Throughout chapter one, Dr.
Sharon Moalem discusses why humans would have evolved to have hemochromatosis. This
relates to Big Idea 1, the process of evolution drives the diversity and unity
of life, since Dr. Moalem has a theory that humans evolved to have
hemochromatosis written into the genetic code of the individuals who suffer
from the disease. On pages 15-18 Dr. Moalem continues to explain the benefits
of hemochromatosis in the past.
What is so bad about
iron-doesn’t the body need it to survive? Cite a source of how the iron rich
diets of today may cause similar problems to what hemochromatosis causes. Explain
why some human gene evolved to include the mutation that causes hemochromatosis
and relate it to natural selection. What mutation made hemochromatosis
beneficial? Why was this beneficial to people in the past? Is it still
beneficial today? Why or why not? How does bloodletting help relieve the
conditions of hemochromatosis?
(Lily Barghi lbarghi4@students.d125.org)
Like all other things in life, iron is good for us only in moderation. If we have too little iron in our bodies, we are at risk for iron-deficiency anemia, where our red blood cells don't work properly. On the other hand, if one has hemochromatosis, iron can build up to dangerous amounts and potentially lead to organ failure. What we don't realize is too little and too much iron can lead to very similar problems. As mentioned by Melissa Kaplan, "both iron deficiency and overload can cause symptoms all to familiar to most of us: fatigue, memory problems, and more" (http://www.anapsid.org/cnd/diffdx/irondisease.html).
ReplyDeleteIn ordinary people, macrophages are filled with iron. When these macrophages engulf an invader, the invader can feed off of that iron and use the lymphatic system to spread throughout the body. This is what happened with the bubonic plague. However, the people with hemochromatosis were usually unaffected by the plague. Why? Their macrophages lack iron and, therefore, the plague couldn't grow and spread throughout the body. Thus at the time of the Bubonic Plague, the gene for hemochromatosis was selected for as a favorable trait. This now leads into Big Idea 1, which states the process of evolution drives the diversity and unity of life. Since the selection pressures at the time, the Bubonic Plague, favored those with little iron in their macrophages, the population adapted to their environment and hemochromatosis became more prevalent among society. This allowed the population to survive and reproduce more easily, making it a selective advantage. Even though hemochromatosis untreated would kill a person by the time they were middle aged, it was better to live until then instead of dying sooner.
Hemochromatosis today can be beneficial to some extent. Because those with hemochromatosis lack iron in their macrophages, their immune systems can fight off many invaders. This can be very helpful, but one must also look at the effects of the disease itself, too.
Hemochromatosis is not harmful if caught and treated early. However, if not caught, serious problems can occur. For one, an excess of iron in the liver and other storage organs can interact with oxygen and produce free radicals that damage cells (http://www.anapsid.org/cnd/diffdx/irondisease.html). This can also eventually lead to organ failure, heart attack, cancer, and pancreatic damage.
Bloodletting is a practice that dates back to over three thousand years ago. Although discredited by many in the nineteenth century, it has proved to be an acceptable solution to those with hemochromatosis. As Moalem states, "regular bleeding of hemochromatosis patients reduces the iron in their systems to normal levels and prevents iron buildup" (18). Therefore bloodletting is advantageous especially to those with hemochromatosis.
(Posted by Lindsay Pontello, lpontel4@students.d125.org)