Who provided maize to Chaco Canyon after the mid-12th-century drought?

Between A.D. 1181 and 1200, in the early part of a climatically wet period, corn was imported to Chaco Canyon from a region outside the Chaco Halo (defined in this paper as the region between the base of the Chuska Mountains and Raton Wells). Strontium-isotope (⁸⁷Sr/⁸⁶Sr) analyses of 12 corn cobs dating to this period match ⁸⁷Sr/⁸⁶Sr ratios from five potential source areas, including: the Zuni region, the Mesa Verde-McElmo Dome area, the Totah, the Defiance Plateau, and Lobo Mesa. The latter two areas were eliminated from consideration as possible sources of corn in that they appear to have been unpopulated during the time period of interest. Therefore, it appears that the corn cobs were imported from the Zuni region, the Mesa Verde-McElmo Dome area, or the Totah area during a time when the climate was relatively wet and when a surplus of corn was produced in regions outside Chaco Canyon. Based on proximity to and cultural affiliation with Chaco Canyon, it is hypothesized that the corn probably was imported from the Totah.     

Possible sources of archaeological maize found in Chaco Canyon and Aztec Ruin,New Mexico

Maize played a major role in Chaco's interaction with outlying communities in the southern Colorado Plateau. This paper seeks to determine where archaeological corn cobs brought to Chaco Canyon were grown. Strontium-isotope and trace-metal ratios of 180 soil-water and 18 surface-water sites in the Southern Colorado Plateau have revealed possible source areas for some of 37 archaeological corn cobs from Chaco Canyon and 10 archaeological corn cobs from Aztec Ruin, New Mexico. The most probable source areas for cobs that predate the middle-12th-century drought include several Upper Rio Chaco sites (not including Chaco Canyon). There are many potential source areas for cobs that date to the late A.D. 1100s and early 1200s, all of which lie in the eastern part of the study area. Some Athapascan-age cobs have potential source areas in the Totah, Lobo Mesa, and Dinetah regions. One Gallo Cliff Dwelling cob has a strontium-isotope ratio that exceeds all measured soil-water values. Field sites for this cob may exist in association with Paleozoic and Precambrian rocks found 80–90 km from Chaco Canyon. Potential source areas for most Aztec Ruin cobs (many of which were found in rooms dating to the first half of the 13th-century) appear to be associated with a loess deposit that blankets the Mesa Verde and McElmo Dome regions.     

Some thoughts on the factors that controlled prehistoric maize production in the American Southwest with application to southwestern Colorado

In this paper, we present a model of prehistoric southwestern Colorado maize productivity. The model is based on a tree-ring reconstruction of water-year precipitation for Mesa Verde for the period A.D. 480 to 2011. Correlation of historic Mesa Verde precipitation with historic precipitation at 11 other weather stations enabled the construction of an elevation-dependent precipitation function. Prehistoric water-year precipitation values for Mesa Verde together with the elevation-dependent precipitation function allowed construction of the elevation of southwest Colorado precipitation contours for each year since A.D. 480, including the 30-cm contour, which represents the minimum amount of precipitation necessary for the production of maize and the 50-cm contour, which represents the optimum amount of precipitation necessary for the production of maize. In this paper, calculations of prehistoric maize productivity and field life for any specific elevation are also demonstrated. These calculations were performed using organic nitrogen measurements made on seven southwestern Colorado soil groups together with values of reconstructed water-year precipitation and estimations of the organic nitrogen mineralization rate.     

Seismic Refraction at Ancestral Puebloan Sites on the Pajarito Plateau,New Mexico

Abstract

Geophysical techniques can be used for non-invasive surveys at archaeological sites. One under-utilized technique, seismic refraction, has many potential applications. It is an inexpensive, efficient way to characterize subsurface deposits, especially at sites with shallow accumulations over bedrock. Archaeologists and geophysicists participating in the Summer of Applied Geophysics Experience from Los Alamos National Laboratory and Bandelier National Monument on the Pajarito Plateau in northern New Mexico characterized Ancestral Puebloan sites (A.D. 1200–1450) using this technique. We provide an overview of how seismic refraction works and demonstrate the applicability of seismic refraction for identifying buried archaeological features such as communal structures and walls.     

Development and application of methods used to source prehistoric Southwestern maize: a review

Archaeological cobs free of mineral contaminants should be used to source the soils in which they were grown. Mineral contaminants often contain much higher concentrations of metals than vegetal materials and can alter a cob’s apparent metal and heavy-isotope content. Cleaning a cob via immersion in an acid solution for more than a few minutes will result in the incongruent and sometimes complete leaching of metals, including strontium (Sr), from the cob. When using ⁸⁷Sr/⁸⁶Sr to determine the location of potential agriculture fields, it is best to either integrate several depth-integrated soil samples or to integrate several vegetation samples from individual fields. Biologically labile Sr in semi-arid Southwestern soils largely originates from eolian source or sources and usually is not derived from underlying bedrock. Existing Sr-isotope data indicate that archaeological cobs from Aztec Ruins came from either the Mesa Verde-McElmo Dome or Totah areas, that Pueblo Bonito and Chetro Ketl cobs, from Chaco Canyon that predate A.D. 1130, probably came from the Rio Chaco corridor, and that cobs from Chaco Canyon, that postdate A.D. 1130, probably came from either the Totah or Zuni areas.     

Factors Controlling Pre-Columbian and Early Historic Maize Productivity in the American Southwest,Part 1: The Southern Colorado Plateau and Rio Grande Regions

Maize is the New World’s preeminent grain crop and it provided the economic basis for human culture in many regions within the Americas. To flourish, maize needs water, sunlight (heat), and nutrients (e.g., nitrogen). In this paper, climate and soil chemistry data are used to evaluate the potential for dryland (rain-on-field) agriculture in the semiarid southeastern Colorado Plateau and Rio Grande regions. Processes that impact maize agriculture such as nitrogen mineralization, infiltration of precipitation, bare soil evaporation, and transpiration are discussed and evaluated. Most of the study area, excepting high-elevation regions, receives sufficient solar radiation to grow maize. The salinities of subsurface soils in the central San Juan Basin are very high and their nitrogen concentrations are very low. In addition, soils of the central San Juan Basin are characterized by pH values that exceed 8.0, which limit the availability of both nitrogen and phosphorous. In general, the San Juan Basin, including Chaco Canyon, is the least promising part of the study area in terms of dryland farming. Calculations of field life, using values of organic nitrogen for the upper 50 cm of soil in the study area, indicate that most of the study area could not support a 10-bushel/acre crop of maize. The concepts, methods, and calculations used to quantify maize productivity in this study are applicable to maize cultivation in other environmental settings across the Americas.     

Modeling agricultural potential in Chaco Canyon during the Bonito phase: a predictive geospatial approach

This study presents a geospatial analysis of surficial hydrology and geomorphology and their relationship to potential agricultural productivity in order to better understand the economic role of water in Chaco Canyon during the Bonito Phase (ca. AD 850–1150). Defined as the Natural Agricultural Suitability Analysis, the foundation of this study is a hierarchical geospatial analysis that integrates six key natural factors: slope, soil texture, soil depth, non-catastrophic overbank flooding potential, drainage flow length, and drainage proximity and flow potential. These factors are combined through a raster weighted overlay function to generate composite suitability map that offers a testable proxy for variability in relative agricultural potential during the Bonito Phase at Chaco. The rationale for including this set of natural factors is based largely on ethnographic and modern agricultural studies, but the predictive model differs from previous studies of agricultural potential in that it is independent of the specific archaeological distribution of evidence of agriculture in the study area. The results of this analysis suggest that previous models of Chacoan agricultural productivity have underestimated local production capacity. Previous studies have focused solely on floodplain contexts, whereas this study points to a more comprehensive and geographically distributed use of the landscape.     

Agriculture and community in Chaco Canyon: Revisiting Pueblo Alto

The Bonito Phase (ca. AD 860–1140) in Chaco Canyon is widely recognized as one of the primary sources of information about emergent social complexity in prehispanic North America. Large masonry buildings called “great houses,” such as Pueblo Bonito, are iconic symbols of the rapid rise of a powerful society based on the ability to harness labor to prolonged construction projects. It is clear that the political forces at work during the Bonito Phase had an agricultural foundation, presumably in the financing of construction through food surpluses, but the actual nature of farming in Chaco is surprisingly opaque to archaeologists. Indeed, many researchers have concluded that farming in Chaco Canyon was too constrained by poor soils to have supported the dynamic developments associated with the massive stone structures and extensive trade systems of the Bonito Phase. The popular perspective that Chaco was mysterious or enigmatic is largely a response to this view of the canyon as agriculturally marginal. In this study we argue that a predictive model of potential agricultural productivity that includes other portions of the canyon besides the floodplain indicates that Chaco was not marginal for farming. The results of this analysis suggest that great house communities may have been sited to control local production zones and that some great houses may have been linked to others in order to manage multiple agricultural areas.     

Chronology and Cultural Activity in Johnson Canyon Cliff Dwellings: Interpretations from Tree-Ring Data

Abstract

Archaeological tree-ring samples were collected during the summer of 1974 from nine cliff dwellings in the tributaries of Johnson Canyon on the Ute Mountain Indian Reservation in SW Colorado. The cliff dwellings belong to the Mesa Verde branch of the Anasazi cultural tradition and on the basis of ceramics and architecture could be assigned to the McElmo phase (1050-1150 A.C.) and the Mesa Verde phase (1150-1300 A.C.). Of a total of 461 tree-ring samples, 352 could be dated. These dates and other observations made during the analysis are applied toward refinement of the dating of the sites as well as to interpretations about utilization of timber resources, environment, and demography. Two clusters of cutting dates consistently occur in most of the sites indicating two periods of construction activity, one in the middle 1100s and the other in the early 1200s. The existing architecture at these sites dates to the early 1200s while the earlier structures have apparently been dismantled and their materials reused. These data suggest an occupation of the area beginning in the 1140s, followed by an abandonment by the 1160s. The area was reoccupied in the early 1200s for only 30 to 40 years before final abandonment.     

Stone-boiling maize with limestone: experimental results and implications for nutrition among SE Utah preceramic groups

Groups living on Cedar Mesa, SE Utah in the late Basketmaker II period (Grand Gulch phase, AD 200–400) were heavily maize-dependent, but lacked beans as a supplemental plant protein, and pottery vessels for cooking. Common occurrence of limestone fragments in their household middens suggests 1) limestone may have been used as the heating element for stone-boiling maize and 2) this practice might have made some maize proteins more available for human nutrition. Experiments examined these possibilities; results indicate that stone-boiling with Cedar Mesa limestone creates an alkaline cooking environment suitable for nixtamalization of maize kernels, and that maize cooked in this fashion shows significant increases in availability of lysine, tryptophan, and methionine. Archaeological limestone fragments from a Grand Gulch phase site show amounts of fragmentation and changes in density consistent with repeated heating. While not conclusive, these data indicate that further research (e.g., examination of archaeological limestone fragments for maize starch grains or phytoliths) is warranted. It is suggested that greater attention be paid to archaeological indications of stone-boiling with limestone among maize-dependent but pre-pottery societies.     

Tewa Place Names for Early Habitation Sites in the Northern Rio Grande Valley,New Mexico

Place names have the potential to aid in the investigation of regional settlement histories because they reflect the importance of specific locations in the social or cultural memories of indigenous groups. Unique place names for ancient habitation sites such as villages or hamlets, i.e., those names for which there are no cognates in other languages, suggest that those ancient villages or hamlets still retain the names given to them by their original inhabitants. Here, we present Tewa place names for habitation sites identified archaeologically in the northern Rio Grande Valley of New Mexico. The results of our study strongly suggest that the Tewa language was spoken in the northern Rio Grande Valley, specifically, within the southern Tewa Basin, as early as the Late Developmental period (a.d. 900–1200), thus challenging the currently well-accepted model postulating a Mesa Verde origin for the Tewa language and culture.     

The stable and radio-isotope chemistry of southeastern Utah Basketmaker II burials: dietary analysis using the linear mixing model SISUS,age and sex patterning,geolocation and temporal patterning

The Bayesian linear mixing model SISUS is used to reconstruct reliance on maize and intake of animal protein from the stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values of 149 directly dated Basketmaker II burials. Maize is the primary dietary staple. δ¹³C values are also enriched by intake of yucca and wild C₄ plant foods but these resources are of minor importance in sampled diets. Animal protein intake is low and cottontail rabbits make the greatest contribution to female diets. Adolescent diets are indistinguishable from the diets of adult females and both groups are less reliant on artiodactyls than males. The δ¹³C and δ¹⁸O values of bone hydroxyapatite distinguish nursing infants and oxygen isotope values identify outsider adults relative to those local to the region where their deaths occurred. Most Utah Basketmaker II burials are contemporary with Black Mesa Lolomai phase occupations, postdating the Marsh Pass, AZ, White Dog phase. All burials in both studies were recovered from sheltered rather than open sites and reliance on maize does not increase over the temporal span of the Utah study, covering the two sigma range 415 BC–AD 322.     

Working holiday makers in Australia: food security,climate change,and the backpacker tax

This commentary considers an often overlooked contribution to food security in Australia—the labour of working holiday makers. Their ability to act as a flexible and mobile temporary workforce is essential to the maintenance of the Australian agricultural industry. Previously, no tax was payable on income below $18,200, but a 2015 proposal to increase their tax rate sparked a vigorous political debate and so revealed their importance to the agricultural industry. A decline in backpacker numbers would cause agriculture to shrink to cope with smaller workforces. But the effects of climate change are expected to further shrink agricultural areas as extreme events and hotter temperatures impact crops, livestock, and the productivity of agricultural workers. Issues that appear manageable when viewed in isolation, such as increases in the tax rate on working holiday makers, become more problematic when viewed in conjunction with other impacts affecting agriculture. Thus, the ‘backpacker tax’ risks making food security harder to maintain at a time when Australia's agricultural system is already vulnerable to climate change.     

Development and evaluation of geochemical methods for the sourcing of archaeological maize

Strontium (Sr)-isotope values on bone from deer mice pairs from 12 field sites in the Chaco Canyon area, New Mexico, were compared with isotope values of synthetic soil waters from the same fields. The data indicate that mice obtain Sr from near-surface sources and that soil samples collected at depths ranging from 25 to 95 cm contain Sr that is more accessible to the deep roots of maize; thus, synthetic soil solutions provide better data for the sourcing of archaeological maize. However, the Sr-isotope composition of mice may be more valuable in sourcing archaeological remains of animals such as rabbit, turkey, and deer.     

Changes in regional organization and mobility in the Zuni region of the American Southwest during the Pueblo III and IV periods: insights from INAA studies

The transition from the late Pueblo III (AD 1200–1275) to Pueblo IV (AD 1275–1400) period marks one of the most dramatic eras of demographic and social upheaval in the American Southwest. At this time, much of the northern Southwest was depopulated as thousands of ancestral Pueblo people moved to new homelands. In the Zuni region, this transition included a residential shift from dispersed, largely household-scale settlements to massive, multi-storied pueblos housing hundreds of people and a simultaneous contraction of regional settlement to a central core along the Zuni River and its major tributaries. This article presents a synthesis of our recent independent efforts to utilize instrumental neutron activation analysis (INAA) to investigate changes in social interaction in the Zuni region before and after this transition. We suggest that in addition to significant local and regional settlement shifts, the Pueblo III–IV transition in the Zuni region was accompanied by a major reorganization of pottery distribution networks as clear social boundaries began to emerge between village clusters. More generally, our combined study also highlights the iterative nature of INAA data analysis, the benefits of large sample sizes, and the utility of a diachronic interpretative approach.     

Cartographic Techniques of Agricultural Regionalization

The use of a series of correlated maps is proposed as an approach to agricultural regionalization. Because of the dynamic character of farm production, two stages in the regionalization process are distinguished: a delimitation of existing agricultural regions and a delimitation of future regions. The basic principle underlying the compilation of agricultural regionalization maps IS to combine the resource base of agriculture with the actual types of farming. Maps of existing regions would also show the volume and structure of farm production, population and farm employment. In the delimitation of long-term future agricultural regions, the emphasis is on determining the potential biological productivity (climate and soils) of regions and the expected volume of production, based on food needs, industrial processing of farm products and the prospects of interregional trade in farm products.     

Recent Research on Chaco: Changing Views on Economy, Ritual, and Society

Current research on Chaco Canyon and its surrounding outlier communities is at an important juncture. Rather than trying to argue for the presence or absence of complexity, archaeologists working in the area are asking different questions, especially how Chacoan political, economic, ritual, and social organization were structured. These lines of inquiry do not attempt to pigeonhole Chaco into traditional neoevolutionary types, but instead seek to understand the historical trajectory that led to the construction of monumental architecture in Chaco Canyon and a large part of the northern Southwest in the 10th through 12th centuries. This review discusses the conclusions of current research at Chaco including definitions of the Chaco region, recent fieldwork, histories of Chaco archaeology, chronology, paleoenvironmental reconstruction, demography, political organization, outlier communities, economic organization, social organization, ritual, violence, and the post-Chacoan reorganization. Although many issues are hotly debated, there is a growing concensus that power was not based in a centralized political organization and that ritual organization was a key factor in the replication of Chacoan architecture across a vast regional landscape. Exactly how ritual, social, and political organization intersected is a central question for Chaco scholars. The resolution of this problem will prove to be of interest to all archaeologists working with intermediate societies across the globe.     

Mano size,stable carbon isotope ratios,and macrobotanical remains as multiple lines of evidence of maize dependence in the American southwest

While the level of agricultural dependence affects many aspects of human adaptation, estimating levels of dependence on maize through traditional archaeological techniques is problematic. Here we compare various measurements of manos (e.g., grinding surface area), macrobotanical evidence of maize use, and human collagen stable carbon isotope values from six regions of the American Southwest, encompassing 16 phases, as a means of assessing the power and limits of each approach for considering agricultural dependence. The analysis of each data class is considered separately, taking into account formation processes and arguments linking data and inferences. Correlations among the three data classes suggest that mano area and maize ubiquity can be considered ordinal measures of agricultural dependence, but Southwestern stable carbon isotope data have the analytical potential only to discriminate between little or no maize use and substantial maize use. The formation processes and linking arguments associated with each method must be considered when multiple lines of evidence are integrated in order to make sound behavioral inferences. Our results suggest that there were at least three patterns in the adoption of farming in the Southwest: early substantial use followed by continuous increasing maize dependence, initial intensive dependence with little change in later periods, and a long period of minor use followed by substantial dependence.     

Late Holocene Neotropical agricultural landscapes: phytolith and stable carbon isotope analysis of raised fields from French Guianan coastal savannahs

This paper summarizes phytolith analyses from four pre-Columbian agricultural raised-field sites of the coastal savannahs of French Guiana—Savane Grand Macoua, Piliwa, Bois Diable and K-VIII—and carbon isotope analyses from the first-named site. The combined phytolith and ¹³C isotope analyses evidence the transformation of the landscape from a relatively homogeneous wetland vegetation comprised of a mixture of C4 and C3 plants (the latter including Cyperaceae and other herbaceous monocots such as Marantaceae and Heliconia, Oryzoideae grasses, and other plants typical of frequently flooded areas) to the construction of raised fields that were dominated by C4 plants (maize and other Panicoideae grasses). Our analysis proves the utility of phytoliths for tracing the agricultural history of landscapes, showing that, as in other parts of the Central and South American lowlands, maize (Zea mays) was one important crop cultivated in raised fields. We also estimated the productivity of raised-field agriculture, showing that in combination with other subsistence activities, it certainly had the capacity to sustain sizeable populations.     

GLOBAL WARMING AND THE AGROCLIMATIC RESOURCES OF THE RUSSIAN PLAIN

Possible future USSR agricultural productivity, given a global warming scenario, is assessed on the basis of paleoclimatic reconstructions for optima of the Holocene and Mikulino interglacial, which may be analogs of the man-modified warm climate of the future. The calculations were made using a dynamic model of grain yields for 94 territorial units, for the most part coincident with the boundaries of oblasts. Three different indicators, which suggest that the warming trend of climate will be generally favorable for agriculture in the European USSR, are analyzed. The paper also provides insights into current spatial patterns of agricultural productivity. Translated by Larry Richardson, Glendale, CA 91202 from: Izvestiya Akademii Nauk SSSR, seriya geograficheskaya, 1990, No. 6, pp. 29-38.