WHY WE GET SICK
The New Science of Darwinian Medicine
By Randolph M. Nesse, M.D., and
George C. Williams, PhD
Times 291pp $24
So many camps have co-opted the term "survival of the fittest" that Charles Darwin's theory of biological evolution has been distorted and obscured. One result is that many people erroneously believe that evolution refers to some force pushing us continually to improve, until we reach a healthy, perfected state. Another, as Randolph M. Nesse and George C. Williams spell out in Why We Get Sick, is that modern medicine has not adequately considered the biological origins of many maladies and consequently may be missing out on better strategies for treating them.
In enjoyable, if sometimes too breezy, form, the authors set the record straight: Evolution relies on random mutations that happen to confer superior reproductive fitness on individuals and so are incorporated into a species over many generations. But we're not likely to evolve dramatically longer lives, because the traits that help us grow and reproduce can be deleterious, too. For example, cell division, so necessary for growth, can backfire and become cancer. But cancer typically does not hit till we're past reproductive age, so mutations that help people avoid it aren't systematically passed on.
These realities can inform smarter approaches to some health problems. Doctors have long sought a treatment for morning sickness, for example. But some research suggests that morning sickness and food revulsion in pregnant women have evolved because they keep toxins away from the fetus. The authors believe doctors should try to learn what foods are dangerous before suppressing women's natural responses. Similarly, they suggest that fevers aren't just symptoms of infection but an evolved disease-fighting mechanism--so efforts to lower them may be misguided.
At times, the authors spin so many evolutionary threads at once that it's hard to sort through the tangle. But Why We Get Sick offers both a provocative challenge to medicine and a thoughtful discussion of how evolutionary theory applies to people.