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PhilosophyandEthicsof

MolecularBiology

Lecture3Dr.SamuelSchindler

CenterforScienceStudies

DepartmentofPhysicsandAstronomy

AarhusUniversity

1

Preliminaries

Explainvs.

assess

Queries:good!

Reminderforpresenters:

Handouttotutor24hrsbeforepresentation!

Printoutthehandouts

SeealsoAULAondesignofhandouts

2

Preliminaries

Newseminarinstructions

Inadditiontorequiredtext,readonepresentation

text(assignmentinseminars)

Identifyoneargument (informally)and/orcome

upwithaquestion forthepresenters

Seminarbehaviour/workethics

3

Todaystopic

Thephenomenonofaltruism

Units/levelsofselection

R.Dawkinsview:theunitofselectionisnot

theorganismbutthegene

AttacksonDawkinsview

4

Recall Thetheoryofevolution;twobasicprinciples

Variation (individualdifferences)

Naturalselection(limitedfoodresources,competition,environmentalchanges,etc.)

Traditionalunitsofselection: Theindividualorganism(cf.Darwin1859/

standardview!)

Groups ofindividuals(e.g.K.Lorentz)

Entirespecies(S.J.Gould)

5

Darwinsview

InDarwinsview,naturalselection

operatesonindividuals

E.g.fastantelopes

Intheancestralpopulationtherewas

varietyofantelopeswithdifferentspeeds

Yet,theslowoneswereweededoutby

predators

Onlythefastonessurvived(and

procreated)

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Darwinsview

Problem

with

this

picture:

altruism

Someanimalssacrificethemselvestosavethemembersoftheirgroup/species

Examples:bees stingingintruders(killsthemselves);birds givingalarmcalls(focusingthepredatorsattentiononthem)

Note:iftheindividualistheunitofselection,whywouldtheindividualsacrificeitselfforotherindividuals?

7

Darwinsview

Darwin

suggested

that

altruism

makes

sensefromtheevolutionaryperspectivebecauseitsavesgroups ofindividuals

Otherdefenders:Konrad Lorentz

Note:thisisinconsistent withhisoverallviewthatselectionworksonindividuals,ratherthangroups!

Thelatteristhestandardview

Infact,thestandardviewrendersaltruismevenunlikely.

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Individualismandaltruism

Supposethat

agroupconsistsofindividualswhoregularly

exhibitaltruisticbehaviortowardstheirgroup

peers

thereareonlyfewegoisticindividualsinthose

groups

thealtruistic/egoistic traitisinherited

Then

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Individualismandaltruism

Theegoisticindividualshaveaselective

advantageoveraltruisticonesinthatgroup:

Theycanbenefitfromthealtruisticbehavioroftheir

peerswithout havingtoexposethemselvestorisks

Becauseegoisticbehaviorisadvantageousinthe

survivalofthefittest,overtime,altruismwill

disappearinthosegroups

Hence,evenifaltruismdoesoccasionallyoccur,it

isgoingtoselectedagainstbyevolution!

10

Individualismand

altruism

theoptions:

1. Altruisticbehaviorisachimera

Optionadoptedbymanybiologists/theoristsof

evolution

2. Altruisticbehaviorisrealandneedstobe

explained

whatwellfocusonhere

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Puzzle:

Howcanweaccommodatealtruism

onthetheoryofevolution?

RichardDawkinsanswer:

Wecandothatbymakinggenes,not

organisms,theunitofselection

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RichardDawkins

Dawkins:The

Selfish

Gene

Published1976

Earlycareer:zoologist

ProfessorforPublicUnderstanding

ofScienceatOxford(19952008)

Otherpublications

Theblindwatchmaker

TheGodillusion

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Theselfishgene

From

the

perspective

of

the

genes

eye,

altruism

makesperfectlysense:

Individualssacrificethemselvesinordertosavethegroupbecause

Thesurvivalchanceofparticulargenes (thattheindividualshareswiththegroup)isincreased!

Afteranattackerhasbeenfoughtoffandthegroupsavedbyanindividual:

thegenefrequencyinthegenepoolisincreased(attheexpenseoftheorganism)

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Furtherreasonswhythegene

shouldbetheunitofselection.

1. JunkDNAmakesnosenseonthestandard

viewofevolution(w/individuals=units)

2. Onlygeneshavetherightcharacteristics

requiredbythetheoryofevolution

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Furtherreasons(1)

Anotherargumentagainsttheindividual

organismasunitofselection

Theexistenceofnoncoding/junkDNA:98%of

ourgenome!

Fromtheperspectiveoftheorganism

since

junk

DNA

has

no

function

for

the

organism/species thereisnogoodexplanation

forwhyorganismsshouldkeepinheritingjunk

DNA

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Furtherreasons

(1)

Ongeneeyeview(p.44/45)

ThetruepurposeofDNAisnotthebuildingof

organisms(inwhichtheyreside)

Rather:thesolepurposeofDNAisittosurvive!

JunkDNAisparasitic;itisaharmlessbutuseless

passenger,hitchingaride!

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Furtherreasons

(2)

Theunitofselectionmust

havelotsofcopies

Otherwise:smallchanceofsurvival

havethepotentialtosurviveforasignificant

periodofevolutionarytime(>longevity)

Neitherorganisms,norspecieshavethe

secondcharacteristic

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Furtherreasons(2)

Each

individual

is

unique.

You

cannot

get

evolutionbyselectingbetweenentitieswhenthereisonlyonecopyofeachentity!

Eachindividualhasveryspecificcharacteristics: e.g.onlyoneleg

Sexualreproductionisnotreplication.(34)

Weinheritonly50%ofourgeneticmaterialtoourprogeny

Afterafewgenerations: hardlyanyproportioninyourdescendantsofwhatmadeYOU

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Furtherreasons(2)

Individualsare

not

stable

things,

they

are

fleeting.genesareforever(35)

Genesare(normally)notdividedwhenpassed

fromonegenerationtothenext

Ofcourse:geneswillnotliterallylastforever

justlongenoughtofunctionasaunitof

naturalselection

contrarytoorganisms

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Theselfishgene

Genesarereplicators

Onlytheytrulyreplicate

Organismsaremerelyvehicles ofgenes

Also:interactors

Theymerelyarethegenesmeans totheendofsurvival

Genesareselfishbecausealltheycareaboutistheir

own

survival Theyproduceorganisms/vehiclesonlyinordertosurvive

Note:thisiswhatDawkinsthinksitisreasonabletoinfer

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Theselfishgene

IfweweretoldthatamanhadlivedalongandprosperouslifeintheworldofChicagogangsters,wewouldbeentitledtomakesomeguessesastothesortofmanhewas.Wemightexpectthathewouldhavequalitiessuchastoughness,aquicktriggerfinger,andtheabilitytoattractloyalfriends.

Thesewould

not

be

infallible

deductions,

butyoucanmakesomeinferencesaboutaman'scharacterifyouknowsomethingabouttheconditions inwhichhehassurvivedandprospered.

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Theselfish

gene

Theargumentofthisbookisthatwe,andallotheranimals,aremachinescreatedbyourgenes.LikesuccessfulChicagogangsters,ourgeneshavesurvived,insomecasesformillionsofyears,inahighlycompetitiveworld.Thisentitlesustoexpectcertainqualitiesinourgenes.Ishallarguethatapredominantqualitytobeexpectedinasuccessfulgeneisruthlessselfishness.Thisgeneselfishnesswillusuallygiverisetoselfishnessinindividualbehaviour.

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Genes

and

the

primeval

soup

ThegenesstruggleofsurvivalNOW(inorganisms)isnotmuchdifferentfromwhatitusedtobeatthebeginningoflifeonEarth!

Intheprimevalsoupreplicatorsarosebyaccident(15ff.),diversifiedthroughreplicationerrors,andcompetedagainsteachother

Replicatorswithnumerousreplications(fecundity),lasting replication(longevity)andaccurate replication(fidelity)wonout

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Theselfishgene

The

selfishness of

genes

often

directly

translatesintothebehaviour oforganisms

Prayingmantis:femalebitesofftheheadofmaleafterorevenduringcopulation

Inordertofeedherself(andinordertoincreasethemalessexualperformance!)

Emperorpenguins:sometimespushtheirpeersintothesea

Inordertotestwhethertherearesealsinthewater(whomightkillthem)

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Theselfishgene

Butnote:

the

selfishness

of

the

gene

doesnotnecessarilyimplythat

organismsbeselfish

Geneselfishnessisverymuch

compatiblewithaltruistic behaviour

Helpingotherorganismsofthesame

speciesisameanstotheendofreplicating

genesofthesamekind

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Howselfisharegenes?

Thegene isthebasicunitofselfishness

Infact:Genesarecompetingdirectlywiththeir

allelesforsurvival,sincetheirallelesinthegene

poolarerivalsfortheirslotonthechromosomeof

futuregenerations.

at

the

gene

level,

altruism

must

be

bad

and

selfishnessgood(36)

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Howselfisharegenes?

Trulyruthlesslyselfishgenes:outlaw

genes

Noregardforwhethertheirreplicationis

ofanybenefittotheorganismornot

Examples:

JunkDNA

Drivinggenesthatdistortmeiosisintheir

ownfavour,sothattheyhaveagreater

chanceofmakingitintogametes

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Howselfish

are

genes?

Important:Dawkinsconceptionofselfishgenesdoesnotimply thatgenesnevercooperate

Genesmayservetheirowninterestsbestbycooperatingwithothergenes(p.37) Hence:selfishnessthroughcooperation

E.g.:buildingalegcannotbedonebyasingle gene Butasinglegenewillprofitfromorganisms

thatrunfast!

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Howselfish

are

genes?

Yet,singlegenesmayverywellmakea

differencetothephenotype

E.g.thelength oflegs

Analogy:plantfertilizer

Otherthingsbeingequal,plantfertilizermake

plantsgrow

Otherimportantfactors:seed,soil,sun,water,

etc./onlyiftheyarepresent,doesthefertilizer

makeadifferencetoplantgrowth

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Howselfisharegenes?

Dawkins

compares

gene

selectionism to

the

coachsselectionofoarsmen(i.e.,rowers)inboatracing

Thecoach hastopickanidealteam

Assemblesthreecrews andshufflesthemembersrandomlyandletsthemraceagainsteachother

Itturnsoutthat,onaverage,therearesomeindividualsthattendtobeinthewinningboats,andsomewhotendtobeintheloosingones

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Howselfisharegenes?

Analogy

to

gene

selection

Oarsmen =genes

Rivaloarsmenforaseatintheboat=allele

Rowingfast=buildingavehiclewhichissuccessfulatsurviving

Coach=naturalselection

Note:anygene(goodandbadones)mustcooperate withothersinordertorowfast Cooperation isintheirselfinterest

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TasksandQuestions Explainwhyaltruism isproblematiconthe

standardviewofevolution

ExplainDawkinsargumentsforwhythegeneshouldbeviewedastheunit ofselection(ratherthantheorganism);mention

Altruism

JunkDNA

Characteristicsrequiredbyevolution

Inparticular:longevity

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WhoagreeswithDawkins?

Handsup!

34

Argumentsagainstthegenes

eyeviewofevolution

1. Dawkinsgeneconcept

2. AcrucialambiguityunderminingDawkinsaccount?

3. Developmentalsystems

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Whatsagene

acc.

to

Dawkins?

Evolutionarygeneconception(fromWilliams)

Ageneisdefinedasanyportionofchromosomal

materialthatpotentially lastsforenough

generationstoserveasaunitofnaturalselection

(p.28)

Note:veryloose definitionindeed!

Nomentionofanymolecularmechanisms(such

astranslation/transcriptionetc.)

'thegenemayvaryinlength

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Theevolutionarygeneconcept

The

shorter

the

genetic

unit,

the

more

likelyitistosurvive(p.29)

Consider

Ageneticunitofhalfthesizeofachromosome:thereisa50%chancethatitwillbesplitaftereachmeiosis

Ageneticunitof1%ofthesizeofachromosome:1%chanceofsurvivalaftereachmeiosis

So:sizematters!

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Note:the

evolutionary

gene

concept

is

compatiblewithnucleotidesbeinggenes!

Theyaretheshortest portionofchromosomal

materialthatpotentiallylastsforgenerations

Plus:theycanfunctionasunitsofselection

Butthatsofcourseabsurd;nucleotidesare

notgenes

Yet,itfollowsfromDawkinsdefinition!

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Dawkinsreaction:

Itwouldbeabsurdtosaythatthedifferenttypes

ofnucleotidescompete witheachother

andthatnucleotidesofthesametypeco

operatewitheachother

If[nucleotides]

are

competitors

at

all,

they

are

competitorsforeachlocusseparately.Theyare

indifferenttothefateoftheirexactreplicasat

otherloci.(1982,p.91)

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CriticismbyGriffithsandNeumannHeld(1999)

Dawkinsonallelesofthesametype:nocompetition

Dawkinsonnucleotidesofthesametype:competition

Hence:Dawkins

is

inconsistent!

Whyistherecompetition b/wnucleotidesofthesametypebutnocompetitionb/wallelesofthesametype?

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Theevolutionary

gene

concept

Notealso:cooperationbetweensametypesof

genes/alleles isrequiredforexplaining

altruism!

Onlyifthereiscooperationatadistance

betweengenescanweexplainfromthegenes

eyeviewwhydifferentorganisms(withsimilar

genes)cooperate

Again:whatsthejustificationforthis?

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Anothercriticism:Dawkinsview

isunderminedbyanambiguity

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Animportantambiguity

Soberpoints

out

that

there

is

an

important

distinctiontobemadebetween

SelectionforX Xs survivebecause evolutionselectsforthem

SelectionofX Xs survivenot becauseevolutionselectedfor

them,butbecauseforsomeotherreason

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Illustrativeexample

Selection

forball

size

i.e.causalselection

Selectionofballcolour

i.e.,correlativeselection

E.SobercriticizesDawkinsfornotdistinguishingbetweenselectionforgenesandtheselectionofgenes

44

Animportantambiguity

Selectionforgenes

Organismssurvivebecause theyhavecertaingenes

Sober:notcorrect!Rather:b/corganismshavecertainproperties

Selectionofgenes

Organismssurvive

because

they

have

certain

features whichareadaptedtotheenvironmentandthosefeaturesarecausedbygenes

Sober:triviallytrue/widelyaccepted!

45

Acounterexample?

Selectionforgenes=false

Counterexample:sicklecellanemia

andMalaria

Heterozygotes withasicklecellallele

andanormalallelearemorelikelyto

surviveMalaria

than

homozygotes

withtwonormalalleles

Anemiasymptoms:minimal

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Acounterexample?

Sober:whatsbeingselectedforis

thegenotype(heterozygote),not

forparticulargenes(i.e.,alleles)

Howeverthereisofcourseselection

ofalleles

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Acounterexample?

Note:selectionofgenesiscompatiblewithselectionforindividuals

Itisthevehicles/interactors thatfeeltheforceoftheenvironment(i.e.,naturalselection),notthegenes

Itisthevehiclesthatare,orarenot,adapted totheirenvironments,notthegenes

Itistruethat,ultimately,evolutionischangeofgenefrequenciesinthegenepoolovertime

Butthissaysnothingaboutwhycertaingenesareselected

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ReplytoSober

Sterelny andKitcher (1988)

Theyargue:ifconstruedcorrectly,Sobers alleged

counterexamplecanbeturnedintoaconfirmation

ofDawkinsview!

Crux:theexampleturnsonthefrequency ofthe

respectiveallelesinthegenepool

Inotherwords:geneselectionisfrequency

dependent

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ReplytoSober

A

sickle

cell

allele

will

be

fitter in

contexts in

whichthenormalalleleforhemoglobinoccursfrequently

Because:insuchcontextsthesicklecellheterozygoteismorelikelythanthesicklecellhomozygote

And,organismswithasicklecellalleleandanormalallelewillhaveabetterchancetosurviveMalaria

Hence:thesicklecellallelewillbeselectedfor

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ReplytoSober

Yetincontexts inwhichthesicklecellalleleisfrequent,thesicklecellallelewillbeunfit

Thentheorganismisatahighrisktodieofsicklecellanemia

Hence:normalallelewillbeselectedfor

Thus,itisnottruethat,asSoberclaims,thegenotype,

but

not

genes

are

being

selected

for

Onthecontrary,genes/allelesarebeingselectedfor,justasDawkinsclaims

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Developmentalsystems

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Geneticdeterminism?

Criticism:Dawkinsviewpresupposesgeneticdeterminism

Geneticdeterminism:istheviewthatthephenotypeisfullydeterminedbythegenotype

R.Gray,P.Griffiths,andothers:

geneticdeterminismiswrong!

Environmentalconditionsarejustasimportantasgenesintheexpressionofthephenotype!

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Geneticdeterminism?

NumberofeyesinDrosophila(wildtype)

Normally: between700and1100(temperaturedependent!)

Mutations

UltrabarandInfrabar:bothconsistently lessthanthewildtype

However: theanswertothequestionwhichmutationhasmoreeyes,UltrabarorInfrabariscontextdependent

Temperaturetoodetermineseyenumber(notjustgenes)

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Geneticdeterminism?

Challenge

to

Dawkins:

Genesdonotdeterminethephenotype

Thereareotherimportantfactors(e.g.environment)

Butifgenesdonotdeterminethephenotype,andthereareotherimportantfactors,then

.wecannotreallysaythatgenesarebeingselectedforwhencertainorganismssurviveandprocreate(andtherebyreplicategenes)

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Geneticdeterminism?

Question:

does

Dawkins

really

subscribe

togeneticdeterminism?Whatsmore,doeshisviewreallyrequireit?

Dawkins:

Developmentoforganisms:Geneticcausesandenvironmentalcausesareinprinciplenodifferent.

Evolution:Geneticfactorsreplicatethemselvesbutnongeneticfactorsdonot

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Geneticdeterminism?

Itsnottruethatonlygenesarereplicatedthroughoutgenerations

Exampleforextragenetic inheritance:aphidBuchneraendosymbiosis

Aphidswithout Buchnera:stuntedgrowth,reproductively sterile,dieprematurely

MaternalBuchneramassisbeingpassedontoeggsorembryo

Remarkablyancientsymbioticrelationship

160 280millionyears!

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Aphid=bladlus

Geneticdeterminism?

AphidBuchneraexamplessatisfiesDawkinsthreecriteria Longevity (sincewehaveinheritanceonan

evolutionaryscale)

Fecundity,andfidelity (numerousandaccuratereplication)

Note:buchnera arenotpartofthegenetic

programme ofaphids!

ContrarytoDawkins:thewholedevelopmental systemisbeingreplicatedindefinitely

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Aphid=bladlus

Geneticdeterminism?

Epigeneticinheritancethroughmethylation

Methylgroupsblockthetranscriptionofanygenestheyareattachedto

Normallyremovedduringzygoteformationandreestablished duringcelldivisions

Methylationlevelisthoughttobeinfluencedbyexternalfactorslikediet

Hence:

Changeofgeneexpressionthroughchangeofexternalfactors

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Developmentalsystems

GriffithsandGraysconclusion:

Theunitofselectionisnotjustthegenebut

ratherentiredevelopmental systemswhich

arebeingreplicated(onanevolutionary

scale)

Thegene isjustoneamongmanyother

factorsdeterminingthephenotype

Others:environment

Hence,thegeneisnottheunitofselection

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TasksandQuestions Explain

Griffiths

and

Neumann

Helds

challengeabouttheevolutionarygene

ExplainSobers sicklecellcounterexampleto

Dawkinsgeneeyeview

ExplainSterelnyandKitchers responseto

Sober

Explaintheideaofdevelopmentalsystems

withregardtotheunitofselectiondebate

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Lecturequery Explain

Dawkins

idea

of

the

gene

being

the

unitofselection

Mentiontheideaofthelongevityofreplicators

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