Question

What factors are likely to have caused the health of Native Americans to decline for many centuries prior to European contact?

Answer 1

PREVALENT HEALTH PROBLEMS IN PRE-COLUMBIAN TIMES

Iron deficiency anemia

Porotic hyperostosis is a descriptive term for lesions primarily found on the parietal and orbital bones of the cranium, produced by bone marrow proliferation diagnostic of anemia. The lesion generally takes the form of a raised, porous area that develops when the trabecular portion of the cranial bone (diploë) expands and the outer table of bone becomes thinner, exposing the inner diploë. Anemias can potentially affect any bone of the skeleton that is involved in the production of red blood cells, but the most frequently affected bones are those of the cranium (figure 2).

Figure 2

Porotic hyperostosis is a condition that is generally seen on the cranial bones and is indicative of iron deficiency anemia

Porotic hyperostosis is a skeletal indicator of nutritional stress that has been extensively studied in archaeologic populations. Nearly all cases in North America seem to be due to iron deficiency, and the presence of low iron stores is likely to occur concomitantly with other health problems and nutritional deficiencies. Although these lesions can also be caused by hereditary hemolytic anemia and other disorders, iron deficiency is accepted as the primary cause of porotic hyperostosis for the vast majority of documented prehistoric cases.

Iron deficiency anemia appears to have been widespread and ubiquitous in most ancient populations in the New World. The general distribution of the lesion corresponds with increasing reliance on agricultural products such as maize, which are low in bioavailable iron. For example, Lallo and co-workers evaluated changes in rates of porotic hyperostosis for ancient Mississippians in Illinois living in the 12th century and found that its prevalence increased dramatically in the transition from hunting and gathering to agriculture. They suggested that this was due to an overreliance on maize in the diet and that the lesions were most pronounced in younger children because of diarrheal disease during weaning, combined with poor diet.

Infectious diseases

Infectious diseases are among the most significant selective forces in human evolution and, combined with under-nutrition, continue to be the largest contributor to morbidity and mortality worldwide. Although most infectious diseases leave no diagnostic markers, it is fortunate for paleopathologists that some affect the skeleton, changing the structure of bone tissue. The most frequent causes of infectious diseases in prehistory have been estimated to be common microorganisms such as staphylococcus and streptococcus, with conditions such as tuberculosis and venereal and nonvenereal syphilis relatively rare and more controversial to diagnose. The chronic (typically nonlethal) conditions are important to track at the community level because these illnesses perhaps shed the most light on everyday occurrences of poor diet, transmissible diseases, and the state of waste disposal and hygiene.

Osteomyelitis results from the introduction of pyogenic infection, and the skeletal response involves the periosteum, cortex, and medullary cavity. Osteitis is another form of this phenomenon, but the reaction is primarily localized within the cortical bone. Periostitis occurs when the reaction is restricted to the outer shaft, or periosteum. It can occur as a direct response to a skin infection, through trauma, through systemic bacterial invasions, or from other soft tissue infections. Diagnosis and identification of the cause of the infection are difficult, and paleopathologists have now advocated using general descriptive categories for classifying the skeletal changes observed. Referred to as nonspecific infectious lesions, the skeletal manifestations are categorized as periosteal reactions because most of the infectious conditions seen on prehistoric bones tend to fall in this category . Specific diagnoses are attempted by paleopathologists when there are lesions that seem to fit the pattern reported for treponemal or tubercular infections, although the number of these in pre-Columbian individuals is relatively rare.

Periosteal reactions can be seen clearly on this long bone and are indicative of some type of nonspecific infectious condition

Lallo and colleagues noted that the severity of periosteal reactions among Mississippian burials increased nearly fourfold during the period spanning the hunter-gatherer phase through intensive agriculture. The increase in infectious diseases in the intensive agriculturalists was thought to be related to increased population density and sedentary behavior, coupled with low dietary quality and overreliance on maize. Other trends in infectious diseases demonstrated that adult women had higher rates than did men and that individuals with infections died at an earlier age. Individuals had a high rate of co-occurrence of porotic hyperostosis and infections, suggesting that iron deficiency may have predisposed children to infectious diseases by lowering resistance.

Osteoarthritis

Osteoarthritis is among the oldest and most commonly known diseases that affect humans. Measuring the amount of arthritic involvement with skeletal remains is sometimes difficult because of the potentially large number of areas to be assessed (each vertebra and all joint systems) and the range of variation in bony response among individuals. Although many factors may contribute to the breakdown of skeletal tissue, the primary cause of osteoarthritis is related to biomechanical wear and tear and functional stress.Biomechanical stress is most apparent at the articular surfaces of long bone joint systems and is referred to as degenerative joint disease. There may be a relationship between such disease and other health problems. For example, a study correlating the incidence of degenerative joint disease and infection was undertaken for a Mississippian population from Illinois (AD 1000-1200). Individuals with multiple joint involvement demonstrated a statistically higher percentage of periosteal reactions. The prevalence of both infectious lesions and degenerative joint disease increased with age, and women demonstrated greater frequencies of disease in the shoulder and elbows than did age-matched men.

In general, early Native Americans appeared to sustain osteoarthritis at rates comparable with individuals today, although the earlier rate of onset and decreased life span of early Native Americans may have served to compress the observable cases into a shorter time frame within the life span. Much work in the area of osteologic correlates of occupational stress and weapon use suggest strong associations between lifestyle and patterns of osteoarthritic and other bone changes.

DEMOGRAPHY AND DISEASE AT CONTACT

There is wide agreement about the effects of diseases and epidemics associated with European contact. The first well-documented, widespread epidemic in what was to become New Mexico was smallpox in 1636. Shortly thereafter, measles entered the area, and many Pueblos lost as many as a quarter of their inhabitants. After the founding of Spanish settlements and missions, there was substantially more contact, and throughout the 17th century, epidemic disease was repeatedly imported.

Osteologic data demonstrate that native groups were most definitely not living in a pristine, disease-free environment before contact. Although New World indigenous disease was mostly of the chronic and episodic kind, Old World diseases were largely acute and epidemic. Different populations were affected at different times and suffered varying rates of mortality. Diseases such as treponemiasis and tuberculosis were already present in the New World, along with diseases such as tularemia, giardia, rabies, amebic dysentery, hepatitis, herpes, pertussis, and poliomyelitis, although the prevalence of almost all of these was probably low in any given group. Old World diseases that were not present in the Americas until contact include bubonic plague, measles, smallpox, mumps, chickenpox, influenza, cholera, diphtheria, typhus, malaria, leprosy, and yellow fever. Americas had no acquired immunity to these infectious diseases, and these diseases caused what Crosby referred to as “virgin soil epidemics,” in which all members of a population would be infected simultaneously.

It is important to look not only at the effects of specific events like epidemic outbreaks but also at longer-term processes that influence the age and mortality structure of populations. Kunitz and Euler stated that “one does not need to invoke large-scale dramatic epidemics; prosaic entities like malnutrition and infectious diarrhea are more than sufficient to do the job.” Neel likewise cautioned that, to understand the influence of introduced diseases on indigenous peoples, we must first know the longer history and “epidemiologic profile” of the populations. This points to the value of incorporating the information on precontact health as a precursor to understanding the effects of contact.