Earth Ovens and Desert Lifeways : 10,000 Years of Indigenous Cooking in the Arid Landscapes of North America 9781647691141, 9781647691165

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Earth Ovens and Desert Lifeways

Earth Ovens and Desert Lifeways 10,000 Years of Indigenous Cooking in the Arid Landscapes of North America

Edited by Charles W. Koenig and Myles R. Miller

The University of Utah Press Salt Lake City

The publisher gratefully acknowledges the George C. Frison Institute of Archaeology and Anthropology at the University of Wyoming for their generous support of this work.

Copyright © 2023 by The University of Utah Press. All rights reserved. The Defiance House Man colophon is a registered trademark of the University of Utah Press. It is based on a four-­foot-tall Ancient Puebloan pictograph (late PIII) near Glen Canyon, Utah. Names: Koenig, Charles W., editor. | Miller, Myles R., editor. Title: Earth Ovens and Desert Lifeways : 10,000 Years of Indigenous Cooking in the Arid Landscapes of North America / Charles W. Koenig, Myles R. Miller. Description: Salt Lake City : University of Utah Press, [2023] | Includes bibliographical references and index. Identifiers: LCCN 2022950977 | ISBN 9781647691141 (hardcover : alk. paper) | ISBN 9781647691165 (ebk) | LC record available at https://lccn.loc.gov/2022950977 Errata and further information on this and other titles available online at UofUpress.com Printed and bound in the United States of America.

In Memoriam: Dr. Douglas B. Craig

In May of 2020, Doug Craig passed away after a long illness complicated by COVID-­19. With his passing, Doug left behind a wonderful wife, Rebecca, and too many friends to count. He was a consummate professional, a dedicated researcher, a prolific author, and a mentor to many. Doug was just as comfortable digging features as he was editing manuscripts or teaching people about archaeology. He was a humble man, but with his passing archaeology lost a great mind, cultural resources lost an advocate, and all of us lost a friend. In Memoriam: Dr. Alston V. Thoms

Alston V. Thoms died unexpectedly in June 2021, not long after completing revisions to the final chapter of this volume. This contribution is literally and figuratively his last word on what many of us recognize as his most important intellectual gift to archaeology: the importance of the “Carbohydrate Revolution” for humankind in North America. Thoms’s 45-­year career in archaeology included decades of field research in south-­central, southeast, and northwest North America in both CRM and academic arenas. He and his teams documented hundreds of FCR features that he recognized held much more meaning and research potential than most twentieth-­century archaeologists understood. Through ethnographic, scientific, and experiential studies, Thoms and his colleagues, including many of the authors of this volume, have amply demonstrated the importance and potential of hot rock studies across the world. “Rock on in solidarity!”

Contents



List of Figures ix



List of Tables xi

1. Lighting the Fire: An Earth Oven Introduction 1 Charles W. Koenig and Myles R. Miller

Part I. Hunter-­Gatherers of “Texas” 2. Late Paleoindian Earth Ovens in the Texas Big Bend 9 Richard Walter and Bryon Schroeder 3. Central Texas Plant Baking 24 Richard McAuliffe, R aymond Mauldin, and Stephen L. Black 4. Using Fire-­Cracked Rock to Evaluate Earth Oven Intensification in the Lower Pecos Canyonlands of Texas 41 Charles W. Koenig, Emily R. McCuistion, Stephen L. Black, Charles D. Frederick, J. Phil Dering, J. Kevin Hanselka, Leslie Bush, and Ken L. Lawrence

Part II. Hunter-­Gatherers of the Southern Great Basin and Lower Colorado River 5. Fire on the Mountain: The Use of Earth Ovens for Agave and Pinyon Processing in the Sheep Range, Nevada 69 Spencer Lodge 6. Hot-­Rock Cooking of Desert Lily (Hesperocallis undulata) and Winding Mariposa Lily (Calochortus flexuosus) Bulbs in the Lower Colorado River Basin 84 Eric Wohlgemuth, Daron Duke, Sarah K. Rice, James R. Kangas, and Mark C. Slaughter

Part III. Agriculturalists of the U.S. Southwest and Northern Mexico 7. Labor, Ritual, and Path Dependence: The Social Dimensions of Earth Oven Use in Southern New Mexico and West Texas 105 Myles R. Miller and Timothy B. Graves 8. Social Implications of Roasting Pits in Southern Arizona Hohokam Rockpile Fields 120 Suzanne K. Fish and Paul R. Fish 9. Tradition and Community: Hornos, Thermally Altered Soils, and Communal Feasting among the Hohokam 143 Eric S. Cox, Gary Huckleberry, and Douglas B. Craig vii

Contents

viii

10. An Ethnoarchaeology of Earth Ovens in the Sierra Catorce, Mexico 160 Richard Stark

Part IV. Earth Oven Discussion 11. Hot-­Rock Cooking in the U.S. Southwest and Mexican Northwest: An Emphasis on Practice and Significance among Village Farmers 177 Paul R. Fish 12. Learning from Rock: Cook-­Stone Technology’s Epistemological Maturation 188 Alston V. Thoms

References 201



Contributors 239



Index 241

Figures

1.1. Earth oven heating element v­ ersus

a burned rock midden 2.1. Late Paleoindian earth oven sites, Big Bend region, Texas 2.2. Map of Paradise Draw sites 2.3. Late Paleoindian earth ovens, GLD site 2.4. Radiocarbon dates from Late ­Paleoindian thermal features 2.5. Features 1 and 2 exposed in an arroyo at GLD 2.6. Feature 2 at GLD 2.7. Perforator tip and projectile point base from Late Paleoindian ­deposits, GLD site 3.1. Central Texas earth oven features 3.2. Map of the Edwards Plateau, Texas 3.3. Edwards Plateau counties and ­numbers of radiocarbon dates 3.4. Summed probability distribution for 376 earth oven radiocarbon dates, Edwards Plateau 3.5. Summed probability distribution for earth oven radiocarbon dates by oven size class 4.1. Map of Eagle Nest Canyon ­rockshelters 4.2. Eagle Cave profile 4.3. Profiles of Kelley Cave, Skiles Shelter, and Horse Trail Shelter 4.4. Idealized cross-­section of an earth oven facility 4.5. Boxplots of FCR density by K-­means cluster, and changes in FCR density through time 4.6. Summed probability distribution of Lower Pecos radiocarbon dates compared to changes in FCR ­density

5.1. Map of the Sheep Range, southern

2

Nevada

70

the blackbrush community

72

the Pinyon-­Juniper community

73

from Google Earth

74

­elevation

76

5.2. Sheep Range roasting pit within

10 15

5.3. Sheep Range roasting pit within

16

5.4. Sheep Range roasting pits viewed

17

5.5. Roasting pit measurements by

18 18

5.6. Scatter plot of roasting pit size by

elevation within Creosote Brush and Blackbrush communities 5.7. Scatter plot of roasting pit size by elevation within the Mixed Shrub and Pinyon-­Juniper communities 6.1. Map of study areas, lower Colorado River Basin 6.2. Salton Basin location 6.3. Roasting feature photos 6.4. Desert lily (Hesperocallis undulata) photos 6.5. Mormon Mesa location 6.6. Winding mariposa lily (­Calochortus flexuosus) photos 7.1. Map of burned rock midden sites, Sacramento Mountains, south-­ central New Mexico 7.2. Feature 59, LA143472 7.3. Feature 1, LA91458 and distance to nearby rock sources 7.4. Summed probability distributions of radiocarbon dates for plant-­ baking facilities, Jornada region 7.5. Comparison of radiocarbon summed probability distributions for plant-­baking facilities and maize 8.1. An Agave murpheyi flowering in a Hohokam rockpile

21 25 26 27 30 31 48 49 50 51 58

61 ix

78 79 85 88 90 92 94 96 106 108 110 114 117 122

x

Figures

8.2. Agricultural features and commu-

nal roasting pits in the Marana ­community 8.3. Locations of Zanardelli, T ­ umamoc Hill, Marana, and McClellan ­subdivisions 8.4. Map of the Marana community 8.5. Idealized cross-­section of the ­Marana community 8.6. Map of the McClellan Community 8.7. Agaves (Agave murpheyi) in ­rockpile clonal group 8.8. Agave and other wild perennial species taking root in a Hohokam rockpile 8.9. A Marana Community rockpile field 9.1. Hohokam culture area and location of SRPMIC-­114 9.2. Project area map at SRPMIC-­114 and selected horno features 9.3. Stratigraphic profile of Feature 26 and Feature 27

9.4. Photographs of thermally altered 123 124 126 127 130 136

10.1. 10.2. 10.3. 10.4. 10.5. 10.6.

140

10.7. 11.1.

147 148

148

SRPMIC-­114

149

9.6. Stratigraphic profile of horno

137

145

soils

9.5. Plan view of Feature 26,

12.1.

­ eature 98 inset into horno F Feature 72, SRPMIC-­114 Map of the Chihuahuan Desert and location of the Sierra Catorce Quiote harvest using a rajiar Firing the thermal elements Layered quiote and agave leaves The archaeological signature of a quiote oven The archaeological signature of a barbacoa oven Chacuaco Palomas FCR midden Deflated hot rock across the La Playa site, northwest Sonora, Mexico Geographic distribution of study areas

153 162 164 166 167 168 170 171 180 193

List of Tables

2.1. Radiocarbon dates from Late Pa-

leoindian thermal features, Texas Big Bend 2.2. Feature attributes from Late Paleo­ indian thermal features, Texas Big Bend 2.3. Rock sort data for GLD Late Paleo­ indian earth oven features, Texas Big Bend 3.1. Compiled Radiocarbon Dates for Central Texas Burned Rock Midden (BRM) Features 3.2. Compiled radiocarbon dates for central Texas individual oven (IO) features 3.3. Burned rock midden features (BRMs) with identified macro­ botanical remains 3.4. Individual oven (IO) features with identified macrobotanical remains 4.1. Summary of Eagle Nest Canyon Rockshelter earth oven facilities 4.2. Rock sort data and cluster assignment, Kelley Cave earth oven ­facilities 4.3. Rock sort data and cluster assignment for Eagle Cave Earth oven facilities 1–5 4.4. Rock sort data and cluster assignment for Eagle Cave earth oven facilities 6–8, 10, and 12 4.5. Average rock sort data by Eagle Nest Canyon earth oven facility and cluster 5.1. Roasting pit total count and ­measurement data according to vegetative community

5.2. Mann-­Whitney U test results for

central depression measurements

77

exterior measurements

77

5.3. Mann-­Whitney U test results for

13

6.1. Thermal feature type characteristics,

northern Mojave Desert, Mormon Mesa, Salton Basin 6.2. Nutritional constituents of selected Native American bulb and corm foods 6.3. FAR features per acre by kilometers to Lake Cahuilla shoreline 6.4. Geophyte macrofloral finds by site type and flotation sample volume 8.1. Agave plant parts from 15 Marana roasting pits in 12 Classic period rockpile fields 8.2. Average cultivated ha per roasting pit in four Classic period Hohokam communities 9.1. Radiocarbon Dating for the SRPMIC-­114 hornos 9.2. Texture and chemical data on ­sediments and soils adjacent to hornos, SRPMIC-­114 9.3. Thermal halo colors and inferred processes associated with Hohokam hornos 11.1. Cumulative roasting-­pit capacities and projections, Hohokam Grewe site and Paquimé 12.1. Summary of hot rock studies ­presented in this volume 12.2. Summary of earth oven morphologies, foods, and other data from studies presented in this volume

14 20 28 29 34 35 46 52 54 56 57 75

xi

86 93 93 101 127 139 150 154 155 184 194 196

1 Lighting the Fire An Earth Oven Introduction Charles W. Koenig and Myles R. Miller

For over 10,000 years, earth ovens have played important economic and social roles for Indigenous peoples living across the arid landscapes of North America. The remains of earth ovens — ​notably the massive ­ accumulations of fire-­cracked rock (FCR) and charred earth known as earth oven facilities, roasting pits, and burned-­ rock middens  — ​ are common from Texas to California and south into Mexico. Earth ovens served an important role for hunter-­gatherers, formative horticulturalists, sedentary farmers, as well as contemporary Indigenous people, by converting inedible plants into digestible food, fiber, and beverage. Yet, d ­ espite the long-­term ubiquity and broad spatial and cultural distribution of earth ovens from Late Paleoindian times until today, archaeological investigations of these features have earned relatively little attention in the way of directed research. This volume explores the longevity and diversity of earth oven baking within the Chihuahuan, Sonoran, and Mojave Deserts and ­e xamines the subsistence strategies, technological organization, and social contexts within which earth ovens functioned. The geographic emphasis (southwestern United States and northeastern Mexico) is in part due to the ­editors’ familiarity with this region but also because earth oven use spans the entire Holocene archaeological record (Koenig et al., this volume; Walter and Schroeder, this volume), there is a rich ethnographic record (e.g., ­Castetter

et al. 1938; Ferg 2003), and contemporary Indigenous peoples continue to use earth oven technology (Houghten 2019; Stark 2002, this volume). The following chapters reflect an array of promising research studies highlighting ongoing efforts to understand the archaeological record of earth oven cookery and FCR more broadly. Each chapter highlights useful archaeological methods for investigating earth ovens. Although this volume uses intensification as a unifying theoretical paradigm for discussing earth oven technology (Morgan 2015; Thoms 2008a, 2009), some papers expand their theo­ retical approaches to incorporate alternative perspectives and consider how those perspectives might be more holistically investigated in the context of earth oven subsistence and labor intensification. The variety of methods and ­theory described herein demonstrate the diversity of useful archaeological techniques for evaluating earth oven cooking. What Are Earth Ovens?

Earth ovens are semisubterranean layered arrangements of heated rocks, packing material, and foodstuffs capped by earth that slowly transform (bake) food in a moist environment through the process called hydrolysis (Black and Thoms 2014; Wandsnider 1997:4). In most instances, rocks are first heated in a fire and then arranged into a circular heating element (or oven bed) upon which moist green plants 1

Figure 1.1. An isolated earth oven heating element (top) compared to an aggregate burned rock

midden (bottom). Lower image courtesy Mark Willis.



Lighting the Fire

(packing material), then foodstuffs, then more packing material are placed. This layered stack is then sealed with a thick layer of earth, thus forming an oven that can hold steamy heat for several days. The cooking temperature within an earth oven is generally maintained at the boiling point of water (100°C). Foods that have more complex carbohydrate chains require longer cooking to successfully convert indigesti­ ble carbohydrates into digestible components (Thoms et  al. 2018; Wandsnider 1997). Although rock heating elements are not used for all earth oven cooking, most plants — ​including all species of Agave spp. and most geophytes — ​ require the use of hot rocks because the plants must be baked for 12–48 hours to render them edible (e.g., Dering 1999; Smith et  al. 2001; Thoms 1989; Thoms et al. 2018). The primary, tell-­tale artifacts generated by earth oven construction are burned rocks, often termed fire-­cracked rock (FCR) or fire-­ altered rock (FAR). These ubiquitous artifacts are encountered in virtually all geographic and cultural contexts, from the eastern woodlands to the Pacific Coast (Fonseca Ibarra et al. 2019; Wilson and VanDerwarker 2015), and the Arctic to the Yucatán (Salazar et al. 2012; Urban et al. 2019). Burned rocks are found in a range of contexts, but archaeologists frequently encounter them in tight, circular arrangements we often call “hearths” (Figure 1.1). In fact, these features should more appropriately be considered earth oven heating elements (Black and Thoms 2014). In many instances, archaeologists encounter larger, sometimes diffuse, concentrations of burned rocks. These amalgam features are generally what archaeologists refer to as burned-­ rock middens, ring middens, roasting pits, or earth oven facilities (Black and Thoms 2014) and represent locations where multiple earth ovens were constructed over time. As a baking locality is reused, refuse accumulates — ​primarily FCR but also food waste, ash, and c­ harcoal — ​ around a central depression or oven pit. Often these baking facilities resemble donut- or crescent-­shaped rings and can be substantial features on the landscape (Figure 1.1). In most

3

hunter-­gatherer contexts, the central pits are relatively shallow (less than 1 m deep) and less than 2 m in diameter (Dering 1999; Yu 2006, 2009). Within agricultural groups, earth oven pits can be more formally constructed features several meters in depth and carefully lined with rocks (Craig and Woodson 2017; Miller and Graves 2011, 2012; Minnis and Whalen 2005). Further, depending on the types of food being cooked (e.g., agaves, geophytes, cholla bulbs, or meat) the shape of the pit and the amount of rock changes. In other words, there are many variations on the earth oven theme. Earth Oven Research

It stands to reason that such a widespread technology with high archaeological visibility would command substantial archaeological attention. However, until recent decades, that has not been the case. Historically, most earth oven research has been confined to cultural ­resource management (CRM) compliance projects (see references cited for this volume), with occasional papers published in widely available aca­ demic journals or scholarly books (e.g., Black and Thoms 2014; Brink and Dawe 2003; Custer 2017; Dering 1999; Fonseca Ibarra et al. 2019; Fulkerson and Tushingham 2021; Graesch et al. 2014; Miller 2019; Miller and Montgomery 2019; Neubauer 2018; Salazar et al. 2012; Smith and McNees 1999; Thoms 2008a, 2009; Urban et  al. 2019; Wilson and VanDerwarker 2015). This research bias has resulted in a massive amount of gray literature that is often minimally cited and regionally compartmentalized. Further, the methods and techniques used to evalu­ ate burned rock vary widely among projects. Often, FCR and earth ovens are interpreted as simply the deflated remains of generic cooking practices carried out in “hearths.” Thoughtful studies of burned rocks have usually been the exception rather than the norm (Black and Thoms 2014). In recent decades, there has been progress, as archaeologists increasingly recognize the lowly burned rock as a legitimate artifact class with potential to yield data bearing on a range

4

Charles W. Koenig and Myles R . Miller

of behaviors — ​from subsistence to ceremony and ritual. However, without the contributions of CRM archaeology, earth oven and FCR research would remain a sidebar. Methodological Approaches

As with any subfield in archaeology, there are a variety of methods that can be applied toward studying earth ovens and FCR. In many ways, the first step is identifying two key pieces of information: (1) whether earth ovens are the primary source of FCR within archaeological sites and (2) what foods were being cooked (Dering 1999; Smith and McNees 1999; Wohlgemuth et al., this volume). From there, archaeologists can begin exploring higher-­level implications of hot-rock cooking. Increasing attention has been paid to defining variability in the morphology and content of earth oven facilities with regard to size and construction of the central baking pit, volume and content of surrounding FCR discard middens, and types of ancillary features surrounding the central pit or adjacent to the facility (Eskenazi and Roberts 2007, 2010, 2011; Miller 2019; Miller et al. 2011; Neubauer 2018; Yu 2006, 2009). Tool assemblages associated with agave processing in earth ovens have also received attention (Bernard-­Shaw 1990; Fish et al. 1992a, 1992b, 1992c; Miller et al. 2011). These are not simply descriptive pursuits. Variability among key attributes provides critical insights into the use histories of earth ovens and their subsistence and economic roles, as well as diachronic perspectives on how the construction, provisioning, and use of earth ovens changed in response to environmental, demographic, and social factors. Evaluating Social Aspects of Earth Ovens

The ethnographic record of earth oven baking among Indigenous people clearly demonstrates earth ovens provided more than just an economic benefit. Foods and/or associated products (alcohol) linked with earth ovens are commonly prepared during social aggregations (Lumholtz 2011a [1903], 2011b [1903]; Miller

2019). For instance, among the Apache, earth ovens are integrated into women’s p ­ uberty cere­monies (Houghten 2019; Opler 1941). Earth ovens are further incorporated into the religious beliefs of other Indigenous peoples (Lumholtz 2011b:169), and there is ample evidence of offerings and rites associated with firing and lighting earth ovens (Castetter and Opler 1936:36; Gifford 1932:206; Kiffen et al. 1935:52; Opler 1941:​ 117). In other words, earth ovens do not solely reflect subsistence behaviors or optimal foraging decisions. These features played significant roles in political economies, community organization, and social production among Indige­ nous societies throughout the southwestern United States and northwestern Mexico. Beyond food production, earth ovens were used to produce fermented beverages and bulk quantities of food for communal feasts and to establish and maintain reciprocal social relationships across communities and territories. These dimensions of earth oven use do not readily translate into optimal foraging models but nevertheless have critical implications for social complexity and how the effects of intensification on common resources, land tenure, and collective cooperation among groups may have been mediated through feasting and related uses (e.g., Hayden 2014). The social implications and roles of earth ovens are better preserved (archaeologically) among agriculturalists. Several of the papers in this volume (Cox et al.; Fish and Fish; Miller and Graves) demonstrate the important roles of earth ovens — ​and the foods baked within — ​ for agricultural societies, and there can be little doubt concerning the communal actions required for earth oven construction. Identifying social behaviors among hunter-­gatherer earth ovens is more challenging but should nevertheless continue to be a research objective. Several of the hunter-­gatherer papers in this volume present preliminary hypotheses regarding the social, ceremonial, and ritual aspects of earth oven construction. Future research will aim to expand our Western world view of hunter-­ gatherer earth ovens.



Lighting the Fire Earth Ovens and Intensification

Many archaeologists argue that earth ovens are markers of subsistence intensification. Intensification is a concept that has been defined in different ways, but for this volume — ​and to avoid the intensification pitfalls discussed by Morgan (2015) — ​we use Boserup’s definition: intensification is an increase in subsistence-­related labor due to a decline in foraging efficiency caused by increasing local or regional population (­Boserup 1965, 1981). The remains of earth ovens are ubiquitous features in the Holocene archaeological record of North America (Thoms 2009). Ovens were most frequently used to bake low-­ ranking but predictable plant resources, such as geophytes and desert succulents, that would be otherwise indigestible to humans (Wandsnider 1997). That archaeologists consider earth ovens material indicators of intensification is due in large part to the high energetic costs and rela­ tively low caloric yields (Dering 1999; Smith and McNees 1999). Those working in the U.S. Southwest, Texas, and the Pacific Northwest argue that earth oven intensification was spurred by regional population increase (Dering 1999; Freeman 2007; Johnson and Hard 2008:​148; Morgan 2015; Thoms 1989, 2008a; Yu 2009). In fact, Alston Thoms (2008a) refers to the widespread occurrence of earth ovens across temperate North America in the early Holocene as the “carbohydrate revolution.” Radiocarbon compilations of dated earth ovens in Texas and southern New Mexico suggest earth ovens were used with increasing frequency over the last two millennia (e.g., Black and Creel 1997:274; Mauldin and Nickels 2003a, 2003b:168; Miller and Graves 2011:214). Interpretations of this trend link earth oven intensification with demo­ graphic increase (e.g., Dering 1999; Freeman 2007; Thoms 1989, 2008a; Yu 2009). Yet demographic change may not have been the sole factor leading to the intensification of earth oven technologies. An alternative, yet related, perspective is that the social dynamics resulting from demographic change provided impetus for intensification of earth oven use. Such relationships were complex and reflexive,

5

and regions where earth ovens were widely used provide a fascinating laboratory for the study of interrelated dynamics of demographics, intensification, and social complexity. Every chapter in this volume discusses how earth ovens and FCR within specific regions fit into the broader concept of subsistence intensification. Still, even though intensification theory provides a unifying theoretical thread throughout the following chapters, we do not believe intensification is the only theoretical paradigm through which earth ovens can be or should be evaluated. Organization

This volume is organized into four sections with chapters clustered by geographic area and subsistence/economic strategies: hunter-­gatherers of “Texas”; hunter-­gatherers of the southern Great Basin and lower Colorado River; agriculturalists of the southwest U.S. and northeast Mexico; and a discussion section. The Texas chapters begin with a description of Late Paleo­ indian earth ovens in the Texas Big Bend by Richard Walter and Bryon Schroeder. Richard McAuliffe and colleagues provide a summary of earth oven use in Central Texas, focusing on radio­carbon dates and macrobotanical data, and Charles Koenig and colleagues demonstrate how FCR can be used to evaluate earth oven intensification using a case study from the Lower Pecos Canyonlands. In the Great Basin section, Spencer Lodge describes remote sensing of large roasting pits in the Sheep Range of Nevada and how roasting pit size changes with elevation and plants being cooked. Eric Wohlgemuth and colleagues describe how understanding ecological distributions of plant species in the lower Colorado River can inform earth oven function despite poor (or limited) preservation of botanical or faunal remains. While the volume’s first two sections are primarily focused on hunter-­gatherers, the third section describes earth oven use among agricultural groups in Arizona, New Mexico, far West Texas, and San Luis Potosi, Mexico.

6

Charles W. Koenig and Myles R . Miller

I­ncorporating theories of path dependence, Myles Miller and Tim Graves argue Jornada Mogollon farmers put an incredible amount of coordinated labor into the construction of earth ovens and that these features were clearly integrated into the social and ceremonial aspects of Jornada culture. Suzanne and Paul Fish summarize their work on the Hohokam agave fields and convincingly demonstrate how the locations of rockpile fields and roasting pits are tied to communal resources and social behavior. Eric Cox and colleagues expand on Hohokam earth ovens to provide a unique geoarchaeologi­ cal approach to investigating feasting “hornos” found in association with Hohokam plazas and residential sites. In the final chapter on the use of earth ovens among agriculturalists, Richard Stark details contemporary Indigenous use of

earth ovens for baking agave bloom stalks and barbacoa in San Luis Potosi, Mexico, and provides important insight into differential feature construction. The final section provides discussion of all the chapters in the volume by Paul Fish and the late Alston Thoms. Earth ovens, and more broadly hot-­rock cooking technology (including stone boiling and griddles), have been integral components of human culture for tens of thousands of years. They represent a significant technological adap­ tation parallel to the more commonly studied technologies of stone tools, ceramics, and agriculture (Thoms 1989, 2008a, 2009; Thoms et al. 2014). The chapters in this volume demonstrate the value of investigating burned rocks and earth ovens with the same analytical rigor as any other artifact or feature class.

PA RT

I

Hunter-­Gatherers of “Texas”

2 Late Paleoindian Earth Ovens in the Texas Big Bend Richard Walter and Bryon Schroeder

Human groups have used stored thermal energy in stones to increase the dietary productivity of carbohydrate-­rich floral resources throughout the Old World for as long as 30,000 calendar years (Black and Thoms 2014). In North America, the appearance of a technology that required an increase of both time and economic investment into floral resources is a defining characteristic of Archaic adaptations (Vierra 2005:2–3; Willey and Phillips 1958:107). However, the emergent use of heated stone and oven technology in the New World is not well characterized, in part due to the ubiquity and reuse of thermal features during the latter portion of the Holocene (Black and Creel 1997; Koenig et al., this volume). The discovery of deeply buried Late Paleoindian (ca. 11,000–9000 cal BP) thermal features — ​interpreted here as earth ovens — ​from the Texas Big Bend region provides some of the earliest examples of hot-­rock cooking in North America (see also Gill et al. 2021) and helps define the formational contexts of both the technology and associated subsistence regimes. This helps us to understand the adaptation and diversity of Paleoindian lifeways (Cannon and Meltzer 2008; Seebach 2011) during a period of local increasing aridity at the end of the Pleistocene, with important implications regarding the initial human adaptation to the Chihuahuan Desert as a whole. Late Paleoindian thermal features have been identified at four sites in the Big Bend region

(Figure 2.1). The first were discovered at the J. Charles Kelley site1 (41BS908; JCK henceforth) during construction monitoring in 1992 at Big Bend National Park, Chisos Basin Ranger Station (Alex 1999). JCK is in a montane oak/ pinyon/juniper environment on an alluvial fan created from erosional debris from Casa Grande Peak and Toll Mountain (Alex 1999). Beginning in 2010, the Center for Big Bend Studies (CBBS) of Sul Ross State University subsequently identified three additional Late Paleoindian sites with thermal features interpreted as earth ovens. Multiple Late Paleoindian earth ovens were discovered at the Genevieve Lykes Duncan site (41BS2615; GLD henceforth) in an unnamed arroyo and tributary of Terlingua Creek (Cloud and Mallouf 2011). Additional Late Paleo­indian earth ovens were discovered at two buried sites exposed along opposite cutbanks of Hackberry Draw, another arroyo system and tribu­ tary of Terlingua Creek. These sites, named the Searcher (41BS2621) and Juncture sites (02-390), are only 4.02 km (ca. 2.5 miles) from the GLD site. Each contains smaller, less intensively used earth ovens and very little chipped stone tools or debitage. Among the four sites, there are 21 reported radiocarbon dates from 14 thermal features. These radiocarbon ages indicate earth oven construction began in the Big Bend region by at least 11,000 cal BP. Although these data are limited, there appear to be two periods of Late 9

10

Richard Walter and Bryon Schroeder

Figure 2.1. Map of Late Paleoindian earth oven sites in the Big Bend region of Texas.

Paleoindian earth oven construction in a lower elevation transitional ecotone (GLD, Searcher, and Junction) and an intermediate period of use within a high-­elevation montane setting (JCK). While additional sites and radiocarbon ages are necessary to confirm the differential use of the Big Bend landscape during the Late Paleoindian period, they offer insights into Late Paleoindian mobility patterns because of floral resources fluctuating by elevation during ameliorating climatic conditions or as a part of stable land-­use patterns. When considered together, these data hint at a specific plant-­focused Late Paleoindian adaptation to the Chihuahuan Desert and some

of the earliest identified use of earth ovens in North America. Environmental Background

The stand-­alone term “Big Bend” refers to a 31,900 km2 (12,317 mi2) region e­ ncompassing Brewster, Presidio, and Jeff Davis counties in West Texas (Seebach 2011:1). The Big Bend is a smaller subset of the eastern Trans-­Pecos, an analytical boundary that extends from New Mexico south to the Rio Grande, and west from the Pecos River to Hudspeth County (Mallouf 2005:​220). This area is the easternmost extension of the Basin and Range physiographic



Late Paleoindian Earth Ovens in the Texas Big Bend

province, with elevations ranging from 415 m (1,362 ft) amsl (above mean sea level) at the mouth of San Francisco Canyon on the Rio Grande to ca. 2,555 m (8,383 ft) amsl at the top of Mount Livermore in the Davis Mountains (Fenne­man 1931; Powell 1998:2). It also repre­ sents the northeastern-­most portion of the Chihuahuan Desert, the largest desert in North America and the most biologically diverse in the Western Hemisphere (Wauer and Riskind 1977). Throughout the Big Bend are a diversity of environments at varied elevations with isolated econiches that include lowland riparian areas with gallery forests, upland montane oak habi­tats, grasslands, and headwaters to watersheds (Dinerstein et  al. 2000:36–37; Powell 1994, 1998). Paleoenvironmental Studies

Initial packrat midden analyses indicate that woodland xerification began sometime before 22,000 years BP and was in full swing by 11,000 years RCYBP (Wells 1976, 1985). Montane woodlands were confined to the highest elevations, and the pinyon-­juniper-oak association expanded downslope in tandem with the upslope migration and mixing of Chihuahuan Desert species from ca. 20,000–15,000 BP (Wells 1966). Independent pollen analyses also support similar, albeit earlier, trends in biotic transitions, as does Pleistocene fauna and fossil entomology (Bryant and Holloway 1985:50; Elias 1987; Elias and Van Devender 1990; Harris 2003). Overall, the increase in aridity in the Big Bend was slow but steady on a north-­to-south gradient (Van Devender 1990; Van Devender and ­Burgess 1985; Van Devender et al. 1987; Wells and Hunzicker 1976). Regarding human ecology, at a coarse scale the adaptation required to survive in the Big Bend region would have been similar from Clovis through Late Archaic periods, with the xerification of the region beginning prior to the entry of the First Peoples. During the Late Paleoindian, the focus of this chapter, vegetative communities would have been like those of today, with similar biotic econiches (Alex 1999:16).

11

Paleoindian Period in the Big Bend

The Paleoindian period (ca. 13,000–9000 cal BP) of the Texas Big Bend (Trans-­Pecos region) is characterized as “a record of numerous isolates and small sites punctuated by the much rarer large site” (Seebach 2011:38). In his region-­ wide survey of Trans-­Pecos isolated diagnostic Paleoindian points, Seebach (2011) reports only 419 projectile points, most of which are isolates. With the exclusion of the sites discussed in this paper, most known Paleoindian sites in the Big Bend region are restricted to diagnostic ­materials found as part of multioccupational surface palimpsests. The scarcity of diagnostic materials from the Trans-­Pecos in the Paleo­ indian record has led to the impression that it was a marginal landscape for early populations (See Mallouf and Seebach 2006; Seebach 2011:38 for discussion). This is in large part due to the lack of the archetypical Great Plains Paleo­ indian kill/processing sites (Seebach 2011:38). However, such a notion presupposes a more h ­ omogenous Paleoindian adaptation focused on the specialized pursuit of big game (sensu Kelly and Todd 1988). Seebach (2011:238) argues, “In regions of entirely different biotic and physiographic structure, and especially one of biomass as low as the Chihuahuan Desert, it is no surprise that such economic stances are relaxed to favor encounter-­based hunting.” Seebach also contends that the xerification of the Trans-­Pecos during the Late Pleistocene would not have supported large ungulate herds and resulted in a more encounter-­based, medium-­sized artiodactyl hunting strategy. Lithic analysis of Paleoindian diagnostics indicates a preference for local Trans-­Pecos stone materials and intensive rejuvenation of points and tools (Seebach 2011). Seebach thus concludes that Paleoindians had knowledge of the Trans-­Pecos region but “the Chihuahuan Desert may have confronted Paleoindians with problems to which they had no solutions” (2011:277). Foundationally, Seebach provides the first broad synthesis of Paleoindian occupation in the Trans-­Pecos region. However, the preva­ lence of local stone sources, as well as a high

12

Richard Walter and Bryon Schroeder

incidence of Paleoindian projectile point rejuvenation, indicates sustained local use of the region. Rather than indicate limited occupation, the small number of recovered Paleoindian diagnostics may instead be a function of a specialized adaptation to local conditions (Mallouf 1985:96; Seebach 2011). While a lack of diagnostic projectiles might suggest a place that groups avoided, as in the Great Plains, a focus on oven technology could just as easily indicate that different resources were targeted (specifically plants) in the Trans-­Pecos. Late Paleoindian Earth Ovens in the Texas Big Bend

Despite a long history of archaeological work in the Big Bend region, the Paleoindian record has been sparse and difficult to identify (Gray 2013; Seebach 2011). The earliest efforts established a chronological series of cultural units that correlate with defined stratigraphic units (Albritton and Bryan 1939; Kelley et al. 1940). This cultural/stratigraphic framework provided an age estimate for archaeological deposits rela­ tive to their stratigraphic contexts. Yet the oldest soil — ​named the Neville, presumed to be Pleisto­cene in age — ​has yet to yield Paleoindian materials (Albritton and Bryan 1939:1466). This is likely a function of taphonomy, with younger Pleistocene portions of the Neville either truncated or deeply buried (Mallouf 1985; Seebach 2011). Taphonomy, coupled with low modern population density, large tracts of private land, and widespread pothunting in the Big Bend, has had an undeniable effect on our knowledge of the first human groups in the region. Yet despite these various factors, multiple Late Paleoindian ovens from the region provide some of the earliest examples for understanding the emergence of hot-­rock technology in diverse ecotones. High-­Elevation Late Paleoindian Earth Ovens in the Chisos Mountains

In 1992, eight buried thermal features were discovered at the JCK site while monitoring the reconstruction of a parking lot drain (Alex 1999). The radiocarbon assays from two features (Feature 1 [CAMS-­12212 10225-­9695 BP; 95.4%] and

Feature 8 [CAMS-­12215 10192-­9779 BP; 95.4%]) confirmed a Late Paleoindian use of what we interpret to be earth ovens (Table 2.1). Feature 1 is a shallow rock-­lined basin (Table 2.2), but excavation was limited, and no additional cultural material was found in association with the Late Paleoindian features at JCK. Feature 8 was severely eroded, but there is a clear association between fire-­cracked rock (FCR) and carbon staining that we feel justifies its inclusion here (Alex 1999:12). The overlapping radiocarbon assays suggest use of the two ovens was contemporaneous, and median dates place them in an interval of occupation not reported from the lower elevation GLD, Searcher, and Juncture sites. The earth ovens reported from the JCK site are situated in the Chisos Mountains in an intermontane basin at 1,650 m (5,413 ft) amsl. Cooler temperatures and moister conditions support different montane floral resources such as oak/pinyon woodlands and Late Pleisto­ cene “relict populations of Arizona cypress, Arizona pine, and Douglas fir” (Alex 1999:3). Alex reports the results of a pollen analysis of ­samples collected approximately one meter north of Feature 1 (1999:​13). Pollen identified in the Late Paleo­indian stratum was a mix of xeric and montane plant assemblages (Alex 1999). Based on the higher percentages of Cheno-­am pollen compared to the lower percentages of Pinus spp., a  tentative interpretation of local xeric conditions at ca. 8800 BP followed by an increase of moisture between +7000–1000 BP was proposed (Alex 1999:16). Low-­Elevation Late Paleoindian Earth Ovens at the Paradise Draw Sites

Twelve Late Paleoindian earth ovens from the GLD, Searcher, and Juncture sites have been identified in deep arroyo cuts on Terlingua Creek, a major tributary of the Rio Grande (Figure 2.2). All three sites are situated within the desert grassland, an ecotone between the desert scrub environment of lower elevations ca. 1,067–1,219 m (3,500–4,000 ft.) amsl and the plains grasslands above ca. 1,219–1,372 m



Late Paleoindian Earth Ovens in the Texas Big Bend

13

Table 2.1. Radiocarbon Dates from Late Paleoindian Period Thermal Features in the Texas Big Bend

Region.

Radiocarbon Age BP

Calibrated Date BP (95.4%)

CAMS-12212 CAMS-12215

8890 ± 90 8880 ± 50

10228–9688 10187–9769

9985 10,008

Feature 16 Feature 17 Feature 18 Feature 20

PRI-10-128-CS-1 PRI-10-128-CS-2 Beta-286400 Beta-306727 PRI-11-014-85 PRI-11-014-85C PRI-11-014-92 ICA 18C/0605 PRI-11-014-73 Beta-306729 ICA C/0428 PRI-11-014-191 PRI-11-014-243 PRI-11-014-222 PRI-13-100-FS 448 Beta-378234

9420 ± 60 9545 ± 25 9470 ± 40 8040 ± 40 7934 ± 25 8180 ± 30 9411 ± 33 9410 ± 40 8474 ± 27 8440 ± 40 8350 ± 40 8290 ± 30 8355 ± 30 8225 ± 30 8250 ± 47 8230 ± 30

11066–10439 11074–10712 11066–10577 9080–8724 8983–8637 9270–9017 10738–10519 10746–10512 9535–9454 9535–9325 9479–9150 9422–9139 9468–9298 9397–9027 9414–9029 9398–9028

10,652 10,944 10,711 8901 8763 9111 10,636 10,636 9500 9473 9366 9303 9372 9192 9222 9197

Searcher Site

Feature 1 Feature 2

Beta-319451 Beta-324499

8140 ± 40 7840 ± 40

9265–8997 8927–8520

9078 8620

Juncture Site

Feature

PRI-12-080-02-390-1

7730 ± 30

8589–8424

8498

Site Name

Feature I.D.

Lab No.

JCK Site

Feature 1 Feature 8

Feature 1

Feature 2 Feature 10 GLD Site Feature 11 Feature 15

Median cal BP

Note: Dates calibrated with OxCal v4.4.4 Bronk Ramsey (2009): r:5 Atmospheric data from Reimer et al. (2020)

(4,000–4,500 ft) amsl. This transitional ecotone would have contained a variety of plant and ani­mal resources, as well as toolstone, making it ideal for the exploitation of multiple economic pursuits. Most of the Late Paleoindian features were exposed at the GLD site, which is situated on an interfluve that separates Terlingua Creek from Davenport Draw (Figure 2.3). The cali­ brated radiocarbon ages from nine sampled earth ovens range from ca. 11,074 to 8424 cal BP and bracket two occupational intervals: 11,074– 10,512 cal BP and 9535–8637 cal BP with nearly a millennium between occupational events (Figure 2.4). Seven of the nine recovered thermal

features date to the later interval of occupation, but excavation work focused on exposing the earliest features. Paradise Draw — ​Early Features Features 1 and 10 represent the earliest docu­ mented earth ovens in the Paradise Draw sites and are some of the earliest earth ovens in North America. Cloud et  al. (2016) describe Features 1 and 10 as shallow, rock-­lined basins (Table 2.2). The FCR in Feature 1 (Figure 2.5) exhibits differential heating, interpreted as rock rejuvenation or uneven firing and voids in the arrangement as possible foodstuff locations. The lithology of the rock used as a heating

Richard Walter and Bryon Schroeder

14

Table 2.2. Late Paleoindian Earth Oven Feature Attributes.

Centimeters

Site Name FTR #

JCK*

GLD*

X̃ cal BP

Length

1 8

9985 10,008

1

10,711

110

2

8901

10

Width

120 Not reported

Depth Below Ground Thickness Surface Fuel Wood

20

110 140

95

20

310

100

88

9

300

10636

125

100

22

310

11

9473

90

60

8

300

15

9303

105

100

10

320

16

9372

145

120

11

322

17 18 20

9192 9222 9197

Profiled in backhoe trench Eroded remnant Eroded remnant

N/A N/A N/A

1

9078

2

8620

1

8498

112

100

20

460

Profiled in backhoe trench

N/A

Searcher

Juncture

100

90

15

350

N/A N/A Saltbush (Atriplex sp.) Mesquite (Prosopis sp.) Saltbush (Atriplex sp.) Pecan (Carya illinoinesis). Saltbush (Atriplex sp.) Mesquite (Prosopis sp.) Saltbush (Atriplex sp.) Mesquite (Prosopis sp.) Creosotebush (Larrea tridentata) Mesquite (Prosopis sp.) Unidentified hardwood Cholla (Cylindropuntia sp.) Creosotebush (Larrea tridentata) Mesquite (Prosopis sp.) Unidentified hardwood Mesquite (Prosopis sp.) Creosotebush (Larrea tridentata) N/A Creosotebush (Larrea tridentata) Desert olive (Forestiera sp.) Mesquite (Prosopis sp.) Desert willow (Chilopsis linearis) Creosotebush (Larrea tridentata) Desert olive (Forestiera sp.) Mesquite (Prosopis sp.) Desert willow (Chilopsis linearis) N/A

Note: JCK = J. Charles Kelley site; GLD = Genevieve Lykes Duncan site.

ele­ment indicates it was collected locally and ­includes an exhausted slab metate (Cloud et al. 2016:34).2 Phytoliths collected from Feature 1 include taxa typical of an open and desert grassland eco­tone, a smaller frequency of herbaceous speci­mens associated with uplands, and the least common consistent with wetland commu-

nities found in Terlingua Creek. Whereas samples collected adjacent to Feature 1 are typical of a grassland ecotone and wetland, phytoliths are not present. The recovery of wetland and riparian communities exclusively from the interior of Feature 1 suggests lush, green, and moist grass taxa were used as a thermal or moisture barrier for plant baking (Ellis 1997: Table 5).



Late Paleoindian Earth Ovens in the Texas Big Bend

15

Figure 2.2. Map of Paradise Draw sites.

Feature 10 does not contain wetland phyto­ liths, and the FCR are larger and minimally fractured, indicating limited use and heat-­stress prior to feature abandonment. Macroscopically, the lithology of the rocks appears to be welded tuff, andesite, and rhyolite of varied geochemical makeup and grain size. Like Feature 1, these stones were collected from secondary stream-­ load deposits of Terlingua Creek or Davenport Draw. Paradise Draw — ​Younger Features A total of 10 ovens cluster in the younger Late Paleoindian interval of use in Paradise Draw sites. Seven of the 10 were discovered at the

GLD site, two are from the Searcher site, and a single feature was discovered at the Juncture site (Table 2.2).3 The seven thermal features at the GLD site (Figure 2.3, Table 2.2) encompass a range of morphological variability; Feature 2 is the best preserved; Features 18 and 20 are both eroded and disarticulated FCR scatters at best. The exposure of Feature 11 is limited to a profile cut in the sidewall of a backhoe trench that has not been formally excavated. Features 15, 16, and 17 were exposed in sampled trench walls and fully excavated in the summer of 2020. The excellent state of preservation of Feature 2 elucidates oven technology in the later interval of Late Paleoindian.

16

Richard Walter and Bryon Schroeder

Figure 2.3. Late Paleoindian earth ovens at the GLD site.

Feature 2 is a shallow, rock-­lined basin (Figure 2.6). Several peripheral pieces of FCR were angled toward the feature interior, suggestive of intentional placement during feature construction. One was an exhausted metate fragment.

The majority of the FCR did not exhibit signs of intensive reuse, and only a few were severely heat-­fractured in situ. Many of the FCR were protruding from a three-­centimeter-thick layer of oxidized clay. The boundary between the



Late Paleoindian Earth Ovens in the Texas Big Bend

17

Figure 2.4. Oxcal Version 4.4 multiple plot of Late Paleoindian period thermal features in the Texas Big Bend region (GLD = Genevieve Lykes Duncan; JCK = J. Charles Kelly Site; SCH = Searcher Site; JNT = Juncture).

oxidized clay and the underlying charcoal was abrupt. While the clay was very compact, the underlying feature fill was loose. A large tabular rock was placed directly over the charcoal bed and may have served as a griddle. Macrobotanical analysis indicated a wide variety of woods were used for fuel including creosote bush, saltbush, walnut, pecan, mesquite, and an unknown member of the buckthorn family. The feature matrix also contained

uncharred seeds, bone fragments, insect chitin, and snail shells, all of which likely reflect the modern biotic community introduced into the feature via bioturbation based on the presence of worm casts, roots, and rootlets (Cloud et al. 2016; Puseman et al. 2013:14). Additional materials may have been introduced by the shrinking and expanding of the clay-­rich sediments. Phytolith analysis was conducted within and adjacent to Feature 2. Like Feature 1, phytoliths

Figure 2.5. Location of Features 1 and 2 at GLD exposed in the walls of the arroyo; inset shows Feature 1 during excavation.

Figure 2.6. Feature 2 as an example of the Late Paleoindian thermal features at GLD showing clay lens, burned rock, and dense charcoal bed.



Late Paleoindian Earth Ovens in the Texas Big Bend

indicative of succulents and grasses were the most common, with a lesser number of those indicative of cacti, gourds, palms, and woody species such as oak. Features 15, 16, and 17 were found in a backhoe trench at the same elevation below the modern ground surface. The overlap in radiocarbon assays from each feature was initially thought to represent a Paleo/Archaic transitional living surface with multiple contemporaneous hearth-­like features. Excavation of all three features determined Feature 15 is a large, rock-­filled oven with a thick bed of charcoal and that Features 16 and 17 are outer discard from previous cooking episodes (Koenig et al., this volume). Considered together, Features 15–17 provide the earliest and best example of a transitional Paleo/Archaic earth oven facility in the Big Bend region. The additional Late Paleoindian ovens identified at the Searcher site indicate a similar construction method. Feature 1 was found eroding from a cutbank in Hackberry Draw and was salvaged before it eroded. The terrace overburden was removed and ca. 50 percent of the oven was intact with charcoal flecks and carbon-­stained sediment overlying two courses of FCR. Like Feature 2 at GLD, there were four slabs placed at or near the edge, oriented at an angle toward the center of the oven remnant. Macrobotanical analysis of samples taken adjacent to Feature 1 indicate a pollen record typical of Chihuahuan desert scrub. Feature 2 at Searcher was found in a backhoe trench. It also had five slabs placed at the edge of a prepared shallow basin, with cobble-­ sized pieces of FCR placed over the slabs. Charcoal was not found below the slabs. GLD Rock Sort Studies of the FCR recovered in an adjacent earth oven facility provide an abundant artifact to quantify the reuse of these dynamic facilities. From the analysis we assume that as an oven was reused through time, the size of rock was reduced because larger stone heating elements were reused and broken down. Quantifying the size of the rock at a thermal feature can provide

19

data used to interpret both the efficiency of the technology and patterning of behavior. The rock sort data is only available for thermal features excavated at the GLD site and is presented in Table 2.3. Features 1 and 10 are the two earliest excavated ovens at the GLD site and, like the phyto­ lith data, the rock sort indicates an opposite pattern of use at each feature. The majority of FCR in Feature 1 is ≤ 11 cm (4 in) in size, whereas the majority of FCR in Feature 10 is ≥ 11 cm (4 in). Functionally, this seems to indicate Features 1 and 10 would have different thermal properties, with the larger stones in Feature 10 retaining heat better than Feature 1. The differences in rock sizes between discrete thermal features located only six meters apart and those found at similar elevation suggests they had different cooking functions. Considered with the phytoliths, these early features represent a technology that was fully understood and harnessed in the Big Bend region in the Paleo­ indian period but not reused to the same degree as later examples. The rock sort data from Features 15–17 are consistent with an incipient earth oven facility (Feature 15) representing a pit feature with two adjacent discard zones (Features 16 and 17). Features 15–17 contain double the amount of burned rock as Feature 1 (the next largest feature) and may represent a period of increased population and or reduced mobility. When contrasted with the other thermal features reported here, Features 15–17 represent the clearest evidence for pit oven reuse, but, interestingly, this pattern is currently not seen at other sites. Discussion

There are 21 reported radiocarbon dates from 14 thermal features in the Big Bend region that document the earliest use of earth ovens in the Trans-­Pecos; two of the thermal features are among the earliest earth ovens and hot-­rock cooking in the New World (Table 2.1 and Figure 2.4). Thoms (2003:89) places the emergence of hot-­rock cooking at the beginning of the Holocene epoch, around 10,000 years ago. He then reviews thermal features from Paleoindian sites

Richard Walter and Bryon Schroeder

20

Table 2.3. Rock Sort Data for GLD Late Paleoindian Earth Oven Features.

FCR size classes < 7.5 cm Feature # Material Type

1

2

10

15

16

17 18 20

Rhyolite Tuff Chert Volcanic Other Total Rhyolite Volcanic Other Total Rhyolite Tuff Basalt Volcanic Other Total Rhyolite Volcanic Other Basalt Total Rhyolite Claystone Volcanic Other Total Rhyolite Total Volcanic Other Total Basalt Total

7.5–11 cm

11–15 cm

Count

Mass (kg)

Count

Mass (kg)

Count

25 — 1 21 47 3 4 7 5 — — 2 7 29 23 2 54 — 1 — 1 1 1 1 1 — —

2.11 — 0.07 1.69 3.87 0.37 0.45 0.81 0.26 — — 0.058 0.32 2.65 1.39 0.03 4.08 — 0.07 — 0.07 0.07 0.07 0.13 0.13 — —

12 — — 7 19 12 3 15 4 — — 4 8 46 17 — 63 3 — 1 4 1 1 — — — —

3.00 — — 1.79 4.79 3.67 0.53 4.20 1.40 — — 2.65 4.05 11.96 4.57 — 16.528 0.63 — 0.09 0.72 0.33 0.33 — — — —

6 1 — 2 9 7 9 16 9 1 — 7 17 14 2 — 16 2 — — 2 1 1 — — — —

and concludes that these early hunter-­gatherers “made little use of cook stones.” Yu (2006, citing Mabry 1998:107–108) reports four Paleoindian earth ovens from the Sonoran Desert basin and range region and argues for early intensification in the basin but does not report associated dates. Both Koenig and colleagues (this volume) and Miller and Graves (this volume) report early radiocarbon ages associated with hot-­rock cooking features from the western and eastern edges of the Trans-­Pecos region. Bous-

Mass (kg)

>15 cm Count

4.25 4 0.9 1 — — 0.57 3 5.72 8 3.90 2 6.82 7 10.71 9 6.38 7 0.47 — — 1 5.58 13 12.43 21 7.92 7 0.92 1 — — 8.841 8 1.75 1 — — — — 1.75 1 1.20 1 1.20 1 — — — — — 1 — 1

Mass (kg)

Total Count

6.00 47 1 2 — 1 3.00 33 10.00 83 2.40 24 7.10 23 9.50 47 11.40 25 — 1 0.90 1 22.80 26 35.10 53 7.59 96 0.90 43 — 2 8.485 141 1.3 6 — 1 — 1 1.3 8 1.00 4 1.00 4 — 1 — 1 1.10 1 1.10 1

Mass (kg)

15.36 1.9 0.07 7.05 24.38 10.34 14.89 25.23 19.44 0.47 0.90 31.09 51.90 30.11 7.79 0.03 37.93 3.68 0.07 0.09 3.84 2.60 2.6 0.13 0.13 1.10 1.10

man (1998) reports similar-­aged thermal features and chipped stone tool assemblages from the Late Paleoindian occupations of the multi­ component Wilson-­L eonard site in Central Texas (Figure 2.7; Guy 1998:1135). The critical difference between these two sites is the frequency and size of thermal features, with GLD representing slightly earlier and more prominent examples of hot-­rock cooking. These Late Paleoindian uses of hot-­rock cooking, contrasted with similarly aged Late Paleoindian site



Late Paleoindian Earth Ovens in the Texas Big Bend

21

Figure 2.7. Perforator tip and projectile point base recovered from the Late Paleoindian deposits at the GLD site. Both are similar to artifacts reported from the Wilson-­Leonard site (Bousman 1998:Figure 8-­3c, Figure 8-­10a, b).

assemblages from the New Mexico region, are more consistent with a Plains hunting adaptation and further suggest that the emergent use of hot-­rock cooking is not solely a product of xeric environments (Blaine et al. 2017; Hill and Holliday 2011; Vierra et al. 2012). The rock ovens from the Big Bend region, although limited, add significantly to our understanding of the emergence and continued use of this thermal and subsistence technology. There appear to be two periods of Late Paleo­ indian earth oven construction in a lower-­ elevation transitional ecotone (GLD, Searcher, and Junction) and an intermediate period of use within one high-­elevation montane setting (JCK). While additional sites and radiocarbon

ages are necessary to confirm the differential use of the Big Bend landscape during the Late Paleoindian period, those described here offer insights into Late Paleoindian transhumant patterns due to the fluctuation of floral resources by elevation during ameliorating climatic conditions or as a part of stable land-­use patterns. The identification of charcoal and pollen analyses from the Paradise Draw sites indicate a range of plants diagnostic of more xeric and riparian flora communities; the discovery of hardwoods such as pecan may be a result of the rejuvenation of a tool shaft rather than an environmental signal (Cloud et al. 2016). Also recovered from these sites were microinvertebrates that indicate the presence of ram’s horn

22

Richard Walter and Bryon Schroeder

snail (Gyraulus parvus) and Mexico Ambersnail (Succinea luteola), species that live in or near riparian environments. The recovered earth oven from the Paradise Draw sites ­covers a large timespan with a gap between the earliest and the latest use. Current efforts are underway to refine our understanding of the environmental conditions associated with each period of use at the Paradise Draw sites. However, when considered with the montane oven remnants recovered at JCK, there appears to be a pattern of transhumance that brought groups out of the Paradise Draw and into the Chisos Basin. Further research needs to refine the conditions from which this use arose. The reported δ13C values of soil organic matter in the paleosol containing the earth ovens at the GLD site re­inforce such an interpretation. These data provide the relative proportions of C3 (cool season and trees) and C4 plants (warm-­season perennial grasses and herbaceous plants) that contribute to the formation of organic soils. Cloud and colleagues (2016:31) suggest that the “vege­tation that contributed organic matter to the paleosol appears to have shifted significantly during the period of its formation. The bottom was derived from C3 plants (ca. 70 percent), whereas the middle of the soil, during the Paleo­indian occupation, diminished to 41 percent in favor of warm-season grasses and perennial plants.” Carbon isotopes taken from soil organic matter at the top of the paleosol shifted back to cool-season C3 plants. This shift toward warm-­season vegetation in the middle of the paleosol may indicate that somewhat drier conditions prevailed during the Paleo­ indian occupation. Thus, Cloud and colleagues (2016:65) conclude that “many constituents of the modern Chihuahuan Desert were present at this time.” Considered with the reported macrobotanical findings from the JCK site, these data indicate Late Paleoindian foragers of the region commanded a technology that enabled them to exploit the xeric conditions. The early emergence of earth ovens during the Late Paleoindian in the Big Bend offers a probable developmental history for the technology (Thoms 2008a:124, Figure 3c for one

plausible projection). Thoms (2009:573) p ­ osits, “Continent-­wide increases in use of rock heating elements during the Holocene resulted primarily from population packing and related intensification of broad-­spectrum foraging.” Under such a scenario, the use of ovens marks a transition to previously available but unused or under-­used foods in the context of increasing population (Thoms 2008a:123). Given these expectations, human groups first use fire for warmth, followed by coals for cooking. Then, as new foods are utilized, early variations of rock-­ less ovens precede more formal hot-­rock ovens. Except for Feature 15 at GLD, the early ovens presented here are small, with little evidence of reuse compared to the much larger burned-­rock features from the late Holocene (Koenig et al., this volume; Lodge, this volume; McAuliffe et al., this volume). Small fragments of charred animal bone and baked xeric species were recovered from the Late Paleoindian ovens (these ovens were not used solely for baking floral resources [Dering 1999; Thies 1990]). However, rock sort data indicate differing construction suggestive of a specific use for each of the recovered thermal features. Given the diversity presented in the early features of the Big Bend region, we propose that early earth ovens were used for a variety of tasks. If intensification of underused resources is a factor for their emergence, it is possible the early use arose in the context of the need for Paleo­indian groups to replenish fiber technologies under increasingly xeric conditions. In such a scenario, hot rock is needed to prepare the appropriate material while other floral and faunal resources are cooked (cf. Cloud et al. 2016; Thies 1990). Such exaptation of the burned-­ rock technology from generalized ovens used to process plant and small game resources to a technology that led to floral intensification in the late Holocene helps account for the low presence of Paleoindian stone diagnostics from the region (Seebach 2011). It is clear from the ubiquity of large, burned-­rock middens across the landscape that oven use became specialized through the Holocene as hunter-­gatherer groups relied more



Late Paleoindian Earth Ovens in the Texas Big Bend

heavily on xeric floral species as a food source and mesic conditions became more entrenched (Black and Creel 1997; Black and Thoms 2014; Morgan 2015). The reported Late Paleoindian ovens do not represent the initial use of the technology, but considered with the suite of Paleo­indian materials recovered from the region, they suggest the presence of early, generalized foragers who utilized a technology that became critical for the adaptation to xeric conditions of the Chihuahuan Desert. Conclusion

The Late Paleoindian earth ovens recovered from montane oak-­juniper-pine woodlands in the Chisos Mountains and a lower-­elevation transitional assemblage of vegetation types typi­cal of the Chihuahuan Desert scrubland and Desert Grassland communities are the first reported from the region (Powell 1994:14; 1998:​ 8–9). In fact, they are among the earliest earth ovens reported from North America (Thoms

23

2009). We argue they represent a generalized technology that became increasingly specialized through the Holocene. Future studies will focus on detailing environmental conditions, the patterned use of the landscape, as well as detailed macro- and microbotanical analyses to better understand the context in which this pervasive and effective technology developed. In a discussion of New Mexico Paleoindian adaptations, Hill and Holliday (2011:16) suggest, “If we want to understand the true nature of the adaptive variability of foragers, we need to focus our attention away from research areas that provide foragers with a homogenous environment, such as the Great Plains, and explore the archaeological record in environmentally diverse settings.” As Paleoindian research progresses in the Big Bend region, the heterogenous ecotones in a Basin and Range environment will provide additional insights with important implications for understanding the diversity of early human adaptations across the continent.

Notes 1. Named in homage to the pioneering Southwest

archaeologist J. Charles Kelly (Alex 1999). 2. This groundstone artifact could be one of the earliest pieces of groundstone in North America.

3. Unfortunately, shortly after Feature 1 at Juncture

(32 m north of the Searcher site) was exposed and sampled for radiocarbon, heavy flooding washed it away.

3 Central Texas Plant Baking Richard McAuliffe, R aymond Mauldin, and Stephen L. Black

By 9,000 years ago, hunter-­gatherers in the central and southwestern parts of Texas had begun to routinely use heated rocks to bake food plants in the layered pit-­cooking arrangements known as earth ovens (Black and Thoms 2014). Regional radiocarbon dates show continuous use of this technology from early Holocene adoption 9,000 years ago — ​or earlier  — ​right through the end of the prehistoric era 500 years ago and beyond into the nineteenth century. Pervasive in the regional archaeological record, earth oven features have been a focus of archaeological inquiry for over a century (see Black et al. 1997; Kelley and Campbell 1942; Pearce 1919, 1932). This chapter synthesizes archaeological knowledge about these features in Central Texas, emphasizing what has been learned over the last two decades. Our focus is on burned rock middens (BRMs), large accumulations of thermally fractured cooking stones and charred earth, found across Central Texas (Figure 3.1a). These BRMs are indicative of persistent reuse of locations at times of plant resource intensi­ fication. However, we also incorporate data from smaller, standalone hot-­rock cooking features (Figure 3.1b), referred to simply as individual ovens (IOs), that likely represent earth oven heating elements analogous to those documented within the central pits of BRMs (Black and Thoms 2014; Black 2003; Walter and Schroeder, this volume; Wohlgemuth et al., this volume). Using radiocarbon-­based summed

probability plots, we suggest that BRMs and IOs have different patterns of use. IOs first appeared in Central Texas over 9,000 years ago, with several periods of intensive use. BRMs occur later in time, with intensive use peaking between 1300 and 600 cal BP. Focusing on 45 recently excavated, well-­documented BRM and IO sites, we provide a review of cooking technology, subsistence, and associated behavioral practices for ovens, then consider the potential role of Central Texas ovens in social and ritual life. Setting and Research Background

Our Central Texas study area comprises 31 Texas counties on and adjacent to the Edwards Plateau, a Cretaceous limestone expanse bounded on the east by the Balcones Escarpment ecotone and on the southwest by the Lower Pecos Canyonlands (Figure 3.2; Black et al. 1997). Natural springs throughout the area provide the base flow for south- and southeast-­flowing watercourses including the Colorado, Guadalupe, San Antonio, and Nueces Rivers. The incised drainages form extensive canyonlands in the eastern and southern Edwards Plateau, a scenic karstic topography dubbed the “Texas Hill Country.” The climate is on the just-­wet side of desert, and the dearth of dry rockshelters means that preserved ­organics are limited to charred plant remains and bones. The region is renowned for its abundant high-­quality chert resources used for tool making and for its endless supply of limestone for hot-­rock cooking. 24



Central Texas Plant Baking

25

Figure 3.1. Central Texas earth oven features: (a) exposed burned rock midden (BRM) at the

Higgins site (41BX228) with three individual oven beds, one in the central pit of the BRM and two overlying the outer edges of the BRM (Black et al. 1998b:100); (b) circular individual oven bed (Feature 7) and associated oven cleanout debris (Feature 8) at the Honey Creek site (41MS32; Black et al. 1997:119).

Despite the thin soils atop its limestone uplands, the region is home to broad oak and juniper savannas and narrow riparian woodlands that provided the abundant plants and animals that served as sources of foods, fuel, fiber, and materials for making tools and building temporary shelters (Collins 2004; Riskind and Diamond 1988). Black and Creel (1997:295, 288) characterize the “classic” Central Texas BRM as “a circular, mounded accumulation some 10–25 m across having a basic annular (concentric) morphology — ​a dense ring of rocks surrounding a distinct center” within which “oven after oven was built.” One of the earliest archaeological investigations of Central Texas BRMs, noting the presence of mussel shell and bison bone, assumed these features were principally used for roasting faunal resources (Kelley and Campbell 1942:320). However, ethnographic accounts and overviews (Buskirk 1987:169–174; Castetter et al. 1938; Castetter and Opler 1936; Ellis and Black 1997; Thoms 1989; Wandsnider 1997), actualistic and ethnoarchaeologcial research (Dering 1999; Leach et  al. 2005; Stark 2002),

and archaeological observations (Black et  al. 1998a; Black and Thoms 2014) provide a clear picture of the construction and use of these features. In most cases, these studies suggest that carbohydrate-­rich plants, surrounded by moist packing material, were laid on beds of heated rocks and coals then covered with earth. After baking, the oven was opened, and the food removed. The BRMs of Central Texas show that groups returned to the same earth oven facilities over hundreds or thousands of years (Black and Creel 1997:271–280; Boyd et al. 2004). This pattern of reuse resulted in massive accumulations of fire cracked rocks that were discarded as the fragments became smaller and less heat retentive than the larger rocks favored for earth oven construction (Mauldin and Tomka 2010). Documenting Temporal Patterns of Earth Oven Use

Establishing when these earth ovens first appeared, and their greatest intensity of use, has long been of interest to Central Texas researchers. Use of earth ovens was traditionally thought to have begun sometime in the Archaic, based

26

Richard McAuliffe, R aymond Mauldin, and Stephen L. Bl ack

Figure 3.2. Texas, showing general Edwards Plateau boundary (bolded black line) and the

­counties included in this study.

primarily on the recovery of temporally diagnostic artifacts in feature fill. Weir (1976) suggested a 5000 cal BP start date, with peak use occurring between 2800 and 1800 cal BP. Prewitt (1981b, 1985), using both artifacts and a small number of radiocarbon dates, opted for a similar start date (5000 RCYBP) but suggested peak use was between 4600 and 4000 cal BP and that BRMs were not used after 2250 cal BP (1981b). Throughout the 1980s and into the 1990s, most researchers suggested that BRMs were principally used in the Middle and Late Archaic (Black 1989; Collins 1991; Houk and Lohse 1993; Johnson 1995; Prewitt 1991), though radiocarbon dating hinted at both earlier (Black and Karbula 1998; Prewitt 1981a) and later oven use (Lukowski 1987; Goode 1991; Treece 1993). Black and Creel (1997) presented the first regional compilation of radiocarbon dates on

these features for the Edwards Plateau area. Focusing on BRMs and using publications from 1974 through 1997, they identified 141 radio­ carbon dates from 35 ovens. The data are compiled and presented by Decker (1997). Contrary to previous assumptions, Black and Creel (1997:​ Figures 133–136) showed that most BRM dates were, in fact, clustered in the Late Prehistoric period (ca. 1200–500 cal BP). The concentration of Late Prehistoric dates, however, was open to question because roughly half of the dates that Black and Creel used were based on conventional liquid scintillation radiocarbon methods. The large charcoal sample weights required in conventional dating are unlikely to survive for long periods of time. The apparent pattern, then, could be a product of differential preservation (Black and Creel 1997:273–80). While several subsequent studies relying exclusively



Central Texas Plant Baking

27

Figure 3.3. The study area, which encompasses parts of 31 Texas counties on and near the

Edwards Plateau. The number of radiocarbon dates used in this study is shown by county (see Tables 3.1 and 3.2).

on AMS supported the dominance of Late Prehistoric dates on these large earth ovens accumulations (e.g., Mauldin et  al. 2003; Weston and Mauldin 2003), these studies focused on a single county on the northern edge of the Edwards Plateau and therefore lacked the spatial scale of the Black and Creel synthesis. Nevertheless, these studies suggested that hot-rock cooking, long considered a “hallmark of the Archaic” in Central Texas archaeology (Collins 2004:119), peaked in the Late Prehistoric period sometime after 1150 cal BP. For our synthesis, radiocarbon dates were compiled from earth oven features on, and immediately adjacent to, the Edwards Plateau. We began with the earlier Black and Creel (1997; Decker 1997) synthesis, as well as dates presented by Weston and Mauldin (2003; see also Mauldin et al. 2003). We supplemented these with dates published over the last 20 years,

limiting our samples to radiocarbon dates run on carbonized plants and bone, while excluding dates from shell and humate samples. Ulti­ mately, we assembled 376 radiocarbon dates from 73 sites reported between 1974 and 2015. Just over 100 BRMs, represented here by 218 radiocarbon dates (Table 3.1), and 86 IOs, represented by 158 dates (Table 3.2), were gathered from 31 Central Texas counties (Figure 3.3). This set of dates is not comprehensive. There are certainly dated oven features within the sampled counties (Figure 3.3) that were missed. In addition, the sample of dated features is a small subset of excavated Central Texas ovens, the vast majority of which have not been radiocarbon dated. Many features seem to lack sufficient organics, even with the use of AMS dating methods. Systemic factors such as baking pit clean out following food preparation, taphonomic impacts, the palimpsest nature of

Table 3.1. Compiled Radiocarbon Dates for Central Texas Burned Rock Midden

(BRM) Features.

Site

41BL233 41BL598 41BL608 41BL743 41BR228 41BR246 41BR250 41BR253 41BR392 41BR420 41BR433 41BR441 41BR473 41BR474 41BR478 41BR492 41BR493 41BR522 41BR65 41BR87 41BX1 41BX1228 41CC112 41CC167 41CV1027 41CV1195 41CV124 41CV1378 41CV413 41CV413 41CV594 41CV595 41ED28 41HY160 41HY209 41HY209 41KM69 41KR229 41KR621 41ME29 41MI77 41MK8 41MK9 41MS32 41MS69 41RN163 41RN169 41RN3 41SU2 41TV742 41UV45 41UV47 41UV48 41UV86 41WM1126 41WM235 Totals:

No. of Dates

6 3 2 2 4 2 1 4 3 2 1 1 2 2 2 4 3 2 3 2 1 1 13 1 4 2 4 7 4 6 4 9 8 1 6 1 1 14 7 2 2 2 8 13 1 2 9 9 4 1 2 1 3 8 5 1 218

No. of AMS Dates Reference

6 3 2 2 4 2 1 4 3 2 1 1 2 2 2 4 3 2 3 2 0 0 0 0 4 2 4 7 4 6 4 7 8 1 3 1 1 0 7 2 0 1 8 13 1 0 0 0 0 0 0 0 0 8 5 0 148

Decker 1997 Decker 1997 Decker 1997 Decker 1997 Mauldin et al. 2003 Mauldin et al. 2003 Mauldin et al. 2003 Mauldin et al. 2003 Weston and Mauldin 2003 Mauldin et al. 2003 Mauldin et al. 2003 Mauldin et al. 2003 Mauldin et al. 2003 Mauldin et al. 2003 Mauldin et al. 2003 Mauldin et al. 2003 Mauldin et al. 2003 Weston and Mauldin 2003 Mauldin et al. 2003 Mauldin et al. 2003 Decker 1997 Decker 1997 Decker 1997 Decker 1997 Decker 1997 Decker 1997 Decker 1997 Boyd et al. 2014 Mehalchick et al. 2002 Quigg et al. 2011 Decker 1997 Mehalchick et al. 2004 Quigg et al. 2008 Haefner 2011 Decker 1997 Ricklis and Collins 1994 Thompson et al. 2012 Decker 1997 Houk et al. 2008 Decker 1997 Johnson 2009 Decker 1997 Decker 1997 Decker 1997 Quigg et al. 2015 Decker 1997 Decker 1997 Decker 1997 Decker 1997 Coffman et al. 1986 Decker 1997 Decker 1997 Decker 1997 Decker 1997 Carpenter et al. 2013 Stafford 1998



Central Texas Plant Baking

29

Table 3.2. Compiled Radiocarbon Dates for Central Texas Individual Oven (IO) Features.

Site

No. of Dates

41BL1214 41BL278 41BL288 41BR87 41CV413 41CV595 41HY160 41HY163 41HY165 41HY202 41HY209 41KM226 41KM69 41KR621 41LM50 41MS69 41SS164 41TV1364 41TV1667 41TV2125 41TV2265 41TV410 41TV441 41TV461 41TV540 41TV742 41WM1010 41WM235 41WM53 Totals:

4 2 1 1 2 2 3 2 7 5 3 8 7 15 2 9 1 2 1 17 2 1 4 1 6 4 21 22 3 158

No. of AMS Dates Reference

4 2 1 1 2 2 3 2 7 4 0 8 7 15 2 9 1 2 1 17 2 1 4 0 6 1 21 20 0 145

BRMs, and sampling methodology all influence the pattern of available dates (Mehalchick et al. 2004:132). Nevertheless, the compiled datasets in Tables 3.1 and 3.2, while not exhaustive, are extensive, involving multiple sites and researchers over the last 45 years. In addition, AMS dates now make up 78 percent of the database. We focus on individual radiocarbon dates rather than features. For the larger, repeatedly used BRMs, multiple dates often reveal different

Griffith and Kibler 2005 Quigg and Frederick 2015 Ringstaff 2004 Mauldin et al. 2003 Quigg et al. 2011 Mehalchick et al. 2004 Nickels and Bousman 2010 Lohse 2011 Leezer 2013 Ricklis and Collins 1994 Ricklis and Collins 1994 S. Carpenter et al. 2012 Thompson et al. 2012 Houk et al. 2008 Quigg et al. 2014 Quigg et al. 2015 Bonine et al. 2008 Nash 2008 R. Jones and Leffler 2008 Karbula et al. 2011 Brownlow 2007 Figueroa et al. 2011 Karbula 2003 Thurmond 1982 Figueroa et al. 2011 Coffman et al. 1986 Dixon and Rogers 2006 Stafford 1998 Decker 1997

periods of use spanning centuries or millennia. However, several cases in the oven category have multiple dates and likely represent only a few use episodes. While cases of multiple, overlapping dates are rare, where they do occur the period will be disproportionately represented. An extreme example of this is Feature 181 from the Wilson-­L eonard site — ​ a 9,000-­year-old oven — ​with nine overlapping dates (Stafford 1998). This oven was clearly used for a brief

30

Richard McAuliffe, R aymond Mauldin, and Stephen L. Bl ack

Figure 3.4. Summed probability distribution for 376 radiocarbon dates on oven features within

the study area. The line represents a 100-­year running mean. The gray band represents the results of 100 Monte Carlo simulations done on the distribution assuming an exponential model. Periods of greater than and less than expected frequencies are highlighted by red (high) and blue (low) shading.

­ eriod, possibly a single event, but the use inp tensity will be overrepresented in our plots. The 376 dates were used to construct the summed probability distribution (SPD) plots presented in Figures 3.4 and 3.5. Radiocarbon SPD plots are often used as an indirect measure of relative population, with changes in the probability curve interpreted as changes in population levels (e.g., Crema et al. 2016; see also Freeman et al. 2018; Rick 1987). The under­ lying idea is that larger populations generate more waste (e.g., charcoal, animal bone, floral remains) for archaeologists to sample. While issues with taphonomy, sampling, calibration, and research focus exist, the use of SPD curves of dates in population estimates has proven use-

ful in numerous studies (e.g., Bevan et al. 2017; Robinson et al. 2019; Shennan et al. 2013; Timpson et al. 2014; Williams 2012). Our use of SPD curves has a more limited focus. While taphonomic and sampling issues are certainly still in play, our primary assumption is that a general relationship exists between increases and decreases in the probability curve of radiocarbon dates in our feature data set and the frequency of oven feature use. Figure 3.4 presents the SPD curve for dates from Tables 3.1 and 3.2. The plot was generated in R using the rcarbon package (Crema and Bevan 2019). Calibration was done using the IntCal13 calibration curve and dates were aggregated and plotted from 100 to 10,000 BP. The

Figure 3.5. Summed probability distribution of radiocarbon dates by general size class for ovens.

Top plot uses 218 dates from features identified as BRMs. Bottom plot uses the 158 dates on IOs. As before, the line represents a 100-­year running mean. The gray band represents the results of 100 Monte Carlo simulations done on the distribution assuming an exponential model. Periods of greater than and less than expected frequencies are highlighted by red (high) and blue (low) shading.

32

Richard McAuliffe, R aymond Mauldin, and Stephen L. Bl ack

line represents a 100-­year running mean. Note that an advantage of this package is the ability to generate, through simulation, expectations based on theoretical models. Comparison of the actual SPD curve against the simulations allows identification of significant deviations (Shennan et al. 2013). The gray band in Figure 3.4, then, was generated by 100 simulations assuming that the actual curve fits an exponential model. We chose an exponential model for two reasons. First, it is a close fit to the actual distribution. In addition, an exponential model provides a rough approximation of taphonomic decay (Surovell and Brantingham 2007). The gray band shown in Figure 3.4 is similar to a 95 percent confidence interval (see Crema and Bevan 2019; also Shennan et al. 2013; Timpson et al. 2014). High and low deviations outside of that confidence interval are highlighted by red(high) and blue-(low) shaded bands. These deviations are unlikely to be random noise or results of the effects of calibration. Rather, they likely reflect shifts in oven-­use frequency in Central Texas. Figure 3.4 shows multiple periods of greater-­ than-expected use of earth ovens, identified by red shading. Here, we focus on the three longer periods. The first, from 9300 to 8500 cal BP, coincides with feature use at both Wilson-­Leonard (41WM235) and the Berdoll site (41TV2125). The magnitude of this positive deviation is certainly influenced by our decision not to average dates at a feature level. For both sites, researchers submitted multiple dates from features, recognizing the importance of securely dating these early contexts (see Collins 1998; Karbula et al. 2011; Stafford 1998). At a feature level, nine features are represented in our sample during this time, suggesting that oven technology was well established at the beginning of the Early Archaic period. A second period of greater-­than-expected use occurs between 6250 and 5650 cal BP. The period encompasses the Calf Creek horizon, a series of assemblages that may reflect subsistence focused on bison (Collins 2004; Johnson and Goode 1994). Lohse and colleagues (Lohse et al. 2014a, b), relying on direct dates on bison,

have argued that these animals were present between 5955 and 5815 cal BP in Central Texas. Yet, Collins suggests there was “relatively little use of hot-­rock appliances . . . during the Bell-­AndiceCalf Creek style interval” (Collins 2004:125; see also Acuña 2006). While the Calf Creek interval occurs in the middle of a spike in oven use, Collins is correct: if we focus on BRMs, only a ­single BRM from site 41CV413 (Mehalchick et al. 2002) is represented in this second devi­ ation. Rather than larger BRMs, this second spike is composed mainly of IO dates from several sites (e.g., Figueroa et al. 2011; Houk et al. 2008; Quigg et al. 2015). The final large positive deviation occurs between 1300 and 600 cal BP. This encompasses much of the initial Late Prehistoric or Austin interval. The peak is formed by over 150 dates from a variety of features on numerous sites (e.g., Black and Creel 1997; Boyd et  al. 2014; Mauldin et  al. 2003; Weston and Mauldin 2003). Unlike earlier periods, this third spike is dominated by BRM dates, over 75 percent of which are from BRM contexts. This suggests a dramatic increase in the frequency of use and reuse at a given location, a pattern that may reflect lower mobility during this period, perhaps constrained by population growth. Figure 3.4 also indicates seven short intervals, shaded in blue, where the observed SPD pattern falls below expectations. The initial period of less-­than-expected use occurs at around 6600 cal BP, a time with no feature dates. The next period begins at 4400 cal BP and is one of five low-­frequency intervals in the Late Archaic (4400–1250 cal BP), a chronological period that lacks any positive deviations. This lower-­ than-expected use frequency is not consistent with earlier interpretations (see Prewitt 1981b, 1985; Weir 1976). The last period of lower-­ than-expected use occurs near the end of the prehistoric sequence, falling between 450 and 100 cal BP. This time frame covers some of the Late Prehistoric Toyah interval — ​ca. 650 to 300 cal BP (Prewitt 1981b) — ​a time when bison were again available and Edward’s Plateau foragers are believed to have embraced a more mobile existence to focus on these animals (Collins



Central Texas Plant Baking

2004). However, significant declines late in many chronological sequences appear to be common in SPD plots that transition into the historic period (e.g., Oh et al. 2017; Zahid et al. 2016). Several methodological causes have been suggested for these late declines, including a boundary or edge effect as dates approach the end of the sequence, and calibration issues with more recent dates (see Thorndycraft and Benito 2006; Williams 2012). To consider these patterns in more detail, we present plots of BRMs and IOs in separate SPD analyses (Figure 3.5), using the same procedures discussed previously for Figure 3.4. Sample sizes are reduced in these plots. Consequently, the patterns produced may change significantly with more dates (see Michczyńska and Pazdur 2004). While these patterns should be regarded as provisional, in Figure 3.5 IOs exclusively account for the first two periods of higher-­than-expected use seen in Figure 3.4. In addition, they make a significant contribution to the ca. 1300–650 cal BP deviation, with a spike seen near the end of the sequence. The larger BRM facilities are infrequent early, essentially being used after 6000 cal BP. As we suggested in our discussion of Figure 3.4, while present from 6000 cal BP on, BRM dates peak in the initial Late Prehistoric interval. Note also that a significant decline late in the distribution of BRMs is not reflected in the IO features. The IO pattern falls within the expected range. While large, repeatedly used earth-­oven complexes (BRMs) were essentially abandoned in the Late Prehistoric Toyah interval (Collins 2004:125), hot-­rock cooking continued, as evidenced by IO dates. Earth Oven Construction and Use in Central Texas

The same literature review that provided the radiocarbon database was used to compile evi­ dence of resources targeted for food, fuel, and packing material. Our focus is on 45 ovens tested over the last two decades (Tables 3.3 and 3.4). Flotation and macrobotanical identification are increasingly common in recent excavations, and several studies have used analysis

33

of lipids, phytoliths, and starch identification to clarify what items were brought into earth oven facilities (see also Walter and Schroeder, this volume). While increased flotation and new methods may yet provide definitive answers regarding which food resources were targeted and which materials were used to construct and fuel earth ovens, the immediate effect is to confound our understanding, as the diversity of recovered plant and animal indicators seems to increase with increased analysis (Mehalchick et al. 2004). One of the principal stumbling blocks in differentiating food, fuel, and packing material is that ovens — ​especially with reuse — ​can quickly become palimpsests of diverse activities, including those unrelated to cooking (Thoms et  al. 2018:95). Artifacts, as well as plant and animal remains, were likely introduced to earth oven features as part of the sediment used to cap the oven (Black and Thoms 2014:218; Leach et al. 2005:201–202). After cooking, the sediment cap, and any secondary artifacts and ecofacts it contained, were dispersed as the oven was opened. The repeated cycles of construction, uncapping, and reuse makes differentiation between food, fuel, and packing material a challenge. Further, Black and Thoms (2014:209–210) argue that abandoned or inactive oven pits were often used for general trash disposal, which compounds the identification challenge. The resulting mix of earth oven sediment, mingled artifacts and ecofacts from earlier occupations, and unrelated trash disposal makes it extremely difficult to accurately reconstruct original food, fuel, and packing material involved in any given baking event. Nevertheless, our Tables 3.3 and 3.4 attempt to classify macrobotanical material recovered from ovens as likely food, fuel, or packing materials. Of the 28 features in Tables 3.3 and 3.4 with fuel wood identified, oak is present in 19 (ca. 68 percent). The predominance of oak is highlighted by a flotation example. At four earth oven sites in Brown County, wood identified from flotation found 14 out of 55 specimens were identifiable as oak, while only one speci­men could be identified as mesquite. All

Reported Feature

Unit 1, Feature 6 Unit 1, Feature 9 Unit 2, Feature 7 Feature 2 Feature 6 Area 2, Test Unit 16 Area 2, Unit 29, Feature 12 Area 2, Unit 33, Feature 8 Area 2, Unit 35, Feature 11 Area 2, Unit 50, Feature 15 Area 3, Feature 3 Area 3, Unit 64, Feature 4 Feature 1

Feature 1 Feature 19 BRM

Unit 1, BRM Feature 8

Site

41CV413 41CV413 41CV413 41CV413 41CV413 41CV595 41CV595 41CV595 41CV595 41CV595 41CV595 41CV595 41ED28

41KR621 41KR621 41MI77

41MS69 41WM1126

Identified Fuel Wood

ash, maple, oak oak

oak oak, sycamore elm, oak

sycamore

box elder, oak, willow oak, pecan agave, sotol, yucca, prickly juniper, mesquite, pear, high-fat plant oak, woody legume amaranth, chenopodium amaranth, walnut shell lily bulb, chenopodium, acorn shell, pecan shell oak lily bulb oak

fauna, acorn acorn, pecan shell, fauna camas, beaver

geophyte mammal camas, onion, fauna

acorn

Identified Food Types

Table 3.3. Burned Rock Midden Features (BRMs) with Identified Macrobotanical Remains.

grasses

prickly pear

water plantain

Quigg et al. 2015 Carpenter et al. 2013

Houk et al. 2008 Houk et al. 2008 Johnson 2009

Mehalchick et al. 2002 Mehalchick et al. 2002 Mehalchick et al. 2002 Quigg et al. 2011 Quigg et al. 2011 Mehalchick et al. 2004 Mehalchick et al. 2004 Mehalchick et al. 2004 Mehalchick et al. 2004 Mehalchick et al. 2004 Mehalchick et al. 2004 Mehalchick et al. 2004 Quigg et al. 2008

Identified Packing Material Reference

Reported Feature

Feature 4 Feature 5 Unit 5, Feature 3 Unit 5, Feature 4 Unit 5, Feature 5 Unit 4, Feature 3a Unit 7, Feature 6 Unit 7, Feature 7 Unit 7, Feature 8 Area 1, Unit 6, Feature 6 Area 2, Unit 52, Feature 14 Feature 3 Feature 11 Unit 2, Feature 7/96 Unit 8, Feature 3a/96-6/97 Feature 2 Feature 7 Feature 13 Feature 25 Feature 26 Feature 34 Feature 2 Unit 5, Feature 1 Unit 5, Feature 2 Feature 4 Feature 11 Feature 12

Site

41BL1214 41BL1214 41BL278 41BL278 41BL278 41BL278 41BL278 41BL278 41BL278 41CV595 41CV595 41HY160 41HY160 41HY165 41HY165 41KR621 41KR621 41KR621 41KR621 41KR621 41KR621 41LM50 41MS69 41MS69 41TV2125 41TV2125 41TV2125 mammal onion mammal

geophyte

walnut shell chenopodium chenopodium chenopodium

agave, sotol, yucca

chenopodium

fauna

geophyte

geophyte geophyte lily, geophyte

Identified Food Types

conifer hackberry, oak, conifer oak, willow oak, walnut, willow oak

oak

juniper

oak

juniper, oak

grasses sponge spicules, grasses sponge spicules, grasses

grasses grasses

Griffith and Kibler 2005 Griffith and Kibler 2005 Quigg and Frederick 2015 Quigg and Frederick 2015 Quigg and Frederick 2015 Quigg and Frederick 2015 Quigg and Frederick 2015 Quigg and Frederick 2015 Quigg and Frederick 2015 Mehalchick et al. 2004 Mehalchick et al. 2004 Nickels and Bousman 2010 Nickels and Bousman 2010 Leezer 2013 Leezer 2013 Houk et al. 2008 Houk et al. 2008 Houk et al. 2008 Houk et al. 2008 Houk et al. 2008 Houk et al. 2008 Quigg et al. 2014 Quigg et al. 2015 Quigg et al. 2015 Karbula et al. 2011 Karbula et al. 2011 Karbula et al. 2011

Identified Packing Material Reference

ash, elm, oak, pecan, yaupon elm, oak, walnut juniper or cypress grasses juniper or cypress juniper or cypress juniper or cypress juniper or cypress juniper or cypress sponge spicules

Identified Fuel Wood

Table 3.4. Individual Oven (IO) Features with Identified Macrobotanical Remains.

36

Richard McAuliffe, R aymond Mauldin, and Stephen L. Bl ack

23 wood specimens identified in macrobotanical collections were oak (Dering 2003:99–100). This is not surprising, given the abundance of oak across the region (Amos and Gehlbach 1988). However, beyond oak, note that most other readily available fuel-­wood sources appear to be represented, with 13 other taxa identified in these 28 features. The limited organic preservation conditions at most reviewed sites leave some evidence of fuel in the form of wood charcoal, but little remains in the way of other, more fragile charred plant from packing material used to surround and protect the baked foods. Only 10 of the features from Tables 3.3 and 3.4 yielded samples that we interpret to reflect packing material. Grasses are the most common packing residuum, present in seven cases. This includes grass starch at site 41BL278 (Quigg and Frederick 2015); grass phytoliths and starch from two earth ovens at site 41MS69 (Quigg et  al. 2015); grass starch from a burned rock dump at 41LM50 (Quigg et al. 2014); grass starch and phytoliths from two smaller features at 41HY165 (Leezer 2013); and macrobotanical grass remains from 41MI77 (Johnson 2009). Use of grass as packing material is also reflected in the ethnographic literature (Dering 2003:104). While the phytolith-­based identification of sponge spicules in sediment for several ovens may indicate the introduction of water to promote moist baking and prevent charring (Thoms 2008b:445), the recovery of water plantain in an oven at site 41CV413 (Quigg et al. 2011) suggests the use of freshwater grasses as a packing material (Table 3.3). This suggestion is supported by sediment analysis from ovens at 41MS69 (Table 3.4), where diatom cells typical of freshwater sources, grass starch from the Triticeae family, Chloridoids grass, and sponge spicules were found (Quigg et  al. 2015). Easily harvested along the waterways and from permanent springs of Central Texas, aquatic grasses may have been a preferred packing material, when available, offering a ready source of moisture during the baking process. Finally, note that prickly pear pads, frequently used as packing material in actualistic studies (e.g., Dering 1999; Thoms et al. 2018), are not common in

our sample. Only a single case, from Feature 1 at 41ED28 (Quigg et al. 2008) was reported (Table 3.3). The paucity of direct evi­dence of prickly pear stands in stark contrast to the abundant evi­dence of grass specimens reported from ­matrix in Central Texas earth ovens as likely packing material. Turning to food resources, considerable evi­ dence shows that the carbohydrate-­rich bulbs of desert succulents, including sotol (Dasy­lirion spp.) and Agave lechuguilla, and geophytes such as onions (Allium spp.) and camas (Camassia spp.), were primary food items processed in Central Texas ovens. Evidence for baking of sotol and lechuguilla are especially common in the drier southern and western portions of the Edwards Plateau (Black et al. 1997; Thoms 2008a:​121). On the somewhat wetter northern and eastern portions of the Plateau, geophytes appear to have been the primary resources. Dering (2003:​105) noted 31 sites with i­ndications of bulb processing in ovens on the Plateau. In Tables 3.3 and 3.4, geophytes and desert succulents are well represented in our more recent sample, being present in 13 of the 27 features with food remains identified. A variety of other potential foods are also present, with instances of wild grains, including chenopodium (n = 6) and amaranth (n = 2), as well as a range of nutshell with acorn (n = 4), walnut (n = 2), and pecan (n = 1). Wild grains may, however, reflect disturbance plants rather than processed items. Further, given the amount of fuel wood needed for baking events (Dering 1999; Mauldin and Nickels 2003a:220– 224), nut fragments may reflect inadvertent byproduct rather than a targeted food source. Eight features also include faunal remains or residual faunal lipid residue; four of these eight yielded only faunal evidence. This may indicate that some ovens functioned as generalized locations of plant or animal processing rather than specific locations focused on exploitation of geophytes and succulents (Collins 2004:124; Black et al. 1997:291). For example, excavations on site 41TV2125 in Travis County yielded multiple earth ovens with plant remains, including bulbs and fuel wood, but additional ovens only evidenced fauna, including a small oven feature



Central Texas Plant Baking

that yielded an “abundance of animal bone, including the deer mandible, [which] suggests that this feature’s primary function was in animal processing” (Karbula et al. 2011:155). While cases such as those from 41TV2125 demonstrate that faunal remains are clearly present in ovens, the palimpsest nature of hot-­ rock cooking features, when combined with their use for expedient disposal of unassociated debris, likely complicates any clear understanding of what food items were processed. This is especially problematic in BRMs with a higher probability of mixed material from numerous baking events. To begin to clarify, we focus on the foods reflected in the individual ovens (IOs) in Table 3.4. There is one case with walnut shell and four with Chenopodium, all of which we can discount as likely unrelated to oven use. Of the 10 remaining cases, seven had either geophytes (n = 6) or succulent species recovered. Nevertheless, three IOs in our sample of 10 only contained fauna. While the recovery of faunal remains in oven features points to some level of animal processing, our results continue to support the notion that baking geophytes and succulents was the primary focus of oven features in Central Texas. Oven use focused on geophytes and succulents did not occur in isolation. The role of lower-­return resources in the diet — ​those most commonly processed in ovens (Dering 1999, 2005) — ​would be expected to decline as the availability of a high-­ranking resource such as bison increased. Yet, as noted, the periodic increased availability of bison — ​such as during the Calf Creek horizon (ca. 5955–5815 cal BP) and the Toyah phase (ca. 650–300 cal BP) — ​does not consistently pattern with the expectations of reduced oven processing needed for lower-­ ranking resources. While BRMs decrease, IO use does not decline during Toyah, and IO use increases during the earlier Calf Creek bison presence. Nor does the use of ovens show the “steady increase” throughout the Holocene suggested by Thoms (2009:580; see also Freeman 2007; Johnson and Hard 2008). Oven use does increase, but, at least in our Central Texas data, the growth in use appears to start around 3000 cal BP and is certainly not steady.

37

Our chronological data showing accumulation of earth oven facilities does provide evidence for increased exploitation of lower-­ ranked geophytes and succulents (see Dering 1999, 2005) at certain periods in Central Texas. These periods of increased oven use and reuse reflect intensification, with an increase in labor to maintain or increase food yields (see Boserup 1965; Morgan 2015). The specific primary drivers of these periods of intensification are not clear, but population growth and regional population circumscription, and decreasing mobility options and increasing demands for food likely play significant roles. Unlike surrounding regions, intensification did not result in adoption of horticulture in Central Texas, where availability of generous wild resources and earth oven plant processing have been posited as viable alternatives (Johnson and Hard 2008:139). Beyond Chronology and Subsistence

The use of ovens, at least during some periods, may also be a response to other considerations that go beyond strictly defined subsistence concerns. These include possible roles for earth ovens in the social and ritual spheres. Collins (2004) has critiqued Central Texas archaeology as historically focused on chronology and subsistence, with little movement beyond this foundation. In addition to highlighting the adaptive importance of Central Texas earth ovens as evidence of intensification, given population growth or regional population circumscription, our synthesis of dating, construction, and subsistence evidence provides a framework for addressing several more challenging questions raised by the 9,000-­year regional oven record. Focusing on BRMs and the notion of persistent places, we consider evidence for the ritual or social significance of these features, including their potential use as cemeteries and possible role in supporting feasting activities. Some Central Texas oven facilities were formed by multiple generations of hunter-­ gatherers reusing the same oven locale, thus creating BRMs, mounds of earth and rock readily visible on the landscape and recognizable as traditional places for resource ­processing.

38

Richard McAuliffe, R aymond Mauldin, and Stephen L. Bl ack

From this perspective, the value of these locations can be considered through the idea of “persistent places” (Schlanger 1992), locations used repeatedly by succeeding occupations over a significant period. This perspective shifts the emphasis from features and sites to landscapes (see Black and Thoms 2014; Knapp 2015). Prominent BRM locations meet the three categories defined by Schlanger (1992:97). First, they accrued in areas of desirable environmental attributes necessary for earth oven cooking (i.e., fuel wood, stone, soil, and food resources). Second, they became areas where cultural features focused reoccupations. An earth oven pit may sit unused for years or decades before the next firing, but such locations would be recognized by subsequent inhabitants as designated spaces for plant processing (Black and Thoms 2014:209). Third, BRMs became places where cultural material was available from previous occupations for reuse, including soil and stone gathered for earth oven cooking as well as culturally modified chert (i.e., discarded flakes and tools) available for expedient tools and as blanks for formal tools (e.g., Goode and Black 1997). The concept of persistent places has been used in other regions to identify trends of increasing ritual or spiritual significance of those landscapes (Gamble 2017; Moore and Thompson 2012). One of these trends identi­ fies the presence of burials in conspicuous ­locations  — ​especially those intrusive into preexisting features — ​as evidence of sacredness and ritual importance (Gamble 2017). The use of cemeteries is not the norm worldwide among hunter-­gatherers. Johnson and Hard cite a study by Binford (2004) that suggests only 81 of 263 hunter-­gatherer groups (ca. 31 percent) used cemeteries for social units larger than the family level. Further, these cases tend to be associated with high population densities and land use intensification (Johnson and Hard 2008:145; see also Freeman 2007; Thoms 2009). Our survey of relevant literature suggests that burials are not common within Central Texas BRMs. Pearce (1919:230–231) mentioned one human skeleton from a BRM in Williamson County and stated that human skeletal remains were re-

ported from other BRMs. Kelley and Campbell (1942:319) reported that burned rock middens “occasionally [contain] human burials.” While there are references in our data set to isolated skeletal elements such as a molar (Carpenter et  al. 2012) or a phalanx (Johnson 2009), we documented only four cases of burials within BRMs (Mehalchick et al. 2002:38; Decker 1997:​ 741; Wesolowsky 1970:248; Francis 2003). The rarity of burials in BRMs may suggest that hunter-­gatherers valued earth oven facilities as functional places for continued oven construction. Intrusive burials would likely mean abandonment of the BRM as an appropriate location for cooking. Another sign of increased social significance of a persistent place is growth in artifact diversity, indicating longer occupations by the same group or occupations by larger groups (Moore and Thompson 2012). Artifacts not directly associated with subsistence, such as decorative adornments or imported exotic material, would lend support to the idea that earth oven complexes became locations of ritual importance (Koenig et al., this volume). In our Central Texas review, however, this test generally fails. Exotic materials are rarely reported from BRM sites. For example, only a single imported sherd and two marine shells were reported at 41ED28 (Quigg et  al. 2008), and ochre was found among an intact burned rock feature at 41BX1577 (Figueroa and Tomka 2004:30). Overall, the recovered artifacts are not suggestive of social significance in most Central Texas BRM sites. These BRMs contain relatively little in the way of artifacts unassociated with baking, though some earth oven sites have assemblages reflecting a variety of activities. For example, the evidence of diverse activities such as lithic tool manufacturing and maintenance, hide processing, and plant processing at many Fort Hood earth oven sites, including 41CV595 and 41CV314, implied to the researchers these sites functioned as residential or base camps (Mehalchick et  al. 2002; see also Mehalchick et al. 2004; Quigg and Frederick 2015). While varied artifact assemblages indicate that some earth oven facilities might have become cen-



Central Texas Plant Baking

ters of domestic activity (Black et al. 1997:86), others show little variation in artifact assemblage, suggesting short-­term occupations (e.g., Weston and Mauldin 2003). Group sizes inferred from individual earth ovens and artifact assemblage diversity may indicate whether those sites were occupied by aggregations of social groups or were instead used by specialized foraging teams. Black and colleagues (1997:301) recognized that some BRM use might have been related to celebrations or provisioning for gatherings of larger social groups. In Central Texas, bulk food processing, which would be important for ceremonial occasions, has seen little research (Boyd et al. 2004). A recent exception is found in Dozier’s (2019) argument that dramatic increases in the sizes of some earth ovens in the Late Prehistoric Toyah phase may reflect increased food requirements associated with large gatherings of people at feasting locations (see also Thoms 2009:587; Wandsnider 1997). Note, however, that our data suggest a decline, at least in the number of dates associated with BRMs, during Toyah. Boyd and coworkers (2004) have developed a model of seasonal usage for site 41CV595 in which occupants were on site for less than three weeks. They reason that the short seasonal window of geophyte bulb availability (less than six weeks) would encourage rapid movement among several BRM processing sites in a s­ ingle season (Boyd et al. 2004:220–222; see also Dering 1999, Mauldin 2003a). The general lack of artifact class diversity in Central Texas earth oven facilities lends credence to the idea that even large accumulations of fire-­cracked rock in BRMs may not correspond with large occupying groups associating with a site for the long periods necessary to accrue social significance. Repeated earth oven firings result in an abundance of refuse, creating an archaeological signature outsized for the caloric return, likely leading to overestimation of group sizes and length of occupations at oven sites (Dering 1999; Koenig and Black 2019). Another avenue to investigate the roles that earth ovens may have in ritual or ceremonial gatherings centers on alcohol production. As

39

documented by Dietler (2006; see also ­Phillips 2014), alcohol is the most widely used psycho­ active agent in human history, with thousands of years of social, economic, political, and religious importance. In addition to its symbolic significance in ritual contexts, alcohol consumption has been an integrative social act for as long as it has been available, used in conjunction with feasting as a socially important practice (­Dietler 2006) and in creation and maintenance of ­social relationships (Phillips 2014:​21–22). Agave and sotol, succulents processed in earth ovens, were prevalent throughout northeast Mexico for production of alcoholic beverages (Driver and Massey 1957:​26). Miller (2019; Miller and Graves, this volume) also argues for the importance of ovens in processing these succulents for both food and fermented beverages in ceremonial contexts in the Southwest U.S. Identifying alcohol production, however, will be challenging within Central Texas, given that agave was pit roasted in essentially the same way for both food and alcohol, (Driver and Massey 1957:266). Dietler (2006) noted that research into the prehistory of alcohol has been extended in recent decades with focus on residue analysis from ceramic vessels. Yet, while such analysis may be a path to testing the possible role of BRMs in alcohol production (Dozier et al. 2020; Miller 2019), ceramic vessels were in use only at the end of the prehistoric sequence in Central Texas. Conclusion

Earth oven technology was used to bake carbohydrate-­rich plants across the Edwards Plateau of Central Texas for over 9,000 years. This technology left myriad archaeological signatures — ​most prominently, distinctive arrangements of fire-­cracked rocks that form features ranging in size from individual ovens (IOs) 1–2  m across to mounded piles larger than 25 m in diameter (BRMs). Our synthesis of radiocarbon dates shows that the earliest recognized BRMs in the region occurred roughly 8,000 years ago. These larger accumulations appear to be consistently present at a low frequency between 6000 and 1300 cal BP. At that

40

Richard McAuliffe, R aymond Mauldin, and Stephen L. Bl ack

point, dates on ovens increase dramatically, driven primarily by dates on these larger ovens suggesting their more frequent reuse. Oven use peaked between 1300 and 600 cal BP during the region’s Late Prehistoric Austin interval. While earth oven cooking continued into the following Toyah interval, that use was primarily driven by IOs, as dates on BRMs decline significantly after 600 cal BP. Evidence for construction — ​and the lack of clear evidence for ritualistic roles — ​suggests that ovens in Central Texas were functional workplaces for processing several different foods using readily available raw materials. Desert succulents, geophytes, and other food sources were commonly protected by grass packing material as they were baked with heated rocks in earth-­covered ovens, often fueled by oak. At the IO level where features likely reflect single or limited use, evidence suggests some IO cases were used to process meat. However, the majority were likely resource-­specific ovens used to bake plants, such as geophytes or desert succulents, that required long-­term baking. Interpretations of the larger burned rock middens are complicated by the pattern of reuse, but it seems these larger facilities became places for process-

ing several different plant and animal resources, suggesting that over time they became hot-­rock cooking workplaces. Ovens continue to be a focal point of Central Texas archaeology, bringing new data to light and refining our understanding of this technology as fundamental to the lifeways of prehistoric Central Texans. The early research questions — ​which activities led to BRM formation, why they began and continued, and when they happened — ​are now better understood. Yet the nearly continuous record of earth oven use in Central Texas needs to be considered within broader research topics such as climate change, population growth, development of new technologies, and the broadening or narrowing of diet breadth (cf. bison presence). A risk abatement strategy through maintaining a diversity of food resources, intensification in the context of increasing populations with potentially decreasing mobility, and seasonal oven use are all avenues for investigation. While we found no clear connection with social aspects in Central Texas ovens, that possibility remains an open research opportunity with potential to increase our understanding of these features and the people for whom they were a part of life.

4 Using Fire-­Cracked Rock to Evaluate Earth Oven Intensification in the Lower Pecos Canyonlands of Texas Charles W. Koenig, Emily R. McCuistion, Stephen L. Black, Charles D. Frederick, J. Phil Dering, J. Kevin Hanselka, Leslie Bush, and Ken L. Lawrence

Fire-­cracked rock (FCR) is a durable artifact that signals a substantial economic and technological change, yet it remains an under­studied artifact class for measuring and evaluating broader questions such as intensification. As discussed by Koenig and Miller (this volume), Alston Thoms (2008a) uses the presence of FCR to identify when hunter-­gatherers began to include desert succulents and geophytes in their diets — ​the “carbohydrate revolution” — ​a  process that required the use of earth oven technology to render certain plants edible. Thoms and others argue the appearance of earth ovens signals subsistence intensification related to growing populations that required more calories from the landscape (Dering 1999; Freeman 2007; Johnson and Hard 2008:148; Thoms 2008a, 2009; Yu 2009). However, only a limited amount of research has focused on evaluating whether demographic increase in and of itself drove earth oven intensification or whether other factors may better explain the increases in population hypothesized to spur earth oven intensification. In this chapter, we analyze the record of earth oven construction and FCR from four rockshelter sites in the Lower Pecos Canyon­ lands (LPC) of Southwest Texas to evaluate whether demographic increase, climate-­induced population packing, or social aggregations spurred earth oven intensification (Morgan

2015). The LPC region is ideal for evaluating earth oven intensification via changes in fire-­ cracked rock morphology for two primary reasons: (1) the record of earth oven baking spans the entire Holocene (Hester 1983; McCuistion 2019); and (2) native peoples maintained a hunting-­gathering-fishing lifestyle and never adopted nonnative domesticates (Dering 2002; Turpin 2004). We consider intensification as an increase in subsistence-­related labor at the expense of energetic efficiency driven by popu­ lation growth (intensification sensu Boserup 1965, 1981). We test the notion that FCR can be used to  measure intensification within four rock­ shelter sites in Eagle Nest Canyon (ENC), a short, box canyon tributary to the Rio Grande, that preserve a local record of earth oven baking spanning the entire Holocene (10,500–600 cal BP). We evaluate intensification by measuring changes in FCR morphology and density, and we hypothesize that as population increases (intensification), the size of discarded FCR will decrease and discarded, fire-­cracked rock density will increase (see also Miller 2019). To evaluate how demographic, climate, and social factors may influence population growth and contribute to earth oven intensification, we compare changes in burned-­rock size and density to (1) changes in population as estimated via summed probability distribution (SPD) of 41

42

Charles W. Koenig, Emily R . McCuistion, Stephen L. Bl ack , et al.

Lower Pecos radiocarbon dates; (2) the general climatic record for the region; and (3) the published radiocarbon dates of Pecos River-­style pictographs (Bates et al. 2015; Steelman et al. 2021b). We use Pecos River-­style rock art as a marker of social factors because it represents the diagnostic archaeological component for the Lower Pecos (e.g., Boyd 2016), and has been hypothesized to be related to earth oven intensi­fication (Turpin 1990). In this chapter we also describe the Rock Sort documentation method used during the Eagle Nest Canyon excavations to quantify burned-­rock morphology (Black et al. 1998b:​ 52). Using Rock Sort data and K-­means cluster analysis, we identify four different clusters that we argue are linked to behavioral zones within earth oven facilities. We describe changes in FCR morphology and density through time within each behavioral cluster and focus our discussion on the discard deposits (Clusters 1 and 2). We identify peaks in FCR density during the early Holocene Alti­thermal (ca. 5000 cal BP) and the late Holocene (ca. 2000 cal BP). These peaks in FCR density correlate with the SPD for all vetted rockshelter Lower Pecos radiocarbon dates, suggesting that regional demographic increase is a driving factor behind earth oven intensification. However, during these two periods of increased population there are differences in FCR sizes within the discard deposits that we hypothesize reflect an emphasis on thermal efficiency in the early Holocene (high density of large rocks [>  11 cm in maximum dimension]) versus an emphasis on labor efficiency in the late Holocene (high density of small rocks [ 15 cm kg

629.2 155.7 69.7 82.7 5.4 43.7 334.0 96.7 151.5 583.9 59.2 93.4 167.1 128.3 44.8 858.1

kg/m3

Totals

11.2 5.1 1.6 7.0 0.4 0.8 13.1 2.3 5.4 11.3 0.8 5.8 10.3 3.9 0.5 95.7

kg

2 3 3 3 3 3 3 3 3 2 3 3 3 3 3 4

Cluster



Using Fire-­Cracked Rock to Evaluate Earth Oven Intensification

without the various quantification methods used by archaeologists in Texas and beyond.1 Such methods are important because they provide a replicable technique to understand the complex cultural depositional environment that are earth oven facilities. Rock Sort in Eagle Nest Canyon

Within each of the four investigated rock­ shelters, Rock Sort was a major task during excavations. The general procedure was to pull all rocks larger than ~5 cm in maximum dimension and place these in a bucket. A ­ dditional rocks larger than one inch were pulled from the screened fill and added to the rock bucket. Once excavation of a layer/level/strat was complete, the rocks were taken to a gridded Rock Sort board (Pagano 2019:Figure 4.1) and divided into four different size classes based on maximum dimension:  15cm. The FCR was weighed by size class, and individual rocks were counted for all but the smallest size class. The final Rock Sort step occurred in the lab where excavated volumes were calculated using either unit measurements or volumes derived from Structure from Motion (SfM) photogrammetry (Koenig et al. 2017; Willis et al. 2016). By calculating the volume, we could measure a total FCR density (kg/m3) per excavated unit. Evaluating Changes in Fire-­Cracked Rock within Eagle Nest Canyon

Of the 18 identified earth oven facilities within the ENC rockshelters (Table 4.1), 16 are used in this analysis.2 In total, 132 excavated proveniences among the 16 EOFs provide Rock Sort data to evaluate changes in FCR through time. Original Rock Sort data for Kelley (Table 4.2) and Eagle (Tables 4.3, 4.4) are reported here. Readers are directed to Heisinger (2019) for Skiles Shelter and Koenig and Castañeda (2023) for Horse Trail. We used K-means cluster analy­ sis in R (R Core Team 2020) to define three major behavioral facies using differences in FCR density by size class: outer discard (Clusters 1 and 2), central pit/edges of EOF features

53

(Cluster 3), and heating elements (Cluster 4).3 Clusters 1 and 2 are defined by high density of the two smallest size classes ( 15 cm). Cluster 3 is defined by relatively low density across all size classes. Finally, Cluster 4 is defined by a high density of the largest size class (> 15 cm). Table 4.5 presents a summary of the K-­means cluster assignment by EOF. Within the ENC rockshelter data, the only proveniences that appear to be misclassified are from Skiles Shelter (Feature 3; EOF 2) and Eagle Cave (EOF 2 [Feature 12], EOF 3 [Units 67, 87, and 135], and EOF 12 [Feature 2]). Skiles EOF 2, Eagle EOF 2, and Eagle EOF 12 are all remnant heating elements that should have been included in Cluster 4 rather than Cluster 3. The Eagle EOF 3 proveniences should have been within one of the two outer discard clusters (Clusters 1 or 2) but instead were grouped with the heating elements (Cluster 4) because of the high density of the largest two size classes (> 11 cm). Regardless, even though some Rock Sort data was miscategorized behaviorally in K-­means, we did not arbitrarily reorganize any proveniences into different clusters. From the behavioral contexts assigned using the K-­means clusters, we evaluate change in fire-­cracked rock through time by behavioral facie using data from Table 4.5.4 We wanted to assign the different clusters to only one behavioral context and so combined Clusters 1 and 2, as we suspect both represent outer discard deposits rather than distinct behavioral contexts. By doing so, we were able to assess FCR variation through time within three EOF facies: outer discard (Clusters 1 and 2), central pit/ inner discard (Cluster 3), and heating elements (Cluster 4; Figures 4.5a, 4.5c, 4.5e). In total, of the 16 Eagle Nest Canyon EOFs included in this analysis, 10 EOFs have outer discard deposits (Clusters 1 and 2), 14 have central pit/feature edge (Cluster 3), and 8 have proveniences classi­fied as containing heating elements (Cluster 4). A radiocarbon date midpoint calculated using the date ranges (cal BP; see Table 4.1) was assigned to each EOF to allow for visualization of FCR change through time.

167 EOF 4

167 EOF 5

EOF *

Volume (m3)

0.036 0.031 0.023 0.035 0.027 0.045 0.005 0.012 0.019 0.004 0.020 0.008 0.006 0.008 0.015 0.008 0.002 0.009 0.005 0.042 0.005 0.009 0.016 0.025 0.014 0.051 0.019

Rock Sort Columns

41VV167.U57.S237-238 41VV167.U64.S237-238 41VV167.U66.S267 41VV167.U80.S288 41VV167.U102.S288 41VV167.U136.S548-549 41VV167.U86.L1(S342, 359) 41VV167.U86.L2(S359, 333) 41VV167.U86.L3(S359, 333, 304) 41VV167.U86.S304 41VV167.U86.S334 41VV167.U86.S335,336 41VV167.U86.S337 41VV167.U86.S338 41VV167.U84.S237 41VV167.U84.S238 41VV167.U84.S358 41VV167.U61.F9 41VV167.U97.S393 41VV167.U95.S385 41VV167.U117.S516 41VV167.U117.S517 41VV167.U117.S385 41VV167.U135.S385 41VV167.U96.S421 41VV167.U87.L2 41VV167.U76.L7

7.1 9.8 8.4 11.9 6.9 13.0 0.2 1.6 2.8 0.7 1.8 2.4 0.3 1.8 0.5 0.4 0.2 1.0 0.2 12.0 1.2 1.3 4.2 9.1 1.3 9.5 4.1

kg

197.9 317.3 366.5 339.7 253.7 288.2 35.8 133.3 146.3 147.7 89.0 301.3 53.4 213.4 35.3 56.0 133.3 115.1 36.5 285.5 246.0 148.2 259.4 364.0 89.8 186.1 214.7

kg/m3

< 7.5 cm

5.9 8.1 9.9 13.0 11.7 7.7 0.4 0.9 1.9 0.3 0.9 2.5 0.0 0.3 0.0 0.0 0.0 0.5 0.0 17.5 0.8 0.5 7.1 14.2 2.0 16.0 6.3

kg

164.2 260.6 430.4 370.6 433.0 171.1 66.0 75.0 97.9 61.4 47.0 317.5 0.0 36.6 0.0 0.0 0.0 53.5 0.0 416.4 162.0 56.5 443.1 569.6 144.3 313.9 331.6

kg/m3

7.5–11 cm

Table 4.3. Rock Sort Data and Cluster Assignment for Eagle Cave Earth Oven Facilities 1–5.

3.1 3.3 2.6 2.9 4.3 2.9 0.0 0.5 1.1 0.0 0.0 0.0 0.4 0.3 0.0 0.0 0.0 1.9 0.0 9.4 0.0 0.0 2.1 6.1 0.2 9.6 4.0

kg

86.4 105.5 111.3 82.9 158.9 64.9 0.0 45.0 58.4 0.0 0.0 0.0 69.0 36.6 0.0 0.0 0.0 225.6 0.0 223.3 0.0 0.0 129.4 245.6 11.4 188.0 208.4

kg/m3

11–15 cm

FCR Size Classes kg

0.0 0.5 0.0 0.0 0.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.2 0.0 1.5 0.0 0.0 0.0 0.0 0.5 3.7 0.0

0.0 16.8 0.0 0.0 15.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 144.2 0.0 36.4 0.0 0.0 0.0 0.0 37.1 73.3 0.0

kg/m3

> 15 cm kg

16.1 21.7 20.9 27.8 23.3 23.6 0.5 3.0 5.8 0.9 2.7 5.0 0.7 2.4 0.5 0.4 0.2 4.6 0.2 40.4 2.0 1.7 13.3 29.5 4.0 38.8 14.3

448.5 700.2 908.3 793.1 861.5 524.2 101.9 253.3 302.6 209.1 136.0 618.8 122.4 286.6 35.3 56.0 133.3 538.4 36.5 961.7 408.0 204.7 831.9 1179.2 282.6 761.4 754.7

kg/m3

Totals

2 2 1 1 1 2 3 3 3 3 3 2 3 3 3 3 3 4 3 1 2 3 1 1 3 2 2

Cluster

*Earth Oven Facility

167 EOF 1

167 EOF 2

167 EOF 3

41VV167.U87.L6 41VV167.U67.L6 41VV167.U67.L7 41VV167.U97.S409, 411 41VV167.U96.S437 41VV167.U117.S525 41VV167.U135.S525 41VV167.U113.S499-501 41VV167.U79.F12 41VV167.U135.S555,556, 568 41VV167.U113.S505, 506, 509 41VV167.U141.L1(S577-579) 41VV167.U140.S594 41VV167.U142.S594 41VV167.U112.L5

0.093 0.016 0.005 0.013 0.005 0.010 0.016 0.008 0.016 0.019 0.011 0.015 0.008 0.004 0.060

14.7 1.2 0.8 1.1 0.8 2.0 2.2 1.8 0.9 0.2 0.1 0.3 0.2 0.3 1.3

157.6 74.4 146.3 86.4 152.8 206.3 139.7 214.5 55.6 7.8 6.1 17.2 27.8 62.5 22.0

17.8 1.3 1.8 1.0 0.7 1.2 2.9 0.9 0.7 0.3 0.0 0.3 0.0 0.1 2.1

191.5 82.1 331.5 80.3 124.5 128.1 187.8 102.4 44.4 16.1 0.0 22.8 0.0 25.0 35.5

21.9 0.0 1.4 1.7 0.0 0.0 4.2 1.0 1.0 0.3 0.0 0.0 0.0 0.0 2.3

235.9 0.0 259.3 136.2 0.0 0.0 269.9 120.5 61.9 17.1 0.0 0.0 0.0 0.0 37.5

19.5 0.0 0.5 0.0 0.0 2.1 1.4 0.0 2.6 0.0 0.0 0.0 0.0 0.0 0.0

209.1 0.0 88.9 0.0 0.0 217.7 87.2 0.0 165.0 0.0 0.0 0.0 0.0 0.0 0.0

73.9 2.4 4.5 3.8 1.5 5.3 10.7 3.6 5.2 0.8 0.1 0.6 0.2 0.4 5.7

794.2 156.4 825.9 302.9 277.4 552.1 684.6 437.3 326.9 40.9 6.1 40.0 27.8 87.5 95.0

4 3 4 3 2 2 4 2 3 3 3 3 3 3 3

0.058 0.029 0.042 0.090 0.089 0.025 0.012 0.019 0.021 0.004 0.009 0.004 0.014 0.009 0.006 0.018 0.031 0.030 0.016 0.040 0.014 0.015 0.018 0.020 0.030 0.055 0.052

Rock Sort Columns

167 EOF 12 41VV167.PS04.U4.F2 167 EOF 10 41VV167.PS04.U11.S072 41VV167.U26.L1(S147-151) 41VV167.U58.S251-261 41VV167.U35.S175-S177 167 EOF 8 41VV167.U57.S177 41VV167.U36.L3 41VV167.U36.L4 41VV167.U36.L5 41VV167.U26.S060 41VV167.U26.S152 41VV167.U26.S153 167 EOF 7 41VV167.U26.S154 41VV167.U26.S155 41VV167.U56.S198-S227 41VV167.U50.L1(S185) 41VV167.U50.L2(S187, 189) 41VV167.U50.L3(S189) 41VV167.U50.L4(S189) 41VV167.U50.L5(S189) 41VV167.U55.L1(S187, 189) 167 EOF 6 41VV167.U55.L2(S189) 41VV167.U55.L3(S189) 41VV167.U55.L4(S189, S190) 41VV167.U25.L3(F8) 41VV167.U25.L4(F8) 41VV167.U25.L5(F8)

* Earth Oven Facility

EOF*

Volume (m3)

1.4 8.1 2.5 4.6 34.0 12.7 1.7 3.6 1.4 0.5 0.1 0.5 0.1 0.5 0.1 3.0 3.1 0.5 2.9 6.6 1.6 0.0 0.5 7.0 3.3 0.1 4.0

(kg)

24.1 280.3 58.3 51.6 381.2 508.8 143.3 188.4 65.2 127.5 14.4 125.0 5.0 50.0 14.0 165.6 100.3 15.0 182.5 164.5 114.3 0.3 29.7 356.6 109.7 1.8 76.7

(kg/m3)

< 7.5 cm

1.8 9.6 0.2 1.5 29.9 8.9 1.2 1.9 1.7 0.5 0.0 0.1 0.0 0.0 0.4 4.4 4.0 0.5 2.2 3.8 4.6 0.7 1.3 1.6 4.3 0.4 3.3

(kg)

31.0 331.4 4.8 16.7 335.2 356.0 96.7 102.1 81.0 115.0 0.0 32.5 0.0 0.0 63.3 242.2 128.4 16.3 136.9 94.5 330.0 43.3 74.4 81.6 143.7 7.3 62.5

(kg/m3)

7.5–11 cm

1.3 1.6 0.0 0.5 10.9 1.2 1.3 1.0 0.3 1.8 0.0 0.0 0.0 0.0 0.6 2.2 1.3 0.5 1.9 1.0 1.5 1.1 0.4 1.6 6.4 0.5 2.7

(kg)

21.9 55.9 0.0 0.0 121.6 48.4 106.7 50.5 13.3 457.5 0.0 0.0 0.0 0.0 96.7 123.9 42.6 17.3 120.0 25.0 109.3 75.3 23.3 80.6 212.7 8.5 51.5

(kg/m3)

11–15 cm

FCR Size Classes

Table 4.4. Rock Sort Data and Cluster Assignment for Eagle Cave Earth Oven Facilities 6–8, 10, and 12.

6.2 0.0 0.0 0.0 0.9 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 0.4 0.0 1.8 2.5 2.2 1.3 0.0 0.0 5.3 0.0 0.4

(kg)

106.0 0.0 0.0 0.0 10.5 0.0 22.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 36.1 11.6 0.0 109.4 62.5 155.0 84.0 0.0 0.0 176.3 0.0 7.9

(kg/m3 )

> 15 cm

10.6 19.4 2.7 6.6 75.7 22.8 4.4 6.5 3.4 2.8 0.1 0.6 0.1 0.5 1.0 10.2 8.8 1.5 8.8 13.9 9.9 3.0 2.3 10.2 19.3 1.0 10.3

(kg)

183.1 667.6 63.1 73.2 848.5 913.2 369.2 341.1 159.5 700.0 14.4 157.5 5.0 50.0 174.0 567.8 282.9 48.7 548.8 346.5 708.6 202.9 127.5 518.9 642.3 17.6 198.7

3 2 3 3 1 1 2 2 3 4 3 3 3 3 3 2 3 3 2 2 2 3 3 2 4 3 3

(kg/m3 ) Cluster

Totals

1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4

Cluster

* Earth Oven Facility

164 EOF 2 164 EOF 1 165 EOF 1 166 EOF 1 167 EOF 10 167 EOF 8 167 EOF 6 167 EOF 5 167 EOF 4 167 EOF 3 164 EOF 1 164 EOF 2 165 EOF 2 165 EOF 1 166 EOF 1 167 EOF 12 167 EOF 8 167 EOF 7 167 EOF 6 167 EOF 5 167 EOF 4 167 EOF 3 167 EOF 2 167 EOF 1 164 EOF 1 165 EOF 3 165 EOF 1 166 EOF 1 167 EOF 7 167 EOF 6 167 EOF 5 167 EOF 3

EOF *

0.018 0.019 0.820 0.871 0.029 0.145 0.108 0.205 0.158 0.023 0.279 0.241 0.938 0.356 1.298 0.058 0.153 0.042 0.201 0.099 0.028 0.028 0.016 0.117 0.112 0.019 0.114 0.135 0.004 0.030 0.009 0.114

Volume (m3 ) kg

2.8 3.6 263.7 200.1 8.1 52.0 21.1 59.5 40.0 4.6 17.2 8.8 58.7 3.2 41.9 1.4 8.5 1.2 8.2 10.2 2.7 2.3 0.9 2.3 12.5 1.8 13.3 12.9 0.5 3.3 1.0 17.6

155.6 185.5 321.7 229.8 280.3 358.3 195.8 290.3 253.4 197.0 61.9 36.7 62.6 8.9 32.3 24.1 55.3 29.4 40.7 103.4 97.7 79.8 55.6 19.3 111.9 92.6 116.5 95.3 127.5 109.7 115.1 154.6

kg/m3

< 7.5 cm

6.5 6.4 172.2 192.8 9.6 41.9 16.6 58.8 61.9 2.7 11.3 4.7 52.4 4.7 24.5 1.8 3.4 0.5 10.1 4.6 2.5 2.3 0.7 2.9 26.6 2.3 16.8 11.5 0.5 4.3 0.5 22.5

kg

362.9 333.2 210.1 221.4 331.4 288.6 153.8 286.8 392.0 118.1 40.6 19.3 55.9 13.2 18.9 31.0 22.2 12.1 50.3 46.8 90.3 81.3 44.4 24.5 238.8 121.1 146.8 84.7 115.0 143.7 53.5 197.6

kg/m3

7.5–11 cm

2.0 1.3 47.6 97.6 1.6 14.3 8.3 19.1 31.1 1.0 10.5 1.5 59.4 1.3 10.2 1.3 0.7 0.6 6.5 2.4 0.2 1.7 1.0 2.6 32.6 2.8 24.4 32.0 1.8 6.4 1.9 27.6

kg

110.7 0.0 58.1 112.0 55.9 98.5 76.8 92.9 197.1 43.1 37.6 6.0 63.3 3.6 7.9 21.9 4.8 13.8 32.5 23.8 5.8 61.1 61.9 22.0 292.2 145.8 213.4 236.0 457.5 212.7 225.6 241.7

kg/m3

11–15 cm

FCR Size Classes

Table 4.5. Average Rock Sort Data by Eagle Nest Canyon Earth Oven Facility and Cluster.

kg

0.0 0.0 12.6 0.7 0.0 1.2 7.1 1.0 5.3 2.1 3.1 0.0 29.1 0.0 9.7 6.2 0.0 0.0 2.0 0.0 0.5 0.0 2.6 0.0 24.0 5.0 10.2 17.3 0.0 5.3 1.2 21.3

0.0 0.0 15.4 0.7 0.0 8.3 65.7 4.6 33.4 90.1 11.2 0.0 31.1 0.0 7.4 106.0 0.0 0.0 10.1 0.0 18.8 0.0 165.0 0.0 215.2 261.1 89.2 128.0 0.0 176.3 144.2 186.8

kg/m3

> 15 cm kg

11.2 11.3 496.0 491.1 19.4 109.4 53.0 138.3 138.4 10.4 42.1 15.0 199.6 9.2 86.2 10.6 12.6 2.3 26.9 17.2 5.9 6.3 5.2 7.7 95.7 11.8 64.7 73.7 2.8 19.3 4.6 89.0

629.2 583.9 605.2 564.0 667.6 753.7 492.1 674.6 875.9 448.3 151.2 62.1 212.9 25.8 66.4 183.1 82.3 55.3 133.7 174.1 212.5 222.2 326.9 65.8 858.1 620.5 566.1 543.9 700.0 642.3 538.4 780.7

kg/m3

Totals

and 2 (a, b), Cluster 3 (c, d ), and Cluster 4 (e, f ). Legend in (f ) corresponds to other graphs.

Figure 4.5. Boxplots of FCR density by K-­means cluster and changes in FCR density through time for combined Clusters 1



Using Fire-­Cracked Rock to Evaluate Earth Oven Intensification Changes in FCR Size through Time

Figures 4.5b, 4.5d, and 4.5f show the changes in FCR density by size class through time for the three behavioral facies. Since we could only use temporal midpoints for each EOF, the plots do not display differences in use duration. Essentially, the single points represent the average age and FCR density for each EOF. Cluster 3 rock sizes (Figure 4.5d) show relatively little change through time, and the distribution of rock size by EOF remains homogenous. The size class density data for Cluster 3 reflects the behaviors we expect from a central pit area where random rocks are left in the pit after earth oven cleanout. The > 15 cm peaks observed in the Cluster 3 data at 10,200 and 661 cal BP correspond to Eagle Cave EOFs 2 and 12, which are the misclassified earth oven heating elements discussed above. It suggests that other > 11 cm peaks in Cluster 3 data may also represent partial heating elements not identified in the field. Cluster 4 shows a relatively constant pattern through time where the medium–larger rock sizes (11–15 cm) have the highest density (Figure 4.5f ). This is interesting because the presence of medium–large size rocks within heating ele­ ments may indicate that virtually every ENC earth oven deposit contains reused FCR. Regardless, the ENC Rock Sort data supports previous burned-­rock studies that identified the highest density of large rocks corresponding with intact heating elements (e.g., Black et al. 1998b; Hines et al. 1994; Mauldin et al. 2003; Miller and Hanselka 2013; Tennis et al. 1997). The temporal distribution of combined Clusters 1 and 2 is much more intriguing: the FCR densities in Figure 4.5b represent the size of rocks that Lower Pecos earth oven cooks considered too small to be reused in subsequent constructions. The high density of FCR  15 cm within discard deposits.5 Although in many regards this trend should be expected, we hypothesize that the lack of discarded FCR > 15 cm reflects a change from thermal efficiency in the early Holocene (pre-­4000 cal BP) to labor efficiency in the late Holocene (post-­4000 cal BP).6 During the late Holocene, the density distribution of rocks within the ENC EOFs reflects the pure technological limit of earth ovens where most rocks are small (  15 cm) are nearly nonexistent. Behaviorally, this indicates rocks were more frequently reused and only discarded once they reached the   15 cm are also found in relatively high densities within the discard deposits. Further, until 4000 cal BP, rocks 7.5–11  cm were found in the highest density within discard zones. What the early Holocene data suggest is that rocks were being discarded earlier in their use lives, likely indicating thermal efficiency during earth oven construction. Discarding rocks