PubMed · 10306158
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A F Gonzalez. 1978. Flying doctors.. https://pubmed.ncbi.nlm.nih.gov/10306158/
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During the past four decades, biomedical scientists have slowly begun to recognize the unique opportunities for studying biomedical processes, disease etiology, and mechanisms of pathogenesis in populations with unusual genetic structures, physiological characteristics, focal endemic disease, or special circumstances. Such populations greatly extend our research capabilities and provide a natural laboratory for studying relationships among biobehavioral, genetic, and ecological processes that are involved in the development of disease. The models presented illustrate three different types of natural experiments: those occurring in traditionally living, modernizing, and modern populations. The examples are drawn from current research that involves population mechanisms of adaptation among East African Turkana pastoralists; a search for etiology and mechanisms of pathogenesis of an emerging disease among the Yakut people of Siberia; and psychosocial stress, hypertension, and cardiovascular disease in women working outside the home in New York City and among subpopulations in Hawaii. The models in general, and the examples in specific, represent natural laboratories in which relatively small intrapopulation differences and large interpopulation differences can be used to evaluate health and disease outcomes.
Ecologists still search for common principles that predict well-known responses of biological diversity to different factors. Such factors include the number of available niches in space, productivity, area, species' body size and habitat fragmentation. Here we show that all these patterns can arise from simple constraints on how organisms acquire resources in space. We use spatial scaling laws to describe how species of different sizes find food in patches of varying size and resource concentration. We then derive a mathematical rule for the minimum similarity in size of species that share these resources. This packing rule yields a theory of species diversity that predicts relations between diversity and productivity more effectively than previous models. Size and diversity patterns for locally coexisting East African grazing mammals and North American savanna plants strongly support these predictions. The theory also predicts relations between diversity and area and between diversity and habitat fragmentation. Thus, spatial scaling laws provide potentially unifying first principles that may explain many important patterns of species diversity.