4.5 DIET AND DENTITION IN ARCHAEOLOGY
There has been a century-long interest in the interrelationships between the human dentition and diet. Mummary in 1870 was the first of several researchers to investigate the dental caries experience of prehistoric British populations. His conclusion that caries incidence increased as advances in food technology produced increasingly refined foods, softer in texture and richer in sugar was extensively cited in textbooks of that era. Those results have been substantiated by recent researchers.
II. SYSTEMIC DISTURBANCE
Any disturbance, such as severe infection can disrupt enamel
formation. That disruption of enamel formation will leave an enduring
record as a disorientation of enamel prisms. Because the human dental
growth sequence is known, the age at which the enamel disturbance
occurred can be determined from the location of the disturbance
within the enamel. A standard chart for dental development can be
consulted for this purpose.
There is an extensive literature (now in excess of 500 articles) on the epidemiology and etiology of enamel defects. Many are investigations using laboratory animals.
There are two types of enamel developmental disturbance of interest to the paleoanthropologist.
(1) Microdefects are histological structures known as Wilson bands. These are accentuated brown striae of Retzius. The most celebrated of these is the neontal line, reported by Schour in 1936.
If the disturbance is short in duration and the enamel formation resumes, that disturbance is recorded as a narrow band seen in the section of enamel under a light microscope. That evidence of enamel formation disruption and recovery is called a Wilson band.
Wilson bands are thin layers of abnormally structured enamel marking the position of the active ameoloblasts (Gr = enamel formers) at the time of insult. Wilson bands are sometimes called 'pathological brown striae' in the literature. This descriptive term is a nice way to describe the bands which contain 'sudden changes in prism direction associated with atypical rod forms.' Wide neonatal lines are associated with traumatic births. Wilson bands appear to represent brief periods of stress lasting from one to five days.
The examination of teeth for histological disturbance is destructive; therefore, this technique is not used of rare ancient hominid teeth.
(2) Macrodefects are defects visible on the tooth surface. They are known as hypoplasias. These can vary in appearance from small pits or furrows to large, deep grooves or even large areas of missing enamel. Typically these defects are horizontal grooves that are called chronological or linear enamel hypoplasias. They seem to reflect impairment of enamel formation for weeks or months, while Wilson lines record events limited to one or a few days.
If the enamel formation does not resume, the defect can be viewed macroscopically as a transverse area of depressed enamel. This is known as enamel hypoplasia.
Enamel hypoplasias show a predilection for anterior teeth and for the cervical and middle thirds of tooth crowns.
Investigators have shown statistical associations between enamel hypoplasias and a variety of clinical conditions of which we will only mention a few here: premature birth, malnutrition, fluorosis, high fever, localized trauma and systemic metabolic distress such as gastrointestinal disorders.
III. SOCIAL AND ECONOMIC IMPLICATIONS
We introduce this section with a vignette about Rudolph Virchow (1821-1902), an early anthropologist, statesman and founder of modern pathology. As a young physician in his twenties Virchou was sent to study a poverty-stricken area in Poland. There has been an outbreak of typhus there and the task of his commission was to make recommendations to the German Second Reich on ways to cope with it. His conclusions reached beyond medicine into issues of social justice.
Virchow's recommendation was crisp and remarkable: "...education, with its daughters, liberty and prosperity" would end the epidemics. Typhus, a disease of war and poverty could be eradicated by economic and social improvement.
(My note: the correlation between life conditions and health is well known to sociologists. They have christened it as the socioeconomic gradient. The classic work in the field is Marmot's highly respected Whitehall Study which finds that there is a strong correlation between rank in British governmental bureaucracy and coronary heart disease. Incidentally, it has been confirmed in baboons which have hierarchal societies. Marmot and his colleagues have found that a sense of control is the underlying factor that plays a significant role in the incidence of coronary heart disease.)
Epidemiological studies of the incidence of enamel hypoplasias in contemporary populations support a general association between hypoplasias and general living conditions. Persons in First World industrialized nations tend to have lower rates of enamel defects as compared with those from underdeveloped areas. The frequency of individuals with one or more hypoplasias is generally less than ten percent in most populations from developed, industrialized countries. In comparison, enamel hypoplasias are frequently quite common in children from impoverished countries. A study from 1930 reported nearly 90% of Chinese children had some form of an enamel defect.
A study at the University of Illinois College of Dentistry by Massler, Schour, and Poncher reported in 1941 is a classic in the field. They examined teeth obtained from the free extraction clinic and found that the teeth of "well-to-do" individuals in their modern North American tooth (Chicago) sample were better calcified than the teeth obtained from the poorer members of the community. The investigators attributed this difference in calcification quality to differential access to nutritional resources.
The incidences of enamel hypoplasias are inversely related to nutritional and socio-economic status.
These comments verify that there is an association between increased frequencies of enamel defects and nutritional conditions or clinical disease.
This is the logical basis for inferring stressors in the lives of prehistoric individuals found with enamel defects.
Studies in the Mexican highlands have confirmed the link between stress, socioeconomic status and life history. Children with enamel defects have reduced body weights and heights-for-age in comparison with children who lack defects. Hypoplasias tend to be from families of lower economic status.
In rural Mexico and Guatamala, children receiving dietary supplements have far few linear enamel hypoplasias than their non supplemented peers.
IV. ANTHROPOLOGIC STUDIES OF DENTAL DEFECTS
There are recurring themes in the study of enamel defects.
(1) Transition from hunter-gatherer subsistence to agriculture. It is suggested that increased reliance on one food resource carries risk of seasonal deficiencies. Increased sedentism might enhance transition of childhood diseases. Examples include the increase in hypoplastic defect from the Mesolithic to early agricultural contexts in the Levant (Eastern Mediterranean), and with more intensive agriculture in Ecuador.
The most detailed studies have been carried out near here at the Dickson Mounds site south of Peoria. The change from Late Woodland to Mississippian cultural contexts was not only associated with increased defect frequencies but also increasingly annual spacing between growth disruptions and earlier average age at disruption.
(My comment on prehistoric Indian studies: Dickson is a large Indian mound along the Illinois River. Initially it was private property and was privately excavated. Hundreds of skeletons and artifacts were found; in time it became the museum that it is today. After many protests by Native Americans, the skeletons were closed to the public--and to anthropologists. The wealth of material and the times they represent has made Dickson Mounds an extremely interesting site for researchers who study the transition from food foraging to maize agriculture.)
Studies conflict as to whether boys or girls are more affected by dental defects. This illustrates another dimension in the transition from foraging to farming. That transition is associated with a more settled life, development of social stratification, and concentrations of wealth and power in society. It appears that higher status individuals had fewer dental defects. They were better fed.
(2) The modal age of growth disruption at weaning. Breast feeding ensures a supply of maternal antibodies, buffers the impact of nutritional deficiencies, and so has a protective effect that is lost at weaning which might be reflected in higher defect rates. Examples of this interpretation include ancient Egyptians and Nubians. West Indian slaves, and Aboriginal Australians. Similar suggestions have been made for Wilson bands.
The association of enamel defects with weaning is not a settled issue. The link between enamel defects and weaning may be coincidental in many circumstances.
(3) The arrival of Europeans in the New World. Introduction of new pathogens to indigenous populations can increase growth disruption in children. Newly arrived, Europeans may have in turn have had their own food supply problems. In Georgia, the contact period Spanish mission of Santa Catalina de Guale had more growth disruptions than pre contact agriculturalists.
V. Enamel Endurance
Enamel structure is usually not affected in archaeological specimens under most conditions on burial. On occasion, the enamel caps of the crowns may be the only part of a body to survive. Enamel tends to be lost in very acid soils.
In a cremation, the enamel of erupted teeth rapidly flakes away from the dentin, but the unerupted teeth receive a measure of protection from their bony crypts and their enamel may be retained. In this situation the enamel surface is cracked and is no longer glossy; however, the prism structure can still be seen after heating to 800 degrees centigrade.
Enamel defect data cannot be used in isolation. It must always be used in conjunction with the full spectrum of nutritional, dietary, and subsistence analyses. Enamel defect data can be used to determine which period of childhood development was associated with nutritional deficiencies, but the nature of the deficiency must be determined by other techniques such as paleopathology, dental caries, trace element analysis, faunal and floral studies, and the archaeological reconstruction of subsistence strategies.
..... CJ '99
Alt., Rosing, F., and Teschler-Nicola, M. eds Dental Anthropology Fundamentals Limits and Prospects. New York: SpringerWien, 1998.
Anderson, R. Magic, Science, and Health. New York: Harcourt Brace College Publishers, 1996.
Garbarino, M. and Sasso, R. Native American Heritage. Prospect Heights: Waveland Press, Inc., 1994.
Goodman, A. and Rose, J. "Dental Enamel Hypoplasias as Indicators of Nutritional Status" in Advances in Dental Anthropology. New York: Wiley-Liss, Inc., 1991.
Goodman, A. "Developmental Defects in Dental Enamel" Cambridge Encyclopedia of Human Growth and Development New York: Cambridge University Press, 1998 pp210-211.
Hillson, S. Dental Anthropology. New York: Cambridge University Press, 1996.
Larsen, C. Bioarchaeology Interpreting Behavior from the Human Skeleton. New York: Cambridge University Press, 1999.
Marmot, M. et al "Contribution of job control and other risk factors to social variations in coronary heart disease incidence" The Lancet Vol 350: July 26,1997 pp 235-239.
Roberts, C. and Manchester, K. The Archaeology of Disease 2nd ed. Ithica: Cornell University Press, 1995.
Rose, J. et al "Diet and Dentition: Developmental Disturbances" in The Analysis of Prehistoric Diets. New York: Academic Press, 1985.