38 • Patty Stuart-Macadam 



hyperostosis reflect a positive response on the part ot the 

 body to the total pathogen load of the environment (Stuart- 

 Macadam 1987a). In areas where the load of pathogens (vir- 

 uses, bacteria, fungi, parasites) is high, it would be expected 

 that greater numbers of the population would cross the 

 threshold between an iron deficiency as an adaptive re- 

 sponse, and an iron deficiency anemia. 



An examination of the demographic picture of porotic hy- 

 perostosis in earlier populations should provide clues to the 

 biological significance of the condition. Porotic hyperostosis 

 begins to appear in Neolithic times (Stuart-Macadam 1987a), 

 it is more prevalent the closer the group is to the equator 

 (Hengen 1971), it occurs with greater frequency on lowland 

 sites than highland (Hrdlicka 1914; El-Najjar et al. 1976; 

 Ubelaker 1984), it has decreased in modem times in northern 

 Europe (Hengen 1971), and it occurs in nonhuman primates 

 (Nathan and Haas 1966). What is the significance of this? 

 Building on the ideas of previous researchers who have sug- 

 gested that porotic hyperostosis is the result of the interaction 

 of customs, diet, hygiene, parasites, and infectious diseases, 

 the concept of porotic hyperostosis as a response to high 

 pathogen loads could explain why individuals from archeo- 

 logical sites who appear to have diets rich in iron and protein 

 still have high levels of porotic hyperostosis. It could explain 

 the fact that porotic hyperostosis is more common in areas 

 such as lowland sites and tropical areas: these are areas of 

 higher pathogen loads. It could also explain why porotic 

 hyperostosis starts becoming common in the Neolithic, not 

 because of agriculture or changes in diet per se, but because 

 of greater population density which means greater exposure 

 to pathogens. 



In the past, signs of chronic disease in skeletal material 

 have been interpreted as an inability to adapt to the environ- 

 ment. However, it is becoming more widely accepted that 

 disease is the defense system's fight for health; in this view 

 evidence for chronic disease on the skeleton is seen as a 

 positive adaptation, a fight for health against the pathogen. 

 As Powell (1986) has said, "since bone lesions typically 

 occur relatively late in the progress of the disease after con- 

 siderable soft tissue involvement has commenced, their very 

 presence is indicative of long-term immune response to in- 

 fection." By a .shift in paradigm, individuals with chronic 

 bone lesions can be seen to have been more successful in 

 adapting to their environment than individuals who did not 

 live long enough to produce bony response to a pathogen. If 

 this is true, then skeletal populations that show signs of 

 chronic bone lesions may not be less "successful" than popu- 

 lations that do not show signs of chronic bones lesions. Of 

 course, ultimately, fertility and longevity are the true indica- 

 tors of successful adaptation. 



Another shift in perception in recent years has been an 

 understanding of the complexities of the interaction between 

 the host, pathogen, and environment. Scrimshaw (1964) 



wrote a classic paper in which he emphasized that the disease 

 agent is only one of a triad with host factors and environmen- 

 tal factors. He said that simply identifying the agent is not 

 sufficient to describe its cause. It must be seen as part of a 

 complex interrelationship which is dynamic, and unique to 

 every individual. These views are reflected in the more re- 

 cent work on porotic hyperostosis, as researchers carefully 

 examine as many variables as possible in the complex inter- 

 action between a population and its environment. 



This paper has presented a review of the research on poro- 

 tic hyperostosis and the development of thought that has 

 occurred over the past century regarding etiology and inter- 

 pretation. Most earlier work would fit into Armelagos et al.'s 

 (1982) descriptive-historical model of research. This refers 

 to research which focuses mainly on data description and 

 discussion of individual cases of paleopathology. In recent 

 years, there has been a shift to a population approach that 

 stresses functional interpretation of data. At the same time, 

 concepts of health and disease have been changing, along 

 with perceptions of the body and its immune system. These 

 trends have had a profound effect on research into porotic 

 hyperostosis and have stimulated new ideas and interpreta- 

 tions of data. 



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Zafireb Paleopathology Symp. 19HH 



