The researches of several recent writers, notably those of Starcke and Westermarck, confirming in part and further developing the earlier conclusions of Darwin and Spencer, have established a probability that marriage or pairing between one man and one woman, though the union be often transitory and the rule frequently violated, is the typical form of sexual union from the infancy of the human race. The problem is not yet fully worked out; but if in the end the theory of original promiscuity must be abandoned, and the pairing or monogamous family accepted as the primitive social unit, it is not because of the spiritual and moral superiority of man, as compared with other animals, but because sexual communism as a primitive and general phase of life appears to be inconsistent with the biological, economic, and psychological laws which have determined the general course of organic evolution. Strongly supported and highly probable as is the pairing or monogamic theory, it must be clearly understood in the outset that it is still only a theory and has not yet reached the stage of demonstration. It will hardly do, however, to set aside the researches of its adherents as being superficial and devoid of real scientific method; for the champions of the opposite doctrine of primitive communism are nothing if not daring, and their sweeping generalizations often rest solely on comparatively few "survivals" of alleged conditions which are absolutely "prehistoric."[266] [266] Among the great living investigators in this field no one, perhaps, has sinned more frequently in making hazardous generalizations than KOHLER, who is particularly harsh in his criticism of Westermarck, Curr, and other adversaries. See, for example, his _Zur Urgeschichte der Ehe_, 2 ff., 150 ff.