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Editorial

April 2007 | Volume 5 | Issue 4 | e112

I

t is curious that Charles Darwin,perhaps medicines most famousdropout, provided the impetus

for a subject that figures so rarely inmedical education. Indeed, even theiconic textbook example of evolutionantibiotic resistanceis rarelydescribed as evolution in relevantpapers published in medical journals[1]. Despite potentially valid reasonsfor this oversight (e.g., that authorsof papers in medical journals wouldregard the term as too general), itpropagates into the popular press whenthose papers are reported on, feedingthe wider perception of evolutions

irrelevance in general, and to medicinein particular [1]. Yet an understandingof how natural selection shapes

vulnerability to disease can providefundamental insights into medicineand health and is no less relevant thanan understanding of physiology orbiochemistry.

One reason that evolution doesntfigure prominently in the medicalcommunity is that although it makessense to have evolution taught as partof medicine, that doesnt make itessential. As explained at a meetingon evolution and medicine I recentlyattended in York, United Kingdom(the Society for the Study of HumanBiology and the Biosocial Societys 2006symposium, Medicine and Evolution),medicine is primarily focused onproblem-solving and proximatecausation, and ultimate explanationscan seem irrelevant to clinical practice.Crudely put, does a mechanic need tounderstand the origins, history, andtechnological advances that have goneinto the modern motor vehicle in order

to fix it?Randolph Nesse (University of

Michigan) and colleagues thinkotherwise [2], and have beencampaigning for evolution to berecognized and taught as a basicscience to all medical students (see alsothe Evolution and Medicine Network,http:www.evolutionandmedicine.org). It has been more than 10

years since he and George Williamspublished their classic book Why WeGet Sick: The New Science of Darwinian

Medicine[3]. Other landmark textslinking evolution to health have been

written since then, with new editions onthe way [46], and the research field isblossoming. Still, as Nesse mentionedat the start of the York meeting, thereare only a handful of medical schoolsin the United States and in the UnitedKingdom with an evolutionary biologistlisted as such on the faculty.

The most obvious examples ofevolutionary biologys importance tomedical understanding are related toinfectious disease [7]. As Jon Laman

(Erasmus University, The Netherlands)pointed out at the meeting, theimmune system provides the perfectplatform to explain the medicalrelevance of the exquisite evolutionaryrelationships between pathogensand their hosts. Understanding how

virulence evolves, for example, canhelp predict the potential, sometimescounterintuitive (and controversial)negative consequences of imperfect

vaccination [8,9]. But evolution canalso tell us that the origin of HIV

was precipitated by a jump acrossthe primate species barrier [10] andenables us to predict the imminentarrival of avian flu and the mutationsmost likely to be responsible for thatevolutionary leap from birds to humans[11]. Where epidemiological andpopulation genetic processes occur onthe same time scale, the emerging fieldof phylodyamics can also inform usabout the timing and progression ofpathogen adaptation more generally[12].

The relevance of evolution to

medicine is, however, much broader.Participants at the York meeting

Does Medicine without Evolution Make Sense?Catriona J. MacCallum

Citation:MacCallum CJ (2007) Does medicinewithout evolution make sense? PLoS Biol 5(4): e112.doi:10.1371/journal.pbio.0050112

Copyright: 2007 Catriona J. MacCallum. This isan open-access article distributed under the termsof the Creative Commons Attribution License,which permits unrestricted use, distribution, andreproduction in any medium, provided the originalauthor and source are credited.

Catriona J. MacCallum is Senior Editor at PLoS Biology.E-mail: cmaccallum@plos.org

doi:10.1371/journal.pbio.0050112.g001

Image: Nick D. Kim

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discussed not only how vulnerability tocancer is an inevitable but unfortunateconsequence of imperfect humanengineering and natural selection(Mel Greaves, Institute of CancerResearch, UK), but how life historytheory can potentially explain patternsof pregnancy loss (Virginia Vitzthum,Indiana University), how a comparative

approach applied to different humancultures and different primates canimprove rates of breastfeeding (HelenBall, University of Durham), whetherclinical depression has an adaptiveorigin (Lewis Wolpert, UniversityCollege London), and if suicideattempts are really just evolutionarybargaining chips in intense socialdisputes (Ed Hagen, HumboldtUniversity).

As with any emerging field, ideaschange and the science is challenged.

The thrifty gene concept [13]thatsome populations (e.g., from Polynesia)are particularly susceptible to type 2diabetes and heart disease becauseof past selection pressure specificallyduring times of famineno longerenjoys the support it once had [14].Tessa Pollard (University of Durham,UK) explained that the so-calledSyndrome X is now considered to bethe result of more general exposure toa rapid change in lifestyle as Westernsociety encroached on these populationsduring the mid-20th century. The

relationship between changingenvironment, diet, and susceptibility todisease, however, is also far from clear.Many diet-related conditions that typifyindustrialized populationse.g., obesity,hypertension, and tooth decayhavebeen explained as resulting from anevolutionary mismatch between ourover-refined, fat-filled contemporarydiet and the environment to whichhumans were once ideally adapted.Sarah Elton (Hull York Medical School,UK) cautioned that while this analogy

(the environment of evolutionaryadaptedness) has been useful as aresearch tool and has led to publichealth campaigns for better diets (moreseeds, nuts, fish oil, etc.), recreatingsuch a typical Stone Age diet as abenchmark can be misleading. Humanecology in the past was at least as

variable as human (and other primate)ecology is today.

Surprisingly, an evolutionaryframework to study human variation

can be seen as counterproductive.George Ellison (St. Georges MedicalSchool, UK) provided an example,although not concerning evolutionarymedicine, about a statistically flawedstudy leading to spurious conclusionsabout regional variation in IQ (whichI wont promulgate here). However,bad papers are published in all

subjects and are a failure of scientistsand the peer-review system, not thescience. These should not providean excuse to dismiss the relevanceof evolution to medicine (or to anyother life science). Even at a verybasic level, medical students can drawinsights from evolution they cannotobtain from other core sciences ontheir course. Paul OHiggins (Hull

York Medical School) noted that it ismuch easier for medics to learn thenerves involved in the brachial plexus

(the nerves supplying the arm) if theyfirst understand the origin of thepentadactyl limb.

It is not the case, however, that allclinicians fail to see the relevance ofevolution. Gillian Bentley (now atUniversity of Durham) conducteda series of interviews with leadingbiologists and clinicians when she wasbased at Imperial College London.

What was surprising was not the positiveendorsement of evolution by thegeneticists and evolutionary biologistsbut the enthusiasm of practicing

medical doctors for the topic, whetherinvolved in the active birth movementor dealing with major trauma inintensive care. Indeed, several localclinicians attended the York meetingand helped lead the discussions.

Ironically, the hardest task inadding evolutionary/Darwinianmedicine to medical curricula may

well be soliciting support from medicalstudents. Although Paul OHigginsthought a comparison of the brachialplexus to the pentadactyl limb was

helpful, not all his students agreedcomplaints were lodged that he wasforcing evolution on them. That lackof support was also reflected in theparticipation of only three medicalstudents at the York meeting (albeitenthusiastic ones), despite being widelypublicized. It is not clear whether thisis because medical students are moreoverburdened than most or because ofa more deep-rooted resistance to thesubject, reflecting wider political and

religious prejudice against evolution.But evolutionary medicine isnt andshouldnt be controversial, and thebest way to challenge prejudice isthrough education. As the oft-quotedTheodosius Dobzhansky wrote in 1973,Nothing in biology makes sense exceptin the light of evolution [15]. Thetime has clearly come for medicine

to explicitly integrate evolutionarybiology into its theoretical and practicalunderpinnings The medical studentsof Charles Darwins day did not havethe advantage of such a powerfulframework to inform their thinking;

we shouldnt deprive todays buddingmedical talent of the potential insightsto be gained at the intersection of thesetwo great disciplines.

Acknowledgments

I would like to thank Sarah Elton for inviting

me to attend the meeting in York, and SarahElton, Randolph Nesse, and Paul OHigginsfor comments on this article.

References

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Medicine needs evolution. Science 311: 1071.3. Nesse RM, Williams GC (1994) Why we get

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