Article pp.110-134 du Vol.27 n°3-4 (2015)

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ARTICLE /ARTICLE

The phylogenetic status of Homo heidelbergensis – a cladistic study of Middle Pleistocene hominins

Le statut phylogénétique d’Homo heidelbergensis – étude cladistique des homininés du Pléistocène moyen

A. Mounier · M. Caparros

Received: 17 March 2015; Accepted: 2 May 2015

AbstractTwo views prevail concerning the significance of H. heidelbergensisin Middle Pleistocene human evolution.

H. heidelbergensis sensu strictorefers to a European chrono- species of H. neanderthalensis while H. heidelbergensis sensu lato is considered to be an Afro-European species ancestral to modern humans and Neandertals.

Here, we test the phylogenetic validity ofH. heidelbergen- sisusing a cladistic analysis based on cranial morphological data of Pleistocene fossils. We perform a low-level analysis to ascertain the information content of the morphological features, a high-level analysis with reweighted characters result- ing in a single most parsimonious cladogram and a bootstrap analysis to assess the robustness of this cladogram.

Our results show that (i) the identification of a coherent H. heidelbergensis s.l. species is not well supported and is equivocal; (ii) the hypothetical last common ancestor of H. sapiensandH. neanderthalensishas more affinities with African specimens than European; (iii) two Middle Pleisto- cene European fossils (Atapuerca SH5 and Steinheim) should be classified asH. neanderthalensis.

Keywords Homo heidelbergensis· Cladistics · Last common ancestor of modern humans and Neandertals · Sima de los Huesos

Résumé Le rôle d’Homo heidelbergensisdans l’évolution humaine au Pléistocène moyen est interprété à la lumière de deux hypothèses principales. H. heidelbergensis sensu stricto fait référence à une chrono-espèce européenne d’Homo neanderthalensis alors que H. heidelbergensis sensu latoest considérée comme l’espèce afro-européenne ancestrale aux hommes modernes et aux Néandertaliens.

Dans cette étude, nous testons la validité phylogénétique d’H. heidelbergensisà l’aide d’une analyse cladistique basée sur des caractères morphologiques crâniens de fossiles du Pléistocène. Nous réalisons une analyse de premier ordre (‘low-level’) pour quantifier le contenu d’information des car- actères morphologiques ; puis une analyse de deuxième ordre (‘high-level’), avec des caractères pondérés, permettant l’obtention d’un unique cladogramme le plus parcimonieux et finalement une analyse bootstrap afin d’évaluer la robus- tesse de ce cladogramme.

Nos résultats montrent que (i) l’identification d’une espèce cohésiveH. heidelbergensis s.l. n’est pas bien étayée et est donc équivoque ; (ii) le dernier ancêtre commun hypothétique àH. sapiensetH. neanderthalensisa plus d’af- finité avec les fossiles africains qu’européens ; (iii) deux fossiles du Pléistocène moyen (Atapuerca SH5 et Steinheim) devraient être classé en tant qu’H. neanderthalensis.

Mots clésHomo heidelbergensis · Cladistique · Dernier ancêtre commun des Hommes modernes et des

Néandertaliens · Sima de los Huesos

Introduction

Over the past twenty years, the study of the Middle Pleisto- cene divergence of the anatomically modern human (AMH)

A. Mounier (*)

The Leverhulme Centre for human Evolutionary Studies, Department of Archaeology and Anthropology,

University of Cambridge, Fitzwilliam Street, Cambridge CB2 1QH, United Kingdom e-mail : [email protected]

UMR 7268 ADES, Aix-Marseille Université/EFS/CNRS, Faculté de Médecine - Secteur Nord,

CS80011 Bd Pierre Dramard 13344 Marseille, France Fondation Fyssen. 194 rue de Rivoli. Paris, France M. Caparros

Muséum national d’Histoire naturelle,

Département de Préhistoire, UMR 7194 du CNRS, 1, rue René Panhard, 75013 Paris, France DOI 10.1007/s13219-015-0127-4

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and Neandertal lineages has been the object of intense focus and debate in palaeoanthropology. The speciation of these two taxa remains unclear despite discoveries of new fossils, and a consensus over the systematics of the genusHomodur- ing the Middle Pleistocene is yet to emerge among authors.

However, many researchers concur that the taxonomic con- cept ofHomo heidelbergensis[1] is of importance when dis- cussing human evolution in the Middle Pleistocene [2-4].

The type specimen, a human jaw found in Mauer (Heidel- berg, Germany), was namedH. heidelbergensisin 1908 by Schoetensack [1]. The Mauer mandible, recently dated at 609±40 ka [5], shows a mixture of primitive (thick mandibular body, great anteroposterior length of the ramus and receding symphysis) and derived (size and shape of the teeth) traits [6-8]. Its peculiar morphology, the lack of comparative material at the beginning of the 20^th century and the nature of the fossil itself (a lower jaw) made it diffi- cult to diagnose the species and to position it in the hominin phylogeny.H. heidelbergensiswas largely forgotten during most of the 20^thcentury, before being re-used as aH. erectus sub-species (i.e.H. erectus heidelbergensis[9,10]). Episte- mologically, this classification of H. heidelbergensis was construed as a Euro-centric clarification of the broadly defined classification archaic H. sapiens often used to lump together old world fossils such as Broken Hill 1 (i.e. Kabwe), Arago, Petralona and Dali. This broad desig- nation implied that these fossils represented the supposed regional ancestors of AMHs [11].

For some authors [2,7,12,13],H. heidelbergensisrepre- sents the last common ancestor of AMHs and Neandertals, while for others [8,14] it embodies a derived form of the H. erectustype evolving gradually towards Neandertals.

The proponents ofH. heidelbergensisare implicitly asso- ciated with the hypothesis of the emergence of AMHs (Recent African Origin [15]), which posits thatH. sapiens emerged in Africa during Marine Isotope Stage 6 (i.e. 190- 130 ka). This new species spread out of Africa and replaced ancient Eurasian populations with minimal genetic admix- ture [15-19]. In this context, two interpretations ofH. heidelbergensisare proposed:

H. heidelbergensis sensu strictois supported by authors who put forward an accretionary model of evolution [20-23 ]. They assert that the accumulation of Neandertal apomorphies among European Middle Pleistocene fossils distin- guishes them from the contemporaneous African fossils and justifies their separation into two lineages. In this framework, the European fossils are either considered as a European chrono-species (H. heidelbergensis) implicitly ancestral to H. neanderthalensis[8, 14] or as part of the evolving Nean- dertal lineage, and as such lumped in the taxon H. neanderthalensis [24]. The Middle Pleistocene African fossils ought to be included in the speciesH. rhodesiensis [25] as exemplified by Broken Hill 1. The anagenetic accretionary

model essentially follows the principles of inductive phyletic gradualism, as proposed by the traditional neo-Darwinian pre- phylogenetic school [26] where classification is based on total morphological evidence, including primitive characters.

H. heidelbergensis sensu latowas introduced in 1983 by Stringer [27]. In a study of the Petralona cranium Stringer advocated the reintroduction of the nomenH. heidelbergensis as the Afro-European stem species of H. neanderthalensis andH. sapiens[27]. This view was later supported and further developed by Rightmire [2, 12] and other researchers [4, 7, 13, 28, 29]. At times, Rightmire [30] and Stringer [15]

favoured accretionary models for Neandertal and modern human evolution while arguing that both of these descended from a widespread H. heidelbergensis ancestral species.

Stringer [4], although relying on a cladistic terminology, follows a“pre-phylogenetic”approach by taking into consider- ation a suite of morphological traits deemed to be diagnostic ofH. heidelbergensisbut untested by cladistic analysis.

New models have been proposed for Middle Pleistocene human evolution in order to classify additional fossil discoveries in Atapuerca (Gran Dolina [31] and Sima del Elefante [32]) and in Russia (Denisova [33]). These models infer the existence of a new taxon ancestral to modern humans and Neandertals (H. antecessor[31]) or the existence of a different lineage fromH. sapiensandH. neanderthalensis(Deni- sova [33]). The latter gained recent support from the analysis of sequenced mtDNA from Sima de los Huesos [34]. How- ever, these models are based either on principles of inductive phyletic gradualism, or, in the case of palaeogenomic studies, on genetic distance similarity algorithms calibrated to uncertain molecular clocks, both approaches failing to take homoplasies, apomorphies and plesiomorphies into account numerically in a phylogenetic context. Both models remain unclear [16, 35, 36] and therefore a clarification of the phylogenetic history of the genus Homo during the Middle Pleistocene is still needed. It should also be noted that a Eurasian hypothesis forH. heidelbergensiscannot be ruled out and would need to be considered [36,37].

Although numerous works have focused on the definition of cranial synapomorphies in Neandertals [38-40], the deter- mination of what derived characters might differentiateH. hei- delbergensisfrom its precursors and descendants (e.g. [12,30]) has not been fully addressed. One of us proposed a definition ofH. heidelbergensis s.l.by means of a phenetic methodology [7,29,41]. However, few numerical cladistic analyses of palaeospecies at the fossil specimen level exist [11, 42-52], and they are not focused onH. heidelbergensis. Stringer [53]

addressed the question of Middle and Late Pleistocene human diversity by means of a cladistic analysis. In our opinion, the grouping of diverse fossils into predefined taxa, the lumping of European and African Middle Pleistocene fossils together into early archaic H. sapiens and the use of very general characters did not resolve the issue of the validity of the

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H. heidelbergensisclassification which came to be used later on after publication of the paper. The use of fossil specimens as terminal taxa is considered, incorrectly, to be theoretically invalid (see Methods) by some researchers; however, as it is also the case in palaeogenetic studies, cladistics has been used below the species level [11,42-47], and in some cases, partic- ularly when uncertainties exist about the taxonomical attribu- tion of some fossils, should be used below the species level to avoid contentious debates with regard to evolutionary scenar- ios [54-56]. In order to test the phylogenetic validity of palaeospecies, and given the scarcity of material in the Middle Pleistocene fossil hominin record, each fossil must be considered as representing a sample of a population or morphotype.

Here, therefore, as required in a Hennigian conceptual framework, we use a cladistic analysis of cranial morphological data to test the phylogenetic validity of the speciesH. heidelbergensis and shed new light on the systematics of the genus Homo during the Middle Pleistocene. In essence, we will address the following questions:

•

Is it possible to define the Middle PleistoceneH. heidelbergensis s.l.taxon phylogenetically?

•

Could this taxon be classified as the last common ancestor of AMHs and Neandertals?

•

What would be the profile of the morphotype of this hypothetical common ancestor?

Table 1 Specimens included in the analysis. Bold type indicates observed original fossil /Spécimens inclus dans l’étude. Les fossiles originaux observés pour cette étude sont indiqués en gras.

Specimen Chronology Site Chronology

references

Early Pleistocene

D2700 1.81±0.05 Ma Dmanisi, Georgia [49]

KNM-ER 3733 ~1.6 Ma East Turkana, Kenya [50]

Sangiran 17 1-1.5 Ma Java, Indonesia [51]

Middle Pleistocene

Atapuerca SH5 427±12ka Sima de los Huesos, Atapuerca, Spain [52]

Arago 21/47 450 ka Tautavel, France [53]

Ceprano 385-430 ka Ceprano, Italy [54]

Steinheim 250-300 ka Steinheim, Germany [55]

Petralona 150-250 ka Petralona, Greece [56]

Bodo 600 ka Bodo, Ethiopia [57]

Florisbad 259±35 ka Bloemfontein, South Africa [56]

Jebel Irhoud 1 130-190 ka Jebel Irhoud, Morocco [58]

Broken Hill 1 125 ka Broken Hill, Zambia [59]

LH 18 129-108 ka Laetoli, Tanzania [60]

Dali 260-300 ka Dali, China [61]

Jinniu Shan 200 ka Jinniu Shan, China [62]

Late Pleistocene H. neanderthalensis

Saccopastore 1 100-130 ka Saccopastore, Italy [63]

Gibraltar 1 45-70 ka Forbes’Quarry, Gibraltar [64]

La Ferrassie1 53-66 ka La Ferrassie, France [65]

Guattari 1 52±12 ka Monte Circeo, Italy [58]

La Chapelle-aux-Saints ~50 ka La Chapelle-aux-Saints, France [66]

Amud 1 50-60 ka Amud, Israel [67]

H. sapiens

Cro-Magnon 1 28 ka Les Eyzies, France [68]

AbriPataud 22 ka Les Eyzies, France [69]

Chancelade ~12 ka Chancelade, France [70]

Qafzeh 9 100-130 ka Qafzeh, Israel [58]

Qafzeh 6 90-130 ka Qafzeh, Israel [58]

Skhūl V 88-117 ka Skhūl, Israel [71]

Ohalo II 19 ka Ohalo, Israel [72]

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Table 2 Morphological features. Description of morphological features and character states; for more details see Appendix A and Mounier (2009) /Description des caractères morphologiques; pour plus de détails, voir Annexe A et Mounier (2009).

Morphological features Character states

Outline of the calvaria,norma occipitalis 1 0 triangular

1 circular 2 pentagonal Frontal cord length / parietal cord length 2 0 Frontal < Parietal

1 Frontal≈Parietal 2 Frontal > Parietal Outline of the supraorbital region,norma facialis 3 0 straight

1 convex

Supraorbital region:sulcus supraorbitalis 4 0 complete

1 incomplete

2 absent:arcus superciliarisandsupraorbitalismerged

Projection of the supraorbital region 5 0 not projecting

1 arcus superciliarisonly 2 whole supraorbital region Post-orbital constriction (Ipc=M9/M43) 6 0 important (Ipc<0.75)

1 weak (0.75≥Ipc≥0.85) 2 absent (Ipc>0.85)

Outline of the supraorbital region,norma verticalis 7 0 medially concave (glabella) 1 straight

2 convex

Sulcus postorbitalis 8 0 absent

1 medially present 2 present continue

Tuber frontale 9 0 absent

1 defined, medially shifted

2 present

Antero-posterior convexity of the frontal (Ifc=M29*100/M26) 10 0 weak (Ifc95)

1 intermediate (95>Ifc≥90) 2 important (Ifc<90) Linea temporalisdevelopment on the frontal 11 0 absent

1 present, unique 2 present, double

Medio-sagittal supra-glabellar tubercle 12 0 absent

1 present

Sagittal keel on the frontal 13 0 absent

1 present

Bregmatic eminence 14 0 absent

1 present

Thickening on the superior part of the coronal sutures 15 0 absent

1 present

Sagittal keel on the bregma-lambda arch 16 0 absent

1 present

Parasagittal hollowing on both sides of the parietal suture 17 0 absent

1 present

Pre-lambdatic hollowing on the bregma-lambda arch 18 0 absent

1 present

Linea temporaliswidth of the temporal band 19 0 absent

1 narrow (<20mm) 2 wide (≥20mm)

(Suite page suivante)

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Table 2(suite)

Linea temporalis: position on parietal (Rlt = temporo-parietal suture-superior line / temporo-parietal suture-bregma)

20 0

1 2

high (Rlt>0.55) medial (0.54>Rlt>0.46) low (Rlt<0.45)

Torus angularis parietalis 21 0 absent

1 present

Tuber parietale 22 0 absent

1 present, medially shifted 2 present, high position Outline of the occipital,norma lateralis 23 0 rounded profile

1 sharply angled Outline of theplanum occipitale,norma lateralis 24 0 no convexity

1 convexity

Relative development:planum nucale(PN) /planum occipitale(PO)

25 0

1

PN≥PO PN<PO

Occipital bun 26 0 absent

1 present

Opisthocranion relative position / inion 27 0 same position

1 different position

Processusretro mastoideus 28 0 absent

1 present

Outline of theplanum occipitale,norma occipitalis 29 0 triangular 1 circular 2 pentagonal

Suprainiac fossa 30 0 absent

1 hollowing, weakly-delineated

2 present

Suprainiac fossa: lateral edges 31 0 absent

1 convergent upward 2 parallels or arched

Sulcus supratoralis 32 0 absent

1 hollowing

2 present

Torus occipitalis transversus 33 0 absent

1 present: medially protruding 2 present: bilaterally protruding Torus occipitalis transversusform,norma occipitalis 34 0 absent

1 rectilinear

2 convex

Protuberantia occipitalis externa 35 0 absent

1 present

Tuberculum linearum 36 0 absent

1 present

External occipital crest 37 0 absent

1 present, posterior only

2 present

Aligned posterior and anterior external occipital crest 38 0 yes

1 no

Temporal squama heigh (Iet=maximal height fromauriculae*100 / maximal width)

39 0

1

low (Iet≤60) high (Iet> 60) Outline of the anterior border of the temporal squama 40 0 curved or sinuous

1 rectilinear

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Table 2(suite)

Outline of the superior border of the temporal squama 41 0 curved or sinuous 1 rectilinear Development of thecrista supramastoideaat the porion 42 0 absent

1 weakly-marked

2 marked

Crista supramastoidea / processus zygomaticus temporalis 43 0 not lined up

1 lined up

Tuberculum supramastoideum anterius 44 0 absent

1 present

Supramastoid groove (betweencrista supramastoidea andcrista mastoidea)

45 0

1 2

absent

present, closed anteriorly present

Form of the auditory meatus 46 0 circular

1 elliptic Position of the auditory meatus /processus zygomaticus temporalis47 0 below

1 intermediate

2 lined up

Tuberculum mastoideum anterior 48 0 absent

1 present

Processus mastoideus: downward development / basicranium 49 0 weak

1 strong

Juxtamastoid ridge development /processus mastoideus 50 0 less developed 1 as developed 2 more developed

Digastric groove: presence of a bony bridge 51 0 no

1 yes

Crista occipito mastoidea 52 0 absent

1 present

Glenoid cavity depth / articular tubercle lowest point 53 0 shallow (<0.9 mm) 1 deep (>0.9 mm) Petro-tympanic crest orientation in relation to the sagittal plan 54 0 perpendicular

1 frontward

2 backward

Articular tubercle configuration 55 0 medio-lateral concavity

1 antero-posterior convexity

2 medio-lateral convexity and vertical

Tuberculum zygomaticum anterius 56 0 absent to weakly-marked

1 marked

Tuberculum zygomaticum posterius(post glenoid process) 57 0 absent to weakly- marked

1 marked

Tympanal contribution to the posterior wall of the glenoid cavity

58 0

1

weak important

Preglenoid tubercle 59 0 absent

1 present

Glenoid fossa 60 0 closed by thespina glenoidalis

1 closed by the sphenoid spine

Superior orbital rim: form 61 0 horizontal

1 inclined 2 strongly inclined

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Table 2(suite)

Supero-lateral orbital rim: form 62 0 right angle

1 arched

Inferior orbital rim: form 63 0 horizontal

1 inclined 2 strongly inclined

Inter-orbital space 64 0 narrow (<29 mm)

1 wide (≥29 mm) Naso-frontal / fronto-maxillary sutures: form 65 0 horizontal

1 oblique

2 trapeziform Nasal margins configuration: relationships between the lateral,

turbinal and spinal crests

66 0 not merged

1 turbinal / spinal crests merged 2 lateral and spinal crests merged 3 turbinal / lateral crests merged

4 merged

Internal nasal floor configuration 67 0 sloped

1 level

2 bilevel

Form of the inferior margin of the nasal cavity 68 0 sharp 1 pre-nasal fossa 2 pre-nasal sulcus Superior and inferior orbital rims: relative position,

norma lateralis

69 0 anterior

1 level

2 posterior Nasion relative depth compare to glabella,norma lateralis 70 0 deep

1 shallow

2 level

Nasal bones projection / naso-frontal suture,norma lateralis 71 0 weak projection 1 strong projection Lateral margins of the nasal cavity orientation,norma lateralis 72 0 sloping anteriorly

1 vertical / concave Projection of the temporal process of the zygomatic

on the nasal aperture,norma lateralis

73 0 low

1 median

2 high

Zygomatic relative orientation / maxilla 74 0 strongly angled, discontinuous with maxilla 1 curved in the horizontal and coronal planes 2 oblique, continuous with maxilla

Facies lateralisof the frontal process 75 0 concave

1 flat

Tuberculum marginale 76 0 absent

1 weakly-developed 2 well-developed

Zygomatico-facial foramina 77 0 absent

1 one

2 multiple

3 multiple,forming an arc of a circle

Zygomatic body 78 0 concave

1 flat

2 convex

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Materials and Methods Materials

The fossil sample we studied covers as much of the Pleisto- cene fossil record as possible. We chose to limit the analysis to the cranium (i.e. calvaria and upper face) since most of the Middle Pleistocene fossils lack mandibular data. All of the

specimens selected have at least a partial calvaria and a partial upper face, with the exception of Ceprano (no upper face). Ceprano was included to further test its possible affili- ation to H. heidelbergensis in the light of recent analyses related to new chronologies [62], and its proposed new phylogenetic position in the Middle Pleistocene human lineage [41]. We selected a group of 28 fossil specimens from Africa, Asia and Europe (Appendix C Table 1), including

Table 2(suite)

Zygomaxillary tuberosity 79 0 absent

1 weakly-developed

2 present

Incurvatio horizontalis 80 0 absent

1 hollowing

2 present

Incurvatio sagittalis 81 0 absent

1 hollowing

2 present

Incurvatio inframalaris frontalis 82 0 absent

1 weakly-developed, at the level of the alveolar margin of the maxilla

2 weakly-developed, present on the whole crest 3 strong, double curved

Canine fossa 83 0 absent

1 slight hollowing, weakly-defined 2 hollowing, well-defined 3 deep hollowing, well-defined

Infra-orbital rim / maxilla 84 0 weakly discontinuous

1 discontinuous

2 strongly discontinuous: vertical maxilla

Infra-orbital foramina 85 0 one

1 multiple Position of the infra-orbital foramen from the infra-orbital rim 86 0 low (≥11 mm)

1 high (<11 mm) Nasoalveolar clivus length (narial-prosthion) 87 0 short (≤17 mm)

1 long (>17 mm) Position of the insertion of the facial crest / dental arch 88 0 P4 and P4-M1

1 M1 and M1-M2

2 M2 and posterior Alveolar torus on the vestibular aspect of the alveolar process 89 0 absent

1 present

Alveolar torus on the lingual aspect of the alveolar process 90 0 absent

1 present

Torus palatinus 91 0 absent

1 present

Incisive foramen: position 92 0 posterior to septum C-P3

1 anterior to septum C-P3

Dental arch: form 93 0 parallel margins

1 divergent margins 2 convergent margins

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three Early Pleistocene fossils used as an outgroup, 12 Mid- dle Pleistocene specimens and 13 Late Pleistocene fossils representing H. sapiens (N=7) and H. neanderthalensis (N=6) (Table 1). No juveniles were included, with the exception of D2700 due to the scarcity of complete cranial fossils available for the Early Pleistocene.

The data on the fossil samples include 93 coded morphological features of which 60 pertain to the calvaria and 33 to the upper face (Tables 2, 3 and Appendix A). Coded obser- vations were made by one of the authors and repeatability tests were run [29, 41].

Methods

In this study, we conducted a parsimony analysis in three conceptual steps using PAUP software v. 4.0 [81]. MacClade software v. 4.08a [82] was used for graphic illustrations of supporting characters at the hypothetical ancestor nodes.

The cladistic methodological protocol used draws on the research of one of us [11] and essentially expands the second stage of Wiley [83] and de Pinna [84], namely the transfor- mation of primary homologies (a priori conjectures of homology from observed similarities deemed to have been inherited from common ancestors) into secondary homologies, whether apomorphic or homoplastic, by using the parsimony principle, i.e. test of congruence. The first step in the protocol is the low-level analysis (discovery of the information content of characters), the second step is the high-level analysis (cladistic analysis after reweighting of characters) and the final step is the character state optimization for identification of the morphology of the hypothetical ancestors at the nodes of the cladogram.

In keeping with Wiley [83] and de Pinna [84], primary homology is represented here by the 93 unweighted coded characters. Primary homology is ana prioriconjecture that the observed and coded character states represent homologies, i.e. resemblances inherited from a common ancestor.

The low-level analysis provides an assessment of the information content of each character as expressed by the character retention indexRI[85] (Table 4 and C.1), which is interpreted as the degree of secondary homology (i.e. apomorphic or homoplastic) apparent in the character [11]. The high-level analysis run with the reweighted data along with the DELTRAN character state optimization results in one most parsimonious tree through which we discovered and defined the informative secondary homologies (apomorphy or homoplasy) supporting the various clades. Without following this three-step approach, one cannot state a priori what type of homology a character represents as revealed by the cladogram: synapomorphy (shared derived character), autapomorphy (unique shared derived character) or homoplasy. In practice PAUP executes steps 2 and 3 simulta-

neously; we separated these steps conceptually to ensure a better understanding of the protocol.

Further information on the cladistic classification method and the parsimony analysis protocol is given in Appendix B.

Results

Low-level analysis: character information content

A heuristic search based on the 93 characters (Tables 2 and 3) entered with equal weights to evaluate their information content identified 47 morphological features (Table 4) that con- vey appreciable phylogenetic information (Retention Index RI≥0.5, see [11] and [42, 43, 48, 50]). 46 characters (Table C.1) show a higher percentage contribution of homoplasy than synapomorphy to the most parsimonious trees, and therefore could falsify the search for the most phylogenetically informative tree if they were to remain unweighted.

More precisely, of the 47 phylogenetically most informative characters, we identified five true synapomorphies (CI,RIet RC=1,HI=0): four are localized on the calvaria (#3 outline of supraorbital region in norma facialis, #27 opisthocranion position relative to inion, #30 suprainiac fossa, #41 outline of the superior border of the temporal squama) and one is a facial feature (#72 orientation of the nasal lateral margins).

The remaining 42 characters (Table 4) with anRI equal to or greater than 0.5 are distributed as follows: nine have an RI value between 1 and 0.8, 18 features have an RI value comprised between 0.8 and 0.6, and 15 have an RI value lower than 0.6 but equal to or greater than 0.5. The discussion of the results is based on those 47 characters withRI≥0.50 (see below). It is of interest to note that out of the 93 characters, eight have anRIvalue equal to 0 (#16, #20, #25, #37,

#46, #52, #78 and #85, Table C.1), which means that they are phylogenetically uninformative, and will not be taken into account in the final numerical analysis due to their nil RIweight. The heuristic search found eight MPTs with tree fit statistics as follows: tree length=543, CI=0.2615, HI

=0.7385,RI=0.4918 andRC=0.1286. The overall tree statistics of these cladograms are low and would not allow a proper interpretation of the synapomorphous content of the changes in character states at the nodes (see Methods and [11, 84]). It should be noted that the eight trees obtained in this initial step (Appendix E) present very similar classifications of the following specimens: the outgroup (Sangiran 17, KNM-ER 3733 and Dmanisi 2700), two monophyletic groups (SH5, Steinheim, Saccopastore 1, Gibraltar 1, Amud 1, Guattari I, La Ferrassie 1 and La Chapelle-aux-Saints) and (Jinniu Shan, Skhul V, Jebel Irhoud 1, Florisbad, Cro-Magnon 1, Ohalo II, Abri Pataud 1, Chancelade, LH 18, Qafzeh 6 and 9) and the succession of Middle Pleistocene terminals (Dali, Ceprano, Arago, Petralona, Broken Hill 1 and Bodo). The

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Table3CharacterstatesofmorphologicalfeaturesoffossilspecimensandLastCommonAncestor(LCA)ofAMHsandNeandertals(node47,Fig.1)/Etatsdecaractèrespour chaquefossileainsiquepourleDernierAncêtreCommundesHommesmodernesetdesNéandertaliens(nœud47,Fig.1). 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647 D270001111022011011111010100010001000000111101010110 KNM-ER373302122012111011100122101000010002110120111111110 Sangiran1702122122112011101021101000010001110120010201101 SH522112212111110011112021110102121111120110211201 Arago21/47--11220212110000002210---------------- Ceprano02112102121100-00-221210-00100011111--0101111-1 Steinheim1111220222000011101201011110212021010-110111210 Petralona02112202122000111122101111010001120111100200211 Bodo--112122121111111-1110-----------1--2----- Florisbad--1111-01210101001---2---------------- JebelIrhoud1200022222210000011110201101020000000200001012-0 BrokenHill102112102122010101112101101102002121-2-110111210 LH1821102101211000011112020110102000000120010000010 Dali2211220212201000102212101001000011110-100211211 JinniuShan22112222111110000112011111111001111120100010110 Saccopastore112--22--211-0000101210111011121021002111000121- Gibraltar11011222220110-0---12001111101220210021000211100 LaFerrassie112122222222000011112001111101220210021000201202 Guattari11212222221110001012200111110122121000-110200202 LaChapelle- aux-Saints

10122222221100001112001111101220210011000001212 Amud1121122222211000001120001111012112100001-0100211 Cro-Magnon120101220221000001121020000112000001100110210210 AbriPataud22101220221000001012020110102000001020000100200 Chancelade20101220211000001022020110102000001000110010210 Qafzeh9201012202010000-00120000101020000001--110100210 Qafzeh6221022212010000001120201101020010010011-0100200 SkhūlV20012122211000011112010110112000001100100010210 OhaloII20101200211000000112020110102000001121110201110 LCA(node47)22112222121010001112021111102001111120110211210 (Suitepagesuivante)

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Table3(suite) 48495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293Missing #(%) D27000--00020011011110112212001000221212121001001012,2 KNM-ER373310100020101011120230202001011202112120010000000 Sangiran170000-020111100010101000100010020101010111000011,1 SH501000020010101111231202110102321112111011001120 Arago21/47---------10112210001111022211121100111111143 Ceprano010011200111-00--0----1----022-----------35,5 Steinheim01000020110110120130100111100321212220011100101,1 Petralona-1010120110011021242100111102111111110011110111,1 Bodo---0-0-10--10111222001111001221021100110001237,6 Florisbad---------002124100001-00012021322--010001250,5 JebelIrhoud101000101100102111130201111000121223221111000111,1 BrokenHill101100101110101021212200111100322112110011111022,2 LH1800100111001010-20110002111----2233200010-0118,6 Dali00200121111111011121000110010211223220100011101,1 JinniuShan00011000010112111231200110010222213220011010120 Saccopastore11001011001011001113220-11-111021111110011100108,6 Gibraltar10020-010010110020222111111101311101101102100025,4 LaFerrassie110210010110101121202102111211311000000012101010 Guattari110200010100011120102101111211321000010011001101,1 LaChapelle- aux-Saints

10010010110001121122101111211301000001012101000 Amud111-0-000010--00212-2-11--1-02322--1----021000117,2 Cro-Magnon111000111101011110211000112001122223320100001120 AbriPataud01010111101011000111021012001210223320101101110 Chancelade01010111110011010220022-12001220223320001001111,1 Qafzeh901-0-1010011-1020-21222-1-00021122222-0110001210,8 Qafzeh60----1111010-212012100011101122222222--11010128,6 SkhūlV010101011011001-0----10--1000110--2----1101--216,1 OhaloII01000111100112010201022011002222223320101000110 LCA(node47)01000000110111121131200111100122112110011000120

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Table 4 Most informative characters in decreasing order ofRI(Retention Index). Characters with RI≥0.5 show a higher percentage contribution of synapomorphy than homoplasy in the most parsimonious tree and therefore are the most phylogenetically informative / Caractères les plus informatifs classés en fonction de leur valeur de RI (Indice de Rétention). Les caractères dont le RI≥0,5 sont plus informatifs phylogénétiquement et contribuent de façon plus importante à l’arbre le plus parcimonieux.

Morphological features # RI CI RC HI

True apomorphiesRI=1; 5#

Outline of the supraorbital region,norma facialis 3 1 1 1 0

Opisthocranion relative position / inion 27 1 1 1 0

Suprainiac fossa 30 1 1 1 0

Outline of the superior border of the temporal squama 41 1 1 1 0

Lateral margins of the nasal cavity orientation,norma lateralis 72 1 1 1 0 1<RI≤0.8: 9#

Torus occipitalis transversus 33 0.923 0.667 0.615 0.333

Outline of the calvaria,norma occipitalis 1 0.909 0.667 0.606 0.333

Tuber frontale 9 0.9 0.667 0.6 0.333

Torus angularis parietalis 21 0.889 0.5 0.444 0.5

Zygomatic relative orientation / maxilla 74 0.889 0.667 0.593 0.333

Suprainiac fossa: lateral edges 31 0.833 0.667 0.556 0.333

Outline of theplanum occipitale,norma occipitalis 29 0.818 0.5 0.409 0.5

Torus occipitalis transversusform,norma occipitalis 34 0.8 0.5 0.4 0.5

Articular tubercle configuration 55 0.8 0.333 0.267 0.667

0.8<RI≤0.6: 18#

Incurvatio sagittalis 81 0.769 0.4 0.308 0.6

Canine fossa 83 0.769 0.5 0.385 0.5

Petro-tympanic crest orientation in relation to the sagittal plan 54 0.75 0.4 0.3 0.6

Supraorbital region:sulcus supraorbitalis 4 0.727 0.4 0.291 0.6

Outline of the occipital,norma lateralis 23 0.727 0.25 0.182 0.75

Glenoid cavity depth / articular tubercle lowest point 53 0.727 0.25 0.182 0.75

Incurvatio horizontalis 80 0.7 0.4 0.28 0.6

Sulcus postorbitalis 8 0.667 0.5 0.333 0.5

Bregmatic eminence 14 0.667 0.5 0.333 0.5

Outline of theplanum occipitale,norma lateralis 24 0.667 0.333 0.222 0.667

Tuberculum linearum 36 0.667 0.25 0.167 0.75

Tuberculum zygomaticum posterius(post glenoid process) 57 0.667 0.25 0.167 0.75

Incurvatio inframalaris frontalis 82 0.643 0.375 0.241 0.625

Sagittal keel on the frontal 13 0.625 0.25 0.156 0.75

Occipital bun 26 0.625 0.25 0.156 0.75

Form of the inferior margin of the nasal cavity 68 0.615 0.286 0.176 0.714

Zygomatico-facial foramina (Maureille, 1994) 77 0.615 0.375 0.231 0.625

Tympanal contribution to the posterior wall of the glenoid cavity58 0.6 0.2 0.12 0.8 RI<0.6: 15#

Inter-orbital space 64 0.583 0.167 0.097 0.833

Position of the auditory meatus /processus zygomaticus temporalis

47 0.571 0.4 0.229 0.6

Tuberculum marginale 76 0.571 0.25 0.143 0.75

Incisive foramen: position 92 0.571 0.25 0.143 0.75

Processus mastoideus: downward development / basicranium 49 0.556 0.2 0.111 0.8

Infra-orbital rim / maxilla 84 0.556 0.333 0.185 0.667

Nasoalveolar clivus length (narial-prosthion) 87 0.556 0,2 0.111 0.8

Alveolar torus on the vestibular aspect of the alveolar process 89 0.556 0.2 0.111 0.8 (Suite page suivante)