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Towards an interpretative framework for burnt ostrich eggshell

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Title:
Towards an interpretative framework for burnt ostrich eggshell an experimental study
Creator:
Diehl, Robert John ( author )
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Denver, Colo.
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University of Colorado Denver
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English
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iv, 48 pages : color illustrations ; 23 cm

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Subjects / Keywords:
Prehistoric peoples -- Food -- Research ( lcsh )
Eggshells -- Fire testing ( lcsh )
Eggs as food -- History -- Research ( lcsh )
Food -- Effect of heat on -- Research ( lcsh )
Ostriches -- Eggs -- Research ( lcsh )
Archaeology -- Methodology ( lcsh )
Archaeology -- Methodology ( fast )
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History. ( fast )
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )
History ( fast )

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Review:
Optimal foraging theory posits that hunter gatherers will seek to maximize the energetic and nutritional outputs of their diets. Recent research has examined how this has been achieved through cooking. For foods such as meat or tubers, the benefits are clear, but this is not always the case, especially when raw consumption is possible or the labor of cooking is intensive. Ostrich (Struthio spp.) eggs represent such a food, with indications of consumption predating and postdating control of fire. If cooking ostrich eggs is indeed the optimal, the archaeological record should reflect a shift in preparation contemporaneous with control of fire. In order to assess cooking patterns over time, a method for assessing thermally altered ostrich eggshell is necessary. This study reviews the lengthy history of ostrich egg exploitation in the archaeological and ethnographic records, as well as previous taphonomic studies of thermally altered eggshell, and presents the results of a series of actualistic studies of different types of heating and the resultant changes in color and morphology. The results demonstrate that anthropogenic and non-anthropogenic fires produce distinct patterns of changes, as well as a potential diagnostic for cooking. These results have potential applications in understanding site taphonomy and interpretation. Furthermore, it has the potential to provide insight into the role of cooking in hunter gatherer foraging strategies and optimal foraging theory.--Page iii.
Bibliography:
Includes bibliographical references (page 42-48).
Original Version:
Originally issued: 2017.
Statement of Responsibility:
by Robert John Diehl.

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University of Colorado Denver
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Auraria Library
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All applicable rights reserved by the source institution and holding location.
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on10480 ( NOTIS )
1048013902 ( OCLC )
on1048013902

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Full Text
TOWARDS AN INTERPRETIVE FRAMEWORK
FOR BURNT OSTRICH EGGSHELL: AN EXPERIMENTAL STUDY by
ROBERT JOHN DIEHL B.A., Illinois Wesleyan University, 2013
A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Master of Arts Anthropology Program
2017


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This thesis for the Master of Arts degree by Robert John Diehl has been approved by the Anthropology Program by
Jamie Hodgkins, Chair Christopher Beekman Charles Musiba
Date: December 16 2017


Diehl, Robert John (M.A., Anthropology Program)
Towards an Interpretive Framework for Burnt Ostrich Eggshell: An Experimental Study Thesis directed by Assistant Professor Jamie Hodgkins
ABSTRACT
Optimal foraging theory posits that hunter gatherers will seek to maximize the energetic and nutritional outputs of their diets. Recent research has examined how this has been achieved through cooking. For foods such as meat or tubers, the benefits are clear, but this is not always the case, especially when raw consumption is possible or the labor of cooking is intensive. Ostrich (Struthio spp.) eggs represent such a food, with indications of consumption predating and postdating control of fire. If cooking ostrich eggs is indeed the optimal, the archaeological record should reflect a shift in preparation contemporaneous with control of fire. In order to assess cooking patterns over time, a method for assessing thermally altered ostrich eggshell is necessary. This study reviews the lengthy history of ostrich egg exploitation in the archaeological and ethnographic records, as well as previous taphonomic studies of thermally altered eggshell, mid presents the results of a series of actualistic studies of different types of heating and the resultant changes in color and morphology. The results demonstrate that anthropogenic and non-anthropogenic fires produce distinct patterns of changes, as well as a potential diagnostic for cooking. These results have potential applications in understanding site taphonomy and interpretation. Furthermore, it has the potential to provide insight into the role of cooking in hunter gatherer foraging strategies and optimal foraging theory.
The form and content of this abstract are approved. I recommend its publication.
Approved: Jamie Hodgkins


IV
TABLE OF CONTENTS
CHAPTER
I. INTRODUCTION..........................................................1
Background...................................................4
Ostrich Eggshell at Archaeological Sites...............4
Natural Occurrences of Ostrich Egg in the Archaeological Record.5
Ostrich Egg Use in the Ethnographic Record.............6
The Rationale for Cooking..............................9
Previous Studies of Eggshell Taphonomy................13
II. EXPERIMENTAL STUDY....................................................18
Materials & Methods.........................................18
Results.....................................................23
Discussion..................................................32
Conclusion..................................................39
REFERENCES..............................................................42


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CHAPTER I INTRODUCTION
Cooking is a fundamental, even necessary, human behavior (Harris, 1992; James, 1989; Wrangham et al., 1999; Wrangham, 2009), one of a gradually shrinking set we can claim exclusive domain over. It has deep ties to culture, identity, mid social organization, but at a fundamental level, it facilitates our intake of energy mid ultimately our survival. Much archaeological research has focused on the procurement and processing of foods, but only relatively recently has the discipline begun to integrate information about the biochemical and nutritional benefits of cooking in the study of prehistory (Kelly, 2013; Subias, 2002; Wrangham et ah, 1999). These studies posit that cooking became a vital adaptive strategy adopted by early humans in order to maximize energy intake (Wrangham, 2009). In the cases of foods such as meat or tubers, the process represents a clear, beneficial trade-off (Wandsnider, 1997). The analysis of these adaptive trade-offs and their implementation in subsistence strategies is the key principle behind optimal foraging theory. If however those foods may be consumed raw or when the labor of cooking has the potential to outweigh benefits, that calculus becomes much more difficult.
Ostrich eggs are incorporated in archaeological sites that date back millions of years, and thus represent a food with a long history of human consumption. The earliest indications of its consumption predate control of fire by more than a million years (Roche et al. 1999) suggesting raw consumption typified the early use of this resource, but contemporary ethnographic records almost uniformly describe them as being cooked (Basedow, 1925; Cott, 1953; Wrangham, 2009). Given that egg can be eaten raw with no ill effects (Wrangham, 2009), why would there be an expectation that egg would consistently be cooked (mid the


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shells therefore altered), especially if they were consumed raw before the regular control of fire? Cooking would seem to represent an unnecessary, expensive behavior, with the benefits accrued by cooking offset by the additional labor. Yet, recent nutritional studies have noted significant increases in protein absorption in cooked egg compared to raw egg (Evenepoel et al., 1998; 1999). Furthermore, some scholars have raised that possibility that certain forms of cooking do not require significant added expense (Kelly, 2013). These factors raise the possibility that the cooking of eggs is indeed optimal, and archaeological indicators of cooking would be expected to appear consistently after control of fire, a behavior dated to approximately one million years ago (Bema et al., 2013).
In order to determine patterns of cooking over time, it must be identifiable in archaeological material. The ethnographic record provides descriptions of how these eggs are prepared (Cott, 1953; Wannerbugh et al., 2000; Wrangham, 2009), but the understanding of how those actions are reflected in the archaeological record is poor. This research aims to develop through experimentation mid guided by middle range theory (Binford, 1977) a framework for the interpretation of heat altered ostrich eggshell. Per Binford, middle range theory is that which seeks to link measurable patterning in archaeological data to cultural practices. For example, Binford (1980) famously tied the spatial patterning of Nunamiut sites with broader mobility strategies. Currently such frameworks exist for the interpretation of heat altered bone (Bennett, 1999; Buikstra & Swegle, 1989; Shipman et al., 1984). These were developed through combinations of laboratory and actualistic experiments, and primarily take into account how coloration and morphology can be explained by cooking or other anthropogenic alteration or can be dismissed as the result of natural phenomena. This research will seek to establish a similar body of knowledge for ostrich eggshell.


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The results of this research have the potential to contribute to archaeological scholarship on several levels. Specifically, it will facilitate the differentiation of anthropogenic cooking sites, anthropogenic eggshell disposal sites, and naturally occurring ostrich nests or carnivore dens modified by wildfires. This work will also help distinguish different egg cooking behaviors. This research has implications beyond archaeology. Being able to demonstrate consistent cooking of eggs would support the hypotheses of Wrangham and others and strengthen the use of human behavioral ecology in modelling subsistence. Conversely, if cooking were not consistent it would raise questions about other factors influencing diet, including culture, resource availability, mid social dynamics. More generally, understanding subsistence strategies and resource extraction is an integral part of placing past peoples within the narrative of hominin evolutionary history. Furthermore, cooking has become integral to our social and cultural dynamics. Greater comprehension of past cooking practices will connect us to our shared past both behaviorally mid biologically.
This paper will first review the long history of ostrich egg exploitation in the archaeological and ethnographic records. Next, it will discuss the energetic benefits of cooking mid how those are integrated into an optimal foraging strategy. Previous studies of eggshell taphonomy mid thermal alteration with be reviewed, with the experimental methodology informed by these subsequently described. Finally, the distinct patterns of color and morphological changes that result from various types of heating will be described mid the implications for archaeology specifically and for the broader understanding of our shared human past.


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Background
Ostrich Eggshell at Archaeological Sites
Given the consistent evidence that ostrich eggs have been a component of Paleolithic subsistence strategies, it is surprising that more attention has not be paid to their interpretation. Roche et al. (1999) document some of the oldest evidence for egg exploitation with shell fragments in close association with Oldowan industry lithics at a Lake Turkana site estimated to be 2.34 million years old. Dominguez-Rodrigo et al. (2009) mention an abundance of ostrich eggshell (OES) at the Bells Korongo site at Olduvai, but express uncertainty as to whether it was hominin-camivore assemblage or the remains of a nesting site, though another source describes the OES as unusually plentiful (Diez-Martin et al., 2009). The Lower Paleolithic site of Zhoukodian, inhabited by Homo erectus, represents one of the earliest sites with charred eggshell (Boaz & Ciochon, 2004). Middle Stone Age sites along the Western mid South Cape of South Africa more definitively identify the presence of eggshell fragments as probable refuse from subsistence activities. At Ysterfontein along the Western Cape, more than two kilograms of ostrich eggshell fragments were recovered from layers dating between 33 mid 70 kya in association with stone tools, hearth features, mid other probable food debris (Halkett et al., 2003), although the OES was located several meters away from the thermal features. Texier et al. (2010, 2013) and Steele and Klein (2013) likewise describe the presence of burnt shell fragments in the same stratigraphic layer with hearths, ash dumps, and other features indicative of controlled fire use at Diepkloof rock shelter (also located on the Western Cape), dated to 60 kya. Robbins et al. (1996) likewise report burnt ostrich eggshell fragments, along with a broad range of other faunal material and lithics, in dense charcoal layers dating to between 11 and 30 kya at the Late Stone Age site of


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Drotskys Cave in the Western Kalahari. They specifically note the charring of shell fragments as indicative of cooking, although with no suggestion of a specific cooking technique. By sheer mass, however, the Apollo 11 Rockshelter represents one of the largest deposits of ostrich egg, with 11 kg comprising more than 15,000 engraved, unengraved, and burnt fragments across the Middle mid Late Stone Age assemblage (Vogelsang, 2010). The authors posit the majority of the fragments to be the result of artisanal activity or the remains of flasks, although Murray-Wallace et al. (2015) note divergent patterns of racemization that indicate fragments were either reworked or exposed to greater temperature variation, suggesting multiple utilization strategies. Furthermore, some of the burnt fragments from Diepkloof are engraved and represent some of the oldest human art (Texier et al., 2013). The most common symbolic use for OES is in the form of beads. For example, Kandel and Conrad (2005) describe a collection of more than 2000 beads in a variety of colors mid in a variety of stages of production from sites at Geelbek Dunes in South Africa. Pei et al. (2012) report OES beads at mi Upper Paleolithic site in China dated to approximately 35 kya. Similarly, the Holocene site Chikhen Agui Rockshelter in Mongolia contained clusters of OES beads, as well as a collection of unmodified fragments (Derevianko et al., 2008). Other sites in Mongolia mid Northern China show persistence of ostriches and human exploitation thereof as late as 8.9 kya (Janz et al., 2009).
Natural Occurrences of Ostrich Egg in the Archaeological Record
Much as hominins value ostrich egg as a food source, carnivores will target eggs. Some such as jackals or Egyptian vultures will break and consume the eggs at or very near to the nest when hens are absent (Magige et al., 2009). Larger animals such as hyenas or lions may consume them in place, but are capable of transporting them (up to 7 km in some cases


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(Kandel, 2004)) and will accumulate them with other prey at denning sites (Henschel et al., 1979; Skinner & van Aarde, 1991). Consequently, OES is present in many prehistoric carnivore accumulations (Scott & Klein, 1981). For example, Rector mid Reed (2010) describe a carnivore den assemblage attributed to the brown hyena {Hyaena brunnea) in one of the Pinnacle Point caves (PP30), located in Western Cape, South Africa, with large quantities of fragmented ostrich eggshell. Similarly, Kandels (2004) analysis of diagnostic carnivore damage to eggshell was used to establish that OES accumulations from Geelbek Dunes as the result of hyena scavenging. The other major natural accumulator of eggshell is nesting sites themselves. Ostriches will share communal nests, with several hens laying in a single nest (Bertram, 1992). Additionally, these nesting sites may be reused, resulting in large shell accumulations (Bertram, 1992). Such sites have been posited to be natural explanations for OES assemblages lacking direct evidence of human interaction (i.e. subsistence, engraving) (Dominguez-Rodrigo et al., 2009).
Ostrich Egg Use in the Ethnographic Record
Indeed, ostriches and their eggs continue to be an important component of life among hunter-gatherers in the Kalahari, including the !Kung, G/wi, mid Ju/hoansi (Hollmann, 2001; Lee, 1984; Silberbauer, 1981). Although the birds themselves are not commonly hunted (Lee, 1984), the eggs are still prized as a food source, especially when seasonal game migrations make other food sources scarce (Hollmann, 2001). Eggs are by and large described as being eaten cooked; in the absence of ceramic or metal cookware, they are generally prepared by placing whole eggs in hot ash (Cott, 1953) or simply by having the contents poured into a coal-lined depression in the ground (Wannerburgh et al., 2000). Variation in human processing of other ratite (large flightless birds including ostriches, emus, rheas, and


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cassowaries) eggs has been documented as well, both archaeologically and ethnographic ally. Medina et al. (2011) report significant accumulations of burned Rhea eggshell fragments at pre-Hispanic sites in central Argentina, as well as more contemporary ethnographic reports of the cooking of eggs over hearths or hot coals. Similarly, Wrangham (2009) reports populations in Tierra del Fuego burying eggs on the edge of campfires. Likewise, some Australian indigenous populations have also been documented as cooking their ratite eggs by burying them in hot sand or ash (Basedow, 1925). Aside from a contemporary travelogue (Rasmussen, 2014), Hollmann (2001) is the only source to describe the consumption of raw
egg-
The shells themselves are also commonly utilized. After being emptied of their contents, the empty shells are very durable, with a breaking strength of 55 kg (Sales, 2006). This allows their use as water canteens that are the primary method of transporting water across the landscape of the Kalahari during the wet season (Silberbauer, 1981). Egg is also still a favored symbolic medium. Necklaces and other adornments with shell beads are valued personal adornments and are often exchanged as gifts (Marshall, 1976). Finally, ostrich eggs figure into the mythology and supernatural beliefs of groups in the area. Hollmann (2001) describes how in San iconography ostrich eggs represent a type of good fortune associated with hunting mid food procurement success. On a broader scale, the exchange of goods to create and maintain social bonds in hunter-gatherer societies is well documented. Wiessner (1982) describes a manifestation of this in the hxaro system of mutual reciprocity among the !Kung San of the Kalahari. This delayed exchange of gifts strengthens social ties mid allows for the minimization of risk through sharing of resources. On a regional scale, the social ties created by hxaro can be used to facilitate distribution of localized


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resources, organize marriages, and manage stress caused by large scale environmental changes (Mitchell, 1996). These networks of exchange even persist beyond the death of an individual, with descendants assuming the deceaseds obligations (Wiessner, 1986).
As described above, ostrich products, primarily beads but also feathers mid canteens, have been documented ethnographic ally as key items in exchange systems (Lange, 2006; Miller, 1996; Wiessner, 1982). When artifacts have limited geographic availability, their presence in exotic locations well beyond foraging ranges can be used as an indicator of exchange. Establishing the presence or lack thereof of ostriches in a given region can be limited by the fossil and historical records, mid some regions can ultimately be deemed to have lacked ostrich populations (Miller, 1996). In regions where the birds are common, however, exchange of such goods can be more difficult to establish. While ostrich eggshell that has been worked into beads or engraved can more easily be assumed to have exchange value, fragments that lack such markers have been largely ignored. Isotopic analysis has previously been applied to eggshell as a dating method (Brooks et al., 1990; Murray-Wallace et al., 2015) and as a component of paleoclimate reconstruction (Johnson et al. 1997, Lee-Thorp mid Ecker 2015). More recently, isotopic analysis has been applied to ratite eggs to track human exploitation mid transportation (Giardina et al., 2014; Hodgkins et al., in press) across the landscape. Nevertheless, when a site presents tens of thousands of fragments as in the case of Apollo 11 Rockshelter (Vogelsang et al., 2010), determining which should be subjected to costly and time-consuming isotopic analysis can be difficult in the absence of indicators of human activity. This study will show that coloration patterns on heated eggshell can help differentiate anthropogenic ally modified ostrich eggshell from naturally deposited eggshell modified by bushfires.


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The Rationale for Cooking
Optimal foraging theory provides a better understanding of the adaptive role of cooking. This analytical tool has been foundational in the quest to understand how human populations past and present, especially mobile hunter gatherers, construct their diets, and has been applied to populations over the world (Alvard, 1993; Byers & Ugan, 2005; Hawkes et al., 1982, 1991; Hill et al., 1987; Riley, 2012; Winterhalder, 1986; Zeder, 2012). As previously discussed, there is evidence that eggs have long been a valued resource with both burned mid unbumed ostrich eggshell (Robbins et al., 1996; Texier et al., 2010, 2013; Vogelsang et al., 2010) fragments preserved in the archaeological record and a diverse range of ethnographic descriptions regarding egg handling mid preparation (Cott, 1953; Lee, 1984; Wannenburgh, 2000; Wrangham, 2009). When considered through the lens of optimal foraging theory, it becomes clear that though raw consumption is possible mid occasionally documented (Hollmann, 2001), optimality theory suggests that cooking of ostrich eggs and, depending on cooking method, heating of the shell is to be expected after regular control of fire was established at approximately 1 mya (Bema et al., 2012).
In order to address why eggs would be cooked, we must first understand why it is that cooking is done at all. Wandsnider (1997) and Crowther (2013) provide the most proximate rationale for the practice of cooking. First, the heat treatment of foods can result in the reduction of toxins or other harmful chemical components or the elimination of harmful pathogens or parasites. Second, certain techniques (e.g. smoking) can increase the time until spoilage, allowing the food to be preserved beyond its natural usability. These reasons for cooking can be described as facilitating consumption of a given food.


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The final reason for cooking is that it acts as a form of pre-digestion. The effect of this is twofold. The first is that foods are softened by the cooking process, with the most obvious effect being that it facilitates consumption by infants or the elderly (Crowther,
2013). On a broader biological level, Wrangham (2009) notes that it reduces the energy expended by the body during digestion. The softer a food is, the less energy must be expended by the body to break down mid absorb it. Thus, although the total amount of calories absorbed from the foods themselves may remain constant, the investment by the gut to obtain those calories is reduced, resulting in a greater energetic profit. Furthermore, thermal processing techniques (i.e. cooking) have been shown to increase this profit to a greater degree than non-thermal ones (e.g. pounding meat to tenderize it) (Carmody et al., 2011; Zink et al., 2014). The second effect is that cooking fundamentally alters the chemical structures of foods, rendering them into forms more readily received by the body (Wandsnider, 1997). The degree to which vitamins, macronutrients, and other substances can be absorbed in the digestive process is known as bio availability. Cooking often promotes processes such as denaturing and hydrolysis which weaken or reduce in size the molecules of the substance, allowing more of it to be absorbed during digestion (i.e. increasing the bio availability) (Wandsnider, 1997), and giving cooked foods superior nutritional content. Several studies (Carmody et al., 2011; Davies et al., 1987) have demonstrated that cooking beef denatures its proteins and greatly increases available mid absorbed protein, up to a factor of four in some cases. Similarly, cooking of tubers has been shown to increase their digestibility (Wandsnider, 1997). Cooking increases the energy output of a given food source by reducing the energy expenditure of digestion, increasing the bioavailable nutrients, or
both.


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Cooking ostrich eggs does not immediately seem to be worthwhile, as the process does not have some of the more obvious benefits of cooking such as safety, preservation, or texture improvement. The eggs are safe to consume uncooked, and if anything, cooking changes the texture to a more robust consistency. Likewise, cooking does not significantly extend the edibility period of eggs, as the shells naturally provide a degree of protection mid the freshness period of the unbroken egg is therefore a matter of weeks rather than days (Wrangham, 2009). Nevertheless, there is a significant benefit. While the overwhelming majority of anthropological and archaeological studies of the effects of thermal processing have been focused on meat and tubers (Zink et ah, 2014) (dietary staples for much of the world), some work in the field of nutritional science has been done on egg. Evenepoel et al. (1998, 1999) demonstrated that there is a significant increase (approximately 40%) in protein bio availability between raw and cooked egg. Protein is the most prioritized macronutrient in the human diet and it has been shown that above the minimum necessary dietary threshold, proteins advantages continue to scale with no obvious limit to benefits, and therefore hunter-gatherers will seek to not only pursue protein, but preferentially seek out resources that maximize its acquisition even at the expense of some caloric output, and this phenomenon will not occur with other macronutrients such as carbohydrates (Hill et al., 1987). It follows then that if humans will seek to maximize resources in the foods that they pursue, they will also seek to maximize it in the foods they acquire. If the maximization of energetic mid nutrient returns is always preferable, then cooking would be expected to be performed when there is a benefit.
It might be argued that the additional benefits accrued by cooking are outweighed by the expense incurred by cooking, as raw ostrich egg already seems to represents an ideal food


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source (Wrangham, 2009). The search cost is relatively low, as nesting sites are static compared to mobile animal herds and as such, the only investment is in locating that site. Furthermore, they incur no pre-transport processing costs in the way that a large animal kill would. The only required processing is cracking a hole through which the contents are drunk; chewing would not even be necessary. Furthermore, ostrich eggs provide an entire days worth of calories for a single adult hunter-gatherer (Lee, 1984) as well as a broader range of necessary proteins in greater quantities than practically any other common food (Wrangham, 2009).
Thus, cooking can definitively increase the output of foods (Carmody et al., 2011; Wand snider, 1997; Wrangham, 2009). Optimal foraging theory considers cooking to be a technological processing technique (Lupo, 2006). Bright et al. (2002) report that technology will be applied in order to reduce handling time of foods in order to maximize net gain, providing the example of increased milling stone production and a shift towards a more efficient design in order to reduce handling time of seeds and ultimately increase energy profit. If strategies that apply technology to decrease energy expenditure and increase the net energy or nutritional output of a given resource are considered optimizing, then those that apply technology in order to increase the energy output of a resource should be considered the same as those that reduce handling time when the additional output is greater than the additional input. Fire is a technology and therefore, all else being equal (i.e. when safety or preservability are controlled for), cooking should be considered to be optimal when it produces a net gain in energy output.
Hill et al. (1987) and De Vynck et al. (2016) both cite cookings low cost in their models. The former notes that after a short preparatory process, the cooking of meat lasts for


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several hours with minimal participation needed. This allows other productive activities to be conducted while cooking occurs (Kelly, 2013). Furthermore, this cooking is done during the night, when the handling time-cost does not as strongly impinge on other activities.
Similarly, the latters study of shellfish exploitation economics also cites a relatively passive cooking process, as well as a division of labor between foragers mid cooks, mid the idea that post-cooking extraction does not affect the foraging calculus. Rather, they prioritize the energy expenditure of firewood gathering and that of tending to the cooking process. Wrangham and Carmody (2010) argue that fires are likely to be present in hunter-gatherer camps independent of cooking needs as predator deterrents, rendering the cooking specific wood gathering minimal. For some foods, as is the case with De Vynck et al.s mollusks, this might be enough to offset cookings benefits, but that cannot be assumed for all items. Furthermore, while Kelly (2013) acknowledges that some cooking techniques such as stone boiling require enough constant attention to merit consideration in terms of expense, most do not. The egg cooking methods described in the ethnographic literature fall into the less labor intensive category.
Previous Studies of Eggshell Taphonomy
Due to its relative fragility (especially for smaller birds), eggshell has not been the subject of a large body of taphonomic inquiry in the same way as other zoo archaeological materials such as bone. While Kandel and Conrad (2005) and Texier et al. (2010) cursorily describe experiments that indicated color variation in OES as a result of heating, Janssen et al. (2011) were the first to investigate in some depth the taphonomic effects of heating avian eggshell, conducting a battery of laboratory experiments to establish the range of variability associated with different heating intensities mid times. They exposed OES fragments to


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progressively increasing temperatures (200-800C) over a range of exposure times (5-60 minutes) in an industrial kiln. Fragments were then assessed in terms of mass mid coloration. The authors observed a broad range of colors associated with the variation in temperature including orange, yellow, brown, blue, mid gray, as well as pronounced decreases in mass at approximately 470 and 730C. They suggested that the majority of observed color change was a function of exposure temperature rather than exposure time, with most changes occurring within 5 minutes, mid little occurring past 30 minutes. Their observations regarding morphology are limited; they note the occasional destruction of the inner and outer layers (not explicitly described, but likely referring to the mammillary layer mid cuticle respectively) as well as some flattening and inversion of the curvature of fragments exposed to higher temperatures (600C and higher). Given that only two fragments were subjected to each time/temperature combination, it is difficult to extrapolate the described variation as representative.
Texier et al. (2013) made a more systematic approach to burnt OES fragments in order to interpret engraved fragments from the Diepkloof rockshelter assemblage. Their previous pilot work (Texier et al., 2010) demonstrated a range of colors produced by thermal alteration, explicitly mentioning orange, red, black, mid gray. In an effort to understand more precisely the color changes in burnt OES, the authors heated fragments to nine temperatures between 100 and 480C for twenty minutes, recording the resultant changes in mass, thickness, mid coloration based on the Munsell system. They describe a color progression from unbumt to yellow, red, brown, gray, and blue gray as temperature increases, as well as fragmentation of the inner and outer surfaces (once again, presumably the mammillary and palisade layers) at temperatures exceeding 500C. Furthermore, they deem mass and


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thickness to be poor parameters for analysis. Once again, however, their sample is small, with only three fragments heated to each temperature.
Collins and Steele (2017) provided the most comprehensive study to date of thermal alteration of OES, seeking to fully develop a model for the effects of thermal alteration on shell color. They began by replicating Janssen et al. (2011) mid Texier et al.s (2013) kiln experiments, observing very similar patterns of color change, though notably they were not able to produce deep red or black coloration. A marked increase in friability was noted above 400C. Crucially, the second phase of their study involved heating OES with a fire. Three fragments were exposed directly to the fire, while ten were buried in sand at depths of 5-8 cm below the fire. The authors noted rapid alteration in terms of time for the fragments exposed directly to the fire, but with distinct color gradients suggestive of rapid dissipation of heat through the air. Collins mid Steele elaborate on six color categories based on exposure temperature: unbumt, yellow, red, black, iridescent, and grey-white. While Collins and Steeles work provides an important baseline, their study can be expanded in several ways. First, sample size can be increased. Second, subsurface temperature recordings could be taken on a more continuous basis to provide information regarding rates of temperature change, rather than at long intervals. Furthermore, temperature probes employed by Collins and Steele suffered failures and were unable to measure temperatures far in excess of 200C, opening the possibility of more precise measurements. Finally, in addition to the analysis of already fragmented OES, thermal alteration of whole eggs with liquid still inside could be tested.
Focusing on form rather than appearance and heating via cooking specifically, Taivalkoski mid Holt (2016) subjected chicken eggs to a variety of cooking methods in order


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to determine whether those left characteristic damages to the micro structure detectable by scanning electron microscopy (SEM). They prepared eggs through boiling at two different durations, baking in an electric oven at 177C, and baking on hot coals for 10, 15, and 20 minutes with starting temperatures recorded at 520C. The eggs were fragmented and, after cleaning, examined through SEM for damage to the mammillary layer. They observed no apparent change in micro structure for boiled or oven baked shell compared to raw shell, but noted delamination in fire-cooked fragments. Unfortunately, Taivalkoski and Holts (2016) sample size was small; only two eggs were given each boiling treatment and oven baked, and only one was fire cooked for each time interval, meaning that the range of variation was limited. Furthermore, they only seem to consider two disparate ends of a temperature spectrum, contrasting the relatively low temperatures with the high ones of fire with no intermediate method or control. Changes in color were only noted in passing, which seems to be a missed analytical opportunity given those disparate exposure temperatures.
Miller et al. (2016) examined burnt shell fragments from the extinct megafaunal bird Genyornis newtoni from Australia. They tested partially blackened fragments with amino-acid analysis, finding total amino acid decomposition in those blackened areas, with progressively higher concentrations moving away from the blackening. They observed color variation commensurate with the change in amino acid decomposition, and attributed this to anthropogenic heating, suggesting that wildfires would not produce significant differential effects within mid between tightly clustered fragments as in the Australian record. Rather, they suggest cooking methods such as pit roasting or cooking on coals that have low overall exposure temperatures but may expose the eggs to small, acute heat sources such as single embers or coals would result in intense but localized discoloration. In general terms however,


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they propose that the most effective cooking methods moderate heat exposure to prevent rupture of the eggs, resulting in little alteration of shell color or morphology.


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CHAPTER II EXPERIMENTAL STUDY Materials & Methods
In this study, two distinct tests were run. The goal of the first test was to establish the effects of heating on shell fragments at and below the surface. The goal of the second test was to determine the effects of cooking on whole ostrich eggs. The first used ostrich egg fragments purchased from Floecks Country Ostrich Farm (https://www.floeckscountrv.com/) in Tucumcari, NM. For the second, eleven whole eggs were purchased from Ostrichland USA in Solvang, CA (https://www.ostrichlandusa.com/). In the second test, one whole egg was reserved for other research and two whole eggs showed signs of damage in shipping and were excluded from this experiment. Thus, eight whole eggs were used in the second experiment. Given that analysis was conducted on shell fragments, and each egg was capable of producing enough fragments for a sufficient sample for statistical testing, this was deemed a sufficient number of eggs. Firewood was pine purchased from a local firewood seller. The sandy soil blend used upon which the fires were built and in which some eggs were buried was purchased from a hardware store. Two fires were constructed in permanent metal campground fire rings and the third was constructed in a freestanding bum barrel approximately 26 inches in diameter. No artificial accelerants were used to start the fires; instead, a combination of dryer lint and small pine shavings was employed. Temperatures were measured with Omega TJ-36-CAIN-14G-24 temperature probes (rated to 1372C) and recorded with Omega RDXL4SD and Sper Scientific 800021 dataloggers.
For the first test (heating of OES fragments), the fire rings were filled with sandy soil. To simulate alteration of buried OES, handfuls of fragments were scattered at approximately


19
three centimeters below the surface such that some fragments were oriented with the exterior facing upwards mid some downwards. Furthermore, some were oriented with varying degrees of verticality. These measures were taken to reflect the variety of orientations that could result from post-depositional turbation. A temperature probe was inserted through a hole in the fire ring and placed such that the measuring portion of the instrument was at three centimeters subsurface (Figure 1, top). Fragments were then covered with soil. The other temperature probe was situated with the measuring portion of the device in approximately the center of the fire at the surface (Figure 1, bottom) with the location adjusted periodically to maintain position in the hottest part of the fire. Temperature readings were logged automatically at 30 second intervals. This provided a sufficient number of temperature data points and given that broader temperature trends were the focus, more frequent sampling would have been redundant. To simulate disposal or exposure to a brushfire, handfuls of fragments were scattered directly into the fire once the larger logs had ignited. These fires were allowed to bum for approximately 100 minutes at which point logs and coals were removed mid fragments were removed and excavated.
The second test (heating of whole eggs) was split into multiple experiments. In the first, sandy soil was put into the bottom of the bum barrel, with two eggs each laid on their sides such that the highest points were three and five centimeters below the surface (Figure 2). Temperature probes were place at five centimeters subsurface via a hole in the barrel and


20
Figure 1: Fragments set at three centimeters subsurface with temperature probe (top) and test in progress with probes at surface and three centimeters subsurface (bottom).
:Fm


21
angled from above to rest at three centimeters subsurface. The barrel was then filled to the rim with sandy soil. A third temperature probe was rested on the surface as in the fragment tests. The fire was then ignited and allowed to burn for approximately 100 minutes. The logs and coals were removed, mid the buried eggs were turned such that the side that previously faced the surface now faced downwards (consistent with ethnographic descriptions of egg cooking (Miller et al., 2016; Taivalkoski & Holt, 2016; Wrangham, 2009)). Eggs were then reburied and a new fire was built which was allowed to bum for approximately 65 minutes.
In the second experiment, the remaining hot coals from the first experiment were shifted to one half of the surface. Two eggs each were then placed on the hot coals mid on the heated soil (Figure 2). One of the eggs on the coals cracked and disgorged its contents soon after it was placed. It was removed, and a hole was created in the other egg placed on the coals to relieve pressure mid prevent further losses. The remaining eggs were rotated in place approximately every five minutes until the surface temperature cooled to under 100C (approximately 40 minutes) at which point they were removed and the buried eggs were excavated.
In preparation for analysis, a hole was made in the whole eggs with a hammer mid screwdriver and the contents removed. Shells were then fragmented with the side of a hammer, with a towel used as padding to diffuse the impact. Any remaining solidified contents were removed. Fragments from immediately around the drain hole were discarded to avoid misinterpretation of the damage from fragmentation as thermally induced damage. All fragments were cleaned with tap water to remove surface dirt and ash. Drying was accomplished with a combination of paper towels and air drying.


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Figure 2: Whole eggs for subsurface cooking tests, pre-burial (top) and whole eggs for surface cooking tests (bottom).


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In total, 325 heated fragments were recovered (see Table 1 for a breakdown by heating category). Thirty-two unbumt specimens were also recorded as controls, bringing the total number of fragments to 347. Specimens were examined via traditional microscopy at 7-40x magnification mid with a Dinolite digital microscope at 25-50x magnification. Fragments were assessed and classified in terms of color and morphology. Exterior color was assigned to one of seven ordinal categories (from lowest associated exposure temperature to highest, based on Texier et. al (2013) and Collins mid Steele (2017)): off-white, pale yellow, orange, brown, black, blue-grey, and white. The presence or absence of a color gradient was noted, and those with a gradient were assigned to the category of the highest exposure temperature color present. Exterior gloss was rated on a 0-3 scale, zero being matte, one being mildly glossy, two being very glossy, mid three being iridescent. Morphology was assessed in terms of the presence, presence with damage, or absence of the exterior and interior mineral layers of the shell: the mammillary or cone layer mid the cuticle layer. Flattening was assessed on a 0-2 scale, with zero representing normal curvature, one representing flattening of the shell, and two representing inversion of the normal curvature. Data regarding the morphology and coloration of the membranes was deemed not to be reliable. The relative fragility of the membranes mid their propensity to pull away when solidified egg contents were removed made it difficult to obtain accurate results. The admission of the source farmer for the fragments that she often removed membranes before shipping further compromised data gathering.
Results
Results revealed that shell morphology only changes at the highest exposure temperatures. Surface burned fragments showed consistent damage, with 47.1% displaying


Fragment Counts by Preparation Tvpe
Unburnt Fragments, 3 cm Subsurface Fragments, Surface Whole, Hot Coals Whole, Hot Soil Whole, 3 cm Subsurface Whole, 5 cm Subsurface Total
Count 32 48 87 26 44 50 60 347
Table 1: Fragment counts by heating type.


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damage to the cuticle or lacking it altogether (Figure 3, top). Likewise, 60.9% showed alteration of the mammillary layer, mid it had been completely destroyed in 32.2% of specimens (Figure 3, bottom). Furthermore, 40.2% of surface burned fragments were flattened, with a further 18.4% having inverted their natural curvature (Figure 4). In contrast, the only other category to show structural alteration was the fragments heated at three centimeters subsurface. Among those only 6.3% showed damaged to the cuticle, 12.5% showed damage to the mammillary layer, with 1 specimen (2.1%) having the mammillary layer destroyed completely. Additionally, only 6.3% showed any flattening, and none were inverted. All other fragments in the other categories showed no structural signs of thermal alteration.
Color proved to be much more indicative of burning circumstances (Figure 5). Fragments burned on the surface showed a broad range of colors, but tended to concentrate towards the upper end of the spectrum, with 57.5% falling into the blue-grey and white categories. The fragments burned at three centimeters showed similar breadth in their distribution, but are skewed towards the lower end of the spectrum with 56.3% of fragments categorized as orange or brown, and 89.6% categorized as brown or below. The fragments of the whole eggs showed much less variation. The preparation method with the most intense color change turned out to be coal cooking. When cooked that way 53.8% remained apparently unaltered, 30.8% reached orange, and only 11.5% were classified as brown. Among those cooked at three centimeters subsurface, no fragments exceeded orange. Likewise, cooking on hot soil and at five centimeters subsurface produced only off-white and pale yellow fragments. Unlike other variables, glossiness showed no obvious patterning related to heating type or color category, so further testing was necessary. A Fishers Exact


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60-
50-
40-
Heating Type Unburnt
Fragments, 3cm Subsurface Fragments, Surface Whole, Hot Coals Whole, Hot Soil Whole, 3cm Subsurface Whole, 5cm Subsurface
30-
20-
10
Undamaged
Damaged
Absent
Cuticle Presence
Heating Type Unburnt
Fragments, 3cm Subsurface Fragments, Surface Whole, Hot Coals Whole, Hot Soil Whole, 3cm Subsurface Whole, 5cm Subsurface
Undamaged Damaged
Mammillary Presence
Absent
Figure 3: Cuticle (top) and mammillary (bottom) layer damage patterns by
heating type.


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C
3
O
O
Heating Type Unburnt
Fragments, 3cm Subsurface Fragments, Surface Whole, Hot Coals Whole, Hot Soil Whole, 3cm Subsurface Whole, 5cm Subsurface
Normal Curvature
Inverted Curvature
Flattening
Figure 4: Flattening patterns by heating type.
Fragment Counts by Coloration, Fragment Test
Fragment Counts by Coloration. Whole Egg Test
Heat ng 1 ype
Umcatcc
3cir 5ubsu"ace USu-'acs
Color Stages
Color Stages
Figure 5: Color patterns by heating type for fragment tests (left) and whole egg tests (right).


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Test based on a 10,000 sample Monte Carlo (selected because of low expected values) was performed, with subsequent examination of the standardized residuals which showed associations between gloss mid both heating type and color category (p=. 000). For heating type (Table 2), the strongest relationships exist between iridescence and the higher exposure temperature heating types. For color (Table 3), the strong association was seen between brown, black, blue-gray mid iridescence. The unbumt control shells tended towards some degree of gloss, but not a matte or iridescent appearance. The eggs cooked whole on hot soil show mi unusually strong trend towards being both matte and pale yellow. Given that this is not reflected by the unbumt shells or shell heated by hot coals (with the closest exposure temperature), there is a strong possibility this is related more to the natural color and texture variation the eggs used in the experiment than the heating circumstances.
Recorded temperatures showed distinctive ranges associated with distance from the heat source (Figures 6-9). Surface temperatures (after the first five minutes) fluctuated greatly, ranging from 93.2C at the end of the surface cooking test to 916.2C during the middle fragment testing in windy conditions, with an average temperature of 587C. In comparison, subsurface temperatures were slow to rise. At five centimeters subsurface, more than 100 minutes was required to raise the temperature from its starting point of 19.7 to its maximum 81.2C. Temperatures at three centimeters were more responsive, ranging from 76.2 to 568.9C, but retained an average measurement much lower than the surface tests at
299.3.


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Heating Type Exterior Glossiness Crosstabulation
Standardized Residual
Exterior G ossiness
Matte Mildly Glossy Glossy Iridescent
Heating Type Unbumt .5 -3.0 3.6 -2.3
Fragments, 3 cm -2.4 -.6 .3 2.6
Fragments, Surface 1.5 -2.7 -2.1 5.3
Whole, Hot Coals -2.0 .3 1.4 -.6
Whole, Hot Soil 8.1 1.1 -4.2 -2.7
Whole, 3 cm -2.8 2.2 1.7 -2.8
Whole, 5 cm -3.1 2.8 .7 -1.8
Table 2: Residual values for Fishers Exact Test searching for association between heating
type and exterior glossiness.
Color Exterior Glossiness Crosstabulation
Standardized Residual
Exterior G ossiness
Matte Mildly Glossy Glossy Iridescent
Color Unbumt -3.6 2.9 2.4 -4.1
Pale Yellow 6.2 -1.3 -.8 -3.1
Orange -2.5 .7 .5 .7
Brown -1.9 -2.5 .6 4.2
Black -1.2 -1.1 -.5 3.5
Blue-Gray -.7 -.7 -3.1 6.6
White 6.8 -1.7 -2.7 -.3
Table 3: Residual values for Fishers Exact Test searching for association between color
and exterior glossiness.


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Fire 1 Temperature
800
200
100
o
Surface
10 15 20 25 30 35
Time in Minutes
40
Figure 6: Fire 1 temperature over time.
Figure 7: Fire 2 temperatures over time.


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Fire 3 Temperatures
1000
u
I:
i -0 ______________________________________________
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Time in Minutes
Surface
3cm Subsurface 5cm Subsurface
Figure 8: Fire 3 temperatures over time.


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Discussion
The temperature profiles for each of the hypothetical circumstances were shown to be radically different. Subsurface temperature was much slower to rise, taking more than fifteen minutes to exceed 300C from ambient air temperatures of approximately 20C at the three centimeter depth. Even when the third fire was restarted (after turning the buried eggs) with the soil already having been heated, it took approximately seven minutes to return to 300C. The temperature at five centimeters subsurface failed to reach even 100C after 100 minutes of heating. Brushfires, though they may produce temperatures in excess of 1200C (Dennison et ah, 2006), move very rapidly. For example, Shea et al. (1996) documented brushfires in savannah landscapes in South Africa and Zambia moving at between 0.2 mid 0.7 meters per second, with residence times of 1 to 11.5 seconds. This means that a natural fire is extremely unlikely to bum in a single location for a long enough period of time to result in significant alteration of buried OES. Any variation in OES based on the capacity of various soil types to hold mid transmit heat is negligible in comparison to that created by depth/distance from the heat source. The effects of a brushfire on surface fragments is more difficult to interpret. A fire with higher temperatures or a longer residence time would likely result in the destmction of the eggs. If the fire were cooler or moved at a higher speed, exposure to the fires hottest part, the fire front, would be brief, and any alteration would be the result of residual fires left behind the front, the temperatures of which could be up to 600C lower (Dennison et al., 2006). This suggests that while many OES fragments would still experience delamination, exposure to bmshfires may not guarantee stmcture damage. A basic knowledge of wildfire ecology in a sites environment could prove useful for taphonomic interpretation.


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Buried OES does show the potential to be altered by anthropogenic fire. This may or may not be intentional. As Collins and Steele (2017) suggest, it may be a deliberate strategy to effect a particular color in shell to be used in bead-making. Alternatively, later fires built at sites of recurring occupation may alter buried shell that was deposited in an unbumed state. This process may even act on natural deposits, perhaps a nesting site or carnivore accumulation. Anderson et al. (2005) related the case of a New Zealand rock shelter wherein burnt moa shell was associated with hearths also found at the site mid interpreted as being the result of cooking by Maori travelers. Subsequent carbon dating revealed instead that there was a several hundred-year gap between the shell and the charcoal in the hearths, with a subsequent hypothesis surmising charring shell from a defunct nesting site by later human inhabitants, suggesting that while OES can be an important line of evidence, the presence of other archaeological material is necessary to verify human habitation. Nevertheless, the presence or absence of other archaeological material in the same context may not be definitive determinant of human interaction. Johnson et al. (1997) reported that ostrich eggshell fragments may be more susceptible to post-depositional movement than larger faunal elements. When the OES from Equus Cave was radiocarbon dated, most of it was found to be out of its proper stratigraphic context, with both upward and downward mixing occurring. Other faunal material was not shown to be disturbed in a similar way, suggest that OES is uniquely vulnerable to certain taphonomic forces (posited by the authors to be small mammal turbation.)
Cooking was shown to be unlikely to produce significant alteration to OES. This is due to the delicate balance in exposure temperature that must be achieved between heat that is sufficient to cook the egg in a timely fashion but not so intense as to rupture the egg. One


34
of the eggs buried at three centimeters did crack and vent some contents to the surface, but ceased leaking quickly after. Additionally, one egg placed directly on the coals ruptured quickly. A hole was made in the egg on the coals, but this inhibited the degree to which it could be rotated. Lack of experimenter savvy in the nuances of fire-cooking eggs could be at least in part responsible for these failures, but cooking on coals mid burial at three centimeters seem to be those that strike the best balance between risk and efficiency. Given that little alteration was documented with this amount of error, it is possible that more skilled cooks could expose the egg to higher temperatures and produce deeper shell colors without structural failure. It is however notable that even though these cooked eggs showed color change, there was markedly less iridescence than in fragments heated at the same depth. This may simply be the result of variation in exposure temperature, but other factors such as the insulating effects of egg contents or a continuous shell may be in play; in either case, further investigation is required.
The results of the fragment component of this study are consistent with Collins and Steele (2017), with a similar range of colors observed. Some discrepancies are to be noted, however. Collins and Steele dub the fifth of their six categories as iride scent, and link that visual quality with blue or gray exteriors. This study finds color and iridescence to be less directly linked. While iridescence was observed in 65% of fragments labelled blue-gray, it was also seen to be associated in brown mid black fragments (Figure 10). In further contrast, the presence of black fragments was documented here whereas Collins and Steeles experiments failed to produce them. They were however the least represented category, accounting for only 2.9% of all fragments. Given the continuum of color from dark brown to black or black to gray sections, it is suggested that blackening represents a specific exposure


35
Figure 10: Iridescent fragment categorized as brown.


36
temperature between those for dark brown and gray. This temperature would seem to be correlated with exposure temperatures greater than those at 3cm subsurface and at the surface. The lack of fragments at that depth could explain their absence in both studies. Proposed alternate factors such as the available oxygen or other organic compounds cannot, however, be discounted. Conversely, this study did not observe a lightening of coloration between the orange and blue-gray stage seen in Collins mid Steeles kiln phase; rather further darkening from orange to brown and black before arriving at gray was seen. This would seem to confirm their supposition that some as yet unknown factor that acts between approximately 300 and 500C is responsible for the lack of deep red fragments in kiln experiments.
The findings of this study call into question Miller et al.s (2016) suggestion that a sharp thermal gradient on a single shell fragment or among closely related fragments is in and of itself diagnostic of cooking. Though the exact range of color variation in thermally altered Genyornis newtoni egg is unknown mid amino acid analysis was beyond the parameters of this study, sharp color gradients were seen in both buried mid surface burned fragments in addition to those from coal-cooked eggs (Figure 11). This, along with the temperature data, suggests that though wildfires are unlikely to produce such patterns of alteration, alteration by anthropogenic fire would not necessarily have to be intentional to produce this patterning. If, however, such sharp gradients are contained solely within a single fragment (Figure 12) that may indicate a very focused heat source affecting a very localized part of a whole egg, a scenario which only makes sense in the context of cooking. Wildfires would be incapable of producing such a localized effect. With heat dissipating more gradually in soil than in air, unintentional heating of buried fragments would produce


37
Figure 11: Fragments showing similar color gradients. Heated by hot coals (top), burnedfragmented on the surface (middle), and burned fragmented at three centimeters subsurface (bottom).


38
Figure 12: Fragments of hot coal heated eggs displaying contained gradients, with color gradients encompassed on single pieces.


39
minimal, if any gradients on horizontally oriented fragments and unidirectional gradients (like those in Figure 11) on vertically oriented fragments. Therefore a bidirectional contained gradient would be unique to exposure in air to a localized heat source. Unfortunately, this acute heat exposure is exactly the source of structural weakening, meaning that post-cooking, shells would be likely to fracture at the location of such gradients, especially as their extremity increases), rendering them indistinguishable from other fragments with gradients (Figure 11).
Conclusion
While this study produced no smoking guns (so to speak) that could be used to identify the way in which any single OES fragment was heated, it did identify several overall trends in the temperature profiles of different circumstances in which OES could experience thermal alteration. Fragments heated above ground were generally blackened, gray, or white with significant damage or even complete destruction of the cuticle and mammillary layers. Fragments burned at three centimeters subsurface showed a broad range of colors from unbumt to blue-gray, but little in the way of morphological damage. Finally, eggs heated whole show minimal shell alteration, but does present the possibility of a characteristic contained gradient that will need to be investigated further.
A number of specific questions regarding the variation in heated OES still remain. Color gradients were observed on multiple preparation categories, reflecting the fact that thermal gradients were common both above and below the surface. The relative dissipation of heat through air as compared to dense media such as soil or sand could inform future studies; measurement of the steepness of a color gradient could be employed to identify


40
heating circumstances. Another future avenue of inquiry would be to examine in depth not merely the immediate effects of thermal alteration but its long term impact on preservation. Fragments exposed to the highest temperatures suffer apparent structural damage that would seem to decrease their survivability, but heating may weaken OES in ways that are not immediately apparent resulting in differential preservation. Further investigation into forces that would alter appearance such as soil staining and abrasion that may alter surface gloss should be investigated. In particular, manganese oxides, which has been known to create blackening in buried bone similar to burning (Shahack-Gross et al., 1997), could operate on OES in a similar fashion. The precise factors that resulted in the variation in this and other studies samples in terms of blackening, iridescence, mid production of ochre-colored fragments merit further analysis mid likely have associations with heating conditions.
Once these other factors are better understood, we can then begin to apply the knowledge of thermally altered OES variability to archaeo logical OES. For example, Texier et al. (2010, 2013) describe the altered OES fragments from Dipekloof as being colored dark red, orange, and brown. Combined with the fact that they were burned post-fragmentation (established through refitting) (Texier et al., 2010), this color pattern strongly suggests that these fragments were altered by a later anthropogenic fire while buried. Unfortunately, this cannot be as immediately applied to other sites as their OES is described in little detail in the literature, but there is potential for the examination of existing collections. Apollo 11 rockshelter would be ideal for this; the sheer amount of OES and its presence throughout the Middle mid Late Stone Ages would allow for study of diachronic patterns of egg exploitation. Furthermore, this method holds the potential to serve as a proxy for both human activity and control of fire. Zhoukodian provides an ideal test case. Initial research suggested


41
that the site was occupied by a behaviorally sophisticated Homo erectus possessing control of fire (Boaz et al., 2000; Weiner et ah, 1998). That proposition has been challenged, with Weiner et ah (1998) failing to detect other archaeological byproducts of fire such as ash or in situ hearth features. Boaz et ah (2000), among others, have posited that the faunal and hominin remains contained in the caves were largely the result of hyena predation, with only minimal human contribution. Identifying if the OES from the site was thermally altered and the source of that alteration could provide strong evidence for control of fire mid suggest more significant human occupation. Similarly, examination of the OES from Ysterfontein could strengthen its association with thermal features.
The understanding of egg exploitation patterns also has more general applications. As ostrich eggs are laid at a specific time of year, identifying cooked OES could provide a window into seasonal occupation patterns. On a broader scale, ostrich eggs can be consumed either raw or cooked. Locating cooking in the record could illuminate temporal and spatial patterns in cooking that could relate to cultural divisions in behavior, climate, and nutritional stress. Alternatively, canteens have been proposed to be exchange goods that passed through early social networks (Curtis Mare an, personal communication). Therefore, burnt OES that was not cooked but shows indications of being anthropogenic ally deposited can be sourced through isotopic analysis to lend insight into these trade patterns. Ostrich eggshell is a rich informational resource that is only now coming into its own and will continue to aid archaeologists as research into it continues.


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i TOWARDS AN INTERPRETIVE FRAMEWORK FOR BURNT OSTRICH EGGSHELL: AN EXPERIMENTAL STUDY b y ROBERT JOHN DIEHL B.A., Illinois Wesleyan University, 2013 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Master of Arts Anthropology Program 2017

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ii This thesis for the Master of Arts degree by Robert John Diehl has been approved by the Anthropology Program by Jamie H odgkins, Chair Christopher Beekman Charles Musiba Date: December 16 2017

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iii Diehl, Robert John (M.A. Anthropology Program ) Towards an Interpretive Framework for Burnt Ostrich Eggshell: An Experimental Study Thesis directed by Assistant Professor Jamie Hodgkins ABSTRACT Optimal foraging theory posits that hunter gatherers will seek to maximize the energetic and nutritional outputs of their diets. Recent research has examined how this has been achieved through cooking. For foods such as meat or tubers, the benefits are cle ar, but this is not always the case, especially when raw consumption is possible or the labor of cooking is intensive. Ostrich ( Struthio spp.) eggs represent s uch a food, with i ndications of consumption predating and postdating control of fire. If cooking ostrich eggs is indeed the optimal the archaeological record should reflect a shift in preparation contemporaneous with control of fire. In order to assess cooking patterns over time, a method for assessing thermally altered ostrich eggshell is necessary. This study reviews the lengthy history of ostrich egg exploitation in the archaeological and ethnographic records as well as previous taphonomic studies of thermally altered eggshell and presents the results of a series of actualistic studies of differe nt types of heating and the resultant changes in color and morphology The results demonstrate that anthropoge nic a nd non anthropogenic fires produce distinct patterns of changes as well as a potential diagnostic for cooking. T hese results have potential applications in understanding site taphonomy and interpretation. Furthermore, it has the potential to provide insight into the role of cooking in hunt er gatherer foraging strategies and optimal foraging theory. The form and content of this abstract are approved. I recommend its publication. Approved: Jamie Hodgkins

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iv TABLE OF CONTENTS CHAPTER I. 4 Ostrich Eggshell at Archaeological Sites ... ....4 Natural Occurrences of Ostrich Egg in the Archaeological Record Ostrich Egg Use in the Ethnographic Record The Rationale for Cooking Previo II. EXPERIMENTAL STUDY Materials & Methods Results Discussion Conclusion REFERENCES

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1 CHAPTER I INTRODUCTION Cooking is a fundamental, even necessary, human behavior ( Harris 1992; James 1989 ; Wrangham et al. 1999 ; Wrangham 2009), one of a gradually shrinking set we can claim exclusive domain over. It has deep ties to culture, identity, and social organization, but at a fundamental level, it facilitates our intake of energy and ultimately our survival. Much archaeological research has focused on the procurement and processing of foods but only relatively recently has the discipline begun to integrate information about the biochemi cal and nutritional benefits of cooking i n the study of prehistory ( Kelly 2013; Subias 2002; Wrangham et al. 1999 ) These studies posit that cooking became a vital adaptive strategy adopted by early humans in order to maximize energy intake (Wrangham 2009). In the cases of foods such as meat or tubers the process represents a clear, beneficial trade off (Wandsnider 1997) The analysis of these adaptive trade offs and the ir implementation in subsistence strategies is the key principle behind optimal foraging theory. I f however those foods may be consumed raw or when the labor of cooking has the potential to outweigh benefits that calculus becomes much more difficult Ostrich eggs are incorporated in archaeological sites that date back millions of years, and thus represent a food with a long history of human consumption The earliest indications of its consumption predate control of fire by more than a million years (Roche et al. 1999 ) suggesting raw consumption typified the early use of this resource but contemporary ethnographic records almost uniformly describe them as being cooked (Basedow 1925; Cott 1953; Wrangham 2009). Given that egg can be eaten raw with no ill effects (Wrangham 2009), why would there be an expectation that egg would consistently be cooked (and the

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2 shells therefore altered), especially if they were consumed raw befor e the regular control of fire? Cooking would seem to represent an unnecessary, expensive behavior, with the benefits accrued by cooking offset by the additional labor. Yet, recent nutritional studies have noted significant increases in protein absorption i n cooked egg compared to raw egg (Evenepoel et al. 1998; 1999) Furthermore, some scholars have raised that possibility that certain forms of cooking do not require significant added expense (Kelly 2013) These factors raise the possibility that the cook ing of eggs is indeed optimal, and a rchaeological indicators of cooking would be expected to appear consistently after control of fire a behavior dated to approximately one million years ago (Berna et al. 2013) In order to determine patterns of cooking over time it must be identifiable in archaeological material. The ethnographic record provides descriptions of how these eggs are prepared (Cott, 1953; Wannerbugh et al., 2000; Wrangham, 2009 ), but the understanding of how those actions are reflected in the archaeological record is poor. This research aim s to develop through experimentation and guided by middle range theory (Binford 1977 ) a framework for the interpretation of heat altered ostrich eggshell Per Binford, middle range theo ry is that which seeks to link measurable patterning in archaeological data to cultural practices. For example, Binford (1980) famously tied the spatial patterning of Nunamiut sites with broader mobility strategies. Currently such frameworks exist for the interpretation of heat altered bone ( Bennett 1999; Buikstra & Swegle 1989; Shipman et al 1984). These were developed through combinations of laboratory and actualistic experiments, and primarily take into account how coloration and morphology can be explained by cooking or other anthropogenic alteration or can be dismissed as the result of natural phenomena. This research will seek to establish a similar body of knowledge for ostrich eggshell.

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3 The results of this research have the potential to contribute to archaeological scholarship on several levels. Specifically it will facilitate the differentiation of anthropogenic cooking sites, anthropogenic eggshell disposal sites, and naturally occurring ostrich nests or carnivore dens modified by wil dfires Th is work will also help distinguish different egg cooking behaviors. This research has implications beyond archaeology. Being able to demonstrate consistent cooking of eggs would support the hypotheses of Wrangham and others and strengthen the use of human behavioral ecology in modelling subsistence. Conversely, if cooking were not consistent it would raise questions about other factors influencing diet, including culture, resource availability, and social dynamics. More generally, u nderstanding su bsistence strategies and resource extraction is an integral part of placing past peoples within the narrative of hominin evolutionary history Furthermore, cooking has become integral to our social and cultural dynamics. Greater comprehension of past cooki ng practices will connect us to our shared past both behaviorally and biologically. This paper will first review the long history of ostrich egg exploitation in the archaeological and ethnographic records. Next, it will discuss the energetic benefits of cooking and how those are integrated into an optimal foraging strategy. Previous studies of eggshell taphonomy and thermal alteration with be reviewed, with the experimental methodology informed by these subsequently described. Finally, the distinct patterns of c o lor and morphological changes that result from various types of heating will be described and the implications for archaeology specifically and for the broader understanding of our shared human past.

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4 Background Ostrich Eggshell at Archaeol ogical Sites Given the consistent evidence that ostrich eggs have been a component of Paleolithic subsistence strategies, it is surprising that more attention has not be paid to th eir interpretation. Roche et al. (1999) document some of the oldest evidence for egg exploitation with shell fragments in close association with Oldowan industry lithics at a Lake Turkana site estimated to be 2.34 million years old. Dominguez Rodrigo et al. (2009) m ention an abundance of ostrich eggshell ( OES ) Korongo site at Olduvai, but express uncertainty as to whether it was hominin carnivore assemblage or the remains of a nesting site Martin et al. 2009) The Lower Paleolithic site of Zhoukodian, inhabited by Homo erectus represents one of the earliest sites with charred eggshell (Boaz & Ciochon 2004). Middle Stone Age sites along the Western and South Cape of South Africa more definitively identify the presence of eggshell fragments as probable refuse from subsistence activities. At Ysterfontein along the Western Cape, more than two kilograms of ostrich eggshell fragments were recovered from lay ers dating between 33 and 70 k y a in association with stone tools, hearth features, and othe r probable food debris (Hal k ett et al. 2003) although the OES was located several meters away from the thermal features Texier et al. (2010, 2013) and Steele and Klein (2013) likewise describe the presence of b urnt shell fragments in the same stratigrap hic layer with hearths, ash dumps, and other features indicative of controlled fire use at Diepkloof rock shelter (also located on the Western Cape), dated to 60 k y a Robbins et al. (1996) likewise report burnt ostrich eggshell fragments, along with a broad range of other faunal material and lithics, in dense charcoal layers dating to between 11 and 30 k y a at the Late Stone Age site of

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5 cifically note the charring of shell fragments as indicative of cooking, although with no suggestion of a specific cooking technique. By sheer mass, however, the Apollo 11 Rockshelter represents one of the largest deposit s of ostrich egg, with 11 kg compri sing more than 15,000 engraved, unengraved, and burnt fragments across the Middle and Late Stone Age assemblage (Vogelsang 2010). The authors posit the majority of the fragments to be the result of artisanal activity or the remains of flasks, although Mu r ray Wallac e et al. (2015) note divergent patter ns of racemization that indicate fragments were either reworked or exposed to greater temperature variation suggesting multiple utilization strategies. Furthermore some of the burnt fragments f r o m Diepkloof are engraved and represent some of the oldest human art (Texier et al. 2013). The most common symbolic use for OES is in the form of beads. For example, Kandel and Conrad (2005) describe a collection of more than 2000 beads in a variety of colors and in a variety of stages of production from sites at Geelbek D unes in South Africa. Pei et al. (2012) report OES beads at an Upper Paleolithic site in China dated to approximately 35 k y a. Similarly, the Holocene site Chikhen Agui Rockshelter in Mongolia contained clusters of OES beads, as well as a collection of unmodified fragments (Derevianko et al. 2008). Other sites in Mongolia and Northern China show persistence of ostriches and human exploitation thereof as late as 8.9 k y a (Janz et al. 2009). Natural Occurrences of Ostrich Egg in the Archaeological Record Much as hominins value ostrich egg as a food source, carnivores will target eggs. Some such as jackals or Egyptian vultures will break and consume the eggs at or very near to the nest when hens are absent (Magige et al. 2009) Larger animals such as hyenas or lions may consume them in place, but are capable of transporting them (up to 7 km in some cases

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6 (Kandel 2004)) and will accumulate them with other prey at denning sites ( Henschel et al. 1979; Skinner & van Aarde 1991 ) Consequently, OES is present in many prehistoric carnivore accumulations (Scott & Klein 1981). For exa mple, Rector and Reed (2010) describe a carnivore den assemblage attr ibuted to the brown hyena ( Hyaena brunnea ) in one of the Pinnacle Point caves (PP30), located in Western Cape, South Africa, diagnostic carnivore damage to eggshell was used to establish that OES accumu lations from Geelbek Dunes as the result of hyena scavenging. The other major natural accumulator of eggshell is nesting sites themselves. O striches will share communal nests, with several hens laying in a single nest (Bertram 1992). Additionally, these nesting sites may be reused, resulting in large shell accumulations (Bertram 1992). Such sites have been posited to be natural explanations for OES assemblages lacking direct evidence of human interaction (i.e. subsistence, engraving) (Dominguez Rodrigo et al. 2009). Ostrich Egg Use in the Ethnographic Record Indeed, ostriches and their eggs continue to be an important component of life among h unter gatherers in the Kalahari, 2001 ; Lee 1984; Silberbauer 1981 ). Altho ugh the birds themselves are not commonly hunted (Lee 1984), the eggs are still prized as a food source, especially when seas onal game migrations make other food sources scarce (Hollmann 2001 ). Eggs are by and large described as being eaten cooked ; i n the absence of ceramic or metal cookware, they are generally prepared by placing wh ole eggs in hot ash (Cott 1953) or simply by having the contents poured into a coal lined depression in the ground (Wannerburgh et al ., 2000) Variati on in human processing of other ratite (large flightless birds including ostriches, emus, rheas, and

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7 cassowaries) eggs has been documented as well, both archaeologically and ethnographically. Medina et al. (2011) report significant accumulations of burned Rhea eggshell fragments at pre Hispanic sites in central Argentina, as well as more contemporary ethnographic rep orts of the cooking of eggs over hearths or hot coals Similarly, Wrangham (2009) reports populations in Tierra del Fuego burying eggs on the edge of campfires. Likewise some Australian indigenous populations have also been documented as cooking t heir rat ite eggs by burying them in hot sand or ash (Basedow 1925) Aside from a contemporary travelogue (Rasmussen 2014), Hollmann (2001) is the only source to describe the consumption of raw egg. T he shells themselves are also commonly utilized. After being e mptied of their contents, the empty shells are very durable, with a breaking strength of 55 kg (Sales 2006). This allows their use as water canteens that are the primary method of transporting water across the landscape of the Kalahari during the wet season (Silberbauer 1981). Egg is also still a favored symbolic medium. Necklaces and other adornments with shell beads are valued personal adornments and are often exchanged as gifts (Marshall 1976). Finally, ostrich eggs figure into the mythology and s upernatural beliefs of groups in the area. Hollmann (2001) describes how in San iconography ostrich eggs represent a type of good fortune associated with hunting and food procurement success. On a broader scale, t he exchange of goods to create and maintain social bonds in hunter gatherer societies is well documented. Wiessner (1982) describes a manifestation of this in the hxaro system of mutual reciprocity among the !Kung San of the Kalahari. This delayed exchange of gifts strengthens social ties and allow s for the minimization of risk through sharing of resources. On a regional scale, the social ties created by hxaro can be used to facilitate distribution of localized

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8 resources, organize marriages, and manage stress caused by large scale environmental chan ges (Mitchell 1996). These networks of exchange even persist beyond the death of an 1986). As described above, o strich products, pr imarily beads but also feather s and canteens, h ave been documented ethnog raphically as key items in exchange systems ( Lange 2006; Miller 1996; Wiessner 1982). When artifacts have limited geographic availability, their presence in exotic locations well beyond foraging ranges can be used as an indicat or of exchange. Establishing the presence or lack thereof of ostriches in a given region can be limited by the fossil and historical r ecords, and some regions can ultimately be deemed to have lacked ostrich populations (Miller 1996). In regions where the birds are common, however, exchange of such goods can be more difficult to establish. While ostrich eggshell that has been worked into beads or engraved can more easily be assumed to have exchange value, fragments that lack such markers ha ve been largely ignored. I sotopic analysis has previously been applied to eggshell as a dating method (Brooks et al. 1990; Murray Wallace et al. 2015) and as a component of paleoclimate reconstruction (Johnson et al. 1997 Lee Thorp and Ecker 2015). More recently isoto pic analysis has been applied to ratite eggs to track human exploitation and transportation (Giardina et al. 2014; Hodgkins et al. in press) across the landscape. Nevertheless, when a site presents tens of thousands of fragments as in the case of Apollo 11 Rockshelter (Vogelsang et al. 2010), determining which should be subjected to costly and time consuming isotopic analysis can be difficult in the absence of indicators of human activity. This study will show that coloration patterns on heated eggshell can help differentiate anthropogenically modified ostrich eggshell from naturally deposited eggshell modified by bushfires.

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9 The Rationale for Cooking Optimal foraging theory provides a better understanding of the adaptive role of cooking This analytical tool has been foundational in the quest to understand how human populations past and present, especially mobile hunter gatherers, construct their diets, and has been applied to populations over the world (Alvard 1993; Byers & Ugan 2005; Hawkes et al. 19 82, 1991; Hill et al. 1 987; Riley 2012; Winterhalder 1986; Zeder 2012). As previously discussed, t here is evidence that eggs have long been a valued resource with both burned and unburned ostrich eggshell (Robbins et al. 1996; Texier et al. 2010, 2013; Vogelsang et al. 2010) fragments preserved in the archaeological record and a diverse range of ethnographic descriptions regarding egg handling and preparation (Cott 1953; Lee 1984; Wannenburgh 2000; Wrangham 2009). When considered throug h the lens of optimal foraging theory, it becomes clear that though raw consumption is possible and occasionally documented (Hollmann 2001), optimality theory suggests that cooking of ostrich eggs and, depending on cooking method, heating of the shell is to be expected after regular control of fire was established at approximately 1 mya (Berna et al. 2012). In order to address why eggs would be cooked, we must first understand why it is that cooking is done at all. Wandsnider (1997) and Crowther (2013) pr ovide the most proximate rationale for the practice of cooking. First, the heat treatment of foods can result in the reduction of toxins or other harmful chemical components or the elimination of harmful pathogens or parasites. Second, certain techniques ( e.g. smoking) can increase the time until spoilage, allowing the food to be preserved beyond its natural usability. These reasons for cooking can be described as facilitating consumption of a given food.

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10 The final reason for cooking is that it acts as a f orm of pre digestion. The effect of this is twofold. The first is that foods are softened by the cooking process, with the most obvious effect being that it facilitates consumption by infants or the elderly (Crowther 2013). On a broader biological level, Wrangham (2009) notes that it reduces the energy expended by the body during digestion. The softer a food is, the less energy must be expended by the body to break down and absorb it. Thus, although the total amount of calories absorbed from the foods them selves may remain constant, the investment by the gut to obtain those calories is reduced, resulting in a greater energetic profit. Furthermore, thermal processing techniques (i.e. cooking) have been shown to increase this profit to a greater degree than n on thermal ones (e.g. pounding meat to tenderize it) (Carmody et al. 2011; Zink et al ., 2014 ). The second effect is that cooking fundamentally alters the chemical structures of foods, rendering them into forms more readily received by the body (Wandsnider 1997). The degree to which vitamins, macronutrients, and other substances can be absorbed in the digestive process is known as bioavailability. Cooking often promotes processes such as denaturing and hydrolysis which weaken or reduce in size the molecule s of the substance, allowing more of it to be absorbed during digestion (i.e. increasing the bioavailability) (Wandsnider, 1997), and giving cooked foods superior nutritional content. Seve ral studies (Carmody et al. 2011; Davies et al. 1987 ) have demonstrated that cooking beef denatures its proteins and greatly increases available and absorbed protein, up to a factor of four in some cases. Similarly, cooking of tubers has been show n to increase their digestibility (Wandsnider 1997). Cooking increa ses the energy output of a given food source by reducing the energy expenditure of digestion, increasing the bioavailable nutrients, or both.

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11 Cooking ostrich eggs does not immediately seem to be worthwhile, as the process does not have some of the more obv ious benefits of cooking such as safety, preservation, or texture improvement. The eggs are safe to consume uncooked, and if anything, cooking changes the texture to a more robust consistency. Likewise, cooking does not significantly extend the edibility p eriod of eggs, as the shells naturally provide a degree of protection and the freshness period of the unbroken egg is therefore a matter of weeks rather than days (Wrangham 2009). Nevertheless, there is a significant benefit. While the overwhelming majori ty of anthropologi cal and archaeological studies of the effects of thermal processing have been focused on meat and tubers (Zink et al. 2014) (dietary staples for much of the world), some work in the field of nutritional science has been done on egg. Even epoel et al. (1998, 1999) demonstrated that there is a significant increase (approximately 40%) in protein bioavailability between raw and cooked egg. Protein is the most prioritized macronutrient in the human diet and it has been shown that above the mini mum necessary dietary threshold, gatherers will seek to not only pursue protein, but preferentially seek out resources that maximize its acquisition even at the expense of some caloric output, and this phenomenon will not occur with other macronutrients such as carbohydrates (Hill et al. 1987). It follows then that if humans will seek to maximize resources in the foods that they pursue, they will also seek to max imize it in the foods they acquire. If the maximization of energetic and nutrient returns is always preferable, then cooking would be expected to be performed when there is a benefit. It might be argued that the additional benefits accrued by cooking are o utweighed by the expense incurred by cooking as raw ostrich egg already seems to represents an ideal food

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12 source (Wrangham 2009). The search cost is relatively low, as nesting sites are static compared to mobile animal herds and as such, the only inve stm ent is in locating that site. Furthermore, they incur no pre transport processing costs in the way that a large animal kill would. The only required processing is cracking a hole through which the contents are drunk; chewing would not even be necessary. Fu worth of calories for a single adult hunter gatherer (Lee 1984) as well as a broader range of necessary proteins in greater quantities than practically any other common food (Wrangham 2009). Thus cooking c an definitively increase the output of foods ( Carmody et al. 2011; Wandsnider 1997; Wra ngham 2009 ) Optimal foraging theory considers cooking to be a technolo gical processing technique (Lupo 2006 ). Bright et al. (2002) report that technology will be applied in order to reduce handling time of foods in order to maximize net gain, providing the example of increased milling stone production and a shift towards a more efficient design in order to reduce handling time of seeds and ultimately increase energy profit. If strategies that apply technology to decrease energy expenditure and increase the net energy or nutritional output of a given resource are considered optimizing, then those that apply technology in order to increase the energy output of a resource should be considered the same as those that reduce handling time when the additional output is greater than the additional input. Fire is a technology and therefore, all else being equal (i.e. when safety or preser vability are controlled for), cooking should be considered to be optimal when it produces a net gain in energy output. Hill et al. (1987) and De Vynck et al. models. The former notes that after a short preparat ory process, the cooking of meat lasts for

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13 several hours with minimal participation needed. This allows other productive activities to be conducted while cooking occurs (Kelly 2013). Furthermore, this cook ing is done during the night when the handling ti me cost does not as strongly impinge on other activities. cooking process, as well as a division of labor between foragers and cooks, and the idea that post c ooking extraction does not affect the foraging calculus. Rather, they prioritize the energy expenditure of firewood gathering and that of tending to the cooking process. Wrangham and Carmody (2010) argue that fire s are likely to be present in hunter gather er camps independent of cooking needs as predator deterrents, rendering the cooking specific wood gathering minimal. For some foods, as is the case with De Vynck et al. assumed for all items. Furthermore, while Kelly (2013) acknowledges that some cooking techniques such as stone boiling require enough constant attention to merit consideration in terms of expense, most do not. The egg cooking methods described in the ethno graphic literature fall into the less labor intensive category. Previous Studies of Eggshell Taphonomy Due to its relative fragility (especially for smaller birds), eggshell has not been the subject of a large body of taphonomic inquiry in the same way as other zooarchaeological materials such as bone. While Kandel and Conrad (2005) and Texier et al. (2010) cursorily describe experiments that indicated color variation in OES as a r e sult of heat ing, Janssen et al. (2011) were the first to investigate in some depth the taphonomic effects of heating avian eggshell, conducting a battery of laboratory experiments to establish the range of variability associated with different heating intensities and times. They exposed OES fragments to

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14 progressively increasing temperatures (200 800C) over a range of exposure times (5 60 minutes) in an industrial kiln. Fragments were then assessed in terms of mass and coloration. The authors observed a broad range of colors associated with the variation in temperature including orange, yellow, brown, blue, and gray, as well as pronounced decreases in mass at approximately 470 and 730C. They suggested that the majority of observed color change was a function of exposure temperature rather than exposure time, with most changes occurring within 5 minutes, and little occurring past 30 minutes. Their observations regarding morphology are limited; they note the occasional destruction of the inner and outer layers (not explicitly described, but likely referring to the mammillary layer and cuticle respectively) as well as some flattening and inversion of the curvature of fragments expose d to higher temperatures (600C and higher). Given that only two fragments were subjected to each time/temperature combination, it is difficult to extrapolate the described variation as representative. Texier et al. (2013) made a more systematic approach to burnt OES fragments in order to interpret engraved fragments from the Diepkloof rockshelter assemblage. Their previous pilot work (Texier et al. 2010) demonstrated a range of colors produced by thermal alteration, explicitly mentioning orange, red, bla ck, and gray. In an effort to understand more precisely the color changes in burnt OES, the authors heated fragments to nine temperatures between 100 and 480C for twenty minutes, recording the resultant changes in mass, thickness, and coloration based on the Munsell system. They describe a color progression from unburnt to yellow, red, brown, gray, and blue gray as temperature increases, as well as fragmentation of the inner and outer surfaces (once again, presumably the mammillary and palisade layers) at temperatures exceeding 500C. Furthermore, they deem mass and

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15 thickness to be poor parameters for analysis. Once again, however, their sample is small, with only three fragments heated to each temperature. Collins and Steele (2017) provided the most compr ehensive study to date of thermal alter ation of OES, seeking to fully develop a model for the effects of thermal alteration on shell color. They beg an by replicating Janssen et al. (2011) and Texier et al. experiments, observing very similar patterns of color change, though notably they were not able to produce deep red or black coloration. A marked increase in friability was noted above 400C. Crucially, the second phase of their study involved heating OES with a fire. Three fragments were ex posed directly to the fire, while ten were buried in sand at depths of 5 8 cm below the fire. The authors noted rapid alteration in terms of time for the fragments exposed directly to the fire, but with distinct color gradients suggestive of rapid dissipat ion of heat through the air. Collins and Steele elaborate on six color categories based on exposure temperature: unburnt, yellow, red, black, iridescent, and grey white. While Collins and anded in several ways. First, sample size can be increased Second, subsurface temperature recordings could be taken on a more continuous basis to provide information regarding rates of temperature change rather than at long intervals. Fu rthermore, temperature probes employed by Collins and Steele suffered failures and were unable to measure temperatures far in excess of 200C opening the possibility of more precise measurements Finally, in addition to the analysis of already fragmented OES, therma l alteration of whole eggs with liquid still inside could be tested. Focusing on form rather than appearance and heating via cooking specifically, Taivalkoski and Holt (2016) subjected chicken eggs to a variety of cooking methods in order

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16 to determine whe ther those left characteristic damages to the microstructure detectable by scanning electron microscopy (SEM). They prepared eggs through boiling at two different durations, baking in an electric oven at 177C, and baking on hot coals for 10, 15, and 20 mi nutes with starting temperatures recorded at 520C. The eggs were fragmented and, after cleaning, examined through SEM for damage to the mammillary layer. They observed no apparent change in microstructure for boiled or oven baked shell compared to raw she ll, but noted delamination in fire sample size was small; only two eggs were given each boiling treatment and oven baked, and only one was fire cooked for each time interval, meaning that the r ange of variation was limited. Furthermore, they only seem to consider two disparate ends of a temperature spectrum, contrasting the relatively low temperatures with the high ones of fire with no intermediate method or control. Changes in color were only n oted in passing, which seems to be a missed analytical opportunity given those disparate exposure temperatures. Miller et al. (2016) examined burnt shell fragments from the extinct megafaunal bird Genyornis newtoni from Australia. They tested partially bla ckened fragments with amino acid analysis, finding total amino acid decomposition in those blackened areas, with progressively higher concentrations moving away from the blackening. They observed color variation commensurate with the change in amino acid d ecomposition, and attributed this to anthropogenic heating, suggesting that wildfires would not produce significant differential effects within and between tightly clustered fragments as in the Australian record. Rather, they suggest cooking methods such a s pit roasting or cooking on coals that have low overall exposure temperatures but may expose the eggs to small, acute heat sources such as single embers or coals would result in intense but localized discoloration. In general terms however,

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17 they propose t hat the most effective cooking methods moderate heat exposure to prevent rupture of the eggs, resulting in little alteration of shell color or morphology.

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18 CHAPTER II EXPERIMENTAL STUDY Materials & Methods In this study, two distinct tests were run. The goal of the first test was to establish the effects of heating on shell fragments at and below the surface. The goal of the second test was to determine the effects of cooking on whole ostrich eggs. The first used ostrich egg fragments purchased fro m Floe cks Country Ostrich Farm ( https://www.floeckscountry.com/ ) in Tucumcari, NM. For the second, eleven whole eggs were purchased from Ostrichland USA in Solvang, CA ( https://www.ostrichlandusa.com/ ). In the second test, o ne whole egg was reserved for other research and two whole eggs showed signs of damage in shipping and were excluded from this experiment. Thus, eight whole eggs were used in the second experiment. Given that analysis was conducted on shell fragments, and each egg was capable of producing enough fragments for a sufficient sample for statistical testing this was deemed a sufficient number of eggs. Firewood was pine purchased from a local firewood sel ler. The sandy soil blend used upon which the fires were built and in which some eggs were buried was purchased from a hardware store. Two fires were constructed in permanent metal campground fire rings and the third was constructed in a freestanding burn barrel approximately 26 inches in diameter. No artificial acceleran ts were used to start the fires; instead a combination of dryer l int and small pine shavings was employed. Temperatures were measured with Omega TJ 36 CAIN 14G 24 temperature probes (rated to 1372C) and recorded with Omega RDXL4SD and Sper Scientific 800021 dataloggers. For the first test (heating of OES fragments), the fire rings were filled with sandy soil To simulate alteration of buried OES, handfuls of fragments were scattered at a pproximately

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19 three centimeters below the surface such that some fragments were oriented with the exterior facing upwards and some downwards. Furthermore, some were oriented with varying degrees of verticality. These measures were taken to reflect the varie ty of orientations that could result from post depositional turbation. A temperature probe was inserted through a hole in the fire ring and placed such that the measuring portion of the instrument was at three centimeters subsurface (Figure 1 top ). Fragme nts were then covered with soil. The other temperature probe was situated with the measuring portion of the device in approximately the center of the fire at the surface (Figure 1 bottom ) with the location adjusted periodically to maintain position in the hottest part of the fire. Temperature readings were logged autom a tically at 30 second intervals. This provided a sufficient number of temperature data points and given that broader temperature trends were the focus, more frequent sampling would have been redundant. To simulate disposal or exposure to a brushfire, handfuls of fragments were scattered directly into the fire once the larger logs had ignited. These fires were allowed to burn for approximately 100 minutes at which point logs and coals were remo ved and fragments were removed and excavated. T he seco nd test (heating of whole eggs) was split into multiple experiments In the first, sandy soil was put into the bottom of the burn barrel, with two eggs each laid on their sides such that the highest po ints were three and five centimeters below the surface (Figure 2). Temperature probes were place at five centimeters subsurface via a hole in the barrel and

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20 Figure 1: Fragments set at three centimeters subsurface with temperature probe (top) and test i n progress with probes at surface and three centimeters subsurface (bottom).

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21 angled from above to rest at three centimeters subsurface. The barrel was th en filled to the rim with sandy soil A third temperature probe was rested on the surface as in the fragment tests. The fire was then ignited and allowed to burn for approximately 100 minutes. The logs and coals were removed, and the buried eggs were turned such that the side that previously faced the surface now faced downwards (consistent with eth nographic descriptions of egg cooking ( Miller et al. 2016; Taivalkoski & Holt 2016; Wrangham 2009 ) ). Eggs were then reburied and a new fire was built which was allowed to burn for approximately 65 minutes. In the second experiment, the remaining hot co als from the first experiment were shifted to one half of the surface. Two eggs each were then placed on the hot coals and on the heated soil (Figure 2). One of the eggs on the coals cracked and disgorged its contents soon after it was placed. It was remov ed, and a hole was created in the other egg placed on the coals to relieve pressure and prevent further losses. The remaining eggs were rotated in place approximately every five minutes until the surface temperature cooled to under 100C (approximately 40 minutes) at which point they were removed and the buried eggs were excavated. In preparation for analysis, a hole was made in the whole eggs with a hammer and scre wdriver and the contents removed Shells were then fragmented with the side of a hammer, with a towel used as padding to diffuse the impact. Any remaining solidified contents were removed. Fragments from immediately aroun d the drain hole were discarded to avoid misinterpretation of the damage from fragmentation as thermally induced damage. All fra gments were cleaned with tap water to remove surface dirt and ash. Drying was accomplished with a combination of paper towels and air drying.

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22 Figure 2: Whole eggs for subsurface cooking tests, pre burial (top) and whole eggs for surface cooking tests (bottom).

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23 In total, 325 heated fragments were recovered (see Table 1 for a bre akdown by heating category). Thirty two unburnt specimens were also recorded as controls, bringing the total number of fragments to 347. Specimens were examined via tradit ional microscopy at 7 40x magnification and with a Dinolite digital microscope at 25 50x magnification. Fragments were assessed and classified in terms of color and morphology. Exterior color was assigned to one of seven ordinal categories (from lowest ass ociated exposure temperature t o highest, based on Texier et. a l (2013) and Collins and Steele (2017)): off white, pale yellow, orange, brown, black, blue grey, and white. The presence or absence of a color gradient was noted, and those with a gradient were assigned to the category of the highest exposure temperature color present. Exterior gloss was rated on a 0 3 scale, zero being matte, one being mildly glossy, two being very glossy, and three being iridescent. Morphology was assessed in terms of the pres ence, presence with damage or absence of the exterior and interior mineral layers of the shell: the mammillary or cone layer and the cuticle layer. Flattening was assessed on a 0 2 scale, with zero representing normal curvature, one representing flattenin g of the shell, and two representing inversion of the normal curvature. Data regarding the morphology and coloration of the membranes was deemed not to be reliable. The relat ive fragility of the membranes and their propensity to pull away when solid ified egg contents were removed made it difficult to obtain accurate results. The admission of the source farmer for the fragments that she often removed membranes before sh ipping further compromised data gathering. Results Results revealed that s hell morphology only changes at the highest exposure temperatures. Surface burned fragments showed consistent damage, with 47.1% displaying

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24

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25 damage to the cuticle or lacki ng it altogether (Figure 3, top ). Likewise, 60.9% showed alteration of the mammillary layer, and it had been completely destroyed in 32. 2% of specimens (Figure 3, bottom ). Furthermore, 40.2% of surface burned fragments were flattened, with a further 18.4% having inverted t heir natural curvature (Figure 4 ). In contrast, the only other category to show structural alteration was the fragments heated at three centimeters subsurface. Among those only 6.3% showed damaged to the cuticle, 12.5% showed damage to the mammillary layer, with 1 specimen (2.1% ) having the mammillary layer destroyed completely Addi tionally, only 6.3% showed any flattening, and none were inverted. All other fragments in the other categories showed no structural signs of thermal alteration. Color proved to be much more indicative of burning circumstances (Figure 5 ). Fragments burned on the surface showed a broad range of colors, but tended to concentrate towards the upper end of the spectru m, with 57.5% falling into the blue grey and w hite categories. The fragments burned at three centimeters showed similar breadth in their distribut ion, but are skewed towards the lower end of the spectrum with 56.3% of fragments cate gorized as orange or b rown, and 89.6% categorized as brown or bel ow. The fragments of the whole eggs showed much less variation. T he preparation method with the most inte nse color change turned out to be coal cooking. When cooked that way 5 3.8% remained apparently unaltered 30.8% reached orange, and only 11.5% were classified as brown. Among those cooked at three centimeters subsurface, no fragments exceeded orange. Likew ise, cooking on hot soil and at five centimeters subsurface produced only off white and pale yellow fragments. Unlike other variables, g lossiness showed no obvious patterning related to heating type or color category so further testing was necessary. A Fi

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26 Figure 3: Cuticle (top) and mammillary (bottom) layer damage patterns by heating type.

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27 Figure 4: Flattening patterns by heating type. Figure 5: Color patterns by heating type for fragment tests (left) and whole egg tests (right).

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28 Test based on a 10,000 sample Monte Carlo (selected because of low expected values) was perform ed with subsequent examination of the standardized residuals which showed associations between gloss and both heating type and color category (p=. 000). For heating type (Table 2), the strongest relationships exist between iridescence and the higher exposure temperature heating types. For color (Table 3), the strong association was seen between brown, bla ck, blue gray and iridescence. The u nburnt con trol shells tended towards some degree of gloss, but not a matte or iridescent appearance. The eggs cooked whole on hot soil show an unusually strong trend towards being both matte and pale yellow. Giv en that this is not reflected by the unburnt shells or shell heated by hot coals (with the closest exposure temperature), there is a strong possibility this is related more to the natural color and texture variation the eggs used in the experiment than the heating circumstances. Recorded temperatures showed distinctive ranges associated with distance from the heat source (Figure s 6 9 ). Surface temperatures (after the first five minutes) fluctuated greatly, ranging from 93.2C at the end of the surface cooking test to 916.2C during the middle fragment testing in windy conditions, with an average temperature of 587C. In comparison, subsurface temperatures were slow to rise. At five centimeters subsurface, more than 100 minutes was required to raise the temperature from its startin g point of 19.7 to its maximu m 81.2C. Temperatures at three centimeters were more responsive, ranging from 76.2 to 568.9C, but retained an average measurement much lower th an the surface tests at 299.3

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29 Heating Type Exterior Glossiness Crosstabulation Standardized Residual Exterior Glossiness Matte Mildly Glossy Glossy Iridescent Heating Type Unburnt .5 3.0 3.6 2.3 Fragments, 3 cm 2.4 .6 .3 2.6 Fragments, Surface 1.5 2.7 2.1 5.3 Whole, Hot Coals 2.0 .3 1.4 .6 Whole, Hot Soil 8.1 1.1 4.2 2.7 Whole, 3 cm 2.8 2.2 1.7 2.8 Whole, 5 cm 3.1 2.8 .7 1.8 Color Exterior Glossiness Crosstabulation Standardized Residual Exterior Glossiness Matte Mildly Glossy Glossy Iridescent Color Unburnt 3.6 2.9 2.4 4.1 Pale Yellow 6.2 1.3 .8 3.1 Orange 2.5 .7 .5 .7 Brown 1.9 2.5 .6 4.2 Black 1.2 1.1 .5 3.5 Blue Gray .7 .7 3.1 6.6 White 6.8 1.7 2.7 .3 type and exterior glossiness. and exterior glossiness.

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30 0 100 200 300 400 500 600 700 800 0 5 10 15 20 25 30 35 40 Temperature in C Time in Minutes Fire 1 Temperature Surface 0 100 200 300 400 500 600 700 800 900 1000 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 Temperature in C Time in Minutes Fire 2 Temperatures Surface 3cm Subsurface Figure 6: Fire 1 temperature over time. Figure 7: Fire 2 temperatures over time.

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31 0 200 400 600 800 1000 0 5 10 15 20 25 30 35 40 45 50 55 60 Temperature in C Time in Minutes Fire 3 (restart) Temperatures Surface 3cm Subsurface 0 200 400 600 800 1000 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 Temperature in C Time in Minutes Fire 3 Temperatures Surface 3cm Subsurface 5cm Subsurface Figure 8: Fire 3 temperatures over time. Figure 9: Fire 3 temperatures (post restart) over time.

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32 Discussion The temperature profiles for each of the hypothetical circumstances were shown to be radically different. Subsurface temperature was much slower to rise, taking more than fifteen minutes to exceed 300C from ambient air temperatures of approximately 20C at the three centimeter depth. Even when the third fire was restart ed ( after turning the buried eggs ) with the soil already having been heated it took approximately seven minutes to return to 300C. The temperature at five centimeters subsurface failed to reach even 100C after 100 minutes of heating. Brushfires, though they may produce temperatures in excess of 1200C (Dennison et al. 2006), move very r apidly. For example, Shea et al. (1996) documented brushfires in savannah landscapes in South Africa an d Zambia moving at between 0.2 and fire is extremely unlikely to burn in a single location for a long enough period of time to result in significant alteration of buried OES. Any variation in OES based on the capacity of various soil types to hold and transmit heat is negligible in comparison to that created by depth/distance from the heat source. The effects of a brushfire on surface fragments is more difficult to interpret. A fire with higher temperatures or a longer residence time would likely result in the destruction of the eggs If the fire were cooler or moved at a higher speed, ration would be the result of residual fires left behind the front, the temperatures of which could be up to 600C lower (D ennison et al. 2006). This suggest s that while many OES fragments would still experience delamination, exposure to brushfires may no t guarantee structure damage A taphonomic interpretation.

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33 Buried OES does show the potential to be altered by anthropogenic fire. This may or may not be intentional. A s Collins and Steele (2017) suggest, it may be a deliberate strategy to effect a particular color in shell to be used in bead making. Alternatively, later fires built at sites of recurring occupation may alter buried shell that was deposited in an unburned s tate. This process may even act on natural deposits, perhaps a nesting site or carnivo r e accumu lation. Anderson et al. (2005) related the case of a New Zealand rock shelter wherein burnt moa shell was associated with hearths also found at the site and inte rpreted as being the result of cooking by Maori travelers. Subsequent carbon dating revealed instead that there was a several hundred year gap between the shell and the charcoal in the hearths, with a subsequent hypothesis surmising charring shell from a d efunct nesting site by later human inhabitants suggesting that while OES can be an important line of evidence, the presence of other archaeological material is necessary to verify human habitation Nevertheless, the presence or absence of other archaeolog ical material in the same context may not be definitive determinant of human interaction. Johnson et al. (1997) reported that ostrich eggshell fragments may be more susceptible to post depositional movement than larger faunal elements. When the OES from Eq uus Cave was radiocarbon dated, most of it was found to be out of its proper stratigraphic context, with both upward and downward mixing occurring. Other faunal material was not shown to be disturbed in a similar way, suggest that OES is uniquely vulnerabl e to certain taphonomic forces (posited by the authors to be small mammal turbation.) Cooking was shown to be unlikely to produce significant alteration to OES. This is due to the delicate balance in exposure temperature that must be achieved between heat that is sufficient to cook the egg in a timely fashion but no t so intense as to rupture the egg. One

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34 of the eggs buried at three centimeters did crack and vent some contents to the surface, but ceased leaking quickly after. Additionally, one egg placed dir ectly on the coals ruptured quickly. A hole was made in the egg on the coals, but this inhibited the degree to which it could be rotated. Lack of experimenter savvy in the nuances of fire cooking eggs could be at least in part responsibl e for these failure s, but cooking on coals and burial at three centimeters seem to be those that strike the best balanc e between risk and efficiency. Given that little alteration was documented with t his amount of error, it is possible that more skilled cooks could expose the egg to higher temperatures and produce deeper shell colors without structural failure. It is however notable that even though these cooked eggs showed color change, there was markedly less iridescence than in fragments heated at the same depth. This ma y simply be the result of variation in exposure temperature, but other factors such as the insulating effects of egg contents or a continuous shell may be in play; in either case, further investigation is required. The results of the fragment component of this study are consistent with Collins and Steele (2017), with a similar range of colors observed. Some discrepancies are to be noted, visual quality with blue or gray exteriors. This study finds color and iridescence to be less directly linked it was also seen to be associated in brown and black fragments (Figure 10 ). In further contrast, experiments failed to produce them. They were however the least represented category, accounting for only 2.9% of al l fragments. Given the continuum of color from dark brown to black or black to gray sections it is suggested that blackening represents a specific exposure

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35 Figure 10: Iridescent fragment categorized as brown.

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36 temperature between those for dark brown and gray. This temperature would seem to be correlated with exposure temperatures greater than those at 3cm subsurface and at the surface. The lack of fragments at that depth could explain their absence in both studies. Propos ed alternate factors such as the available oxygen or other organic compounds cannot, however, be discounted. Conversely, this study did not observe a lightening of coloration between the orange and blue ather further darkening from orange to brown and black before arriving at gray was seen. This would seem to confirm their supposition that some as yet unknown factor that acts betwe en approximately 300 and 500C is responsible for the lack of deep red fra gments in kiln experiments. The f indings of this study call into question Miller et al. n that a sharp thermal gradient on a single shell fragment or among closely related fragments is in and of itself diagnostic of cookin g. Though the exact range of color variation in thermally altered Genyornis newtoni egg is unknown and amino acid analysis was beyond the parameters of this study, sharp color gradients were seen in both buried and surface burned fragments in addition to t hose from c oal cooked eggs (Figure 11 ). This, along with the temperature data, suggests that though wildfires are unlikely to produce such patterns of alteration, alteration by anthropogenic fire would not necessarily have to be intentional to produce this patterning. If, however, such sharp gradients are contained solely wi thin a single fragment (Figure 12 ) that may indicate a very focused heat source affecting a very localized part of a whole egg, a scenario which only makes sense in the context of cookin g. Wildfires would be incapable of producing such a localized effect. With heat dissipating more gradually in soil than in air, u nintentional heating of buried fragments would produce

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37 Figure 11: Fragments showing similar color gradients. Heated by hot c oals (top), burned fragmented on the surface (middle), and burned fragmented at three centimeters subsurface (bottom).

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38 Figure 12: Fragments of hot coal heated eggs displaying "contained gradients", with color gradients encompassed on single pieces.

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39 minimal, if any gradients on horizontally oriented fragments and unidirect ional gradients (like those in F igure 11) on vertically oriented fragments Therefore a bidirectional Unfortunately, this acute heat exposure is exactly the source of structural weakening, meaning that post cooking, shells would be likely to fractu re at the location of such gradients, especially as their extremity increases), rendering them indistinguishable from other fr agments with gradients (Figure 11 ). Conclusion identify the way in which any single OES fragment was heated, it did identify several overall trends in the temperature profiles of different circumstances in which OES could e xperience thermal alteration. Fragments heated above ground were generally blackened, gray, or white with significant damage or even complete destruction of the cuticle and mammillary layers. Fragments burned at three centimeters subsurface showed a broad range of colors from unburnt to blue gray, but little in the way of morphological damage. Finally, eggs heated whole show minimal shell alteration, but does present the possibility of a characteristic contained gradient that will need to be investigated fu rther. A number of specific questions regarding the variation in heated OES still remain. Color gradients were observed on multiple preparation categories, reflecting the fact that thermal gradients were common both above and below the surface. The relati ve dissipation of heat through air as compared to dense media such as soil or sand could inform future be employed to identify

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40 heating circumstances. Another future avenue of inquiry would b e to examine in depth not merely the immediate effects of thermal alteration but its long term impact on preservation. Fragments exposed to the highest temperatures suffer apparent structural damage that would seem to decrease their survivability, but heat ing may weak en OES in ways that are not immediately apparent resulting in differential preservation. Further investigation into forces that would alter appearance such as soil staining and abrasion that may alter surface gloss should be investigated. In particular, manganese oxides, which has be en known to create blackening in buried bone similar to burning (Shahack Gross et al., 1997), could operate on OES in a similar fashion. The precise factors that resulted in the variation in this and other studi colored fragments merit further analysis and likely have associations with heating conditions. Once these other factors are better understood, w e can then begin to apply the knowledg e of thermally altered OES variability to archaeological OES. For example, Texier et al. (2010, 2013) describe the altered OES fragments from Dipekloof as being colored dark red, orange, and brown. Combined with the fact that they were burned post fragment ation (established through refitting) (Texier et al. 2010), this color pattern strongly suggests that these fragments were altered by a later anthropogenic fire while buried. Unfortunately, this cannot be as immediately applied to other sites as their OES is described in little detail in the literature, but there is potential for the examination of existing collections. Apollo 11 rockshelter would be ideal for this; the sheer amount of OES and its presence throughout the Middle and Late Stone Ages would al low for study of diachronic patterns of egg exploitation. Furthermore, this method holds the potential to serve as a proxy for both human activity and control of fire Zhoukodian provides an ideal test case. Initial research suggested

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41 that the site was occ upied by a behaviorally sophisticated Homo erectus possessing control of fire (Boaz et al., 2000 ; Weiner et al., 1998 ). That proposition has been challenged, with Weiner et al. (1998) failing to detect other archaeological byproducts of fire such as ash or in situ hearth features. Boaz et al. (2000), among others, have posited that the faunal and hominin remains contained i n the caves were largely the result of hyena predation, with only minimal human contribution. Identifying if the OES from the site was thermally altered and the source of that alteration could provide strong evidence for control of fire and suggest more si gnificant human occupation. Similarly, examination of the OES from Ysterfontein could strengthen its association with thermal features. The understanding of egg exploitation patterns also has more general applications As ostrich eggs are laid at a speci fic time of year, identifying cooked OES could provide a window into seasonal occupation patterns. On a broader scale, ostrich eggs can be consumed either raw or cooked. Locating cooking in the record could illuminate temporal and spatial patterns in cooki ng that could relate to cultural divisions in behavior, climate, and nutritional stress. Alternatively, canteens have been proposed to be exchange goods that passed through early social networks (Curtis Marean, personal communication). Therefore, burnt OES that was not cooked but shows indications of being anthropogenically deposited can be sourced through isotopic analysis to lend insight into these trade patterns. Ostrich eggshell is a rich informational resource that is only now coming into its own and w ill continue to aid archaeologists as research into it continues.

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