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Science 4 September 2009: |
Medicine: Evolutionary Biology for Doctors
The reviewer is at the Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
E-mail: [email protected]
In his 1870 address to medical students at University College,London, Thomas Huxley—already known as “Darwin’s bulldog”and fast becoming the most important voice in Britain on allpolicy questions regarding science and education—did notmention evolution even once. In fact, far from suggesting theinclusion of evolution in medical curricula, he advocated removingunnecessary topics, including his own beloved field of comparativeanatomy. There was simply too much information medical studentsneeded to absorb from the crucial areas of physiology, pathology,and pharmacology for broad topics such as evolutionary biologyto be covered.
In 2009, the 150th anniversary of the publication of On the Origin of Species, evolutionary biology is still trying to earn a place in medical education. The core competencies recommended by a recent joint committee of the Association of American Medical Colleges and the Howard Hughes Medical Institute on the scientific knowledge required by future physicians include an understanding of evolution by natural selection (1). At an April meeting, “Evolution in Health and Medicine,” sponsored by the National Academy of Sciences and the Institute of Medicine, a panel of deans and faculty from leading medical schools around the world endorsed the incorporation of evolutionary principles in medical curricula (2). And yet one can probably count on the digits of a three-toed sloth the number of medical schools currently offering such instruction.
Part of the problem is still the crowded medical curriculum that Huxley recognized. But in the era of genomics and proteonomics, this no longer seems an adequate excuse. More problematic may be the lack of appropriately skilled faculty members to teach evolutionary principles and the lack of appropriate materials from which to teach. In the 14 years since Randolph Nesse and George Williams published Why We Get Sick (3), a number of books devoted to Darwinian medicine have appeared. But they have either been edited compendia of recent research that assume an understanding of evolution or popular reads for a lay public. Principles of Evolutionary Medicine, by Peter Gluckman, Alan Beedle, and MarkHanson (authorities on the developmental origins of health anddisease), is the first specifically designed as a textbook appropriatefor medical students and medical schools, and it succeeds brilliantly.
For the rest of this review, see http://www.sciencemag.org/cgi/content/short/325/5945/1207 (paid content)
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This is to let readers know that Gluckman et al’s Section 6.3 on Hominin evolution contains inaccuracies. For example, the reader is informed that Lucy was discovered by the Leakeys in Olduvai Gorge (p. 125). Lucy was found by Donald Johanson in Hadar, Ethiopia.
Thank you for pointing out the error – we will correct in the reprinting
On page 225 in “Principles of Evolutionary Medicine,” by Gluckman, Beedle, and Hanson, there is a discussion of suborganismic selection in the immune system. The description of thymic selection is not accurate in several respects, the most important and easily addressed of which are delineated below.
First, it is implied that all immunological discrimination is established in the thymus, which ignores the multiple molecules, cells, and processes other than thymocytes and peripheral T cells that contribute to discrimination between self and non-self. For example, B cells responding to so-called thymus-independent, or TI, antigens should be regarded as discriminating between self and non-self without necessary participation by T cells.
Second, the claim that each T cell receptor (TCR) recognizes just one epitope is incorrect and highly unlikely for biological reasons as well as virtually inconceivable for biophysical reasons. In fact, although TCRs can display impressive degrees of molecular discrimination, they have been documented in numerous studies to exhibit considerable cross-reactivity in recognizing both MHC molecules and peptides.
Third, it is stated that T cell precursors undergo apoptosis in the thymus unless they fail to react to the repertoire of self antigens presented on other thymic cells. This claim differs substantially from the version of events currently accepted by immunologists. The selection of T lineage cells in the thymus is in fact a two-stage process. First, T cell precursors undergo “positive selection” in the thymic cortex. In this process, only T cells that do effectively recognize a complex of self-MHC plus self-peptide are rescued from apoptosis (i.e., the opposite of what is claimed by Gluckman et al.). Subsequently, the developing T cells are subjected to the process of “negative selection” in the thymic medulla, in which T cells that too strongly recognize a complex of self-MHC plus self-peptide are deleted by apoptosis.
Dr Greenspan
Thank you for the helpful comment. We will review that section in the forthcoming reprint of the book.