The bulk of the contemporary populations in the study area reside in towns in block 3 established during the colonial period that are distributed along the Colca river. The largest settlement inside the study area is Callalli, a town with a 1993 population of 1295 persons, and across the Colca River the population of the town of Sibayo is 508, and upstream in Block 5 the cooperative of Pulpera numbers 85 residents (I.N.E.I. 1993). These towns are primarily service centers and district seats for widely distributed populations with an economy based largely on pastoral products, and on extensive interaction through trade with their wealth in camelid herds, and have long resided in rural hamlets and herding outposts. Callalli and Sibayo first formed as part of the sixteenth century reducción of the Yanque Collagua, and in the colonial period the province of Collaguas (Caylloma) held three-quarters of the livestock in all of Arequipa (Cook 1982;Manrique 1985: 95-96). The dominance of the herding economy in these upper valley towns is evident in the 1961 census where both Callalli and Sibayo populations are reported as 93% "rural", while the average percentage for all nineteen towns in the Colca census, including large and dense agricultural communities downstream, was only 52% "rural" (Cook 1982: 44).

These early villages also formed an important source of labor for colonial mining ventures in the Cailloma region (Guillet 1992: 25-27). Mercury and copper were mined between Callalli and Tisco (Echeverría 1952 [1804]) and Lechtman (1976) reports a structure in Callalli known as " La Fundición" that is described as "stone metal smelter, probably colonial, said to be for copper smelting: mineral, scoria on surface". A location known as "Ccena" or "Qqena" is described as having "metal smelters near a pre-Spanish occupation site: mineral, scoria, surface sherds" (Lechtman 1976: 11). The toponym "Ccena" can be found close to the Llapa and Pulpera stream confluence upstream of Callalli. These historical smelters were not encountered during the course of our survey in this particular area.