In this colloquium, I will be addressing two related topics. First, I will introduce the field now generally referred to as Bioarchaeology.

Transcription

1 In this colloquium, I will be addressing two related topics. First, I will introduce the field now generally referred to as Bioarchaeology. And second, I will be sharing with you what studies of human skeletons from the Mariana Islands reveal about the lives and health of the prehistoric Chamorro. 1

2 Bioarchaeology is the study of human biological remains within their cultural, or archaeological, context. The term was first coined in 1972 by the British archaeologist Grahame Clark as a reference to zooarchaeology, or the study of animal bones from archaeological sites. In 1977, Jane Buikstra, an American physical anthropologist, redefined bioarchaeology in the U.S. to refer exclusively to the scientific study of human skeletons from archaeological sites. The approach used in the U.S., which emphasizes a population-based and ecological perspective to the study of human skeletons, grew out of the New Archaeology of Lewis Binford and colleagues.

3 Skeletons represent the most direct evidence of the biology and sometimes behavior of past human groups. The study of human skeletal and dental remains provides an important context for understanding of human variation, biocultural behavior, and the quality of life in the past. 3

4 The model adopted by most bioarchaeologists to study health in past populations is the model developed by Goodman and co-workers in the 1980s. This is a biocultural or stress model, which emphasizes an individual s continuing lifelong adjustment to environmental constraints and stressors. The model focuses on the causes (cultural, genetic, and other) and the skeletal manifestations of stress, commonly referred to as indicators of stress.

5 Citing problems of selective mortality and hidden heterogeneity in individuals susceptibility to illness, Wood and others have argued that the interpretation of population health status from skeletal remains is not necessarily as straightforward as once presumed a view expressed in the so-called osteological paradox. These issues reveal that differences in the abundance of stress indicators or pathological lesions between skeletal series may not always follow the common inference that better health makes for better skeletons. 5

6 While many diseases do not affect the bone, severe and long-term stress may leave observable changes in the skeleton and teeth identified as indicators of stress. Two categories of skeletal and dental indicators of stress are recognized: non-specific and specific stress indicators.

7 Located in the northwestern Pacific, the Mariana Islands form an archipelago made up by the summits of 15 volcanic islands, and other smaller outcroppings, that stretch approximately 450 miles in a north to south direction. Guam, located in the south, is the largest island in the Marianas with a total land area of approximately 212 square miles. Saipan and Tinian are about half the size of Guam, and Rota is even smaller. In prehistory as well as today, people have preferred living in the southernmost islands, which are also the largest, oldest, and best-watered islands within the archipelago. Geologically, these islands are a combination of volcanic and raised coral deposits surrounded by a fringing reef. Today, the climate of the Mariana Islands is classified a marine tropical, with a pronounced summer monsoon season associated with heavy downpour, tropical storms, and typhoons.

8 When the first European explorers arrived in 1521, they found the islands inhabited by a single group of people who spoke an Austronesian language, Chamorro. It is estimated that human settlement of the Mariana Islands began approximately 3,500 BP, with permanent occupation probably not occurring until approximately 2,000 years BP. Based on linguistic and archaeological evidence, the most likely source of these earliest settlers is island Southeast Asia and the Philippines. Chamorro prehistory is traditionally divided into three periods: Pre-Latte, Transitional Pre-Latte, and Latte Periods. The term, latte refers to a form of paired stone pillars and cup-shaped capitals or capstones, which very likely were used to support houses, meeting halls and/or religious structures. One of the largest latte sets is the one found on the island of Tinian, the House of Taga. Latte structures are nearly always associated with burials, typically interred within the perimeter of these structures. The Latte Period extends into the proto-historic Period, which began with Magellan s historic landfall in Guam in 1521 and terminated with the forcible removal of the Chamorro from Saipan, Tinian, and Rota to the island of Guam in

9 The precontact Chamorro subsisted on cultivated tree and root crops typical of the tropical island environment, such as coconut, banana, breadfruit, taro, yam, and eventually rice. They also subsisted on fish and shellfish found in the surrounding reefs, reef flats, and deep-water environments. 9

10 In 1995, Douglas Hanson and I organized a symposium on the bioarchaeology of the Marianas Islands for the American Association of Physical Anthropologists meeting, which was held in Oakland, California. Among the papers that were subsequently published in a special issue of AJPA in 1997, was one written by me and two of my then graduate students that summarized the health and life style of the inhabitants of the Mariana Islands. 10

11 The sample used in this survey included 383 individual skeletons representing transitional pre-latte and Latte periods, which were recovered during Cultural Resource Management (CRM) projects in the Mariana Islands region in the 1980s and 1990s.

12 Although there are some biases in the age and sex representation of the samples, this earlier survey reported life expectancy at birth for three of the largest skeletal samples from Guam and Saipan, that ranged from 26 to 34 years of age. The average adult age for these same three series ranges from years. 12

13 Using the Mean Childhood Mortality (MCM) statistic, relatively high fertility rates, ranging from 4-6 children for women who survived to age 15 to 45 years, were observed for these three prehistoric skeletal series. Barring any disasters, these fertility rates support a steady increase in increase in population numbers expected of an island ecosystem. 13

14 The average statures of prehistoric males from the Mariana Islands ranged from 170 to 176 centimeters (about 5 7 to 5 9 ), statures that are comparable to prehistoric Polynesians. 14

15 The average female statures ranged from 159 to 164 centimeters (about 5 2 to 5 4 ). 15

16 Although the prehistoric inhabitants of the Mariana Islands were relatively healthy, they did suffer from a number of diseases, including yaws, a skin disease that can leave distinctive lesions in the skeleton, degenerative joint disease, and possibly iron deficiency anemia. 16

17 Despite diets rich in root starch and sugars, prehistoric Chamorro teeth show little evidence of dental caries (tooth decay), antemortem tooth loss, or dental abscessing. The chewing of Areca, or betel, nut with lime and the leaves of the pepper leaf, which is common throughout South/Southeast Asia and the western Pacific, may have contributed to this good dental health. There is now a substantial epidemiological literature demonstrating that betel chewing, which stains the teeth a reddish brown, may prevent dental caries while increasing the frequencies of periodontal disease, calculus, and dental attrition. It is of note that the teeth of pre-latte period skeletons from Guam do not exhibit dental staining.

18 Evidence in skeletons of prehistoric Chamorro indicate they led strenuous lives involving physical activities. Spondylolysis, or stress fractures of the lower back, and well developed occipital tubercles in the back and base of the skull have been attributed to the seafaring culture, agricultural subsistence, and the construction and transport of heavy latte stones prior to contact with Spanish explorers in the early 16 th century.

19 In addition to providing one of the first summaries of the health and lifestyles of the prehistoric inhabitants of the Mariana Islands, our earlier survey suggested that the prehistoric inhabitants of the smaller islands located north of Guam, such as Saipan and Tinian, experienced higher levels of specific and non-specific indicators of stress than the prehistoric inhabitants of Guam. Possible explanations for the observed difference included environmental factors, such as lower rainfall, slightly cooler temperatures, inadequate water supply, remoteness, narrow and non-continuous fringing reefs. Also earthquakes, volcanic eruptions, and sea level fluctuations, may make these smaller and more remote islands more susceptible to environmental distresses. 19

20 With this as backdrop, I wish now to share some of the results of recent work that examines health and lifestyle in prehistoric skeletons from Saipan and Tinian Islands with those from Guam. It is predicted that the estimators of physiological stress examined in this study will be greater in the prehistoric skeletons from Tinian than in those from Saipan and, when combined, higher levels of stress indicators will be observed in the skeletons from Tinian and Saipan when compared to those from Guam. 20

21 A total of 227 skeletons, mostly from the Latte Period, from Tinian, Saipan, and Guam are used in these comparisons. The majority of the skeletons from Tinian (20) and an additional 26 skeletons from Saipan were not available in our earlier survey. 21

22 The general indicators of systemic stress that I examine are: Stature Linear enamel hypoplasia (LEH) Cribra orbitalia (CO) 22

23 The specific indicators of stress examined: Limb bone fractures Spondylolysis Dental pathology (AMTL, caries, alveolar resorption, alveolar defect, calculus, attrition) Infection (treponemal disease) Statistical tests: Fisher s exact test and Student's t-test 23

24 Using stature formulae for Polynesian Maori, no significant differences in adult stature were found for the prehistoric skeletons from Tinian, Saipan, and Guam. On average, the prehistoric male Mariana Islanders were relatively tall (5 8 or 173 cm), while female Chamorro were about 4 inches shorter than male Chamorro. 24

25 Linear enamel hypoplasias (LEH) result from a disruption of enamel development during infancy and early childhood due to a variety of stressors, in the mother and/or child, including malnutrition, metabolic disorders, acute and chronic infections, physical trauma, and hereditary conditions. The frequency (8.9%) of LEH in the Tinian series is very low. A significantly higher frequency of LEH (34.0%) is reported in the Saipan series. The combined frequency of occurrence of LEH in the Tinian and Saipan series (21.6%) is significantly less than that observed for the combined Guam series (31.0%). Thus, this general indicator of stress indicates that the prehistoric Chamorro experienced physiological stress in the early years of their development, especially in the two largest islands. 25

26 Cribra orbitalia, a porosity of the orbital roof, which is a form of porotic hyperostosis of the cranial vault, is commonly attributed to the presence of iron deficiency anemia. Similar frequencies of CO were observed in the Tinian (29.4%) and Saipan (20.0%) skeletons. The combined frequency of CO in the Tinian and Saipan series (22.2%) is significantly higher than the frequency reported for the Guam series (7.1%). 26

27 Fractures of the major long limb bones in adults provide an indication of the frequency and type of traumatic, accidental or deliberate, injury in a population. Identical frequencies (1.1%) of limb bone fractures were observed in the Tinian and Saipan series and a slightly lower frequency (0.8%) is reported for the skeletal series from Guam. Overall, accidental or deliberate injury, as indicated by limb bone fracture, is extremely rare in the prehistoric Mariana Islanders. 27

28 The frequency of spondylolysis, or a stress fracture of the lower lumbar vertebrae, is similar in the Tinian (2.8%) and Saipan series (1.3%). Although not statistically significant, a somewhat higher frequency of spondylolysis is reported for Guam (6.7%) compared to the combined frequency of this condition in the skeletons from Tinian and Saipan (1.8%). The higher prevalence of this indicator and healed bone fractures in the skeletons from Guam suggest that the inhabitants of this island may have experienced more stress involving physical labor and or cultural practices than those living on the more northerly islands. 28

29 Very similar frequencies of betel staining were observed in the Tinian (80.3%) and Saipan (75.3%) dentitions. However, the combined frequency of betel stained teeth in the skeletons from Tinian and Saipan (77.3%) was found to be significantly higher than frequency of betel stained teeth reported for Guam (53.3%). 29

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31 Dental caries is a de-mineralization of the tooth structures caused by organic acids produced by bacterial processes involved in the fermentation of dietary carbohydrates. Very similar frequencies of carious lesions were observed in the Tinian (4.6%) and Saipan (7.1%) teeth. A significantly higher frequency of carious teeth is reported for the Guam skeletal series (10.1%) compared to the combined Tinian and Saipan series (6.1%). 31

32 Alveolar resorption is related to the removal of alveolar bone due to inflammation of the supporting tissues of the teeth often associated with periodontal disease. Here, we report frequencies of advanced resorption. A significantly higher frequency of alveolar resorption was found in the Saipan (58.6%) series compared Tinian series (24.4%). The combined frequency of alveolar resorption in the Tinian and Saipan series (49.6%) is significantly higher than that reported for the Guam series (28.3%) suggesting periodontal disease was more prevalent for those living on Tinian and Saipan. 32

33 The frequency of dental abscessing in the Tinian series (3.8%) is not significantly different from that reported for the Saipan series (6.0%). The overall frequency of alveolar defects for Tinian and Saipan (5.3%) is slightly higher than the frequency reported for the Guamanian series (4.6%), but the difference is not statistically significant. 33

34 Dental calculus, which is calcified or mineralized dental plaque, is one of the most common dental diseases in the living and past peoples. Among the contributing factors to plaque buildup are an alkaline oral environment, mineral content of drinking water, and dental hygiene. The frequency of advanced calculus in the Tinian series (14.1%) is higher, but not significantly higher, than the frequency of calculus reported for the Saipan series (10.5%). However, a significantly higher (15.6%) frequency of advanced calculus buildup was observed in the Guam series compared to the combined Tinian and Saipan series (11.8%). 34

35 Very similar frequencies of advanced dental attrition were observed in the Tinian (47.0%) and Saipan (48.7%) series, and the combined frequency of advanced attrition (48.1%) for the Tinian and Saipan series is statistically higher than that observed in the Guam series (26.3%). 35

36 Yaws is an infection caused by a bacteria [Treponema pallidum, subspecies pertenue ] that is closely related to one that causes syphilis. Yaws is a long-term (chronic) infection that mainly affects the skin, bones, and joints, primarily of children, living in warm tropical regions including the western Pacific. Unlike syphilis, yaws is not sexually transmitted. Yaws is transmitted by direct contact with skin sores of infected people. While the skeletal manifestations of yaws and syphilis are similar, it is generally acknowledged that venereal syphilis was absent in the Mariana Islands prior to contact with Europeans. Therefore bony lesions with manifestations typical of treponemal infections from the Mariana Islands are usually diagnosed as evidence of yaws. The overall frequency of treponemal infection in the Tinian series (8.7%) is lower but not significantly different from the frequency of treponemal infections reported for the adult skeletons from Saipan (12.7%). The combined frequency of treponemal infection in the Tinian and Saipan series (12.0%) is not significantly different from the frequency reported for skeletons from Guam (8.1%). 36

37 Comparisons of the indicators of health and lifestyle in the skeletons from Tinian and Saipan reveal few significant differences. When comparisons are made with the Tinian series, significantly higher frequencies of LEH, AMTL, and alveolar resorption were observed in the skeletons from Saipan. Differing age-at-death profiles may contribute to the differences in dental pathology, while a slightly higher rate of infection in the Saipan skeletal series may result in increased childhood stress reflected in the LEH prevalence. 37

38 When the skeletons from Tinian and Saipan are compared to those from Guam: Significantly higher frequencies of LEH, dental caries, and dental calculus are observed in the skeletons from Guam Significantly higher frequencies of alveolar resorption, dental attrition, and betel staining are observed in the skeletons from Tinian and Saipan The significantly higher frequency of betel-stained teeth in the Tinian and Saipan series may explain the higher frequencies of AMTL, alveolar resorption, and attrition observed as well as the lower caries rate in the teeth from these two islands compared to Guam. 38

39 As was found in the earlier survey, this new study indicates that these prehistoric Chamorro were generally of good health. The frequencies for many of the indicators, such as fractures, AMTL, dental caries, dental abscessing, and infection, are very low. Comparisons between Tinian and Saipan Islands reveal few differences. However, when the skeletons from Tinian and Saipan are compared to those from Guam, significantly higher frequencies for several indicators suggest more childhood stress and oral-dental disease in the Guam skeletal series. Unexpectedly, these most recent results suggest that the prehistoric inhabitants of Tinian were subjected to less stress levels than those living on the larger islands of Saipan and Guam. Some of the differences in dental pathology may be related to the cultural practice of chewing Areca nut with or without the use of slaked lime. Other observed differences may be attributed to increasing population size, changes in marine resource utilization, differences in diet, temporal differences in the skeletal series, and contact with Europeans. Continued work in the field of bioarchaeology, including isotopic and adna studies, will build on the existing database for understanding the health and wellbeing, lifestyle, and behavior of the earliest inhabitants of the Mariana Islands.

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