The cultural sequence of the Nanchoc valley

Preserved charcoal from excavated house remains and garden plots was suitable for radiocarbon assays, which provide a chronology for several phases of human occupation from the late Pleistocene to the middle Holocene period (c.

The early El Palto phase (c. 11,500-10,000 bp) is associated with a pattern of scheduled, possibly seasonal movements between coastal and upland locations in northern Peru, where various plants, animals, and seafood were available during all or at different times of the year. Regional and local variation in stone tools, dated around 10,000 bp, and the use of small domestic structures (Figure 21.3) and local raw lithic material suggest the economic exploitation of circumscribed local territories (primarily alluvial fans drained by small streams) and possibly semi-sedentism by Paijan settlers. Domesticated squash (Cucurbita moschata) was adopted at this time. The constriction of territory, reduced mobility, and localization of population continued and accelerated past 9,000 bp into the following Las Pircas and Tierra Blanca phases. In some areas of the valley, this pattern of resource exploitation began to change between 9,000 and 7,000 years ago when people of the Las Pircas phase began to settle more permanently on selected alluvial fans.

Las Pircas foragers began a permanent or perhaps sedentary life at higher elevations between 9,000 and 7,000 bp, with small organized settlements, burial of the dead, domestic circular houses, subtle social differences in the artefact inventory, and small garden plots near their homesteads (Figure 21.4). Unifacial stone tools, a varied ground stone technology, simple food storage, and a food economy based primarily on the exploitation of a wide variety of plants and animals dominated the technology.

During the Tierra Blanca phase (7,000-5,000 bp), settlements aggregated closer to the valley floor and its fertile soils. House styles changed (from small circular to larger, multiple-room rectangular: Figure 21.5), cotton, beans, and coca were added, and residents constructed an artificial agricultural system associated with irrigation canals and sedentism. (Corn does not appear in the local archaeological record until about 4,000 years ago.) Although exotics disappeared, the separation of public and private or domestic space was pronounced, as evidenced by dual, stone-lined, multi-tiered earthen mounds at the Cementerio de Nanchoc site in the valley (Figure 21.6). At this site, lime was produced in a controlled, presumably public ritual context for probable use with coca leaves and/or as a food supplement (Figure 21.7). The mounds were located on an alluvial fan separated from but also acces­sible by all households. For reasons not fully understood, sedentism and food

Figure 21.3 Schematic drawing of Paijan house remains dated around 10,000 bp.

production did not occur everywhere in this valley during this phase. Some groups continued practising a mobile foraging way of life well after more cultigens were introduced into the area. Between 6,000 and 5,000 bp, farmers and foragers co-existed and were co-dependent on one another.

Figure 21.4 The remains of an excavated Las Pircas house.

Figure 21.5 The foundation of a rectangular-shaped Tierra Blanca house form.

Figure 21.6 Outline of the two mounds at the Cementerio de Nanchoc site.

Figure 21.7 Coca leaves excavated from a Tierra Blanca house floor.

There is widespread evidence that the transition from foraging to food production in parts of the valley altered aspects of the material culture. For instance, there is evidence for increased utilization of food crops in association with changes in grinding stone tools, houses, and storage pits, which appear to be a direct product of food production. It is possible to equate changes in house form or design with functional changes in the subsistence regime. For instance, circular forms of the Las Pircas phase are associated with a semi-sedentary to incipient sedentary life and with a broad­spectrum economy focused on foraging and a few food crops. However, in the Tierra Blanca phase, the reverse occurs, with the rectangular house form associated primarily with plant food production and secondarily with foraging.

Though people still relied on foraging for some subsistence means during the Tierra Blanca phase, the rich resources of the seasonally dry tropical forest, combined with food crops (i.e. squash, beans, yucca, avocado, chile pepper, peanut, quinoa), allowed for a more settled way of life.¹¹ During this period, several new sociocultural traits were developed: planning and decision-making, risk management, communal land use, resource sharing between different groups, and technological innovation. And this happened during the peak aridity of the hypsithermal between 7,000 and 4,000 bp.

In summary, in some localities of the valley, the palaeoecological and archaeological analyses relate climatic and environmental change to specific stone tool industries, dietary regimes, site and house forms, food crops, and differential human responses.