[PDF] From the Cover: Earliest evidence of modern human life

New fossils from Jebel Irhoud, Morocco and the pan-African

New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapiens Jean-Jacques h ublin 1,2 , Abdelouahed Ben-n cer 3 , Shara E Bailey 4 , Sarah E Freidline 1 , Simon n eubauer 1 , Matthew M Skinner 5 ,

ORIGIN OF MODERN HUMANS - University of Notre Dame

JEBEL IRHOUD 1 MOROCO 100,000 –200,000 YEARS OLD H erectus or France Homo erectus Homo neanderthalensis Homo sapiens 15 RECONSTRUCTION BASED ON SKULLS FROM

PALEOANTHROPOLOGY The earliest modern humans outside Africa

France 12Institut de Recherche sur les Archéomatériaux, UMR 5060 CNRS - Université d e Bordeaux Montaigne, modern humans and near to Jebel Irhoud It

SAPIENS - downloadsalesartetv

as Irhoud 1 and 2 In 1982, the 2 skulls unearthed at Jebel Irhoud were returned to Morocco: on the occasion of King Hassan II’s birthday, Yves Coppens was sent as a French envoy to present the fossils to him 20 years after its initial discovery, the Jebel Irhoud man had finally been confirmed to belong to the Homo sapiens species

From the Cover: Earliest evidence of modern human life

descriptions of the hominins from Jebel Irhoud (Morocco) emphasized similarities with Neanderthals; however, recent analyses demonstrate a number of synapomorphies shared with modern humans, establishing the presence of H sapiens sensu stricto in North Africa 130,000–190,000 years before present (ybp) (1)

Timeline for Homo sapiens - 3rd Edition

300,000 B C E +/- 20,000 years Jebel Irhoud (Morocco) Jawbone of oldest homo sapien 74,000 B C E La Ferrassie (France) Male/Female/Juvenile Neanderthal (Image

The Origin of Us - NYCEP

A Homo sapiens cranium from Jebel Irhoud, Morocco, dating from about 315,000 years ago, is the earliest known fossil of our species Chris s tringer/ n atural h istory Museu M l ondon Chris s tringer/ n atural h istory Museu M l ondon Chris s tringer/ n atural h istory Museu M l ondon 19-22 NH OShea 918 indd 20 8/6/18 11:59 AM

Curriculum vitae - Max Planck Society

2018 Keynote Speech - International Symposium, Collège de France, Paris (France) 2018 Jebel Irhoud et l’origine d’Homo sapiens, Grands Séminaires du Musée de l'Homme, Paris (France) 2018 Le premier de notre espèce, Musée de Nemours, Paris (France) 2018 Conference, University of Geneva, Geneva (Switzerland)

O ORÁCULO DA NOITE S RIBEIRO - GostodeLer

“New Fossils from Jebel Irhoud, Morocco and the Pan-African Origin of Homo sapiens” Nature 546, pp 289-92, 2017; Richter, D e outros “The Age of the Hominin Fossils from Jebel Irhoud, Morocco, and the Origins of the Middle Stone Age” Nature 546, pp 293-6, 2017 2 Pike, A W e outros “U-Series Dating of Paleolithic Art in 11

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Homo sapiens

From the Cover: Earliest evidence of modern human life history in North African early

Boutakiout, and Jean-Jacques Hublin

Tanya M. Smith, Paul Tafforeau, Donald J. Reid, Rainer Grün, Stephen Eggins, Mohamed doi:10.1073/pnas.0700747104

2007;104;6128-6133; originally published online Mar 19, 2007; PNAS

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Notes:

Earliestevidenceof modernhumanlife history

inNorthAfrican earlyHomosapiens

TanyaM.Smith*

,PaulTafforeau ,DonaldJ. Reid ,RainerGru ¨n ,StephenEggins ,MohamedBoutakiout**, andJean-JacquesHublin*

*DepartmentofHuman Evolution,MaxPlanck InstituteforEvolutionary Anthropology,DeutscherPlatz 6,D-04103 Leipzig,Germany;

Laboratoirede

Ge´obiologie,BiochronologieetPale´ontologieHumaine,Unite´Mixtede Recherche6046,Centre Nationalde laRechercheScientifique, Universite´de

Poitiers,40 AvenueduRecteur Pineau,86022Poitiers Cedex,France; EuropeanSynchrotronRadiation Facility,6 rueJulesHorowitz, BP220,38046

GrenobleCedex,France;

DepartmentofOral Biology,Schoolof DentalSciences, NewcastleUniversity,Framlington Place,Newcastleupon Tyne

NE24BW,United Kingdom;

ResearchSchool ofEarthSciences, AustralianNationalUniversity, CanberraACT0200, Australia;and**Department of

Geology,Facultyof Sciences,UniversityMohammed V-Agdal,Avenue IbnBattouta,BP 1014,Rabat,Morocco

CommunicatedbyRichard G.Klein,Stanford University,Stanford,CA, February1,2007 (receivedfor reviewDecember12, 2006)

Recentdevelopmentalstudies demonstratethatearly fossilhomi- ninspossessedshorter growthperiodsthan livinghumans, imply- ingdisparatelife histories.Analysesof incrementalfeaturesin teethprovidean accuratemeansof assessingthe ageatdeath of developingdentitions,facilitating directcomparisonswith fossil andmodernhumans. Itiscurrently unknownwhen andwherethe prolongedmodernhuman developmentalconditionoriginated. Here,anapplication ofx-raysynchrotron microtomographyre- vealsthatan earlyHomosapiensjuvenilefromMorocco datedat

160,000years beforepresentdisplays anequivalentdegree of

toothdevelopmentto modernEuropeanchildren atthesame age. Crownformationtimes inthejuvenile's macrodontdentition are higherthanmodern humanmeanvalues, whereasrootdevelop- mentisaccelerated relativetomodern humansbut islessthan livingapesand somefossilhominins. Thejuvenilefrom Jebel Irhoudis currentlytheoldest-known memberofHomowitha developmentalpattern(degree oferuption,developmental stage, andcrownformation time)thatis moresimilar tomodernH. sapiensthantoearlier membersofHomo.This studyalsounder- scoresthecontinuing importanceofNorth Africafor understand- ingthe originsofhuman anatomicalandbehavioral modernity. Correspondingbiologicaland culturalchanges mayhaveappeared relativelylate inthecourse ofhumanevolution. dentaldevelopment?humanevolution?humanorigins ?synchrotron microtomography?toothgrowth B ecauseofincreasing eviden ceofsophisticatedmaterial culture,newfossilmateri al,andref ineddatingtechniq ues, humanoriginsin Africa,inparticulart heques tionofwhenearly

Homosapiens

becamefullymodern(1-6).Whereascranialand dentalfeaturesdemo nstratethatAfricanMiddl ePleistocene form(i.e.,Homoheidelb ergensis/Homorhodesi ensis)to arela- inthe timingofs omaticdevelopment ,repro ductivescheduling, orlife span(7).Analysesofdenta ldevelopment ,molareruption, andageatd eathbase doninc rementalfeature softhedentitio n arethemos taccurat emeansofiden tifyingdevelopmental changeinthehumanfo ssilre cord(7-1 0). Studiesofdentaldevel opment inearlyHomodocumentalife historypatternmoresim ilartoAfricanapestha ntomodern humans(8,10),andre searchonb raingrowthi nHomoerectus alsosuggest sashorterperiodofearlyd eve lopmentthanisseen inmode rnhumanpopulations (11).Aspectsof H.heidelbergen- sis,Homoantecess or,an dHomoneandert halensisanteriortooth developmentalsodifferwhencompare dwithUpperPa leolithic/ Mesolithicpopulations(12),alt houghNeanderthalmolardevel- opmentmaymoreclose lyresemb lethatofmode rnhumans(13). Recentworkonasingl epermanentN eander tha lmolartooth reportedashortercrownfo rma tiontimethanmodernhu mans, butsimil arratesofrootextensio n;thiswasinter preted as evidencethatlifehistory wassimilarb etweenNeande rthalsand modernhumans(13).H owever,overlapinm olarcrownforma- tiontimesand rootextensionra teshaveb eenfoundbetw een chimpanzeesandhumans(10,14),desp itediffe rencesinlife historyscheduling.Fu rthermore,itisstillunknownwhenNe - anderthalserupttheirfirstmola rs,aneventwhich ishighly correlatedwithotherlifehistor yvariables(7 ).Inshort,give n welldocument edtechnologicalinnovationsdur ingthePleisto- cene,dietarych angesduringtheHolocen e,anddentalreduction inmode rnpopulations,itis unclearwhetherdentaldevelopment mayhaveun dergonecorre spondingchanges,andwhenthe unique,prolongedmode rnhumanpatternofgrowthandd evel- opmentoriginated( 7,10). NorthAfricanMi ddleandearlyUpperPlei stocenehominins aretypica llycharacterizedashavingma crodontdentitionsand aco mbinationofprimitivetraitsshare dwithe arlyHomoand derivedtraitssharedwi thlaterHomo,in cludingH.sapiens.Ea rly descriptionsofthehomininsfromJebelI rhoud( Morocco) emphasizedsimilaritieswithNea nderthals;however,recent analysesdemonstrateanumb erofsynapomorphiessharedwith modernhumans,estab lishingthepresenceof H.sapienssensu strictoinNort hAfrica130,000 -190,000yearsbefor epresent (ybp)(1).Theju venileindivi dualfrom JebelIrhoud(Irhoud3) isrepr esentedbyawellpreservedmandible( 15)tha tda tesfrom justlessthan thegeologica lagesofthee arliestev idenceforearly H.sapiensinEast Africa(5).Re centdirecturanium series/ electronspinresonancedat esonthespec imenconfirmearlier dates,suggestingan ageof160,000?16,000ybp[supporting information(SI)MethodsandSIFigs .4-6].This studyaimedto characterizedentaldevelopmentandag eatdeathinIrhoud3, andtocom pareit withfossilhomininsan dlivin ghuman populationstodeterminewhetherthe modern humancondition ofprol ongeddentaldevelopmentwasp resent.Thepreserva tion Authorcontributions:T.M.S., P.T.,andJ.-J.H. designedresearch;T.M.S., P.T.,D.J.R., R.G., andS.E.performed research;M.B.and J.-J.H.contributednew reagents/analytictools;

Theauthorsdeclare noconflict ofinterest.

Freelyavailable onlinethroughthe PNASopenaccess option. Abbreviations:Phasecontrast SR-mCT,Phasecontrast X-raysynchrotronmicrotomogra- phy;ybp, yearsbeforepresent.

SeeCommentaryon page6093.

Towhomcorrespondence shouldbeaddressed at:Departmentof HumanEvolution,Max PlanckInstitutefor EvolutionaryAnthropology,Deutscher Platz6,D-04103 Leipzig,

Germany.E-mail:tsmith@eva.mpg.de.

Inthisarticle, earlyH.sapiensincludesAfricanfossils postdating200,000ybp thatare variablyreferredto as''ancestorsof modernhumans,''''early anatomicallymodern humans,''or''early modernhumans''(1- 6). Thisarticlecontains supportinginformationonline atwww.pnas.org/cgi/content/full/

0700747104/DC1.

©2007by TheNationalAcademy ofSciencesof theUSA

6128-6133?PNAS?April10,2007 ?vol.104?no.15www.pnas.org ?cgi?doi?10.1073?pnas.0700747104

ofaner uptedf irstmolar,eruptingla teralincisorand unerupted canine,andtheapplicat ionofhig h-resolut ionpropagationphase contrastx-raysynchrotron microtomograph y(phasecontrast SR-mCT)(16-18),facil itatesaccuratenondestru ctiveestima- tionoftheag eatdea th,suchth atthissp ecimen representsthe earliestmemberofH.sapiensforwhicht hetimingoftooth eruption,durationofcrownfo rmation,andschedulingofl ife historymaybeinferred. Toothdevelopme ntischaracterizedbyfeaturesrepre sentin g subdaily,daily,supradaily, andannualrhythmspe rmanently recordedinhardtissuesof thecro wnandroot(r eviewedinref.

19).Estimat esofcrownformationtimeanda geatde athbased

onthes eincrementalfea turesmayyieldhighlyaccurateresul ts fromhistolog icallysectionedmaterial(9).Thedurationof enamelformationis typicallyassessedbycountso flong- period lines(Retziusl inesinternallyorperikym ataexternally)m ulti- pliedbytheirper iodici ty(numberofdai lycross-striationsbe- tweensuccessive Retziuslines),whichisaddedtoa nestimateof cuspalenamelformat ionbasedonlineart hicknessandsecretion rates.Thisstudyrep resentsthem ostcomprehensiv enondestruc- tiveassessme ntofcrownformationinasinglefo ssilho minin specimen,combiningdataonex ternalincrementalfeatures (perikymata)withinternalvariables(c uspalenamel thickness andlong-p eriodlineperiodicity)derivedfrom high-resolu tion laboratorymicrotomographyandp hasecontrastSR-mCT.This uniquenondestructi veapproachyieldscrownformationtimes previousstudiesoffossil hominins(e.g.,refs.8 ,12,an d20-23).

Results

Perikymata(Fig.1)wereevidento nthesurfaceofth eIrhou d3 lowerrightlate ralincisor,lowe rleftcanine,andmesio buccal cuspofthelo werlef tmolar.Th eperiodicityof long-period incrementalfeatureswas10daysinth isindividual(Fig.2andSI

Fig.7),dete rminedfromphasecontrastSR-mCT .Dataon

perikymatanumber,cuspalenamel thickness,andcrownfo rma- tiontimefor eachofthethr eepermane ntteethareg ivenin Table1.Crownfor mation timeswereestim atedtobe5.13,6.68, and3.96ye arsforthelow erlateralincis or,canine ,andmesio - buccalcuspofthefi rstmolar,res pecti vely.Twen typeriradicular bands,whicharebeli evedtobeequiva lenttooth erlong-period lines(23-25),we recountedonthecanineroo tfromtheendo f was200day s.Theagea tdeath,determi nedbyaddi ngtheageo f modernhumancanine initiation(26)t othedurationofcan ine crownandrootfo rmationob servedinthis specimen,was7.78 years(2,839days ).Initiationageso fearly-formingteet hdonot seemtovarygr eatlyb etweenmoder nhumansandchimpanzees ; becauseinitiationage sinbothtaxaarequitesimilarfor early- formingteeth[lesstha nafewdaysto?2mo nthsapartdepend- ingontoot htype (26,27)],theuse ofthemodern humanvalue forthisva riableisunli kelytogreatlyaffectthea ccurac yof estimates.

Fig.1.Uneruptedlowerleft caninegermof theIrhoud3 juvenile.(A)Stereomicroscope overviewwithposition ofareaenlarged inB(whitebox)and virtual

Labialrootlength estimatewas madebyprojecting thecurvaturesof thedevelopingroot coneandthe enamel-dentinejunction.(Scale bars:2 mminAand

Cand0.2mm inB.)

Smithetal.PNAS?April10,2007 ?vol.104 ?no.15?6129

ANTHROPOLOGY

SEECOMMENTARY

premolarsandthesecondperma nentmolar hadcomple ted crownformation andhadjustbegunrootformatio n(Fig.3) . ComparisonswithmodernEuropeanpop ulationsatas imilar developmentalstage(lowersecondpremolar andsecondmolar rootinitiati on)suggestsanaverageageof7.2-7.3 yearsfora femaleor7.3-7.6yea rsfora malejuvenile(28).Thi sresultis consistentwiththestageoflater alincisor(I2 )eruption ,which isafew mms hortofbe ingina fullyeruptedpos ition ;modern EuropeanI2eruptiontypica llyoc cursbetweensevenandeight yearsofage(29). Thus,t heIrhoud 3juvenileseemst ohavea developmentalstagequitesimilartoaverag emodernEuropean children.

Discussion

Thenondes tructiveapplicationofphasecontrastSR-mCT to determinelong-periodlinepe riodicityrepresentsavaluabletool forstudie sofdentaldevelopment .Uncer taintyaboutthisvar i- ablehashisto ricallyle dtobroadconfidenceintervalsforesti - matesofhominin crownf ormationtimes(e.g.,re fs.8,21,and

22),complic atingcomparisonswithmodernhumanpopu lations.

Thelong- periodlineperiodicityof10inIrhou d3isthehighe st valueyetreporte dinafossi lhominin;thishighvaluem aybe relatedtoitslargebody and/or toothsiz e.Long-periodli ne periodicityinmodernhumansishighl yvaria ble;arecentstudy of365m odernhuma nsfoundameanvalue of8days,witha rangeof6-12day s(14). Perikymatanumberswerehigherth anmeanvaluesforequiv - alentteethofear lyEastAfricanf ossilHomo,so uthernAfrican MiddleStoneAgeH.sapiens,H.neanderthalensis,an dtwo modernhumanpopulat ions(Table2),b utwerenotoutsidethe Europeanpopulationrangef ormodernhumans.Comparisons betweenthecuspalenam elthickne ssofIrhoud3andmod ern humansdemonstrate similarities(14,30,31),althought he Irhoud3permanentte eth haveslightlythinnercuspale namel.

Crownformationt imesinIrhoud3arehigherthan modern

humanmeans,exc eedingknownrangeso fthetwomodern humancomparativ esamples.Theincisorandcanineform ation timesaremoresim ilartomod ernEuropean sthantosouthern Africanpopulationsofm odernhumans(31),unlikethemore rapidpatternre portedforNeanderthals (21).Globalvariationin histologicallydeterminedcrownformationtim esispoorlyun- derstood,forexamplemodernJ apanesede ntitionsmayform overanevenlo ngerpe riodthantheI rhoud3individual( 32). Longcrownfo rmationtimesinI rhoud3maybedueinpartto theabsolu telylargesizeoftheteeth,which arelargerthanm any macrodontfossilhominins(15) .CanineheightinIr houd3(13.6 mmvert icalheight,15.0mmcurvil inearlength)isgreater than meanvaluesfo rH.heidelbergensis,H.neanderthalensis,H.an- tecessor,Up perPaleolithic/ MesolithicH.sapiens,an dlivingH. sapiens,in manyca sesoutsideof 95%confidencei ntervals(12,

31).Thefind ingoflong crownformationtimesi namacr odont

hominindentitionisno tunexpected;giventhatsecre tionra tes seemtobefai rlycon strain edamongapesandhum ans(e.g.,refs.

8an d14),incr easingthedur ationofcrownformationmaybe

necessarytoformlargerteeth, sugge stingthatcro wnformation timealonemay notbeareliable predictor oflifehis tory. Evidenceoftootheruptiona gesand theattainmento fdevel- opmentalstagesrepresent morerobustmarkers oflifehistory (7),providin gstrongevidenceforaprolong edlifehistoryinH. sapiens160,000yearsago. Thefossil recordofearlyrepr esentativesofH.sapiensis difficulttointerpretbecaus eofthe lackofsecuredatesandthe mosaicofprimitivea ndderi vedfeaturesfoundonmanyofth e wellpreserv edfossils(6).Giventhestron ggeneticcomponentto dentaldevelopment( reviewedinref.33),aswellasthehig h correlationwithotheraspectsoflif ehistory(7), evidencefrom dentaleruptionand toothgrowthrepresentsaro bustchar acter fortheid entificat ionofmodernhumansintheMiddleorearly UpperPleistoce ne.RelativelyfewcontemporaneousAfri can specimenshavethepotentialt oprovideinfo rmationa bout dentaldevelopment. AnexceptionistheEastAfricanHerto Fig.2.Enamelmicrostructurein anincisor fragmentfromIrhoud 3.(A) Virtualsection(70 ?mthick)of labialenamelgenerated byusing phase contrastSR-mCT. (Scalebar:0.5 mm.)(B-D)The enlargedareasfrom topto bottomshow dailycross-striations(light anddarkbands crossingdiagonal enamelprisms)in thelateralenamel (B),theperiodicity ofRetziuslines :10 dailycross-striations(small arrows)between successiveRetziuslines (large arrows)(C)(seealso SIFig.7 ),andan areaofcervical enamelshowing accentuatedlines andslightprism decussation(D). child(BOU-VP-1 6/5)(4),whichpreservesamaxillarydentit ion atasim ila rdevelopmentalstagea stheIrhoud3mandible. Althoughnumerousjuvenil eNeanderthaldentitionsh avebeen recovered,ageatdeathassignmen tshaveof tenbee nbasedon comparisonwithmodernEuropeand evelopmenta lstandards (34),whichmayb einappropriatei ftheyhave amore accelerated periodofdentaldev elopme ntthanUpperPaleol ithic/Mesolithic humans(12)ormodern Europeans(3 5).The applicationof phasecontrastS R-mCTallowsforgreaterre solutionofthis issue,asitisnowpo ssible tonond estruc tivelyde terminethe long-periodlineperiodicityvalues offossilhom inindentitions. Becauseofthepermanent develo pmentalr ecordspreserved intee thandtheirpoten tialforid entifyingdevel opmentalchange intheh umanfossi lrecord,theinn ovativestudiesofDe anand colleagues(e.g.,8,10,13,20,23 ,35)havesubstantia llyalt ered reconstructionsoffossilhomininontogeny,poin tingto differ- encesamongmembe rsofthegenusHomo.T hisisfurther supportedbysuggestionsofsh ortant eriortoothformationtimes Table1.Crown formationtimesand ageat crowncompletionin themandibularpermanent teethof Irhoud3

ToothPKPer LTThickMin CTMaxCT CFTInitAge

I2167 101,670645 1702341,872 1462,018

C21710 2,170885233 3052,439200 2,639

M111410 1,1401,080263 3501,446 ?181,428

I2,rightlateral incisor;C,left canine;M1,mesiobuccal cuspofthe leftfirst molar;PK,perikymata number;Per,

periodicity(numberof dailycross-striationsbetween long-periodlines);LT, lateralformationtime indays; Thick,

cuspalformation timeindays; CFT,crownformation timeindays; Init,initiationage indays;Age, ageat crown

formationin days.

Fig.3. Themandibulardentition oftheIrhoud 3juvenile;crowns areinwhite, rootsin yellow.(AandB)Virtualmandible showingthe dentitionfromanterior

(A)andlateral (B)perspectives,with thedentitionvirtually extractedinsitu ontheright. (C)Isolatedand virtuallyextractedteeth inlabial/buccal orientation

ontheleft andocclusalorientation ontheright (teethleftto right:rightlateral incisor,left canine,leftfirst premolar,leftsecond premolar,leftfirstpermanent

molar,leftsecond permanentmolar).Bright whitespeckles arefroma densemineralthat invadedthemandible duringfossilization.(Scale bars:2 cm.)

Smithetal.PNAS?April10,2007 ?vol.104?no.15?6131

ANTHROPOLOGY

SEECOMMENTARY

inH.antecessor,H.heidelbergensis,an dH.neanderthalensis(12), Thejuveni lemandiblefromJebelIrho udis,atpresent,the oldest-knownmemberofHomotoshow apatternofer upt ion andperiod ofdentaldevelopme ntmore similartomodernH. sapiens.Th isextendedpe riodofdevelopment,andby implica- tionchildhoo d,impliestheadventofcorrespon dingsocial, biological,andculturalchangesnec essarytos upporthighly dependentchildrenwithprolo ngedopportunitiesforsoc ial learninginearlychildhoo d(7,11 ,36).

MaterialsandMethods

Perikymatacountsweremadeonthe eruptinglowerright lateral incisor,uneruptedlowerle ftcanine,anderuptedlowerle ftfirst molar(mesiobuc calcusp)byusingstereomicroscopyatam ag- nificationof?50;thecan inewasis olatedasthemandibl ewas fracturedthroughthecaninec rypt,permittingphysic alextrac - tion(15).The long-periodlin eperiodic itywasdeterminedfrom afr agmentofthepermanentinc isor(F ig.2andSIFig .7)im aged ata0.7 -?mvo xelsizebyusing phasecontras tSR-m CTper- formedwithbeamlin eID19attheEu ropeanSynchrotron RadiationFacility(Grenoble ,France).Lateral(imbrica tional) ofperi kymatabytheperiodicity.Cuspal ename lthicknes swas determinedfrommicrotomographi cslices(det ailedbelow); measurementsweremadefromthetipofth edentinehorn tothe approximatepositionofthefirstper ikymataatthecuspsurface (Fig.1). Cuspalformationti mewascalculatedbytwodiffer entmeth- odsandan averageva luewas determined.Aminimume stimate wascalcul atedascuspalthicknessdividedb ythem odernhuman meancuspald ailysecretionrate: 3.80?m/dayforanterio rteeth (37)and4.11 ?m/dayformolarte eth(14).I twasnotpossibl eto directlyquantifycuspalda ilysecretionratesinIrho ud3asonly thelabial enamelfragmentoft heincisorwasimaged withphase contrastSR-mCT.However,g iventhesimilarityofm eancuspal ratesbetweenhum ans,chimpanzees,andN eanderthals(13,14), estimatesderivedfrommodern humanpopulationsareun likely toaffe ctaccuracy.Amaximu mcuspalformationtimeestima te wascalcul atedwithregressionequationsfo rmodernhuman teeth.Crownformati ontimewascalcu latedbyaddingthelateral enamelformationtim etotheaverageofthetwometho dsfor cuspalformationti meestimation.Ageatcrowncom pletionwas determinedbyaddingmodernhumani nitia tionages(26)tothe durationofcrownformation time. Caninerootformati onwasdetermi nedbyfollowinganac- centuatedperiradicularband ,formedjustaftercrowncomple- tiononthelab ialsur face,tot helongestportionof theroot preservingtheentiredeveloping surface(o ntheoriginalspec- imen);countswerema deoflong-periodpe riradicularb ands (23-25)fromtheaccentu atedbandtot heendofro otformation, andthisnu mberwasmulti pliedbytheperiodi cityoflon g-period linesdetermine dfromenamel(10days)toyieldroot formation indays .Labialcaniner ootlengthwasestima tedfromthe originalspecimenandmCTsl ices,andaslightcorrecti onwas madeforthefr acturedde veloping surface(Fig.1).Theesti- matedcanineroot lengthof1.56mmwas dividedbythe duration ofform ationtoyieldanaverageexten sionra teof7.8?m/day. Thisrateisa pproximately twicea shighasthatfoundinasmall sampleofrecenthuma ns(SITabl e3)an dsuggests that,relative tomode rnhumans,thedentit ionofIrhoud3showedal ong crownformation andarapidrootextension,lead ingtosim ila r agesattoothe rupti on.Ageatdeathwa sdeterminedasthesum ofagea tcaninec rownco mpletionandthedura tionofroot for11mmof lower latera lincis orrootas13.4?m/day,and9.6 ?m/dayforthefirs t13.5mmof thefirst molarroot.These values areinterm ediatebetweenthoseforlivingandfossi lhominins(8,

10,13)and explainh owteethwi threlativelylongcrow nforma-

tiontimesma yeruptatthesame ageasmod ernhumans.

Themandib lewasscannedbyusingaBIR Actis300/ 225

microtomograph[Bio-ImagingResearch,Inc.(B IR),Lincoln- shire,IL]atanisotr opicvoxe lsizeo f109?m,andt hedevelo ping microtomograph(Kontich,Belgium),performe dattheMax PlanckInstitutefo rEvolutionaryAnthropologyin Leipzig, Germany.Virtualextracti onofthemandibulardent itionwas performedbyusingVGStudioMa x1.2.1 software(Heidel berg, Germany).Foreachtooth,enam elanddent ineweresegme nted byusin gthe3Dmagicwand regiongr owingt oolorbymanual segmentation.Athree-pixelGaussianfilt erw assubsequently appliedtoeachsubvolu metoob tainasmooth 3Drendering. Densemetallico xideparticleswerepartial lyremovedbymod - ifyingtherenderin gramp;the whitestpartsofthesliceswer eset tozero .Insomecases,it wasno tpossibletor emovetheoxide particleswithoutalteringth esurfaceoftheteeth(Fi g.3),which wasavoide d. Wegive specialthan kstoDebbieGuatelli-St einberg,AnthonyOl ejnic- zak,Fernando RamirezRozzi,GinaStedin g,HeikoTemming,Andre as Winzer,MonsieurleDoye ndelaFaculte´de sSciences ,theUniversityof Rabat,theGermanEm bassyinMo rocco,theGovernme ntofMorocco, Table2. Long-period(incrementalline) numbersandcrown formationtimesin livingandfossil Homo Taxon

LPCFT, days

NLI2LCLM1 LI2LCLM1

EarlyHomo2-392-113110 - 893-1,2921,142-1,362 -

H.neanderthalensis5-10151(22) 159(15)92 (16) - - 1,041

Irhoud31 167217114 1,8722,4391,446

MSAHomo2 - - 94 - - 1,128

ModernEUR6-13 130(19)199 (22)92(14) 1,376(46)2,066 (73)1,160(34) ModernSA6-23 111(12)155 (24)93 (10)1,224(25) 1,712(47)1,161 (31)

IntheTaxon column,thefollowing applies:EarlyEast AfricanHomo(8);Neanderthaldata arefrom refs.13and 21andfrom D.

Guatelli-SteinbergandD.J.R., unpublisheddata;MSA HomoareMiddleStone Agehumans(22); ModernEURare modernclinically

extractedteeth fromNewcastle,U.K. (14,30,31). ModernSAare extractedmodernhuman teethfroma skeletalcollection ofmixed

SouthAfricantribal populations(14,30, 31).N,samplesizes, whichvariedwithin taxafortooth typesanddevelopmental variables;LP,

long-periodlinenumbers, eitherperikymata fromexternalsurfaces orRetziuslines fromhistologicalsections ofmodernteeth. LI2,LC,

andLM1, lowerlateralincisor, lowercanine,and lowermolarmesiobuccal cusps,respectively;CFT, crownformation time,determined

valuesderived fromhistologicalsections. Numbersinparentheses representstandarddeviations whengiven. onthi sproject.All isonCleveland,AnthonyOl ejniczak,GarySchwartz , andtwoan onymousre viewersprovidedhelpfulcomm entsonthe manuscript.Fundingwassuppliedbyt heMaxPlanckSociety,E uropean VirtualAnthropologyM arieCurieResearchTrainingNetworkMRT N- CT-019564,theCentreNationaldel aRecherc heScientifique,and the

EuropeanSynchrotronRadi ationFacility.

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