Book Review: Morning has broken: ten years after the dawn of evolutionary medicine

Have you ever been confronted with the question: `Can evolutionary biology be of practical interest to mankind?' There are many possible examples you could give to support an af®rmative answer, but those relating to human health and well being will certainly be the most convincing. This is what this book is about and because of that it might be useful in convincing your layman neighbour of such a point of view. The authors argue forcefully for an evolutionary perspective on human diseases, with the aim of providing a deeper understanding of their proximate and ultimate causes and, in part, to offer avenues for improved treatments. The book is aimed not only at those people who want to learn more about an evolutionary approach to medicine, but also seeks to convince those who do not see humans as part of nature, and therefore not subject to the laws of biology. This Creationist type of thinking, which is still fairly common among medics, might have prevented previous generations from using evolutionary thinking as a tool in medicine. This aim deserves pursuit and this book may succeed in in ̄uencing the way medically quali®ed people think about their ®eld. Ten years after evolutionary medicine ®rst gained recognition (Williams & Nesse, 1991), the ®eld has found many applications. The book by Trevathan et al. covers many of them. The list of subjects, which are discussed over the 18 chapters and 469 pages, is long and themes cover many aspects of human biology and disease: neonatal jaundice, sudden infantdeathsyndrome,asthma, pathogen virulence, chronic degenerative diseases, substance abuse and addiction, incest avoidance, and nutrition, to name just a few. These topics are certainly of great public interest and therefore a wide readership may be expected even among nonscientists. Although this book may be entertaining to many people, it lacks the power to convince evolutionary biologists themselves about the critical need to apply evolutionary thinking to medicine. A leading theme in many chapters is the idea that most of humanness evolved during the Stone Age (about 200 000±10 000 years before present), i.e. when our ancestors lived as hunters and gatherers on wild food resources. Presumably, by the end of this period human beings were well-adapted stone agers and unprepared for the changing environment brought about by the rapidly spreading agricultural lifestyle. As a consequence, we supposedly still carry until today traits that were adaptive in pre-agricultural societies, but prove to be useless or even detrimental now. A convincing example illustrating this notion may be dental caries, which, according to palaeontological records, seems to have appeared only with the onset of the carbohydrate-rich diet of agricultural times. This hypothesis sounds compelling, but a closer inspection reveals that there is more to human nature than its evolutionary legacy from the Stone Age. Certainly the beginning of agriculture signi®es a major change in the human environment, but there were other environmental changes as well and every one of them might have had its consequences. The Stone Age argument relies heavily on the notion that evolutionary processes are too slow to lead to adaptations in 10 000 years. A number of examples indicate that this is not the case. For instance, the ability of the majority of mankind to digest milk (lactose tolerance) is believed to be an adaptation to the availability of milk as nourishment for adults after the domestication of wild stock. Likewise, the spread of certain resistance genes to infectious diseases is suggested to have occurred only after human settlements reached densities high enough for the disease agents to cause continuous problems (i.e. after the end of the Stone Age). On the other hand, the Stone Age was presumably long enough to allow for a generally well adapted human being to evolve. However, bipedalism and senescence are certainly older than the Stone Age, and problems related to them were not solved during the last half a million years. After all, Drosophila and Caenorhapditis elegans show senescence as well. Thus, there must be more to evolutionary medicine than just explanations based on the changes in human environment and life style. Some of the other likely reasons for the aforementioned problems, e.g. antagonisitc pleiotropy and recurrent deleterious mutations, are underrepresented in the discussions on evolutionary causes of diseases in this book. Much of the book does not come up to the expectations of an evolutionary biologist. Although many