Reviews
Survival of the Sickest: A Medical Maverick Discovers Why We Need Disease
by Sharon Moalem, M.D., with Jonathan Prince
William Morrow; 288 pages; $25.95
Reviewed by: Rebecca Walberg
Winnipeg Free Press
February 11, 2007
Survival of the Sickest: A Medical Maverick Discovers Why We Need Disease
What could persuade you to take a pill that’s guaranteed to kill you in 40 years?
This is the provocative question Canadian neurogeneticist Sharon Moalem uses to explore how and why many diseases have been part of human genetics for centuries or longer.
The answer is that the only reason to make a choice that will be fatal in the long term is if it enables survival in the short term.
Survival of the Sickest, which is being marketed as a kind of Freakonomics for health issues, is a readable and entertaining work of popular medical science.
The challenge of presenting difficult technical concepts in ways that the average reader can grasp has defeated many scientists, but Moalem, who teaches medicine in New York, touches upon genetics, evolution, biology and medicine without ever growing tedious or too complex.
Moalem first studied the mystery of genetic illness when his grandfather was diagnosed with hemochromatosis. Sufferers store excess iron in their blood that causes illness and eventually death. It is one of the most prevalent genetic diseases in people of European ancestry.
Traditional thinking about natural selection has been quite simple. Those who carry genes for good health and disease resistance live longer, and bear more children, thus leading to more people in the next generation with these strengths.
Any genetic disease that shortens life, especially if it kills before adulthood, should fairly quickly disappear from the gene pool, as stronger genes will be more successful.
What reason could there be, then, for a slow but lethal disease (uncurable until recently) to be part of the genetic code?
In order for a trait to be passed down through generations, it ought to bestow some advantage on its carriers. It is hard to understand why chromahematosis, a serious hereditary disease, hasn’t vanished by now.
But medical anthropology provides a fascinating theory about how this genetic default might at one point have helped its carriers to survive. During the plague of the 13th century, when a third of Europeans died, groups that had higher levels of iron were much more resistant to the Black Death.
Hemochromatosis led to death many years later, but enabled survival in the immediate future. People with this disease were more likely than others to survive the plague, and to bear children who also survived, and carried those genes.
Survival of the Sickest explores many other diseases, including diabetes and sickle cell anemia, as well as bacteria and parasites, in the course of showing that health and sickness are more complicated than they sometimes appear.
Moalem doesn’t look only at humans. The phenomenon of flavour, for example, is the result of plants seeking survival. Fruit-bearing plants reproduce by having their seeds consumed and then “recycled” by animals in the area. In order for this to work, a fruit must be sweet and attractive to animals.
The title is a bit misleading, though. Moalem is not arguing that we need disease, as such, but rather is showing that beneficial adaptations come with strings attached, and that some of our medical problems today exist because of vital benefits these diseases bestowed in the sometimes distant past.
The omnipresence of puns and thin jokes adds little to the book; the ideas and concepts are intriguing enough without these embellishments.
It is worth reading, if only for the discussion of race, medicine and heredity. Moalem demonstrates that skin colour is one of the least helpful ways, from a medical or scientific perspective, to classify humans.
Groups that evolved in very different climates, however, often share the genes for adaptations that enabled them to thrive under their specific conditions.
The research into HIV immunity carried out at the University of Manitoba, for instance, is an example of work that seeks to make beneficial adaptations of some groups available to all.
Rebecca Walberg is a Winnipeg writer.
© Winnipeg Free Press 2007. Reprinted with permission. http://www.freepress.mb.ca