BloodGenesMalaria - Blood, Genes, and Malaria (condensed...

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1 Blood, Genes, and Malaria (condensed version) Long before chemical antimalarials, we had evolved genetic ones to give us some protection – but at a price by Jared Diamond The headaches that I had been having for several days grew rapidly worse during my physiology lecture to UCLA medical students. By the end of the hour, it was painful to look at a light, and I felt as if knives were being pressed against my eyes from inside my skull. I barely got through the lecture, went out into the hall, vomited, and checked into a UCLA hospital bed. There I broke out in a sweat, pushed all the bedcovers off, then felt so cold that I pulled up the covers and two blankets, only to become hot and drenched in sweat again. My physician, who had drawn a sample of my blood, soon confirmed what I already suspected: I had malaria. I cursed my bad luck. If only I had been quicker at swatting those damned mosquitoes in New Guinea a few months ago, perhaps I wouldn’t be lying in a hospital in such absolute misery. A year later, I instead was feeling lucky. After seven more attacks of diminishing severity at intervals of 48 days, my malaria disappeared. I wasn’t stuck with it for life, as some people are, nor did I have to resort to dangerous and sometimes lethal drugs to eradicate it, as other people do. In another sense, though, I could still be called unlucky. Hundred of millions of people born where malaria is endemic belong to populations that have evolved a resistance to malaria. Because my ancestors came from malaria-free regions of Europe, I was genetically unprotected. Malaria is the world’s most important infectious disease, affecting more than a hundred million people each year. In some areas, it kills nearly 10% of the population in childhood. Today, those malaria victims who are lucky enough to share my access to modern medicine get treated, with varying success, with antimalarial drugs. Most victims, however, have to rely on their body’s own genetic antimalarials. Just as plant species native to regions with browsing mammals evolved many natural antibrowser defenses (such as sharp spines and toxic chemicals), so humans in malarial regions have evolved dozens of chemical defenses against malaria. Sickle-cell hemoglobin is probably the best-known genetic antimalarial. Like other such defenses, it provides some protection against one disease, while causing another – in this case, sickle-cell anemia. Taken collectively, genetic antimalarials constitute the commonest single-gene disorders in the world and are carried by more than 300 million people. In their paradoxical combination of protecting against one disease while causing another, they give us our best- understood paradigm for the origin of other, widespread genetic diseases. Genetic antimalarials also provide a paradigm of human
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This note was uploaded on 04/28/2011 for the course ANTH 150 taught by Professor Pietrusewsky during the Fall '10 term at University of Hawaii, Manoa.

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BloodGenesMalaria - Blood, Genes, and Malaria (condensed...

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