This paper examines the biological and evolutionary relationship among sickle cell anemia, malaria, and African-Americans. Beginning with a definition and description of sickle cell anemia — its causes, types, and complications — the paper traces how the sickle cell gene may have developed as a survival mechanism in malaria-endemic regions of Africa. Drawing on scientific studies, the paper argues that natural selection favored individuals carrying one sickle cell gene, as they demonstrated greater resistance to malaria while avoiding the severe complications faced by those carrying two copies of the gene. The paper also considers how this evolutionary dynamic is already shifting within African-American populations in the United States as malaria is no longer an environmental pressure.
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There is a compelling biological relationship among African-Americans, malaria, and sickle cell anemia. Many people born in regions affected by malaria are resistant to the disease. Malaria, rampant in parts of Africa south of the Sahara, has killed millions of people — many of them young children. Closer examination reveals that those who are resistant to the disease carry at least one sickle cell trait. African-Americans whose ancestors hail from Africa show a higher incidence of sickle cell disease. Are African-Americans who carry the abnormal gene proof of natural selection at work — allowing those with the trait to survive while those without it perished? This paper explores the link between the sickle cell gene and its apparent protective effect against malaria, as well as the connection between African-Americans and their African ancestors.
Sickle cell anemia was originally discovered by Linus Pauling in 1949. It is a red blood cell disorder that can be passed down from generation to generation. The disease takes its name from the shape of the affected red blood cells, which resemble the curved blade of a sickle used to cut wheat. Infected cells also become sticky and hard. By contrast, a person without the disease has red blood cells that are round and flexible, roughly resembling a doughnut in shape.
Sickle cell anemia is caused by changes in hemoglobin, a substance found inside red blood cells whose primary function is to carry oxygen. A small modification in this substance causes long rods to form within the cell when it releases oxygen, giving the cell its characteristic sickle shape.
Sickle cell is an inherited disease — children acquire it from parents who either have the disease or carry the trait. Sickle cell anemia is not contagious. It is most prevalent among African-Americans, Greeks, Latin Americans, Italians, Indians, and Arabs. However, cases have been recorded in other groups, including whites. No one is entirely immune, and everyone should consider being tested.
The three most common types of sickle cell disease in America are:
1. Hemoglobin SS, or sickle cell anemia
2. Hemoglobin SC disease
3. Hemoglobin sickle beta-thalassemia
While there are some differences among these three types, none is less painful than the others. Regardless of type, all patients can experience serious complications, including leg ulcers, kidney damage, strokes, bone damage, increased susceptibility to infections, and delayed growth. To manage the disease, patients typically employ a combination of strategies: increasing folic acid intake, staying well hydrated, avoiding extreme temperatures, and limiting excess physical exertion and stress.
Approximately one out of every 400 African-Americans has sickle cell anemia, meaning that roughly 8% of African-Americans carry the sickle cell trait. However, sickle cell is not exclusively an African-American issue. Scientists have concluded that sickle cell is a gene mutation that may have developed as a defensive mechanism against malaria, and research has shown that those with the trait have a higher-than-average survival rate in malaria-infected regions compared with those who do not carry it.
"Describes malaria transmission and global death toll"
"Evidence that sickle cell gene resists malaria"
It appears that the sickle cell trait was not solely formed to be a barrier against malaria as originally thought. However, natural selection has shaped populations in affected regions such that those carrying the abnormal trait enjoy longer lives than those who do not. The prevailing pattern has been that individuals with one sickle cell gene outlive both those with two sickle cell genes (who die from disease complications) and those with no sickle cell gene (who are more vulnerable to malaria). Extending this logic further, if malaria were ever fully eradicated, the selective pressure maintaining the sickle cell trait would disappear, and over time the trait itself would diminish in the population — a further demonstration of natural selection in action.
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