Agro-Pastoralism and Social Change in the Cuzco Heartland of Peru: A Brief History Using Environmental Proxies

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The purpose of this paper is to sketch a history of agro-pastoralism during the last 4200 years in the heartland of the Cuzco region, thus providing a context for social and political changes leading up to the Inca period and beyond. While such changes are not solely driven by environmental trends, environmental factors can provide restraints, challenges and opportunities that influence agricultural and pastoral activities, population density, altitudinal/latitudinal migration, and affect the spread of diseases. Certainly, social and technological developments can have a major impact on agro-pastoral output, and the more food that is made available by efficient production, storage and distribution, the larger the proportion of the population available to carry out other tasks, such as creating road networks and maintaining a large, standing army. Efficient agro-pastoralism was certainly one of the factors that led to the success of the Inca Empire. Additional drivers, such as climate, also probably had a major role to play (Chepstow-Lusty et al. 2009).


Our research focused on Laguna Marcacocha which lies at 3350m above sea level, surrounded by agricultural terraces in a highly anthropogenic, ancient landscape (Figures 1 & 2). The deep and circular lake (or pond) was only 35m in diameter (today it is an infilled wetland) and filled by underground discharge from the Patacancha River (which flows even during the dry season due to meltwater supply). The site is adjacent to an ancient trading route for llama caravans that still connects the selva and the sierra, with the major Inca settlement of Ollantaytambo (2792m asl) located 12km downstream (Figure 3). The pasture adjacent to Marcacocha would have been an important resource for these llama caravans, as it is today for cattle, horses and sheep (Figure 4).

The pollen sequence from Marcacocha provided a high resolution (c. 40-100 year interval) environmental and agricultural history of the last 4200 years (Chepstow-Lusty et al. 1996, 1998, 2003), represented by 6.3m of well-dated, highly organic sediments. In the present study, the pollen record was combined with quantitative measures of oribatid mites (Figure 5) at a sampling resolution every 10mm (c. 5-10 years). An abundance of oribatid mites is seen as an indication of high concentrations of camelid dung and thus greater food availability for these detritivores. This in turn acts as a proxy for the intensity of pastoralism at Marcacocha, and potentially the frequency of llama caravans along the adjacent route using the pasture (Chepstow-Lusty et al. 2007).


The oribatid mite as a proxy

There are two useful controls that justify this equation. First, is the high abundance of oribatid mites recorded during the brief bur rapid expansion of the Inca Empire that occurred between c. AD 1400 and 1532, which then collapsed with the arrival of the Spanish conquistadors. This abundance could be due to the large caravans of llamas numbering 1000 animals or more recorded by Spanish chroniclers, bringing goods between the selva and sierra on highways such as that which passed Marcacocha, and using the pasture en route to major sites, including Ollantaytambo (e.g. de Garcilaso de la Vega 1609 [1966]; de Acosta 1590 [1986]). The subsequent marked decline of oribatid mites in the record could reflect a rapid decline in pastoralism, the disappearance of llama caravans on this trading route, or the decimation of the indigenous people that looked after the animals following the introduction of new diseases.

A second control is provided by the increase in oribatid mites from the 1600s onwards, as the Patacancha Valley fell under the control of an important hacienda and Old World livestock, such as cattle, horses and sheep began to make use of the high-quality pasture around Marcacocha. …