Kin Groups and Descent. According to a common Andean bilateral kinship system, Aymara trace descent through both male and female ancestors within a certain number of generations, usually to the great-grandparents ( t'unu ). It is unclear when this cognatic system developed, but ethnographers (e.g., Lambert 1977) at present agree that earlier reports of a patrilineal system are the results of misinterpretations and that the pre-Hispanic kinship system rather was parallel, or dual, in its nature (Collins 1981). Kin groups were traditionally organized into an ayllu, described as a "subtribe," "one or several extended families," "extended lineages," "a unit within which certain bonds of kinship are recognized" or, according to Zuidema (1977), as "any social or political group with a boundary separating it from the outside." The ayllus and the current corresponding comunidades display strong tendencies of endogamy. A high rate of endogamy between urban migrants and members from their community of origin is reported.
Kinship Terminology. According to Lounsbury (1964), the kinship system was a rarity of the Omaha type. This is based on Ludovico Bertonio's early-seventeenth-century Vocabulary. Today there is assimilation to a Spanish bilateral system, but with vestiges of the older system.