Ancestry-constrained phylogenetic analysis supports the Indo-European steppe hypothesis

51 Pages·0.856 MB·English

by  Will Chang et al.

ANCESTRY-CONSTRAINEDPHYLOGENETICANALYSISSUPPORTSTHE
INDO-EUROPEANSTEPPEHYPOTHESIS
WillChang ChundraCathcart
UniversityofCalifornia,Berkeley UniversityofCalifornia,Berkeley
DavidHall AndrewGarrett
UniversityofCalifornia,Berkeley UniversityofCalifornia,Berkeley
DiscussionofIndo-Europeanoriginsanddispersalfocusesontwohypotheses.Qualitativeevi-
dencefromreconstructedvocabularyandcorrelationswitharchaeologicaldatasuggestthatIndo-
European languages originated in the Pontic-Caspian steppe and spread together with cultural
bp
innovationsassociatedwithpastoralism,beginningc.6500–5500 .Analternativehypothesis,
accordingtowhichIndo-EuropeanlanguagesspreadwiththediffusionoffarmingfromAnatolia,
bp
beginningc.9500–8000 ,issupportedbystatisticalphylogeneticandphylogeographicanalyses
oflexicaltraits.ThetimeandplaceoftheIndo-Europeanancestorlanguagethereforeremaindis-
puted.Herewepresentaphylogeneticanalysisinwhichancestryconstraintspermitmoreaccurate
inferenceofratesofchange,basedonobservedchangesbetweenancientormedievallanguages
andtheirmoderndescendants,andweshowthattheresultstronglysupportsthesteppehypothe-
sis.Positingancestryconstraintsalsorevealsthathomoplasyiscommoninlexicaltraits,contrary
totheassumptionsofpreviouswork.Weshowthatlexicaltraitsundergorecurrentevolutiondue
torecurringpatternsofsemanticandmorphologicalchange.*
Keywords: lexical change, linguistic phylogenetics, Indo-European chronology, Indo-European
dispersal,steppehypothesis
Thisarticlehasthreemaingoals.First,weshowthatstatisticalphylogeneticanalysis
supports the traditional steppe hypothesis about the origins and dispersal of the Indo-
European language family. We explain why other similar analyses, some of them
widely publicized, reached a different result. Second, for skeptics about phylogenetic
methodology,wesuggestthattheagreementbetweenourfindingsandtheindependent
results of other lines of research confirms the reliability of statistical inference of re-
constructed chronologies. Finally, for linguistic phylogenetic research, we argue that
analysesgroundedintheevolutionarypropertiesofthetraitsunderstudyyieldmorere-
liableresults.Ourdiscussionmakesreferencetoancestryrelationships,forexamplebe-
tweenOldIrishandtwomodernlanguagesdescendedfromit,IrishandScotsGaelic,
and draws on what can be learned from direct observation of changes over historical
ancestry constraints
time. In our phylogenetic analyses, we introduce and show
thattheyresultinmorerealisticinferencesofchronology.
Ourarticleisorganizedasfollows.Wefirstgivebackgroundinformationaboutthe
steppeandAnatolianhypotheses,andaboutearlierphylogeneticanalyses(§1),anddis-
cusslexicaltraits(§2)andlinguisticancestryrelationships(§3).Wethendescribeour
dataandsomemeasurementsmadedirectlyonthedata(§4),explainourphylogenetic
methods(§5),andsummarizeourexperimentalresults(§6).Finally,wediscusstheef-
*WethankClaireBowern,RussellGray,SimonGreenhill,HannahHaynie,GaryHolland,LevMichael,
JohannaNichols,DonaldRinge,andMichaelWeissforcommentsanddiscussion,TomRechtforhelpwith
Greekdata,QuentinAtkinsonandRemcoBouckaertforsharingcodeanddata,MichaelDunnforassistance
withIELEX,andaudiencesinBerkeley,Oslo,andSanDiegoforfeedbackandsuggestions.Ourworkwas
supportedbytheDieboldFundforIndo-EuropeanStudies,UniversityofCalifornia,Berkeley(CC,WC,AG)
andaGooglePh.D.FellowshipandGrantIIS-1018733fromtheNationalScienceFoundation(DH).
194
PrintedwiththepermissionofWillChang,ChundraCathcart,DavidHall,&AndrewGarrett.©2015.
Ancestry-constrainedphylogeneticanalysissupportstheIndo-Europeansteppehypothesis
195
fects of advergence (§7) and ancestry constraints in phylogenetic modeling (§8), fol-
lowedbyconclusions(§9)andappendiceswithdetailsaboutmethodsandresults.1
Indo-europeanbackground.
1.
Thesteppeandanatolianhypotheses.
1.1. TherelationshipsofIndo-European
(IE)languageshavebeenstudiedforovertwocenturies,butitisstilldisputedwhenand
where their common ancestor Proto-Indo-European (PIE) was spoken, and how they
spread beforetheyfirstappeared in historicalrecords about3,700 years ago.Two hy-
pothesesdominatediscussion.
Accordingtoatraditionalhypothesis(Gimbutas1973,1997,Mallory1989)accepted
by many linguists (Ringe 2006, Parpola 2008, Fortson 2010, Beekes 2011), PIE was
spokeninthePontic-Caspiansteppe,northoftheBlackandCaspianSeas.Thesteppe
hypothesisassociatesIElanguagespreadwiththediffusionofculturalinnovationsre-
latingtopastoralism,includinghorsedomestication,wheeledvehicles,andtheweaving
of wool from woolly sheep.Analyses of archaeological data from this point of view
suggestaPIEdispersaldatec.6500–5500bp,probablyinthefirsthalfofthatperiod.2
It is now also widely assumed that Anatolian was the first branch to separate from
PIE.3Withintheframeworkofthesteppehypothesisthecommonancestorofthenon-
Anatolianlanguages,Proto-Nuclear-Indo-European(PNIE),mightthenhavebeenspo-
bp
kenc.6000–5000 .
According to an alternative hypothesis proposed by Renfrew (1987), IE languages
spread into Europe with the diffusion of agriculture fromAnatolia; see also Renfrew
1999,2000a,b,2001,2003.Thismechanismisplausible,sinceclearcasesoflanguage
dispersalwiththespreadofagricultureareknownelsewhereintheworld(Bellwood&
Renfrew 2002, Diamond & Bellwood 2003, Bellwood 2004). Given that farming
bce
reachedsoutheastEuropebytheseventhmillennium (vanAndel&Runnels1995,
Perlès2001,Bocquet-Appeletal.2009),theAnatolianhypothesisimpliesaPIEdisper-
saldatec.9500–8000bp.4
1Datasetsandfiguresshowingsummarytreesforallofouranalysesappearinonlinesupplementaryma-
terials,whichcanbeaccessedathttp://muse.jhu.edu/journals/language/v091/91.1.chang01.html.WecitePIE
bp: ce
verbrootsfromRixetal.2001,andweusethefollowingabbreviations: beforepresent(2000 ),HPD:
highest posterior density, IA: Indo-Aryan, IE: Indo-European, IELEX: Indo-European Lexical Cognacy
Database(http://ielex.mpi.nl/),ME:MiddleEnglish,OE:OldEnglish,PIE:Proto-IE,NIE:NuclearIE(the
non-AnatolianIEclade),PNIE:Proto-NIE,RM:root-meaning(traits),RSC:restrictionsitecharacter,SDC:
stochasticDollocharacter,(T)MRCA:(timeofthe)mostrecentcommonancestor.
2ArchaeologistshavesuggestedPIEdates‘about4,500bc’(Mallory1989)and‘about4,400–4,200bc’
(Anthony2013);seealsoDarden2001,Mallory&Adams2006,Anthony2007,andAnthony&Ringe2015.
bp
SomephylogeneticanalysesattributePIEdatesof6000–5000 tothesteppehypothesis(Gray&Atkinson
2003,Atkinsonetal.2005,Bouckaertetal.2012);RyderandNicholls(2011)characterizethehypothesis
moreaccurately.
3Thisideahasalongpedigreeunderthelabelindo-hittite(Sturtevant1929,1933)andisacceptedinone
form or another in much current research (Oettinger 1986, Strunk 1994, Melchert 1998, Lehrman 2001,
Melchert2001,Ringeetal.2002,Jasanoff2003,Rieken2009,Yakubovich2010).
4AthirdhypothesisthathasgainedlesstractioncanbeseenasahybridoftheAnatolianandsteppehy-
potheses.ItpositsthatPIEwasspokenatthetimeassumedbythesteppehypothesis,butineasternAnatolia
(Barber2001)ortheCaucasus(Gamkrelidze&Ivanov1995,Ivanov2001).Accordingtothishypothesis,
afterPNIEspreadnorthfromAnatolia,thesteppewasthestaginggroundforNIEexpansionintoEuropeand
Asia.Allelsebeingequal,however,linguisticgeographyfavorsawesternoriginfortheAnatolianbranchof
IE,sincethegreatestbranch-internaldiversityisinthewest;thisismosteasilyexplainedbyassumingthat
Proto-AnatolianspreadacrossAnatoliafromthewest.Ivanov’s(2001)alternativeanalysisofAnatoliandi-
alectologyhasnotgainedsupportfromotherspecialists(Melchert2001,Yakubovich2010).
196 LANGUAGE,VOLUME91,NUMBER1(2015)
Inprinciple,evidencebearingonIEoriginsanddispersalmaycomefromarchaeol-
ogy,genetics,orlinguistics.Atpresent,geneticdataisinsufficienttoresolvethematter,
sinceancientEuropeanDNAandcomparisonofancientandmodernDNAconfirmnot
justimmigrationfromtheNearEastatthetimeofthefarmingdispersal,butalsolater
populationmovementfromnorthernEurasiathatisconsistentwiththesteppehypothe-
sis;seeBrandtetal.2013andLazaridisetal.2014.Inpractice,discussionhasmainly
focusedonarchaeologicalandlinguisticarguments.
Several arguments have been advanced in favor of the steppe hypothesis; a recent
review is by Anthony and Ringe (2015). The first argument is from archaeological
analysis. For example, based on correlations among archaeological data, documented
culturalpractices,andvocabulary,researchershavearguedthatProto-Indo-Iranianwas
bp
spokenc.4300–3700 inanareaofcentralAsiaaroundtheAralSea(Lubotsky2001,
Witzel2003,Kuz’mina2007).5ThisincludestheSintashtacultureofthesteppetothe
north,whoseeconomywaspastoralandwhosecemeteriescontainhorsesacrificesand
chariots(Anthony2009),aswellasthemoreurbanizedBactria-MargianaArchaeolog-
icalComplextothesouth(Hiebert1994).Thelattermayhavebeenthestagingground
forIndo-Iraniandispersal.Ifthisargumentiscorrect,thenfromwhatwecaninferabout
cultural interactions in this region, Indo-Iranian speakers probably entered the area
from the steppe. This line of reasoning locates speakers of an Indo-Iranian precursor
bp
northoftheCaspianSeac.5000–4500 ,closeintimeandplacetoPNIEifthelatter
bp
was spoken in the steppe c. 6000–5000 . In other words, the diffusion of cultural
traitsthatareobservedinthearchaeologicalrecord(andinsomecasesreportedinlater
textual sources) correlates well with the chronology of the steppe hypothesis. Similar
analyseslinkIE-speakingEuropeanpopulationswithculturechangesthatcanbeiden-
tified as moving from the steppe and eastern Europe within the chronological frame-
workofthesteppehypothesis.
Asecond argument is based on inferences about environment and material culture
from reconstructed vocabulary. For example, wheeled-transport vocabulary is recon-
structedforPIE(Mallory&Adams1997,2006,Parpola2008)orPNIE(Darden2001).
Since wheeled transport was invented long after farming reached Europe, if PIE or
PNIEhadsuchvocabularyitcannothavebeenspokenbyearlyfarmers.Itisfairtosay
that most of those writing from a linguistic perspective, though not all (Krell 1998,
Clackson2000),havebeenimpressedbytheextentoftheevidence.Theargumentsare
in any case based on an assemblage of individual points, each of which needs careful
evaluation.
Athirdargumentisbasedonlinguists’subjectiveimpressionthatearlyIElanguages
are more similar grammatically and phonologically than would be expected from the
Anatolianchronology;seeTable1.After4,500ormoreyearsofdivergenceontheAna-
tolianchronology,somegrammaticalpatternsremainintactwithonlyafewchangesin
each language; see, for example, Hittite [esmi, esi, estsi] = Sanskrit [ásmi, ási, ásti].
ː ː ː ͜
Similarly, only a few sound changes distinguish Hittite [χanti], Sanskrit [ánti], and
Greek[ánti];suchexamplescanbereplicatedthroughoutthegrammarandlexicon.The
5Becauselanguageandmaterialculturespreadindependently,somearchaeologistsemphasizethatcorre-
lationsofspecificarchaeologicaldatawithethnicityorlanguagecannotbedemonstratedconclusivelywith-
outinscriptionalevidence.ButmostlinguistswouldprobablyagreethatKohl(2009:236)goestoofar,inhis
otherwiseexcellentsurveyofBronzeAgeEurasia,insuggestingthat‘[t]herewasnosingleIndo-Europeanor
Proto-Indo-European“homeland”butjustaneverunfoldinghistoricalprocessofdevelopment’.Iftherewas
aPIElanguage,itwasspokensomewhere.
Ancestry-constrainedphylogeneticanalysissupportstheIndo-Europeansteppehypothesis
197
PIE hittite vedicsanskrit greek
‘Iam’ *h1ésmi[ʔésmi] ēšmi[eːsmi] ásmi[ásmi] eimí[eːmí]
‘you(sg.)are’ *h1ési[ʔési] ēšši[eːsi] ási[ási] eĩ[ẽː](dialectalessí)
‘s/heis’ *h1ésti[ʔésti] ēšzi[eːst͜si] ásti[ásti] estí
‘theyare’ *h1sénti[ʔsénti] ašanzi[asant͜si] sánti[sánti] eisí[eːsí](dialectalentí)
‘bear’ *h2rtḱos[χrˌtkos] h̬artaggaš[χartkas] ŕḳ ṣas[ŕˌkʂas] árktos
‘cloud,sky’ *nébhos[nébos] nēpiš[nebis] nábhas[nábas] néphos
̤ ː ̤
‘wood’ *dóru[dóru] tāru[taru] dāèru[dáru] dóru
ː ː
‘vis-à-vis’ *h2ánti[χánti] h̬anti[χanti] ánti[ánti] antí
‘yoke’ *yugóm[ju óm] yugan[ju an] yugám[ju ám] zdugón
ɢ ɡ ɡ ͜
Table
1.SelectedvocabularyinPIEandthreeearlyIElanguages.
divergencetimepositedbytheAnatolianhypothesisisroughlytwicethatofthepres-
ent-dayGermanic,Romance,orSlaviclanguages,butmanylinguistshaveasubjective
impressionthatthedifferencesinTable1arenottwiceasgreat.Yetwehavenogener-
allyacceptedwaytoquantifyimpressionsofsimilarityinphonologyorgrammar,orto
show that examples like those inTable 1 are representative, so this argument remains
impressionistic.6
Twofurtherargumentsprobablysupportonlyaweakerposition,namely,thatPNIE
wasspokeninthePontic-Caspiansteppe.Oneconcernsevidenceforearlycontactbe-
tween IE and early western Uralic languages (Joki 1973, Koivulehto 2001, Janhunen
2009). Given the location of Uralic in northern Eurasia, such contact must have oc-
curred north of the Black and Caspian Seas. The evidence for contact between early
Uralic languages and the Indo-Iranian branch of IE is uncontroversial, supported by
dozensofunambiguousloanwords,andacceptedbyspecialists(Rédei1986,Lubotsky
2001, Mallory 2002). There is similarly clear evidence for contact with Balto-Slavic
(Kallio2005,2006,2008)andGermanic(Hahmoetal.1991–2012).Theevidencefor
contact with PIE itself is weaker (Kallio 2009), perhaps because Uralic languages
spread from the east into northern Europe and Proto-Uralic itself was not spoken in
proximitytothesteppe.7
Finally, some morphological evidence suggests that the Greek, Armenian, Balto-
Slavic,andIndo-IraniansubfamiliesformacladewithinIE(Ringeetal.2002).Since
GreekisspokentothewestofAnatolia,andArmenianandIndo-Iraniantotheeast,itis
hardtoconstructadiversificationscenarioconsistentwiththeAnatolianhypothesisin
whichtheselanguagesremainedincontactafterPNIE,unlessthelatterwasitselfspo-
ken on the steppe. The steppe hypothesis makes this easier: the four subfamilies in
question remained in proximity, after the departure ofTocharian to the east and Italo-
Celtic,Germanic,andotherstothewest.
TwomainargumentssupporttheAnatolianhypothesis.First,asoriginallynotedby
Renfrew (1987), the spread of agriculture provides a plausible mechanism for large-
scale language dispersal, one with clear parallels elsewhere. The language dispersal
mechanismsrequiredinthesteppehypothesisarelesswellunderstood,partlybecause
pastoralsubsistenceeconomiesarenotascommonworldwide.Second,beginningwith
Gray&Atkinson2003,theAnatolianhypothesishasbeensupportedbyresearchusing
6Holmanandcolleagues(2011)provideaphonologicaldistancemeasurefromwhichtheyinferaPIE
bp
time-depthofabout4350 .Thatisfartoolate(onlyafewcenturiesbeforethefirstattestationofalready
differentiatedIElanguages),butitdoesquantifytheimpressionthatIElanguagesaremoresimilarphono-
logicallythaninvocabularypatterns.SeeClackson2000foraperceptive,skepticaldiscussionoftheargu-
mentfromimpressionisticsimilarity.
7ForrecentdiscussionseeHäkkinen2012andParpola2012.
198 LANGUAGE,VOLUME91,NUMBER1(2015)
statisticalmethodsadaptedfrombiologicalphylogenetics(Atkinsonetal.2005,Atkin-
son & Gray 2006, Nicholls & Gray 2008, Gray et al. 2011, Ryder & Nicholls 2011,
Bouckaertetal.2012,2013).Thisisalsothefocusofourresearch.
Methodological differences between fields contribute to the present impasse.Argu-
ments for the steppe hypothesis are mostly qualitative rather than quantitative, and
come from traditional lines of reasoning in historical linguistics and archaeology. In
contrast,acrucialargumentfortheAnatolianhypothesisisquantitative,relyingonsta-
tistical methods that originated in another discipline. Thus some researchers have ex-
pressed skepticism about chronological inference with statistical methods (Clackson
2000,2007,Evansetal.2006,McMahon&McMahon2006),whilesomeadvocatesof
suchmethodshavewrittenthathistoricallinguisticsmethods‘all…involveintuition,
guesswork, and arguments from authority’(Wheeler & Whiteley 2014). We hope our
workcancontributetoarapprochementbetweenthetworesearchtraditions.
Indo-european phylogenetics.
1.2. IE linguistic phylogeny has been studied for
many decades (Meillet 1922, Porzig 1954, Birnbaum & Puhvel 1966), but statistical
phylogenetic research is relatively recent in IE (Tischler 1973). Dyen and colleagues
(1992)usedlexicostatisticstoproduceaclassificationofIElanguagesbyanalyzinga
wordlistofeighty-fourmodernlanguagesand200basicmeaningscompiledbyIsidore
Dyen.Their method assumed a similar overall rate of lexical change in all languages.
An alternative approach to classification that dispenses with this assumption was em-
ployedbyRingeandcolleagues(2002)toaddresstheissueofhigher-orderstructurein
IE. They analyzed a data set created by Don Ringe and Ann Taylor, consisting of
phonological,morphological,andlexicaltraitsfromtwenty-fourpredominantlyancient
andmedievallanguages.Thesetwoworksyieldedtwowordlistswithcognatecoding;
oneorboth,orbothcombined,wereusedinallsubsequentwork.
In2003,GrayandAtkinsonpresentedthefirstBayesianphylogeneticanalysisofIE
chronology;theyusedtheDyenwordlist,supplementedwithHittite,TocharianA,and
TocharianBdata.Historicallyattestedeventswereusedtodatevariouslinguisticsplits,
rate smoothing
and over the branches of the inferred tree was used to relax the as-
sumptionofaconstantrateofchange.Asinallsubsequentanalysespriortoourwork,
the inferred root age supports theAnatolian hypothesis. Nicholls and Gray (2008) re-
worked Gray and Atkinson’s analysis by replacing the trait model, which permitted
multiplegainsinthesamelexicaltrait,withonethatdidnot;theyalsoperformedasep-
arate analysis on the lexical traits of a subset of the languages from the Ringe-Taylor
dataset.RyderandNicholls(2011)thenaddedamodeloflexicographiccoveragethat
enabledthemtoworkwithalltwenty-fourlanguagesintheRinge-Taylordataset,many
of which, like Oscan and Old Persian, are scantly attested. Bouckaert and colleagues
(2012)performedaphylogeographicanalysis:itsgoalwastoinferthegeographicallo-
cationofPIE,butembeddedinitwasaphylogeneticanalysisthatsupersededprevious
workinmostrespects.8Mostnotably,theinferencesoftwaresupportedmanydifferent
trait models, including the single-gain trait model devised by Nicholls and Gray, and
thedatawasbasedonaharmonizationoftheRinge-TaylorandDyendatasets.Bouck-
aertandcolleagues(2013)addressedanerrorinthecodingofthedatawithoutaltering
theirgeneralconclusions.
8Ourworktodatedoesnotmodelgeographicdispersaloraddresstheirphylogeographicfindings;thisre-
mainsadesideratumforfutureresearch.
Ancestry-constrainedphylogeneticanalysissupportstheIndo-Europeansteppehypothesis
199
Figure
1.AnalysisA1summarytree.Modernlanguageswithnoancestorsinthedatasetareexcluded.This
treeshowsmedianposteriornodeheights,medianposteriorbranchratemultipliers(widthofhorizontal
lines),timeconstraintsonancientandmedievallanguages(brightredbars),cladeconstraints
(verticalblackbars),andposteriorcladeprobabilitieslessthan98%.
Wenowbrieflypreviewourresults.UsingthesamemodelanddatasetasBouckaert
andcolleagues(2012,2013),butwithincrementalchangestoboth,wefoundarootage
that strongly supports the steppe hypothesis. The key difference was that we con-
strainedeightancientandmedievallanguagestobeancestraltothirty-ninemodernde-
scendants.Usingancestryconstraintsissimilarinspirittostipulatingtheknowndates
of historical languages, or stipulating uncontroversial clades that are not the object of
inquiry.Theancestor-descendantrelationshipswepositareuncontroversial,butcould
notbeinferredbythemodel.Figure1showstheresultofananalysiswithancestrycon-
straints and other refinements, where the only modern languages included are those
withdocumentedancestors.Figure2showsasimilaranalysiswithmodernlanguages
200 LANGUAGE,VOLUME91,NUMBER1(2015)
Figure
2.AnalysisA2summarytree.ModernlanguagesareincludedfromallIEsubfamilies.
SeeFig.1captiontointerpretgraphicalelements.
fromallIEsubfamilies.Figure3showstheinferredIErootagesinselectedstudies,be-
ginningwithGray&Atkinson2003andendingwithourwork.
Lexicaltraits.
2. Linguistsinferrelationshipsfrommorphological,phonological,
and lexical traits. Morphological and phonological traits, however, are interdependent
Ancestry-constrainedphylogeneticanalysissupportstheIndo-Europeansteppehypothesis
201
GA NG NG RN B C
1 2
9500bp
anatolian
8000
6500
steppe
5500
Figure
3. Inferred IE root age distributions in selected studies. GA: Gray &Atkinson 2003; NG1, NG2:
Nicholls&Gray2008,usingDyenandRinge-Taylordatasets;RN:Ryder&Nicholls2011;B:Bouckaertet
al.2013;C:analysisA1correctedrootagefromourwork(§7.1).Plottedarethe95%highest-densityinterval
(verticallines),themean(NG,RN)ormedian(B,C)ifknown,andintervalsforthesteppeand
Anatolianhypotheses(dashedlines).
inwaysthatarepoorlyunderstood.9Forthisreason,andbecauselargelexicaldatasets
are available, most statistical work on language relationships analyzes lexical traits.
cognatetraits root-
Thereareatleasttwotypesoflexicaltraits,whichwecall and
meaningtraits
.Theyhavenotbeendistinguishedinpreviousphylogeneticresearch.
Languagesshareacognatetraitiftheysharecognatewords,thatis,wordsdescended
fromthesameancestralwordform.Forexample,EnglishandGermanshareacognate
traitbecausetimberandZimmer‘room’aredescendedfromGermanic*timra-(derived
from a PIE root *demh - ‘build’); likewise, German Gast ‘guest’ and Latin hostis
2
‘stranger,enemy’defineacognatetraitbecausetheyaredescendedfromaform*ghosti-
(Bammesberger 1990, Ringe 2006). Cognate words need not have the same meaning.
Cognatetraitsarewidelystudiedincomparativeandhistoricallinguistics,butareonly
occasionallyusedinstatisticalphylogeneticstudies(e.g.Gray&Jordan2000).10
Moreoften,thedataconsistsofroot-meaning(RM)traits,whichencodewhetherthe
most semantically general and stylistically neutral word for a given meaning is based
onagivenancestralroot;meaningsareoftenchosenfroma‘Swadesh’listofoneortwo
hundredbasicmeanings.SuchtraitsarethebasisformostIEanalyses,includingours.
Forexample,sinceEnglishfeatherisderivedfromaPIEroot*pet-‘tofly’,Englishhas
atrait[*pet-,‘feather’];becauseLatinserpens‘snake’isderivedfrom*serp-‘tocreep’,
9Typologicaltraitsarealsosometimesusedinanalyzinglanguagerelationships,thoughtheysharedraw-
backsofbothlexicaltraits(theyspreadeasily)andnonlexicaltraits(theyareofteninterdependent).Somedif-
ficultiesofusingmorphologicalandphonologicaltraitsinstatisticalphylogeneticanalyseshavealsobeen
discussedbyTaylorandcolleagues(2000)andRingeandcolleagues(2002).
10Cognatetraitscanbehardtousesystematically,sincetheyrequiredetailedetymologicalknowledge.In
English,forexample,withoutmedievaldataacognatetraitwouldbemissedbyanyonewhodidnotknow
thatthesecondmemberofthecompoundbridegroomisthecognateofGothicguma‘man’;thecognateof
Sanskritmádhu-‘honey’wouldbemissedwithoutlexicaldatathatincludedtheinfrequentwordmead.Afur-
therproblemintheanalysisofcognatetraitsistodeterminewhichwordscountas‘descendedfromthesame
ancestralwordform’.InRomance,forexample,Latinneuterschangegender,andsimplexverbsareoften
continued by their frequentatives. Presumably Italian rapa ‘turnip’counts as the ‘same’as Latin rāpum,
thoughrapastrictlyspeakingcontinuesapluralrāpareinterpretedassingular;butisFrenchchanter<Latin
cantāre‘sing(repeatedly)’the‘same’asLatincanere‘sing’?Statisticalanalysesofroot-meaningtraitsneed
notseekinvainforaprincipledwaytountiesuchGordianknots.
202 LANGUAGE,VOLUME91,NUMBER1(2015)
Latinhasatrait[*serp-,‘snake’].LanguagescanshareanRMtraitbasedonformswith
different derivations, like English feather < *pet-trā (or *pet-rā) and Latin penna
‘feather’<*pet-nā.Thesewordssharearootbutarenotcognatewords,sincetheywere
derivedwithunrelatedsuffixes*-trā(or*-rā)and*-nāandsocannotdescenddirectly
fromthesameancestralwordform.Bycontrast,becausethecognatewordstimberand
Zimmerhavedifferentmeanings,theydonotdefineasharedRMtrait.
Homoplasyanddrift.
2.1. CognateandRMtraitsevolveverydifferently,especially
withrespecttohomoplasyorindependentinnovation.11Exceptinborrowingbetween
languages,cognatetraitsordinarilycomeintoexistenceonlyonce;thisisthebasisofthe
comparativemethod
(Meillet1925,Weiss2014).Thereforemodelsoftraitevolution
thatdonotpermithomoplasyarewellsuitedtocognatetraits.Butbecausethemecha-
nismsofchangeunderlyingRMtraitsincludesemanticchangeandthederivationofnew
wordsfromexistingforms,RMtraitsaresubjecttoatleasttwodistinctivekindsofho-
drift
moplasy.Indescribingthem,weadaptSapir’s(1921)term ,whichreferstothepre-
dispositiontoundergocertainchangesgivencertainprecursortraits.
First,RMtraitsarisenotonlywhenwordformscomeintoexistence,butalsowhen
they change meanings. For example, Old English (OE) timber probably originally
meant‘building’(likeOldSaxontimbar);tomodelitsshiftinmeaningto‘timber(ma-
terial for building)’, the trait [*demh -, ‘building’] would be said to be replaced by a
2
trait [*demh -, ‘timber’].12 Meaning changes fall into recurrent patterns across lan-
2
guages (Heine & Kuteva 2002, Traugott & Dasher 2002, Urban 2014). If the same
meaningchangeaffectsthesamerootinrelatedlanguages,ahomoplasticRMtraitre-
sults. For example, in a crosslinguistically common shift (Wilkins 1996), reflexes of
PIE*pod-‘foot’cametomean‘leg’independentlyinModernGreekandmodernIndic
andIranianlanguages.Twootherexamplesfromourdatasetaregivenin1.
(1) a. Old Irish seinnid meant ‘play or strike an instrument, sound’ but has
shifted in Modern Irish and Scots Gaelic to mean ‘sing’. The ancestral
root *swenh - referred to producing sound or music more generally, but
2
thesamesemanticshiftto‘sing’isseeninPersianxvāndan.
b. Manylanguagesdistinguishastative‘sit’verb(‘beinasittingposition’)
from a change-of-state one (‘sit oneself down, take a seated position’),
butshiftsbetweenthesensesarecommon.InPNIE,theroot*h eh s-ex-
1 1
pressedthestativesense,while*sed-expressedthechange-of-statesense
(Rixetal.2001).Change-of-state*sed-cametoexpressthestativesense
independentlyinArmenian,Balto-Slavic,Celtic,Germanic,andItalic,a
shiftnotsharedbyGreekorIndo-Iranianandthereforeindependentinat
leastsomeofthebrancheswhereithappened.
Recurrentmeaningchangeslikethesehavebeencalled‘rampant’inlanguage(Ringeet
semanticdrift
al.2002).Forsuchchangesweusetheterm .
11Homoplasyisanevolutionarytermforindependentanalogousinnovationinparallellineages.Changes
likethet>ksoundchangethathasoccurredindependentlyatleasttwentytimesinAustronesianlanguages
(Blust2004)aresaidtobehomoplastic.
12Wewriteasiflatermeaningssimplyreplaceearlierones.Inreality,asinthiscase(OldEnglishhadboth
meanings),wordsusuallypassthroughapolysemousstage,whichwouldbemodeledasthecoexistenceof
traits(e.g.[*demh2-,‘building’]and[*demh2-,‘timber’]).Themethodologyofbasic-vocabularywordlist
collection tends to suppress all but the clearest cases of polysemy in the languages under study, but this
shouldnotaffecttheanalysisaslongasthemethodisthesamethroughoutthedataset.
Ancestry-constrainedphylogeneticanalysissupportstheIndo-Europeansteppehypothesis
203
derivational drift
Asecond source of homoplasy in RM traits is . This refers to
changethatoccursbecausecertainrootsaresemanticallywellsuitedtoprovidecertain
derivatives.Forexample,constructionsthatmean‘causetodie’arearecurrentsource
ofverbsfor‘kill’(Buck1949).Therefore,asdescendantsofPIE*gwhen-‘kill’fellout
of use, causative derivatives of PIE *mer- ‘die’were used in this meaning. This hap-
pened independently in Irish and in modern Indic and Iranian languages (Rix et al.
2001), yielding a homoplastic RM trait.13Three other examples from our data set are
givenin2.
(2) a. Becausewordsfor‘animal’oftenevolvefromexpressionsmeaning‘hav-
ingbreath’andsoforth,PIEh enh -‘breathe’isseeninseveralotherwise
2 1
unrelated ‘animal’ terms. Latin animal itself is a derivative of anima
‘spirit’, a derivative of h enh -. In Indo-Iranian, Persian jānvār ‘animal’
2 1
andrelatedformsdescendfrom*wyāna-bāra-‘havingaspirit’,inwhich
*wyāna-isaderivativeofh enh -.Andthoughnotthebasicwordfor‘an-
2 1
imal’, Tocharian B onolme ‘living being’is also a derivative of h enh -
2 1
‘breathe’(D.Adams2013).
b. Basic words for ‘live’ include derivatives of the PNIE root *gwyeh -:
3
Greek zdõ, Classical Armenian keam, Latin vīvō, and so forth, all of
͜
whichareprimaryverbalformations.BasicCelticwordsfor‘live’inour
datasetarederivativesofanadjective*gwih -wo-thatwasderivedfrom
3
thesameroot,thatis,aconstruction‘bealive’.Itisnaturaltoderiveasta-
tiveverb‘X’fromaconstruction‘beX’(withastativeadjectiveX).
c. In the meaning ‘snake’, reflexes of the PIE noun *h ógwhis are wide-
1
spread (Ancient Greek óphis, Vedic Sanskrit áhi-, etc.). A verb *serp-
‘crawl’alsooftenrefersspecificallytothemotionofasnake.Derivatives
of *serp- came to be the general term for ‘snake’inAlbanian, in Latin
(and modern Romance languages), and in modern Indo-Aryan (IA) lan-
guages,forexample,Hindisālp,Assamesexāp.Thehomoplasticnatureof
suchcasesisshownbythefactthatthevariouswordformsthatacquire
the new meaning are often formed with different derivations. For exam-
ple, thoughAlbanian (Tosk) gjarpër ‘snake’and Latin serpens are both
based on the PIE root *serp-, theAlbanian noun is formed with a suffix
*-ena-(Orel1998)andtheLatinnounwithadifferentsuffix*-ent-.The
wordformsthemselvesdonotgobacktoasingleancestor.
In short, though some analysts erroneously assume that RM traits are homoplasy-
free(Atkinsonetal.2005:204,Grayetal.2011:1094),semanticandderivationaldrift
areendemicinRMdatasets.Thisclaimisfurthersupportedin§3belowandquantified
in§4.2.14
13Derivationaldriftcanbeunderstoodasresultingfromthesemanticdriftofderivativewords.Forexam-
ple,thederivationaldriftwhereby‘causetodie’replaces‘kill’canbeviewedasaconsequenceofsemantic
changeintheseverbs.Itisnonethelesshelpfultodistinguishthetwocategorieswhenpossible.
14Athirdkindoflexicaltrait,intermediatebetweencognateandRMtraits,wouldencodewhetherwords
forgivenmeaningsareexpressedbycognatewordforms,ratherthanroots.Suchtraitswouldhaveevolu-
tionarypropertieslikethoseofRMtraits,sincetheywouldbeliabletosemanticdrift(thoughnotderivational
drift).TheseareevidentlythetraitsanalyzedbyBowernandAtkinson(2012),whoreportthat‘wordswere
notcountedascognate…iftheywerepresentinthelanguageinadifferentmeaning’(p.827).Theyalso
writethat‘languagesarehighlyunlikelytoindependentlygainthesamecognate’(p.829),whichistruebut
irrelevant,since(astheyimplicitlyacknowledgebynotingthatcognatescanhavedifferentmeanings)the
traitstheyanalyzearesusceptibletosemanticdrift.