An interesting book with some new and some old examples of evolutionary traits that have persisted to help protect us from disease despite causing problems at other times. However it is written in a very popular style that American readers seem to like but I found a bit childish and annoying.
This book follows the trend of someone with a huge amount of specialised knowledge teaming up with a professional writer who can present the ideas in a breezy accessible style (think Freakonomics and you get the idea). In this case, the theme is evolution and how it impacts on humans and the organisms who share our bodies. Why, for instance, do severe illnesses keep getting passed down, when they seem to put their carriers at an evolutionary disadvantage? Moalem provides compelling evidence for thinking that this might not always be the case, hence the title. There is more to the book than that, but it makes an intriguing starting point for what follows. I was particularly interested in the short section on childbirth and why it is so difficult for humans, but every chapter was full of fascinating information presented in a way that a non-scientist like myself can readily understand.
We're used to thinking of disease as the enemy, as a malicious force that makes our lives shorter and more miserable. That may be exactly what "disease" is on an individual basis--but its value to the species as a whole is a different matter.
Dr. Moalem elegantly explains why medical conditions that are deemed to be diseases today often helped our ancestors survive and reproduce in difficult environments. Take hemochromatosis, a hereditary condition that causes iron to accumulate in a person's internal organs, eventually leading to death. Although the gene that causes hemochromatosis was once thought to be rare, research completed in 1996 found that it's actually surprisingly common. Why wouldn't such a terrible disease have been "bred out" of our species long ago? The answer is that hemochromatosis reduces the amount of iron available to iron-loving bacteria, such as the bubonic plague that depopulated Europe in the mid-1300s. A person living in the Middle Ages with the hemochromatosis gene would have eventually died from iron build up, but in the meantime would have have had a smaller chance of dying from the plague and other iron-loving infections--in an age when few people lived past the age of 50, the disease resistance conferred by hemochromatosis far outweighed the disadvantage that would have materialized if the person carrying the gene had lived to old age. People with hemochromatosis reproduced and passed the gene one to their heirs; those without it died of the plague, without children.
"Survival of the Sickest" is filled with similarly surprising observations. Anemia may be the body's way of reducing iron available to bacteria--giving an iron supplement to a malnourished population may be a bad idea and ironically (so to speak) medical bloodletting may not have been such a bad idea. Type II diabetes may have been a condition that conferred an advantage on northern Eurpoeans during the ice age, when an increase in sugar in the bloodstream and frequent urination would have reduced the risk of freezing to death. Similarly, sickle cell anemia offers protection from malaria. In the "good old days," a genetic condition that kept a person from dying before reproducing would have been a boon, even if the condition would have turned killer if the person managed to reach old age.
The book is filled with other "big ideas, briefly discussed." Instead of battling bacteria with antibiotics (which is only making them tougher), perhaps we could manage their evolution so that they thrive by inconveniencing their host (like a cold) instead of by flooring it (like malaria). And, although Dr. Moalem seems to agree that natural selection is the big driver of evolution, he observes that perhaps Lamarck wasn't so far off after all--jumping genes, retroviruses and methylation all suggest that an organism's life experiences can in certain circumstances affect future generations. As for aging--perhaps our bodies are designed by natural selection to limit the number of times a cell can reproduce (thus insuring that we will all die from old age if something else doesn't get us first), the alternative being an excess of cells without such a limit (in other words, cancer).
On the whole, "Survival of the Sickest" is readable, surprising and filled with "ah-ha!" moments. If you enjoyed "The Tipping Point" or "Freakonomics," you'll probably be intrigued by Dr. Maolem's often counter-intuitive observations.
We really don't "need" disease. This is a bit misleading. It just so happens that some genetic disorders, such as sickle-cell anemia, favism, diabetes, hemochromatosis, the tendency to obesity, etc., confer on the afflicted compensatory advantages. Thus a predilection for getting fat is adaptive if a drought or a long winter beckons, or a person with a genetic tendency toward sickle-cell anemia is less likely to get malaria, and so on. Note that it is only diseases caused by genetic mutations that Dr. Moalem is talking about.
One of the techniques our bodies use when fighting infection is to reduce the amount of iron available to the invaders. Bacteria need iron to reproduce. If there is a lot of it available their numbers can grow quickly. Without iron they can't reproduce at all. Iron is a limiting factor for many kinds of life. Vast stretches of ocean support little in the way of life because the microorganisms that begin the food chain can't grow where there is so little iron. As Dr. Moalem reports in this wide-ranging and eyebrow-lifting book, sprinkle some iron onto those patches of ocean and they will quickly turn green with microorganisms.
So it is a bit of an irony that people who have hemochromatosis, a genetic disorder that causes them to retain large amounts of iron in their bodies, are able to survival infections like the plague. This is because they starve the invading microbes through "iron locking." They have a lot of iron in their bodies, but they keep it away from the bacteria. Other people who have low levels of iron in their bodies are able to withstand bacterial attacks because they also keep what little iron they have away from the germs. In fact, one of the body's initial responses to microbial invasion is to limit the amount of free iron in the system.
Genetic coding for levels of iron in the body is an example of evolutionary adaptation, part of the ongoing arms race between us and the microbes that live in and on our bodies. This is just one of several interesting and new ideas coming from the growing science of evolutionary medicine that I found in Survival of the Sickest. Incidentally, one way to manage hemochromatosis is through donating blood on a regular basis, which explains in part why physicians of old were sometimes successful when they bled their patients.
This got me to thinking about "only women bleed" which led me to think about hemorrhoids (which prove that it isn't only women who bleed). Perhaps bleeding instead of retaining blood, which seems like the more natural thing for our bodies to do, has adaptive value in some people in some environments.
Another interesting idea is this from page 58: "ACHOO syndrome--its full name is autosomal dominant compelling heliopthalmic outburst syndrome." It is a "disorder that causes uncontrolled sneezing when someone is exposed to bright light, usually sunlight, after being in the dark." Dr. Moalem suggests that "way back when our ancestors spent more time in caves, this reflex helped them to clear out any molds or microbes that might have lodged in their noses or upper respiratory tract." Now this may sound a bit far fetched, but I have suffered from low grade allergies all my life, and used to have asthmatic attacks. I came to believe that the buildup in my lungs and the sneezing were signals to me to move on! Of course now I clean and vacuum like a germaphobe, but the idea is the same. My symptoms were adaptive. They more or less forced me to reduce the level of potential irritants and microbes in my environment.
But there is more. I noticed long ago that sometimes the sun in the morning would cause me to sneeze. I never figured out why until I read the above from Dr. Moalem. I am just the kind of person who would need to sneeze those molds out.
Later on in the book Moalem returns to an evolutionary idea that has been kicking around for decades. Beginning with the work of Elaine Morgan from the 1970s the public became aware of the notion that we humans had an aquatic past. She got the idea from marine biologist Alister Hardy. Through such books as The Descent of Woman (1972) and The Aquatic Ape: A Theory of Human Evolution (1982) Morgan argued that some of our unusual adaptations came about because we had an aquatic past. Taking up the idea, Moalem writes, "Every hairless mammal is aquatic or at least plays in the mud--think of hippos, elephants and the African warthog. But there aren't any hairless primates." (p. 198) Furthermore we have fat directly under our skin to help keep us warm just as aquatic mammals do. Also, Moalem notes, "the ability to survive on land and sea" gives us adaptive flexibility. If "chased by a leopard, the semiaquatic ape could dive into the water; chased by a crocodile, it could run into the forest." (p. 199)
These ideas are familiar but what I didn't know was that an aquatic past could have figured in our evolution toward bipedalism. "[S]tanding upright in water allowed...[aquatic apes] to venture into deeper water and still breathe, and the water helped to support their upper bodies, making it easier to support them on two feet." (p. 199)
This is an easy to read book, aimed at a general readership. An earlier, slightly more technical book that covers some of the same territory is Why We Get Sick: The New Science of Darwinian Medicine (1994) by Randolph M. Nesse and George C. Williams, which I also recommend.
I picked this up in Borders in Miami and read it before I came home. Not an obvious holiday read but absolutely fascinating to a kinesiologist (even complementary therapists ready stuff like this!).
It provides a really interesting perspective on how the diseases which plague us now actually helped our ancestors survive and there is a salutary warning about the link between too much iron in a person's bloodstream and Alzheimer's Disease. A touch of anaemia may not always be a bad thing!
It is written in a very easy style and flows very well. If you have any interest in health or medicine, read it!
I found this book really interesting. With very little science knowledge but an interest in diseases affecting us, it is really interesting to find out some of the background behind modern day diseases and why they exist in the first place. Not written in a scientific way just really easy to pick up and read a few chapters at a time
This is a book with countless deeply interesting facts about biology. After reading it I feel that I have a much much stronger grasp on how evolution works. However if you want to read something that will help you with your biology classes this isn't it. You will only gain generic knowledge, the kind of which will entertain a group of friends during a dinner party. All in all this is a extremely interesting book that mainly consists of a collection of unbelievable facts about biology, not a textbook. You will go through it as easily as if it was a Agatha Christie!