Viewpoint

We live in interesting times. Twowell-known biologists—E.O.Wil-

son and Richard Dawkins—and someof their well-known colleagues,who usedto employ broadly similar selectionmod-els, now deeply disagree over the role ofgroup selection in the evolution of eu-sociality (or so we will argue). Yet theydescribe their models as interchange-able. As philosophers of biology, wewonder whether there is substantial (i.e.,empirical) disagreement here at all, and,if there is, what is this disagreementabout?We argue that a substantial disagree-

ment over the processes that caused eu-sociality best explains this debate, yet thecommon practice of using overarchingdefinitions for“group selection”and“kinselection” renders empirical differencesdifficult to detect.We suggest Michael J.Wade’s use of these terms as a basis formodels that reveal different selectionprocesses.Wade’s models predict differ-ent outcomes for different processes andthus can be tested.Some background: Thirty-three years

after the publication of Sociobiology: TheNew Synthesis (HarvardUniversity Press,1975), E. O.Wilson seems to be makingan almost 180-degree turn (Wilson 2008).Back then,Wilson accepted a broad de-finition of “kin selection” as the favor ordisfavor of individuals based on kin re-latedness, but nowhe claims this conceptapplies only to collateral relatives (i.e.,those other than parents and offspring).Back then, Wilson thought eusocialitywas all about relatedness,whereas nowheargues for a minor—if any—explana-tory role for kin selection.AlthoughWil-son has always claimed to support groupselection theory, only recently has thisinclination channeled into a specificmathematical model of group selectionand against the centrality of kin selection.

One thing has not changed:Wilson’s veryrich and well-organized assembly ofrecent empirical findings.His opponents,who favor kin selection

over group selection, target his interpre-tation rather than his facts. Indeed, bothsides declare that theirmodels are trans-latable, that is, they could agree withany set of data the other model agreedwith (Dawkins 1982,Wilson andWilson2007). If this disagreement were purelyabout terminology, onewould expect thecommunity to gradually lose interest init.This has not happened.Another optionis that this debate continues because it issemantic in a nontrivial way: that is, themodels agree with all the data but differgreatly in their heuristic value. In thatcase, one would expect many method-ological comparisons of model perfor-mance—for example, comparisons ofmodels’ precision, generality, accuracy,complexity, or elegance—for variousspecies and social phenomena in the laband in nature.Yet these are not a centralpart of the debate either. Rather, it seemsthere is no given phenomenon both sidesuse; instead, disputants clash on how todefine or describe the phenomenon thatour models attempt to fit to. In short,they disagree over what it is that we seewhen some ants walk by.ForWilson andWilson (2007), a group

is any aggregation of individuals that issmall comparedwith the total populationand consists of individuals interactingin a nonrandom way that affects eachother’s fitness. This is an extremely ab-stract understanding of what constitutesa group, one that fitsmany kinds of casesand is almost completely unconstrainedby any particular population structure,dynamic, duration, or size. Nor does itrequire groups to multiply as anythinglike cohesive wholes in order to acquireheritable variance in fitness. Such a broad

definition of “group” is central for Wil-son andWilson’s definition of group se-lection: “the evolution of traits based onthe differential survival and reproduc-tion of groups.” Such a group selectionmodel does not differ empirically fromthe similarly broad definition of kin se-lection:“selection affected by relatednessamong individuals” (Foster at al. 2006).Again, no particular population struc-ture constrains the application of thiskin selectionmodel.The difference lies inmodel structure: whereas the groupselection model partitions the overallselection in the population into“within-group selection” and “between-groupsselection,” alternative models—kin se-lection, reciprocity, indirect reciprocity, ormutualism—consider such partitioningunnecessary, since they all claim thatwhat enhances group fitness alwaysenhances the inclusive fitness of eachmember in the group (or rather, whatDawkins “only partly facetiously” de-scribes as“that property of an individualorganism which will appear to be maxi-mized when what is really maximized isgene survival” [Dawkins 1982, p. 187]).This theoretical difference in model

structure does not necessarily empha-size different causal factors, because thecontexts that can affect the frequencyof altruists—population structure andecology—can be captured by bothmodels (Foster et al. 2006,Wilson 2008).The contexts therefore do not constrain

Group Selection Is Dead! Long LiveGroup Selection?AYELET SHAVIT AND ROBERTA L. MILLSTEIN

Ayelet Shavit (e-mail: ashavit@UCDavis.edu) is a

Marie Curie Fellow in the Department of Philoso-

phy at the University of California–Davis, and inTel

Hai College, Israel. Roberta L. Millstein (e-mail:

rlmillstein@UCDavis.edu) is an associate professor

in the Department of Philosophy at the University

of California–Davis. © 2008 American Institute of

Biological Sciences.

574 BioScience • July/August 2008 / Vol. 58 No. 7 www.biosciencemag.org

either model, as both measure the evo-lutionary outcome only in gene fre-quencies, not as the process of evolvinga new level of organization (Griesemer2000). So, argue Foster and colleagues(2006), if E.O.Wilson’s new groupmodeldoes not generate facts unattainable oth-erwise, why accept his definition of kinselection rather than Maynard Smith’soriginal definition—the evolution ofcharacteristics that favor the survival ofclose relatives of the affected individual?And when Wilson states that “the finalstep to eusociality can occur with thesubstitution of only one allele or a smallset of alleles” (Wilson 2008), why notcall this allele for staying in the nest—which is easily recognizable by an arbi-trary marker identifiable in other ants(such as an odor) and promotes favor ofthose ants—byDawkins’s original term,“green beard effect”? Yet Wilson asks inreturn,why not go back toDarwin’s orig-inal explanation of group selection? Thusthe debate again seems to be over ter-minology, this timewith a historical twist.But why should biologists care, as they

obviously do? If the disagreement weremainly about choosing among inter-changeable perspectives for the samephenomenon, a choice based on per-sonal taste, historical uses, or heuristicvalues of group or kinmodels, onewouldexpect the debate to gradually dissolve inthe first two cases and become pragmaticand methodology based in the third.Since the debate has neither dissolvednor turned pragmatic, and since weassume the debate is a rational one, we

suggest the remaining explanation as thebest one: Wilson and Dawkins disagreeover semantics because both hope fortheir different concepts and models torefer to different evolutionary processesin the world,with eachmaintaining thathis preferred evolutionary process is themore prevalent. To use Dawkins’s terms,even when modestly arguing over theflipping picture we see in aNecker cube,the nonmodest aim remains to decipherthe picture we see from an East Africanmountain: are the small spots below in-sects or buffalos (Dawkins 1982)?WhenWilson looks at a social group

he sees a unit that is a target of a selection,while Dawkins sees an illusory by-product of a different selection processacting at a single level of organization:gene selection. They disagree the waythey do because they aim to accuratelyrepresent empirical facts, but since bothsides employ overly broad definitions forgroup, group selection, and kin selec-tion, it becomes very difficult to identifya specific fact—for example, a particularpopulation dynamic or structure—todistinguish between these models in aparticular case.We think this situation isunfortunate.Whether or not certain sub-populations have heritable variance infitness is an empirical question, what-ever you choose to call these entities(Griesemer 2000). Luckily, an alterna-tive is already present in the literature.Wade (1978, 1985) defined group selec-tion and kin selection in accordwith dif-ferent population structures, so hisconstrained models could clearly refer

to distinct selection processes that he andhis colleagues then compared in the labor in the field.Dawkins andWilsonmayobject that Wade’s definitions are toonarrow.Theywould be right in the sensethat his definitions do not cover manykinds of cases, yet that does not imply thathis definitions do not cover many cases.They do. Indeed, narrow definitions—those that restrict the kinds of cases—giveus tools to determinewhat is andwhat isnot happening in a given population,whereas the broad definitions used byDawkins and Wilson will forever talkpast each other without resolution.

AcknowledgmentWe thank James R. Griesemer for help-ful comments on this essay.

References citedDawkins R. 1982.The ExtendedPhenotype.Oxford

(United Kingdom): Oxford University Press.Foster KR,Wenseleers T, Ratnieks FLM. 2006. Kin

selection is the key to altruism.Trends in Ecol-ogy and Evolution 21: 57–60.

Griesemer JR. 2000.The units of evolutionary tran-sition. Selection 1: 67–80.

Wade MJ. 1978. A critical review of the models ofgroup selection.Quarterly Reviewof Biology 53:101–140.

———. 1985. Soft selection, hard selection, kinselection, and group selection. American Nat-uralist 125: 61–73.

Wilson EO. 2008. One giant leap: How insectsachieved altruism and colonial life. BioScience58: 17–25.

Wilson EO,Wilson DS. 2007. Rethinking the the-oretical foundation of sociobiology.QuarterlyReview of Biology 82: 327–348.

doi:10.1641/B580702Include this information when citing this material.

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