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. 2016 Apr 1;2(4):e1501532.
doi: 10.1126/sciadv.1501532. eCollection 2016 Apr.

Exploration and exploitation in the macrohistory of the pre-Hispanic Pueblo Southwest

R Kyle Bocinsky  1 , Johnathan Rush  2 , Keith W Kintigh  3 , Timothy A Kohler  4
Affiliations

Exploration and exploitation in the macrohistory of the pre-Hispanic Pueblo Southwest

R Kyle Bocinsky et al. Sci Adv. .

Abstract

Cycles of demographic and organizational change are well documented in Neolithic societies, but the social and ecological processes underlying them are debated. Such periodicities are implicit in the "Pecos classification," a chronology for the pre-Hispanic U.S. Southwest introduced in Science in 1927 which is still widely used. To understand these periodicities, we analyzed 29,311 archaeological tree-ring dates from A.D. 500 to 1400 in the context of a novel high spatial resolution, annual reconstruction of the maize dry-farming niche for this same period. We argue that each of the Pecos periods initially incorporates an "exploration" phase, followed by a phase of "exploitation" of niches that are simultaneously ecological, cultural, and organizational. Exploitation phases characterized by demographic expansion and aggregation ended with climatically driven downturns in agricultural favorability, undermining important bases for social consensus. Exploration phases were times of socio-ecological niche discovery and development.

Keywords: Agriculture; Climate change; Prehispanic Pueblo Southwest; socio-ecological cycles.

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Figures

Fig. 1
Fig. 1. The rain-fed maize growing niche in the southwestern United States, A.D. 500–1400.
Each cell is colored by the percentage of years it is in the niche; darker green represents more years in the niche. Black dots mark the locations of tree-ring–dated sites in our database (n = 1002). Our study area is within the dotted rectangle encompassing all these sites. UT, Utah; AZ, Arizona; CO, Colorado; NM, New Mexico.
Fig. 2
Fig. 2. Tree-ring date distributions and the percentage of the landscape in the rain-fed MFN where and when tree-ring dates are found, A.D. 500–1400.
Pecos period divisions (dashed lines) and subperiod divisions (dotted lines) as rederived here are superimposed on all plots. All series are smoothed using a 21-year center-aligned Gaussian filter with a 5-year SD. (A) Stacked histogram of the number of cutting and noncutting dates through time. (B) Stacked histogram of the number of 30–arc sec cells with dates, shaded by the percentage of cutting dates in the cell. Red indicates cells with 100% cutting or near-cutting dates; blue indicates cells with 0% cutting or near-cutting dates. (C) The percentage in the niche of all 30–arc sec cells (solid black line), of all cells that ever contain tree-ring dates (dotted black line), and all local cells with 95% confidence intervals (CIs) (white line with colored bars). A local cell has a tree-ring date in the plotted year or any of the previous 3 years. The color of the confidence interval for each year indicates the unsmoothed mean of the percentages of dates in each cell that are cutting and near-cutting; the color ramp is as in (B). (D) The domain radius, or radius of maximal clustering, through time (see Materials and Methods). The black line connects true data points estimated annually; the red line is smoothed as above. Lower values indicate more dispersion between smaller clusters of occupied cells, whereas higher values indicate spatially larger clusters of occupied cells. The red line is missing in periods of no significant clustering.
Fig. 3
Fig. 3. Average prediction error across space and through time for each climate reconstruction, A.D. 500–1400.
In each map, lighter (lower) values indicate a higher-quality reconstruction for that place. Declines or increases in error through time (B and D) occur when particularly important tree-ring chronologies for reconstructing each climate signal become available or unavailable, respectively. (A) Water-year precipitation, averaged through time. (B) Water-year precipitation, averaged across space. (C) Growing-season GDD, averaged through time. (D) Growing-season GDD, averaged across space.
Fig. 4
Fig. 4. Monte Carlo resampling of tree-ring date distributions controlling sample-size disparities between sites (n = 1002), A.D. 500–1400.
These are based on 999 replications; each replication represents a randomly selected date (cutting or noncutting) drawn from each site in the database. Pecos period divisions (dashed lines) and subperiod divisions (dotted lines) as rederived here are superimposed on all plots. All series are smoothed using a 21-year center-aligned Gaussian filter with a 5-year SD. (A) Mean number of dates through time, ±1 SD. (B) Stacked plot of the mean number of 30–arc sec cells with dates, shaded by the percentage of cutting dates in the cell. Red indicates cells with 100% cutting or near-cutting dates; blue indicates cells with 0% cutting or near-cutting dates.
Fig. 5
Fig. 5. For each Pecos classification subperiod, the mean number of years, within a 4-year window ending in the current year, for which a cell is in the MFN.
Pecos period divisions (dashed lines) and subperiod divisions (dotted lines) as rederived here are superimposed on all plots. Points represent the mean; error bars show ±1 SD.
Fig. 6
Fig. 6
The rain-fed MFN and tree-ring dates by revised Pecos subperiod. In each panel, the green shading represents the percentage of years in that period that each 30–arc sec cell is in the MFN; darker greens reflect more years in the niche. Dots represent cells with tree-ring dates in each subperiod, shaded by the percentage of cutting dates in the cell. Red indicates cells with 100% cutting or near-cutting dates; blue indicates cells with 0% cutting or near-cutting dates. The region is as defined in Fig. 1.
Fig. 7
Fig. 7. Histogram of the distribution of tree-ring date counts across archaeological sites.
Most sites in the database only have a single tree-ring date, whereas several sites have hundreds of dates. The y axis is logarithmic.
See this image and copyright information in PMC

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References

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