Paleoanthropology, Department of Early Prehistory and Quaternary Ecology and Senckenberg Center for Human Evolution and Paleoecology, Eberhard Karls Universität Tübingen, Rümelinstrasse 23, Tübingen 72070, Germany
Paleoanthropology, Department of Early Prehistory and Quaternary Ecology and Senckenberg Center for Human Evolution and Paleoecology, Eberhard Karls Universität Tübingen, Rümelinstrasse 23, Tübingen 72070, Germany
Cioclovina is one of the earliest reliably dated modern human fossils found in Europe. It was discovered in 1941, during phosphate mining of the Peştera Cioclovina cave, South Transylvania (Harvati et al., 2007) and constitutes a well-preserved calvarium (Fig. 1). The specimen is dated by recent direct AMS 14C to an age of 29,000+–700 ka (Olariu et al., 2003) and 28,510+–170 (ultrafiltration pretreatment; Soficaru et al., 2007) and assigned to the Aurignacian (e.g., Churchill and Smith, 2000). It preserves the cranial vault and much of its cranial base, while the face is almost entirely absent: only the frontal aspect of the orbits and the upper part of the nasal bones are preserved. The cranium is in good condition and appears to have suffered minimal postmortem distortion. The initial description by Rainer and Simionescu (1942) considered this specimen as a young female. Later studies (Smith, 1984; Harvati et al., 2007; Soficaru et al., 2007) are divided on this point. The overall morphology of the cranium is unquestionably modern human (Rainer and Simionescu, 1942; Necrasov and Cristescu, 1965; Harvati et al., 2007). Some authors have suggested the possibility of partial Neanderthal ancestry for Cioclovina based on their interpretation of the nuchal region (Soficaru et al., 2007; Trinkaus, 2007). According to this view, Cioclovina possesses a suprainiac fossa reminiscent of, though not exactly the same as, the Neanderthal condition often cited as a Neanderthal autapomorphic feature (e.g., Santa Luca, 1978). This interpretation has been disputed. Harvati et al. (2007) applied several criteria developed from the literature to recognize hybrids in the fossil record, including heterosis/dysgenesis, supernumerary teeth and extra sutures, and intermediate shape. None of these criteria suggested that Cioclovina might represent a hybrid. Harvati et al. (2007) further consider the suprainiac morphology of the specimen to lie within the normal range of modern human variation in this anatomical region.
Here, we describe the endocranium of the Cioclovina specimen, including the endocast, frontal sinus morphology, as well as the middle meningeal vessel and occipital venous sinus imprints. Where possible, we identify gyri and sulci, particularly on the prefrontal lobe. Some of these traits have been shown to differ between modern and fossil humans. We evaluate these anatomical features with special reference to Neanderthal and modern human endocranial morphology.
MATERIALS AND METHODS
This study was conducted on a computed tomography (CT) scan of the original Cioclovina calvaria. Scanning was performed using a Siemens sensation 64 medical CT scanner in the facilities of the Centrul De Sanatate Pro-Life SRL, Bucharest. The scanning direction was coronal (transverse). Slice thickness of 0.625 mm, X-ray tube voltage 120 kV and tube current 304 mA were used. All slices were formatted in the same size of 512 × 512 pixels. The reconstruction diameter and pixel resolution were 223 and 0.44 mm. The half-maximum height protocol (Spoor et al., 1993) was used to reconstruct each cranial surface from the CT scan via the software package Amira (Mercury Computer Systems, Chelmsford, MA).
To obtain an approximation of the total endocranial volume, missing parts of the cranial base were virtually reconstructed by using a modern human cranium as reference. We determined the reference by carrying out a generalized Procrustes analysis (GPA) and a subsequent principal components analysis (PCA) in form space (Mitteroecker et al., 2004) on 34 anatomical landmarks present in 25 modern human crania and Cioclovina and chose the specimen that was closest to the Upper Paleolithic calvarium in terms of Procrustes distance (Bookstein, 1991). The specimen closest to Cioclovina was a 20-year-old female of Southern African origin (VA24) with an endocranial volume of 1365.43 cc.
The missing area incorporates the medial part of the left cerebral fossa, the clivus, the anterior and posterior clinoid processes, parts of the dorsum sellae, the ala minor, the lamina cribrosa, and the posterior part of the orbital roof formed by the frontal bone. Using the open-source software Edgewarp3D (Bookstein and Green, 2002) and AMIRA 5.3, a three-dimensional (3D)-template of 508 anatomical landmarks (n = 34) and semilandmarks (n = 474) was created to capture the geometry of the complete endocranial surface of the reference. We estimate missing data using thin plate splines (TPS; Bookstein, 1991) by warping the complete reference cranium onto the target; in this case, the cranial remains of Cioclovina. This procedure aligns the reference and the target according to homologous anatomical landmarks present in both models. First, a TPS interpolation based on the anatomical landmarks was computed to warp all semilandmarks from the reference to Cioclovina. In this way, the reference and target are aligned according to the anatomical landmarks; and all semilandmarks are roughly estimated according to minimum bending energy of just the landmarks. In a following step, each semilandmark is projected onto the preserved parts of the respective endocranial surface of Cioclovina and slid along tangents to the surfaces. Landmarks on the reference that correspond to the missing area in Cioclovina were manually declared as “fully relaxed,” that is, missing, and are estimated according to the TPS algorithm. Finally, the estimated subcranial parts that are corresponding to the missing area in Cioclovina were fused with the original virtual endocast.
The virtual reconstruction (Fig. 2) was used for the quantification of the total endocranial volume and for visually assessing the morphological features of the endocranium. The analysis, segmentation, and measurements were performed using Amira 5.3.
Cioclovina's virtual endocast was aligned in dorsal view, and markers were placed on the left (FR-L) and right frontal pole (FR-R) and the left (OC-L) and right occipital pole (OC-R). In the right lateral view, the markers were placed on the vertex (V) and most caudal cerebellar pole (CP). These placements were checked with dorsal and posterior views. The endocast was then rotated to occipital view, and markers were added at the most projecting points laterally on both hemispheres of the cerebrum and at the most laterally projecting points of the cerebellum (at the outside edges of the sigmoid sinuses, if visible) and to the most laterally projected points of the endocast. Additional markers for lambda and bregma were placed with the endocast positioned in occipital and dorsal view, respectively. A series of distances and arcs were then calculated using Amira 5.3 and Rapidform XOR (Inus Technology).
Breadth measurements were taken from the dural sinus imprints at the following anatomical regions: superior sagittal sinus (SSS-B) transition curve between superior sagittal sinus and transverse sinus, right transverse sinus, and left transverse sinus (Rosas et al., 2008a). Each measurement was repeated three times by EFK, and the mean value is reported in the Results section (see below, Venus sinus imprints). Several linear measurements were also taken on the endocast following Holloway et al. (2004b) and summarized in Table 1. Fifteen of these were used in a PCA for a dataset including modern humans and fossil hominins, collected by one of the authors (RH). The specimens included are listed in Table 2, and the measurements included in the PCA are listed Table 3. The raw measurements were corrected for size, so that shape would be analyzed, by subtracting the log geometric mean of all measurements for each individual from each log-transformed measurement (thus, generating Mossiman shape variables; Darroch and Mosimann, 1985). We also performed the size correction using the logged endocranial volume instead of the logged geometric mean, with very similar results (not reported). Finally, we performed a discriminant analysis treating the Cioclovina endocast as unknown to be classified into one of the groups used in the analysis (modern human, Neanderthal, H. erectus [s.l.], Middle Pleistocence African, Middle Pleistocene Europeans, and H. habilis [s.l.]) on the basis of the 15 size-corrected measurements.
Table 1. Measurements (in mm) on the Cioclovina endocast
Maximum anterio-posterior chord L (mm)
Maximum anterio-posterior chord R (mm)
Maximum anterio-posterior dorsal arc L (mm)
Maximum anterio-posterior dorsal arc R (mm)
Maximum anterio-posterior lateral arc L (mm)
Maximum anterio-posterior lateral arc R (mm)
Maximum breadth chord (mm)
Maximum breadth arc (mm)
Bregma-lambda cord (mm)
Bregma-lambda arc (mm)
Bregma-basion chord (mm)
Bregma-deepest cerebellum (mm)
Bregma-asterion chord L (mm)
Bregma-asterion chord R (mm)
Bregma-asterion arc L (mm)
Bregma-asterion arc R (mm)
Bi-asterion breadth (mm)
Maximum cerebellar width (with sigmoid sinuses) (mm)
Maximum cerebellar width (without sigmoid sinuses) (mm)
Depth from vertex to lowest temporal poles (mm)
The distance of the Broca's cap from the midsagittal plane left (mm)
The distance of the Broca's cap from the midsagittal plane right (mm)
Maximum width across Broca's caps (mm)
Length from frontal pole L to most posteriorly projecting part of cerebellum (usually just under lat. sinus) (mm)
Length from frontal pole R to most posteriorly projecting part of cerebellum (usually just under lat. sinus) (mm)
Table 2. Samples used in the principal components analysis
H.habilis (s.l.): KNM 1470, KNM 1813, KNM 1805
H. erectus (s.l.): Daka, KNM 3883, KNM 3733, Trinil, Sangiran 2, 4, 12, and 17, Sambungmacan 3, Solo XI, Sin LE, SN IID, SinIIL, Hexian
H. neanderthalensis: Amud 1, La Chapelle, Spy 1 and 2, Quina 5
Middle Pleistocene Africans and Europeans: Arago XX1, Kabwe, Irhoud 1, Sale
Table 3. Eigenvectors of the first two principal components
Bilateral measurements are from the right hemisphere.
Maximum width across Broca's caps
Frontal pole to most posteriorly projecting part of cerebellum
Maximum anterio-posterior chord
Maximum anterio-posterior dorsal arc
Maximum anterio-posterior lateral arc
Maximum breadth chord
Maximum breadth arc
Depth from vertex to lowest temporal poles
Maximum cerebellar width (without sigmoid sinuses)
The virtual reconstruction of Cioclovina calvarium allows the inspection of the endocranial surface and the detailed anatomical description of endocranial features, which are not visible otherwise.
The frontal sinus.
The human frontal sinuses constitute two irregular air-containing cavities on the frontal bone, each communicating with the middle meatus of the ipsilateral nasal cavity through the fronto-nasal duct (Gray, 1918). The frontal sinus has been considered to be functionally, physiologically, and structurally important (Márquez, 2008), though its precise role is not clear. Our CT imaging revealed a bilateral absence of the frontal sinus in Cioclovina (Fig. 3A,D), in agreement with the observations of Rainer and Simionescu (1942) on a radiograph of the specimen. The frontal sinus region in Cioclovina is occupied by dense bony tissue with small air cells corresponding probably to a natural bony loss in the diploe and to vascular spaces. On the contrary, the frontal sinus on a modern comparative specimen (Fig. 3B,E) constitutes a well-defined asymmetric cavity extending up to high on the frontal squama. Krapina 3 (Fig. 3C,F) exhibits well-defined frontal sinuses which, however, are mostly extended in the area of the supraorbital torus, as seems to be typical for Neanderthals (Kindler, 1960).
The imprints of the middle meningeal vessels.
The endocranial surface of the neurocranium in the frontal and parietal regions is marked by imprints of the middle meningeal vascular network. To avoid any unnecessary confusion concerning the exact nature of the imprints observed on the endocranium, we use the term middle meningeal vessels, following Bruner and Manzi ( 2008). We scored the middle meningeal system for the derivation of the middle ramus from the anterior (Adachi's I), the posterior (Adachi's II), or both the main branches (Adachi's III; Bruner et al., 2005; Bruner and Manzi, 2008). In Cioclovina, the middle ramus on the left part of the cranium seems to have been formed from branches of both the anterior and posterior middle meningeal arteries. However, on the right side, the middle branch of the meningeal artery appears to have derived from the anterior branch alone (Fig. 4).
Venus sinus imprints.
The anatomical details of the occipital region and the occipital venous sinus imprints can be clearly observed on the endocranium of Cioclovina (Fig. 4). At the midsagittal plane, a marked crest (corresponding to the attachment impression of the falx cerebri) is visible. It crosses the internal occipital protuberance through which it is connected with the internal occipital crest (the insertion of falx cerebelli). The left cerebral fossa is deeper (more posteriorly protruding) than the right one, and the latter is crossed by the right sagittal sinus groove. A deep groove representing the SSS is observed at the superior region of the occipital squama. It becomes less marked laterally and at a distance of about 37 mm from the internal occipital protuberance deviates to the right to form the right transverse sinus. The left transverse sinus is obvious from roughly the midsagittal plane and forms a distinctive left transverse sinus.
The measurements of the breadths on the sinus imprints were taken where possible. The middle portion of the superior sagittal groove was not visible in the virtual reconstruction; therefore, this measurement was not taken. The breadth on the transition curve between the sagittal and the right transverse sinus groove was about 12.4 mm. The breadths of the right and left transverse sinus grooves were 10.5 and 5.6 mm, respectively. These values are within the normal ranges in modern humans and human fossils (Rosas et al., 2008b). There is an obvious right predominance of the posterior drainage system in Cioclovina.
A cranial endocast is a 3D replica of the endocranial cavity of the skull. Cranial endocasts allow the observation of some of the external features of the brain. The information on circulatory and nervous system of the endocranium as well as general shapes and volumes can be inferred from endocasts, and such information has been used to address the paleoneurology of fossil hominins (Connolly, 1950; Holloway, 1974; Holloway, 1983; Holloway and Kimbel, 1986; Bruner et al., 2003; Holloway et al., 2004a; Falk et al., 2005; Bruner and Manzi, 2008).
Among the most commonly described features of the brain hemispheres are the petalia asymmetries (protrusions of the hemispheres producing imprints on the inner skull surface); the Yakovlenian torque (a forward “torquing” of the structures surrounding the right Sylvian fissure relative to their counterparts on the left); and the asymmetry on the occipital horns of the lateral ventricles (a deeper projection on the left occipital bone is common; Toga and Thompson, 2003). The inferior aspect of the Cioclovina endocast allows the observation of such asymmetries. Cioclovina exhibits a protrusion of the right occipital lobe over the left, which is mainly attributed to the right sinus configuration creating the impression of a right occipital petalia (Fig. 4). When the sinus volume is accounted for, the left occipital lobe exceeds the right one in depth and volume, suggesting right handedness. However, a small anterior extension of the left frontal lobe over the right one is also observed.
Further features such as gyral and sulcal impressions are clearly visible on the Cioclovina endocast particularly on the third inferior frontal convolution, indicating a truly modern morphology, although definite parcellation into pars opercularis, triangularis, and orbitalis is difficult (Fig. 5). The occipital (Fig. 6) and parietal regions do show some convolutional relief, but it is very difficult to be certain whether a fragment of the inferior occipital or lunate sulcus is apparent on the left side. There is clearly no evidence for an anteriorly located lunate sulcus, and this region appears fully modern. On the temporal lobe of the right side, a middle temporal sulcus is apparent, dividing superior and inferior temporal gyri.
The estimation of the total endocranial volume for the Cioclovina endocast was based on a virtual reconstruction using a modern human cranium as reference. The missing part of the basicranium was reconstructed using TPS, obtaining a total volume of the Cioclovina of approximately 1498.53 cc.
The firsr two axes of the PCA account for 56.3% of the total variance. PC1 (35.7%) roughly separates modern humans and H. erectus (s.l.) specimens, although there is overlap. Neanderthals, Middle Paleolithic specimens, and H. habilis fall in between. PC2 (20.6%) reflects variation within the modern human sample (Fig. 7). Neanderthals are intermediate in their position between the Homo erectus and the modern human sample on PC1. Cioclovina falls within the modern human range along both axes. Although it is meaningless to calculate 95% confidence ellipses for the very small Neanderthal sample, it is worth mentioning that Cioclovina falls outside the Neanderthal range (Fig. 7).
Table 3 lists the eigenvectors of the first two principal components. PC1 is influenced mainly by the bregma-lambda chord and arc measurements (loading negatively) and to a lesser extent by the maximum breadth chord, the bi-asterion breadth and the maximum cerebellar width (all loading positively). The H. erectus specimens are, therefore, characterized by endocasts with shorter bregma-asteriod chors and arcs, as well as greater maximum breadth chords, bi-asterion breadths, and maximum cerebellar widths, compared to modern human endocasts (although overlap exists in these shapes). PC2 reflects mainly differences in the maximum breadth arc (loading negatively), and to a lesser extent, in the maximum anterio-posterior chord and the length from frontal pole to most posteriorly projecting part of the cerebellum (both loading positively). Specimens with more negative PC2 scores, therefore, are characterized by greater maximum breadth arcs and smaller anterio-posterior lengths relative to specimens with more positivie PC2 scores (which include the fossils in this analysis).
The discriminant analysis classified Cioclovina as a modern human with posterior probability of 0.59 (the next highest probability was for H. erectus at 0.18 and for African Middle Pleistocene hominins at 0.16). Cross-validation classification showed that 92% of modern humans were classified correctly (one misclassified as H. habilis, one as Middle Pleistocene African, and four as Neanderthals); 60% of Neanderthals were correctly placed (with the remaining two specimens classified as Middle Pleistocene Africans); 71.4% of H. erectus was correctly classified (with one specimen classified as H. habilis, one as Middle Pleistocene African, 1 as Neanderthal and 1 as H. sapiens).
The frontal sinus morphology has been widely discussed in a phylogenetic context and emphasis has been given to its implication in anatomical function and climatic adaptation (e.g., Márquez, 2008). However, the difficulties in ascertaining their homology in fossils impede the understanding of their phylogenetic significance. Furthermore, among modern humans, the degree of anatomical variability reported for several temporally and spatially distinct populations (Buckland-Wright, 1970; Kupczik, 1999; O'Higgins et al., 2006) is so high that the anatomy of the frontal sinus is considered a unique cranial feature extensively used in forensic identification (Quatrehomme et al., 1996; Christensen, 2004; Cox et al., 2009). Frontal sinus agenesis in Cioclovina as extrapolated by the CT reconstruction confirms the observation of Rainer and Simionescu, (1942) inferred by means of radiography. This condition is rare in some populations of modern humans, but frequent in others, and is generally not observed in Neanderthals. The absence of the frontal sinus has been reported at a frequency of 95% in a Mesolithic population from Sudan (Greene and Scott, 1973), but 5% in Australians of European extraction (Schuller, 1943), while in sample of Pleistocene–Early Holocene fossils from Tanzania, two of five specimens exhibited extremely small frontal sinuses (Mumba VI, Strauss III; Kupczik, 1999). The high variability in modern human frontal sinus configurations has been attributed, among other factors, to the extent of distribution of masticatory stresses on the face (Greene and Scott, 1973). Neanderthals on the other hand appear heavily pneumatized, although pneumatization appears to be mainly constrained to the supraorbital torus region (Fig. 1; Kindler, 1960).
The middle medial meningeal system is thought to have undergone marked changes during human evolution (Grimaud-Hervé, 2004), possibly due to its major role in metabolism and thermoregulation (Bruner and Manzi, 2008). In modern humans, the anterior and middle rami are usually predominant compared to the less developed posterior branch, although this pattern is variable (Grimaud-Herve, 2004). The anterior ramus is found to be more (e.g., Gibraltar 1 and 2) or equally (e.g., Le Moustier) predominant to the posterior ramus in Neanderthals and Pre-Neanderthals (Grimaud-Herve, 2004). In Cioclovina, there is a bilateral asymmetry in the pattern of the middle meningeal vessels. On the left side anterior and posterior rami seem to be equally dominant both giving rise to the middle ramus. However, on the right side, the anterior branch is more predominant and gives rise to the middle ramus, with which it shares a large number of anastomoses. While the former pattern characterizes modern humans, the latter is observed in both modern humans and Neanderthals.
A recent comparative study of venous sinus topology in human fossils did not find a straightforward relationship between the venous sinus shape and brain size in Neanderthals and modern humans (Rosas et al., 2008b). Cioclovina exhibits a clear right predominance of the posterior drainage system, with breadth values that fall within the normal range of both modern and other Pleistocene fossil humans (Rosas et al., 2008b).
Hemispheric asymmetries are commonly thought to reflect hemispheric dominance and handedness in modern humans. In Cioclovina, the right occipital lobe gives an impression of a posterior protrusion, but careful observation reveals that this protrusion results from the configuration of the right venous sinus. The left occipital lobe is larger than the right one in both width and total volume, suggesting right handedness. The slight anterior projection of the left frontal lobe is of minor importance, as the distance of the Broca's cap from the midsaggital plane is almost equal in both sides of the endocast (see Table 1). Therefore, we suggest that left hemispheric dominance and right handedness is the most likely interpretation. The Cioclovina endocranial volume is well within the range of modern humans, and falls near the average value reported for modern people. Finally, a PCA analysis of 15 size-corrected measurements again places the shape of the Cioclovina endocast with that of modern humans. It is further classified as a modern human based on a discriminant analysis of the same size corrected measurements.
Our examination and description of the Cioclovina endocast and endocranial morphology show a clearly modern human pattern in this Upper Paleolithic European individual. The specimen displays some idiosyncratic features, such as frontal sinus agenesis and right-left asymmetry in the middle meningeal vessel pattern. However, as far as can be determined, its gyral and sulcal configuration is modern human-like, its estimated endocranial volume falls well within the modern human range of variation, and its endocranial shape places it with modern humans rather than fossil hominins, including Neanderthals.
The CT scan of the modern Greek used in Fig. 1B,D was obtained through funding from the Institute for Aegean Prehistory. Concerning the modern human reference sample, the authors thank Antonio Rosas González (Museo Nacional de Ciencias Naturales, Madrid, Spain) and G. W. Weber (Department of Anthropology, Vienna, Austria) for access to CT–data. The “NESPOS Database  Neanderthal Studies Professional Online Service (http://www.nespos.org) was used to produce Fig. 1C,F. E.F. KRANIOTI thanks Antonio García Tabernero for his most valuable advice on 3D virtual tools. Special thanks to David Ramon for his contribution in preparing the 3D virtual approximation of the middle meningeal vascular network and the venous sinuses drainage system, illustrated in Fig. 2A,B.