Mr. Darwin on the primitive relations of the sexes--Primitive man monogamous or polygamous--His jealousy--Expulsion of young males--The author’s inferences as to the evolution of Primal Law--A customary rule of conduct evolved--Traces surviving in savage life--The customs of avoidance--Custom of exogamy arose in the animal stage--Brother and sister avoidance--The author’s own observation of this custom in New Caledonia--Strangeness of such a custom among houseless nomads in Australia--Rapid decay under European influences CHAPTER II SEXUAL RELATIONS OF ANIMALS Brother and sister avoidance, a partial usage among the higher mammals--Males’ attitude to females in a group dominated by a single male head--Band of exiled young males--Their relations to the sire--Examples in cattle and horses--In game-fowl--Strict localisation of animals--Exiled young males hover on the fringe of the parent group--Parricide CHAPTER III MAN VARYING FROM ANIMALS Effect of the absence of a special pairing season on nascent man--Consequent state of ceaseless war between sire and young males --Man already more than an ape--Results of his prolonged infancy and of maternal love--A young male permitted to live in the parent group--Conditions in which this novelty arose CHAPTER IV EARLIEST EVOLUTION OF LAW Truce between semi-human sire and son--Consequent distinction taken between female and female, as such--Consequent rise of habit of brother and sister avoidance--Result, son seeks female mate from without--Note by the editor CHAPTER V AVOIDANCES Results in strengthening the groups which admit several adult males--Disappearance of hostile band of exiled young males--Relations of sire and female mates of young males now within the group--Father-in-law and daughter-in-law avoidance--Rights as between two generations--Elder brother and younger brother’s wife avoidances--Note on hostile capture CHAPTER VI FROM THE GROUP TO THE TRIBE Resemblance of semi-brutal group, at this stage, to actual savage tribe--Resemblance merely superficial--In this hypothetical semi-brutal group paternal incest survives--Causes of its decline and extinction--The sire’s widows of the group--Arrival of outside suitors for them--Brothers of wives of the group--New comers barred from marital rights over their daughters--Jealousy of their wives intervenes--Value of sisters to be bartered for sisters of another group discovered--Consequent resistance to incest of group sire--Natural selection favours groups where resistance is successful--Cousinage recognised in practice--Intermarrying sets of cousins become phratries--Exceptional cases of permitted incest in chiefs and kings--No known trace of avoidance between father and daughter--Progress had rendered such law superfluous CHAPTER VII TRACES OF PERIOD OF TRANSITION AVOIDANCES