Bioarchaeology integrates osteology within a biocultural context
In most bioarchaeological studies, remnants of skeletons and bones are used as a proxy to reconstruct bodies within their cultural setting. Precisely because bioarchaeology is anthropology (Armelagos 2003), it places some of the focus on the actions (behaviors, habits, and occupations) and beliefs (ideology, social structures, subsistence, and economics) of humans and what these reveal about their life histories. Bioarchaeologists often focus on how humans adapt to diverse environments and the ways that biological and cultural processes work together to shape individual life histories and group survival. Thus, processes that can cause early death such as poor diet, disease, or violence are of central importance.
As anthropologists, bioarchaeologists are highly specialized within their area, yet they must remain generalists in the ways that observations of the human condition are interpreted. Addressing these kinds of complex topical areas requires researchers to use and synthesize information from many different areas within anthropology (including archaeology and biological anthropology) along with an impressive array of methods and data from other fields. Models and frameworks have been developed over the years to be used as heuristic devices. These are important for helping to organize and systematize the ways that data are collected and analyzed.
One of the earliest attempts to model complex factors having to do with archaeological bodies and the social processes that affect bodies was by Buikstra, who together with a group of biological anthropologists with osteological and archaeological training, had a vision of working with human remains that departed from prior approaches by directing research into more contextualized and integrative areas. Buikstra describes this history as a major conceptual and theoretical breakthrough with the incorporation of archaeological and mortuary context, and the application of an interdisciplinary perspective. The model she presented (Figure 2.3) became the basis for shifting the study of ancient burials from descriptive to a more integrated scientific approach (Buikstra 1977: 71). In this new approach, human remains were placed within a larger context that included the mortuary component, grave goods, and the relationship of the burials to the larger archaeological site reconstructions. In this way, studies of the dead were seen as being linked to studies of the living in terms of social behaviors and biological well-being.
Goodman and colleagues (1984: 14) provided a more focused and detailed framework that emphasized modeling physiological disruption (or, stress) within a larger context of environmental and cultural factors that prevent or manufacture
FIGURE 2.3 A model demonstrating all of the important variables that need to be considered beyond the analysis of the human remains. Adapted from Buikstra (1977: 82), with permission from author.
stress. This model was designed for population-level analysis of disease and thus incorporates ideas about the physiologically stressed body from the fields of epidemiology and stress research (Figure 2.4). This model is general enough so that it can be modified for particular populations to address specific problems, and it provides a systematic framework for integrating information regarding human adaptability and health with the larger biocultural and ecological context. In this model the physical environment is viewed as the source of resources essential for survival. If there are constraints on the resources, then the ability of the population to survive may be limited accordingly (Figure 2.4, box 1).
Cultural systems and beliefs are important to our understanding of overall health and sensitivity to stress. In most cases, these systems and beliefs act as buffering mechanisms, protecting individuals during physiologically dangerous times such as weaning or changes in environmental conditions. Sometimes, however, cultural
FIGURE 2.4 A model demonstrating the systemic stress perspective and the kinds of variables that can be brought to bear on the analysis of the human remains.
systems can act to introduce stress or dietary deficiency. This is particularly true in the case of some food taboos that may limit nutritional intake based on life stages. For example, food taboos existing during pregnancy may make some foods off- limits to pregnant women (e.g., Osterholtz et al. 2014). In some cases, marriage patterns may also increase the prevalence of genetic anomalies or expose adolescent girls to pregnancies at very young ages (e.g., Baustian 2010).
The adaptation of human populations is more often enhanced by a cultural system that buffers the population from environmental stressors (Figure 2.4 , box 2). The technology, social organization, and even the ideology of a group provide a filter through which environmental stressors pass.
Although cultural and behavioral responses may effectively buffer inhabitants during some environmental perturbations, stressors in some places at some times may be so significant that cultural responses are not successful buffers. For example, if cultigens were relied on increasingly through time, it would make it difficult to meet dietary requirements should there be crop failure several years in a row. This problem would be compounded if the group size was growing and if there was an investment in a rigid set of adaptive strategies. On the other hand, increased sharing, storage capacity, trading, and redistribution of limited resources along with flexibility in resource type and procurement could offset the stress produced by crop production. Thus, reliance on cultigens is perceived as both a buffer during ecologically favorable times and a stressor during periods of drought.
The inability of an individual to resist a stressor results in physiological disruptions (Figure 2.4, box 4). The severity of the disruption depends on many factors. Age, sex, health status, genetic composition, and nutritional constitution are especially critical factors. For example, a nutritional deficiency that occurs during a critical phase of growth may affect several biological systems. Decreased activity, increased use of fat stores, and decreased skeletal growth are a few of the possible responses. A similar deficiency that occurs after growth ceases may have little lasting effect on the biological system.
Target organs must be considered in studying the impact of stressors. For example, the adult human skeletal system is relatively immune to mild and short-term nutritional deficiencies. However, the skeletal system is in constant communication and cooperation with other systems. The primary functions of the skeleton are support and locomotion; storage and regulation of minerals (especially calcium and phosphorus); protection of the brain, spinal cord, and other organs; and the production of red blood cells (White et al. 2012). The diversity of functions in this one system indicates the degree to which the entire body dependents on the skeleton. Thus, a careful “reading” of subtle morphological changes can be very revealing of physiological disruptions.
Although the record is far from complete, many stressors leave markers on bones and teeth. These markers can be used to reconstruct the history of morbidity and mortality experienced during infancy and childhood. From this record of the type, severity, frequency, and distribution of ill health, we can begin to draw inferences about the presence of stress and its functional and adaptive effects on the individual and on the group. The adult skeleton may not show effects of mild stressors, but the growing bones and teeth of children often are altered in measurable ways. Specifically, chronic or episodic physiological stress can disrupt growth, and these disruptions often leave permanent markers on bone and teeth that persist into adulthood. These retrospective indicators of previous physiological insults are among the most useful indicators of diet and disease for ancient skeletal remains.
Multiple stress indicators are used to determine the degree and patterning of the stress by looking for patterns of acute and chronic stress, for patterns of stress among different subgroups by age and sex, and for patterns of severity of and response to pathogens in the environment. Understanding physiological disruption and the impact of stress on the population feeds directly back into the understanding of cultural buffering and environmental constraints, and is presented in the model as a feedback mechanism (Figure 2.4, box 5). It is extremely important to understand how disease and death have important functional and adaptive consequences for the community. Poor health can reduce work capacity of adults without necessarily causing death. Decreased reproductive capacity may occur if maternal morbidity and mortality are high in the youngest adult females. Individuals experiencing debilitating or chronic health problems may disrupt the patterning of social interactions and social unity and may strain the system of social support.
The documentation of patterns of ancient disease should ultimately be channeled back into the discussion of human behavior and culture change. In modern society, health of infants and children is delicately linked to the function of mothers, families, and communities. Similar dynamics exist for all human groups, and these interrelated issues must be explored for ancient communities. The archaeologist is in a unique position to monitor the dynamics between changes in the ecological and cultural environment and changes in human response.
To address these hypotheses, the demographic and biological impact of stress must be measured by skeletal indicators of growth disruption, disease, and death. Pathological alterations on bone are assessed primarily through the systematic description oflesions. Patterns of growth and development also provide information on stress. Demographically, a majority of the human remains recovered are under the age of18, and we are able to document growth and development of both dental and skeletal tissue during critical stages and compare this to known values for well- nourished and healthy groups, as well as modern groups living in similarly marginal areas. Identifiable, age-specific disruptions in growth yield important information on patterns of childhood developmental disturbances and physiological disruption. The distribution and frequency of specific diseases (nutritional, metabolic, infectious, and degenerative) are also an essential part of the osteological analysis. The patterning and frequencies of nutritional diseases, such as iron-deficiency anemia, are documented for many precontact populations and has obvious implications for understanding adequacy of diet. Infectious diseases, likewise well documented for many skeletal series, provide an indicator of demographic patterning, population density, and degree of sedentism.
Others have added new dimensions and enhanced the biocultural model by factoring in things such as mortuary context and funerary goods, as well as archival and historical documents. Sheridan (1999, 2002) created an expanded version ofthe biocultural model that emphasized historical information (Figure 2.5). This is just one example of how bioarchaeologists organize complex data sets from a diverse range of topics. This has led to more sophisticated ideas about the ways that human biology and culture are embedded in a matrix of contexts that can be reconstructed using multiple lines of evidence. For her research, this biocultural model helps to integrate a wide range of data from the archaeological record, historical documents, and the human remains. Her research questions include understanding the patterns of social stratification and differential access to limited resources as well as poor childhood health and occupationally related stress on the bodies of the adults. Without using a model such as this as a purely heuristic device, it would be difficult to maintain integration across the various data sets.
Thus, to factor in all the complexity of factors that affect demography and health for ancient groups there are many different approaches. Bioarchaeologists have to decide what is most useful for weighing the importance among a number of
FIGURE 2.5 A model demonstrating variables that may be utilized if there is access to ethnohistoric documents and other kinds of evidence. Adapted from Sheridan (1999, 2002) with permission from author.
factors. To focus more clearly on major spheres of interaction, the preceding models (Figures 2.3—2.5) have advanced how bioarchaeology and paleopathology studies are conducted. The cultural and noncultural stressors that cause observed bone changes can often be inferred. Occurrence of stress markers at different stages in the life cycle can be examined and compared to the mortality rates of the group as a whole. Life history events end up structuring many of the biocultural approaches to understanding disease and early death. For example, sick mothers can give birth to sick children. Weaning places many biological stresses on infants. Thus, life history is crucial in thinking about the more important places where disease and trauma may prove crucial in overall survival.
In summary, our interest in the inhabitants of the ancient past is not to learn about specific health problems so much as it is to learn about humans in general and their unique ways of coping with change over time. When are humans able to be resilient and flexible in the face of change, and when are they forced to migrate or die trying to adapt to new life-threatening situations such as drought or warfare? What has been the process of sedentism, and what is the relationship of sedentism to health? What has been the impact of sedentism on population growth? What has been the process of aggregation and how has it affected the pattern of disease? If there has been an increase in disease, how have the populations responded to the increase in disease load? Biocultural perspectives and bioarchaeological modeling can answer these kinds of questions. Bioarchaeological studies take advantage of dietary and health data to provide time depth and geographic variability to the understanding of short- and long-term consequences and mechanisms of adaptation to change.