Natural experimental models: The global search for biomedical paradigms among traditional, modernizing, and modern populations

During the past four decades, biomedical scientists have slowly begun to re cognize the unique opportunities for studying biomedical processes, disease etiology, and mechanisms of pathogenesis in populations with unusual genet ic structures, physiological characteristics, focal endemic disease, or spe cial circumstances. Such populations greatly extend our research capabiliti es and provide a natural laboratory for studying relationships among biobeh avioral, genetic, and ecological processes that are involved in the develop ment of disease. The models presented illustrate three different types of n atural experiments: those occurring in traditionally living, modernizing, a nd modern populations. The examples are drawn from current research that in volves population mechanisms of adaptation among East African Turkana pasto ralists; a search for etiology and mechanisms of pathogenesis of an emergin g disease among the Yakut people of Siberia; and psychosocial stress, hyper tension, and cardiovascular disease in women working outside the home in Ne w York City and among subpopulations in Hawaii. The models in general, and the examples in specific, represent natural laboratories in which relativel y small intrapopulation differences and large interpopulation differences c an be used to evaluate health and disease outcomes.