The adoption and spread of food production
Although the introduction of domesticates happened relatively early in places like the Nanchoc valley in the Central Andes, aggregated household village formation based on agricultural surplus developed a few millennia afterwards.
There was an apparent lag in the widespread adoption and intensification of agriculture. We know that the ancient human occupation in the Nanchoc valley was long-lived and coincided with a shift towards more arid conditions in the climate by at least 7,000 bp. Climatic change resulting in this shift sparked this particular opportunity for sustained agriculture on a small scale in the valley, resulting in semi-sedentism to sedentism at certain alluvial fans. This new dependence on crop production did not stimulate its immediate adoption in neighbouring areas with a similar climate. Given the current database, it seems rather clear that the exploitation of plant and animal species and the shift to food production in this case study do not fit into a simple unilinear sequence.Returning to the opening theme of this study, our work in the valley attempted to examine the factors that were involved in decisions to forage or produce food. This approach allowed us to assess the relative importance of variables that contributed to the spread of food production. The expectations of our research drove us to assess the costs associated with food production, and to hypothesize a probable sequence for the transition to food production in association with early to middle Holocene settlements, as well as the later geographic expansion of farmers in the region.
Furthermore, our research built on the study of plant and animal remains in archaeological sites, and attempted to model the specific decisions that individual communities made concerning the procurement or production of specific crop foods. At the core, our interpretations assume that communities chose to either forage or farm based upon perceived greater returns.
This interpretation made use of economic concepts that are critical to understanding adaptive decision-making in the context of food production, such as the marginal value of resources, and opportunity costs (e.g. when does the value of a cultivated resource decline, and how does the amount of labour, time, and competing opportunities factor into the decision to farm at any given time?). These concepts allow for an interpretation that anticipates future (as opposed to immediate) returns, examines the varying value of foods or resources in the context of an unpredictable future, and allows for the assessment of long-term and short-term returns on different kinds of labour expenditures (e.g. hunting, gathering, gardening). These notions are critical to understanding the context of human decision-making that involved food production in the valley. We believe that the low energy requirements for early gardening in this seasonally dry forest would have made food production appear as the best option, as a small plot of irrigated land could produce a relatively high yield following a single growing season.We also hypothesize that in the centuries that followed the initial adoption and development of food production, both foragers and food producers weighed the option of procuring food from a greater distance, which apparently was the case with food producers, as evidenced by the increased presence of exotic cultigens at Tierra Blanca sites.[1216] Similarly, the Tierra Blanca food producers continued to engage in occasional foraging, which perhaps entailed travelling longer distances. This likely narrowed their foraging options to high-ranked prey, as suggested by the increased presence of deer bones in the Tierra Blanca sites.
A final critical aspect of our work focused on the expansion of food producers into new environments, such as the interiors of larger alluvial fans and especially the fertile and more expansive floodplain downvalley near the coast.
This expansion appears to have been density dependent, and reflects population growth and the limited capacity of Tierra Blanca floodplain farming to support a burgeoning population. The expansion of food producers must also have been associated with the recruitment of new fertile niches, such as the generation of large tracts of alluvium following major El Nino events. We expect that in this density-independent scenario, population expansion would have occurred after the landscapes of the alluvial fans and narrow upvalley floodplains had been significantly altered and maximized for production. There is no current evidence to indicate that the single densely populated core that once occurred in the mountainous up-valley Nanchoc area during the early to middle Holocene period ever developed again in the region. After 5,000 bp a more widely dispersed agricultural population developed. This pattern intensified after 4,000 bp, when larger monuments and agricultural villages appeared in the valley and the wider region for the first time.