Genetics: a Mixed Curse?
Did you ever get only one chapter into a book and realize at once that it deserves to be shared? That just happened to me yesterday. The book is "Survival of the Sickest," which I checked out of the library along with two others a little earlier this month. The author, Dr. Sharon Moalem, became fascinated by genetic disease -- specifically, the persistence of hereditary genetic diseases. If such diseases are bad, and in many cases kill their victims, why do they persist? To find out the answer to that question, one must turn to evolution and environment.
What moved me to write about this now was that first chapter, where he hits you with one of the most counter intuitive examples I've ever seen. The disease in question, hemochromatosis, causes excess iron to build up in the body in various organs. Untreated, its victims literally rust to death in middle age. As it turns out, though, the one place that iron *doesn't* get to in a sufferer's body is the white blood cells called macrophages. These are the same blood cells that transport infectious disease-causing agents to the lymph nodes. Now, what you need to know here is that most living things, including bacteria (*especially* bacteria, it seems) have a thing for iron. So the macrophages in someone who suffers from hemochromatosis not only tackle nasty bacteria; they starve it on the way to the lymph nodes. It's like a one-two punch.
Now let's get a little history into the act (hey, I majored in history). The Black Death swept through Western Europe starting in 1347, killing about 25 million people in that first outbreak; I've seen estimates saying that at the time, this was half the population of the area. It struck down people in their prime, especially healthy young men -- the kinds of folks we'd expect to have lots of iron in their system. Hemochromatosis have lots of iron in their system, too; but remember, infectious agents can't get to that iron. So those sufferers actually had a better chance of surviving the Black Death and passing their genes (including the disease) on to their progeny.
Remember what I said about the disease killing its victims in middle age if it isn't treated? As it turns out, it's quite treatable. The most effective treatment, in fact, has been around for thousands of years -- and was thoroughly discredited by the beginning of the twentieth century. Lately, though, the medical establishment has been taking a second look at it. Give yourself a gold star if you guessed the treatment was bloodletting. Dr. Moalem noted that his grandfather suffered from the disease, but they didn't know this until he reached his seventies. How did the man survive so long? He gave blood, diligently -- and felt *physically* better every time. With that kind of reinforcement, it's no wonder it became a lifelong habit.
I can hardly wait to see what else I learn from this book. Anyone have any other cool books to share?
What moved me to write about this now was that first chapter, where he hits you with one of the most counter intuitive examples I've ever seen. The disease in question, hemochromatosis, causes excess iron to build up in the body in various organs. Untreated, its victims literally rust to death in middle age. As it turns out, though, the one place that iron *doesn't* get to in a sufferer's body is the white blood cells called macrophages. These are the same blood cells that transport infectious disease-causing agents to the lymph nodes. Now, what you need to know here is that most living things, including bacteria (*especially* bacteria, it seems) have a thing for iron. So the macrophages in someone who suffers from hemochromatosis not only tackle nasty bacteria; they starve it on the way to the lymph nodes. It's like a one-two punch.
Now let's get a little history into the act (hey, I majored in history). The Black Death swept through Western Europe starting in 1347, killing about 25 million people in that first outbreak; I've seen estimates saying that at the time, this was half the population of the area. It struck down people in their prime, especially healthy young men -- the kinds of folks we'd expect to have lots of iron in their system. Hemochromatosis have lots of iron in their system, too; but remember, infectious agents can't get to that iron. So those sufferers actually had a better chance of surviving the Black Death and passing their genes (including the disease) on to their progeny.
Remember what I said about the disease killing its victims in middle age if it isn't treated? As it turns out, it's quite treatable. The most effective treatment, in fact, has been around for thousands of years -- and was thoroughly discredited by the beginning of the twentieth century. Lately, though, the medical establishment has been taking a second look at it. Give yourself a gold star if you guessed the treatment was bloodletting. Dr. Moalem noted that his grandfather suffered from the disease, but they didn't know this until he reached his seventies. How did the man survive so long? He gave blood, diligently -- and felt *physically* better every time. With that kind of reinforcement, it's no wonder it became a lifelong habit.
I can hardly wait to see what else I learn from this book. Anyone have any other cool books to share?