The significance of the fossil hominid skull from Petralona, Greece

Journd

Q/’ Archaeological

Science 1979, 6, 235-253

The Significance of the Fossil Hominid from Petralona, Greece

Skull

Christopher B. Stringer,” F. Clark Howell” and John K. Melentis“ Evidence is accumulatingthat the hominid cranium found in the Petralonacave in 1960is associatedwith cave depositsof middle Pleistoceneage. If this is so, the fossilis the mostcompletemiddle Pleistocenecranium yet discoveredand provides important morphological. metrical and radiographic information on the possible evolutionary transition from Homo erectus to Homo sapiens. The classificationof the specimenis discussedand it is suggestedthat a grade system within Homo .sapiens should be erected.The Petralonafossilwould be allocated to Homo sapiens grade 1 rather than to Homo erectus or to a subspecies of Homo sapiens. Keywords; GREECE, PETRALONA CAVE, MIDDLE PLEISTOCENE, FOSSIL HOMINID, CRANIUM, RADIOGRAPHS, HOMO ERECTUS, HOMO SAPIENS, EVOLUTION.

Introduction Samplesof fossil hominids from the Plio-Pleistocene have grown rapidly in recent years and have led to a marked increasein knowledge of the genus Australopithecus and of the early stagesof evolution of the genus Homo (Homo habilis, Homo erectus) (for example seeWalker & Leakey, 1978). There have also been many finds of hominids from the later middle Pleistocene and upper Pleistocene which document the evolution of our own species,Homo sapiens (Pilbeam, 1975; Stringer, 1978). It is widely assumedthat Homo erectus evolved into Homo sapiens, but the supposed evolutionary transition is still poorly documented in the fossil record. European middle Pleistccene finds have generally been rather fragmentary but those from Mauer, Steinheim, Swanscombe,VCrtessz8lliis, Arago and Bilzingsleben show to varying degrees“archaic” features reminiscentof Homo erectus, and somehave been classifiedwithin that speciesby certain workers (for example see Wolpoff, 1977; VlEek, 1978). In Africa, fossils such as those from Broken Hill, Saldanha, Omo (Kibish formation), Salt and Ndutu have been regarded as representatives of advanced Homo erectus or archaic Homo sapiens populations (Rightmire, 1979). At present there is much debate amongst palaeoanthropologists on the best means of classifying fossil hominids. The suggestion by Campbell (1964) that most of the middle and upper Pleistocene fossils could be classified as subspeciesof Homo erectus or Homo “Sub-Departmentof Anthropology, British Museum (Natural History), Cromwell Road, London SW7 SBD. *Department of Anthropology, University of California, Berkeley, California 94120, U.S.A.

CDepartmentof Geology and Palaeontology.University of Thessaloniki. Greece. 235 0305-4403/79/030235

+ I9 $02.00/O

‘c 1979 Academic Press Inc. (London)

Limited

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sapiens has been utilized by many workers, but such subspecific categories say little about the relationships of the fossils themselves and provide no information about evolutionary relationships. Alternative classifications using cladistic or cladogenetic methods are heavily dependent on the available fossil material for assessment of plesiomorphous (“primitive”) and apomorphous (“derived”) characteristics within Pleistocene and recent hominids (Delson, Eldredge & Tattersall, 1977). Work on rates of evolutionary change in hominids is dependent on the model of ancestor-descendant relationship chosen and is similarly hampered by the present lack of complete fossil material from the middle Pleistocene (Bilsborough, 1976). So the recognition of a virtually complete fossil hominid cranium, which seems chronologically and morphologically intermediate between Homo erectors and Homo sapiensis of the greatest importance, especially when such a find can complement the incomplete specimens available from the European middle Pleistocene. The Petralona cranium was discovered in a cave in the Katsika (Goat) Hill near the village of Petralona, Halkidiki in 1960. Early work on the skull led to the belief that it was a Greek “Neanderthal” and this view was apparently reinforced by the first excavations and by fauna1 analyses which dated at least some of the cave deposits to a last interglacial or last glacial age (Sickenberg, 1964; Marinos, Yannoulis & Sotiriadis, 1965). Sickenberg later concluded from a fuller study that the material was more appropriately dated as upper Biharian, perhaps equivalent to sites such as Vertesszijlliis and Mosbach (Sickenberg, 1971). More recently Kurt& and Kretzoi have analysed fauna1 material from excavations by Poulianos. Kurten, working on the carnivores, concluded that a wide time-range was covered but that a pre-Cromerian to “inter-Mindel” (preHolsteinian) age was indicated (Kurten & Poulianos, 1977), whilst Kretzoi (1977), working on small vertebrates, suggested a “middle Middle Pleistocene” age for the microfauna, corresponding to the Vtrtesszolliis or Templomhegy phases. The first absolute dates for stalagmitic material from the cave were obtained by radiocarbon, giving a minimum age of 44,000 years b.p. (Poulianos, 1971) but more recently Ikeya, using the “electron spin resonance” technique (a variant of thermoluminescence dating) obtained an estimated age of about 250,000 years for central cores of surface stalagmite in the cave (Ikeya, 1977). Recent uranium series determinations by Schwartz, Liritzis & Dixon (in press) suggest a long history of deposition in the cave. The site from which the cranium was derived was the locus of travertine deposition before 350,000 years B.P. but the deposits from which Kurten and Kretzoi studied fauna1 material may be, in part, much younger than this age. An attempt by Dr R. Protsch at an amino-acid racemisation date on a fragment of the cranium supplied by J.K.M. produced an age of 260,000 years B.P. but details of the method of calibration are not yet available. The age of the Hoxnian/Holsteinian interglacial may be greater than 400,000 years (Kukla, 1977) or may be only about 275,000 years (Szabo & Collins, 1975), but if the Petralona fauna is no younger than upper Biharian it is clearly older than true Hoxnian/ Holsteinian faunas, whatever their age. However it should be borne in mind that the cranium was a virtually isolated surface find, covered in stalagmite, while fauna1 material has been collected from many areas of the cave system (which extends for at least 1.5 km), both from surface deposits and from excavations. So great caution must be exercised before directly associating the hominid cranium with fauna1 or other material from the cave. Nevertheless the cranium is probably not younger than the most recent fauna1 material within the cave, suggesting on present evidence a minimum age for this hominid fossil of about 300,000 years B.P. The Petralona cranium has now been recognized as a probable Homo evectus or archaic Homo sapiensspecimen but only brief descriptions or assessments of this important fossil have been published recently (Hemmer, 1972; Stringer, 1974a; Schott, 1974).

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Description

The cranium is well-preserved and virtually complete, lacking the incisors and the crown of the right canine, the right zygomatic arch and, probably, the mastoid processes. There is slight damage in both infratemporal fossae, the right zygomaxillary area, the medial walls of the orbits and on the left frontal bone. The skull was encased in a pink stalagmitic matrix when discovered and this has been mechanically removed from most of the vault and palate. However, much of the cranial base, face, the left zygomatic arch, the left temporal fossa and the inferior parts of the left temporal and parietal and the occipital were still obscured at the time of this study. The cranium has since been completely cleaned by Greek technicians. The endocranial surface of the skull was also lined by a thin calcareous encrustation, but it was possible to measure the cranial capacity using millet seed, giving a range of 1190-1210 ml. Although this method probably gives a minimum value it is comparable with the lowest values previously published, and considerably less than the figure of about 1400 ml which was presumably obtained by calculation from external measurements (cited by Howells, 1974). The discrepancy between the large external measurements of the cranium and the small endocranial volume can be exp!ained by cranial shape and thickness. A list of cranial measurements is presented in Table I. Table 1. Measurements taken on the Petralona cranium. Measurements are averaged where appropriate and averaged for data collected by CBS and FCH where differences are less than I.5 mm. Otherwise two measurements are given, CBS value first. Howells (1973) definitions used where appropriate. Brackets represent less certain values due to presence of matrix or damage and double brackets indicate that the value has been obtained by estimation. EAM = external auditory meatus. FMA = frontomalare General

Glabello-occipital length Glabello-lambda length

209-O 185-O 200.0 (110.5) 127.0 150.0 156.0

Nasio-occipital length Basion-nasion length Basion-bregma height Maximum breadth (parietal) Maximum breadth (temporal) Bizygomatic breadth (WW) Ant. bizygomatic breadth (146.0) Biauricular breadth (154.5) Inion-prosthion length (224.0) Basion-prosthion length (121.0, 118.8) Minimum cranial breadth r;;oo) Transverse breadth between EAM Frontal

bone

120.0 Maximum frontal breadth 110.8 Minimum frontal breadth 113.0, 117.5 Bistephanic breadth Breadth supraorbital torus 133.5 Lateral thickness of torus 15.9 Medial thickness of torus (at notch) 20.8 14.0 Supraorbital projection Glabella projection 11.0 111.0 Nasion-bregma chord Nasion-breama subtense 21.0 67.0 Nasion-bregma fraction Nasion-bregma arc 130.0 FMA-pterion length 39.1 Face

Nasion-prosthion

height

(94.0, 92.5)

Nasal height (nasion-subspinale) (65.0) Nasal aperture height 39-l Maximum nasal breadth (30-9) Inferior nasal breadth (26-3) Nasospinale-prosthion 30-7. (26-7) Nasal bone length (med.) 14.6 Internasal breadth (sup.) 34.5 Orbital hright Orbital breadth 414.5, 41.0 Bijugal breadth 141-o Bimalar breadth 128.4 A-P thickness zygoma at FMA t?-6 Bimaxillary breadth ((109-O)) Zygomaxillary subtense ((31.0)) Bifrontal chord 127.0 Nasio-frontal subtense 22.0 1240 Biorbital breadth (ect.) 118.4 Biorbital breadth (int.) 133-5 Biorbital breadth (ext.) Dacryon subtense (( IOQJ Interorbital breadth (36.4) Naso-dacryal subtense ((14+%) Minimum cheek height (34-5) 52.8 Perpend. height FMA-base zygoma Temporal

and base

Maximum length temporal Height squama above EAM Transverse length glenoid fossa Width glenoid fossa Lat. breadth across base of pterygoids

64.5 49.4 (34.3) (14.0) (67.4)

(Continued

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Palatal

Pavierals

Breadth at parietal tubers Bregma-lambda chord Bregma-lambda subtense Bregma-lambda fraction Bregma-lambda arc Bregma-asterion chord Bregma-asterion arc Bregma-pterion chord Bregma-pterion arc Lambda-pterion chord Min. bregma-temporal lines

133.0 105.0 19.0 60.0 114.5 139.0 165.0 88.0 99.0 (74.5) (63.3)

External palate breadth Palate length Average palate depth from alveolus Inter-C distance (lingual between tooth surfaces) Inter-P” distance (lingual between tooth surfaces) Inter-M’ distance (lingual between tooth surfaces) Inter-M2 distance (lingual between tooth surfaces) Inter-M3 distance (lingual between tooth surfaces) Prosthion-dist. M”

Occipital

Radii

Lambda-opisthion chord 91.0 Lambda-opisthion subtense 36.0 Lambda-opisthion fraction 41.0 Lambda-opisthion arc 129.0 Biasterionic breadth ((119.5, 116.2)) Lambda-inion chord 63.5 Inion-opisthion chord 62.0, 64.3 Inion-asterion chord ((73.0)) Lambda-asterion chord ((84.0)) Lambda-asterion arc ((98.0) Foramen magnum length 41.5 Foramen magnum length (int.) 38.7 Foramen magnum breadth 32.6 Basion-inion length 100.5 Maximum breadth occipital torus (116.0) Maximum length occipital condyles (24)

EAM-vertex radius EAM-nasion radius EAM-subspinale radius EAM-prosthion radius EAM-dacryon radius EAM-zygorbitale radius EAM-FMA radius EAM-ectoconchion radius EAM-zygomaxillare radius EAM--Ml alveolus radius EAM-bregma radius EAM-lambda radius EAM-inion radius EAM-asterion radius EAM-opisthion radius EAM-basion radius

Norma

lateralis

(Figure

87.5 65.0 14.0 35.0 42.5 46.7 50.8 58.8 62.5 116.0 103.0 (111.0) (120.0)

w384w

87.0 81.0 (79.0) (79.0) 88.5 114.5 108.0 101.0 ((54.0)) 47.0 14.0

I)

One of the most striking features of the lateral view of the cranium is the projecting supraorbital torus, overhanging the relatively deep nasal root. The nasal bones project but the middle and lower face are relatively orthognathous. The supraorbital torus runs smoothly into the relatively flat frontal bone and there is no true supratoral sulcus.The sagittal contour shows a slight depression at bregma and a small mound-like swelling midway between bregma and lambda. There is a raised area inferior to lambda corresponding to the position of a wormian bone, below which is a sulcuswhich dips laterally. The area of the occipital torus in lateral view doesnot resemblethe mound-like structure found in Asian Homo erectus crania but is an extensive slightly raised area beginning below the sulcus already described and terminating at the thickened angulated junction of the occipital and nuchal planes. Opisthocranion lies on the upper part of the torus rather than at the inion. The posterior part of the nuchal area is slightly concave in lateral view. Although the temporal area was partly obscured by matrix it was possible to seethe articular eminence and the post-glenoid tubercle on each side. The external auditory meatus is elliptical with the largest diameter approximately vertical. There is a spheno-parietal articulation on both sides, and the most lateral chamber of the frontal sinus can be seenwithin the left temporal fossawhere the frontal bone is damaged. Holes in the temporal squamae reveal an extensive pneumatization particularly where the squamae are posteriorly thickened and raised above the surface of the parietals. The temporal lines on the frontal bone initially run parallel to the mid-sagittal contour of the vault, but the inferior temporal line dips to meet the coronal suture, enclosing a distinct

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Figure 1. Left lateral view of Petralona

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Figure 2. Left lateral radiograph

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cranium.

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of Petralona cranium.

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fossa around stephanion on the right side. On the parietal there is a torus angularis which turns superiorly without crossing the lambdoid suture. Parallel to this ridge but about 2cm higher is a second ridge of bone which appears to represent the continuation of the supramastoid crest. These ridges on the parietals fade as they rise to meet the temporal lines, and they enclose a slight sulcus posterior to the thickest part of the temporal squamae. Norma facialis (Figure 3)

The frontal bone is relatively flat without sagittal keeling and the supraorbital torus is not sharply defined, being separated from the rest of the superior surface by only a slight depression. The torus is well developed laterally but is thickest above the supraorbital notches. It consists of two distinct arches which meet below the supraglabellar depression. The superior margin of the orbits is less sharply defined than the lateral and inferior margins, and the orbits are relatively rectangular in shape with lateral height only slightly greater than medial height. The nasal bones rise superiorly to form an inverted “V” and a remnant of the metopic suture extends from this point across the glabella. The internasal suture deviates towards the right so that the left nasal bone is broader than that on the right. The lower part of the nasal bones and much of the lower face were obscured by matrix, but the upper nasal border projects above the nasal aperture. The exact shape of the external aperture was difficult to determine but the position of its maximum breadth occurs near the midpoint rather than more inferiorly. The detailed form of the lower border was obscured but it appeared to be well defined and relatively horizontal with a prominent anterior nasal spine. Photographs of the cleaned face suggest the form of the nasal aperture is very reminiscent of that of Arago 21. The nasal septum is preserved posteriorly and deviates strongly to the left in its central and upper portion. The zygomatic bones are large in size with a strong temporal flare. The maxillae were partly obscured by matrix but are massively built with a very large cheek height and little distinction between the zygomatic and alveolar portions. The subnasal area is flat and extensive. Norma verticalis

The supraorbital torus can be seen to consist of left and right halves divided at glabella. Posterior to each are two slight sulci which run parallel to the torus and meet above glabella. The anterior surface of the torus retreats laterally and the lateral parts of the torus flare anterior to a well-developed post-orbital constriction. The left zygomatic arch also flares to produce a deep temporal fossa. The superior margin of the frontal bone is slightly elevated at bregma, and the anterior surfaces of the parietal bones are similarly raised along parts of the coronal sutures. There is a slight heaping of bone along the sagittal suture and a mound of bone about 15 mm in diameter lies on the suture posterior to the single parietal foramen on the right side. Norma occipitalis

The vault is broadest where the temporal bones flare posteriorly, and the parietals converge slightly without curving until the level of the parietal tubers where they curve sharply to meet at the slightly keeled sagittal suture. There are no parasagittal depressions and there is a distinct wormian bone below lambda which does not appear to have affected the course of the other sutures in the area. The wormian bone lies on a raised area of bone running laterally across the upper part of the occipital squama. Parallel and inferior to this is a furrow which may correspond to the supratoral sulcus. Inferiorly there is a high and flat torus without a restricted supratoral (suprainiac) fossa

100 mm

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Figure 3. Facial view of Petralona cranium.

L

100 mm

Figure 4. Facial radiograph

I of Petralona cranium.

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which slopes laterally but fades before meeting the lambdoid suture. The inferior margin of this raised area is at the thickened junction of the occipital and nuchal planes. This junction is most thickened at the inion where a well-developed occipital crest appears, but it thickens again as it approaches asterion on each side and the raised line of bone appears to divide, with the inferior part turning anteriorly to join the prominent occipitomastoid crests on each side of the nuchal area. The course of the superior division was obscured by matrix but it is apparent that if this high and relatively flat structure can be regarded as an occipital torus, it is confined to the occipital bone. Norma basalis (Figure 5)

The very broad base of the vault displays a long, wide and relatively concave nuchal plane bordered posteriorly by the inferior margin of the occipital torus. Posteriorly there is a well-developed occipital crest which thins as it approaches the foramen magnum.

Figure 5. Basal view of Petralona cranium.

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Lateral to the crest are prominent mounds of bone. These mounds which may correspond to the inferior nuchal lines are limited anteriorly by post-condylar fossae bordering the foramen magnum, laterally by the occipito-mastoid crests, posteriorly by the concave nuchal plane anterior to the occipital torus, and medially by the fossa in which the occipital crest lies. The foramen magnum is not very elongate and there are no postcondyloid tuberosities. The plane of the foramen magnum is relatively horizontal in the Frankfurt plane but the nuchal and basilar planes of the occipital are angulated to it and to each other. Despite the matrix on the base of the cranium it was possible to see the foramen ovale, the carotid canal, the hypoglossal canal and the condylar canal on each side. It was not possible to say whether the base of a styloid process is present, but the glenoid fossa on each side is deep and wide, though relatively narrow antero-posteriorly. It appears to be bordered by a well-developed articular eminence and a prominent but thin post-glenoid tubercle. This tubercle lies directly anterior to, but distinct from, the thin and relatively vertical tympanic plate and they enclose a triangular area of the floor of the root of the zygomatic process which overhangs the external auditory meatus. The tympanic plates and petrous bones are apparently only slightly angled in relation to each other. The mastoid processes are not visible and are probably missing through damage on both sides. The infratemporal fossa is deep, but short in an antero-posterior direction. The palate is moderately deep and smooth with a virtually straight alveolar margin between the position of the canines, behind which are posteriorly diverging tooth rows (see measurements in Table 1). The left premolars are subequal in crown area as are the first and second molars. The third molars are very reduced in size (see Appendix) and the right third molar has two well-developed distal roots visible. The central incisive fossa

1

100

Figure 6. Basal radiograph

mm

1 of Petralona cranium.

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and two lateral foramina are visible, as are the inter-palatine and palato-maxillary sutures. The midline of the palate is not coincident with the sagittal plane of the cranial vault and this slight asymmetry is reflected in cranial measurements since the twisting of the face and palate results in a slightly smaller distance between points on the vault and face on the right side compared with the left. The zygomatic bones sweep back from the maxillae, the zygomatic processes of which emerge from a position lateral to the first molar. Radiographs

The lateral radiograph (Figure 2) shows a thick-walled cranial vault. The thick form of the occiput resembles that of the Sangiran 17 radiograph illustrated by Tillier (1975), but the measured maximum thickness at inion (25 mm) is probably matched only by the “Pithecanthropus VII” specimen amongst Homo erectus fossils (Sartono, 1971) and is much greater than in known Homo sapiensfossils. The degree of mastoid pneumatization appears comparable to that of Homo erectus fossils but the squamous part of the temporal is even more highly pneumatized in the Petralona cranium. The cranial wall posterior to the frontal sinus is very strongly defined and the inner and outer tables of the frontal bone are clearly defined almost to bregma, as in the archaic Homo sapiens skull from Broken Hill. The anterior wall of the supraorbital torus is thinner than in Homo erectus fossils and is comparable to archaic Homo sapienscrania such as the last glaciation Neanderthal crania from La Ferrassie and La Chapelle (Tillier, 1975). The facial radiograph (Figure 4) again shows thick cranial walls, but its most remarkable feature is the development of the frontal sinus which far exceeds in size that of any other Pleistocene fossil hominid illustrated by Tillier (1975). The sinus is divided into two main chambers by a central septum and, as in the Broken Hill cranium, there are subchambers. The frontal sinus occupies the entire breadth of the supraorbital torus except for the parts lateral to the orbits and although the medial height of the sinus is comparable to that of the archaic Homo sapienscranium from Broken Hill, the total area pneumatized is much greater in the Petralona specimen. The large maxillary sinuses can be seen to extend slightly below the level of the nasal floor, and the ethmoidal sinuses are also well developed. The basal radiograph (Figure 6) illustrates the slight asymmetry of the face and palate in relation to the midline of the vault. The right maxillary sinus can be seen clearly and there is a very large sphenoidal sinus, extending into the basioccipital. These radiographs provide important information on the evolutionary development of features such as the frontal sinus. Previous evolutionary schemes have argued for a gradual increase in frontal pneumatization in the later evolution of Homo sapiens,and in the case of the Neanderthals the lateral extension of the frontal sinus has been seen as a specialized evolutionary development (VlEek, 1969; Heim, 1974). The fact that the Petralona skull shows the greatest degree of pneumatization seen in any Pleistocene hominid cranium calls for a complete reassessment of previous evolutionary schemes concerning pneumatization. However, studies of the significance of sinuses must also take account of their variability in modern and fossil populations (Brothwell, Molleson & Metreweli, 1968) particularly as the middle Pleistocene fossils from Arago and Steinheim appear to have relatively small frontal sinuses (Tillier, 1975). Affinities of the Petralona cranium At present there is no consensus of opinion amongst palaeoanthropologists on the classification of various middle and upper Pleistocene hominids. In the first part of this discussion specimens from Choukoutien, Sangiran, Trinil, Ngandong, Koobi Fora (KNM-ER-3733), Ternifine and Olduvai (O.H. 9) will be regarded as members of the

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species Homo erectus, whilst fossils such as those from Bodo (Conroy et al., 1978), Broken Hill, Arago, Swanscombe, Steinheim and Vertesszijllijs will be regarded as “archaic Homo sapiens”. Probable earlier Neanderthal crania such as the Saccopastore specimens will be differentiated where necessary in the discussion from last glaciation European and southwest Asian Neanderthal fossils. The classification of the Mauer (Heidelberg) mandible and the Bilzingsleben material [regarded as representing a new subspecies of Homo erectus by VlCek (1978)] will be discussed below. The Petralona cranium is larger than any Homo erectus calvaria and crania in its principal dimensions although Sangiran 17, Ngandong 6 (“Skull V”) and Olduvai hominid 9 match or exceed the specimen in certain measurements. Comparative analyses have shown that there are resemblances in shape between the Petralona and Homo erectuscranial vaults (Corruccini, 1974; Stringer, 1978) but the Petralona cranial capacity of about 1200 ml (probably to be regarded as a minimum value) is larger than estimated values for African Homo erectus crania and is at the top end of the range of values for Asian Homo erectus specimens. However it is at the lower end of the range of values quoted for archaic Homo sapiensfossils and is well below values typical of Neanderthal and anatomically modern crania. The broad flattened frontal bone of the Petralona cranium bears more resemblance to African, rather than Asian, Homo erectus crania, since in many examples of the latter the frontal bone tends to be narrower and more vaulted, with a slight sagittal keel (although the Bodo frontal bone is apparently also keeled). The Petralona frontal bone also resembIes that of the Arago and Broken Hill archaic Homo sapiensspecimens, but differs from the more expanded frontal bone form typical of Neanderthal and modern man. There is only a slight and divided sulcus separating the superior part of the frontal bone from the supraorbital torus, which is well developed but less well-defined than in most Homo erectus and archaic Homo sapienscrania. The lateral development of the torus is greater than is found in Neanderthal specimens, but is less than that found in Homo erectus crania, and in the archaic Homo sapiensfossils from Broken Hill, Bodo and Arago. In its division into two arches, and in the medial position of greatest thickness, the torus most resembles that of European archaic Homo sapienscrania such as those from Arago and Steinheim. However, in the lateral recession and pneumatization of the supraorbital region the Petralona fossil is more like the Broken Hill and European Neanderthal crania. The face of the Petralona specimen is massive but especially broad in the upper face where the large biorbital and interorbital breadths relative to orbital and nasal height align it with middle Pleistocene and early Neanderthal crania, rather than with late Neanderthal or anatomically modern crania. The Arago, Bodo and Broken Hill archaic Homo sapiensspecimens and the Saccopastore 2 early Neanderthal fossil seem most comparable to the Petralona cranium in overall facial form, but the Steinheim specimen seems more distinct from the Petralona cranium in both size and shape, although comparable to the Petralona fossil in certain indices and morphological details (Stringer, 1978). The relatively small external nasal opening of the Petralona fossil contrasts with that found in late Neanderthal specimens, although the form of the nasal bones is reminiscent of those of European Neanderthal crania. However, the flattened middle face does not resemble the presumably derived condition of extreme mid-facial projection evident in late European and southwest Asian Neanderthal crania, and which is present to a lesser extent in the Broken Hill specimen. Here the form of the Petralona face resembles Homo erectus and anatomically modern crania (Stringer, 1978). The relative orientation of the face to the vault also differentiates the Petralona specimen from late Neanderthal crania since the cranial base appears to be well flexed as in the Steinheim and Broken Hill archaic Homo sapienscrania, and as in the Sacco-

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pastore early Neanderthal fossils. This flexion is also reflected in the relatively short and deep infratemporal fossae of the Petralona cranium. These characteristics, as well as a relatively broad face, palate and cranial base, also relate the Petralona specimen to the upper Pleistocene cranium from Djebel Irhoud in Morocco, although in other respects the latter fossil is much more similar to anatomically modern and Neanderthal forms of Homo sapiens(Stringer, 1978). The Petralona palate has a large surface area and a distinctive angular shape when compared with archaic and Neanderthal fossils of Homo sapiens, but crown areas calculated for the dentition show that the Petralona teeth, whilst matching in size those of some Homo erectus specimens, are within the size range of archaic Homo sapiensand Neanderthal dentitions (Murrill, 1974). The tooth proportions resemble those of the Arago 21 palate, with a similarly large second molar, but the third molar is relatively less reduced than in the Arago 21 and Steinheim archaic Homo sapiens specimens. We have not been able to study the dentition of the Steinheim specimen for comparison with the Petralona dentition, but measurements on the best available cast suggest that the differences in size between the Petralona and Steinheim teeth are less than the differences between the two Arago mandibles (which are presumed to represent male and female individuals drawn from the same “population”). However as discussed below, there are still other reasons (temporal, metrical and morphological) which suggest caution before assuming that the Steinheim cranium represents a female of a “population” from which the Petralona cranium has been drawn. The parietal bones of the Petralona specimen are high and long in a sagittal and lateral direction compared with those of many Homo erectus, archaic Homo sapiens and Neanderthal fossils, a fact which is reflected in the relatively large basibregmatic height and bregma-asterion chord, and the low parietal angle (Stringer, 1978). There are no parasagittal depressions, although there is a slight degree of flattening and a slight anterior keel as in some Homo erectus and archaic Homo sapienscrania (e.g., the Bodo, Broken Hill and Omo-Kibish 2 specimens). The parietals are robust with a thickness at the mastoid angle of 11-12 mm, greater than is found in archaic Homo sapiensfossils (with the probable exception of Bodo) but less than in the majority of Homo erectus crania and calvaria for which data are available. Although the occipital bone is strongly angulated as in Homo erectus specimens and in the archaic Homo sapienscrania from Broken Hill, the occipital torus is less prominent externally. Nevertheless the torus is well-developed centrally, is continuous, and there is no supratoral fossa characteristic of early and late Neanderthal fossils, and which is also found in the Swanscombe and Steinheim archaic Homo sapiens specimens (Howell, 1960; Santa Luca, 1978). The occipital torus does not extend on to the parietal and temporal areas, and the torus itself is located relatively inferiorly since the Petralona specimen does not display the posteriorly rotated nuchal region typical of Homo erectus fossils. The extensive but flat occipital torus of the Petralona cranium superficially resembles a Neanderthal “chignon” but the occipital projection in Petralona is caused by a great thickening of the occipital wall rather than a projection of it. As also suggested by Wolpoff (1977), the closest match for the Petralona occipital morphology is found in the Vertesszollos occipital, and the still continuous torus in these two specimens could be seen as the precursor of the distinctive European occipital structure found in archaic Homo sapiensspecimens such as the fossil from Swanscombe and in the early and late Neanderthals. The nuchal plane in both the Petralona and Vertesszbllos occipitals is long and bordered by the inferior rim of the occipital torus, but the VCrtesszGllbs specimen, although apparently less thick, exceeds the Petralona occipital in general dimensions. The occipital angle is wider and the occipital height greater suggesting a cranial capacity outside the generally accepted range for Homo erectus. As the recently discovered Bilzingsleben occipital is reported to be smaller, thicker and more angulated than the

HOMINID

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247

Vertessziilliis and Swanscombe occipitals (VlEek, 1978) this Holsteinian fossil may resemble the Petralona specimen in morphology. The temporal squama resembles that of archaic Homo sapiens and Neanderthal specimens in lateral view, but the squamae are flat and robust with an inferior and posterior divergence from the sagittal plane reminiscent of Asian and African Homo erectus specimens. The development of a supra-auricular tegmen is perhaps an archaic feature but the meatal wall is thin and the tympanic plate is relatively vertical and only slightly angled in relation to the petrous bone. There is no suprameatal spine and the deep but anteroposteriorly narrow glenoid fossa is apparently bordered by a welldeveloped articular eminence and post-glenoid tubercle. This combination of characteristics differentiates the Petralona fossil from both Asian Homo erectus and late Neanderthal crania. Full comparisons with African Homo erectusfossils are not possible from available descriptions, but the overall morphology of the temporal area of the Petralona cranium appears most similar to that of the Broken Hill cranium, and to European archaic Homo sapiensfossils such as those from Saccopastore. With the relative wealth of middle Pleistocene mandibular material from Africa and Europe (Aguirre & de Lumley, 1977) it is unfortunate that the Petralona cranium lacks its mandible. Nevertheless, the form and position of the glenoid fossa, narrow infratemporal fossae, orthognathous face, wide palate and relatively small teeth impose a number of constraints on the kind of mandible which could articulate with the Petralona cranium. The middle Pleistocene Mauer mandible has an insufficient bicondylar breadth, while the great breadth and verticality of the Mauer ascending ramus would bring the coronoid processes directly against the postero-lateral surfaces of the Petralona maxillae. Additionally the Mauer dental arcade is both too narrow and relatively too anterior for satisfactory articulation with the Petralona upper jaw. A better occlusion is provided by the Ternifine 1 Homo erectus mandible, but the more complete Ternifine 3 specimen is too massive to fit the Petralona cranium. The Petralona mandible probably had a large bicondylar breadth combined with a dental arcade like that of the Ternifine Homo erectus specimens, and a relatively narrow or sloping ascending ramus like that of the Arago 13 and Montmaurin archaic Homo sapiensmandibles. The internal architecture of the anterior parts of the Petralona cranium belies the apparent robusticity of the brows and face. Radiographs reveal that the massive zygomatic, maxillary, supraorbital and interorbital areas are primarily thin bony coverings formassive sinus chambers.The contrast between the thick posterior cranial walls and the anterior highly pneumatized areas of the Petralona fossil is very marked. The apparent correlation in pneumatization shown by the frontal, ethmoid, maxillary, basisphenoid and temporal areas of the Petralona cranium shows that it is incorrect to assume that there was a progressive and derived increase in pneumatization in the evolution of Homo sapiens. Conclusions

From its morphology and dating it is clear that the Petralona cranium could represent a sample from a population ancestral to later European middle and upper Pleistocene hominids. It appears to be closely related to European archaic Homo sapiensfossils such as those from Arago, Vertesszijlliis and Bilzingsleben and perhaps to those from Steinheim and Swanscombe. It is also morphologically similar to the Bodo and Broken Hill crania, which are perhaps its African equivalents in evolutionary grade. Although more like the Broken Hill specimen in general dimensions it seems to resemble Bodo more than Broken Hill in terms of cranial thickness. The low cranial capacity, thick occipital and parietals, angular vault, and angulated occipital with continuous occipital torus all

248

C. B. STRINGER

ET AL.

point to the classification of the Petralona fossil as Homo erectus rather than Homo sapiens, but if the cranium is so classified it would have to be recognized as a variety which was quite distinct from Asian and African examples of Homo erectus and which was closely related to European and African middle Pleistocene hominids. One of the present authors (J.K.M.) feels that this is the correct taxonomic placement for the Petralona fossil. Alternatively the cranium could be classified as a primitive form of Homo sapiens and grouped with other fossils to form a taxon whose members share some apomorphous characteristics in cranial structure common to Neanderthal and anatomically modern man. These features would include an increase in cranial height and parietal expansion (associated with an increase in cranial capacity), changes in temporal morphology, reduction of the occipital torus, downward rotation of the nuchal area, lengthening of the occipital plane and progressive lightening of cranial superstructures through either external or internal reduction. However, the taxon would be distinguished from later forms of Homo sapiens by the lack of other apomorphous characteristics in the temporal region, face, vault, endocranium and cranial base shown by Homo sapiens neanderthalensis and Homo sapiens sapiens, and by the greater retention of some plesiomorphous characteristics of the face, cranial vault, endocranium and dentition shared with Homo erectus which have been lost in Neanderthal and anatomically modern forms (Stringer, 1974; Howells, 1975; Wolpoff, 1975; Santa Luca, 1978). Lack of evidence precludes the use of post-cranial features. Comparative studies of middle Pleistocene mandibular material suggest that European specimens such as those from Heidelberg, Arago, Montmaurin and Atapuerca are closely related, and that they, in turn, are more closely related to African rather than Asian fossils of Homo erectus (Aguirre & de Lumley, 1977). As already discussed, the Petralona mandible must have differed morphologically from the Mauer specimen, but allowing for the degree of variability manifest within the Ternifine sample and the Arago sample it would be reasonable to extend the range of variation of the group containing the Petralona cranium to include the Mauer mandible. The subspecies name heidelbergensis is available for this group which could be regarded as a grade of Homo sapiens intermediate between Homo erectus and late forms of Homo sapiens as one of us has suggested (Howells, 1978). A possible cladogram illustrating the relationship is

Figure 7. Phylogenetic position of the Petralona cranium (P).

HOMINID

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shown in Figure 7 (i). However Bonde (1977) has already discussed the difficulty in treating subspecies in such a system and would advocate instead a cladogram and classification such as that shown in Figure 7 (ii). Certainly subspecies terms are most appropriately used geographically, and the relationship between the various subspecies named by Campbell (1964), and Homo sapiensheidelbergensis,would be problematical unless all the subspecies were defined in comparable ways. If Homo sapiensheidelbergensis was ancestral to Homo sapiens steinheimensisand the latter subspecies was in turn ancestral to Homo sapiensneanderthalensis,then African fossils such as Bodo and Broken Hill could hardly be placed into the same subspecies as the Petralona specimen unless they conformed to this same evolutionary scheme in Africa, or Homo sapiens heidefbergensiscould be regarded as the widespread common ancestor for all later forms of Homo in Europe and Africa. On the other hand Bonde’s scheme [Figure 7 (ii)] has its own drawbacks. Despite the presence of some autapomorphous (unique derived) features in the Neanderthals, it is difficult to accept that they constitute a distinct species from Homo sapiens,since other aspects of their morphology are clinal when compared with the morphology of modern man. The archaeological evidence from southwest Asia clearly indicates that late Neanderthal and early anatomically modern forms existed almost or completely contemporaneously, produced similar cultures, and led comparable ways of life. To place them in separate species to satisfy a classificatory device seems to go against the aim of increasing the information content of the classification since it surely does not reflect biological reality. Equally, the re-erection of species such as H. heidelbergensisand H. neanderthalensiswould presage a proliferation of species names such as those which burdened palaeoanthropology before workers such as Campbell (1964) attempted to clarify the classification of members of the genus Homo. If a subspecies name cannot be applied as a grade term to forms such as Petralona and Broken Hill without implying a geographical or chronological unity, it might be better to suspend the use of subspecies names within Homo sapiensand use simple grade terms which do not have such implications. Fossils like those from Petralona and Broken Hill would represent “H. sapiensgrade I “, and the “early Neanderthals” might represent “H.sapiens grade 2”. However, it would then be necessary to place the late Neanderthals and modern H. sapiensas grades 3 and 4 respectively, implying a direct evolutionary relationship between these forms [Figure 7 (iii)], or to place one or other of the forms into a separate species. Much evidence can be presented both for and against the proposition that late Neanderthal man evolved into modern man [see, for example, Wolpoff (1975) and Stringer (1978)], but the problem seems no closer to resolution when some of the most crucial specimens are uncertainly dated. Yet another alternative would be to include all pre-modern forms which were clearly more advanced than H. erectusin a very widely defined taxon Homo neanderthalensiswith its own grade structure. This would be closer to the ideas expressed by workers such as Wolpoff (1975) but if autapomorphous characteristics can really be identified in the later Neanderthals it would be necessary to originate the lineage leading to modern man (Homo sapiens)before the evolution of “Homo neanderthalensisgrade 3” [Figure 7 (iv)]. A compromise solution would be to recognize two grades of Homo sapiensmore primitive than either the Neanderthals or anatomically modem man, and to split the third grade of Homo sapiensinto grade 3a (the late Neanderthals) and grade 3b (anatomically modern man) [Figure 7 (v)]. This would allow the grade system to operate without prejudging the relationship between modem and Neanderthal man, since group 3b could be derived from group 3a, given the known time-range of the grade, or from another part of grade 3 or from a part of grade 2. This system could also replace the use of subspecies names and terms such as “archaic sapiens” until such time as they can be more precisely defined, Distinctions

C. B. STRINGER ET AL.

250

between grades 3a and 3b could be due to geographic or evolutionary differences. Other specimens which are more “evolved” than grade 2 forms but which could not readily be accommodated into grades 3a or 3b (such as the Djebel Irhoud crania) would for the moment be allocated to grade 3, but without further subdivision. Grouping fossils into grades would not necessarily imply that the groups formed a biological unit such as a subspecies, nor that members of one grade were automatically regarded as ancestral to members of the succeeding grade. Relationships of the non-European fossils are more difficult to interpret, but if, for example, members of Homo sapiensgrade 2 could be divided into forms which through autapomorphous characters could be linked with either grade 3a or 3b, they could in turn be further subdivided into grades 2a and 2b. A tentative division of the more important specimens is presented in Table 2, as a basis for further discussion, mainly at this stage using morphoclines in cranial shape discussed in Stringer (1978), rather than detailed analysis of character states. Table 2. Suggested Homo sapiens grade structure Grade

Subgroup a

Homo sapiens grade 3

b ?

Examples: suggested types in italics La Ferrassie I ; La Chapelle; Shanidar; Amud; Tabiin; TeshikTash Omo (Kibish) 1; Qafzeh; Skh?il: Niah; Wadjak; Mungo; Cro-Magnon 1; MladeE Djebel Irhoud

-----------------

-2 a?

Saccopastore I; La Chaise; Ehringsdorf ; Fontechevade

Homo sapiens grade 2 ------------------

Homo sapiens grade 1

Specimens of less certain position

a?

Petralona; V&tessztilkis; Bilzingsleben

3

Broken Hill; Bodo

Border Cave; Klasies Cave; Iwo Eleru Singa Krapina; Zuttiyeh; Forbes’ or 3 Quarry; Omo (Kibish) 2; Florisbad Biache

Ndutu; Eyasi; Saldanha; 1 or 2 Steinheim; Swanscombe; Montmaurin; Atapuerca Mauer; Atgao Rabat; Sal6 Ngandong (alternatively regarded as Homo erectus)

Note: Groupings within each grade are not meant to reflect chronological evolutionary relationships.

or

The position of specimens such as Swanscombe and Steinheim presents some difficulties in the grade scheme. VlEek (1978) has suggested that the species Homo erectusand Homo sapiensmay have coexisted in Europe during the Holsteinian, and his views are based on differences between the Bilzingsleben fossils (which he allocated to a new subspecies of Homo erectus) and those from Swanscombe and Steinheim. Certainly there are equally great contrasts between the Petralona cranium and the fossils from Swanscombe and Steinheim in size, cranial thickness and occipital morphology, but these may well be due to the effect of both phyletic change and sexual dimorphism. The increasing complexity of middle Pleistocene correlations means that supposed Hoxnian/Holsteinian faunas and their associated hominids may well have spanned at least two distinct interglacials. A single lineage of European middle Pleistocene hominids should show considerable temporal variation in addition to geographic and normal population variability.

HOMINlD

251

SKULL FROM PETRALONA

The fortuitous absence of early middle Pleistocene hominid material in Europe provides a convenient limit for what might otherwise be a somewhat arbitrary taxonomic division between Homo erectus and Homo sapiens. Further fossil evidence is needed before the origin of Homo sapiens grade 1 in Europe can be determined, but the apparent resemblances between the Petralona, Bodo and Broken Hill crania seem to favour an African rather than Asian ancestry for the group. The allocation of certain other fossils to grades is problematical because of inadequate data or their “mosaic” nature. Because they are better known and relatively well dated, the European fossil hominids readily fall into such a scheme. Even if palaeoanthropologists do not adopt the full panoply of cladistic methods it is to be hoped that they will utilize the basic methods of analysis to improve the scheme presented in Table 2 and allow a more detailed and meaningful taxonomy ofthe fossil material to be developed. Whichever methods of analysis are adopted, the significance of the Petralona cranium remains the same. It is apparently the most complete fossil known of the most primitive grade of Homo sapiens. Further study of the Petralona specimen and more accurate dating evidence can only enhance its already great value to palaeoanthropology. Acknowledgements We would like to thank Dr P. Andrews, Dr B. Wood and Mr T. Olson for providing constructive criticism of the manuscript of this paper, and Professor B. Kurten, Dr A. Poulianos and Professor H. Schwartz for providing information about recent work in the Petralona cave. The radiographs were taken by Professor A. Christoforidis and Dr P. Papadopoulous. Funds towards the cost of travel for the collection of data were supplied to one of us (C.B.S.) by the Medical Research Council, the Boise Fund, Oxford, and the British Museum (Natural History). The opportunity for another one of us (F.C.H.) to examine the Petralona cranium was provided by a grant from the National Science Foundation. U.S.A. Appendix Dentition: Mesiodistal x labiolingual/buccolingual measurements necessarily approximate because closely packed).

right (CBS) MD C

p3

P4 M’ M2 M3

(8.6

-

7.9 12.4 11.5 10.5

LL/BL 9.5 root only)

-

12.2 13.0 13.9 13.1

crown measurements (M-D molars and premolars are

left (CBS) MD

LL/BL

94

8.9

8.5 8.1 12.0 11.7 10.1

11.8 11.5 13.0 13.6 12.9

-

--__ MD 9-3 8.0 7.5 12.1 11.2 11.1

WH) -BL/LL 9.2 11.7 11.25 13.0 13.5 12.8

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