Abstract
While much of evolutionary psychology seeks to understand why human behavior is adaptive, this book is concerned with the extent to which we are not well-adapted to our current environment. Ill health in most cases represents some actual or potential loss of evolutionary fitness. However, as the authors of this book point out, we have evolved to maximize reproduction rather than survival, and this is sometimes at the cost of our short-term health. Evolutionary medicine seeks to understand sickness in evolutionary terms.
This discipline has seen tremendous growth in the last 20 years. It is now part of the curriculum of many medical schools and there are numerous university courses. There is even an evolutionary medicine module developed by the National Institutes of Health for high schools. Evolutionary medicine has an odd status. In an ultimate sense, nothing makes sense in medicine except in the light of evolution. However, a practicing physician may seldom need to directly apply evolutionary reasoning in their diagnoses. For example, the current epidemic of obesity in the US may ultimately derive from the fact that our Pleistocene ancestors were at a selective advantage when eating ad lib. However, this fact does not necessarily guide the treatment of the condition. The evolution of antibiotic resistance is perhaps the one exception. It is important to understand some of the principles of natural selection to try to counter microbial resistance. The literature in evolutionary medicine is growing quickly, but because of the essentially multidisciplinary nature it is rather dispersed. The book under review makes a great contribution as a textbook that collects much of the core information in one place.
Principles of Evolutionary Medicine is aimed at all members of the medical profession, from doctors to students and allied health professionals so that they can “gain a more complete understanding of the processes that shape the human condition” (p. xii). The first six chapters provide an introduction to evolutionary theory. These chapters are aimed at about the same level as a freshman college textbook. The last chapter in the section discusses human phylogeny at some length.
The central four chapters take up four “illustrative axes” (p. xv), namely human reproduction, nutrition, metabolism and social organization. Basic biology is presented followed by evolutionary interpretations. The level remains at about that of a freshman undergraduate and I am concerned if my doctor needs this level of presentation. There is a welcome emphasis on the whole human lifespan and on health in the context of age and aging. The authors view senescence more as an adaptive trade off than an inevitable deterioration.
The coevolutionary war between parasites and hosts does not receive the attention I would expect. The section on virulence takes a very static view that virulence and resistance are fixed variables. The final chapter provides a slightly more dynamic perspective. I was entertained that speculations by others were often qualified by statements that the ideas were untested. The authors' own wilder ideas did not have the same caveats.
The last two chapters extract principles to develop a general framework for evolutionary medicine. I enjoyed the section in which the authors make a list of the eight ways in which we are not adapted. The list includes, for example, the costs of heterozygote superiority and the negative byproducts of sexual competition. However, the first item on the list is the proposition that that the environment in which we now live bears little relationship to that before the coming of agriculture and we are deleteriously out of sync with current conditions. I accept that lactose intolerance reflects a species that did not consume milk past lactation. However, for a misplaced hunter gatherer, I think I do a pretty good job at driving a car and on a good day can even fill out an income tax form. It would be good if there was some theoretical framework to decide when and where we are likely to show maladaptive behavior. In addition, I was frustrated by the lack of citations in Principles of Evolutionary Medicine. Many interesting and new ideas are presented in the text, but there is no way to find the author(s) or the original source. Instead, there is a list of 10–20 books of further reading at the end of each chapter. These readings vary considerably in their depth and complexity and in a couple of cases include books that would not be understood by most readers (citations are given in the figure legends).
I am ambivalent about Principles of Evolutionary Medicine. It synthesizes a lot of information. However, the authors feel obliged to review basic information on evolution and human biology which, I hope, the intended audience in the medical profession would know already. For those interested in getting the flavor of evolutionary medicine, I would still recommend Why we get sick, by Nesse and Williams (1994), which incidentally has a much better system of citation.