Rare Temporal Bone Pathology of the Singa CalvariaFrom Sudan

FRED SPOOR,1* CHRIS STRINGER,2 AND FRANS ZONNEVELD3

1Evolutionary Anatomy Unit, Department of Anatomy and DevelopmentalBiology, University College London, London WC1E 6JJ, United Kingdom2Human Origins Group, Department of Palaeontology, The Natural HistoryMuseum, London SW7 5BD, United Kingdom3Department of Radiology, Utrecht University Hospital, 3584 CX Utrecht,The Netherlands

KEY WORDS Singa; paleopathology; CT; bony labyrinth; fossilhominid; anemia; parietal

ABSTRACT Evidence has recently accumulated that the Singa calvariafrom Sudan probably dates from Oxygen Isotope Stage 6 (.130 ka). Morpho-logical studies have indicated a mixture of archaic and more modern humantraits, but such analyses are complicated by the possibility that the vault ispathologically deformed, although the exact etiology has not been established.Now computed tomography (CT) has revealed that the right temporal bonelacks the structures of the bony labyrinth. The most likely cause of this rarepathological condition appears to be labyrinthine ossification, in which newlydeposited bone obliterates the inner ear spaces following an infectious diseaseor occlusion of the labyrinthine blood supply. A possible cause of vascularcompromise could have been the presence of an expanding acoustic neuromain the internal acoustic meatus, which is suggested by a significantly widerright meatus compared with the left side. Interestingly, labyrinthine ossifica-tion is also consistent with the controversial diagnosis that an anemia causedthe characteristic diploic widening at the parietal bosses, because primeetiological factors of ossification are among the common complications of someof these blood diseases. CT examination of the vault and a review of theliterature suggest that a blood disorder may well have caused the unusualparietal morphology. Given the nature of these pathological conditions, theSinga individual must have experienced a period of considerable disability.The morphological evidence from the normal bony labyrinth on the left sideand from the CT evaluation of the vault is consistent with the interpretationof Singa as a late archaic hominid or an early representative of Homo sapiensdrawn from a population which might be directly ancestral to modernhumans. Am J Phys Anthropol 107:41–50, 1998. r 1998 Wiley-Liss, Inc.

Since its discovery in 1924, the Singacalvaria has been rather neglected in stud-ies of recent human evolution. This hasoccurred partly because of doubts about itsgeological age and partly because its un-usual morphology has proved difficult tointerpret. The specimen was discovered atthe base of the seasonally exposed bed of theBlue Nile, in the district of Singa, about 320km south east (upstream) of Khartoum. It

was enclosed in a block of limestone calcrete(Woodward, 1938; Arkell et al., 1951). Puta-tively associated fauna and artefacts werealso collected at both Singa and at the

*Correspondence to: Fred Spoor, Evolutionary Anatomy Unit,Department of Anatomy and Developmental Biology, UniversityCollege London, Rockefeller Building, University Street, LondonWC1E 6JJ, UK. E-mail: f.spoor@ucl.ac.uk

Received 30 July 1997; accepted 11 June 1998.

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 107:41–50 (1998)

r 1998 WILEY-LISS, INC.

comparable site of Abu Hugar, some 15 kmto the south (Arkell et al., 1951). Bate (inArkell et al., 1951) described the faunalmaterial, arguing that it perhaps dated tothe early Upper Pleistocene. The only abso-lute age determination which was availablewas a radiocarbon date on a crocodile toothfrom Abu Hugar of 17,300 6 200 B.P., al-though it was recognized that there mighthave been contamination from younger car-bon (Whiteman, 1971). The artefacts fromSinga and Abu Hugar have been variouslyinterpreted as nondiagnostic (Marks, 1968),Middle Palaeolithic (Lacaille in Arkell et al.,1951; McBurney, 1977), or perhaps evenAcheulian (Brauer, 1984) in affinities.

The calvaria itself has also been subjectedto various interpretations. Woodward (1938)regarded it as a brachycephalic variant ofthe late Pleistocene ‘‘Boskop’’ race of south-ern Africa, while Rightmire (1984) and Clark(1988) regarded it as a late PleistoceneHomo sapiens. However, Tobias (1968),Brothwell (1974), and Stringer (1979) em-phasized its archaic characters, with Tobiasnoting anterior resemblances to Broken Hill,Brothwell pointing out ‘‘neandertaloid’’ fea-tures, and Stringer arguing for metricalsimilarities in shape to the Jebel Irhoudcrania (Fig. 1). Multivariate analyses byBrauer (1984) demonstrated the unique pa-rietal morphology of Singa.

Brothwell (1974) first raised the questionof possible pathology, arguing that its un-usual breadth and parietal expansion wasthe result of compensatory lateral growthfollowing premature synostosis of the sagit-tal suture. Stringer (1979) agreed that theparietal region was unusual and that thebregma-lambda chord was especially short.Reevaluation after preparation of the speci-men revealed unusual unilateral expansionof the sphenoid sinus and that the markedvault thickness at the parietal bosses isassociated with an expanded diploic layeralmost four times the width of the compactbone (Stringer et al., 1985). However, anattempt to identify the etiology was notsuccessful. In particular, no conclusive evi-dence was found for the hypothesis that thevault shape and diploic thickening were theresult of anemia, an opinion reiterated inStuart-Macadam (1992). On the other hand,

to Webb (1990) the morphology suggeststhat the Singa individual suffered from someform of blood disease.

More recently, attempts have been madeto date the Singa calvaria using the puta-tively associated fauna and calcareous matri-ces. Electron spin resonance (ESR) dateswere carried out on a supposedly associatedhorse and bovid tooth from Singa, suggest-ing an oxygen isotope stage 5–6 age (Grunand Stringer, 1991), while further ESR anduranium series dates, including some on thematrix around and within the calvaria, sug-gested an age in excess of 133 ka (McDer-mott et al., 1996). Moreover, chemical analy-ses of matrix on the calvaria and faunasupported their association, while modellingof uranium history clearly indicated a closerapproximation to linear uptake (LU). Thissuggests that the LU ESR age estimates onthe associated teeth in the range 140–160 ka

Fig. 1. Left lateral view of the Singa calvaria (top) incomparison with a cast of the Jebel Irhoud 1 cranium(bottom). The transverse and coronal planes of the CTscans of Singa, given in Figs. 2 and 3, are indicated bysolid lines and the fracture posterior to the parietalbosses by the dotted line. Scale, 12 cm.

42 F. SPOOR ET AL.

are likely to be most accurate. Thus, theSinga hominid probably does date from oxy-gen isotope stage 6 and therefore predatesall well-dated specimens of Homo sapienssensu stricto. It thus represents a rare sam-ple from a population which might approxi-mate the ancestral one for all modern hu-mans. Knowledge of its morphology and theextent to which this might have been modi-fied by possible pathological change is there-fore of considerable importance for humanevolutionary studies.

In the context of the ongoing morphologi-cal study of Singa, the internal structures ofits temporal bones were investigated usingcomputed tomography (CT). The principalaim was to image the bony labyrinth, whichhouses the sense organs of hearing andbalance and has been shown to providevaluable information in studies of hominidlocomotor behavior and phylogeny (Spoor etal., 1994; Hublin et al., 1996). Rather unex-pectedly, the CT scans revealed the absenceof the structures of the right bony labyrinth.This paper describes this unusual pathologi-cal condition not found previously in anyfossil hominid and discusses the possibleetiology. In a wider context, the questionarises whether this temporal bone pathologycan be linked with, and thus increase anunderstanding of, the other areas of abnor-mal morphology. Identifying a single under-lying disorder would help in attempts toeliminate pathological characteristics fromanalyses of Singa’s phylogenetic affinities.Apart from evaluating the pathology of theright temporal bone, this paper also brieflyconsiders the normal labyrinthine morphol-ogy on the contralateral side.

METHODS

The method of visualizing the internalmorphology of the temporal bone by CTfollows the procedures described in Spoorand Zonneveld (1994, 1995). The CT scanswere made with a Philips Tomoscan 350scanner (University College Hospital, Lon-don, August 1991) with an exposure of 480mA at 120 kVp tube voltage and a slicethickness of 1.5 mm. By replacing the stan-dard soft tissue beam hardening correctionbased on a plexiglas calibration with a spe-cial aluminium calibration, an extended

Hounsfield scale (CT number scale) wascreated to avoid overflow artefacts caused bythe high density of the mineralized bone andthe attached matrix (Spoor and Zonneveld,1994). Scans with a field of view of 240 3 240mm (matrix 256 3 256) were made in thetransverse (nasion-biporionic), sagittal, andcoronal planes as indicated in Figure 1 anddemonstrated in Figure 2a. Zoom reconstruc-tions of the temporal bone regions weremade with a field of view of 80 3 80 mm (Fig.2b,c). The scans were made contiguously,with an additional overlapping (slice incre-ment 0.75 mm) transverse scan at the levelof the lateral semicircular canal and anoverlapping sagittal scan at the level of thecommon crus. Measurements to the nearesttenth of a millimeter of the left labyrinthwere taken from the CT scans following themethod and definitions described in Spoorand Zonneveld (1995). Measurements of thelateromedial length and the inferosuperiorand anteroposterior diameters of the inter-nal acoustic meati were taken from trans-verse and coronal scans.

The endocranial surface morphology ofthe petrous pyramids was investigated us-ing an operating microscope with a coaxiallight source and a dental mirror.

DESCRIPTION

The left temporal bone is normally devel-oped in all aspects. Most of its internalspaces are filled with matrix of a higherdensity than the surrounding bone (Fig. 2c).In the bony labyrinth, the superior parts ofthe anterior and posterior semicircular ca-nals are air-filled, and an area of reduceddensity in the center of the vestibule sug-gests the presence of a bone fragment(Fig. 2c).

The labyrinthine measurements that havebeen shown to be important functionallyand phylogenetically in Middle and LatePleistocene hominids are the radii of curva-ture of the semicircular canals and the sagit-tal labyrinthine index (SLI), which de-scribes the proportion of the posterior canalsituated inferior to the plane of the lateralcanal (Spoor and Zonneveld, 1994; Hublin etal., 1996). The radii of curvature of theanterior, posterior, and lateral canals of the

43PALEOPATHOLOGY OF THE SINGA CALVARIA

left Singa labyrinth are 3.0, 3.1, and 2.3 mm,respectively, and its SLI is 46%.

Externally the right temporal bone is simi-lar in morphology to the left one, includingthe overall shape of the petrous part anddelicate details such as the endocranial aper-ture of the vestibular aqueduct. Its internalmorphology is marked by the absence of thestructures of the bony labyrinth. An irregu-lar space, partly filled with matrix, takes theposition of the vestibule (Fig. 2b). Moreover,a faint spot of slightly higher density thanthe surrounding bone marks the area of thecochlea, and an air-filled structure couldpossibly represent a remnant of the superior-most part of the anterior semicircular canal.In contrast, the tympanic cavity and allthree segments of the facial canal are nor-mally developed (Fig. 2b).

CT scans reveal that the middle part ofthe right internal acoustic meatus has aconsiderably larger vertical diameter thanthe left side, whereas both pori are approxi-mately equal in size. Measurements of thelength and the inferosuperior and anteropos-terior diameters, halfway between the porusand fundus, are 12.5, 6.4, and 4.4 mm, and12.0, 4.2, and 4.0 mm for the right and leftmeati, respectively. Direct observation of thelargely matrix-free right meatus confirmsthat the larger dimensions are not due toerosion. Its fundus is normal in morphologyand shows a well-developed falciform crest.The actual spiral part of the tractus spiralisforaminosus is covered by a remnant ofmatrix, but all other foramina can be ob-served.

DISCUSSION

The paleopathology of hominid fossils is ofimportance beyond a basic interest in theexpression of disease in skeletal remains. Inthe case of Singa, appreciating the full pat-tern of pathologies and the impact on themorphology is crucial in assessing its phylo-genetic affinities. Moreover, it may help inunderstanding the paleoepidemiology of thedisease involved, and the nature of thesymptoms may reflect on social aspects ofearly hominid behavior.

A first consideration is the differentialdiagnosis of the absence of labyrinthinestructures in Singa’s right petrous pyramid.

Fig. 2. a: Transverse overview CT scan at the levelindicated in Fig. 1. b,c: Zoom reconstruction of the right(b) and left (c) temporal bone areas, showing the vesti-bule (v) and the lateral semicircular canal of the normallabyrinth on the left and the irregularly shaped vesti-bule (v) as well as the intact second part of the facialcanal (f) on the right side.

44 F. SPOOR ET AL.

Possible causes include postmortem damageowing to the fossilization process, develop-mental deformity of the otic capsule, andbony obliteration of the labyrinthine lumenafter a normal development (e.g., for recentreviews of inner ear anomalies see Phelpsand Lloyd, 1990; Ballenger, 1991; Som andCurtin, 1996). The former option can bediscarded because the undistorted preserva-tion of the petrous pyramid, in particular offragile structures such as the facial canaland the falciform crest, clearly demon-strates that this area is free of postmortemdamage capable of obscuring the semicircu-lar canals and the cochlea.

The presence of an irregular central spaceinstead of a normal labyrinth could be inter-preted as a congenital, so-called commoncavity deformity, a persistent otocyst result-ing from arrested development (Jackler etal., 1987; Kavanagh and Magill, 1989). How-ever, this is unlikely, as the specimen doesnot show the hypoplastic petrous pyramidand internal acoustic meatus that character-ize such cases (Valvassori et al., 1969; Phelps,1974; Isenberg and Tubergen, 1979; Ka-vanagh and Magill, 1989). Also, in the areawhere the lateral semicircular canal wouldnormally be located, the medial tympanicwall shows a prominence (Fig. 2b), indica-tive of full development of the otic capsule.In contrast, this area is flat in cases ofcongenital dysplasia of the common cavitytype because the lateral canal never devel-oped (Curtin, 1988; Weissman and Kamerer,1993). Likewise, the normal morphology ofthe fundus of the internal acoustic meatusalso points at full development of the labyrin-thine structures.

Labyrinthine ossification, in which newlydeposited bone obliterates some or all of theinner ear spaces, appears to be the mostlikely explanation of the abnormal morphol-ogy seen in the Singa petrous pyramid.Many etiological factors have been reported,such as fractures, advanced otosclerosis, andcompromised vascularization, but most of-ten it is secondary to chronic infection of themembranous labyrinth (labyrinthitis ossifi-cans) (see reviews in Suga and Lindsay,1977; Swartz et al., 1985; DeSouza et al.,1991; Muren and Bredberg, 1997). Infec-tions reach the labyrinth from the tympanic

cavity (chronic otitis media), the meninges(meningitis), or occasionally via the blood-stream (septicaemia). Complete ossificationof the labyrinth may take many years (Papa-rella and Sugiura, 1967) but has also beenobserved within a period of a year (Hoffmanet al., 1979). Even in cases of total ossifica-tion, the internal acoustic meatus and thecochlear and vestibular aqueducts, struc-tures directly connected with the labyrinth,are not affected (Sugiura and Paparella,1967).

In the Singa specimen, ossification ap-pears to have proceeded to all labyrinthinespaces except the vestibule and perhaps themost superior part of the anterior semicircu-lar canal. Paparella and Sugiura (1967)observed that newly formed bone in thecochlea can be distinguished histologicallyfrom endochondral bone, but in the semicir-cular canals it completely blends with boneof the otic capsule. If we keep in mind thatany contrast between the otic capsule andnewly formed bone is likely to be diminishedby the fossilization process, this perhapsexplains why in the CT scans of the Singaspecimen only the cochlear area shows avague density difference, whereas no out-lines of the semicircular canals are visible.The cause of the ossification in the Singaspecimen is difficult to establish with cer-tainty, because most etiological factors, espe-cially the primary infections leading to laby-rinthitis, are not reflected in the morphologywhich is fossilized. This is the second re-ported case of pathology of the otic capsulein a hominid fossil. Previously, CT scansrevealed a likely case of cochlear otospongio-sis in the Forbes Quarry Neanderthal fromGibraltar (Zonneveld and Wind, 1985).

A striking feature of the right petrouspyramid of the Singa specimen, other thanthe obliterated labyrinth, is the 2.2 mm or52% greater vertical diameter of its internalacoustic meatus when compared with theleft side. Several studies have investigatedthe bilateral variation of the meatus dimen-sions in modern humans, using radiologicalor casting methods (Ebenius, 1934; Campand Cilley, 1939; Graf, 1952; Valvassori andPierce, 1964; Amjad et al., 1969; Papan-gelou, 1972). Of the total of 686 pairs oftemporal bones thus assessed, only 1.6%

45PALEOPATHOLOGY OF THE SINGA CALVARIA

showed a bilateral difference in vertical di-ameter of more than 2 mm (Table 1). Thisincidence led Valvassori (1969) to consider ameatus abnormal if it shows a widening of 2mm or more when compared with the samesegment on the opposite side, a criterionsubsequently cited in review works such asSchuknecht and Gulya (1986) and Phelpsand Lloyd (1990). The difference in verticaldiameter of 2.2 mm in the Singa calvariafalls in this category and deserves furtherconsideration.

Abnormal widening is usually associatedwith expanding, space-occupying lesions in-side the meatus, such as facial nerve neuro-mas, arachnoid cysts, and, by far the mostcommon, acoustic neuromas (Phelps andLloyd, 1990). Dolan et al. (1978) demon-strate that exceptions occur by presentingnine cases where widening did not corre-spond with any space-occupying lesion of themeatus. However, these cases were found byreviewing an unspecified body of archivalcase material and could easily represent the1.6% widening also found in anatomicalstudies.

If the widening is confined to the middlepart of the internal acoustic meatus, as seenin the Singa specimen, it most likely indi-cates a small intrameatal acoustic neuroma(primary intracanalicular eighth nerveschwannoma: Goodhill, 1979). The effects ofsuch an expanding lesion include compres-sion not only of the nerves but also of thelabyrinthine artery, the principle blood sup-ply to the inner ear. This results in degenera-tive changes of the membranous labyrinth(Perez De Moura, 1967; Belal, 1979), andboth clinical cases and experimental animalstudies indicate that arterial occlusion re-sults in bony obliteration of the labyrinth(Belal, 1979; Kimura and Perlman, 1958;

Paparella and Sugiura, 1967). Hence, anexpanding intrameatal lesion in the Singaspecimen, as suggested by the increasedinferosuperior diameter, is a possible candi-date for the cause of the observed labyrin-thine ossification through the mechanism ofvascular compromise. However, a nonpatho-logical origin of the bilateral difference inmeatal morphology cannot be completelyexcluded, given its occasional occurrence inmodern humans (Dolan et al., 1978)

Neither diploic thickening of the parietalsnor expansion of the sphenoid sinus, bothpreviously described as unusual morphologyof Singa (Stringer et al., 1985), are known toresult directly from any of the possible causesof labyrinthine ossification or from an ex-panding lesion in the internal acoustic me-atus. However, a potential common underly-ing cause for two of these, diploic expansionand labyrinthine ossification, is a hereditaryor acquired blood disorder. Anemias are thebest known cause of an increase of thediploic layer (Diggs, 1967; Moseley, 1974;Konotey-Ahulu, 1991; Ortner and Putschar,1985; Serjeant, 1992; Stoker, 1997), andsensorineural hearing loss has a well-knownassociation with sickle cell anemia (Cole andJahrsdoerfer, 1988; Donegan et al., 1982;Serjeant, 1992; Odetoyinbo and Adekile,1987). The likely mechanism underlying thisrelationship is that common complicationsof sickle cell disease, vasoocclusion, meningi-tis, or septicaemia, result in inner ear hem-orrhage, avascular necrosis, and labyrinthi-tis (Cole and Jahrsdoerfer, 1988; Donegan etal., 1982; Serjeant, 1992; Odetoyinbo andAdekile, 1987).As discussed previously theseare among the prime etiological factors of laby-rinthine ossification. Degenerative changesto the cochlea and hearing loss have alsobeen associated with acquired, mainly iron

TABLE 1. Bilateral differences between the vertical (inferosuperior) diameter of the internal acoustic meatusin modern humans, listing the percentage (%) of the sample with a specified difference

Source Number of pairs Difference Incidence in %

Ebenius (1934) 100 Over 2.0 mm 1Camp and Cilley (1939) 250 2.0 mm or more 2Graf (1952) 100 Over 1.5 mm 0Valvassori and Pierce (1964) 100 2.0 mm or more 0Amjad et al. (1969) 15 Over 1.0 mm 0Papangelou (1972) 121 2.0 mm or more 4

Total 686 Over 2.0 mm 1.6

46 F. SPOOR ET AL.

deficiency anemia (Yassin and Taha, 1965;Morrison and Booth, 1970; Morrison, 1978;Sun et al., 1992a,b). Furthermore, bacterialor viral infections, capable of invoking laby-rinthitis, may also cause hemolytic anemiasor an exacerbation of a previously existingchronic anemia (Dacie, 1995).

The finding that the newly discoveredtemporal bone pathology is consistent withanemia asks for a reexamination of theevidence that led Stringer et al. (1985) toconclude that there is little support for thisdiagnosis. The study defined seven criteriadescribing bony change in anemia that arevisible in radiographs (further commentedon in Stuart-Macadam, 1987) and reportedthat the Singa calvaria exhibits only one ofthese: diploic thickening of the parietals.The three other criteria pertaining to thevault, thinning of the outer table, hair-on-end trabecular appearance, and diploic tex-ture changes, could not be detected. Theseobservations must have been based on in-spection of the fracture surface posterior tothe parietal bosses (Fig. 1), because radio-graphs of Singa are inherently incapable ofrevealing details of the vault morphologyowing to the complete saturation of thediploic layer by matrix of a higher densitythan the fossilized bone (Figs. 2, 3). Webb(1990) assessed this fracture, and reportedthat both the inner and outer table are thin,each with a thickness of less than 1 mm.

With CT, it is now possible to visualize thevault structure at the center of the parietal

bosses, and a coronal scan suggests a similarvault morphology as seen at the fracture(Fig. 3). The outer table does not appear tobe markedly thinner than the inner table,and the thickness of neither table is specifi-cally reduced at the centers of the bosseswhere the diploic layer is most expanded.The thickened diploe is imaged as a virtu-ally homogenous layer, suggesting a finetrabecular pattern. However, establishingthe presence in the matrix-saturated diploiclayer of texture changes or radially orientedbone spicules, associated with the hair-on-end appearance in radiographs, is beyondthe limitation of the spatial resolution of theCT scans. Nevertheless, Singa clearly doesnot show the severe hair-on-end morphologyillustrated in the literature (e.g., Diggs, 1967;Moseley, 1974; Serjeant, 1992; Stoker, 1997)because it lacks the strongly eroded outertable with honeycombed compartments ofsubperiosteal new bone giving this radiologi-cal appearance (Ortner and Putschar, 1985).Webb (1990) suggested that, in addition tothe two parietal bosses, Singa also showsexpansion of the frontal, thus implying thatthe well-rounded shape of the forehead ispathological in origin. However, this is notsupported by the evidence from CT scans,which do reveal a well-developed frontalsinus but no obvious widening of the frontaldiploic layer.

Reviews of skeletal involvement in vari-ous types of blood disorders (Diggs, 1967;Konotey-Ahulu, 1991; Moseley, 1974; Ortnerand Putschar, 1985; Serjeant, 1992; Stoker,1997) suggest that the radiographic criteriaused by Stringer et al. (1985) to assess Singapertain predominantly to the most severemanifestations of anemia. Indeed, Singaclearly does not show the severe cranialchanges, such as of strong erosion of theouter vault table and inhibited developmentof the air sinuses, that mark thalassemias.On the other hand, it is more consistent withthe pattern observed for sickle cell disease,hereditary spherocytosis, and iron defi-ciency anemia, in which cranial changes areuncommon and restricted to widening of thediploic layer with possible thinning of theouter table and only occasionally the hair-on-end radiographic appearance. Diploic widen-ing and bossing that is restricted to the

Fig. 3. Coronal CT scans of the Singa calvaria at thelevel of maximum parietal bossing, as indicated in Fig.1. Note that the scan plane is not entirely perpendicularto the external surface, but this does not affect therelative proportions of the tables.

47PALEOPATHOLOGY OF THE SINGA CALVARIA

parietals, as seen in Singa, is the mostcommon pattern in these forms of anemia.Diploic expansion without obliteration ofthe outer table or the hair-on-end appear-ance has also been reported in Peruviancrania in the Hrdlicka collection (Ponec andResnick, 1984), in Willandra Lake Hominid50 (Webb, 1990), and in some of the Kanjerahominids (Plummer and Potts, 1995). Thepossibility raised in the latter study thatremodelling may have brought about anouter table of normal thickness after thedemand for hematopoietic tissue had de-clined with adulthood deserves further inves-tigation, for example by scanning electronmicroscopy or histological examination ofthe Kanjera specimens and the Singa cal-varia.

The suggestion of Webb (1990) that thediploic expansion seen in Singa is indicativeof hyperplastic marrow associated with someform of blood disease seems to be a plausibleone, given that its parietal vault morphologyappears distinctly different from that inother fossil hominids (Brauer, 1984; Stringer,1979; Stringer et al., 1985) and modernhumans, in a way that is broadly consistentwith the manifestation of some modern-dayanemias. Differentiating various types ofanemia in dry bone specimens is problem-atic (Ortner and Putschar, 1985), and in thecase of Singa such attempts would be particu-larly meaningless when considering the ageof the specimen in relation to the possibleage of hereditary anemias. For example,estimates of the origin of the sickle cell genevary from just 2,000 years ago (Kurnit,1979; Wiesenfeld, 1967) up to a range of70,000–150,000 years ago (Solomon and Bod-mer, 1979). Singa thus likely predates theorigin of sickle cell disease in its currentforms, and there is a real possibility that itsuffered from a blood disorder causing anincreased demand for hemopoietic marrowspace not known today. Future progress ininterpreting histological features of diploemodified by hyperplastic marrow or perhapsanalysis of ancient biomolecules could leadto a more definite diagnosis. Moreover, cur-rent systematic quantitative assessment ofthe vault structure in extant and fossilhominids on the basis of CT scans (Garcia,1995) will lead to a more secure differentia-

tion between pathologies and extremes ofnormal anatomical variation.

Extensive labyrinthine ossification as seenin Singa is rare, and the minimum timereported for this level to be reached is a year(Hoffman et al, 1979). It is therefore testi-mony to the fact that the Singa individualsurvived the original insult affecting thelabyrinth, whether this was vascular compro-mise, labyrinthitis following an infectiousdisease, or some other cause, regardless of apossible association with anemia. The conse-quence was complete and permanent unilat-eral loss of auditory and vestibular function,which results in deafness, spontaneous nys-tagmus, vertigo, postural imbalance, andataxia (Curthoys and Halmagyi, 1996;Swartz et al., 1985; Schwarz and Tomlinson,1994). The static symptoms gradually re-cover over a period varying from a few daysto a few months in a process known asvestibular compensation (Curthoys and Hal-magyi, 1996; Schwarz and Tomlinson, 1994).An expanding lesion in the internal acousticmeatus would have put pressure not only onthe labyrinthine vessels and the vestibuloco-chlear nerve but also on the facial nerve.However, this rarely results in gross facialdysfunction (Phelps and Lloyd, 1990).

It follows from the inferred pathologicalhistory that the Singa individual must havegone through a period characterized at thevery least by severely impaired body coordi-nation and at the worst by a life-threateninginfection such as bacterial meningitis orsepticaemia. In addition, there was the con-siderable handicap of permanent unilateralhearing loss and possibly any symptomsassociated with a blood disorder. Given thesecircumstances, it is debatable to what extentthe survival of the Singa individual wouldhave required care by others.

The morphology of Singa’s well-preservedleft bony labyrinth resembles that of bothmodern humans and Homo erectus. It lacksthe derived features of the Neanderthallabyrinth, most notably a relatively smallposterior semicircular canal with a mark-edly inferior position relative to the plane ofthe lateral canal (Hublin et al, 1996). Hence,the labyrinth does not support the sugges-tion of Brothwell (1974) that the Singa cal-varia shows neanderthaloid influences. On

48 F. SPOOR ET AL.

the other hand, the evidence from both thelabyrinth and from CT examination of thevault is consistent with the interpretation ofmost recent studies, which take into accountthe pathological parietal shape and regardSinga as either a late archaic hominid or anearly and primitive representative of Homosapiens (Stringer, 1979; Stringer et al, 1985;McDermott et al., 1996). These studies high-lighted resemblances between Singa and theJebel Irhoud crania (Fig. 1), which may be ofcomparable age (Grun and Stringer, 1991).Both may be drawn from a population ances-tral to modern humans, which lived in North-ern Africa some 150,000 years ago.

ACKNOWLEDGMENTS

We thank Robert Kruszynski for curato-rial assistance, Lorraine Cornish for clean-ing Singa, and Catherine Jones (UCH) andAngela Haydon (Philips Medical SystemsUK) for facilitating the use of the UCH CTscanner. We are grateful to Peter Phelps foruseful discussions on inner ear anomalies,Chris Dean, Jane Moore, and three anony-mous referees for helpful comments on themanuscript, and Chris Sym and Jane Pend-jiky for photographic assistance.

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