22 Forty Years of Archaeobotany at Crow Canyon and 850 Years of Plant Use in the Central Mesa Verde Region

Sarah E. Oas and Karen R. Adams

In this chapter we synthesize forty years of archaeobotanical analyses in the central Mesa Verde region by Crow Canyon Archaeological Center that document 850 years of domesticated and wild plant usage during the Basketmaker III (AD 500–750) period through the late Pueblo III (AD 1225–1280) period (CCAC 2021). This is one of the largest studies of consistently acquired, examined, and reported archaeological plant sample assemblages to assess stability and change in human-plant relationships over eight centuries of time. We discuss long-term patterns of ancestral Pueblo foodways and emphasize the importance of maintaining mixed, diverse agricultural and wild plant subsistence strategies. Through combining archaeological and ethnobotanical research, this chapter provides insights into the history of a range of foods, fuels, and other economically important plants of ancestral Pueblo and other Native peoples from the Four Corners region of the US Southwest. In doing so we highlight a range of pre-Hispanic crops and gathered foods, some of which had fallen out of favor and use by the time ethnographers began recording historic plant use data in the late nineteenth and early twentieth centuries.

Background

In this chapter we draw primarily on the Crow Canyon Archaeological Center database of macrobotanical remains analyzed from over 1,500 flotation samples recovered from forty-three settlements in the central Mesa Verde (table 22.1). To address changes in plant use through time, we focus on 1,305 flotation samples that were assigned to one of nine chronological culture periods ranging from AD 500–1280. Flotation samples capture very small plant parts invisible to excavators. To address temporal changes in plant use, we rely on presence-absence, or ubiquity, calculations. The underlying assumption with ubiquity analysis is that the frequency at which one encounters certain plant taxon in an archaeological site provides a relative measure of the level of use/importance of the plant to an ancient culture (Adams 2004; Popper 1988).

Table 22.1. Analyzed archaeobotanical samples by period and context.

Period	Dates (AD)	Total Samples	Independent Feature Samples				References
Period	Dates (AD)	Total Samples	Thermal	Midden and Secondary	Other	Total	References
Early Basketmaker III	500–660	144	11	25	74	110	Adams (2020)
Late Basketmaker III	660–750	59	5	6	37	48	Adams (2020)
Pueblo I	750–920	120	19	7	71	97	Adams (1993, 2015a, 2015b, 2020)
Early PII	980–1060	46	1	26	10	37	Adams (2015a, 2015b, 2018, 2020)
Late PII	1060–1140	88	13	31	23	67	Adams (2015a, 2015b), Murray and Jackman-Craig (2003)
Early PIII	1140–1225	167	25	99	11	135	Adams (1999, 2015a, 2015b), Rainey and Jezik (2002)
Middle PIII	1210–1240	48	4	23	17	44	Adams (1999)
Late PIII	1225–1280	297	75	98	52	225	Adams (1999, 2015a, 2015b, 2018), Adams et al. (2007), Rainey and Jezik (2002)
Terminal PIII	1255–1280	336	53	148	52	253	Adams (1999, 2015a, 2015b, 2018), Adams and Brown (2000)
Total		1,305	206	463	347	1,016

Source: Table by authors.

As ubiquity calculations assume all samples in a group are independent (Popper 1988, 61), we further consolidated sample counts in cases where discrete archaeological features were heavily sampled. For example, a hearth feature sampled and analyzed as eight 1-liter flotation samples was only counted as a single sample after the results were combined. Intensive sampling of features increases chances for discovery of rare taxa and reinforces patterns of commonly utilized resources. As such, ubiquity values in this chapter are calculated from a total of 1,016 “Independent Feature” samples (table 22.1). In table 22.1, sample counts are subdivided into deposit types to allow for comparisons between plants recovered from thermal features that likely represent the last few uses of the feature, and from midden and other secondary deposit contexts (e.g., Schiffer 1987, 58–64) that provide insights into the wider range of plant preparation and discard practices accumulated over longer time periods.

Details concerning the sampling and identification methods of archaeological plant remains are accessible in the Crow Canyon Archaeological Center archaeobotanical manuals available online (Adams 2004; Adams and Murray 2004). All taxonomic nomenclature and common names used in this chapter follow A Utah Flora (Welsh et al. 1987), with updated scientific nomenclature drawn from the PLANTS Database (USDA NRCS 2021). For a complete list of all charred plants and plant parts identified in analyzed flotation and macrofossil remains, see Oas and Adams (2021a).

The Central Mesa Verde Environment

The biotic communities of the Greater Southwest, including the United States and Mexico, offer a wide range of useful plant resources (Brown 1982a). In the central Mesa Verde region, two widespread communities include the Great Basin Conifer Woodland (Brown 1982b, 52–57) and Great Basin Desertscrub lands (Turner 1982, 145–155). Some plant resources within these communities that would be of interest to human groups are listed in table 22.2. Within the region, there are additional biotic communities (Brown 1982a) that would also offer a diversity of plant resources requiring travel or trade.

Table 22.2. Environmental traits and some useful plant resources in the major biotic communities of the central Mesa Verde area.

Biotic Community	Environmental Traits	Trees	Shrubs	Perennials	Annuals	Reference
Great Basin Conifer Woodland	1500–2300 m amsl; annual precipitation averages 250–500 mm, spread through the year; growing season averages 215 days	Juniper (Juniperus) and pine (Pinus) species are common	Saltbush (Atriplex), sagebrush (Artemisia), yucca (Yucca spp.), sumac (Rhus), rabbitbrush (Chrysothamnus), mountain mahogany (Cercocarpus), oak (Quercus)	Cacti (Opuntia, Echinocereus, Mammillaria), grasses	Beeweed (Cleome), goosefoot (Chenopodium), mallow (Sphaeralcea), pigweed (Amaranthus), sunflower (Helianthus)	Brown (1982b, 52–57)
Great Basin Desert Scrub	1200–2200 m amsl; annual precipitation averages less than 250 mm; strong winter rains in the west, shifting to summer rains in the east	Restricted to drainages and basins	Sagebrush species (Artemisia tridentata; A. bigelovii; A. arbuscula)	Cacti (Opuntia, Echinocereus, Ferocactus, Mammillaria), sedge (Cyperus), grasses	Wild mints (Salvia), wild beans (Phaseolus)	Turner (1982, 145–155)

Biotic Community

Environmental Traits

Trees

Shrubs

Perennials

Annuals

Reference

Great Basin Conifer Woodland

1500–2300 m amsl; annual precipitation averages 250–500 mm, spread through the year; growing season averages 215 days

Juniper (Juniperus) and pine (Pinus) species are common

Saltbush (Atriplex), sagebrush (Artemisia), yucca (Yucca spp.), sumac (Rhus), rabbitbrush (Chrysothamnus), mountain mahogany (Cercocarpus), oak (Quercus)

Cacti (Opuntia, Echinocereus, Mammillaria),

grasses

Beeweed (Cleome), goosefoot (Chenopodium), mallow (Sphaeralcea), pigweed (Amaranthus), sunflower (Helianthus)

Brown (1982b, 52–57)

Great Basin Desert Scrub

1200–2200 m amsl; annual precipitation averages less than 250 mm; strong winter rains in the west, shifting to summer rains in the east

Restricted to drainages and basins

Sagebrush species (Artemisia tridentata; A. bigelovii; A. arbuscula)

Cacti (Opuntia, Echinocereus, Ferocactus, Mammillaria), sedge (Cyperus), grasses

Wild mints (Salvia), wild beans (Phaseolus)

Turner (1982, 145–155)

Results

Based on the analyses of routinely collected flotation samples, and on the record of larger plant macrofossils retrieved by hand during excavation (see Oas and Adams 2021a), the subsistence record indicates the following. Across all time periods, a total of five domesticated crops, including four Mesoamerican domesticates—maize (Zea mays), beans (Phaseolus sp.), squash (Cucurbita sp.), and gourds (Lagenaria sp.)—and one Indigenous US Southwestern domesticate, little barley (Hordeum pusillum) were identified. An additional seventy wild plants were also identified (2021a). Reproductive plant parts, most likely deposited as part of food preparation and cooking activities, suggest fifty-six of these domesticated and wild plants were consumed as foods and/or medicines based on both archaeological context and the historic ethnographic record. In addition, we present evidence of nonreproductive remains of thirty wild plants likely used for fuelwood, construction, and a variety of other economic and/or ritual activities.

Top-Ranking Plant Foods

Figure 22.1a presents ubiquity information for the top five ranked plants foods. For complete ranking and ubiquity data for the top ten ranked plant foods, see Oas and Adams (2021b). Domesticated maize is the most frequently recovered food in all periods examined, suggesting it was the most important food source through time. From the Pueblo I period (AD 750–920) onward, a mixture of whole maize ears, cob, and kernel remains provide row-number and kernel endosperm data (e.g., Adams 2015a, 2015b, 2018; Adams et al. 2007) that can be used to understand ancient maize varieties. Overall, farmers in the central Mesa Verde region consistently maintained a diverse range of maize varieties, with 8–16 kernel rows that resemble previously described ancient varieties of 10–16 rowed flinty and 12–14 pop/flinty maize from the Mesa Verde region called “Pima-Papago” (Adams 1994, 277). Floury endosperm maize may belong to the Maís de ocho landrace, an eight-rowed maize of easy-to-grind floury maize that was adopted in the northern Southwest by at least AD 500 (e.g., Galinat 1970) and that previous research suggests was widely grown across the northern US Southwest by the thirteenth century AD (Oas 2019, 115–118).

Line graphs of ubiquity values of plant food and fuel remains through time from the early Basketmaker III through terminal Pueblo III periods — Figure 22.1. Ubiquity of (a) top five ranked foods and (b) top three ranked fuelwoods from all sampled contexts during the Basketmaker III period–Pueblo III period and terminal Pueblo III period thermal features. Courtesy of the Crow Canyon Archaeological Center.

Other top-ranked plants (listed in descending order) include pigweed (Amaranthus sp.), goosefoot (Chenopodium sp.), groundcherry (Physalis sp.), purslane (Portulaca sp.), grasses (Poaceae), prickly pear (Opuntia sp.), ricegrass (Achnatherum hymenoides), sagebrush (Artemisia sp.), tansy mustard (Descurainia sp.), and bulrush (Scirpus sp.) (see Oas and Adams 2021b). That the second through fourth top ranking plant foods are weedy species indicate these rapid-growing plants were consistently important foods that were tolerated and perhaps even encouraged to grow in agricultural fields, kitchen gardens, and other disturbed areas such as trash heaps and pathways. Other highly ranked slower-growing perennial plant foods, such as rice grass and prickly pear, speak to the long-standing importance of collecting foods that ripened throughout the year and found in a range of microenvironments (e.g., arid, riparian). These resources could offset shortfalls in domesticated crop harvests and supply foods in the early spring, when crops were not yet ripe and food stores from the previous harvest were in low supply.

Top-Ranking Fuelwoods

Across all time periods, a total of at least twenty-seven fuelwood species were identified (Oas and Adams 2021a). Juniper (Juniperus sp.) is consistently the highest-ranking fuel resource whose high ubiquities suggest continual preference and access as fuelwoods in every time period. Pinyon pine (Pinus edulis) and sagebrush follow as typically the second- and third-most highly ubiquitous fuelwoods (figure 22.1b). These are major components of the extensive pinyon-juniper woodland and sagebrush/bitterbrush shrublands present in the region. Other top-ranking fuelwoods (Oas and Adams 2021b) include serviceberry (Amelanchier sp.)/peraphyllum (Peraphyllum sp.), mountain mahogany (Cercocarpus sp.), saltbush (Atriplex sp.), oak (Quercus sp.), bitterbrush (Purshia sp.), rabbitbrush (Ericameria sp.), and poplar (Populus sp.)/willow (Salix sp.)—all woody plants present in the modern vegetation communities.

Discussion

The archaeobotanical results presented here for the most ubiquitous/top-ranking foods from over forty sites in central Mesa Verde region occupied from AD 500–1280 are well supported by previous studies of coprolites (e.g., Minnis 1989) and bone chemistry in the northern San Juan region (e.g., Matson 2016). Due to a range of morphological and cultural factors (see Gasser and Adams 1981, 183–184), domesticated beans do not rank in this macrobotanical record. However, they were likely important crops, and studies of coprolites from the Basketmaker III period to the Pueblo III period rank both squash and beans among the most frequently recovered foods (Minnis 1989).

Changes through Time in Food and Fuelwood

There are several changes in the rankings of foods and fuelwoods from the Basketmaker III period to the Pueblo III. The top-ranked foods in the Basketmaker III period are somewhat different from later periods. Tansy mustard ranks highest (third and fourth) in early and late Basketmaker III period samples and drops to eighth or is unranked thereafter (Oas and Adams 2021b). This late winter / early spring resource may have experienced reduced populations due to repeated harvesting during the extended Pueblo occupation of the region. Spiderling (Boerhaavia sp.) only ranks in the early Basketmaker III period (Oas and Adams 2021b) and is thought to be a nonlocal food. Along with a little barley caryopsis (grain) recovered from the late Basketmaker III period, spiderling and little barley suggest connections existed in the Basketmaker III period between the central Mesa Verde region and Hohokam peoples living hundreds of miles to the Southwest (Graham et al. 2017; also see Schleher et al., chapter 10 in this volume). In contrast, physalis and prickly pear rank higher in Pueblo I period through terminal Pueblo III period samples.

Juniper wood ubiquities suggest there may have been some decrease in juniper fuelwood availability in two periods: (1) the Pueblo I and (2) the early-mid Pueblo III periods (AD 1140–1240). The lowest recorded juniper ubiquity (73%) is during the Pueblo I period, which supports previous regional assessments of anthropogenic pinyon-juniper woodland reductions (Kohler and Matthews 1988). A second downward trend in pinyon ubiquity can be seen in a drop in pinyon ubiquities from 87 percent in the early Pueblo III period (AD 1140–1225) to 75 percent in middle Pueblo III period samples (AD 1225–1240) (figure 22.1b). Pinyon pine ranks as the second-most-common fuelwood in every period but the early (AD 980–1060) and late Pueblo II periods (AD 1060–1225). There is a major increase in sagebrush wood ubiquity in the early Pueblo II period to 73 percent, and the late Pueblo II period has the highest-recorded sagebrush ubiquity of 78 percent. This high sagebrush ubiquity suggests the Pueblo II period was characterized by an increasingly open, agricultural landscape with perhaps some overall reduction in pinyon-juniper woodlands surrounding settlements. Finally, sagebrush ubiquities drop to 56 percent in the early Pueblo III period and reach a low of 16 percent in the middle Pueblo III; these are periods where juniper and pinyon pine ubiquities also decrease, suggesting fuelwood scarcity was more widespread during the late twelfth and early thirteenth centuries AD.

Periods of Food Abundance and Stress

Ubiquities of maize and other weedy wild plant food data suggest certain periods were characterized by an abundance of crops and other preferred foods. The Pueblo II period appears to have largely been one with remarkably successful maize agriculture with some of the highest maize ubiquities. The highest ubiquity for kernel/embryo parts (42%) occurs in the late Pueblo II period (Oas and Adams 2021b).

Macrobotanical evidence also suggests farmers may have experienced several periods of food stress in the central Mesa Verde region. There are three periods in which maize is ranked second and goosefoot/amaranth rank as the most frequently recovered food: (1) the late Basketmaker III (AD 660–750); (2) the late Pueblo II; and (3) the early Pueblo III periods. These weedy species were likely relied on in times of crop shortfalls. While additional work is needed to address temporal and contextual patterns in plant food diversity/richness, previous studies have noted increases in the number of wild food species in samples from late Basketmaker III, late Pueblo II, and early Pueblo III period settlements (Adams 2015a, 321; 2015b, 104; 2020, 603). While some of these species may represent overlapping medicinal and/or ceremonial uses, the greater range of plants identified in samples from these periods supports arguments that communities engaged with and collected a broader range of plant foods due to diminished harvests or possibly increasing population pressures on existing resources.

Decreases in maize ubiquity in the middle Pueblo III and terminal Pueblo III periods (AD 1255–1280) thermal samples provide some additional evidence for food stress. The middle Pueblo III period has the lowest maize ubiquities of any period, and the ubiquities of nearly all other top-ranked wild foods also decrease (figure 22.1a). While relatively low sample numbers may be a factor, consistently lower ubiquities of the most highly ranked food plants suggest some degree of food stress was experienced by communities during this period. As this period falls between both the prolonged drought of AD 1130–1180 (e.g., Ryan 2010) and the “Great Drought” between AD 1276 and 1299 (e.g., Schwindt et al. 2016), the low ubiquities may indicate that the recovery from agricultural downfalls in the late Pueblo II / early Pueblo III periods was slow and/or that population increases and social unrest were additional factors adding to food insecurity. In the terminal Pueblo III period, maize recovery rates from thermal features (64%) are lower than in midden contexts (79%) (Oas and Adams 2021b), indicating less maize was available when the last meals were being prepared (also see Kuckelman, chapter 19 in this volume).

Overall, it is difficult to confidently assess precisely how certain foods grew into or fell out of use through time and what factors best explain these trends. Possible influences include changes in climate (i.e., wet-cold/warm-hot conditions that would affect the productivity of various crops/wild plants) and anthropogenic shifts in local vegetation due to agricultural expansion and continuous harvesting of foods and fuels over multiple generations. Climatic conditions and the changing local, occupied landscapes would each factor into the decisions agricultural communities made about the relative costs and benefits of gathering and processing different foods. Other social factors include changes in mobility (e.g., residential mobility, restricted movements due to warfare or social boundaries [see Arakawa et al., chapter 15 in this volume]), exchange networks, and settlement that would alter how often communities encountered and/or could access certain foods. Additional social factors might include more subtle changes in the social value placed on acquiring and preparing various foods/medicines to express or reinforce particular social identifies (e.g., Chacoan, Hohokam) and/or to participate in public feasts/ceremonials.

Conclusions and Future Research

Overall, from AD 500 to 1280, our research suggests there is little change in the top-ranked foods (or fuels). The subsistence economy consisted of a mixture of maize agriculture supplemented by other crops and a wide range of preferred encouraged and/or gathered wild plants established by the early Basketmaker III period. This pattern persists through periods of climatic and social instability until the point of regional depopulation. The Crow Canyon plant database is the largest and most consistently analyzed source of ancient plant remains for the Greater Southwest. These data offer a remarkable opportunity for future research exploring issues of food and fuel use across multiple temporal and spatial scales. Future work, particularly studies exploring issues of plant diversity and richness, will be beneficial.

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