THE EVOLUTIONARY BASIS OF DISEASE By
Sanjana Rao Esther J Beck
A phlebotomy, or the act of ‘blood letting’, was a common treatment for most illnesses in medieval times, as it was believed that the withdrawal of blood from the patient would help balance their humors and cure them. This practice, said to be the most common treatment used in Europe, was relatively commonly used until the beginning of the 19th century. Modern medicine has since dismissed the practice as pseudoscience, however, there is at least one disease that it does effectively treat: Haemochromatosis. Haemochromatosis is an inherited condition where your body absorbs too much iron, leading to excess iron buildup in your organs. This can have
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potentially fatal effects, leading to liver disease, heart problems, and diabetes, and patients often suffer from joint pain and fatigue. Those afflicted with this condition often unknowingly treat their disease by becoming blood donors, using phlebotomies to get rid of the excess iron in their body and alleviate their symptoms. Nearly 6% of individuals of Caucasian descent carry or are afflicted with the inheritable form of haemochromatosis. But how did it arise and become so prevalent? Natural selection, or the survival of the fittest, is the idea that traits that make an organism better adapted to their environment are more likely to be passed on and therefore increase in prevalence
in a population. Individuals with traits that increase their ‘fitness’ survive longer or have a reproductive advantage, leading to more individuals with that trait. These traits arise via mutations, which lead to altered phenotypes. The mutation that leads to hereditary haemochromatosis is found in the HFE gene, and is called C282Y. So what evolutionary benefit could a mutation that results in excess iron uptake give us? There are at least two possible explanations. The first is that it is a ‘thrifty’ mutation, allowing our ancestors to make the most of the resources available to them. During the time this mutation that leads to hemochromatosis is hypothesized to have arisen, the northern Euro-
