Stress, adaptation, and 

 enamel developmental defects 



Alan H. Goodman 



In recent years we have witnessed an impressive growth in 

 research on the evolution of disease. While the ultimate aims 

 of paleopathologists were once merely to describe the occur- 

 rence of lesions and infirmities in relationship to the time and 

 location of those long dead, most researchers now strive to 

 understand the significance of their data for the lives of the 

 individuals and populations under investigation. Temporal 

 changes in the pattern of health and disease are now seen as 

 important keys to understanding human evolution, and the 

 distribution of disease over ecological and socioeconomic 

 landscapes is increasingly seen as critical to understanding 

 the human condition, past and present. 



With these broader and deeper questions on disease, evo- 

 lution, and the human condition comes an increased need to 

 understand the context of our paleopathological data. In or- 

 der to understand who dies and who gets sick, and the impact 

 of these events on individuals and populations, one must 

 understand the available ecological and social resources, 

 population sizes, social stratification, systems of power, re- 

 source distribution and the like. At present, I hope it will 

 suffice to say that the need for context — not just ecological 

 and demographic, but broadly social, political, and econom- 

 ic — forces paleopathologists to pay greater attention to col- 

 leagues in anthropology and archeology who share the goal 

 of knowing something of the daily lives and struggles of past 

 populations. 



With the asking of questions about the effects of lesions on 

 peoples' lives comes a well-placed need to understand firmly 

 the biobehavioral significance of the underlying condition 

 causing these scars. How chronic and long lasting might the 

 underlying illness have been? How often does a bony scar 

 signify a condition which leads to reduced work capacity, 

 reproductive potential, or length of life? 



The potential disparity in interpretation of the adaptive 

 significance of lesions has recently been highlighted by 

 Ortner ( 1 979:596, and this volume) with particular reference 

 to infectious lesions. Most researchers have assumed that 

 lesions generally are signs of stress and, by extension, prob- 

 lems in adaptation (c.f Goodman, Martin et al. 1984). Their 

 questions have revolved around understanding the degree of 

 280 



stress and adaptive constraint signified by lesions. Ortner. on 

 the other hand, has challenged the basic assumption that 

 those with lesions are less biologically adapted. He proposes 

 that skeletal lesions may be indications of the individual's 

 ability to "rally" from insults. This proposition in based on 

 the notion that lesions are found paradoxically on individuals 

 that survived with the underlying perturbation. These bony 

 scars, therefore, are signs of survival. 



The above variability in perspective is particularly critical 

 to the analysis and interpretation of enamel hypoplasias and 

 other developmental defects of dental enamel. Linear or 

 chronologic enamel hypoplasias, deficiencies in enamel 

 thickness resulting from a temporary cessation in enamel 

 matrix apposition (Samat and Schour 1941; Goodman, Ar- 

 melagos, and Rose 1980), have long been considered to re- 

 flect nonspecific physiological stress during tooth crown 

 formation (Samat and Schour 1941 ; Kreshover 1960). Hypo- 

 plasias are, without denial, a markerofa condition which the 

 individual survived. 



Based on clinical and experimental data (see recent re- 

 views by Cutress and Suckling 1982, Jontel and Linde 1986, 

 and Pindborg 1982) paleopathologists have frequently and 

 increasingly interpreted those with hypoplasias to be more 

 stressed and less well adapted than those without hypo- 

 plasias. For example, Swardstedt (1966) has shown that the 

 frequency of enamel hypoplasias decreases significantly 

 from a slave class to a land-owning class in Westerhus, a 

 Medieval Swedish population . These data are consistent with 

 increased cultural buffering of the stresses of disease and 

 malnutrition in families owning land. In a recent volume on 

 health changes at the origins of agriculture (Cohen and Ar- 

 melagos 1984), 15 of 19 (79%) regional case studies reported 

 on changes in frequency of hypoplasias from gathering- 

 hunting to agriculture. All participants considered increased 

 hypoplasia frequencies to signify increased stress. Ortner's 

 comments notwithstanding, hypoplasias have been reified as 

 prime indicators of stress in paleopathological studies. 



Are we justified in considering hypoplasias to be general 

 indicators of stress? If so, what is the degree of disruption and 

 limit to function signified by hypoplasias? The purpose of 



Zagreb Paleopathology Symp. 1988 



