A BIOARCHAEOLOGICAL INVESTIGATION OF STATURE, LOWER
LIMB PROPORTIONALITY, AND NUTRITIONAL STATUS
IN PREHISTORIC CENTRAL CALIFORNIA
______
A Thesis
Presented
to the Faculty of
California State University, Chico
______
In Partial Fulfillment
of the Requirements for the Degree
Master of Arts
in
Anthropology
______
by
Janet E. Finlayson
Spring 2014 A BIOARCHAEOLOGICAL INVESTIGATION OF STATURE, LOWER
LIMB PROPORTIONALITY, AND NUTRITIONAL STATUS
IN PREHISTORIC CENTRAL CALIFORNIA
A Thesis
by
Janet E. Finlayson
Spring 2014
APPROVED BY THE DEAN OF GRADUATE STUDIES AND VICE PROVOST FOR RESEARCH:
______Eun K. Park, Ph.D.
APPROVED BY THE GRADUATE ADVISORY COMMITTEE:
______Guy Q. King, Ph.D. Eric J. Bartelink, Ph.D., Chair Graduate Coordinator
______Frank E. Bayham, Ph.D. ACKNOWLEDGMENTS
First and foremost, my committee deserves acknowledgement. My chair, Dr.
Eric J. Bartelink, invests a tremendous amount of time and effort into every one of his students, and has been a wonderful advisor to me. His tireless effort and generosity to his students is truly astounding and I could not have asked for a more dedicated mentor. My second committee member, Dr. Frank E. Bayham, was always willing to sit down with me and share his infinite wisdom. Dr. Bayham always had a smile, a bit of advice, and good words to keep me motivated.
Additionally, Dr. Colleen Milligan and Dr. P. Willey deserve recognition. Dr.
Milligan always lent me an open ear or two when I needed it the most, be it for personal or academic reasons. Dr. P. Willey spread his infectious appreciation of data to me from the start of my career, as well as his adventurous spirit for California’s beautiful outdoors.
It was an honor to work with these individuals, as well as the entirety of the CSU, Chico
Anthropology Department during my time there.
Although I moved about as far away as I possibly could within the country from my family and circumstances rarely permitted me to visit my home state, my family has always sent their support and bottles of Michigan maple syrup. Finally, Corey has been a constant source of unconditional moral support throughout my academic journey.
His patience and love for all things in the world makes me a truly lucky human.
iii TABLE OF CONTENTS
PAGE
Acknowledgments ...... iii
List of Tables...... vi
List of Figures...... vii
Abstract...... x
CHAPTER
I. Introduction...... 1
Research Hypotheses...... 3 Organization of the Thesis...... 7
II. Central California Environment and Resource Intensification ...... 9
Central California Environment ...... 9 Central California Chronology...... 12 Resource Intensification in Central California...... 17 Resource Intensification and Skeletal Indicators of Health ...... 20 Summary...... 24
III. Stature and Proportionality...... 26
Stature...... 26 Body and Lower Limb Proportionality ...... 32 Summary...... 34
IV. Cranial Porosity...... 35
Cribra Orbitalia...... 35 Porotic Hyperostosis...... 36 Etiology of Cribra Orbitalia and Porotic Hyperostosis ...... 37 Relationship of Cribra Orbitalia and Porotic Hyperostosis...... 41
iv CHAPTER PAGE
Cranial Porosity in Archaeological Populations...... 43 Summary...... 45
V. Materials and Methods ...... 46
Archaeological Sites...... 46 Data Collection Methods...... 54 Stature Estimation and Body Proportionality in Prehistoric California Populations ...... 57 Statistical Methods ...... 58 Summary...... 60
VI. Results...... 61
Sample Demography ...... 61 Temporal Trends ...... 63 Regional Trends...... 81 Sexual Dimorphism in Stature...... 93 Comparison of Stature in Individuals with Cranial Porosity...... 97 Summary...... 100
VII. Discussion and Conclusions...... 107
Stature...... 107 Lower Limb Proportionality...... 113 Cranial Porosity...... 115 Study Limitations ...... 120 Future Research...... 121 Conclusions ...... 122
References Cited...... 125
Appendices
A. Skeletal Measurements...... 141 B. Statistical Results...... 144
v LIST OF TABLES
TABLE PAGE
1. Early, Middle, and Late Period Skeletal Samples ...... 48
2. Sites by Region in Central California...... 49
3. Scoring for Presence and Severity of Cranial Pathological Conditions Cribra Orbitalia and Porotic Hyperostosis...... 56
4. Scoring for Activity of Cribra Orbitalia and Porotic Hyperostosis...... 56
5. Stature Equations for Males and Females from Auerbach and Ruff (2010) ...... 57
6. Sample Demographics...... 62
vi LIST OF FIGURES
FIGURE PAGE
1. Map of Archaeological Sites ...... 47
2. Temporal Trends in Mean Femoral Bicondylar Length by Region and Sex...... 65
3. Temporal Trends in Tibia Length by Region and Sex ...... 67
4. Temporal Trends in Mean Estimated Stature by Region and Sex...... 68
5. Temporal Trends in Mean Total Leg Length by Region and Sex...... 69
6. Temporal Patterns in Mean Tibiofemoral Index Values by Region and Sex...... 70
7. Temporal Distribution of Cribra Orbitalia Considering All Regions Combined ...... 71
8. Temporal Distribution of Cribra Orbitalia in the Bayshore Region...... 72
9. Temporal Distribution of Cribra Orbitalia in the Interior Bay Region ...... 74
10. Temporal Distribution of Cribra Orbitalia in the Central Valley Region...... 75
11. Temporal Distribution of Porotic Hyperostosis Considering All Regions Combined ...... 76
12. Temporal Distribution of Porotic Hyperostosis in the Bayshore Region ...... 78
13. Temporal Distribution of Porotic Hyperostosis in the Interior Bay Region ...... 79
14. Temporal Distribution of Porotic Hyperostosis in the Central Valley Region...... 80
vii FIGURE PAGE
15. Regional Distribution of Mean Femoral Bicondylar Length ...... 82
16. Regional Distribution of Mean Tibial Lengths ...... 83
17. Regional Variation in Mean Estimated Stature...... 84
18. Regional Variation in Mean Total Leg Length ...... 85
19. Regional Variation in Mean Tibiofemoral Index Values...... 86
20. Regional Variation of Cribra Orbitalia During the Early Period ...... 87
21. Regional Variation of Cribra Orbitalia During the Middle Period ...... 88
22. Regional Variation of Cribra Orbitalia in the Late Period ...... 89
23. Regional Variation of Porotic Hyperostosis in the Early Period...... 90
24. Regional Variation of Porotic Hyperostosis in the Middle Period...... 91
25. Regional Variation of Porotic Hyperostosis in the Late Period ...... 92
26. Sexual Dimorphism in Femoral Bicondylar Length ...... 94
27. Sexual Dimorphism in Tibia Length ...... 94
28. Sexual Dimorphism in Estimated Stature...... 95
29. Comparison of Mean Stature between Males with the Presence and Absence of Cribra Orbitalia...... 98
30. Comparison of Mean Stature between Males with Higher Severity versus Absence/Low Severity of Cribra Orbitalia ...... 99
31. Comparison of Mean Stature between Females with the Presence or Absence of Cribra Orbitalia...... 100
32. Comparison of Mean Stature between Females with Higher Severity versus Absence/Low Severity of Cribra Orbitalia ...... 101
viii FIGURE PAGE
33. Comparison of Mean Stature between Males with Presence or Absence of Porotic Hyperostosis ...... 102
34. Comparison of Mean Stature between Males with Higher Severity versus Absence/Low Severity of Porotic Hyperostosis ...... 103
35. Comparison of Mean Stature Between Females with Presence or Absence of Porotic Hyperostosis...... 104
36. Comparison of Mean Stature Between Females with Higher Severity versus Absence/ Low Severity of Porotic Hyperostosis ...... 106
ix ABSTRACT
A BIOARCHAEOLOGICAL INVESTIGATION OF STATURE, LOWER
LIMB PROPORTIONALITY, AND NUTRITIONAL STATUS
IN PREHISTORIC CENTRAL CALIFORNIA
by
Janet E. Finlayson
Master of Arts in Anthropology
California State University, Chico
Spring 2014
Late Holocene resource intensification models indicate a temporal shift from exploitation of large, low-cost food resources to smaller, high-cost resources in central
California. Additionally, archaeological evidence suggests intensified use of high-cost vegetal resources through time, such as acorns and small seeds. Late Holocene central
California populations also became more sedentary and population density increased over time. These changes have been documented to negatively affect health.
A sample of 669 individuals from 21 archaeological sites dating to the Early
(>3450-2450 BP), Middle (2450-940 BP), and Late (940-230 BP) Period occupations were evaluated for trends in stature, lower limb proportionality, and cranial porosity.
These stress indicators were also compared between sites located near the San Francisco
Bay, Central Valley, and in an interior Bay Area region. Results indicate stature declined
x from the Early to Middle Period, consistent with predictions from resource intensification models. A rebound in stature is evident from the Middle to Late Period, which was an unexpected result. Female stature was affected more so than male stature, which may have inadvertently resulted from sexual division of labor in food acquisition practices or differential parental investment. For most analyses, the prevalence of porotic hyperostosis decreased over time while there was no significant change in the prevalence of cribra orbitalia. These trends were opposite the expected pattern. Furthermore, geography appeared to be an important factor in determining body size and conditions for disease or parasitic infections, and was likely influential due to the availability and diversity of resources in the immediate environment.
xi
CHAPTER I
INTRODUCTION
Records of early European explorations and settlements indicated California was a land of abundance. Around the time of contact, California had a very high native population density (Cook 1976). While these European explorers observed a landscape rich with vegetation and large game, archaeological and zooarchaeological evidence from the Late Holocene shows that these resources may not have always been as readily available, indicating resource depression in the prehistoric record. Archaeological evidence supporting resource depression in the Late Holocene follows a pattern of exploitation of large, low-cost mammals to smaller, high-cost animal resources
(Broughton 1994a, 1994b). Furthermore, the use of other high-cost resources such as acorns is believed to have intensified dating to the Late Holocene, as evidenced by the increased prevalence of mortars and pestles in the archaeological record during the
Middle Period (Basgall 1987). The explorers’ impression of a resource-rich California was likely due to a rebound in large game abundances resulting from decimated Native
American populations (Broughton 1999). This large decline in native population is attributed to numerous consequences of European contact, such as the introduction of foreign diseases (Cook 1976).
Skeletal remains provide a unique opportunity for researchers to observe the biology of past populations and understand how they interacted with their environment.
1 2
Stature is commonly used as an indicator of health within a population (Broughton et al.
2010:390-392; Goodman and Martin 2002; Steckel 1995). Variation in stature may exist because bone, as a living tissue, adapts during growth and development to stresses such as malnutrition or disease. These adaptations may be observed skeletally as altered growth and development or evidence of growth stress.
In this study, a diachronic evaluation of stature change will be viewed through the lens of resource intensification and paleonutrition in prehistoric central California through the Early (>3450-2450 BP), Middle (2450-940 BP), and Late (940-230 BP)
Periods. This provides a temporal framework to evaluate the effects of dietary change.
Documented evidence of resource intensification leading to increased vegetal resource consumption in central California, especially balanophagy (acorn eating), presents a cultural context that may explain temporal changes in stature.
The main research hypothesis for this study is that as subsistence practices changed to a lower quality diet in the Late Holocene for central California, stature decreased. Additionally, it is expected that long bone proportionality and joint size changed as a response to nutritional stress. Other studies have shown that the growth of the distal limb bones, especially the tibia, is highly sensitive to a variety of environmental conditions and is typically the most responsive bone when looking at proportional change in long bones (Jantz and Jantz 1999). In the context of central California and the change to a sub-optimal diet, it is predicted that the tibia will decrease in length relative to femoral length over time.
With the documented change towards increased use of vegetal foods, it is also expected that the prevalence of porotic hyperostosis and cribra orbitalia (indicators of
3 possible anemic response) increased over time in response to nutritional stress. It is also expected that individuals that show signs of nutritional stress manifested as cranial porosity will be of shorter stature than individuals without porosity. Furthermore, this thesis will explore regional variation in stature, proportionality, and cranial porosity.
Skeletal samples are divided into three geographic regions for comparison: Bayshore,
Interior Bay, and Valley. This chapter outlines how the study’s main research questions will be tested using a series of smaller-scale hypotheses, as well as the organization of the remainder of the thesis.
Research Hypotheses
The main research question in this study is if changing subsistence practices during the Late Holocene in central California is associated with a temporal decline in skeletal health, as evidenced by a decline in stature, changes in lower limb proportionality, and an increased prevalence of cranial porosity. The second research question is to explore how geographic location and the available resources may affect health in central California, such as trends in porotic hyperostosis, cribra orbitalia, stature, and lower limb proportionality. The third research question is to examine the effects of diet change during the Late Holocene on sexual dimorphism. These questions are evaluated by testing eight hypotheses using several independent proxies and measurements for skeletal health, such as stature, lower limb proportionality, cribra orbitalia, and porotic hyperostosis. These hypotheses are outlined in the following sections.
4
Stature
Stature Hypothesis 1: Temporal Stature Decline
The first hypothesis in this study predicts that in response to dietary change in the
Late Holocene, average stature will decline over time in central California concomitant with resource intensification. It is predicted that this will be evident by a temporal decline in average femoral bicondylar length, tibia length, and estimated stature.
Stature Hypothesis 2: Regional Variation
This hypothesis predicts that there will be regional variation in stature between skeletal populations located near the San Francisco Bay estuary, the Central Valley, and the Interior Bay region. Specifically, it is predicted that Bayshore populations will be taller in comparison to the Interior Bay and Valley populations. Sites located near the
Bayshore would have had sufficient access to dietary protein, which would have been an important macronutrient for normal growth and development, since this region is expected to have a greater diversity of protein resources, such as fish, marine mammals, and terrestrial animals.
Stature Hypothesis 3: Sexual Dimorphism
The third stature hypothesis predicts that stature will be sexually dimorphic for central California populations. A temporal examination of sexual dimorphism may identify periods where stature differences between males and females are either maximized or minimized. An increase in sexual dimorphism in height may have resulted from a sexual division in labor, and thus, differential access to food resources; this may have unequally subjected the sexes to nutritional stress (Grauer and Stuart-Macadam
1998). For instance, since females are identified as the primary gatherers and processors
5 of plant food resources such as acorns (Jackson 1991), they may have subsisted more on plant-based foods. Males may have participated in hunting or fishing parties that were outside of home bases, and therefore may have promoted diets higher in protein. This expected difference in diet between males and females may have affected stature greater in one sex than the other.
Lower Limb Proportionality
Proportionality Hypothesis 1: Tibial Sensitivity and Temporal Decline in
Total Leg Length
The first proportionality hypothesis expects that total leg length will decline over time, and that changes in tibial length will be the largest contributor to this decline. This is because stature is expected to decrease, and lower limb length has been found to disproportionately contribute to changes in stature (Tanner et al. 1982). The length of the tibia has previously been identified as very sensitive to environmental and nutritional stress. Therefore, it is predicted that changes in tibial length will be the largest contributor in stature decline.
Proportionality Hypothesis 2: Regional Variation
The last proportionality hypothesis expects that regions that experienced the greatest change in stature also would experience larger temporal changes in body proportionality such as a decline in tibiofemoral index values and shorter total leg length.
Of the three regions, the Valley population in particular was expected to show these trends since their protein resources may have been more depressed or limited than in
Bayshore or Interior Bay populations.
6
Cranial Porosity
Cranial Porosity Hypothesis 1: Temporal Increase in Prevalence
The first cranial porosity hypothesis predicts that the prevalence of both cribra orbitalia and porotic hyperostosis will increase over time. Furthermore, the severity of these pathological conditions is expected to increase over time. While this hypothesis reflects trends observed in other studies focusing on skeletal health during major subsistence transitions, there are a few reasons why this trend is expected during central
California’s intensification of an acorn subsistence economy.
Acorns contain toxic tannins that are leached out before consumption, but this process may leave some traces of tannins. When consumed, tannic acids interfere with the absorption of vitamins and minerals such as vitamin B12 (Chung et al. 1998). Tannins also form insoluble complexes with iron to inhibit its absorption (Chung et al. 1998).
Deficiency in nutrients, such as vitamin B12, has been attributed as causes for porotic hyperostosis and cribra orbitalia (Walker et al. 2009).
Furthermore, the aggregation of people and increased sedentism promotes transmission of pathogens, poor sanitation practices, and parasitic infections that affect the retention and absorption of nutrients through diarrheal disease or blood loss (Holland and O’Brien 1997; Kent 1986). These conditions have also been identified as potential causes for cribra orbitalia and porotic hyperostosis.
Cranial Porosity Hypothesis 2: Regional Trends
It is hypothesized that regional variation exists in trends of cranial porosity prevalence. Specifically, Bayshore populations are expected to have more instances of cranial porosity than both the Interior Bay and Valley populations. This is because sites
7 located near the Bayshore would have had greater access to marine resources, which may introduce helminth infections, or other pathogens that prevent absorption of nutrients
(Holland and O’Brien 1997; Walker 1986).
Cranial Porosity Hypothesis 3: Stature Variation and Presence of Porosity
The third cranial porosity hypothesis and the last prediction of the thesis expects that individuals with cribra orbitalia or porotic hyperostosis will have shorter stature than those without evidence of cranial porosity, and that those with moderate-to-severe cranial porosity would be shorter than those with lower severity or absence of cranial porosity.
Cribra orbitalia and porotic hyperostosis are identified as pathological conditions with an onset in infancy and early childhood and have potential etiologies that can be linked to inadequate consumption of animal protein (Walker et al. 2009). Therefore, individuals who may not have consumed sufficient dietary protein due to a diet high in vegetal foods are expected to have experienced reduced stature and have a higher chance of developing acquired anemia.
Organization of the Thesis
Chapter II provides the theoretical background for this study. The chapter begins with a description of the central California environment followed by an outline of the chronology used for prehistoric central California. The chapter ends with a discussion of evidence for resource intensification in central California and the associated skeletal health consequences.
Chapter III discusses the existing literature related to studies of stature and body proportionality. The chapter starts with a discussion of the estimation of stature in
8 archaeological contexts. Specifically, stature estimation methodology for archaeological
California populations is described, as well as previous studies of stature in prehistoric central California. The remainder of the chapter highlights trends in long bone proportionality.
Chapter IV provides a literature review on the definitions and etiologies of cribra orbitalia and porotic hyperostosis in a bioarchaeological context. The relationship between these two pathological conditions of cranial porosity is also discussed. The chapter concludes with a discussion of previous analyses of cranial porosity in archaeological populations.
Chapter V outlines the materials and methods used for this research, and
Chapter VI presents the results. Chapter V identifies the skeletal sample, osteometrics, paleopathological methods of data collection, and the statistical tests that will be used to compute the results. Chapter VII revisits the study’s research hypotheses in light of the results. This chapter also discusses the study’s limitations and potential for future research, and provides a summary to conclude the thesis.
This thesis contains two appendices. Appendix A provides images describing the measurements of femoral bicondylar length and tibial length used for analysis in this study. Appendix B consists of tables presenting the quantification of data and statistical results in this study, and is the same as the information presented as figures in Chapter
VI.
CHAPTER II
CENTRAL CALIFORNIA ENVIRONMENT
AND RESOURCE INTENSIFICATION
This chapter addresses the theoretical background for this study. Since the available resources within an environment are predicted to influence geographic variation in stature, body proportionality, and cranial porosity, this chapter will describe the central
California environment of the Central Valley and San Francisco Bay regions. A history and the definition of the occupational sequence that allows for temporal comparisons of stature, body proportionality, and cranial porosity will also be provided.
Furthermore, this chapter will review the literature on resource intensification models and evidence for dietary change, which outline how the available resources within regions of central California change throughout the Late Holocene. This chapter will end with a discussion of how these resource intensification models predict changes in body size and health, as well as bioarchaeological evidence for these changes.
Central California Environment
The sample used in this study is comprised of sites from the Central Valley and San Francisco Bay regions of California. The Central Valley is a vast and environmentally diverse region located in the central lowland of the state. The Valley is
750 km long and encompasses approximately 50,000 km2 of land (Moratto 1984:13).
9 10
Topographically, it is predominantly comprised of low-elevation river channels, alluvial plains, marshes, and old lakebeds surrounded by mountain ranges in all directions. The center of the Central Valley region lies just east of the San Pablo and San Francisco Bays.
The Sacramento Valley, Delta, and San Joaquin Valley comprise the three main divisions of the Central Valley. These three regions are recognized as both natural and archaeological divisions (Moratto 1984). The Sacramento Valley is the northern- most of the three, and the San Joaquin Valley is the southernmost. The Delta region lies in the center of the Central Valley, within both the Sacramento and San Joaquin Valleys.
The Sacramento River runs southwest and the San Joaquin River flows northwest to form the Delta (Moratto 1984; Schoenherr 1992). Freshwater from the Sacramento-San
Joaquin Delta flows west into the San Francisco Bay, where it mixes with saltwater from the Pacific Ocean (Moratto 1984). Populations in the Central Valley likely communally hunted mule deer, rabbits, and squirrels when available in the environment (Lightfoot and
Parrish 2009). Freshwater clams and mussels, crayfish, several species of anadromous fishes, and freshwater fish were prehistorically available as well (Lightfoot and Parrish
2009). Archaeological faunal assemblages have suggested that prehistoric populations in the Sacramento Valley area would have had access to a variety of large and small mammals, several species of fish, as well as pond turtles, ducks, and geese (Broughton
1994b). However, the relative abundance of these animals changed through time, where the proportion of larger mammals decreases in archaeofaunal assemblages relative to smaller vertebrate species (Broughton 1994b).
The San Francisco Bay region consists of bayshore, hill, and valley areas that surround the Carquinez Strait, Suisun Bay, and the San Francisco and San Pablo Bays.
11
The Bay Area has the largest estuarine system in all of California (Lightfoot and Luby
2002). These bodies of water cover approximately 1100 km2, but was likely much larger
(around 1800 km2) before the California Gold Rush (Moratto 1984:219). The surrounding prehistoric landscape included saltmarshes, redwood forests, grasslands, and mixed- evergreen woodlands (Moratto 1984). Because of this variety in ecological surroundings, the environment of the Bay Area is able to support an enormous diversity in species
(Lightfoot and Luby 2002; Schoenherr 1992). Abundances of game such as deer, elk, and waterfowl been documented by early explorers in the Bay Area. Sea mammals, abalone, mussels, oysters, clams, and several species of fish were also available in the environment (Lightfoot and Luby 2002; Lightfoot and Parrish 1996). Archaeologically,
Beardsley (1954) identifies shellfish from the mudflats or rocks of the beaches of the Bay
Area to be an important resource. Broughton (1994a) found that artiodactyls (such as pronghorn, elk, and black-tailed deer) and sea otters were abundant in Bay Area shellmounds, although the artiodactyls declined in relative abundance to the sea otters over time.
Several species of marine plants were available for consumption and other economical uses (Lightfoot and Parrish 2009). Abalones, snails, oysters, clams, and mussels are examples of the variety of shellfish in the prehistoric Bay Area. Aquatic invertebrates and crustaceans were also likely food sources for these prehistoric populations. Several species of anadromous fishes and few freshwater fish species were available to the Bay region (Lightfoot and Parrish 2009). Much like the more interior regions, the Bay Area had access to a variety of terrestrial animal resources. Bay Area
12 populations would have had access to sea mammals, which over time became an important food resource (Broughton 1994a).
Central California Chronology
Despite archaeological investigations in the central California region since the early 1900s, such as those by Uhle (1907) and Nelson (1909), the recognition of distinct temporal periods was not developed until the late 1920s. Schenck and Dawson (1929) published a tentative chronology for the northern San Joaquin Valley Delta region. This chronology suggested that sites within this region have distinctive cultural patterns throughout time. In the early 1930s, archaeological investigations in this same region by
Lillard and the Sacramento Junior College found cultural differences in archaeological material (Heizer 1939; Moratto 1984). Lillard and Purves (1936) proposed three distinct horizons from these sites, consisting of the Early, Intermediate, and Late Horizons, where the Intermediate strata appeared to be a transitional period between the Early and Late levels. These periods were defined by burial patterns, artifact types, and the condition of human bones (Lillard and Purves 1936). Recognized as the Delta sequence, Lillard et al.
(1939) later elaborated on the three periods identified in 1936, defining these periods by mortuary patterns, subsistence, artifacts, and Olivella shell bead types.
The chronological organization of the Delta sequence was adapted by
Beardsley (1948), and extended its application to the San Francisco Bay region.
Beardsley redefined the Intermediate Horizon as the Middle Horizon to suggest it was not a true transitional period, but rather a discrete horizon with characteristics of its own.
13
Finding that this dating system did not allow for much cultural variability,
Ragir (1972) proposed a system of distinction that involved regional characteristics rather than temporal phases. Ragir (1972) identified the Windmiller, Consumnes, and Hotchkiss cultures, loosely substituting them for the Early, Middle, and Late Horizons respectively.
Fredrickson (1973) later identified the Berkeley pattern (associated with the Middle
Horizon) and the Augustine pattern (associated with the Late Horizon). The Berkeley and
Augustine patterns replaced the Consumnes and Hotchkiss cultures identified by Ragir
(1972) to include additional cultural patterns observed in the San Francisco Bay region.
Bennyhoff and Hughes (1987) recognized that the shapes, sizes, and decorations of Olivella beads found in the archaeological record changed over time. From this, Bennyhoff and Hughes developed a chronology, known as Dating Scheme B1, which could be used to identify assemblages of specific shell types that are associated with distinct time periods. This system also changed the terminology from “Horizon” to
“Period”. However, this typology could not depend alone on the form of shell beads, and utilized radiocarbon dating, obsidian hydration dates, and mortuary data to gain a more accurate temporal placement (Bennyhoff and Hughes 1987; Groza 2002; Moratto 1984).
This was done in anticipation of situations of temporal overlap or hiatus in the manufacture of a specific bead form, such as a type found to be identical dating to the
Early and Late Periods but completely absent from the Middle Period. In such situations, they would need to be classified as different shell types. These developments in central
California chronology became known as the Central California Taxonomic System
(CCTS).
14
This study utilizes Dating Scheme D (Groza 2002), which is an adaptation of the CCTS Scheme B1 by Bennyhoff and Hughes (1987). Dating Scheme D is a dating system based on the calibrated accelerator mass spectrometry (AMS) dates of 103
Olivella shell beads that represented most of the periods and phases in the CCTS. Groza
(2002) found that the calibrated AMS analysis of the shell was mostly consistent with the typology of Bennyhoff and Hughes (1987) Scheme B1, but also identified some discrepancies. These discrepancies typically note that some time periods in Scheme B1 are earlier or later than originally recorded, as well as the appearance of a previously undiscovered phase of the Middle Period (Groza 2002). The time ranges associated with each period acknowledged in this study are Early (>3450-2450 BP), Middle (2450-940
BP), and Late (940-230 BP) Period.
Although these separations of time are arbitrary and may not be truly representative of any real division in time reflecting changes in culture, subsistence, or diet, this chronology is widely used in California archaeology and will provide the temporal basis for diachronic comparison in this study. It is recognized that the majority of chronological systems used in central California archaeology consist of sequential discrete periods of time that do not fully account for gradual changes or considerations of cultural interactions. As has been discussed in this section, the chronology for central
California has been repeatedly debated, revised, and researched, and will likely be subjected to such analysis again in the future. Likewise, Dating Scheme D requires more investigation due to the reservoir effect in dated shell remains. However, it provides a calibrated chronology that is better aligned with calendric time than previous systems.
15
Early Period (Windmiller and Lower Berkeley Pattern) >3450-2450 BP
Different regions in California are described by patterns that loosely correlate with the Early, Middle, and Late Periods. The Lower Berkeley Pattern is associated with the Early Period in the Bay Area. Cobble mortars, and a gradual shift from mobile forager economies to semisedentary land use characterize the Lower Berkeley Pattern
(Milliken et al. 2007). In the Bay Area, Early Period burials are flexed (Milliken et al.
2007). In the Valley and Delta regions, the Windmiller Pattern is associated with the
Early Period. Early Period burials are typically ventrally extended and oriented to the west with associated grave goods (Heizer 1949; Moratto 1984; Ragir 1972). Cremations are rare in this period. Moratto (1984) notes that sites dating to the Early Period are predominantly found in the Delta region.
Although the importance of vegetal foods to the diet during the Early Period has been debated, this period is represented by an abundance of large mammal exploitation, such as artiodactyls in both the Bay Area and Valley regions (Broughton
1994a, 1994b; Moratto 1984.). The atlatl was a common hunting tool during this period
(Basgall and Hildebrandt 1989).
Milling artifacts are present in this period, but primarily associated with burials rather than found in midden debris (Basgall 1987; Schulz 1981). These milling artifacts are predominantly millingstones, which are used to grind small seeds, and less commonly mortars and pestles, which are typically associated with acorn use (Basgall
1987). This implies that acorn consumption, also known as balanophagy, was limited at this time. In addition, quartz crystals, Olivella beads of Type A1a and L, and Haliotis
16 beads of rectangular or other decorated geometric shapes are examples of diagnostic artifacts found at Early Period sites (Moratto 1984).
Middle Period (Upper Berkeley Pattern) 2450-940 BP
The Middle Period is associated with the Upper Berkeley Pattern in the Bay
Area. In the Valley and Delta regions, the Middle Period is associated with the Berkeley
Pattern. Evidence from this time suggests a cultural influence from the Bay area on the
Valley and Delta cultures.
The Middle Period is marked by an increase in use of vegetal resources, specifically acorns, as suggested by the higher prevalence of mortars and pestles over millingslabs in the archaeological record (Basgall 1987:31) and archaeobotanical evidence (Wohlgemuth 1996). There is also evidence for increased consumption of fish compared to the Early Period (Basgall 1987; Broughton 1994a, 1994b).
Burials in the Middle Period are flexed rather than extended, and can follow any cardinal orientation (Basgall 1987; Moratto 1984). Cremations are rare, but have been found at Middle Period sites associated with funerary artifacts (Moratto 1984).
However, fewer grave goods are associated with burials and may imply greater social stratification. Aside from milling equipment, artifacts associated with the Middle Period include Olivella shell bead types C1 and F, and geometric Haliotis ornaments (Moratto
1984). The production of bone tools as developed in the Bay Area spread to the Valley during this period (Moratto 1984).
17
Late Period (Augustine Pattern) 940-230 BP
Late Period sites are found distributed widely throughout central California
(Moratto 1984). Bay Area and Sacramento Valley sites show many cultural similarities, associating the Augustine Pattern with the Late Period for both regions (Bennyhoff
1977). The Late Period also has flexed burials (Basgall 1987) but is characterized by a higher prevalence of cremations (Moratto 1984). Burial goods, sometimes of rare artifact types, are associated with only a small proportion of graves and imply more social stratification than in the Middle Period (Lightfoot and Luby 2002). Fish continue to be exploited in this period, but there is also a focus on intensive acorn gathering, fowling, and hunting. Associated with the focus on hunting in this period, new technology is introduced into the Bay Area from the Valley region in the form of the bow and arrow, characterized by smaller projectile points and tools for straightening arrow shafts
(Moratto 1984). Olivella beads of types E and M, trapezoidal and triangular Haliotis ornaments, flat-bottomed mortars and pestles, baked clay, and magnesite artifacts are other artifacts characteristic of Late Period sites (Heizer and Fenenga 1939; Moratto
1984).
Resource Intensification in Central California
Defined as a decline in efficiency as productivity per unit of land or capita increases, resource intensification is related to food productivity and the energy costs associated with obtaining and processing these food resources (Basgall 1987; Broughton
1994a, 1994b). Subsistence patterns in central California shifted from low cost, high- ranked taxa to use of more costly, smaller taxa during the Late Holocene (Broughton
18
1994a, 1994b). Around the same time that zooarchaeological evidence implies a shift from large to smaller game exploitation, the consumption of acorns increased (Basgall
1987; Broughton 1994a, 1994b). A predominant explanation for this pattern in
California’s archaeological record is resource intensification.
Resource intensification models suggest that with the growth in population during the Late Holocene, the relative abundance of high-ranked resources decreased
(i.e., resource depression) and shifted to the exploitation of lower-ranked resources.
California indigenous populations emphasized big-game hunting subsistence economies in the Early Period (Walker and Thornton 2002). Population growth in the Late Holocene is first attributed to territorial circumscription; then around the Middle Period it is attributed to greater diversification in diet and intensification of acorn exploitation (i.e., diet breadth expansion).
In numerous regions of California, a significant decrease in foraging efficiency occurred during the Late Holocene based on zooarchaeological evidence
(Broughton 1994a; Broughton 1994b). Broughton identified a temporal decline in the relative abundance of large mammals in the archaeological record, with an increase in small mammals in the Sacramento Valley and San Francisco Bay areas. Prey rank depends on overall caloric return, and archaeologically, larger body size is associated with high-ranked prey (Bayham 1979; Broughton et al. 2011). The prey rank model predicts that foragers will pursue only the prey that will provide the highest return for the least effort placed into capturing and processing those animals (Stephen and Krebs 1986).
After the Early Period, there is archaeobotanical evidence for increased dependence on acorns as compared to other small seeds (Wohlgemuth 1996, 2004).
19
Acorns were consumed but did not appear to contribute significantly to the diet in the
Early Period, as there was diversity in seed types during this period (Wohlgemuth 1996,
2004). The peak of archaeobotanical evidence for acorns in the Middle Period is expected since other evidence points to acorn intensification. Archaeologically, this is supported by an increase in the prevalence of mortars and pestles in the archaeological record
(Basgall 1987; Milliken et al. 2007; Rosenthal et al. 2007). By the Late Period, there was an intensive dependence on acorn production and consumption, even up until recent times as observed in ethnographic studies (Basgall 1987; Baumhoff 1963). However,
Wohlgemuth (1996, 2004) finds evidence that other small seeds also were important in the Late Period. Since the archaeological record often does not provide well-preserved paleobotanical assemblages to support these trends, artifact assemblages must also be analyzed. Thus, the abundance and distribution of mortars and pestles are used as a proxy for acorn use in the archaeological record. The primary purpose of the mortar and pestle was to process acorns, as supported by ethnographic evidence (Baumhoff 1963). In the region of the Central Valley Delta during the Early Period, milling equipment such as mortars and pestles were mainly associated in burials and not in middens, and therefore acorns were interpreted to be less important in the diet at this time (Basgall 1987). During the Middle Period, there was an increase in mortars and pestles in middens, which has been interpreted as evidence of intensified acorn processing and increased dependency on acorns (Basgall 1987:31).
Basgall (1987) and Ortiz (1991) both provide insight into the labor-intensive process of preparing acorns for consumption. Ortiz (1991) records her observations of traditional acorn preparation according to the Yosemite-area Miwok/Paiute in California.
20
Ortiz outlines acorn preparation in an eight-step process. First, the acorns must be harvested, then dried and stored, cracked and shelled, winnowed, pounded, sifted, leached of toxins, and cooked before they are ready for consumption. The exact methodology in acorn processing may vary geographically and culturally. Basgall (1987) stresses the high nutritional content of acorns as a subsistence resource. Although acorns are low in protein, they are about equal in carbohydrates and high in fats compared to other grains such as wheat and barley, and the high fat content makes them calorically superior (Basgall 1987:25).
Resource Intensification and Skeletal Indicators of Health
Patterns in skeletal health are commonly studied as biological consequences of sedentism and dietary change associated with the advent of agricultural practices, as well as support for the existence of the transition to these practices. Increased sedentism, population growth, and the development of agriculture are often correlated and have often been shown to have negative impacts on skeletal health despite agriculture’s purpose to provide nutritional resources (Cohen 1977). Linear enamel hypoplasias, dental caries, Harris lines, porotic hyperostosis, and cribra orbitalia are examples of indicators of skeletal health that can be used to analyze temporal patterns in prehistoric populations.
Typically, analysis shows a lower prevalence of these pathological conditions in pre- agricultural societies than in those that are undergoing an agricultural transformation
(Cohen 1977; Cohen and Armelagos 1984; Larsen 1995, 1997).
Although the subsistence economy in California is not agricultural like in other areas of North America, the adoption of acorn subsistence in California mirrors
21 patterns in health typically associated with agricultural development (Meighan 1959).
Furthermore, the intensification of acorns and storage in California was able to provide a reliable subsistence economy to support increases in population density as native populations became more sedentary. Because of this, patterns of skeletal indicators of stress that are commonly studied in agricultural transitions have also been analyzed in
California skeletal populations, and have been found to mimic the same patterns specifically the Central Valley (Bartelink 2006; Dickel et al. 1984; Ivanhoe 1995;
Kennedy 1960; Newman 1957; Schulz 1981), the San Francisco Bay regions (Bartelink
2006; Ivahnoe and Chu 1996) and in the Santa Barbara Channel Islands (Lambert 1993;
Lambert and Walker 1991; Walker 1986; Walker and Thornton 2002). The following sections will describe evidence for nutritional stress in the Central Valley, San Francisco
Bay, and Santa Barbara Channel Islands regions.
Central California: Central Valley
In the lower Sacramento Valley, a heightened prevalence of dental caries in the Late Period as compared to the Early and Middle Periods supports a major diet shift
(Kennedy 1960; Newman 1957). Bartelink (2006) found that proportion of teeth with caries is highest during the Early and Late Periods in the Sacramento Valley. These trends are not in exact agreement, but identify a high prevalence of caries in the Late
Period.
The relationship of stature and diet in prehistoric central California is a central issue examined in this study. Stature and body proportionality will be discussed more in- depth in the next chapter. However, studies have shown that stature declines in response to nutritional stress that is associated with the adoption of agricultural practices or major
22 shifts in diet (Cohen and Armelagos 1984; Mummert et al. 2011; Steckel et al. 2002), such as populations in the Central Valley (Broughton et al. 2010; Ivanhoe 1995). A previous analysis of stature in central California by Bartelink (2006) found that
Sacramento Valley populations experienced a decline in stature from the Early to Middle
Period, with a rebound in height from the Middle to Late Period. Females from the
Sacramento Valley in this study were also identified as the most affected by stature change (Bartelink 2006).
Cribra orbitalia and porotic hyperostosis are forms of cranial porosity also commonly studied in prehistoric subsistence transitions. These conditions are often studied due to their etiological link to nutritional deficiencies (Ortner 2003; Walker et al.
2009). Bartelink (2006) provides a temporal analysis that shows the prevalence of these cranial pathologies increased in the Sacramento-San Joaquin Delta region. The etiology and a more in-depth discussion of these pathological conditions and their application in this study are found in Chapter IV.
Central California: San Francisco Bay
There are fewer published studies on temporal patterns in bioarchaeological health in San Francisco Bay prehistoric populations than in some other regions of
California discussed in this chapter. However, some studies have identified trends in prehistoric Bay Area health. Ivanhoe and Chu (1996) found a decline in stature in Bay
Area skeletal samples that was slightly less pronounced than results from a similar study conducted by Ivanhoe (1995) on Sacramento Valley skeletal populations.
More recently, research by Bartelink (2006) identified several trends in skeletal health in the Bay Area. This study identified a reduction in femoral bicondylar
23 length (and by proxy, stature) from the Early to Middle Period in Bay populations. The prevalence of dental caries peaked in the Middle Period for females, although males showed no change. This study also found stable proportions of tibial periostitis, cribra orbitalia, and porotic hyperostosis through time in the San Francisco Bay, but a temporal increase in the Central Valley.
Southern California: Santa Barbara Channel Islands
Although southern California is not a region of focus in this study, research in this area provides support for a temporal health decline during large-scale economic transitions in California. Subsistence practices in this region shifted from practices such as hunting and gathering of both maritime and terrestrial resources to an intensified reliance on fishing (Erlandson 1991; Glassow 1980). Several studies have been conducted in this region showing a decline in prehistoric health (Lambert 1993; Lambert and Walker 1991; Walker 1986; Walker and Thornton 2002).
Walker (1986) found that the prevalence of porotic hyperostosis and cribra orbitalia increased over time in the Channel Islands. This study also found that the prevalence of these conditions was higher in island populations than mainland populations. This is a pattern similar to that observed in populations with iron- and protein-deficient maize-based diets, even though the Channel Islands population subsisted on of iron- and protein-rich marine diet. Lambert and Walker (1991) also found an increase in cribra orbitalia throughout time. Since these trends were also associated with fish-born parasites or contaminated water, it presents a case study where geographic location is also an important consideration in studying prehistoric health.
24
Lambert (1993) found a temporal decline in health in the Channel Islands, marked by an increase in the frequency of periosteal lesions and a decline in stature. This is further supported by Walker and Thornton (2002), in which trends of growth disruption and skeletal manifestations of infectious disease increase through time in the Channel
Islands.
Osteological Paradox
Traditional interpretations of health consequences from economic transitions like resource intensification have been debated. Wood et al. (1992) presented a paradoxical argument that suggests skeletons that show pathological lesions may actually be healthier than those who do not show any signs of disease. This concept is based on the logic that if an individual survived long enough to manifest the disease skeletally, they had less frailty than individuals who may have had a severe or acute episode of disease that caused death before any skeletal lesions were formed. In terms of studying health consequences from resource intensification, this indicates that the individuals with skeletal stress symptoms may not be the most frail or most stressed in any given population. However, in the context of this study, skeletons are understood to represent the biological adaptation to nutritional stress through stature, proportionality, and cranial porosity.
Summary
The literature shows that aspects of skeletal health associated with nutritional deficiencies can be negatively impacted by dietary change associated with population increase, sedentism, and environmental change. A temporal decline in stature and an
25 increase in cranial porosity has previously been observed in prehistoric central California, although this study will focus on a larger region that includes sites in both the Central
Valley and Bay Area, and the Interior Bay. Although the Early, Middle, and Late Periods encompass a large amount of time in each division that may obfuscate the true variation of trends in skeletal health, they provide a basis for temporal comparison of sites in the absence of absolute dates for each site sample skeletal remains. The next chapter provides a review of the literature on stature and body proportionality.
CHAPTER III
STATURE AND PROPORTIONALITY
This chapter examines the factors that influence stature during growth and development. Although primarily determined by genetics, aspects of body size can be used as a proxy for estimating status of environmental conditions such as nutrition. A description of how stature is reconstructed in bioarchaeological contexts will be presented, as well as the importance of population-specific estimation techniques. This chapter will also examine factors that influence proportionality. Body proportionality is an important consideration in archaeological stature estimation, since proportionality is also subject to environmental conditions such as climate and nutritional stress. Finally, the chapter will end with a discussion of how aspects of body size can be used as a proxy for nutritional stress in prehistoric contexts to estimate conditions of the prehistoric environment.
Stature
Although predominately dictated by genetics, stature is affected by environmental factors such as nutrition and disease. Individual differences in stature are primarily genetically determined, but at the population level these differences cancel out and average stature reflects environmental conditions (Steckel 2012). Skeletally, nutrition has the potential to control aspects of the growth and development of long bones and can
26 27 affect the timing of long bone epiphyseal fusion (Bogin 1999; Cameron and Demerath
2002). Nutritional stress during critical periods of growth and development, due to situations such as nutrient deficiencies or food scarcity, can cause delayed growth in juveniles and result in stunted adult stature (Bogin 1999; Cameron and Demerath 2002;
Fogel et al. 1983; Larsen 1995; Norgan et al. 2012; Steckel 2012). These critical periods for growth occur in early childhood and adolescence (Cameron and Demerath 2002;
Steckel 2012). Slowed growth leading to stunted adult stature can be attributed to deficiency in a single nutrient, such as protein, which is essential for normal growth and development (Norgan et al. 2012). In central California, such nutritional stress can be introduced when infants are weaned onto low-protein acorn-based complementary foods, such as gruels.
Improvements in social and economic factors allow for rapid increases in average stature (Steckel 2002). Such improvements are often interrelated, and can include enforcement of public health measures, higher income, and social equality. Other socioeconomic factors, such as urbanization, allowed the spread of disease, and result in declines in stature. Demanding physical labor is also suggested to constrain growth, especially for those that may have less efficient technology (and therefore higher energy expenditure) to complete tasks (Steckel 2012). Furthermore, culture may dictate practices that either directly or indirectly affect food distribution or restrict dietary choices that affect nutritional status.
A case study by Bogin et al. (2002) illustrates the importance of health on stature. This study examined the height of United States-born Maya immigrant children and was compared to that of Maya children in rural Guatemala. Children in both groups
28 were the offspring of adults from Guatemala, and those living in the United States were refugees from a civil war in Guatemala. The study found that Maya American children were on average 11.54 cm taller and 6.83 cm longer-legged. The Maya American children also had longer legs proportional to rest of body than the Maya in Guatemala.
These increases in average stature were attributed to better nutrition and health care in the
United States. This case study highlights that stature, and especially the length of legs is sensitive to environmental factors, and that stature is an adaptation to environmental conditions and can be used as a proxy for environmental factors such as nutrition.
Large-scale changes in subsistence economies, such as transitions to agriculture or intensified acorn use, have been associated with reductions in stature
(Cohen 1977; Cohen and Armelagos 1984). The following sections discuss the assessment of stature from prehistoric skeletal remains, and how stature has been used as a proxy for health in central California.
Stature Estimation Methods
Archaeological analyses of stature are usually strictly applied to adults due to a number of reasons. One is the potential for underrepresentation of juvenile remains in archaeological contexts and skeletal collections. This underrepresentation could be the result of previous paradigms in which it was thought that juvenile remains had little information to reveal (Ubelaker 1989), as well as issues with inadequate recovery
(Saunders 2008), and poor skeletal preservation (Walker 1995; Walker et al. 1988). It is also difficult to assign biological profiles to juvenile individuals, given the near impossibility for sex assessment before reaching puberty. Aging juvenile remains is also problematic since individuals may follow different developmental patterns such as
29 experiencing periods of catch-up growth (Goodman and Martin 2002). Despite the fact that juvenile individuals would be the best to study for the true effects of nutritional stress during growth and development, adults in the archaeological record represent those who became the best adapted and show the biological responses to the stressor.
Stature can be estimated using a few different methods. One method of skeletal stature estimation is an anatomical reconstruction method. This method requires the reconstruction of an individual’s height based on the summation of the heights of the cranium, vertebral column, femur, tibia, talus, and calcaneus, as well as a soft tissue correction factor (Fully 1956; Fully and Pineau 1960; Lundy 1985; Raxter 2006).
Typically, stature is estimated using regression formulae from reference populations, in which the measurement of a single skeletal element is used. These reference populations usually consist of known individuals, such as the decedents of European and African descent from the Terry Skeletal Collection analyzed by Trotter and Gleser (Trotter 1970;
Trotter and Gleser 1952, 1958).
However, the use of reference samples and general anatomical reconstruction formulae are problematic for archaeological populations. This is because stature and body proportions vary due to genetics and geography. A single reference group for application to all populations cannot accurately capture this variation, and therefore it is necessary for population-specific regression equations and soft-tissue correction factors. Furthermore,
Jantz et al. (1995) found that Trotter’s method of measurement for the tibia was not consistent by sometimes excluding the medial malleolus or intercondylar eminence.
Konigsberg et al. (1998) advocate for the use of reference samples that are representative
30 of the study sample in question, although these are not always available for stature estimation of unknown or archaeological remains.
Stature Estimation Methodology for Archaeological California Populations
Most of the estimation methods in the literature were developed for application to populations of European, African, and Asian ancestry. Regression equations for Asian populations have been used in lieu of an appropriate equation for indigenous New World populations. This is problematic since the equation for Asian populations was derived from samples including a mixture of various individuals of
Asian, Melanesian, Polynesian, Micronesian, and Native American descent that have been reported to have European ancestors (Auerbach and Ruff 2010). Due to this, some analysts have preferred to use formulae derived from a Mexican sample that has limited
European ancestral mixture (Genovés 1967). However, Auerbach and Ruff (2010) deemed the reliance on these methods inappropriate for use on indigenous American populations due to regional and temporal discrepancies in limb proportionality.
In response to the need for population-specific formulae, Auerbach and Ruff
(2010) recently published stature estimation equations for New World populations. Using the femur and tibia, Auerbach and Ruff (2010) generated new regression equations for prehistoric populations. Eleven cultural regions spanning North America were defined based on temporal and geographical proximity, as well as evidence of archaeological relationships. Although there is some degree of unequal temporal distribution within regions that may inflate the amount of morphological variation, this study provides the
31 most appropriate stature estimation method for New World populations currently available.
Across North America, it was found that there was considerable variation in stature and body proportionality. Therefore, rather than one equation for the application to all New World populations, several regional equations were developed. Auerbach and
Ruff (2010) grouped regions together based on their similarity in stature and body proportionality, specifically geographic regions that do not differ significantly in relative tibia length comparisons. Archaeological California populations are grouped with the
“Temperate” populations (US Southwest, Great Basin, Eastern Woodlands, and
Southeastern US regions) to which a set of sex-specific equations applies. The equations developed by Auerbach and Ruff (2010) for California populations are used in this study and are provided in Chapter V.
Stature in Prehistoric Central California
Significant reductions in stature have been identified in previous studies of central California health (Bartelink 2006; Broughton et al. 2010; Ivanhoe 1995; Ivanhoe and Chu 1996). Ivanhoe (1995) studied adult skeletons in the Central Valley of California spanning the Early to Late Periods and found skeletal stunting due to dietary calcium deficit over time as the diet shifted towards increased acorn consumption. Ivanhoe and
Chu (1996) also found a decline in stature in the San Francisco Bay. The greatest reduction in height was identified from the Early to Early-Middle Transition Period and between the earliest phases of the Late Period.
Using femoral bicondylar length as a proxy for stature, Bartelink (2006) found that stature decreased significantly from the Early to Middle Period for Sacramento
32
Valley and San Francisco Bay populations, but femur length rebounded in the Late
Period in Valley populations indicating a rebound in stature. Furthermore, Bartelink
(2006) identified greater sexual dimorphism in femoral length in the Middle Period for both Valley and Bay regions, which may imply that the stature of females was affected greater than the stature of males by a reduction in foraging efficiency throughout central
California at this time. Broughton et al. (2010) also used femoral bicondylar length of
Late Holocene skeletons for a temporal comparison of stature in the Sacramento Valley.
This study also identified a temporal decline in stature for both sexes over time.
Body and Lower Limb Proportionality
Body proportionality in humans is influenced by a number of factors. Aside from genetic factors, proportionality is similar to stature in that environmental factors are large contributors. Although somewhat interrelated, climate and diet composition can alter body proportionality (Bogin 2012). Bergmann’s and Allen’s rules describe how climate may directly affect body proportionality, where greater body mass is found in organisms in colder climates (Bergmann 1847) and appendages are shorter in colder climates (Allen 1877) to increase volume-to-surface area ratio to maximize heat retention. However, climate can also indirectly affect body proportionality by influencing availability of food resources and therefore nutritional intake.
A prevailing trend in the secular analysis of long bone proportionality is that the distal long bones are the most variable when compared to the proximal long bones of the same limb. In their study of long bone length and long bone allometry of mid-19th century to mid-20th century American skeletal samples, Jantz and Jantz (1999) found that
33 changes in the proportion of long bones are more notable in the distal elements. Holliday and Ruff (2001) also support greater variability in the distal limb bones when compared to proximal elements.
Males also appear to have been more biologically sensitive to environmental factors or stressors than females, showing stronger secular change (Jantz and Jantz 1999;
Malina et al. 2004). The authors attribute the driving forces behind these secular changes in stature and proportionality to environmental factors such as nutrition and disease. This study (along with Tanner et al. 1982) showed that the lower limbs disproportionately contribute to changes in stature. Jantz and Jantz (1999) identify the tibiae as the largest factor in considering stature change, observing that it showed the strongest positive allometry with increasing stature.
Pelin and Duyar (2003) compared the proportionality of long bone lengths in
Turkish males to determine usefulness of the tibia in stature estimation. The Turkish study sample was separated into three groups consisting of short, medium, and tall individuals. They found that the relative tibia length to height increased as stature increased, although not isometrically.
The tibia and fibula have been shown to be more positively allometric than the femur (Meadows and Jantz 1995), which is supported by populations with recent improvements in diet and socioeconomic status showing positive allometry in lower limb length to stature increases (Bogin et al. 2002; Tanner et al. 1982). Meadows and Jantz
(1995) also found that upper limbs show negative allometry in situations of longer lower limb length and heightened stature.
34
However, all of these studies do not identify a cause for this trend of tibial sensitivity. As has been determined in previous sections of this chapter, human growth is very plastic and sensitive to environmental conditions. Body parts that develop at the fastest rate during critical periods of growth will then be the most affected by adverse environmental conditions (Bogin 2002). The legs (and especially the tibia) are the fastest developing bones in humans from birth up until around seven years of age (Bogin 2012).
Therefore, measurements of total leg length, femoral length, and especially tibial length are valuable indicators for inferring nutritional stress.
Summary
Studies have shown that the lower limbs disproportionately contribute to stature, as well as identifying the tibia as being most sensitive to changing environmental conditions. This provides support for using these measurements as proxies for stature, and that the assessment of proportionality using long bones in the lower limb can provide information about environmental conditions. Previous research examining nutritional stress in central California has identified a temporal decline in stature, as well as regional variation in stature. The next chapter will discuss cribra orbitalia and porotic hyperostosis, which are two other indicators of stress.
CHAPTER IV
CRANIAL POROSITY
Pathological conditions, such as cranial porosity observed as macroscopic porous lesions on various regions of the skull, are commonly reported in archaeological skeletal samples. Cribra orbitalia and porotic hyperostosis, the two conditions of cranial porosity relevant to this study, are understood to be skeletal indicators of health often tied to nutritional stress. These pathological conditions are often thought to be a skeletal response to anemia, but histological and clinical evidence suggest that other conditions may also cause similar lesions. This chapter will provide a description of each pathological condition, followed by hypotheses regarding the etiology and relationship of cribra orbitalia and porotic hyperostosis. The chapter will end with a brief discussion of how they are interpreted as indicators of health in archaeological contexts.
Cribra Orbitalia
Cribra orbitalia refers to a pathological condition found on the superior roof of the eye orbit with a spongy, porous, sieve-like appearance (Goodman and Martin 2002;
Ortner 2003). Orbital lesions are usually bilateral (Nathan and Haas 1966; Ortner 2003;
Stuart-Macadam 1989). These orbital lesions are formed from marrow hypertrophy and the subsequent enlargement of cranial vault marrow spaces (or diploë) as a response to nutritional deficiency (Ortner 2003). As a response to the enlarged diploë, bony
35 36 remodeling forms circumscribed porous lesions on the roof of the eye orbit. Histological analysis has shown a thinning of the outer table of the orbit and enlarged trabeculae, as well as the intrusion of the marrow under the periosteum (Nathan and Haas 1966; Schultz
1993).
Porotic Hyperostosis
Porotic hyperostosis is a pathological condition observed in cranial bones such as the frontal (located in areas other than the orbital plate), parietal, and occipital bones
(Goodman and Martin 2002). The parietal bones are the most commonly affected bone, followed by the occipital and the frontal bones, respectively (Hrdlička 1914; Stuart-
Macadam 1982). This pathological condition is macroscopically observed as areas of porosity similar in appearance to cribra orbitalia on the ectocranial surface, and is usually found bilaterally (Stuart-Macadam 1989).
Angel (1966) first coined the term “porotic hyperostosis” to describe cranial lesions that were usually diagnosed as “symmetrical osteoporosis”. Angel furthermore suggested that the term “porotic hyperostosis” include the lesions similar in appearance on the orbital roofs. Much like cribra orbitalia, histological analysis of cranial vault lesions shows enlargement of trabecular bone, and thinning of the outer tables of cortical bone. In these lesions, the trabeculae consisted of enlarged spaces that opened up the marrow space to the surface beyond the outer table, contributing to its porous appearance
(Schultz 1993).
37
Etiology of Cribra Orbitalia and Porotic Hyperostosis
The literature largely agrees on the macroscopic characteristics of cribra orbitalia and porotic hyperostosis. It also generally accepted that both pathological conditions result from the enlargement of the diploë through marrow hyperplasia, eventually resulting in bone remodeling. However, the exact etiology of these pathological conditions is debated. The following section presents a discussion on the predominant hypotheses for the causes of porous cranial lesions.
The Anemia Hypothesis
The predominant literature attributes the etiologies of cranial porosities to include iron-deficient anemia, megaloblastic anemia, or hereditary hemolytic anemia.
Anemia, or in literal terms “without blood”, is a pathological symptom that can occur as a secondary response to other diseases in which there is an abnormality in red blood cells affecting the ability to circulate oxygen (Ortner 2003).
Red blood cell production is usually isometric to red cell destruction in a healthy individual. Anemia is mainly characterized by a disruption in the blood cell production to destruction ratio (Walker et al. 2009). Amino acids, iron, vitamins A, B12,
B6, and folic acid maintain red blood cell homeostasis (Martini and Ober 2001). Iron is a very important component of hemoglobin and is necessary for red blood cell production
(Ponka 1997:1), which is a protein in red blood cells that binds to oxygen and allows for its transport throughout the body. Skeletal reactions are usually a last resort in the body’s response to anemia, in which hematopoietic marrow increases red blood cell production and the diploë intrudes on the outer lamina of flat bones (Ross and Logan 1969).
38
Only a few types of anemia can affect the skeleton such as thalassemia major, sickle cell anemia (or sicklemia), and hereditary spherocytosis. Thalassemia major, sicklemia, and hereditary spherocytosis are commonly grouped together as hereditary hemolytic anemias, since red blood cells in these conditions are characterized by short lifespans. Thalassemia major is a genetic condition concerning the deficient synthesis of hemoglobin, and can affect multiple bones other than the skull (Ortner 2003). Sickle cell anemia is another genetic form of anemia that with the presence of the hemoglobin S gene, affected persons have sickle-shaped red blood cells that are less effective in oxygen transport, have shorter cell lifespans, and can obstruct vascular pathways. Ortner
(2003:367) suggests sicklemia can affect bone by requiring more space for enlargement of the hematopoietic marrow, and such changes are primarily observed in the diploë of the skull. Hereditary spherocytosis describes a condition of large, globular
(megaloblastic) red blood cells that are destroyed before the typical cell lifespan (Ortner
2003). Hemolytic spherocytosis is usually only reflected in the enlargement of the cranial diploë, although this result is minimally expressed.
Porotic hyperostosis was first associated with anemia in skeletal populations by J. Lawrence Angel (1966), in which he observed porotic hyperostosis in areas of
Greece where thalassemia and sicklemia were common. The porotic hyperostosis was assumed to be a result of these anemias and presumed to be a balanced polymorphic defense against malaria. This was further supported by clinical evidence for development of porotic hyperostosis in anemic individuals (Moseley 1974). There is also clinical evidence for hereditary hemolytic anemia as a cause for porotic hyperostosis
(Hershkovitz et al. 1997). Stuart-Macadam (1982) provides support for anemia as a cause
39 of cranial porosity by comparing clinical evidence including macroscopic, microscopic, radiographic, and demographic information. The conditions causing anemia in archaeological contexts have been associated with lower standards of living, which can include sanitation issues, disease, and nutrient deficiencies (Walker 1985, 1986; Stodder
2006).
Walker et al. (2009) show support for hemolytic and megaloblastic anemias as explanations for porotic hyperostosis over iron-deficiency anemia, although not exclusive explanations. This is because these categories of anemias have potential to stimulate a higher production of mature red blood cells, and therefore marrow hypertrophy causing porotic hyperostosis. Furthermore, in these situations of hemolytic or megaloblastic anemia, it is assumed that sufficient iron stores are present to assist in the body’s response to compensate for red blood cell loss by expanding marrow spaces (Walker et al. 2009). This study also suggests that cribra orbitalia may result from hemolytic and megaloblastic anemias, but may also be due to vitamin deficiencies, and therefore has a slightly more complex etiology.
The Synergistic Approach: Vitamin Deficiencies
Despite the iron-deficiency anemia hypothesis’ grip on the paleopathological community, some inconsistencies with diagnoses of anemia have been identified. For example, in a study of a Sudanese skeletal sample, Wapler et al. (2004) found that approximately half of cribra orbitalia cases were not histologically consistent with an anemia diagnosis. As alternative explanations, Wapler et al. (2004) suggest the potential for inflammation, osteoporosis, and pseudopathological cases where postmortem erosion
40 may have worn through part of the ectocranial lamina. Also, in consideration of the study of prehistoric populations in the Americas, hereditary anemia was not present until contact with European explorers (Stuart-Macadam 1992a).
Furthermore, it has been argued by Walker et al. (2009) that iron-deficiency anemia cannot be the cause of porous cranial lesions. This is because iron is a necessary component of hemoglobin and red blood cell production. Since iron-deficiency anemia means a reduction in red blood cell production and can cause hemolysis, the enlargement of hemopoietic marrow space that requires the increased production of red blood cells, and subsequently causes porotic hyperostosis, is not possible.
It has been suggested that a combination of inadequate diets, sanitation, disease, or cultural practices may be better explanations than just a single cause
(Mensforth et al. 1978; Walker et al. 2009). Specifically, the lack of vitamins B9 and B12 from animal sources are identified as a cause of megaloblastic anemia that can be manifested as porous cranial lesions. Vitamin B12 is derived almost exclusively from animal-based foods and those with low consumption of animal product commonly experience B12 deficiencies. This deficiency can also be passed on to infants if the breastfeeding mother is deficient, causing megaloblastic anemia from birth since birth stores of B12 are low (Allen 1994; Stabler and Allen 2004).
In addition, poor sanitation practices and high population density can result in diarrheal diseases and gastrointestinal parasites (Crompton 1999; Goncalves et al. 2003).
This can cause nutrient loss and malabsorption of vitamins B9 and B12, which can lead to megaloblastic anemia (Walker et al. 2009). In the interpretation of parasitic infections or diseases that inhibit nutrient absorption, porotic hyperostosis may not represent dietary
41 deficiencies. Rather, cranial porosity could be the result of an adaptive response to reduce bioavailable nutrient access to the pathogen or parasite (Stuart-Macadam 1992b). This minimizes diet as a factor in some situations of cranial porosity, aside from cases of malnutrition or introduction of parasites from food resources.
Subperiosteal hematomas and blood clots resulting from scurvy, rickets, hemangiomas, and trauma can also produce orbital porosity by forming subperiosteal new bone on the orbital plate (Walker et al. 2009). Of these diseases, orbital lesions are more commonly seen in scurvy, which is a condition of vitamin C deficiency. Vitamin C promotes healthy Sharpey’s fibers to support connective tissue, in which a deficiency can detach the periosteum of the orbital roof and cause subperiosteal bleeding and new bone formation, resulting in a porous lesion (Walker et al. 2009). However, it has been documented that scurvy shows a diagnostic pattern in its expression in the skeleton that can aid in diagnosis. The patterns in skeletal expression of scurvy varies dependent upon the age of the affected individual, but usually appear as porous lesions or pitting evident in the sphenoid, and alveolar processes of the maxillae and mandible, cranial vault, or orbital roof (Ortner 2003).
Relationship of Cribra Orbitalia and Porotic Hyperostosis
The areas for red blood cell production change from the cranial diploë and long bone medullary cavities during childhood and adolescence to the spleen and marrow of the axial skeleton in adulthood (Hoffbrand and Lewis 1981). This is evidence for potential juvenile onset of cribra orbitalia and porotic hyperostosis in situations of
42 marrow hypertrophy. Stuart-Macadam (1985) found that adult lesions of the cranial vault and orbital roof are typically the result of healed episodes of childhood anemia.
Porotic hyperostosis and cribra orbitalia often co-occur and also thought to result from the same pathological process, suggesting the two conditions are linked
(Angel 1966; Roberts and Manchester 2005; Stuart-Macadam 1989). Stuart-Macadam
(1982, 1987a, 1987b) further supported this hypothesis with clinical evidence. However,
Walker (1985, 1986; Walker et al. 2009) states that there is a weak correlation between the two forms of cranial porosity, and typically one will occur in higher frequencies over the other in a given population. In most paleopathological analyses, cribra orbitalia is found in higher frequencies (Steckel et al. 2002; Walker et al. 2009).
The higher prevalence of cribra orbitalia in skeletal collections could be due to its potential for earlier onset than porotic hyperostosis. Hrdlička (1914) suggested porous lesions on the cranial vault began from the orbit, and then radiated to other areas of the skull. Orbital lesions have been observed during infancy, which supports Hrdlička’s hypothesis (Stuart-Macadam 1985). Stuart-Macadam (1989) suggests that the common factor between cribra orbitalia and porotic hyperostosis is anemia since clinical evidence shows cranial and orbital thickening for certain anemias.
However, porotic hyperostosis can occur on the skull without orbital lesions, and could be the result of separate etiologies. Walker et al. (2009) suggest that cribra orbitalia could result from a different variety of vitamin deficiencies than porotic hyperostosis. They suggest that severe vitamin B12 deficiency in infancy can cause marrow hypertrophy in both the cranial vault and orbital roof, while a severe vitamin C deficiency in infancy can only cause cranial roof porosity and would not affect other
43 cranial vault bones. Because of the potential for different etiologies, porotic hyperostosis and cribra orbitalia should be scored and analyzed separately in bioarchaeological analyses.
Cranial Porosity in Archaeological Populations
Bioarchaeological examinations of cranial porosity are typically considered in the context of transitions to agricultural practices and diet change. The adoption of agricultural practices is characterized by sedentism and increased population density
(Cohen 1977). In a study by Kent (1986), the aggregation of people and sedentism resulted in a higher prevalence of cranial porosity, rather than diets low in animal protein.
Using a case study of the Anasazi in the American Southwest, Kent attributed this to an increase in parasitic, viral, and bacterial diseases that lead to nutritional deficiencies and anemic responses in the skeleton.
There is much support for a trend of increased prevalence of cranial porosity in societies undergoing large-scale subsistence transitions (Broughton et al. 2010; Cohen and Armelagos 1984; Kent 1986; Larsen 1995; Steckel et al. 2002). Bartelink (2006) found that there was an increase in the proportion of individuals with porotic hyperostosis and cribra orbitalia over time in the Sacramento Valley of California, associated with resource intensification. Although this temporal trend was not found in San Francisco
Bay skeletal samples, Bartelink (2006) found that cribra orbitalia and porotic hyperostosis had a higher prevalence in the San Francisco Bay area when compared to samples in the Central Valley.
44
It has been documented that cranial porosity occurs in high frequencies in archaeological coastal populations (Bartelink 2006; Cybulski 1977; Holland and O’Brien
1997; Ubelaker 1992; Walker 1986). Helminths, a type of worm-like intestinal parasite, are much more viable in coastal regions because of preferable conditions such as lower elevations, warmer environments, and higher diversity of organisms in the ecosystem
(Dunn 1972). Parasites also flourish in lower sanitary conditions caused by sedentism
(Dunn 1972).
Bathurst (2005) presents archaeological evidence for helminths in shell middens in Canada’s Pacific coast. An abundance of preserved fish tapeworm (Diphyllobothrium spp.) and human roundworm (Ascaris lumbricoides) eggs were found in human coprolites within these coastal shell middens. Consumption of raw or undercooked fish, as well as birds or mammals that have consumed the fish, can introduce fish tapeworm to the human intestinal system (Bathurst 2005). Diphyllobothrium latum is the only known species of fish tapeworm that can cause vitamin B12 deficiency in humans (von Bonsdorff
1977), which has been found in high prevalence in the regions used in the Bathurst
(2005) study. This species has also been found in a variety of anadromous salmon species in the Pacific regions (von Bonsdorff 1977; Ruttenber et al. 1984). Human roundworm is transmitted by consumption of food or water containing roundworm eggs (Bathurst
2005). Although evidence of these parasites have not been studied in prehistoric central
California populations, it is likely that pathogens or parasites introduced by food sources are likely causes of high porotic hyperostosis and cribra orbitalia frequencies in prehistoric coastal populations.
45
Summary
While the literature has identified anemia as a default etiology for cranial porosity, it is clear that anemia is not the exclusive cause. From these hypotheses, nutritional deficiencies are a common denominator. Furthermore, it is evident that while the two conditions often co-occur, different processes may cause them.
Because of its etiology in nutritional deficiency, cribra orbitalia and porotic hyperostosis prove to be useful indicators in studying evidence of nutritional stress.
Previous studies show temporal increases in the prevalence of cranial porosity in societies undergoing agricultural transitions, as well as in populations located in coastal regions.
Therefore, for this study, the analysis of cranial porosity will be used in conjunction with stature and body proportionality to study nutritional stress context of intensified acorn use in prehistoric central California. Furthermore, evidence for high frequencies of porotic hyperostosis and cribra orbitalia in archaeological coastal populations may be associated with parasitic infections contracted from eating fish or being in contact with contaminated food and water. The next chapter will introduce the skeletal sample for this study, as well as the methods that will be used to examine stature, body proportionality, and cranial porosity.
CHAPTER V
MATERIALS AND METHODS
This chapter introduces the archaeological sites used in this analysis, as well as the skeletal samples from these sites and the occupation periods in which the skeletal remains are associated. This chapter explains how sites will be grouped together for regional analyses relative to their location to the San Francisco Bay, Interior Bay, and
Central Valley regions of central California. The relative location of each site highlights the availability of resources and how this availability changed over time as described in
Chapter II, which is predicted to influence body size and pathological conditions of cranial porosity. The chapter will then discuss the osteological methods used for data collection, and the statistical tests that will be used to assess temporal and regional trends of body size and cranial porosity.
Archaeological Sites
Central California Sample
A total of 669 skeletal individuals housed at the University of California at
Berkeley’s Phoebe A. Hearst Museum of Anthropology (PAHMA) from 21 archaeological sites in central California will be used for this study. These sites are located in present-day Alameda, Contra Costa, Sacramento, and San Joaquin counties
(see Figure 1). Four sites are in Alameda County, including CA-ALA-307 (West
46 47
Figure 1. Map of archaeological sites. (Map by Kevin Dalton)
Berkeley), CA-ALA-309 (Emeryville Shellmound), CA-ALA-328 (Patterson), and CA-
ALA-329 (Ryan). Nine of the 21 sites are in present-day Contra Costa county, including sites CA-CCO-020 (Dal Porto), CA-CCO-138 (Hotchkiss), CA-CCO-139 (Simone), CA-
CCO-141 (Orwood #2), CA-CCO-146 (Holland Tract), CA-CCO-150 (Veale Tract #1),
CA-CCO-151 (Sobrante), CA-CCO-250 (Maltby), and CA-CCO-259 (Fernandez). Three sites are in Sacramento County, including CA-SAC-006 (Johnson Mound), CA-SAC-43
(Brazil Mound), and CA-SAC-60 (Hicks). The remaining five sites are in present-day
48
San Joaquin County, including sites CA-SJO-068 (Blossom Mound), CA-SJO-142
(McGillivray), CA-SJO-154 (Cardinal), CA-SJO-105 (Park Woods) and CA-SJO-106
(Castle).
Individuals from these sites were grouped by time period for each region (see
Table 1). The Early Period sample is represented by burials from sites CA-ALA-307,
CA-ALA-328, CA- SJO-068, and CA-SJO-142. The Middle Period sample is represented
Table 1. Early, Middle, and Late Period Skeletal Samples
Time Sites Male Female Indeterminate Total Period Sex N N N N Early ALA-307, ALA-328, SJO- 67 74 7 148 068, SJO-142
Middle ALA-307, ALA-309, ALA- 143 150 15 308 328, ALA-329, SAC-043, SAC-060, SJO-154, CCO- 020, CCO-139, CCO-141, CCO-146, CCO-151, SJO- 106
Late ALA-328, ALA-329, SAC- 85 119 9 213 006, SAC-043, SAC-060, SJO-154, CCO-138, CCO- 150, CCO-250, CCO-259, SJO-105
Total 295 343 31 669
by burials from the sites CA-ALA-307, CA-ALA-309, CA-ALA-328, CA-ALA-329,
CA-SAC-043, SAC-060, CA-SJO-154, CA-CCO-020, CA-CCO-139, CA-CCO-146,
CA-CCO-151, CA-CCO-259, and CA-SJO-106. Burials from CA-ALA-328, CA-ALA-
329, CA-SAC-006, CA-SAC-043, CA-SAC-060, CA-SJO-154, CA-CCO-138, CA-CCO-
49
150, CA-CCO-250, CA-CCO-259, CA-SJO-105, CA-CCO-138, CA-CCO-150, CA-
CCO-250, and CA-SJO-105 comprise the Late Period sample. To increase sample size, burials dated to transitional periods were grouped with the period where the bulk of the site occupation extends. For example, all burials from CA-CCO-250 (Maltby) are dated to the Middle/Late Transition Period and extend into the first and second phases of the
Late Period, and are therefore grouped with the Late Period sites.
Sites were furthermore grouped by region. The sites are aggregated in
Bayshore, Interior Bay, or Central Valley floor regions (see Table 2). Sites close to the
San Francisco or San Pablo Bay shores are labeled “Bayshore” sites; those that are near
Table 2. Sites by Region in Central California
Region Sites Male Female Indeterminate Total Sex N N N N Bayshore ALA-307, ALA-309, 106 118 14 238 ALA-328, ALA-329, CCO-151, CCO-250, CCO-259 Interior Bay CCO-020, CCO-138, 65 84 2 151 CCO-139, CCO-141, CCO-146, CCO-150 Central SAC-06, SAC-043, 125 141 15 280 Valley SAC-60, SJO-068, SJO-105, SJO-106, SJO-142, SJO-154 Total 295 343 31 669
the Bay but located closer to the Central Valley near or the Sacramento and San Joaquin
Delta are labeled as “Interior Bay” sites; and sites located on the Central Valley floor are labeled “Valley”. Seven sites are in the Bayshore region, including CA-ALA-307, CA-
50
ALA-309, CA-ALA-328, CA-ALA-329, CA-CCO-151, CA-CCO-250, and CA-CCO-
259. Six sites from Contra Costa are located between the Bayshore and the Valley in the
Interior Bay region, including CA-CCO-020, CA-CCO-138, CA-CCO-139, CA-CCO-
141, CA-CCO-146, and CA-CCO-150. The remaining eight sites are located in the
Central Valley, including CA-SAC-006, CA-SAC-043, CA-SAC-060, CA-SJO-068, CA-
SJO-105, CA-SJO-106, CA-SJO-142, and CA-SJO-154.
CA-CCO-020
The skeletal sample from Dal Porto (CA-CCO-020) in this study is from a
Middle Period occupation. This archaeological site is located in present-day Contra Costa
County. The Dal Porto sample is grouped in the Interior Bay region due to its location near the Sacramento-San Joaquin Delta, which is between the San Francisco Bay Area and the Central Valley. Within the Interior Bay, Dal Porto is located closer to the Central
Valley than the Bayshore regions. Dal Porto is the northernmost Contra Costa site used in this study.
CA-CCO-138
The Hotchkiss Mound (CA-CCO-138) is a Late Period occupation site located near the Delta in Knightsen, California (Atchley 1994; Lillard et al. 1939). Radiocarbon and obsidian hydration analysis have provided dates for the site between approximately
AD 700 and AD 1800 (Atchley 1994; Clark 1964; Heizer 1958). The site has been excavated several times since the 1930s, revealing hundreds of burials (Johnson 1937).
Lillard et al. (1939) note that burials are typically flexed and laying on their side or back, and only a small amount of burials are cremated.
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CA-CCO-139
The Simone site (CA-CCO-139) represents a Middle Period occupation located in the Interior Bay region, south of the Delta. Burial positions at this site vary, from full extension to tightly flexed and laying on the side (Johnson 1939). According to notes by Johnson (1939), square unperforated Haliotis ornaments, large round Haliotis discs, pestles, quartz crystals, obsidian blades and projectile points, and Olivella beads were found associated with burials.
CA-CCO-141
Orwood #2 (CA-CCO-141) is a Middle Period site south of the Delta in the
Interior Bay region. Olivella saddle-shaped beads and flat circular beads were found at this site. Haliotis ornaments and steatite ear-plugs were also found. Burial positions vary at this site and reflect specific postures typically seen in Early Period or Late Period burials, but these appear to be localized phenomena at the site. As support for CA-CCO-
141 as a Middle Period site, the shell beads and other artifacts present at this site are characteristic of intensive occupation during the Middle Period (Lillard et al. 1939).
CA-CCO-146
Holland Tract (CA-CCO-146) is a Middle Period site located near the Delta in the Interior Bay region. This site is the closest to the San Francisco Bay region of all the
Interior Bay Contra Costa sites. Burials at this site are typically in an extended posture
(Rosenthal et al. 2007).
CA-CCO-150
Veale Tract #1 (CA-CCO-150) is a Late Period site located on a 200-foot long
S-shaped sand ridge located in the Interior Bay region (Lillard et al. 1939). Burials at the
52 site are flexed, and lay on their back or side. Olivella shell bead types 1b and 2a, as well as Haliotis ornaments of type C.1.a are associated with the burials (Lillard et al. 1939). A steatite pipe-bowl and Haliotis ornaments type M.C.2.a and M.C.3.a. are also associated with burials, and appear to be the only appearance of these types of artifacts in the delta region.
CA-CCO-151
The Sobrante site (CA-CCO-151, also known as the Philippi site) is dated to the Middle Period. Type II “Acorn” style atlatl spurs are found in the Sobrante Mound, made of bone or antler. The presence of these Type II atlatl spurs is indicative of a central
California Middle Period site due to their association with specific types of shell beads and ornaments (Payen and Johnson 1965; Riddell and McGeein 1969). Field excavation records from 1950 and 1951 indicate burials at this site are typically flexed, although some extended burials were found in the mound. Other artifacts at this site include obsidian blades, small circular Olivella beads and rectangular shaped Haliotis ornaments.
CA-CCO-250
Maltby (CA-CCO-250) is a Late Period site located near the San Francisco
Bay region that was surveyed by Nelson in the early 1900s (Lillard et al. 1939; Nelson
1909). Burials at this site are fully flexed and lay on the side. Powdered red ochre,
Olivella shell bead types, and Haliotis ornaments associated with these burials are characteristic of a Late Period occupation (Lillard et al. 1939).
CA-CCO-259
The Fernandez site (CA-CCO-259) is a Late Period shellmound located 8 km
(approximately four and a half miles) from the Bay, and is therefore grouped with the
53
Bayshore sites in this study (Davis 1960; Moratto 1984). Even given this slight distance from the actual bayshore, the mound was rich in mollusk shells. The mound also contains burials as well as cremations. Three components were identified at the site: Components
A (0-137cm), B (137-183cm), and C (below 210cm) (Davis 1960; Moratto 1984).
Component A is distinct by the presence of a variety of beads associated with cremations, including clamshell disks, magnesite and steatite beads, lipped and punched
Olivella beads, and baked clay balls. The presence of rectangular Olivella beads, several types of Haliotis ornaments, and cremations mark Component B. Olivella saddle beads, circular Haliotis ornaments, cobble mortars, and red ochre associated with flexed burials are characteristic of Component C.
CA-SJO-105
The skeletal sample from the Park Woods (CA-SJO-105) site dates to the Late
Period occupation. This site is located in the northern San Joaquin Valley north of
Stockton and east of the Delta. Park Woods is the northern-most of the San Joaquin
County samples in this study.
CA-SJO-106
Castle (CA-SJO-106) is a Middle Period site located in the northern San
Joaquin Valley. The site is characterized by extended burials located near side streams and axial marshes (Rosenthal et al. 2007). These characteristics are associated with the descendants of the Windmiller culture (Bennyhoff 1994a, 1994b; Rosenthal et al. 2007).
Comparative Skeletal Samples
The remaining sites used in this study are comparative data previously collected and described by Bartelink (2006). These sites are from Alameda, Sacramento,
54 and San Joaquin counties. The four Alameda County sites from this comparative sample are located near the bayshore. CA-ALA-307 (West Berkeley – Early and Middle Period site) and CA-ALA-309 (Emeryville Shellmound – Middle and Late Period site) are located in the upper East Bay Area of California. CA-ALA-328 (Patterson – Early,
Middle, and Late Period site), and CA-ALA-329 (Ryan Mound – Middle and Late Period site) are situated near the southeastern edge of the San Francisco Bay.
The sites in San Joaquin and Sacramento County are all located in the Central
Valley. Sites CA-SAC-006 (Johnson Mound – Late Period site), CA-SAC-043 (Brazil
Mound – Middle and Late Period site), and CA-SAC-060 (Hicks – Middle and Late
Period site) are all in the lower Sacramento Valley near the Delta. CA-SJO-068 (Blossom
Mound – Early Period site), CA-SJO-142 (McGillivray site – Early Period site), and CA-
SJO-154 (Cardinal Mound - Middle and Late Period site) are all located in the upper San
Joaquin Valley near the Delta.
Data Collection Methods
Sex and Age Estimation
Previously, Bartelink (2006) assessed the sex and age-at-death of all individuals in this study sample using standards outlined in Buikstra and Ubelaker
(1994). The study sample consists of only adults so that all individuals analyzed were assumed to have reached adult stature. A number of methods were used to assess age based on the availability of skeletal elements for each individual. If available, the innominate was used for pubic symphyseal (Brooks and Suchey 1990; Buikstra and
Ubelaker 1994) and auricular surface aging (Buikstra and Ubelaker 1994; Lovejoy et al.
55
1985). Cranial suture closure (Buikstra and Ubelaker 1994; Meindl and Lovejoy 1985) was also used for age assessment. In addition, epiphyseal union of the iliac crest, the acetabulum, the medial clavicle, the sacrum, the basilar suture, and long bones were also considered in age assessments.
Sex was assessed from the pelvis as well as the cranium according to standards outlined in Buikstra and Ubelaker (1994). This included scoring criteria on the innominate such as the ventral arc, subpubic concavity, greater sciatic notch, and the preauricular sulcus. Attributes of the nuchal crest, mastoid process, supraorbital margin, glabella, and the mental eminence were scored on the cranium. If these criteria were not applicable, osteometrics of the humeral head and femoral head were considered for assignment to a sex category according to Dittrick and Suchey (1986). Individuals were labeled as “indeterminate sex” if sex could not be determined due to the skeletal elements required in any of the aforementioned methods were unavailable or missing in analysis.
Postcranial Osteometrics
Bartelink (2006) also collected postcranial osteometric data according to criteria in Buikstra and Ubelaker (1994). The two osteometric measurements considered in this research include femoral bicondylar length and the maximum length of the tibia.
The descriptions of these measurements from Buikstra and Ubelaker (1994) are as follows:
Femoral bicondylar length: “distance form the most superior point on the head of the femur to the most inferior point on the distal condyles” (Buikstra and Ubelaker
1994:82).
56
Length of the tibia: “distance from the superior articular surface of the lateral condyle to the tip of the medial malleolus” (Buikstra and Ubelaker 1994:83).
Visual depictions of these measurements are provided in Appendix A. These osteometrics will be used to estimate stature and lower limb proportionality.
Cranial Porosity
Presence and severity of porotic hyperostosis and cribra orbitalia were also assessed as according to criteria outlined in Buikstra and Ubelaker (1994) (see Table 3 and Table 4). The left and right sides of the frontal, parietal, and occipital bones were
Table 3. Scoring for Presence and Severity of Cranial Pathological Conditions Cribra Orbitalia and Porotic Hyperostosis
Score Porosity 0 Absent 1 External table porosity only, no thickening of cranial vault 2 Porosity, coalescence of foraminae, no thickening of cranial vault 3 Porosity, coalescence of foraminae with coral like hyperostosis 4 Slight porosity, pinpoint (indeterminate, limited to outer table)
Table 4. Scoring for Activity of Cribra Orbitalia and Porotic Hyperostosis
Score Activity 0 Absent 1 Active at time of death 2 Healed at time of death 3 Mixed reaction, some active lesions and signs of healing 4 Eroded lesion margins, uncertain activity at time of death
57 examined for the presence, activity, and severity of porotic hyperostosis. The superior roofs of the eye orbits that were ≥50 percent complete were examined for the presence, activity, and severity of cribra orbitalia. Furthermore, bones with slight porosity (score =
4) were not considered in analyses since this type of porosity has indeterminate causes.
Stature Estimation and Body Proportionality in Prehistoric California Populations
Stature Estimation
For this study, stature estimations will be limited to adults. Three sex-specific equations for indigenous California stature are presented by Auerbach and Ruff (2010), and involve two skeletal measurements. The two measurements are femoral bicondylar breadth (FBL) and tibial maximum length (TML). Based on the availability of measurements available per individual, the stature equations for California indigenous populations used are selected from Table 5.
Table 5. Stature Equations for Males and Females from Auerbach and Ruff (2010)
Sex Measurements (mm) Stature Equation
Male Femoral Bicondylar Length 0.254 * FBL + 52.85 ± 2.55 (FBL) Maximum Length of the 0.302 * TML + 51.66 ± 2.81 Tibia (TML) Maximum Length of the 0.160 * FBL + 0.126 * TML + 47.11 ± 2.35 Tibia (TML) and Femoral Bicondylar Length (FBL) Female Femoral Bicondylar Length 0.267 * FBL + 44.80 ± 2.58 (FBL) Maximum Length of the 0.296 * TML + 52.30 ± 2.90 Tibia (TML) Maximum Length of the 0.176 * FBL + 0.117 * TML + 41.75 ± 2.40 Tibia (TML) and Femoral Bicondylar Length (FBL)
58
Body Proportionality
Comparisons of femoral and tibial lengths will also be considered as proxies for stature using these equations, separately and together as an estimate of total leg length. Individual long bone length differences will also be assessed to examine how proportionality of the femur and tibia affect total leg length. This proportionality between femoral and tibial maximum lengths will be assessed using the tibiofemoral index. The tibiofemoral index is calculated by the following equation:
Tibiofemoral index = (TML)*100/(FBL)
A larger tibiofemoral index implies longer tibial length as compared to femoral length within an individual.
Statistical Methods
Statistical analyses were conducted using IBM SPSS v.20 with all tests evaluated using an alpha level of 0.05. Descriptive statistics and frequencies were computed for the total skeletal sample and also individual sites. Sample demographics were also computed.
Stature
ANOVA was conducted to determine if there was a significant difference in femoral bicondylar length, maximum length of the tibia, and average stature between time periods for each sex (Early, Middle, and Late Periods). It is expected that average values of femoral length, tibial length, and stature will decrease in the Late Holocene as a response to nutritional stress. For comparisons of tibial length, independent samples t- tests were used to compare mean lengths of the Middle and Late Period, since this study
59 lacks tibial length data for the Early Period. Independent samples t-tests were also used to test for sexual dimorphism.
ANOVA was also computed to compare regional differences in femoral length, tibial length, and stature for each time period and sex. It is expected that stature will similarly decrease in both regions over time. If this test demonstrates a significant difference, this may imply that there is differential access to resources between regions.
Body Proportionality
Independent samples t-tests were used for temporal comparisons of total leg length and the tibiofemoral index. For regional comparisons, ANOVA were used to compare total leg length and the tibiofemoral index. It is expected that all measurements and the tibiofemoral index will decrease over time as a response to nutritional stress. This would imply that the tibia is the largest factor associated with stature decline in situations of stress response, as well as total leg length.
Cranial Porosity
Frequencies of porotic hyperostosis and cribra orbitalia were also calculated.
A Pearson’s chi-square test (or Fisher’s Exact test if expected counts are less than five) was used to compare the prevalence of cranial porosity and time period, since both variables are nominal. This test was repeated to compare the prevalence of cranial porosity with each region. All tests were repeated in evaluations of varying levels of severity for cribra orbitalia and porotic hyperostosis. If results of chi-square tests suggest an association, Phi was used to determine the strength of this relationship. It is expected that cranial porosity will increase from the Early to Late Period as a response to nutritional stress. It is also expected that Bayshore populations will show a higher
60 prevalence of cranial porosity when compared to other regions due to the increased potential for coastal populations to experience parasitism.
A final analysis of cranial porosity used independent samples t-tests to compare stature of individuals (within sexes) that have cranial porosity to those that have no evidence of cranial porosity. This test was repeated for stature comparisons of individuals who have higher severity in cranial porosity versus those of lower severity or absence of porosity.
Summary
Adult skeletal samples from 21 central California sites will be used to provide insight to the relationship between subsistence change and skeletal health. Calculations of stature, body proportionality, and prevalence of cranial porosity will be examined from the Early to Late Period, as well as by their region.
CHAPTER VI
RESULTS
The results of statistical analyses conducted to identify trends in stature, body proportionality, cranial porosity, and sexual dimorphism are presented in this chapter.
The demography of the skeletal sample will be discussed first, followed by temporal and regional trends in skeletal health. Each temporal analysis is considered by region and sex, as well as with pooled regions to represent Early, Middle, and Late Period samples for all central California sites. This chapter will also identify patterns in sexual dimorphism of femoral bicondylar length, tibia length, and estimated stature. The results of variation in stature will also be compared to determine if individuals with varying levels of severity of cribra orbitalia and porotic hyperostosis are taller or shorter than those with lower severity levels, or the absence of porosity.
Sample Demography
The sample consists of 669 skeletal individuals, of which there are more females (n = 343) than males (n = 295). A smaller proportion of the sample is of indeterminate sex (n = 31). The Early Period has the smallest sample size (n = 148), but also lacks an Interior Bay sample that is present in other time periods. The Middle Period has the largest sample size (n = 308), followed by the Late Period (n = 213). Table 6 provides a breakdown of the sample demographics by sex, age, region, and time.
61 62
Table 6. Sample Demographics
Age Early Period Middle Period Late Period Males Females Indeterminate Males Females Indeterminate Males Females Indeterminate N % N % N % N % N % N % N % N % N % Bayshore 20-29 5 12.5 9 22.5 - - 23 18.7 16 13.0 2 1.6 6 8.0 14 18.7 - - 30-39 3 7.5 4 10.0 - - 12 9.8 10 8.1 1 0.8 6 8.0 1 1.3 - - 40+ 5 12.5 9 22.5 - - 10 8.1 20 16.3 1 0.8 12 16.0 9 12.0 - - 20+ 1 2.5 3 7.5 - - 10 8.1 8 6.5 4 3.3 8 10.7 11 14.7 5 6.7 30+ 1 2.5 - - - - 1 0.8 4 3.3 1 0.8 3 4.0 - - - - Total 15 37.5 25 62.5 - - 56 45.5 58 47.2 9 7.3 35 46.7 35 46.7 5 6.7 Interior Bay 20-29 ------7 8.6 7 8.6 - - 2 2.9 2 2.9 - - 30-39 ------4 4.9 6 7.4 - - 5 7.1 4 5.7 - - 40+ ------1 1.2 6 7.4 - - 4 2.9 11 15.7 - - 20+ ------20 24.7 15 18.5 - - 2 20 18 25.7 2 2.9 30+ ------6 7.4 9 11.1 - - 14 5.7 6 8.6 - - Total ------38 46.9 43 53.1 - - 27 38.6 41 58.6 2 2.9 Central Valley 20-29 21 19.4 10 9.3 - - 19 18.3 13 12.5 1 1.0 9 13.2 10 14.7 - - 30-39 10 9.3 11 10.2 3 2.8 11 10.6 9 8.7 - - 5 7.4 5 7.4 - - 40+ 14 13 19 17.6 1 0.9 7 6.7 21 20.2 1 1.0 5 7.4 19 27.9 - - 20+ 4 3.7 6 5.6 1 0.9 10 9.6 5 4.8 3 2.9 2 2.9 8 11.8 2 2.9 30+ 3 2.8 3 2.8 2 1.9 2 1.9 1 1.0 1 1.0 2 2.9 1 1.5 - - Total 52 48.1 49 45.4 7 6.5 49 47.1 49 47.1 6 5.8 23 33.8 43 63.2 2 2.9 All Regions Combined 20-29 26 17.6 19 12.8 - - 49 15.9 36 11.7 3 1.0 17 8.0 26 12.2 - - 30-39 13 8.8 15 10.1 3 9.7 27 8.8 25 8.1 1 0.3 16 7.5 10 4.7 - - 40+ 19 12.8 28 18.9 1 0.7 18 5.8 47 15.3 2 0.6 19 8.9 39 18.3 - - 20+ 5 3.4 9 6.1 1 0.7 40 13.0 28 9.1 7 2.3 24 11.3 37 17.4 9 4.2 30+ 4 2.7 3 2.0 2 1.4 9 2.9 14 4.5 2 0.6 9 4.2 7 3.3 - - Total 67 45.3 74 50.0 7 4.7 143 46.4 150 48.7 15 4.9 85 39.9 119 55.9 9 4.2
63
A prevailing trend across all subsamples is that females consistently outnumber males. The only subsample that has more males than females is the Early
Period Valley samples, with males outnumbering females 1.1:1. For the most part, male- to-female ratios are similar to the overall sample sex ratio (1:1.2). The Middle Period
Valley and Late Period Bayshore subsamples show a 1 to 1 male-to-female sex ratio.
However, Late Period samples in the Interior Bay and Valley regions have higher male- to-female ratios (1:1.5 and 1:1.9 respectively) than seen in other time periods or regions, raising the sex ratio of males to females to 1 to 1.4 when all regions are combined for the
Late Period. Females in the Middle Period sample with all regions combined outnumber males 1.1 to 1. Females also outnumber males in the combined region Early Period sample 1.1 to 1. Overall, the Early and Middle Period samples show ratios of near sex equality, and the Late Period has a female bias.
Temporal Trends
Stature
Stature was assessed in this study using three measurements: femoral bicondylar length (mm), tibial length (mm), and estimated stature (cm) using equations developed for prehistoric California populations. When all three geographic regions are pooled, males had a mean femoral bicondylar length of 453.4 mm (SD = 18.3 mm, n =
51) in the Early Period, 447.7 mm (SD = 16.8 mm, n = 88) in the Middle Period, and
448.7 mm (SD = 19.7 mm, n = 38) in the Late Period. The total female sample had a mean femoral bicondylar length of 425.9 mm (SD = 14.2 mm, n = 33) in the Early
Period, 412.6 mm (SD = 17.1 mm, n = 81) in the Middle Period, and 417.5 mm (SD =
64
16.7 mm, n = 51) in the Late Period. Geographic regions vary in mean femoral bicondylar length from the pooled means, and there is an absence of measurement data from the Early Period Interior Bay sample. Mean values, standard deviations, and sample sizes for femoral bicondylar length can be found in Table B1 in Appendix B organized by geographic region and sex.
Tibial length data were only available for the Middle and Late Period samples.
When all regions are considered together, Middle Period male tibiae averaged 378.9 mm
(SD = 15.7 mm, n = 44) and Late Period male tibiae averaged 377.4 mm (SD = 21.7, n =
23) in length. The total sample of females had a mean tibial length of 346.5 mm (SD =
21.9 mm, n = 30) in the Middle Period, and a mean tibial length of 348.0 mm (SD = 14.9 mm, n = 32) in the Late Period. Descriptive data for individual regions presenting mean tibial length values, standard deviations, and sample sizes can be found in Table B5 in
Appendix B.
Mean stature estimates for each sex and region are found in Table B9 in
Appendix B. With all regions combined, males had a mean stature of 168.0 cm (SD = 4.6 cm, n = 51) in the Early Period, 166.0 cm (SD = 4.5 cm, n = 93) in the Middle Period, and 166.6 cm (SD = 5.5, n = 45) in the Late Period. Female stature averaged 158.5 cm
(SD = 3.8 cm, n = 33) in the Early Period, 154.8 cm (SD = 4.9, n = 89) in the Middle
Period, and 156.2 (SD = 4.6, n = 59) in the Late Period.
Analysis of variance (ANOVA) and independent samples t-tests were conducted to evaluate temporal differences in stature for each of these measurements for each sex and region. Tables displaying statistical results for temporal comparisons of femoral bicondylar length, tibial length, and mean stature can be found in Tables B2, B6,
65 and B10 in Appendix B, respectively. However, Bayshore population sample sizes were too small for statistical comparison. Figure 2 is a graphic illustration of ANOVA results
Figure 2. Temporal trends in mean femoral bicondylar length by region and sex.
of temporal trends in mean femoral bicondylar length by region, as well as with all regions combined. This analysis identified a significant decline in female femoral length from the pooled region sample from the Early to Middle Period (p < 0.001, Bonferroni test; mean difference of 13.4 mm). Significant results were also found in Central Valley
66 females, with a 16.8 mm reduction in femoral length from the Early to Middle Period (p
< 0.001, Bonferroni test;) and a rebound in femoral length from the Middle to Late
Period (p = 0.002, Bonferroni test; increase of 15.1 mm). Females in other regions, as well as all males showed no significant temporal changes in femoral length (p > 0.05).
However, a general trend of a reduction in femoral length from the Early to Middle
Period is evident.
A visual representation of temporal trends in tibial length is displayed in
Figure 3. Bayshore and Valley sample sizes were too small for statistical comparison. No significant differences in tibial length were found from the Middle to Late Period for either sex, or within any region (p > 0.05).
Figure 4 illustrates temporal trends in mean estimated stature. This analysis identified a significant reduction in female stature from the combined regions sample from the Early to Middle Period (p < 0.001, Bonferroni test; mean difference of 3.7 cm).
Valley females also experienced a decline in stature from the Early to Middle Period (p <
0.001, Bonferroni test; mean difference of 4.8 cm) and an average increase of 3.9 cm from the Middle to Late Period (p = 0.003, Bonferroni test). Females from the other regions showed no significant changes in stature (p > 0.05). The entirety of the male sample also showed no significant temporal change in stature (p > 0.05).
Lower Limb Proportionality
Lower limb proportionality was estimated using three measurements: total leg length (the sum of femoral bicondylar length and tibial length within an individual) and the tibiofemoral index. Tibial length data were not available for the entirety of the Early
Period sample, limiting the analysis of proportionality to the Middle and Late Periods.
67
Figure 3 Temporal trends in tibia length by region and sex.
With all regions combined, total leg length in males averaged 827.6 mm (SD = 25.7 mm, n = 39) in the Middle Period, and 823.9 mm (SD = 40.8 mm, n = 16) in the Late Period.
Females had a mean total leg length of 764.7 mm (SD = 43.7 mm, n = 22) and 761.9 mm
(SD = 24.2 mm, n = 24) in the Middle and Late Periods, respectively. Descriptive data for total leg length can be found in Table B13 in Appendix B. Figure 5 illustrates temporal trends in mean total leg lengths for each region, as well as with all regions
68
Figure 4. Temporal trends in mean estimated stature by region and sex.
combined. No significant differences were found between the Middle and Late Period for either sex (p > 0.05) (see Table B14 in Appendix B).
With all regions combined, males had a mean tibiofemoral index of 84.5 (SD
= 2, n = 39) in the Middle Period and 84.6 (SD = 2.4, n = 16) in the Late Period.
Females from the pooled region sample averaged an index value of 83.4 (SD = 1.7, n =
22) in the Middle Period and 84.1 (SD = 2.2, n = 24) in the Late Period. Mean values for each individual region and sex are located in Table B16 in Appendix B, and results of
69
Figure 5. Temporal trends in mean total leg length by region and sex.
temporal comparisons are found in Table B18. Most comparisons within regions were too small to test for statistical significance. There were no statistically significant differences in tibia-to-femur length proportionality from the Middle to Late Period for any sex or region (p > 0.05) (see Figure 6).
70
Figure 6. Temporal patterns in mean tibiofemoral index values by region and sex.
Cranial Porosity
Cribra Orbitalia. A total of 522 individuals were assessed for the presence or absence of cribra orbitalia (see Tables B19 and B20 in Appendix B). When all regions and time periods are considered together as a single sample, 214 male crania were assessed. Of these, 47/214 (22.0%) of these males have cribra orbitalia in any state, and
25/214 (11.7%) males have moderate-to-severe states of cribra orbitalia. A total of 283
71 females were assessed for cribra orbitalia, and show a higher proportion of the pathological condition than males, and may be an artifact of the slight female bias in the total study sample. Within females, 72/283 (25.4%) are affected, of which 23/283 (8.1%) were moderate-to-severe cases. Twenty-five cases of cribra orbitalia were found in individuals of indeterminate sex. Of these, approximately 0.4 percent (8/214) of those with indeterminate sex had cribra orbitalia, with only half of these as moderate-to-severe cases (4/214, 0.02%). Tables B21 and B22 in Appendix B present the statistical data for temporal comparisons of cribra orbitalia.
Figure 7 illustrates the temporal distribution of cribra orbitalia. When considering all sexes together, the prevalence of cribra orbitalia in the Early, Middle, and
Figure 7. Temporal distribution of cribra orbitalia considering all regions combined.
72
Late Periods is 31.5 percent (34/108), 22.9 percent (54/236), and 21.9 percent (39/178), respectively. When sexes are considered individually, cribra orbitalia is present in the
Early, Middle, and Late Period samples in 29.8, 21.4, and 17.2 percent of male crania and
32.7, 23.1, and 24.2 percent of female crania respectively. Moderate and severe conditions of cribra orbitalia are present in the Early, Middle, and Late Period samples in
8.5, 11.7, 14.1 percent of male crania and 9.0, 6.6, and 9.3 percent of female crania. The prevalence of cribra orbitalia showed no significant temporal patterns in chi-square analyses (p > 0.05).
Figure 8 displays the temporal distribution of cribra orbitalia in the Bayshore region. Within the Bayshore region, pooled sex Early Period populations have the highest
Figure 8. Temporal distribution of cribra orbitalia in the Bayshore region.
73 proportion of individuals with cribra orbitalia in all states cases (43.5% all states, 21.7% moderate to severe), followed by the Middle Period (37.4% all states, 19.8% of population with moderate to severe cases), with the Late Period having the fewest (30.6% all states, 21.0% moderate to severe). However, the sample sizes of individuals in the
Bayshore regions assessed for cribra orbitalia are small for the Middle and Late Periods.
When partitioned by sex, the proportion of crania with the prevalence of cribra orbitalia is highest in the Early (50.0 percent), followed by the Middle Period (28.6%), and Late
Period (26.7%) in males, and the highest in the Middle (42.9%), followed by the Early
Period (40.0%) and Late Period (32.1%) in females. Moderate-to-severe cribra orbitalia is present in 25.0, 19.0, and 23.3 percent of male crania and 20.0, 16.7, and 17.9 percent of female crania in the Early, Middle, and Late Period Bayshore samples, respectively.
The temporal distribution of cribra orbitalia in the Interior Bay is illustrated in
Figure 9. With pooled sexes, the Interior Bay reports considerably fewer cases of cribra orbitalia in comparison to the other regions. Only one individual is reported to have cribra orbitalia in the Middle Period, of which it is low severity, representing 1.5 percent of the sample. The Late Period shows only four cases (6.5% of Late Period Interior Bay population), of which one is of higher severity within the Interior Bay (1.6%). When divided by sex, the Late Period had the highest prevalence of cribra orbitalia for both sexes (0.0% and 4.8%, and 2.6% and 7.7% for Middle and Late Period males and females respectively). The only Late Period male in the sample with cribra orbitalia was a higher severity case. No significant results were reported for temporal comparisons within this region (p > 0.05).
74
Figure 9. Temporal distribution of cribra orbitalia in the interior bay region.
Figure 10 displays the temporal distribution of cribra orbitalia in the Central
Valley region. With all sexes combined, Valley populations have the highest prevalence of cribra orbitalia in the Late Period (29.1%), followed by the Early (28.2%) and Middle
(23.2%) Periods. No temporal patterns are found for prevalence of cribra orbitalia in all states, or even in consideration of moderate and severe cases (p > 0.05). When partitioned by sex, Valley males had the highest proportion of cribra orbitalia in the
Middle Period (27.0%), followed by the Early (25.6%) and Late Period (15.4%). Valley females had the highest proportion of cribra orbitalia in the Late Period, (35.0%), followed by the Early (30.0%) and Middle (22.5%) Periods. Within the Valley population, higher severity of cribra orbitalia was reported for 5.1, 10.8, and 7.7 percent
75
Figure 10. Temporal distribution of cribra orbitalia in the central valley region.
of males and 5.0, 2.5, and 12.5 percent of females in the Early, Middle, and Late Periods, respectively. No significant results were reported for temporal comparisons within this region (p > 0.05).
Porotic Hyperostosis. A total of 582 crania were assessed for the presence and absence of porotic hyperostosis (see Tables B30 and 31 in Appendix B). From the entire sample, 249 male crania were examined. Of these, 151/249 (60%) had porotic hyperostosis, and 74/249 (29.7%) were moderate-to-severe cases. A total of 308 female crania were examined, of which 161/308 (52.3%) had porotic hyperostosis and 47/308
(15.3%) were moderate-to-severe cases. In the sample of individuals of indeterminate sex, 18/26 (69.2%) had porotic hyperostosis, and 7/26 (26.9%) of these cases were of
76 higher severity. When considering all sexes together, the prevalence of porotic hyperostosis in the Early, Middle, and Late Periods is 76.7 percent (102/133), 50.8 percent (136/260), and 48.7 percent (92/189), respectively (see Figure 11). Results indicate that as a whole, the Early Period has a significantly higher proportion of porotic hyperostosis than in the Middle Period (p < 0.001) and Late Period (p < 0.001), but no trends were identified for cases of moderate-to-severe cranial vault porosity (p > 0.05).
Tables B32 and B33 in Appendix B present the statistical data for temporal comparisons of porotic hyperostosis.
Figure 11. Temporal distribution of porotic hyperostosis considering all regions combined.
77
When sexes are considered individually, porotic hyperostosis is present in
78.7, 58.1, and 49.3 percent of male crania and in 75.8, 44.6, and 47.7 percent of female crania respectively for the Early, Middle, and Late Period samples. Chi-square results show that the male Early Period sample with all regions pooled have a higher proportion of porotic hyperostosis than the Middle and Late Period samples (χ2 = 7.473, p = 0.006;
χ2 = 12.144, p < 0.001, respectively). Results also indicate that the Early Period female sample has a significantly higher prevalence of porotic hyperostosis than in the Middle and Late Period female samples (χ2 = 17.161, p < 0.001; χ2 = 13.341, p < 0.001 respectively). Moderate to severe cases of porotic hyperostosis are present in the Early,
Middle, and Late Periods in 30.5, 30.8, and 28.2 percent of male cranial vaults and 18.2,
14.6, and 14.3 percent of female cranial vaults. No significant temporal trends were identified for cases of moderate-to-severe porotic hyperostosis in this region (p > 0.05).
Figure 12 illustrates the temporal variation of porotic hyperostosis in the
Bayshore region. With sexes pooled, the Early Period has a high prevalence of porotic hyperostosis within the Bayshore region (89.5% with the condition, 42.1% of the population with higher severity). The Middle Period Bayshore population has a 67.0 percent prevalence of porotic hyperostosis, as well as 41.5 percent with moderate or severe cases. Within the Late Period Bayshore, the prevalence of porotic hyperostosis is
68.1 percent, and 42.9 percent of the population has moderate-to-severe cranial vault porosity. No significant results were found for these temporal comparisons (p > 0.05).
When partitioned by sex, the proportion of cranial vaults with porotic hyperostosis is highest in the Early Period (100.0%), followed by the Middle Period (77.6%) and Late
Periods (75.8%) in males, and highest in the Early Period (82.6%), followed by the Late
78
Figure 12. Temporal distribution of porotic hyperostosis in the Bayshore region.
(68.8%) and Middle Periods (67.3%) in females. Results indicate that the Early Period male Bayshore sample had a higher prevalence of porotic hyperostosis than the Middle
Period (F.E., p = 0.05) and also the Late Period (F.E., p = 0.044).
Higher severity porotic hyperostosis was found in 60.0, 55.1, and 51.5 percent of male crania in the Early, Middle, and Late Periods respectively, and also in 30.4, 24.5, and 33.3 percent of female crania in the Early, Middle, and Late Periods respectively. No trends were identified in temporal analysis of higher severity porotic hyperostosis (p >
0.05).
Temporal variation of porotic hyperostosis within the Interior Bay is presented in Figure 13. The Interior Bay lacks a comparative Early Period sample. With sexes
79
Figure 13. Temporal distribution of porotic hyperostosis in the interior bay region.
pooled, 14.3 percent of individuals assessed from the Middle Period and 16.9 percent of individuals from the Late Period have porotic hyperostosis. Moderate to severe cases of porotic hyperostosis are present in 2.9 percent of the Middle Period population, and 3.1 percent of the Late Period sample. Interior Bay Middle and Late Period samples show very similar prevalence for all states of porotic hyperostosis, as well as cases of moderate to severe vault porosity. When sexes are observed individually, porotic hyperostosis is present in 20.0 and 20.8 percent of male crania and 10.0 and 15.0 percent in female crania in the Middle and Late Period, respectively. Higher severity cases of porotic hyperostosis are present in 3.3 and 4.2 percent of male crania in the Middle and Late
Periods respectively, and the prevalence of moderate-to-severe cases in female crania is a
80 consistent 2.5 percent in both the Middle and Late Periods. No significant results were reported for temporal comparisons within this region at any level of severity (p > 0.05).
The temporal variation of porotic hyperostosis within the Central Valley is illustrated in Figure 14. Of the pooled sex Valley populations, porotic hyperostosis is present in 71.6 percent of the Early Period sample, 56.0 percent in the Middle Period
Figure 14. Temporal distribution of porotic hyperostosis in the central valley region.
sample, and 54.5 percent of the Late Period sample. Results indicate a significantly higher proportion of porotic hyperostosis in the Early Period than in the Middle and Late
Periods (χ2 =4.739, p = 0.029; χ2 =4.462, p = 0.035 respectively). Higher severity porotic hyperostosis is present in 15.1 percent in the Early Period sample, and 16.7 and 10.9
81 percent of the Middle and Late Period samples, respectively. No significant differences were identified in temporal comparisons of higher severity cranial vault porosity (p >
0.05).
When partitioned by sex, the prevalence of porotic hyperostosis in the Early,
Middle, and Late Period is 71.7, 63.2, and 35.7 percent respectively in male crania, and
72.1, 51.2, and 64.1 percent respectively in female crania. Significantly higher proportions of cranial vault porosity were found in the Early Period Valley male sample than in the Late Period Valley male sample (χ2 = 5.998, p = 0.014), as well as a higher proportion of cranial vault porosity in Early Period Valley females than Middle Period
Valley females (χ2 = 3.878, p = 0.049). Moderate-to-severe porotic hyperostosis is present in 20.5, 21.1, and 14.3 percent of male crania in the Early, Middle, and Late
Period Valley samples respectively. In females, moderate-to-severe porotic hyperostosis is present in 11.6, 14.6, and 10.3 percent of the Early, Middle, and Late Period Valley samples respectively. No significant results were found in temporal comparisons of moderate-to-severe cranial vault porosity (p > 0.05).
Regional Trends
Stature
Figure 15 shows regional patterns in femoral bicondylar length (see Table B3 in Appendix B for statistical data). The Bayshore male sample tends to have longer femora than both the Interior Bay and Valley male samples, with Valley males having the shortest femora in all time periods. However, this pattern was not significant (p > 0.05).
Females show different trends in regional comparisons of mean femoral length. In all
82
Figure 15. Regional distribution of mean femoral bicondylar length.
temporal comparisons, Bayshore female samples tend to have the shortest femora. In the
Middle Period, Interior Bay females have the largest average femoral length, and the
Bayshore and Central Valley females are very similar in length (1.2 mm mean difference). Central Valley females have the longest femora in the Late Period, and
Bayshore and Interior Bay females have very similar average femoral lengths (0.7 mm mean difference). Significant differences are only identified in Late Period females,
83 where Central Valley females have longer femora than both the Bayshore and Interior
Bay female samples by 15.3 mm (p = 0.031), 14.6 mm (p = 0.015) respectively.
Tibial lengths show no significant differences in regional comparisons (see
Figure 16 for graphic illustration, and Table B7 in Appendix B for ANOVA results).
Small sample sizes hindered results of this analysis. However, results for Middle Period males were conducted, and a general trend was identified. Bayshore males had the longest average femora than both Interior Bay (4.8 mm mean difference) and Valley males (3.9 mm mean difference), although this was not a statistically significant difference (p = 0.684).
Figure 16. Regional distribution of mean tibial lengths.
Although data for the Early Period component for the Interior Bay was absent, the regional analysis of estimated stature showed general trends for males and females
(see Figure 17 for graphic illustration, and Table B11 in Appendix B for ANOVA results).
84
Figure 17. Regional variation in mean estimated stature.
Bayshore males tended to be the tallest in all time periods, and Interior Bay males as the shortest. For females, the Valley sample was the tallest in the Early and Late
Periods, with Interior Bay females as the tallest in the Middle Period. However, these patterns are not statistically significant, although differences between Late Period Valley females and samples from the Interior Bay (mean difference of 3.2 mm) and Bayshore
(mean difference of 3.7 cm) approach significance (p = 0.063 for both).
85
Lower Limb Proportionality
Illustrations of regional patterns in total leg length are in Figure 18 (see Table
B15 in Appendix B for statistical data). The Middle Period male sample, although still small, was the only sample large enough for statistical assessment. However, no significant results were found (p > 0.05), but Bayshore samples tended to have longer total leg length when compared to the Interior Bay and Valley samples.
Figure 18. Regional variation in mean total leg length.
Figure 19 illustrates regional variation in tibiofemoral index values (see Table
B18 in Appendix B for statistical output). ANOVA was conducted for only Middle
Period males due to sample size, but no significant differences were found between regions (p > 0.05). For both sexes, Interior Bay populations tended to have the largest index values in the Middle Period, followed by the Bayshore and Valley samples. In the
Late Period, the Bayshore samples tended to have the largest tibiofemoral index for both sexes.
86
Figure 19. Regional variation in mean tibiofemoral index values.
Cranial Porosity
Cribra Orbitalia. Regional comparisons of cribra orbitalia in the Early Period are illustrated in Figure 20 (see Table B23 in Appendix B). Chi-square results indicate no regional trends were found for Early Period comparisons for either sex when considering all levels of cribra orbitalia severity (p > 0.05), implying that the percentage of affected individuals within each region is not statistically different from one another. When sexes are combined into a single Early Period sample, the Bayshore has a higher proportion of moderate-to-severe cribra orbitalia than the Valley sample (21.7% vs. 4.7%, F.E., p =
0.02).
Regional variation in cribra orbitalia during the Middle Period is presented in
Figure 21. In the Middle Period, males showed a statistically significant higher prevalence of cribra orbitalia in the Bayshore region than in the Interior Bay (28.6% vs.
0.0%, F.E., p = 0.003). Middle Period males also had a higher prevalence in the Valley versus the Interior Bay (27.0% vs. 0.0% percent, F.E., p = 0.004). Higher severity cribra
87
Figure 20. Regional variation of cribra orbitalia during the early period.
orbitalia was only more prevalent in the Bayshore than Interior Bay male samples (19.0% vs. 0.0%, F.E., p = 0.043). Middle Period females showed statistical significance in all regional comparisons. Middle Period Bayshore female populations had a higher prevalence of cribra orbitalia than the Interior Bay (42.9% vs. 2.6%, F.E., p < 0.001) and
Valley females (42.9% vs. 22.5%, χ2 = 3.844, p = 0.050), and the Valley females had a higher prevalence than the Interior Bay females (22.5% vs. 2.6%, F.E., p = 0.014). Like the Middle Period males, moderate-to-severe cribra orbitalia was only significantly higher in the Bayshore female sample than the Interior Bay female sample (16.7% vs.
0.0%, F.E., p = 0.012). With sexes combined, the Middle Period Bayshore populations had the highest prevalence of cribra orbitalia when compared to the Valley (37.4% vs.
88
Figure 21. Regional variation of cribra orbitalia during the middle period.
23.2%, χ2 =4.088, p = 0.043), and the Valley had a higher prevalence than the Interior
Bay (23.2% vs. 1.6%, F.E., p < 0.001). Moderate-to-severe cases of cribra orbitalia were higher in the Bayshore pooled sex sample than the Interior Bay and Valley samples
(19.8% vs. 0.0% and 6.1% respectively, F.E., p < 0.001 for both comparisons).
In the Late Period, chi-square and Fisher’s Exact test results showed no significant regional trends for prevalence of cribra orbitalia of any level of severity in males (p > 0.05) (see Figure 22). Females showed a significantly higher prevalence of cribra orbitalia in the Bayshore than in the Interior Bay region (26.7% vs. 4.8%, F.E., p =
0.021), and this trend is the same for cases of higher severity orbital roof porosity (23.3% vs. 4.8%, F.E., p = 0.01). Valley females also showed a higher prevalence of orbital roof
89
Figure 22. Regional variation of cribra orbitalia in the late period.
porosity than Interior Bay females (15.4% vs. 4.8%, F.E., p = 0.001). When sexes were pooled into a single sample, Bayshore populations showed a higher prevalence of orbital roof porosity in all states, as well as higher severity cases, than the Interior Bay (30.6% vs. 6.6% and 21.0% vs. 1.6%, F.E., p = 0.001 for both tests). The pooled sex Valley samples also show a higher proportion of affected individuals in both categories than
Interior Bay samples (29.1% vs. 6.6%, F.E., p = 0.002 all states of porosity; 10.9% vs.
1.6%, F.E., p = 0.05 for higher severity cases).
Porotic Hyperostosis. The majority of regional comparisons of porotic hyperostosis show significant results (see Table B34 in Appendix B). Regional comparisons of porotic hyperostosis in the Early Period are illustrated in Figure 23. In
90
Figure 23. Regional variation of porotic hyperostosis in the early period.
comparisons of porotic hyperostosis in the Early Period, the Bayshore male sample has a higher prevalence than in Valley males (100.0% vs. 71.7%, F.E., p = 0.026). When sexes are combined into a single Early Period sample, this trend is repeated (89.5% vs. 71.6%,
F.E., p = 0.039). This trend is again repeated in comparisons of higher severity porotic hyperostosis in males (60.0% vs. 20.5%, χ2 = 8.683, p = 0.013). The combined sex Early
Period sample show the Bayshore region has a higher proportion of moderate-to-severe porotic hyperostosis than the Valley sample (42.1% vs. 15.1%, χ2 = 11.181, p = 0.001).
Regional variation of porotic hyperostosis in the Middle Period is illustrated in Figure 24. In the Middle Period, Interior Bay males show a lower prevalence of porotic hyperostosis than Bayshore males (20.0% vs. 77.6%, χ2 =25.975, p < 0.001) and Valley
91
Figure 24. Regional variation of porotic hyperostosis in the middle period.
males (20.0% vs. 63.2%, χ2 =12.666, p < 0.001). This trend is repeated in regional comparisons of females (10.0% vs. 67.3% and 51.2% respectively, F.E., p < 0.001 in both comparisons). When sexes are combined into a single Middle Period sample,
Bayshore populations show a significantly higher prevalence than both the Interior Bay
(89.5% vs. 14.3%, χ2 =61.210, p < 0.001) and Valley populations (89.5% vs. 56.0%, χ2
=7.239, p = 0.007), and the Valley shows a larger proportion than in the Interior Bay
(56.0% vs. 14.3%, χ2 =28.433, p < 0.001). Trends of higher severity cranial vault porosity are similar. Middle Period Bayshore males show a higher prevalence of moderate-to-severe porotic hyperostosis than the Interior Bay and Valley regions (55.1% vs. 3.3%, F.E., p < 0.001; 55.1% vs. 21.1%, χ2 =10.319, p < 0.001). For females, results
92 indicate significant differences only between the high prevalence of moderate-to-severe porotic hyperostosis in the Bayshore region versus the Interior Bay (24.4% vs. 2.5%,
F.E., p = 0.005). With sexes combined, the Interior Bay had the lowest prevalence of moderate-to-severe porotic hyperostosis compared to the Valley (2.9% vs. 16.7%, F.E., p
= 0.07) and Bayshore populations (2.9% vs. 41.5%, F.E., p < 0.001), and the Valley had a lower prevalence than the Bayshore samples (16.7% vs. 41.5%, χ2 =13.64, p < 0.001).
Figure 25 shows regional variation of porotic hyperostosis in the Late Period.
In the Late Period, Bayshore populations showed a significantly higher prevalence of
Figure 25. Regional variation of porotic hyperostosis in the late period.
93 porotic hyperostosis when compared to the Interior Bay (75.8% vs. 20.8%, χ2 =16.813, p
< 0.001 for males; 68.8% vs. 10.0%, χ2 =21.612, p < 0.001 for females; 68.1% vs.
16.9%, χ2 =43.726, p < 0.001 for combined sexes) and Valley populations (75.8% vs.
35.7%, χ2 =6.827, p = 0.009 for males; 68.1% vs. 54.5%, χ2 =6.068, p = 0.024 for combined sexes). The Interior Bay had a significantly lower prevalence of porotic hyperostosis than Valley populations for the female and combined sex samples (15.0% vs. 64.1%, χ2 =19.969, p < 0.001; 16.9% vs. 54.5%, χ2 =18.747, p < 0.001 respectively).
When considering higher severity porotic hyperostosis, Bayshore populations had a significantly higher proportion when compared to Interior Bay (51.5% vs. 4.2%, and
42.9% vs. 3.1%, F.E., p < 0.001 for both males and combined sex samples; 33.3% vs.
2.5%, F.E., p = 0.001 for females) and Valley samples (51.5% vs. 14.3%, χ2 =5.657, p =
0.017 for males; 33.3% vs. 10.3%, F.E., p = 0.021 for females; and 42.9% vs. 10.9%, χ2
=15.331, p < 0.001 for combined sexes).
Sexual Dimorphism in Stature
As seen in Figures 26, 27, and 28 (and Tables B4, B8, and B12 in Appendix
B) respectively, males and females show marked sexual dimorphism in femoral bicondylar length, tibial length, and mean estimated stature. Independent samples t-test results indicate significantly longer femoral bicondylar length in males (p < 0.001 in all comparisons except for Late Period Valley samples, p = 0.015, see Figure 27). In the
Early Period, the difference between male and female femoral lengths was 27.4 mm with all regions combined, and 35.8 mm and 24.5 mm for the Bayshore and Valley regions, respectively. However, Early Period Bayshore sample sizes for males and females were
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Figure 26. Sexual dimorphism in femoral bicondylar length.
Figure 27. Sexual dimorphism in tibia length.
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Figure 28. Sexual dimorphism in estimated stature.
too small for statistical comparison. In the Middle Period, the difference between sexes was 35.1 mm for the pooled regions, and 42.3 mm, 29.6 mm, and 32.5 mm in the
Bayshore, Interior Bay, and Valley regions, respectively. In the Late Period, males and females differed in femoral length by 31.2 mm in combined regions, and 40.0 mm, 36.5 mm, and 18.0 mm in Bayshore, Interior Bay, and Valley populations, respectively. In the
Bayshore, Interior Bay, and combined regions samples, sexually dimorphic differences peaked in the Middle Period. In the Interior Bay, the Middle Period had a smaller dimorphic difference in femoral length than in the Late Period.
Statistical comparisons of sexual dimorphism in tibia length could only be conducted for some of the time periods within regions due to sample size. Independent samples t-test results showed that males and females significantly differed in tibial length when these comparisons could be made, with longer tibiae in males (p < 0.001) (see
Figure 27). Although sample sizes were small, Bayshore populations had an average difference of 28.6 mm in tibia length in the Middle Period and 37.4 mm in the Late
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Period. Interior Bay samples differed in tibia length by 32.4 mm and 26.1 mm in the
Middle and Late Period, respectively (p < 0.001). Middle Period Valley samples differed by 36.7 mm between sexes (p < 0.001). In the Late Period Valley, male tibiae were an average of 38.8 mm longer, although the sample sizes were small in this comparison.
When all regions were combined, male tibiae were an average of 32.4 mm and 29.4 mm longer than female tibiae in the Middle and Late Period (p < 0.001). For the Bayshore and Valley populations, sexual dimorphism in tibia length peaked in the Late Period, while sexual dimorphism peaked in the Middle Period for Interior Bay and combined regions samples.
Using stature estimates from formulae by Auerbach and Ruff (2010), statistically significant differences were found between males and females when sample sizes permitted comparisons (p < 0.001). These dimorphic differences in stature are illustrated in Figure 28. In the Bayshore, males were on average taller than females in the
Early Period by 11.7 cm, and by 12.8 cm and 12.9 cm in the Middle and Late Period, respectively. However, sample sizes of Bayshore populations in the Early Period were too small for statistical assessment. Interior Bay males were on average taller than females by 10.2 cm in the Middle Period and 10.4 cm in the Late Period. In the Valley samples, males were an average of 8.7 cm taller than females in the Early Period, and
11.2 cm and 8.2 cm taller in the Middle and Late Period, respectively. When all regions were combined, Early, Middle, and Late Period males were on average taller than females by 9.5 cm, 11.5 cm, and 10.4 cm respectively. Sexually dimorphic differences in estimated stature peak in the Middle Period for Valley and combined regions samples. In the Bayshore and Interior Bay samples, sexual dimorphism was slightly greater in the
97
Late Period compared to the Middle Period. The magnitude of these differences are small enough that sexual dimorphism is very similar between the Middle and Late Period in these regions.
Comparison of Stature in Individuals with Cranial Porosity
Cribra Orbitalia
Average stature of males with and without cribra orbitalia are illustrated in
Figures 29 and 30 (see Table B24, and mean male stature with and without higher severity levels of cribra orbitalia are reported Table B25 in Appendix B). These comparisons are also available for females in Figures 31 and 32 (see Table B26 and
Table B27 in Appendix B). When divided into subsamples by region, time period, and sex, sample sizes for many groups become too small for statistical comparison of stature of those with the absence or presence of cribra orbitalia. Because of this, the only statistical comparisons that could be reported are for males and females with all three regions combined considering all states of cribra orbitalia (Table B28 and Table B29 in
Appendix B). No statistically significant temporal difference in stature was found between affected and unaffected individuals for either sex (p > 0.05).
Porotic Hyperostosis
The average stature of males with and without porotic hyperostosis is illustrated in Figures 33 and 34 (see Table B35, and mean male stature with and without higher severity levels of porotic hyperostosis is reported Table B36 in Appendix B).
These comparisons of female stature values are also illustrated in Figures 35 and 36 (see
Table B37 and Table B38 in Appendix B). For comparisons that had sufficient sample
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Figure 29. Comparison of mean stature between males with the presence and absence of cribra orbitalia.
sizes for statistical computation, there was no significant difference between males without porotic hyperostosis, and males that had porotic hyperostosis of any level of severity (Table B39 in Appendix B). In comparison of males with higher severity porotic hyperostosis versus males with lower severity or no porosity, Middle Period males without higher severity porosity were an average of 2.4 cm shorter (165.8 cm vs. 168.2 cm, t-value=2.098, df=66, p = 0.04) (Table B40 in Appendix B). However, the sample sizes for these groups are very different from each other, so this may not be a truly
99
Figure 30. Comparison of mean stature between males with higher severity versus absence/low severity of cribra orbitalia.
representative comparison of stature in these groups (n = 19 for those with moderate-to- severe porotic hyperostosis, n = 49 for those without). No patterns were found between females without porotic hyperostosis and females with any porosity (Table B41 in
Appendix B), and sample sizes of females with porosity of higher severity were inappropriate for statistical comparison.
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Figure 31. Comparison of mean stature between females with the presence or absence of cribra orbitalia.
Summary
Several aspects of stature, cranial porosity, and proxies for body proportionality were analyzed over time and between regions of central California.
Femoral bicondylar lengths, maximum tibial lengths, and stature estimations were used for analyses of stature. Total leg length and the tibiofemoral index were used as proxies for lower body proportionality. The presence and absence of cribra orbitalia and porotic hyperostosis were analyzed as proxies for nutritional stress.
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Figure 32. Comparison of mean stature between females with higher severity versus absence/low severity of cribra orbitalia.
Femoral bicondylar length declined significantly from the Early to Middle
Period for females when all regions were considered. Valley females mimicked this pattern, but also showed a significant increase from the Middle to Late Period. Only Late
Period females showed significant regional differences in femoral length, with longer femora in the Valley than the Interior Bay or Bayshore populations. No significant temporal or regional differences were found in tibial length and most sample sizes were
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Figure 33. Comparison of mean stature between males with presence or absence of porotic hyperostosis.
too small for comparison, but lengths were very similar across time periods and Bayshore populations tended to have the longest tibiae.
Stature proved to be highly sexually dimorphic, with males taller than females, as expected. Females in combined regions were significantly taller in the Early
Period than their Middle Period counterparts. Similar to results in femoral bicondylar
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Figure 34. Comparison of mean stature between males with higher severity versus absence/low severity of porotic hyperostosis.
length analysis, Valley females again mimicked this pattern, but also had a significant increase in average stature from the Middle to Late Period. Late Period females only approached significant regional variation in stature, with Valley populations as the tallest.
Although total leg length had small sample sizes, no significant trends were evident but leg length tended to be longer in the Middle Period. The tibiofemoral index
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Figure 35. Comparison of mean stature between females with presence or absence of porotic hyperostosis.
reported lower values in the Middle Period than in the Late Period, indicating that femoral length increases in leg length comparatively to tibial length within an individual.
No temporal trends were evident for cribra orbitalia in any state. Regionally, however, Bayshore populations display the highest prevalence, and Valley populations with the lowest. No trend could be strongly identified in comparisons of stature of individuals with orbital roof porosity and those without. Porotic hyperostosis of all levels
105 of severity in males with all regions considered together tended to be of higher prevalence in the Early Period, while the opposite trend is found in females. For both sexes, Bayshore populations had the highest prevalence of all levels of severity as well as moderate to severe cranial vault porosity, followed by Valley populations. A single significant trend in comparisons of stature of individuals with cranial vault porosity and those with no porotic hyperostosis was found. Males with moderate-to-severe porotic hyperostosis tended to be taller than individuals with lower severity or no porotic hyperostosis. The next chapter will provide interpretations on these results in the context of this study’s research hypotheses.
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Figure 36. Comparison of mean stature between females with higher severity versus absence/ low severity of porotic hyperostosis.
CHAPTER VII
DISCUSSION AND CONCLUSIONS
This purpose of this study was to test if expected skeletal changes occurred during the Late Holocene in central California skeletal populations. Several proxies for stature and body proportionality were used to evaluate these expectations, as well as an analysis of the prevalence of cranial porosity. This chapter addresses each research hypothesis proposed in Chapter I, and is evaluated in light of the results. Study limitations and suggestions for future research will be discussed. The chapter, as well as the thesis, will end with a summary statement on resource intensification and geography as models for predicting nutritional stress.
Stature
Stature was evaluated in this study using three biological measurements including femoral bicondylar length, maximum tibial length, and estimated stature using equations developed for prehistoric California populations (Auerbach and Ruff 2010).
The analysis of stature in this study tested three hypotheses that predicted outcomes on temporal variation, regional variation, and sexual dimorphism.
Stature Hypothesis 1: Temporal Stature Decline
The first hypothesis in this study was that for both sexes, stature would decrease over time in central California as a response to a change to a lower-quality diet,
107 108 including increased reliance on acorns and lower consumption of meat resources. This hypothesis was only partially supported. With all regions considered together, femoral bicondylar length and estimated stature measurements decreased from the Early to
Middle Period, supporting the hypothesis. This trend is significant in the Valley female and combined region female samples. However, it should be noted that stature was estimated using the same femoral lengths due to the lack of tibial measurements for the
Early Period, so this pattern is expected for both measurements. Middle to Late Period comparisons showed similar and slightly increased mean femoral lengths and stature, which was an unexpected result. Again, this trend is significant in the sample of Valley females, while all samples reported tibial lengths of very similar measurements from the
Middle to the Late Period.
The reduction of stature from the Early to the Middle Period observed in this study is consistent with expectations for responses to nutritional stress resulting from resource depression and a decline in foraging efficiency prior to the development of new subsistence adaptations. Previous research observed a temporal decline in stature in central California during the Late Holocene as a response to nutritional stress (Bartelink
2006; Broughton et al. 2010; Ivanhoe 1995; Ivanhoe and Chu 1996), as well as in southern California (Lambert 1993). Ivanhoe (1995) found a decline in Late Holocene stature in the Central Valley, and this region appears to be affected to a greater degree than the decline of stature found by Ivanhoe and Chu (1996) in the Bay Area. Bartelink
(2006) observed stature in Central Valley and Bay Area populations, and found that femoral length was greater in the Early Period for both regions, and only the Central
Valley females experienced an increase in femoral length in the Late Period. Broughton
109 et al. (2010) also used femoral bicondylar length of Late Holocene skeletons from the
Sacramento Valley and identified a temporal decline in stature for both sexes. These studies of central California attributed reductions in stature to nutritional stress as a result of resource intensification, citing an increased reliance on acorns. In southern California,
Lambert (1993) attributed a decline in femoral length during the Late Holocene to nutritional stress resulting from a shift from maritime hunting and gathering towards an intensified fishing economy.
Stature Hypothesis 2: Regional Variation
The second hypothesis presented expectations that there is regional variation in stature, and results would indicate that Bayshore populations tend to have taller stature in comparison to the Interior Bay and Valley populations. This reasoning is due to the assumption that Bayshore populations have access to a higher diversity of dietary protein given their geographic proximity to marine resources that would have provided sufficient dietary protein for normal growth and development.
This hypothesis of regional variation in stature was partially supported.
Bayshore sample sizes were small for statistical assessment of regional comparisons, but a general trend was observed. Bayshore females tend to be the shortest in regional comparisons of estimated stature and femoral bicondylar length, and Bayshore males tended to be the tallest. However, both sexes in the Bayshore region tended to have longer tibial lengths in regional comparisons. Similar to the results of this study,
Bartelink (2006) also found that in comparisons of femoral length between Central
Valley and Bay Area samples, male samples from the Bay Area tended to have longer
110 femora than in the Valley. This trend reversed for females in the Late Period, where
Valley femora were longer than in the Bay Area.
Other research on stature in prehistoric central California such as works by
Brooks (1975) and Ivanhoe and Chu (1996) identified populations in the San Francisco
Bay region as metrically smaller than Sacramento Valley populations, which suggests a pattern contrary to what was found in this study. Results of this study suggest that dimorphism was usually largest between Bayshore males and females than in the other two regions, even in the Early Period. This suggests that there may be some influence prior to the time frame of this study that results in a general pattern of tall males and short females in the Bayshore region. For example, this may be the result of a larger evolutionary process of sexual selection influencing the sexual dimorphism in stature for this population. Some studies of contemporary populations have indicated that tall men tend to have greater reproductive success than shorter men, suggesting that stature may have been a selective pressure (Mueller and Mazur 2001; Nettle 2002; Pawlowski et al.
2000).
However, the Bayshore region has access to a higher diversity of protein resources such as marine foods such as shellfish, fish, and marine mammals, as well as terrestrial foods that would be beneficial to growth and development. In comparison,
Valley populations would have had a more limited diversity of protein sources. A sexual division of labor is hypothesized to be a factor in diet choice for males and females
(Jochim 1988; Zeanah 2004). In California, ethnohistoric subsistence activities were divided by gender, with women acting as the primary plant food gatherers and processors
(Jackson 1991) and men focusing on hunting and fishing (Willoughby 1963). This
111 division in labor would have introduced greater access of protein-rich foods that promote normal growth in males and greater access to low-protein resources to females (but likely high in fat and carbohydrate macronutrients, in the situation of acorns and small seeds). A depression of low-cost terrestrial animal resources in the Bayshore region would have been buffered by a shift or balance towards marine foods (Broughton 1994a); however, a similar situation may have been more costly for Valley populations that largely had access to only terrestrial resources (Broughton 1994b). This may explain why males in the Bayshore region are taller than the Interior Bay and especially the Valley males, and also why Valley females showed a significant decline in stature.
Stature Hypothesis 3: Sexual Dimorphism
Finally, the third stature hypothesis stated that stature would be sexually dimorphic, and that there would be temporal variation in dimorphism, suggesting that one sex may be affected to a higher degree by nutritional stress than the other. This hypothesis was supported. Significant differences were found between males and females in all comparisons. Sexual dimorphism peaked in the Middle Period for measurements of femoral bicondylar length in all regions except for the Interior Bay. The tibia was more variable in its regional expression of dimorphism, but this analysis was limited due to small sample sizes. Estimated stature also varied in its regional expression of sexual dimorphism, but differences were greatest in the Middle Period for Valley populations and in the combined regions sample.
Maximum dimorphism may also have been the inadvertent result of differential access to resources associated with sexual divisions of labor, as previously discussed. Primary documentation of sexual division of labor in California is from
112 ethnohistoric or ethnographic studies, but some studies have incorporated skeletal evidence into understanding sexual division of labor. A previous study by Mangold
(2006) found that male and female mobility changed over time in the Central Valley of
California by observing changes in femoral morphology. A sexual division of labor is an influential factor in determining mobility patterns and diet (Zeanah 2004). Mangold
(2006) found that male mobility increased over time, as evidenced by an increase in anteroposterior diameter relative to mediolateral diameter of the femur. Females showed the opposite trend, implying a decline in female mobility. These trends between males and females became more divergent over time, suggesting that the sexual division of labor involving mobility increased over time. This increased division of labor and reduction in mobility is likely a response to an increased requirement for labor in sedentary populations, where females tend to be responsible for childcare and plant processing near home base, and male mobility increased as a response to resource intensification (Mangold 2006). For females, the increased labor requirement as a response to increased sexual division of labor, lowered mobility, and greater access to vegetal food resources may provide support for why females appear to be more affected by stature decline in central California.
Sexual division of labor may also be an influence at a young age. For example, young boys and girls may have accompanied their fathers and mothers, respectively during subsistence activities. This activity would then result in differential access to food resources from a young age, where a balance of protein macronutrients is essential for growth, therefore unequally subjecting sexes to nutritional stress.
Furthermore, differential parental investment may also suggest that there may be unequal
113 provisioning of resources in their offspring based on sex. For instance, male children are often given preferential treatment, and in such situations, may be better buffered against environmental stresses (Stinson 1985). Other studies that have identified female growth as negatively affected by environmental stress found that males tend to meet adequate nutritional intake while females do not (Chen et al. 1981; Dewey 1980, 1983).
Stature: Summary
In short, the overall trends indicate that stature decreased significantly from the Early to Middle Period with a very slight increase from the Middle to Late Period, with females showing the strongest decline in stature. Stature in central California also proved to be sexually dimorphic, with maximum differences in the Middle Period. This suggests that although males also experienced a slight decline in stature, they may have been somewhat better buffered against the impacts of nutritional stress, possibly due to sexual division of labor and/or practices of differential parental investment.
Lower Limb Proportionality
Body proportionality was evaluated using measurements of total leg length and the tibiofemoral index. These measurements were used to test hypotheses predicting temporal and regional trends in body proportionality.
Proportionality Hypothesis 1: Tibial Sensitivity and Temporal Decline in Total Leg Length
The first proportionality hypothesis predicted that total leg length would decline over time, and changes in tibial length would be the largest contributor to this decline. Statistical tests were hindered by small sample size, since proxies for
114 proportionality required data from individuals that had both femoral and tibial length measurements available. Results suggest a slight decline in total leg length and a slight increase of the tibiofemoral index, indicating an increase in tibial length relative to femoral length in individuals with both a femur and tibia in the sample. These results were not significantly different between the Middle and Late Period and leg length decline was only a few millimeters. However, in consideration of the analysis of temporal trends, femoral length increased from the Middle to Late Period while the tibia did not significantly change within the same time frame, suggesting that the rebound in stature from the Middle to Late Period is attributed mostly to an increase in femoral length. This hypothesis of using ratios and total leg length to evaluate temporal patterns in proportionality should be revisited with larger sample sizes.
Proportionality Hypothesis 2: Regional Variation
The second hypothesis for proportionality expected that the regions that experienced the greatest change in stature also would experience alterations in body proportionality such as a decline in decreased tibiofemoral index, and shorter total leg length. However, small sample size did not allow for robust statistical assessment of regional comparisons, so this hypothesis could not be thoroughly evaluated. Further evaluation with larger sample sizes is needed to accurately test this hypothesis.
Proportionality: Summary
A sample of Early Period tibial lengths would provide a stronger interpretation of lower limb proportionality. The decrease in femoral bicondylar length from the Early to Middle Period supported the presence of a biological response to
115 reduced foraging efficiency and resource depletion before the adaptation of a different subsistence strategy. If this implies that nutritional stress is best identified in central
California in a comparison of these two time periods, this is also where potential changes in proportionality should be examined.
Cranial Porosity
Cranial porosity was assessed through the prevalence of cribra orbitalia and porotic hyperostosis. Three hypotheses were tested using cranial porosity prevalence data regarding temporal trends, regional trends, and variation in stature in individuals with or without evidence of cranial porosity.
Cranial Porosity Hypothesis 1: Temporal Increase in Prevalence
The first porosity hypothesis expected an increase in prevalence and severity of both cribra orbitalia and porotic hyperostosis over time. This hypothesis was not fully supported by the results of this study. There were no temporal trends found for either sex
(or even combined sex analysis) for cribra orbitalia. Comparisons of frequencies of males and females with any level of severity of porotic hyperostosis and those with no cranial vault porosity tended to show higher prevalence in the Early Period when compared to the Middle and Late Periods, but showed no difference in prevalence between the Middle and Late Periods. Also contrary to expectation, no patterns were found in comparisons of higher severity porotic hyperostosis and those with lower severity or no porosity for either sex.
This decline in prevalence of porotic hyperostosis and no change in the prevalence of cribra orbitalia contradicts nearly the entirety of the literature regarding
116 prehistoric health during times of subsistence change. Studies typically identify a temporal increase in either porotic hyperostosis or cribra orbitalia (or sometimes both) in populations undergoing the adoption of new subsistence strategies and increased sedentism (Bartelink 2006; Broughton et al. 2010; Cohen 1977; Cohen and Armelagos
1984; Kent 1986; Larsen 1995; Steckel et al. 2002).
However, this unexpected trend may indicate a variety of explanations. For instance, it may imply that the consumption of any remnant tannins in acorn meal is not enough to inhibit nutrients such as vitamin B12 to induce an increased rate in these populations, or that the leaching process in acorn preparation is sufficient in removing most of the tannins. Consumption of nutrients such as vitamins and iron are typically adequate within the diet as long as intake is within two standard deviations within the mean, which accounts for an extremely large amount of variation of intake that is sufficient (Norgan et al. 2012).
It is also possible that the predictions of resource intensification are misleading. For example, these models point to a decline in foraging efficiency that result in populations putting more effort into obtaining and processing resources than what is returned to them from these resources. While this is reflected archaeologically as a temporal decline in abundance of large game and increased use of smaller resources, it is unclear if the actual diet composition (such as the proportion of macro and micronutrients) changes over time.
117
Cranial Porosity Hypothesis 2: Regional Trends
The second porosity hypothesis predicted regional variation in prevalence, with Bayshore populations showing the highest frequencies of cribra orbitalia and porotic hyperostosis. This hypothesis was supported for both cribra orbitalia or porotic hyperostosis. As expected, Bayshore populations consistently showed higher prevalence of all types and severity of cranial porosity than the other regions.
This trend is consistent with other studies that have shown that the prevalence of cranial porosity is high in prehistoric populations that have access to marine resources
(Lambert 1993; Lambert and Walker 1991; Holland and O’Brien 1997; Walker 1986;
Walker and Thornton 2002). While marine diets likely contain sufficient micro and macronutrients, cranial porosity can occur in shoreline populations due to diarrheal diseases from contaminated water or helminth infections from eating raw marine animals and fish (Walker 1986). Furthermore, there is archaeological evidence of parasites in shellmounds of the Canadian Pacific Coast that have the potential to inhibit nutrient absorption and retention in humans (Bathurst 2005). However, archaeological parasite remains have not yet been identified in California shoreline populations, but this finding supports the increased potential for acquired anemia in coastal populations through parasitic infection. These diseases inhibit nutrient absorption or retention through either the diarrheal disease or blood loss.
Cranial Porosity Hypothesis 3: Stature Variation and Presence of Porosity
The third porosity hypothesis expected that individuals with any severity level of cranial porosity would display shorter stature than individuals with the absence of
118 cranial porosity. Furthermore, this hypothesis predicted that individuals that show higher severity of cranial porosity would also show shorter stature than those with lower severity or absence of porosity. This hypothesis was not supported. For comparisons that could be statistically evaluated, mixed results were found but did not show stature to be statistically different in any comparison except for a comparison of Middle Period males from the combined regions sample, where individuals with moderate-to-severe porotic hyperostosis were on average taller than individuals without. However, it has been observed that Bayshore males tend to have higher prevalence of porotic hyperostosis as well as taller stature than males in other regions; since males make the majority of the
Middle Period sample with moderate-to-severe porotic hyperostosis and the sample size is relatively small, this analysis suggests there is no definitive pattern describing the relationship between stunted growth and cranial porosity.
Furthermore, sample sizes are small in these considerations of stature and cranial porosity, and further evaluation with larger sample sizes is needed to test this hypothesis. Comparisons that do have sufficient samples for statistical assessment, however, suggest no difference in mean stature between individuals with or without varying severity levels of cranial porosity. It is possible that since porotic hyperostosis and cribra orbitalia are hypothesized to be childhood diseases, affected individuals may experience delayed growth and development at a young enough age to provoke a period of catch-up growth in adolescence.
Cranial Porosity: Summary
In this study, predominant patterns in cranial porosity suggest that there was a higher prevalence of porotic hyperostosis in the Early Period than in later periods, and no
119 temporal patterns of higher severity. However, the sample sizes of porotic hyperostosis are small for two of the three regions. Bayshore males and females showed the highest prevalence of both cribra orbitalia and porotic hyperostosis, which may be attributed to their increased potential for contaminated water resources and parasitic infections due to their proximity to bodies of water and fish foods. Furthermore, no patterns in stature were identified comparing individuals with or without varying severity of cranial lesions.
Although the predominant patterns in porosity are contrary to expectations, previous analyses and discussions in this study have identified the Early and Middle
Periods as the critical timeframe for the onset of nutritional stress. The reflection of major dietary shifts in the transition from the Early to Middle Periods is further supported by
Dickel et al. (1984:441), noting that the Early Period emphasized a hunting economy versus the adoption of an acorn subsistence economy in the Middle Period that became a specialization in the Late Period. If this is true, then a higher prevalence of cranial porosity in the Early Period in this sample could be identifying biological stress responses to increased conditions of resource depletion and reduced foraging efficiency, resulting in a lower quality diet before the beginning of the Middle Period, followed by an increase in health as a reliable subsistence base was developed.
And although it seems paradoxical since it is expected that those with cranial porosity represent individuals who have experienced nutritional stress or disease and therefore should also have shorter stature, Bayshore populations tend to have the highest prevalence of cranial porosity, and Bayshore males tend to be the tallest in regional comparisons. Cranial porosity occurs during childhood, and full stature is not attained until adulthood. This means that individuals who experience nutritional stress young
120 enough to develop cribra orbitalia or porotic hyperostosis, such as from the weaning process, are still growing and may experience a period of catch-up growth. Catch-up growth is a process of accelerated growth that occurs after growth retardation, and allows for growth-stunted individuals to catch up to normal growth and development (Cameron
2012).
Study Limitations
There are several limitations in this study. The data set that was used lacked comparative data for Early Period tibial length measurements. The effect of lacking tibial measurements was compounded since they would have been integral in analyses of the tibiofemoral index and total leg length. The Interior Bay also did not have an Early
Period component, which limited certain temporal and regional analyses that would assist in identification of stress in a critical period of dietary stress in central California populations (Dickel et al. 1984).
Chronology is also an inherent issue, given that this study is comparing skeletons categorized within a time period defining few hundred to a thousand years, which has the potential to minimize differences between time periods and maximize variation within time periods, or vice versa. Although the Early, Middle, and Late Periods in central California can be broken down into smaller phases and transition periods to minimize these effects, this study did not consider the use of these shorter temporal partitions.
The assessment and interpretation of paleopathological conditions has been known to have several limitations in bioarchaeological studies. It should also be noted
121 that the percentage of the central California population affected by cribra orbitalia and porotic hyperostosis is quite high, even despite the temporal decline in porotic hyperostosis. Cribra orbitalia and porotic hyperostosis data in this study were not available for every skeleton, since some individuals had only postcrania present at time of data collection. While sample sizes are usually sufficient in most comparisons of these pathological conditions (although some samples when partitioned by both region and sex were small), the percentages were calculated by comparing individuals that were assessed for these conditions or had crania available that were complete enough for examination.
Furthermore, the sampling of bony elements that were at least 50 percent complete may also bias frequencies in that it reduces the confidence that the missing fraction of the bone does or does not have porosity. Omitted cases included those with indeterminate porosity, which could be attributed to causes not related to the etiologies of cribra orbitalia and porotic hyperostosis. These conditions mean that there may be several cases of cribra orbitalia or porotic hyperostosis, or several cases of the absence of these conditions that were not considered for this study.
Future Research
One factor not evaluated in this study is the assessment differences in the use of the stature estimation equations by Auerbach and Ruff (2010). Since a large proportion of this study used only femoral bicondylar length to estimate stature, such as with the entire Early Period sample, trends in femoral bicondylar length and stature mimicked each other from the Early to Middle Period. Comparatively, a smaller proportion of the sample used either tibial length or both measurements to estimate stature in the later
122 periods. It would be interesting to see if the inclusion of an Early Period tibial length sample for use in stature estimation would alter outcomes, which can be compared to stature calculated by the femur, and also by the combination of both bones for the same individuals. Furthermore, a more informative Interior Bay Early Period sample would benefit future study.
Lower limb proportionality could not be fully assessed in this research, so the true sensitivity of the tibia could not be evaluated. The majority of the literature does not explicitly address tibial sensitivity in declining health, but rather in improving health conditions. It would be interesting to expand on such a topic to gain a better understanding of tibia length responses on a broader spectrum of environmental conditions.
Finally, chronology is an issue in this study. The Early, Middle, and Late
Periods in central California are relatively arbitrary ranges of time that are constantly under revision. The compression of hundreds of years within a time period, even up to a thousand years, may obfuscate the real trends at play as well. Future study could consider using a tighter chronological system using smaller date ranges to evaluate trends.
Conclusions
This objective of this research was to study stature and lower limb proportionality in relation to changes in prehistoric central California subsistence patterns using a temporal and regional framework. The incorporation of the analysis of cranial porosity allowed for the evaluation of effects of major subsistence change in central
123
California. Several hypotheses were tested for temporal and regional variation in stature, proportionality, cribra orbitalia, and porotic hyperostosis.
This study was driven by three research questions: 1) if there was a decline in skeletal health in central California as predicted by resource intensification, as evidenced by a decline in stature, alterations in lower limb proportionality, and increased prevalence of cranial porosity; 2) if there is regional variation in trends of skeletal health, suggesting that differential access to resources based on geographic location is a factor in assessing skeletal health; and 3) if sexual dimorphism in stature varies over time, which would identify if one sex is impacted to a higher degree by resource depression and intensification than the other.
Results of this study show support for some predictions of temporal and regional trends in prehistoric health. A reduction of stature was observed in this study that supports the hypothesis of declining health during large-scale subsistence change.
However, contrary to expectations, a rebound in stature was identified between the
Middle and Late Period. Proportionality was not fully assessed in this study due to the absence of several Early Period osteometrics and small sample sizes. Also contrary to expectations, cranial vault porosity is less prevalent through time, and cribra orbitalia shows no significant temporal variation. Overall, this study identified that the largest changes in skeletal health occurred from the Early to Middle Period, which is consistent with assumptions of resource depression and resource intensification models.
Furthermore, the results of this research show that geography, and therefore the availability of resources in the environment, is an important consideration when studying temporal trends in skeletal health. Populations situated near the San Francisco
124
Area bayshore had a higher prevalence of cribra orbitalia and porotic hyperostosis than in the other regions, and males in this region were identified as the tallest in central
California throughout time, both of which may be related to the proximity of these populations to bodies of water and marine resources.
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APPENDIX A
Figure A1. Measurement of femoral bicondylar length.
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Figure A2. Measurement of maximum tibial length.
APPENDIX B
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