Time for one of the last Neanderthals

by Jennifer L. Thompson and Alan Bilsborough

Contents

Introduction
Neanderthal features
Neanderthal features present in Le Moustier 1

Cranial size and shape
Frontal
Temporals
Occipital
Mandible
Maxilla & Midfacial Prognathism
Postcranial skeleton

Features reflecting the youth of Le Moustier 1
Unique features of Le Moustier 1
Discussion and Conclusions
Bibliography

Abstract: Le Moustier 1 is an adolescent Neanderthal from the site of Le Moustier in the Dordogne of France. This specimen dates to about 40,000 years ago or less, making it among one of the last Neanderthals of western Europe. Due to historical circumstances, the specimen has only recently become available for study and so a description of its Neanderthal morphology is warranted. This paper outlines many of the characteristics commonly associated with adult Neandertals and assesses their presence and absence in the Le Moustier 1 specimen. In the majority of characters, the specimen resembles adult Neandertals, but in several cases departs from the typical Neandertal condition. This departure has more to do with ontogeny than phylogeny and can in most cases be linked to the immature status of the individual.

Keywords: Neanderthals, Le Moustier 1, Human remains.

Date of Submission: 16th July 1998; Date of Uploading: 23rd September 1998.

Introduction

The two rock shelters at the site of Le Moustier, Dordogne, France occupy a central place in prehistoric studies. The site is famous, not only because it is the type site of the Mousterian industry, but also for its fossil hominid remains. The two important fossil hominids are the skeleton of a Neanderthal youth (Le Moustier 1) discovered by Otto Hauser in 1908 (Hauser 1909; Klaatsch and Hauser 1909; Thompson and Bilsborough 1997) and the remains of a young child (Le Moustier 2) recovered by D. Peyrony in 1914 (Peyrony 1930; Bordes 1972).

Because of the poor circumstances of recovery, we cannot be sure of the exact provenience of Le Moustier 1, but it is widely accepted that the specimen was intrusive into layer H (containing Mousterian of Acheulean Tradition B), but that the individual likely lived during the time when layer  was deposited - a layer containing typical Mousterian tools (Laville, Rigaud and Sackett 1980; Bordes 1959; Bourgon 1957; Vandermeersch 1965; Stringer and Gamble 1993). There have been several attempts to date these layers using TL and ESR techniques. According to Mellars and Grün (1991), the Le Moustier 1 specimen cannot be older than 40-42,000 years. In fact, the specimen may be much younger, even as young as 37,000 years BP or less, which qualifies it, along with specimens like St. Cesaire, as one of the last Neanderthals from Western France (Valladas et al., 1986).

The specimen was sold to the Berlin Museum für Völkerkunde (Ethnological Museum) in 1910. The skull of Le Moustier 1 has undergone four major reconstructions in the past: the first and second by the anatomist, H. Klaatsch, the third by E. Krause, and a fourth by H. Weinert (Klaatsch 1909a, b; Schuchhardt 1912; Dieck 1923; Weinert 1925). The postcranial bones were largely destroyed during a bombing raid in latter part of the second World War. The skull, thought to have been destroyed during World War II, was rediscovered in 1965 (Hoffmann 1997). Unfortunately Weinert's reconstruction was somewhat damaged and several pieces of the face were missing but the existing pieces were reconstituted by H. Ullrich in 1965 (Hesse and Ullrich, 1966). From this time until the early 1990's the specimen was essentially unstudied. In 1992 the authors were requested by the Museum für Vor- und Frühgeschichte in Berlin to describe, analyze, and undertake a reconstruction of the specimen (Thompson and Bilsborough 1994; Thompson and Illerhaus in press).

The Le Moustier 1 skull was briefly described in the early part of this century, but the sample of Neanderthals has increased dramatically since then, as has our understanding of the phylogenetic and functional implications of their morphology, factors which make a new detailed description and analysis of this specimen appropriate. This work is now in progress (Bilsborough and Thompson 1996; Nelson and Thompson in press; Thompson 1995a;Thompson and Bilsborough 1996, 1997; Thompson and Nelson 1997).

The preserved skull of Le Moustier 1 is composed of: the frontal, parietals, temporals and part of the occipital and sphenoid, the mandible, the palate, and most of the permanent dentition (the upper right incisor is missing and the deciduous left incisor is still a part of the tooth row) (Thompson and Bilsborough 1994, 1997). Le Moustier 1 is an adolescent Neanderthal of about 15.5 years of age at death (by human standards of age determination) based upon the developmental status of the dental and postcranial evidence (Thompson 1995 a, b, in press) although it may be younger based on postcranial growth (Nelson and Thompson in press). The specimen is likely a male based on cranial capacity, size of the teeth, diameter of the femur head, and overall robusticity (Thompson 1995b). Despite his youth, Le Moustier 1 possesses a number of traits characteristic of adult Neanderthals, indicating that these were already fully developed by mid-adolescence (Thompson and Bilsborough 1996). These features will be reviewed in this paper.

Neanderthal Features

There are a number of traits commonly found in Neanderthal specimens which may be regarded as characterizing Neanderthal morphology. The purpose of this paper is to examine these in Le Moustier 1 to determine:
1. the presence or absence of such traits in this specimen, so adding to our knowledge of their geographic distribution in the Neanderthal sample;
2. to determine those Neanderthal characters that likely represent the incipiently developed form of the adult condition. Such information will contribute to any assessment of ontogenetic variation and developmental processes in Neanderthals; and
3. to determine features unique to this individual.

Neanderthal features present in Le Moustier 1

Table 1 lists some of the characteristics most commonly used to describe adult Neanderthals and which refers to different regions of the skull and postcranial skeleton: cranial size and shape, the frontal bone and associated features, the temporal, the occipital, the mandible, the maxilla and evidence of midfacial prognathism, and the individual postcranial bones.

Cranial size and shape:The skull of Le Moustier 1 is long, low and platycephalic and with a large cranial capacity of at least 1500cc (Weinert 1925) or even greater if Holloway's (1985) estimate of 1565cc is accepted. The maximum diameter of the skull is low, at the level of the parietal crests and while the upper portion of the vault is an even semi-circle when viewed in norma occipitalis, the lower walls of the brain case are near vertical.

Frontal:The frontal breadth is pronounced, with little post-orbital constriction although the supraorbital torus is separated from the frontal by a shallow sulcus. The frontal sinuses are large and confined to the median section of the browridge and there is a reduced supratoral sulcus above glabella. The outline of the torus indicates that the orbits were probably large and rounded and, based on the preserved portion of the frontal, they are separated by a wide interorbital space, flanked by column-like lateral orbital pillars.

Temporals:The overall proportions of the temporal bones resemble the typical adult pattern with a straight squamous suture which extends posteroinferiorly at a shallow angle. Many adult Neanderthals are characterized by a relatively small mastoid. Those of Le Moustier 1 are small but broad and the mastoid region curves medially. A mastoid tubercle is present on the anterolateral surface of the mastoid, just posterior to the external auditory meatus. Medial to the mastoid, the digastric groove is well developed and, although the relevant bone is missing, the preserved bone indicates that the occipitomastoid crest was present and likely large relative to the mastoid. The external auditory meatus is oval in shape. The mandibular fossa is bounded posteriorly by a short, stout post-glenoid fossa and a tympanic plate that is nearly vertical.

Occipital: Lambdoid flattening occurs on the posterior aspect of the parietals and continues onto the upper scale of the occipital with the Lambda-inion portion of the occipital highly curved. A suprainiac fossa is present above a weak nuchal torus. The nuchal torus projects more posteriorly lateral to the midline and inion is positioned high relative to Frankfurt Horizontal. The superior nuchal line is strongly marked and is situated above a flat nuchal planum. The cranial base appears relatively unflexed baseed on the long, unflexed basioccipital. A small occipital bun is present (contra Wolpoff 1980). The lateral expansion of the occipital seen in many Neanderthals is present but the bun is not well-developed in the sagittal plane. In this feature Le Moustier 1 resembles La Ferrassie 1 and Spy 2, but has a larger bun than the structure seen in Saccopastore 1, for example.

Mandible:The mandibular corpus of Le Moustier 1 is long and relatively robust, meeting the broad ascending ramus at a curved gonial angle. There is no chin present and the corpus is particularly thick in the symphyseal region. The area surrounding the mandibular foramen is damaged, but the horizontal-oval pattern seen in adults is likely present. The teeth of both upper and lower jaws are large and the molars taurodont, and the teeth are relatively unworn. Anteriorly, the dental arcade is flattened in the coronal plane, matching the squared-off appearance of the arcades of adult Neanderthals.

Maxilla & Midfacial Prognathism: Little remains of the maxilla besides some alveolar bone and the dentition. However, enough is present to demonstrate that the zygomatic root is positioned over M2, and that the zygomatic arch was likely quite long with a posteriorly positioned root. This indicates that the face of Le Moustier 1 is characteristically long and relatively prognathic. The anterior teeth are large and relatively unworn, with long roots which indicates that the face of Le Moustier 1 was probably tall in the subnasal region to accommodate the large incisor roots. The incisors are spatulate and shovel-shaped and possess accessory tubercles (Bilsborough and Thompson 1996, in prep). The preserved frontal retains the most superior fragment of the nasal root. Actual measurements are difficult because of the lack of surface bone but the area around nasion is well depressed underneath the supraorbital torus and thus could accommodate the sharply angled nasal bones characteristic of adult Neanderthals. Certainly the nasal root is located posterior to glabella and nasion is positioned anterior to the lateral orbital margins as in adult Neanderthals.

Postcranial skeleton: Published descriptions of the original, and available casts, indicate that even though postcranial growth was not complete, since none of the epiphyses is fused, the Le Moustier 1 specimen was largely adult in its possession of several features characteristic of adult Neanderthals. Since the original postcranial bones are largely destroyed, the following is based upon information in the literature and on detailed examinations of casts. A more detailed description of the postcranial anatomy is in preparation.

The specimen possesses short distal limb segments as demonstrated by the Brachial (78) and Crural (76.3) indices. A cast of a rib fragment is thick and triangular in cross-section, but whether the rib cage was barrel-shaped is unknown. According to Klaatsch (1909c, d), the Le Moustier 1 clavicle is relatively long and slender as seen in adult Neanderthals though a cast indicates that it is missing its epiphyses. The fragment of scapula includes the glenoid fossa, but not enough is preserved to determine whether the scapula had a deep sulcus on its dorsal or ventral surface. Certainly the glenoid fossa appears long and narrow and, according to Klaatsch (1909c), it shows backwards-inflection similar to that seen in the skeleton from Neander Valley. According to the literature, the humerus is robust with a strongly marked deltoid tuberosity. The radius and ulna are short; the radius is strongly curved with a radial tuberosity positioned more medially than in modern humans. Of the original hand bones recovered, none is preserved. Klaatsch remarked (1909a, b) that some of the hand bones were quite small but unfortunately no assessment can be made of the nature of the first carpometacarpal joint, the length of the phalanges, the width of the fingertips, or the strength of the grip (Trinkaus and Villemeur 1991).The size of the femur head indicates that the acetabulum was large but unfortunately only fragments of parts of the innominate bones were preserved.

Klaatsch (1909a, b) describes the diaphyses of the femora as round, curved, not very platymeric proximally, with a faint linea aspera along the posterior surface, and with large lateral condyles but shallow articular cavity. Examination of a cast of the femur shows it to be bowed anteroposteriorly and round in cross-section with no pilaster. The head of the femur is large and the maximum length of the femur was 380 mm (trochanter length 370 mm) (Klaatsch 1909a, b). The femur head-shaft angle, as measured on a cast, is low (113 °). According to Herrmann (1977) the preserved fragments of one of the femora has thick cortical bone and a relatively narrow marrow cavity. A cast of one of the patellae is large and thick. The tibia of Le Moustier 1 was an estimated 290 mm in length; according to Klaatsch (1909a, b) it was not platymeric but there was probably retroflexion of the proximal surfaces. Fragments of the diaphyses of the fibulae were recovered in 1908 but did not survive the fire of 1945. They were described by Klaatsch (1909a, b) as being thick, but without the curvature seen in anatomically modern humans. None of the foot and ankle bones of Le Moustier 1 survived the fire and they do not seem to have been described by Klaatsch. Although the missing distal and proximal epiphyses have been reconstructed, a cast of the left 1st metatarsal reveals that this bone was strong and robust indicative of the adult Neanderthal condition.

Features reflecting the youth of Le Moustier 1

Despite this extensive list of features found in many, if not all adult Neanderthals, there are several others that are absent or only incipiently developed. Many of these are likely to reflect the specimen's youth; others appear to be unique to Le Moustier 1 and will be outlined below. Discussion of the adult morphology represented by this specimen necessarily involves assumptions about the pattern and magnitude of growth remaining. We now summarize our view on the likely outcome of further cranial growth had the individual lived to full maturity.

A number of traits probably reflect the specimen's immaturity and include: the lack of a retromolar space; the preserved coronoid process projects anteriorly instead of posteriorly as in adults; and the mental foramen lie under P3 and P4 rather than under M1. Assuming that Neanderthals follow a growth pattern similar to that of modern humans, we assume that the jaws would have growth in length to accommodate the eruption of the M3's just as they do in modern human adolescents during puberty (Minugh-Purvis 1988). It is probable that the position of the mental foramen and the angle of projection of the coronoid process would be affected by such an increase in mandibular length.

The specimen departs from the adult pattern in other ways. The supraorbital torus lacks the characteristic thick, double-arched shape seen in adult specimens, although traces of it are evident, and it thins laterally instead of maintaining a continuous bar of bone above the orbits. The frontal bone is more steeply angled than seen in adult Neanderthals and the vault bones are not particularly thick. Also, the nasal aperture, as estimated by Weinert (1925) was rather small compared to those of adult Neanderthals. It is likely that the morphology and/or size of the torus, the frontal, and the nasal aperture would have been affected by any anterior growth of the face resulting from any lengthening of the upper and lower jaws and/or widening of the face.

In the temporal region, including the temporomandibular joint (TMJ) and the external auditory meatus (EAM), Le Moustier 1 also departs from the adult pattern. The anterior aspect of the mandibular fossa is bounded by a steep ridge of bone which extends medially from each articular eminence rather than forming a flat pre-glenoid plane as seen in many adults; the tympanic plates are more vertically inclined than in many adults; and the EAM is positioned behind, instead of slightly above, the mandibular fossa and below, instead of in the same plane as, the root of the zygomatic process.

The morphology of the articular surfaces of the TMJ can change due to masticatory stresses. Trinkaus (1988) suggests that the adult Neanderthal TMJ morphology may be be linked to the pronounced dental wear seen in these specimens. Since the teeth of Le Moustier 1 are relatively unworn compared to adults, his TMJ morphology may reflect an earlier stage of this remodelling process. Similar growth remodelling may explain the position of the EAM in this specimen.

Unique Features of Le Moustier 1

Finally, there are a few traits that are unique to Le Moustier 1. The adult "en bombe" shape, usually apparent in posterior profile, is not present in Le Moustier 1. However, this might well be the result of how the cranial fragments were reconstructed. The lower left adult canine is impacted in the jaw and the left mandibular condyle is affected by pathology. Another anomaly is that the left and right mandibular fossae differ somewhat in their morphology, mainly in the area of the entoglenoid process. On the right side of the cranial base, the entoglenoid process is distinct and there appears to be a small gap medially, between it and the tympanic plate. On the left side, there is no such gap present and the left entoglenoid process is not as well-developed. The significance of this is unclear; the contrasts may represent plastic deformation resulting from taphonomic forces incurred during fossilization or may be in some way connected to the pathology noted above. The pathological condyle, the asymmetry in the mandibular fossae, coupled with the asymmetrical wear which is present on the molar teeth, may well be connected and future study may reveal the reason for these morphological anomalies.

Discussion and Conclusions

As mentioned before, if this individual survived to full maturity, his jaws would have exhibited additional anterior growth , thus affecting the extent of facial prognathism. Additional, functionally correlated changes include: a more pronounced supraorbital torus; a less steep frontal bone; thicker cranial bones; and remodelling of the TMJ and EAM. If these phenomena can be generalized to all adolescent Neanderthals, it would seem that substantial changes to their cranial morphology occurred during the later part of the adolescent growth period.

Apart from these indications of immaturity, the skull and postcrania possesses many of the traits diagnostic of adult Neanderthals. This mixture of adult and immature characteristics makes the Le Moustier 1 specimen extremely important for Neanderthal studies. For instance, despite his immaturity, Le Moustier 1 still possesses the majority of traits found in many adult Neanderthals, and so contributes to our knowledge of the geographic variability of these traits. Secondly, the comparatively late date of the specimen means that it is one of the last known Neanderthals. Despite this, it possesses no features that could be called "transitional" in a phylogenetic sense, which supports the growing body of evidence that typical Neanderthal morphology persisted, in at least some individuals, until 40kya and later. This lack of "transitional" features in Le Moustier 1 would lend support to theories that suggest that Neanderthals had little or no genetic role to play in the origin of modern humans (e.g. Stringer and Gamble 1993). Thirdly, its immature status allows an important ontogenetic gap to be filled. Remains of adolescent Neanderthals are rare. Even though we lack the complete original elements of the Le Moustier 1 postcrania, casts and the available descriptions in the literature will allow some comparisons to be made between this and other specimens of similar developmental age and so expand our knowledge of the adolescent period of Neanderthals (Thompson in press; Nelson and Thompson in press; Thompson and Nelson 1997).

The Le Moustier 1 specimen has had a long and interesting history. Though damaged and abraded, the skull is relatively complete and this, and the postcrania, possess diagnostic morphology which make them significant evidence for Neanderthal research. These and other aspects of the Le Moustier 1 specimen will be considered in more detail in future papers.

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