Evolution’s Deadly Tradeoffs? Diseases That Can Kill Us May Also Save Lives And Increase IQ
What if you were told that diseases–even life threatening ones–can be a good thing, at least for some people
Is it possible that some of the maladies that plague us have helped humans survive and even thrive through evolutionary history?
Could it be that mutant genes may actually make endogamous populations ‘smarter’?
Consider sickle cell anemia, a genetic disease common to many American blacks and persons of West and Central African ancestry. It is characterized by severe anemia with symptoms of pallor, muscle cramps, weakness, and susceptibility to fatigue. Additional symptoms include heart enlargement, brain cell atrophy, and severe pain in the abdomen, back, head, and extremities (see diagram below). Many victims of sickle-cell anemia die before the age of twenty, though some survive past fifty. It’s an ugly list of maladies. Usually genetic disorders with such horrific consequences lead to the extinction of the ‘bad’ mutation-it ends up literally killing off all its carriers, so the faulty gene is not passed on to future generations.
So why is sickle cell still with us? Because like the mutations that cause a range of other disorders such as inflammatory bowel disease, psoriasis, Tay-Sachs disease and certain breast cancers, there are beneficial dimensions to these mutations. In the case of sickle cell, the gene has a beneficial aspect: it provides protection against malaria.
Evolution can be weird that way. The genes for some afflictions may actually have been preserved through Darwinian selection. The reason has to do with the specifics of each disease, but often is easily figured out, based on associations between various genes, the disease, and factors affecting aspects of biology not directly connected with the disease.
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