Teaching
Evolution
&
The
Of
Nature
Science
PAUL FARBER
he famousgeneticistand co-founderof the modern
theory of evolution, Theodosius Dobzhansky,
publishedan articlein thisjournalin 1973 with the title
"Nothingin BiologyMakesSense Exceptin the Lightof
Evolution"(Dobzhansky, 1973). In that article he
responded to religious attacks on the theory and
defended its importance by noting how evolution
explainsthe enormousdiversityof life,its unity,and the
myriadempiricalfacts of biology.
What does Dobzhansky's dictum mean today?
Most biologists would say that Dobzhanskyhad it correct:The theory of evolution is the central organizing
theoryof the life sciences.The theory explainsthe facts
of biology,i.e., the theory tells us why the living world
appearsas it does. It gives us the answerto a numberof
interesting questions: Why do we observe so much
diversityof life (750,000 namedinsects, 170,000 dicots,
12,000 nematodes,and 18,000 bony fish, for example)?
PAUL FARBERis OregonState UniversityDistinguishedProfessorof
History of Science and Chair of the History Department, Oregon
State University,Corvallis, OR 97331. He holds a joint appointment with the Zoology Department. His e-mail address is
pfarber@orst.edu.
Giventhe vast amountof biodiversity,why are so many
chemicalpathways(e.g., the KrebsCycle) the same in
otherwise greatly different organisms?Why is DNA
found so widely as the geneticmaterial?Evolutionprovides for us an understanding.It also addresses questions like, Why do organismshave highly specialized
functions that permit them to live in hostile environments (hot springs), or in extraordinarilylimited environments(like the nematodePanagrellusredivivuswhich
lives in Germanbeer coasters)?Biologyis a trulyamazing subject,and evolutionhelps explainwhy.
The theory of evolution similarlyexplains biological relationships.Why do we observecomplex patterns
of distribution among plants and animals?Why do
some birdshave limitedrangeswhile others are cosmopolitan? The theory also relates bodies of scientific
information. Subjects of study that utilize different
methods, focus on differentorders of magnitude,conceive of naturein differenttime frames,or in different
spatialcategoriesareunifiedby the theoryof evolution.
Paleontology,biogeography,physiology, ecology, systematics,embryology,genetics, and cytologyare vastly
differentdisciplines.Unlikethe physicalsciences,which
arestill searchingfora plausibleunifyingtheory,the life
sciences have a single unifyingtheory that synthesizes
NATURE
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347
them all and brings them into relationshipwith one
another.Finally,the theoryof evolutionprovidesa powerfulguide to research.The questionsraisedby the theory havebeen extraordinarily
productivein the past 140
years.Much of 20th centurygeneticsgrew out of scientists' attempts to reconcile Darwin's theory with the
ideas on inheritancein his day.At presentthe theory of
evolution provides directionin bringingknowledge in
ecology to illuminatingproblems in paleontology;or
knowledge in genetics to shedding light on issues in
embryology,and suggestingnew paths of investigation.
The Teaching of Evolution in the
United States
The theoryof evolution,then, is impressive,productive, and important.To become a serious biologist,one
needs to havea graspof whatevolutionmeans,and to be
an informedcitizen, one should have a generalunderstanding of what the theory claims. People in most of
the modern,industrializedworldtakethatforgranted.It
is terriblyironic,however,that the United States,where
so much of the contemporarytheoryof evolutiondeveloped, has such an unsatisfactoryrecord of teachingit,
both in K-12and in post-secondaryeducation.
Consider the situation in K-12. The Thomas B.
FordhamFoundationpublishedin January,2000, Good
Science,Bad Science:TeachingEvolutionin the States
(Lerner,2000). The reportis unsettling.It reviewsand
evaluatesthe treatmentof evolutionby looking at state
science standardsstate by state. Statestandardsdo not
tell the full story,but by looking at them we can get a
reasonablybroad stroke picture of the situation. The
good news in the reportis that 31 of the states do an
adequateto excellentjob; the bad news is that 19 states
do a "weakto reprehensiblejob,"12 omit the word "evolution,"and fouromit teachingbiologicalevolutionaltogether. Since the report was issued there have been
some changes, most notably, the Kansas Board of
Educationhas reversedits scandalousdeletionof all references to biologicalevolutionin its standards.But the
story is far from over, and the opposition to teaching
evolution in the public schools continues to be a wellfinancedand powerfulforce.
The author of the report, Professor Lawrence
Lerner,explains that the opposition to the teachingof
evolutiondoes not come fromreservationsin the scientific communityaboutwhetheror not evolutionoccurs.
Yet,a significantnumberof Americansbelievethatboth
Creationand evolution should be taught in the public
schools, and the generalpublic is less than convincedin
the validityof evolution.Some people worry about the
moral effectsof teachingbiologicalevolution;and there
is a diversecoalition of young Farthers,Biblicalliteralists, intelligentdesign proponents,new age spiritualists,
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and others,who add up to a potent forcethat can influence state boards of education,and, just as important,
local school boards.
What emergesfromthe Fordhamreportis a picture
of a country that differsradicallyin its teachingof evolution from others in the modern industrializedworld.
Thereis less of a commitmentfor instructionon evolution, and if Dobzhanskyis correct,manyof the K-12students in the United Statesarenot receivingan adequate
preparationfor understandingthe life sciences.
What about post-secondaryeducation?The problems differfrom K-12but carryimplicationsfor them.
Colleges and universities,for the most part, teach evolution in biology courses. How they do it is another
issue. I find two main problems(which also are reflected in most major and non-majorbiology textbooks)
with the approachgenerallyused.
The first problem with what I shall call the "standard treatmentof evolution"is that it is taught as one
unit among a numberof others. In a typicalcourse we
arelikelyto find a sequencesomethinglike this:the cell,
genetics, evolution, animal/plant form and function,
and ecology.A few programsuse evolutionas an organizing principle.For the most part,however,evolutionis
just another topic. Studentshave to master the HardyWeinbergformulaand memorizedifferentformsof isolatingmechanisms;then they move on to anotherseemingly unrelated set of hurdles, like the nitrogen cycle
and the characteristicsof the biomes. Evolution,which
synthesizesthe disparatedisciplinesof the life sciences,
rarelyemergesin biology courses or texts as the unifying threadthat makes sense of all the material.
The second problem that concerns me with most
college teachingof evolutionhas to do with the organizationand presentationof the subjectmatter.Manyprograms and texts present evolution in the following
manner.The unit startswith some Pre-Darwinian
ideas
including:a brieflook at some earlynaturalistswho discussed change in time, such as the famous naturalists
Georges-LouisLeclerc, Comte de Buffon, and JeanBaptistede Lamarck,followedby some great figuresof
the past who, although they did not accept change in
time, nonetheless contributedto the accumulationof
knowledgethat made the "discovery"of evolutionpossible. CarlLinnaeusmakesa cameoappearancehere,as
well as GeorgesCuvier,the greatcomparativeanatomist
and paleontologist.
Next a shortbiographicalsketchof CharlesDarwin,
sometimes pointing out that he was not a particularly
promising universitystudent (perhaps to suggest that
students should not give up hope of becoming a useful
citizen someday,even if they get a "C"in the course),
and then, from Darwin'syouth to his voyage on the
H.M.S. Beagle, focusing on the GalapagosIslands with
their famous iguanas,tortoises,and finches.This is followed by a description of natural selection, the main
force of evolutionarychange accordingto Darwin,and
then an extensive treatmentof the "evidencefor evolution:"fossils, diversity,distribution,comparativeanatomy (adult and embryo),and finally,a case study in speciation-favoriteexamples include the Galapagosfinches, the Hawaiian Drosophila, or the cichlids of Lake
Victoria.The evidence for evolutionis intended to provide a compellingargumentfor acceptingevolution,i.e,
there is so much evidence for the theoryit must be correct, and, by implication,only an obscurantistor religious fanaticwould go againstall that evidence.
Afterestablishingthe validityof evolution,programs
elucidateevolutionarymechanisms:chiefly focusingon
populationgenetics (explainingthe implicationsof the
Hardy-Weinbergformula) and reproductivebarriers.
Finally,studentsare given a concludingwiz throughthe
recordof 700 millionyearsof life on Earth,with lots of
interestingphotos and even moreLatinnames.
What is wrong with this approach?There are two
majorproblemsthat concernme: the impressionit conveys and the opportunities it misses. Going from
Darwin,to a sketch of his centralidea of naturalselection, to a long list of evidencegives students the impression of a fortressmentality:Stakeout a claim,build an
intellectualfortressof evidenceto defend againstall oncomers, and pour boiling oil over the rampartson the
barbarianswho attack.As such, it can easilyappearnot
only dauntinglydogmatic,but also static.And, if combined with a couple of throw-awaylines on religion,the
approach can come off as threatening to students'
deeply held values, even if they do not subscribeto any
fundamentalistposition. More important, the typical
method of presentingevolutionmisses a greatopportunity to discuss the natureof science.
A caveatabout the natureof scienceis in orderhere.
Like many others, I think it is important that those
learningaboutevolutionbe given a broadersense of the
subject.Likewise,it is necessarythatthose teachingevolution (or any science) have an adequateconception of
the nature of science if they expect to teach their students effectively.It is pretty much a common sense
notion-you should know the general nature of what
you teach (Abd-El-Khalick,Bell, & Lederman, 1998;
AmericanAssociationfor the Advancementof Science,
1990, 1993; National Academy of Sciences, 1998).
Studentsand those preparingto be teachers,therefore,
should be taughtabout the natureof science.The problem, of course,is that scholarshavebeen grapplingwith
the subjectsince the earlypartof the 20th centurywithout achievingany consensus.It maynot be necessaryto
achieve total consensus on the matter,but many feel
that the currentlack of agreementundercutsattempts
to teach the subject.
Partof what makes uncoveringand explaining the
natureof science difficultlies in the diversityof the scientific enterpriseitself. Consider the list in Table 1 of
the sections of the American Association for the
Advancementof Sciencewhich includes physics, chemistry, geology, geography,engineering, biology, statistics, psychology,politicalscience, and linguistics. What
is it that holds togetherstatistics,the historicaldevelopment of the surfaceof Earth,classificationof plants, and
experimentationon the behaviorof rats?Even the individual sciences (take biology, for instance), encompass
a vast array of disciplines-as exemplified by the 78
member societies (and organizations)of the American
Institute of Biological Sciences which include people
who work at a rangeof activities:constructingcomputer models, givingnames to previouslyunknown lichens
of the rain forest, testing the physiological consequences of alterationsin diet, and elucidating the life
cycle of liverflukesin Africa.
Table1.
Sectionsof the AmericanAssociationforthe
Advancement
of Science
1. Agriculture,
Resources
Food,andRenewable
2. Anthropology
3. Astronomy
4. Atmospheric
andHydrospheric
Sciences
5. Biological
Sciences
6. Chemistry
7. Dentistry
8. Education
9. Engineering
inScienceandEngineering
10. General
Interest
11. Geology
andGeography
12. History
andPhilosophy
of Science
13. Industrial
ScienceandTechnology
14. Information,
andCommunication
Computing,
andLanguage
15. Linguistics
Science
16. Mathematics
Sciences
17. Medical
18. Neuroscience
19. Pharmaceutical
Sciences
20. Physics
21.
22.
23.
24.
Psychology
Social,
Economic,
andPolitical
Sciences
Societal
Impacts
ofScience
andEngineering
Statistics
NATURE
OFSCIENCE
349
A Case Study Approach
In spite of the perils of attemptingto construct a
model that captures the nature of science, we can,
nonetheless, make a number of useful observations
aboutthe contemporarynatureof scienceand aboutscientific inquiry.Teachingthe theory of evolution is an
invitationto do so. An effectiveway is to use a historical
case study approach,one thatfocuseson scientificproblems. Instructorspresent biology as a set of questions
that biologists are investigating,how those questions
came into existence, and what are currentlyproposed
answers.This perspectivestresses the lineages of questions that guide scientificresearch.
Evolution as a case study illustrates this well. In
such a treatment,one can startwith CharlesDarwinas
a young man and surveywhat constitutedthe world of
the life sciencesin his day.Studentslearnthat "biology"
was not a term widely used, and that what lay at the
heart of understandingthe living world was "natural
history."Naturalhistory'sgoals were to describeand to
classify the products of nature and to uncover the
underlyingorderin nature(Farber,2000). The tradition
in which Darwin worked had been establishedin the
centurybeforeby CarlLinnaeus,who popularizedand
pioneered a system of classifying and naming, and
Georges-LouisLeclerc,Comte de Buffon,who stressed
the importanceof extensiveobservationand arguedfor
a complete survey of the living world (by which he
meant external and internalcharacteristics,life stages,
geographicaldistribution,geographicalvariation,and
behavior). Naturalists believed that with sufficient
empiricalobservationsthey would someday penetrate
the veil of mysterythat shroudedthe living world, and
discern the orderin nature.
Between the founders of modern natural history
and the generation of naturalists to which Darwin
belonged, stood a majorrevisionof the naturalisttradition:the emergenceof comparativeanatomyas a serious
science. Combiningthe carefulanatomicalresearchtradition on the human body with extensivenew studies
on animals,a set of researchershoped to find the key to
understandingthe orderin natureby examiningstructure.The most well-knownproponentof this new discipline was Georges Cuvier of the Paris Museum of
NaturalHistory..He claimedthat his exhaustivedissections revealeda set of fundamentalbody plans. These
basic plans could be furthersubdividedinto subgroups
by using examinationof the structureof variousorgan
systems. What was importantabout the new comparative anatomywas Cuvier'sclaimthat each species could
be rigorouslydefined, and was morphologicallystable.
They could not change because the individual units
were so complex that any change would destroy their
functionalintegrity.
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When Darwin was a young man, comparative
anatomywas the queen of the life sciences.Comparative
anatomistswere uncoveringthe underlyingstructures
of animal form, and they regarded these underlying
structuresas the foundationfor classification.Systems
of classification,it was hoped, would mirrorthe orderin
nature.Enrichingthat picturewas the study of embryology. Of equal importance was the study of fossils
which revealedthat the structuresof extinctanimalsfollowed the same generalpatternsas living ones. Thatis,
the picturethat Cuvierconstructedapplied to living as
well as to extinct forms.
Darwin also lived at a time when the Industrial
Revolutionin Europewas leadingEuropeansto actively
colonize the globe. Nations sought new markets and
new raw materials,and in the explorationand exploitation of the world, Europeansuncoveredthousands of
new plants and animals.The materialcoming back to
the museums and collectionsin Europerevealedinteresting geographicalpatterns. Largeareas of the globe
seemed to have plants and animalsthat possessed family resemblances.Darwin's generation,therefore,was
heir to the largest collections ever assembled.His colleagues differed qualitativelyfrom earlier naturalists
because of the consequences of the Industrial
Revolution.Increasedleisure time, lower cost of printing, innovationsin the reproductionof illustrations,and
developmentof populareducationhad made it possible
for more people to work on naturalhistory than ever
before. This new, more professional,generation held
high standards,and they were in communicationwith
one another through such new genres as the monographand scientificarticle(Farber,1997).
Darwin'scontemporariespuzzled overa numberof
problems concerning their data. For one, naturalists
were amazedby the diversitythat existed. Beetles!Why
should God have createdso many beetles?You could
find a thousand differentspeciesjust in the areawhere
Darwin received his university education. Does God
have an inordinatefondness forbeetles (as a laterbiologist would quip?).Giventhat therewere so many different species on the planet, naturalistsasked where they
all had come from.One could imaginea Gardenof Eden
with a few hundred species;or Noah's arkwith several
thousandkinds, but naturalistswere uncoveringa staggeringnumberof life forms.Paleontologistscompounded the problemby showing that there were thousands,
perhapsmillions,of extinctformsthat formerlyinhabited Earth.Where had all the new species come from?
Why did all the old ones die off? What accounted for
the similarities we notice among different species,
among genera,etc.? On a practicallevel, what criteria
should we use in classifyingthem?
In additionto diversityand its origin(and the related issue of classification),the patterns of distribution
called out for some explanation.Why should Australian
animalstoday resembleAustraliananimalsof the past,
rather than the animals of other continents? Why
should plants on islands in the ocean resemblethose of
the closest continent?Why should plants at high altitudes resembleplantslivingat greatdistancesaway,but
at the same altitude?
When Darwinbeganhis momentousvoyageon the
H.M.S.Beagle,his contemporarieswereaskingthe above
questions, and it his hardly surprisingthat he found
himself asking the same ones on his journey. He discovered interesting fossils (e.g., armadillos) in South
Americathatresembledanimalsstill livingin the region,
and noted that similar animals and plants inhabited
adjacent territories.He noticed that the life on the
GalapagosresembledSouth Americanforms, but were
separatespecies.
AfterDarwinreturnedto Englandhe spent a number of years compiling his data and farmingit out to
experts for them to describe and to name. One of his
collaboratorsinformedhim that his collection of finches from the Galapagosconsisted of almost a dozen differentspecies. Anotherverifiedthat the fossil llama he
found in South Americarepresenteda differentspecies
than the ones found alivetheretoday.These novel findings reenforcedhis puzzlement over the leading questions in natural history.At some fairly early point in
these years after his return, Darwin realized that IF
species changed,if one species could give rise to another, then many of the centralproblemsthat he and other
naturalists confronted could be answered. But, how
could a species change?The comparativeanatomyof his
day suggested it could not happen. So he spent years
reading.He found earlierattemptsto establish change
in natureunconvincing.Buffonand Lamarckwere too
speculative.Darwinfelt that to be convincinghe had to
discover the mechanismresponsible for the change of
species. Why a mechanism?We do not know for sure,
but it certainlyseems that he had absorbedthe scientific ethos of the generationof naturaliststo which he
belonged.Theywanted the study of living organismsto
be a sciencelike the study of chemistryor physics.Since
the days of Newton, the physicalsciences had pursued
a vision of nature as a vast, complex machine.During
the 18th and 19th centuries the picture of nature
became more and more that of machine, like the
machinesdrivingthe IndustrialRevolutionthroughout
Western Europe. While Darwin was working on his
explanation of the origin of species, those studying
physiologywere discoveringthe workingsof the animal
and plant body-a series of physicaland chemicalmechanisms that explainednutrition,respiration,and other
biological functions. So, looking for a mechanism to
explain evolution was in keeping with the most
advancedscience of his day, and is a traditionthat still
characterizesa lot of what we do in the life sciences.
Finally,as we know from Darwin'sdiaryand notebooks, on September28, 1838 he read a work by the
Rev. Thomas Malthus on the consequences of overpopulation. In a flash he made a leap from the pressure that resulted from overpopulationto the notion
that in nature,since there was so much destructionof
life and so much variation, there must be a natural
selection operating that in time could modify the
descendants of a population (Browne, 1995, Mayr,
1972, Ruse, 1979).
It was a huge leap. He went from thinking of a
species as a blueprint-aunit rigorouslydefinedby comparativeanatomy-to a population of individuals. He
realizedthat individualswith variationsthat gave them
an adaptiveadvantagewere more likely to surviveand
reproduce,and that in time the process would give rise
to new species. Fossil forms resembled living forms
because they were directly or indirectly related.
Distributionpatternswere the traces of ancient movement of plants and animals.The resemblancesnoted in
classificationwerenot the resultof an abstractplan,but
the faintoutlines of common descent.
Noticewhatis happeningherepedagogically.Those
categoriesthat we usuallypresent as "evidencefor evolution" are presented as the problems that Darwin
solved (fossils, diversity, distribution, comparative
anatomy). These problems gave rise to the theory;
rather than being the bricks and mortar of a fortress
constructedafterthe theorywas conceived.By reorganizing the materialsthat are generallyused we can convey knowledgeof the theoryin a mannerthat avoidsthe
static "fortressmentality" and better illustrates the
natureof science.
Darwin'seuphoriaof discoverydid not last long, for
he realizedthat thereweremanyproblemswith his new
theory. So much so that he doubted if he could ever
convince anyone of it. This is not fortressscience;just
the opposite (more like ecosystem development,if we
need a differentmetaphor).Darwinworkedfor over 20
years before publishing his theory,for he knew that it
would be controversialand he knew that he had not
solved many of the problems that the theory faced. In
this regard,Darwinwas like other proponents of new,
revolutionarytheories.
What were some of the majorscientificproblems?
Firstoff, of course,was the issue raisedby comparative
anatomy-thatspecieswereso complexit was difficultto
fathom how they could change. Next, if the species
inhabiting Earth were the descendants of previous
species, then there would have to have been a vast
amount of variationin those earlierpopulationsto permit naturalselection to create new forms. Was there?
Wheredid it come from?Werethereforcesoperatingon
the productionof new variations?Closelyrelatedto the
issue of variationwas the concern about whether new
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351
variationcould be inherited.The study of inheritancein
Darwin'sday also posed the troublingobservationthat
characteristicsseemed to blend when they were inherited-a red floweringplant crossedwith a white flowering
plant often gaverise to a pink floweringplant. Or,if the
characteristicsdid not blend, then they seemed to
mix-the childrenin a family typicallyseemed to have
features resembling the father, some the mother.
Blendinginheritancesuggestedthat advantageousvariation, so importantfor Darwin,might get swamped in
successivegenerationsand thereforenot be acted upon
by naturalselection.
The problemsthat Darwinfacedwere real and serious. Not surprisingly,therefore,many scientists had
serious reservationsabout his theory when he published it in 1859, and a livelydebateensued.The debate,
however, stimulated a vast amount of significant
research.The researchdone on heredity,for example,
turned out to be of criticalimportancein biology,for it
led ultimately to the rediscoveryof "Mendel'sLaws"
(which had been completelyignored in Mendel'sday)
and to the developmentof modern genetics.
So, one set of problems,the ones Darwingrappled
with, led to a solution, Darwin's theory of evolution
based on naturalselection,which led to another set of
problems.The work on those problemsled to new solutions in genetics,and other subjects,and eventuallyto a
new theory of evolution (the Modern Synthesis that
was formulated by Theodosius Dobzhansky, Ernst
Mayr,GeorgeGaylordSimpson,JulianHuxley,Ledyard
Stebbins,and others beginningin the late 1930s). And,
of course,the new theoryraiseda host of new and exciting issues and questions.The lineage of problemscontinues, and when we teach this way students see how
fundamentalquestions are to science.
Religion
What about religion? Religion resides under the
surface in any discussion of evolution. Here, again, I
think an historicalapproachhelps greatly.In Darwin's
day many scientists and most educated people in the
English-speakingworld had grown up with the view
that the wonders of nature served as testimony to the
wisdom and power of God, the Creator.Darwin,however,had come to the view thatnaturalhistorywould be
more productiveif it severed its explicit ties with religion. That is, if scientific explanationdid not include
any referenceto the supernaturalabout which we have
no way of resolving disputes. Such was the case in
physics,chemistry,and recently,in Darwin'sday,geology. Not everyoneagreedwith that position.
We most often, however, read caricaturesof the
story: for example, accounts of the famous HuxleyWilberforcedebate at the 1860 BritishAssociationfor
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the Advancementof Science meeting where Darwin's
bulldog allegedlydefeatedand put down "SoapySam,"
the Bishopof Oxford.Whatis left out of this renditionis
the very serious considerationgiven to Darwin'sideas
by the religiousminded (cf. Livingstone,1987, Moore,
1979). Therewerea numberof theologianswho considered Darwin's theory a threat to received opinion.
CharlesHodge, for example,arguedthat by stressinga
deterministicuniverse,Darwinwas slipping into atheism. But other theologiansarguedthat Darwin'stheory
John Fiske,
opened the path for a renewedChristianity.
a leadingpopularizerof evolutionin America,made that
a centralargumentin his writings.Similarly,Asa Gray,
Darwin'schief scientificsupporterin the United States,
wrotea set of articlesshowinghow Darwincould be reconciled with traditionalChristianbeliefs (Gray,1963).
To Gray,Darwinhad shown howthe Creatoroperated.
Instead of what Gray took to be the commonly held
naive and crude belief that God had createdeverynew
species individually (think of all those beetles!),
Darwin'sOriginof Speciesgave a dynamicdimensionto
Creationand removedthe awkwardnessthe fossil and
geologicalrecordposed to men of faith.Fiske and Gray
werenot alone.BenjaminWarfield,foremostdefenderof
the theologicallyconservativedoctrineof the inerrancy
of the Bible was an evolutionist. One enthusiastic
Americanwritereven produceda book titled,TheGospel
to Darwinthat claimedthe Originwas the fifth
According
Gospel.It is not an overstatementto say that the majority of the Americanbiologistswho acceptedevolutionin
the late 19th centurydid not believeit posed any threat
to religion,but, quite the contrary,felt their religious
beliefswere strengthenedby it.
Now, the point is not to teachthe historyof religion
in biology classes,but ratherto brieflyconveythat there
aremanyways to interpretDarwin,and there are many
ways to reconcileevolutionwith religion.My experience
has been that once students see that, they realize that
evolutionis not the flame-breathing
dragonof atheism,
but a theory that explains biologicalphenomena, that
relatesbodies of information,and that guides research,
and like other aspectsof science,is open to manyphilosophical and religious interpretations.They have to
work out for themselveshow they want to view it. Butit
is not an either/or situation:science or religion.There
are a number of models of negotiatedrelationships(cf.
Miller,1999).
Nature of Science
So given this case-studyapproachto the theory of
evolution,which presents science as a lineage of questions, which sees Darwin'stheoryas a response to a set
of problemsin his day,andwhich sees Darwin'ssolution
as one thatraisednew questionswhich ultimatelyresulted in a new theory, how can we use it to exemplify
aspects of the nature of science?What generalizations
aboutthe natureof sciencemightwe be able to drawout
of our story?
One obvious generalizationis the dynamicnature
of science. Science changes through time. In Darwin's
case we see the basic concepts of biology redefined
(species, distribution,etc.) We also see a new interpretation of how to explain the facts of biology come into
being. The changing dimension of science needs to be
conveyedto studentswho too often aregiven a simplistic view that science consists of the "Truth"about
nature.This is not to say that we need get entangledin
a post-modernfree-for-all,
but merelyto make the point
that in science new questions emerge,new interpretations come into being, opinions, often long held, can be
revised.
Anotherimportantdimensionto understandingscience is its levels of generality.Althoughwe discuss facts,
hypotheses, laws, and theories, we often neglect to
point out in our science teachingat what level the material under considerationfalls, and the result can generate a lot of confusion.How, afterall, can we evaluatea
scientificclaim if we do not know the intended level of
generalization?Is the claim a fact (a well-confirmed
observationor empiricalstatement),a hypothesis(a calculated guess open to investigation),a law (a well-confirmed regularity,or, a definitionusually of a relationship thought to be invariableand universal),or a theory (a complex explanation,based on assumptionsand
definitions, that relates observations and bodies of
knowledge and guides research)?All have different
appropriatestrategiesfor evaluation.One uses observation for most facts and experimentsfor most hypotheses. Theories are evaluatedon how well they explain
and relate, and therefore are not "proved"or "disproved."They are inherently open-ended and always
have "problems"to be solved,which is a strength,not a
weakness.
The theory of evolution has to be presented as a
theory,and this is an invitationto discuss the levels of
generalityin science. It also permits us to circumvent
pseudo-arguments,like the alleged "scientific problems" of the theory which turn out to be areas of
research.The theory of evolution has problems. Yes;
they make the theory more interesting!Lookingat levels of generalitygives students a more sophisticated
frameworkwith which to judge claims, and permits
them to see how a theory like evolutioncan be considered "powerful"while being "unproved"and raising
serious questions.
Relatedto the issue of the level of generalityis the
level of certaintyin science. Sciencemakes some statements about the world that have a high degree of cer-
tainty,but science is not a monolithicenterprise.Some
of the claimsin sciencewe hold with a greatdeal of certainty:Mendel'slaws, the gas laws, for example.They
arehighlyconfirmed,and some of us would literallybet
our lives on them. Other claimsin science are less confidently held. The Big Bang theory explains a lot, but
one could imagine another theory replacing it given
new observationsor new discoveriesin physics. What
about evolution?Thatlife has changedon Earthis well
established and one could say with great confidence
that evolutionhas occurred.Some of the broaderclaims
of the theory, however,are held with less confidence,
and otherparts,for example,the evolutionaryhistoryof
individualgroups, such as Homosapiens,rest on slight
evidenceand are constantlybeing rethoughtin light of
new discoveries.
Scientificmethod?Thereis not, of course, a single
scientificmethod. Scientistsuse a number of methods
depending upon what questions or problems they are
tackling.In the case of evolution,biologistsuse different
methods to examinedifferentissues. Some of the work
is experimental,as in the investigationof the peppered
moths in Britain;some of the work is observationalor
comparative,as in paleontology,that continuallybroadens our understandingof past flora and fauna; and
finally,some of it consists of creativeintellectualconstructions,like Darwin making an analogy to human
populationgrowth to formulatethe concept of natural
selection.By paying attentionto the methods scientists
employ,we obtain a sense of the wide range of issues
that they can tackle.
Finally,science is alwaysdone in a specificcultural
context. Darwin's work took place in industrial
England. The vast amount of material pouring into
Europeanmuseums raised specific scientificproblems.
Competition was a fact of life, and the metaphors
Darwinemployedfit his day.Had he lived at a different
place or period he may well have framedhis ideas differently.
Dobzhanskypassionatelybelieved that the process
of evolution was fundamentalto an understandingof
biology.Today,his contentionis as valid as it was when
he made it more than a quarter of a century ago.
Moreover,the theoryof evolutioncan serveas an exemplar of how scientists examine the natural world
Biologyis not a body of facts to memorizebut a quest
towardsunderstanding,one that is ever changing and
one that has roots not only in the phenomena that we
observe,but in the human world that shapes our concerns and questions.If we can move the study of biology towardwhat excites biologists and away from what
makes students' eyes glaze over,we shall have accomplished an importantand valuabletask.
NATURE
OFSCIENCE
353
Acknowledgments
This articleis a writtenversionof a plenarysession
talkdeliveredat the 2001 AnnualMeetingof the National
AssociationforResearchin ScienceTeaching.Comments
by MarkLargent,Norm Lederman,MikeMix, and Ben
Mutschlerwerehelpfulin preparingthis article.
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