Public architecture, community organization, and food production
Communal construction projects are noted for the Nanchoc valley during the middle Holocene period. These include agricultural earthworks (i.e. canals and fields) and possible ceremonial mounds that are associated with the rise of crop production.
Mound-building was restricted to the small teardrop-shaped structures at the site of Cementerio de Nanchoc.13 The moundsites represent one of the earliest public architectural expressions in the Central Andes and, of particular relevance, can be situated within the local settlement system. The mounds produced evidence of lime production, which is believed to have been associated with the consumption of coca leaves. The archaeological record of both Las Pircas and Tierra Blanca households shows evidence for heating calcium-bearing limestone to produce lime as an alkali, used in historic times and today to extract alkaloids from coca leaves. Coca leaves (E. novogranatense var. truxillense) and precipitated lime were preserved in the floors of several houses. Two radiocarbon dates on the leaves indicate that coca chewing in the valley began at least 147,000 years ago.
The horticultural landscape of the Las Pircas phase is characterized by the presence of short feeder ditches taking water from the upper reaches of small streams at the headwaters of alluvial fans, which flowed into small garden plots adjacent to fifteen to twenty houses. A more intensified and communal organization of agriculture in the valley occurred during the subsequent Tierra Blanca phase. This phase is defined by the presence of more than twenty-five households that correspond to small communities linearly aggregated downslope on the alluvial fans near a 2.5 km long irrigation canal that watered the fertile floodplain of the river valley. That is, a major settlement transformation took place from one phase to the other, with the Tierra Blanca people shifting from small stream-irrigated horticulture on alluvial fans to canal-irrigated floodplain agriculture.
At the smallest scale, these changing domestic and communal food production landscapes of the valley were linked exclusively to local sociopolitical conditions, rather than to a larger valley-long polity or centralized authority. At the largest scale, the organization of agriculture by local communities is reflected in a ‘legible' landscape,[1214] [1215] one that eventually became familiar to non-local communities that adopted similar food production practices in similar alluvial and riverbottom landscapes. At a small or large scale, these landscapes are records of alternative ways to communally create, transform, and manage resources, and of different concepts of the relationship between nature and culture.In summarizing the interdisciplinary data from the Nanchoc valley, smallscale changes combining short-distance environmental moves, development of irrigation and crop technologies, and continued reliance on some hunting and gathering, in a specific mixed environmental setting among various households of small, dispersed, and aggregated communities, made significant socioeconomic advances and held a magnetic potential for causing change elsewhere in the region. Interdisciplinary research on the specific and small-scale environmental setting of the Nanchoc valley allowed us to pinpoint specific human and palaeoecological parameters as people not only adjusted to local climate changes over a long period of time but also transformed their social and economic practices to benefit from them. The collective evidence shows that similar developments were not taking place in neighbouring areas as far away as 2-5 km within the same valley, where similar suitable climatic and environmental conditions existed. Although spatially extensive foraging sites of hunters and gatherers characterized other alluvial fans during this same period, neighbouring groups made decisions to stay primarily with a foraging life. Although we cannot point directly to climate changes as spurring these social and cultural changes, there must have been choices and preferences by local communities in responding to them, with some groups deciding to change, others possibly deciding to move elsewhere, and others maintaining a status quo.