In opposition to the classical monographes which are doing of the societies they are describing static wholes where the progress comes and disturbs the harmony, the author is trying in this study to reinsert three main notions : these of time, conflict and reaction. The first one led him to rely upon history and to make a diachronic study of such a society; the second one to locate the play of confrontations and social conflicts, creators of dynamism in that society, the third one to examine the mechanisms of defence and of reorganisation opposed by the society to the pressures which assault it from outside, emanating of the society which comprise and dominate it. In the first part of this research, it could be seen the description of the traditional social organisation such as the native formulation and a first ethnological approach let appear, then such as it is really. That organisation relies part iculsrly upon three institutions: the dualist system which divides the village into two halfs, Qollana and Wanaco, theoretically residencial, endogamous end rival, which maintain complemental but inegual reports; the System of the social relationship (compaternity principally and relationship by oath) which weaves between each of its members a large network of hierarchical relations, oriented from the weak section to the strong one, but which in fact justifies the domination of the ones upon the others; the system of the social and normalized ascension where the members of each section share comptementary the politic and religious burdens, but which dedicate the ones enrichment and the others Impoverishment. In the second part, the author confronts inmediate data with the empirical relidad, by systematic and quantitative analysis of social and economic reports (land, property, production reports, politic responsabilities, bands of compaternity) and also by the rituel and the history, which do appear the existence of an unwedge between what it is said and what it is. One could realize that the dualist system represents only a precarious moment or even idealized of social stability. In front of the dualism, warranting of the order, which is affirmed by the tradition, appear the strengths of contestation which develop themselves generally under a ternary form, and come and interpose themselves between the two groups in presence. In the same time and as resuit, the social relationship are modificated. The system reorganize itself to the new data while the tradition which represents the instrument of social control, no ceases to affirm the perennity of the equalltarian structures, to struggle against the diversity of the experiences and of the social conflict and against the strengths of domination which get away from it. Finally, a third part is consacred in a theoretic way to the dynamic of change which rests upon the obligatory lack of balance existing between two social groups. In that optic, other social contexts have been considered, then other thecretic approaches, the structuralism particulary which, flattening the t i m e and doing of the dualism a simple frame to the matrimonial Institutions, strikes itself against the Impossible imbrication of Irreconciliable structures without any diachronic or politlcal perspective of what we call " tradition ". A society is not a static whole. In a perpetual struggle between order and contestation, old and new patterns coexist, found, oppose and develop them without either sociologists or politic men could be able t o well-shape the societies which are doing t h em in the moulding they have thought for them."