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Home arrow History arrow Southeast Inka Frontiers: Boundaries and Interactions
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Population Pressure and Agriculture

The most striking aspect of these settlement trends is the growth of population in a zone with limited agricultural potential. What factors, then, guided this decision, rather than enjoying the benefits of living closer to better agricultural soils? Was it simply a change in technology from natural irrigation to the use of in-field agricultural terraces on the Plateau? Did the shift in the location of settlements reflect defensive concerns about increasing Chiriguano invasions, or was it instead part of broader shifts that occurred in the Late Intermediate period (Arkush and Stanish 2005; Stanish 1992)?

To address these questions, the potential agricultural yields of the Plateau and the Valley zones were calculated, and these estimates were compared with the total inhabited area of each zone. This comparison was based on caloric needs. The goal was not to assess the absolute population size. Instead, I wanted to compare the relative population levels of each zone in relation to their agricultural potential. This comparison had two objectives. The first was to evaluate whether socioeconomic and demographic factors like land scarcity or population pressures guided the decision to settle the Plateau in the Classic Yampara period. The second objective was to determine if the Plateau population was economically self-sufficient.

Because of environmental similarities, the agricultural indexes provided by Christine Hastorf (1993) in her study of prehispanic agriculture in the Mantaro Valley were used. Both Mantaro and Oroncota are warm Andean valleys, suitable for the production of corn, grapes, and related products. Based on ethnographic and ethnohistoric research, Hastorf argues that around six persons inhabited a household compound. Each household was in turn composed of one patio and an average of two structures (Hastorf 1993:71). Therefore, our calculations were based on an index of three persons per structure considering the similar size in the domestic structures. Using this index, the prehistoric occupation of the Oroncota region was calculated. At preserved domestic sites, we documented a minimum of seven structures per hectare, whereas in villages there was an average of twenty structures per hectare. Both the minimum and average architectural indexes were multiplied by the total occupied area in the survey region. This provided reasonable estimates to compare the total occupational density and agricultural potential of the Plateau and the Valley zones during all periods.

To convert this population estimate into an estimate of agricultural needs, Hastorf’s (1993) calorific intake of Andean people was useful. This index is based on a value of 1,530 kcal per person (Hastorf 1993:72). Based on experiments and ethnographic research, she calculated that the valley’s irrigation yield per hectare was 1,557,915 kcal/ha, whereas hillside agriculture had an index of 984,373 kcal/ha. For this analysis, the productive area in each zone (Valley and Plateau) was multiplied by its associated index. For comparative purposes, a more conservative scenario was also utilized. To account for the fact that the Plateau was nearly half as productive as the Valley floor, the Plateau’s lower agricultural potential to a 0.6 value was adjusted. Both scenarios are summarized in Table 4.3.

These calculations were very useful in assessing the agricultural potential in comparison to population densities. As expected, a substantially higher agricultural yield can be produced in the fertile Valley zone than on the Plateau. However, the calculated population for each zone could have been comfortably supported by the production of each area, either at a minimum or average population size. For the Valley, the average village population of nearly 2,800 inhabitants could have been easily sustained by its own production. The same situation is found in the Plateau. There, the cultivation could have easily supported the mean village population of 1,344 inhabitants. This is the case even with a 0.6 adjustment for productivity. Therefore, the production in each zone could have roughly doubled the needs of the likely population. Considering that the number of people for each period was probably well below our generous “average” estimated figures, it is clear that the demographic shifts in the Oroncota

Table 4.3. Agricultural potential and population size estimates in the Oroncota region

Z-1 Valley

Z-2 Pucara Plateau

Total

N. Sites

65

243

308

Occupied area Population (1)

46.3 ha

22.4 ha

68.7 ha

Minimal population (21 persons/ha)

972 persons

470 persons

1,442 persons

Average village population (60 persons/ha)

2,778 persons

1,344 persons

4,122 persons

Population requirements (in kcal) (2)

Minimum population (21 persons/ha)

542,980,935 kcal

262,694,880 kcal

805,675,815 kcal

Average village (llajta) population (60 persons/ha)

1,551,374,100 kcal

750,556,800 kcal

2,301,930,900 kcal

Agricultural potential

Valley irrigation

2,355.4 ha

2,355.4 ha

Extensive hillside agriculture

1,809.4 ha

1,809.4 ha

Agricultural land adjusted for 0.6 of productivity difference

(in comparison to the Valley zone):

Valley irrigation Extensive hillside agriculture

2,355.4 ha

1,413 ha

Optimal potential yield (kcal/ha) (3)

Valley irrigation

3,669,512,991 kcal

3,669,512,991 kcal

Extensive hillside agriculture

1,781,124,506 kcal

1,781,124,506 kcal

Agricultural land adjusted for 0.6 of productivity difference

(in comparison to the Valley zone):

Valley irrigation

3,669,512,991 kcal

3,669,512,991 kcal

Extensive hillside agriculture

1,390,919,049 kcal

1,390,919,049 kcal

Valley cannot be explained by population pressure or by shortages of cultivable land factors alone.

Let us turn now to settlement densities. Again, even with a calculation of a 0.6 productivity adjustment, the settlements in both the Plateau and the Valley had roughly similar population densities (1-1.2 persons/ha) in relation to agricultural potential (Table 4.4). This similarity is even more striking if we take into account that in addition to different site dispersion patterns between the two zones, the Plateau had more settlements than the Valley. I suggest that this may reflect prehistoric agricultural landTable 4.4. Settlement density and agricultural potential in the Oroncota region

Valley Pucara Plateau

Valley

Pucara Plateau

Agricultural land potential

2,355 ha

1,809 ha

Population (60 persons/ha, village) Agricultural land adjusted for

2778 persons

1,344 persons

0.6 productivity difference

2,355 ha

1,413 ha

Population density (persons/ha)

Around 1.2 persons/ha

Around 1 person/ha

holding preference patterns in the sub-Andean valleys. For example, the Colonial era chronicler Garcilazo de la Vega reported that the tupu, the land unit provided by the Inka to a married couple with no children, was around 2.4 acres (Rowe 1946:266). This estimate roughly equates to 1 ha, approximately the same size of productive land allocated to the Oroncota native inhabitants.

Summing up, several aspects of the regional settlement dynamics are noteworthy. First, the largest villages throughout the cultural sequence were on the Valley floor. Second, population growth there was accommodated in larger sites, rather than in more sites. Third, the Pucara Plateau had many more sites than the Valley, but these were much smaller in size. Fourth, a clearly defined clustering pattern is observed in the Plateau, indicative of the presence of some sort of political, social, or territorial units. Fifth, the groups in the Valley remained about the same over time, with a site tendency to be spaced equidistantly along the river. Sixth, the reduction in the average distance between sites over time, particularly in the Plateau, suggests the emergence of new social or economic arrangements. In addition to these changes, another important shift during the Late Yampara-Inka period was the construction of Inka facilities. Their location in relation to the broader settlement patterns is discussed below. In chapter 5, I offer a comprehensive overview of the architectural features.

 
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