive Family_, 9; _ibid._, 30. STARCKE is conspicuous for the simple causes which he assigns for the various phenomena connected with marriage and the family. See examples, _op. cit._, 43, 49, 50, 106. II. THE PROBLEM OF MOTHER-RIGHT Such is the case with attempts to account for kinship in the female line. McLennan thinks it "inconceivable" that it can be due to any cause other than uncertainty of fatherhood; and he holds therefore that it must have preceded the paternal system.[334] Careful research, however, has shown that these assumptions are far from axiomatic. In the first place, the acute criticism of Friedrichs is deserving of special attention. Among a number of low races where relationship with the begetter is not recognized he finds that certainty of fatherhood through securing the fidelity of the wife nevertheless exists. The number is small, but a single certain example, he insists, is sufficient to refute McLennan's hypothesis. Such an example is provided by Semper[335] in the case of the people of the Palau Islands; and it is all the more convincing because here it is only the wife who is prohibited from general sexual intercourse, while young girls may give free play to their desires, and in a measure this is not merely suffered, but even enjoined by social custom.[336] Indeed, savages know well how to secure chastity on the part of their women by such "naïve arts" as infibulation, so realistically described by Ploss in his well-known book on woman.[337]