The teaching of evolution-we need to do hetter

Education

The teaching of evolution-we need to do hetter

E

volutionar y processes provide

fune 1997

seilers. Finally, society continues to be plagued by persistent, aggressive attempts to eliminate evolutionary concepts frorn public education.

Books and subdisciplines I surveyed 50 major textbooks (see box page 386) in fields of biology tu which evolution, evolutionary dynamies, and the consequences of evolution are especially pertinent. For eaeh book, I checked the glossary and the index, and T read the parts in whieh evolution was discussed in detail. I define as "major textbooks" those that have an important share of the national market, hased on publishers' statements; those that are in a third or larer edition; or those that my colleagues recognize as commonly used textbooks. The 50 selected textbooks fall into six fjelds: evolution, general biology, ecology, genetics, paleontology, and systernatics. The reasons for selecting these fields as subjects to examine textbook treatment of evolution are as folIows: • Evolution. Books in this Held should provide the standard against which to judge textbooks in other fjelds because they are written bl' professional evolutionists. • General hiology. These textbooks, whieh are of crucial importance as pedagogic tools because they introduce students co the entire field of biologl', come in two categories, each senring a different audience. Those textbooks meant for biology majors form the basis of s)Jbsequent training in biology. By contrast, textbooks written for nonmajors provide a more general surycy of the biological world, for example, in the context of courses te ae hing "biology for poets". These books oftcn provide the onll' formal intro duc-

385

Downloaded from http://bioscience.oxfordjournals.org/ by guest on July 18, 2016

The presentation of evolution is important both within biology and philosophical framework for without. Biology is currendy one of thc study of life that Dohzhansky the most popular fields of academic (1973) was led to state forcefully study. At the University of Colorado that, " ... nothing in bioJogy makcs at Boulder, almost2000 undergradusense except in the light of evolu- ate students, or 10% of the und ertion." For chis enlightened perspec- graduate population, major in one civc to hc transmitted c1early to stu- of the two depanments whose purdenrs of biology, the teaching of view is biology (Environmental, evolution must begin wich an accu- Population, aod Organismic Biolrate definition and description oE the ogy aod Molecular, Cellular, and major features of cvolutionary pro- Devclopmental Biology). The same cesses and the possible outcomes of trend is true at other universities and such processes. However, a perusal colleges. The popularitl' of biology of SQme of the books most COlTI- probably reflects modern societal monly used as textbooks in college- challenges. Just as political science level courses indicates that these was a popular major in the world of books often provide a faulty or in- the 1950s, which was recovering complctc perspecrive of evolution. from World War II and facing the In chis article, I show how the Cold War, biology is a popular maconceptual framework of evolution jor in the world of the 19905, most of as a process is prescnted and devcl- whose scrious problems aod chaloped in those fjelds most elosely lenges-ranging from overpopulaassoeiated with evolutionary think- tion and 10ss of biodiversity to the ing. I intend this article as a eall to reemergenee of diseases and plagues readers of BioScience who are in- that have evolved resistance to antivolved in the teaehing of evolution biotics and pesticides-are biologiand re1ated fields. I do not intend it cal in nature. And just as many stuto be an exhaustive eompilation of dents of the 1950s did not become all books in all biological fjelds. political seientists, manl' students of Professional biologists invest sig- the 1990s will not become profesnifieant time in teaching, thinking sional biologists. Students seleet about, and investigating the complexi- these majors as a way of obtaining ties of biology in their evolutionary an education that addresses issues of contexts. Those of us who specialize broad societal relevanee. in the study of evolution and evoluOutside academia, the general tionary processes often assurne that public is also aware of thc relcvance we have sueeessfully eonveyed our of evolution to biologieal phenomeollective knowledge about evolution ena aod to publie health issues. As I to other professional eolleagues in write this ankle, for example, the biology. We also often assurne that New Yorker (7 Oetober 1996) has these eol1eagues, in turn, effeetively just published an essay about Dareommunieate that understanding to winian perspeetives in psl'chobiolstudents. A reasonable corollary of ogy, and Family Circle (Oetober these assumptions is that textbooks 1996) has an artide about renewed whose subjeet matter includcs evo- rhreats to public health by antibilution present the eoneept correctly. otic-resistant strains of several disease-causing bacteria. Moreover, Stephen J. Gould's compilations of by Yan B. Linhart evolutionary .vritings are often bestsuch a strong scientific and

Textbooks consulted for this analysis, arranged by fields

386

Although not all facets of ecology, genetics, paleontülogy, and systematics need to he conspicuously evolutionary in their focus, the over-

BioScience Val. 47 No. 6


Evoluti o n Furuyma ( 1986), Evolutionary Bio/ogy Pricc ( t 996), Bio/ogical Evolution Ridley (1993), EI/olutioll Strickberger ( 1996), Evolution Bio logy (for majors) Arms und Camp (1995), Bio/ogy Carnpbell ( 1993), Biology Ravcn and Johnson (1986 ), Bio/ogy Solomon, Be rg, Martin, and Villcc ( 1993 ), Biology Starr and Taggart ( 1995), BioJogy: Thc Unity and D;vcrsity 01 Lire ßiology (for nonmajors ) Bernstein aod Bernstein ( 1996), Bi%gy Campbell, Mitchcll, and Reese ( 1994), Biology: Concepts and Connections MadeT (198B), Inquiry /nto Lire Mix, Farber, aod King (1996), Biology: Thc Netrvork of Life Posrlcrhwair and Hopson (1992), Tbe Nalllre of Lire Wallace ( 1992), Bi%gy: Tbc World o( Lire Ecology Begon, Harpcr, and Townscnd (1996), te%gy: Individuals, Populations, and Comnllmities Brewer (1994), Tbc Scienee of Ee%gy Colinvaux (1993), Ecology 2 Kormondy (1996), C01leepts of Eeolog)' Krebs ( 1994), Ee%gy R;cklcfs ( 19901. Ecology Smith (1996), Eeolog)' and Field Bi%g)' Stiling ( 1996), Ee%g)': Tbeories and App/ieatio1/S Gcnctics Griffiths, Miller, Suzuki, Lewontin, :md Gclbarr ( 1993), All Imrodl/etion 10 Genetie Anal)'sis Harrl ( 1994), Geneties Lcwin ( 1994), Genes V Klug and Cummings ( 1996), Essemials of Geneties Russcll (1996), Genetics Tamarin ( 1996), PrincilJ/es of Geneties Paleo ntology Cowen (1990), History of Life Lane ( 1986), Life ill tbc Post Nicld and Tucker ( 1985), Pa/eonto/og)': All Introduction Raup and Sranlcy ( 1978), PrincilJ/es of Pa/eont%g)' Stcarn and Carroll ( 1996), Pafeomology: Tbe Record of Life Zicglcr ( 1983), Illtrodl/etion to I'afaeobi%gy: Genera/ Pa/aeollt%g)' Systcmatics Duellman and Trucb (1986), Bio/ogy of Amphibia1/S Elzing:J ( 1987), Fllndamenta/s of Entom%g)' Evans ( 1984), t1lseCl: A Textbook of Entom%g)' Gi ll (1990), Omitholog)' Gi llorr ( 1995), Enlom%gy Mayr ( 1969), Prillciples of Systematie Zo%gy Radford (1986), Fundamemals of Pfam Systematies Ross, Ross, and Ross ( 199 1), A Textbook of Entom%gy Siv:Jrajan :Jnd Robson (199 1), Illtroductioll to the Principles of Nant Taxonomy Stacc ( 1989), l'Ialll Taxonomy and ßiosystematies Srucssy ( 1990), Plant Taxmlom)': The Systematie Evaluation of ComlJarative Data Wclty ( t 982), The Life of Birds Woodland ( 1991 I, COlltemporary l'Iant Systematics Van Tyne and Bergcr (1976), FlIndame1lta/s of Omithology Vaughan ( 1986), Mammalogy

tion ro evolutionary biology that most poets and orher nonmajors ever receive. • Ecology. This field is concerned wirh the study of the interactions betwecn organisms "nd theit environments, and it is prccisely thesc interactions that have the potential to genera te evolutionary change. Hence, ecology is relevant as rhe setting, or context (sensu Hutchinson's [1965J Fcolagical Theater and the Evnlutianary Play) , within which evolution takes placc. In addition, it is the results of evoJunonary processes (hat help explain many ccological phenomena, such as adaptive radiation, characrcr convergence, and displacemenr, r versus K selection, and coevolurionary interactions. • Genetics. This field describes mcchanisric processes of evolutionary change, which involve the storage of hereditary information, irs patterns of transmission hetween generations, and dynamics of evolutionarv change. I examined only rhose text·bOüks whose goal was to provide a general introduction to, and overvie\\-" of, geneties. Books whosc foCHS involvcs specific subficlds of genetics, such as deveJopmental or molecular genetics, are not expected to address evolutionary issues. • Paleontology. This field is relevant ro evolution because it deals with tht' srudy of fossi( forms of life, their evolutionary hisrory, classification, and ecology. Because the vast majority of species that have ever existed on Earth are represented only in the fossil record, and because fossil phylogenies lllustrare macroevolutian, paleontology provides a COIltext in which to analyze historical aspects of evolution. • Systematics. This field deals with the study üf evolutionary relationships among species, the principles and procedures undcrlying thc classification or taxonomy of these speeies) aud the origin of new species via evolutionary processes. Simply pur, systematics is "the study of the kinds and diversicy of organisms and any and alt rchHionships among them" (Simpson 1961),

all subjecc matter in these fields contributes significantly to an accurate understanding of processes of evolutionary change and the contcxts in which such change occurs. The converse is also true: an evolutionarv perspeetive is necessary to obtain a~ understanding of the subjecc matter of these disciplines.

Evolution: what it is and wh at it is not

June 1997

evolution "the eore theme of biology" (1993, p. 11). Both Starr and Taggart (1995) and Arms and Camp (1995) begin with abrief chapter that describes evolution. Textbooks for nonmajors are more variable in the perspective they provide. With The survey and the exception of Mader (1988), all its implications of those examined emphasize in theif The results of the survey (Table 1) introductory chapters that evolution are illuminating but disappointingj is of paramount importance in bioltextbooks in several fields fall short ogy and provide a glossary definition of the baseline definition. The prob- of evolution . .lust one (Postlethwair lems are diverse. Some textbooks and Hopson 1992) defines evolution equate evolution with natural selec- as evolution textbooks da (Table 1); tion or adaptation. Others, although thc orherseither equate evolution with providing a reasonable definition in natural selection or imply that (he the strictest sense, do not provide process of evolutionary change necesenough details abom cvolutionary sarily leads to increased adaptation processes. For example, same defi- and increased complexity (Table 1). nitions of evolution provide variaEcology texts are surprisingly intions on Darwin's perspective of complete: three of the seven textde.">cent with modification. This ap- books (Begon et al. 1996, Colinvaux proach is reasonable but imprecise 1993, and Kormondy 1996) provide bccause it leaves out the genetic no formal definition of evolution in mechanisms involved. Converse!y, a their glossaries and give it litde atdefinition often used in genetics (i.e., tention in the text. Begon et a1. (1996) "changes in allele frequencies over do address coevolution in several time") is too stark if presenred alone, contexts and the role of natural secspecially because the concept of lection in evolution (in two pages), evolution is often introduced in the and they describe brieHy convergent early chapters of general biology text- evolution and genetic polymorphism. books, before the concept of "allele Colinvaux (1993) addresses the role frequencies" is even inrroduced. of evolution in the context of locoEvolution textbooks generally motion (cows versus kangaroos), the present the perspective on evolution Red Queen hypothesis (adaption is a that is captured by the baseline defi- fleeting attribute, and constant nition. Tha t is, rhev stress that evo- change is needed to keep up with lution involves a variety of processes variable environments), and the gc(e.g., mutation, migration, and se- ography of evolutionary (i.e., biolection) and that evolution can in- geographic) regions; each ropic is volve undirected generic change covercd in a few paragraphs. through time. In addition, these text- Kormondy (1996) discusses evolubooks c1early state that evolution is tion in five pages thar cover Darwin, not synonymous with selection, the voyage of the Beagle, and the progress, or adaptation (e.g., Strick- Hawaiian lslands. By contrast, berger 1996, pp. 62, 427, 512, 515; Ricklefs (1990) devotes 6 of 36 chapFutuyma 1986, pp. 8, 16,369-371; ters to evolutionary ecology; two Price 1996, pp. 52-54; Ridley 1993, other chapters are tirled "Evolution, pp. 8, 325, 326). social behavior and population reguAmong general biology textbooks, lation" and "Adaptations to the those that are written for srudents physical environment." The other ecolmajoring in biology provide a per- ogy textbooks are variahle in their spective on evolution that is compa- treatments of evolution, providing rable to that found in evolution text- brief definitions (Table 1) with modbooks-that is, they ler thc students est coverage of the topic in the text. know immediately that evolution Generic."> textbooks are highly provides the unifying framcwork of variable in their treatments of evolubiology. Für example, Raven and tion. Ofthe six textbooks consulted, Johnson say that "Evolution i5 the only two (RusseIl 1996 and Klug essence of the study of biology" and Cummins 1996) provide a defi(1986, p. 14), and Campbell calls nition comparable co that found in 387


To eompare texthook definitions of evolution, ir is best to ~tart with a descriptive baseline definition thar is inrended not co be comprehensive bm rather to represent some of thc issues that need ro bc addressed when discussing what evolution i5 and is not. Evolution is said to have oeeurred within a specjes, lineage, or population when measurable dunges in various morphologieal, physiological, hehavioral, or biochemieal eha racteristics can be detected. These characteristics must be at least pard}' under genetic conrrol. The genetic change(s) can occur as a consequence of processes such as migration, mutation, genetic drift or bottleneek, natural selection, and nonrandom mating. Genetie changes within different populations of a species can lead to differences among lineages, and sometimes tO the origin of new spccies. (More detailed discussiollS of the major features of evolution can be fouod In textbooks, such as Futuyma [19861 and Strickberger l J 996}; in a collection of essays about the central role of evolmion in biology [Moore 1984]; and in a compendium of keywords in evolutionary biology IKel1er and Lloyd 19921.) An introduction to the concept of evolution should also clearly emphasize what evolution is not, or at least avoid misleading implications. Evolution is not a synonym of natural selection. Nor is evolution a process that leads inevitably to increased or improved ada ptation, or to greater reproductivc success. Evolution does not imply a progressively doser fit between a population and its environment. Finally, evolution does not involve predictable 01' irrevocable change from simple to more COTIlplex forms or coward some sort of pcrfection. Nlercifully, iliustrations of evolution Llsing "rrees of life" with

somc ill-defined pond SCllm at the base and Atlas at the apex have been shruggcd off by most textbook writers, but subde variations on that theme must be guarded against.

Table 1. Definitions of evolution provided in texrbooks in several fields of biology.ln a11 cases, rhe definitions are exact quores from specific pages of the refetenced texts. Field

Definition

Referenee

Evolution

In a broad sense, the origin of entities pussessing different states oE olle or more char