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For example: Sickle Cell Anemia and Evolution. Your name. Brief introduction of the disease. What is it? Where is it? How much of a problem is it?. Proximate Causation. The proximate cause of this disease is:. Evolutionary Question. For example:
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Brief introduction of the disease • What is it? • Where is it? • How much of a problem is it?
Proximate Causation • The proximate cause of this disease is:
Evolutionary Question • For example: • Why are genes for sickle cell so common, since they cause sickle cell anemia, a devastating disease? • Shouldn’t natural selection have removed the sickle cell allele from human populations?
Evolutionary Hypothesis • One possible answer to those questions: • Heterozygote advantage of the sickle cell allele in areas with malaria.
Explanation of Evolutionary Hypothesis • Heterozygote advantage in sickle cell might work like this… • This is an example of ______(for example, “Balancing Selection”, one of the categories of evolutionary medicine hypotheses from the class)
Predictions and evidence for this hypothesis • If the sickle cell trait provides a benefit in malaria, we should see higher numbers of people with the trait in places with malaria. • Evidence for sickle cell trait matches the distribution of malaria.
Alternative Hypotheses • Sickle cell is not adaptive – it has no benefit • This is not supported by evidence for survival of sickle cell heterozygotes in Africa. • Sickle cell is a sporadic mutation • This idea is not supported by the high frequency in the population, way higher than what is expected for sporadic mutation rates.
Significance • This hypothesis explains the epidemiology of this disease • Other gene polymorphisms that affect the red blood cell might also provide benefit in malaria.
