Survival of the Sickest: A Medical Maverick Discovers Why We Need Disease is a most fascinating and entertaining book. In it, Dr. Sharon Moalem looks at disease through the lens of evolution, asking, "if evolution is all about survival, why would it select for deadly diseases?" He answers the question in breezy and inviting prose with plenty of science to back up his claims.

Dr. Moalem starts with the hereditary disease hemachromatosis, which produces excess iron in the blood and kills people in midlife if left untreated. He also looks at diabetes, high cholesterol, and favism (a hereditary and deadly intolerance of fava beans). He traces the diseases' history to see when they entered the gene pool and find out why such problems would remain. The answer: they protected against an immediate threat. About hemachromatosis he says, "Why would we select for a gene that will kill us through iron loading by the time we reach what is now middle age? Because it will protect us from a disease that is killing everyone else long before that" (p. 14).

From specific genetic diseases, Dr. Moalem moves on to infectious diseases like malaria and examines the relationship between humans and microbes. This chapter had a big "ewww!" factor for me, because I don't enjoy contemplating the fact that I am a host for more minute beasties than my own cells. However, the examination is interesting and well worth the read.

Dr. Moalem goes on to discuss such things as "jumping genes" (many genes are able to rearrange themselves as an editor might a manuscript), gene expression (genes can be turned on or off depending on the environment), and the utility of aging (cells that don't die become cancer). Throughout, he demonstrates a declaration he made in the introduction: "everything out there is influencing the evolution of everything else" (p. xv).

Dr. Moalem sometimes relies on controversial theories in his explanations, but he always declares them as such, and there are references at the end of the book for those who wish to follow up. A Ph.D. in human physiology, he appears to know what he's talking about and to be able to put it in layman's terms.

Survival is chock full of interesting stories and wonderful analogies and can be quite funny. In advising caution in the new scientific endeavor of changing gene expression, he says our genes are "engaged in a vast and complex dance that makes us who we are. We need to be awfully careful when we start to change the choreography, especially given our current lack of precision. When you try to move one dancer with a bulldozer, you're pretty darn certain to scoop up more than one Rockette" (p. 177).

Jonathan Prince, with whom Dr. Moalem wrote the book, was a senior adviser and speech writer in the Clinton administration and oversaw communications strategy with NATO during the war in Kosovo. One can't tell what contribution he made to the book, but I find it interesting that he was involved.

The emerging field of evolutionary genetics is something everyone should become literate in, given the pace of discoveries. Survival of the Sickest is a great introduction to the field and addition to the popular science literature. Read it, laugh, and learn.