From the preceding analysis it will appear, we trust, that scientific examination of the problems of kinship and exogamy has disclosed something of the real origin of the laws which govern human sexual relations. The searching criticism to which the theory of polyandry has been subjected, in connection with the opposite custom of polygyny, carries us still nearer the truth. For, in the light of recent research, it does not seem entirely hopeless to discover a trace of the actual sequence in which, according to natural law, the general forms of marriage and the family have been evolved. According to McLennan, it will be remembered, polyandry originates in a scarcity of women due to female infanticide; and it is a universal phase of social progress through which transition is made from promiscuity and the system of kinship in the female line to the paternal system and higher types of family life. Furthermore, he seems to think, though on this point he is not very clear,[399] that polygyny may grow out of polyandry through the practice of capturing wives. This theory has by no means gone unchallenged.[400] It has been shown, in the first place, that the extent to which the custom of polyandry has prevailed is greatly exaggerated. Though it is found among various peoples in different parts of the world, its occurrence is on the whole comparatively rare; and the practice is much less extended than that of polygyny. Its former existence cannot be inferred from such customs as the niyoga and the levirate; for these are capable of simpler explanation.[401] It is highly probable, as Starcke urges, that they are merely expedients for procuring an heir or for conveniently regulating the succession to property and authority,[402] particularly in the joint family; but there is no good reason to doubt that Spencer's explanation is adequate in some cases. "Under early social systems," he declares, "wives, being regarded as property," are inherited like other possessions.[403] The procuring of an heir through a brother or some other third person harmonizes with the "juridical character of fatherhood among primitive men."[404] [399] MCLENNAN, _Studies_, I, 116, _passim_; _cf._ SPENCER, _Principles of Sociology_, I, 679. [400] See, especially, WESTERMARCK, _op. cit._, chaps. xx-xxiii; STARCKE, _Primitive Family_, 128-70; WAKE, _Marriage and Kinship_, chaps. v, vi, vii; and compare HELLWALD, _Die mensch. Familie_, 241 ff. For the literature of polyandry, see p. 80, n. 2, above. [401] For the literature relating to the levirate and similar customs, see above p. 84, n. 2. [402] This may be the explanation of the levirate among the Todas: MARSHALL, _A Phrenologist amongst the Todas_, 206-9, 213. Similar practical motives influenced the rise of the levirate elsewhere: DORSEY, "Omaha Sociology," _III. Rep. of Bureau of Eth._, 258; _cf._ MARTIUS, _Ethnographie_, 117, notes; _idem_, _Rechtszustande_, 64.