Abstract
BackgroundMedical and pre-professional health students ask questions about human health that can be answered in two ways, by giving proximate and evolutionary explanations. Proximate explanations, most common in textbooks and classes, describe the immediate scientifically known biological mechanisms of anatomical characteristics or physiological processes. These explanations are necessary but insufficient. They can be complemented with evolutionary explanations that describe the evolutionary processes and principles that have resulted in human biology we study today. The main goal of the science of Darwinian Medicine is to investigate human disease, disorders, and medical complications from an evolutionary perspective.DiscussionThis paper contrasts the differences between these two types of explanations by describing principles of natural selection that underlie medical questions. Thus, why is human birth complicated? Why does sickle cell anemia exist? Why do we show symptoms like fever, diarrhea, and coughing when we have infection? Why do we suffer from ubiquitous age-related diseases like arteriosclerosis, Alzheimer's and others? Why are chronic diseases like type II diabetes and obesity so prevalent in modern society? Why hasn't natural selection eliminated the genes that cause common genetic diseases like hemochromatosis, cystic fibrosis, Tay sachs, PKU and others?SummaryIn giving students evolutionary explanations professors should underscore principles of natural selection, since these can be generalized for the analysis of many medical questions. From a research perspective, natural selection seems central to leading hypotheses of obesity and type II diabetes and might very well explain the occurrence of certain common genetic diseases like cystic fibrosis, hemochromatosis, Tay sachs, Fragile X syndrome, G6PD and others because of their compensating advantages. Furthermore, armed with evolutionary explanations, health care professionals can bring practical benefits to patients by treating their symptoms of infection more specifically and judiciously. They might also help curtail the evolutionary arms race between pathogens and antibiotic defenses.
Highlights
Medical and pre-professional health students ask questions about human health that can be answered in two ways, by giving proximate and evolutionary explanations
Notwithstanding our knowledge, clear explanations of the evolutionary processes that underlie sickle-cell disease, balancing selection and heterozygote advantage, are still not found in many medical and pre-professional health texts leaving students needlessly wondering 'Why?' understanding these evolutionary processes would help students understand why genes underlying other hemotological disorders like alpha and beta thalassemias, Hemoglobin E (Hb E) syndrome, and Glucose-6-phosphate dehydrogenase (G6PD) deficiency are found at high frequencies in certain populations from the Mediterranean, African and/or South East Asia [14,15]
This is the central tenet of the science of Evolutionary Medicine: that principles of evolutionary theory can provide a unifying principle by which human biology, disease, and disorders can be understood [1,2]
Summary
Evolutionary explanations & natural selection Can our students benefit from such evolutionary explanations? Yes, we believe they can. Compensating advantages may maintain disease genes associated with diabetes Type I (reduced miscarriage when linked to the beneficial HLA DR3 gene [1,20]), Fragile X syndrome (increased fertility among heterozygous females [37] or prenatal advantages to offspring [38]), gout and hyperuricemia (beneficial antioxidant effects [39,40]) among other examples [1,2,6,20] Many such evolutionary hypotheses initially advanced a decade or more ago on the bases of observed biased inheritance patterns, or because of the commonness of the disorder and other circumstantial evidence, have not received rigorous scientific testing. It would be possible to determine the validity of the evolutionary hypotheses, and to clarify the proximate genetic and physiological mechanisms involved
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