A Closer Look at Neanderthal Postcanine Dental Morphology: The Mandibular Dentition

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1 THE ANATOMICAL RECORD (NEW ANAT.) 269: , 2002 ARTICLE A Closer Look at Neanderthal Postcanine Dental Morphology: The Mandibular Dentition SHARA E. BAILEY* Neanderthals are known to exhibit unique incisor morphology as well as enlarged pulp chambers in postcanine teeth (taurodontism). Recent studies suggest that their overall dental pattern (i.e., in morphologic trait frequencies) is also unique. However, what this means in a phylogenetic sense is not known. Although exploring the polarity of dental morphologic characters is essential to understanding the phylogenetic implications of unique patterns of variation, few have undertaken this task. This study moves beyond standard scoring methods, which are based on modern humans, to include several postcanine traits that have not been considered previously. In addition, Homo erectus is used as an outgroup to Neanderthals and modern humans to explore the polarity of these traits. The findings of this study suggest that Neanderthals are not only unique in their pattern of dental trait frequencies (as found in previous studies) but that they present several dental autapomorphies, as well. These include a high frequency of the mid-trigonid crest in lower molars and unique morphology of the lower premolars. Interestingly, these characters are not observed in the Mauer mandible, which some have claimed to be a member of a chronospecies that is a unique ancestor to Neanderthals. Anat Rec (New Anat) 269: , Wiley-Liss, Inc. KEY WORDS: comparative anatomy; dental morphology; human evolution; hominoid postcanine teeth; Neanderthals; Homo sapiens; Homo heidelbergensis; Homo erectus INTRODUCTION Neanderthals are a group of extinct humans that inhabited Europe and Western Asia between approximately 200,000 and 30,000 years ago. They are also the best-known and most extensively studied extinct human group. Despite the totality of morphologic and cultural evidence in support of the theory that Neanderthals are a distinct group of archaic humans (Tattersall and Schwartz, 2000), paleoanthropologists continue to debate the biological specializations that help define their clade. This debate Ms. Bailey is a paleoanthropologist completing her doctorate at Arizona State University. She specializes in dental anthropology and is in the process of developing new standards for scoring variation in fossil hominids. Currently her interest lies in using dental morphology to investigate evolutionary patterns in the fossil record and to address issues regarding the origin of modern humans. *Correspondence to: Shara E. Bailey, American Museum of Natural History, Division of Anthropology, Central Park West at 79th Street, New York, NY Fax: ; shara.bailey@asu.edu DOI /ar Published online in Wiley InterScience ( concerns the origins of modern humans and the nature and degree to which Neanderthals participated in our evolution (Box 1). Traditionally, researchers have focused on cranial (and to a lesser extent postcranial) features to address the question of evolutionary relationships among Neanderthals and modern humans. However, this kind of research has been confounded by a lack of agreement regarding how morphologic characters should be interpreted, that is, whether they are primitive or derived (in a cladistic sense). This disagreement may be due, at least in part, to the nature of working with skeletal features that can be affected more by a variety of external influences such as diet and behavior. Teeth are good anatomical candidates for making phylogenetic inferences for several reasons, not the least of which is because they are the most abundantly preserved elements in the fossil record. In addition, teeth contain a large array of morphologic information that is controlled to a greater extent by genes than are skeletal features. Once formed, crown morphology does not change, except through tooth wear. Dental morphologic studies have shown that different geographic populations e.g., Asia, Europe, Africa, and India can be characterized by regional dental morphologic patterns (Hanihara, 1969; Mayhall et al., 1982; Turner, 1990a; Irish, 1994; Hawkey, 1998). Studies also show that variation in dental morphologic characters can be successfully used to work out biological affinities among human populations (Sofaer et al., 1986; Hanihara, 1989; Irish and Turner, 1990; Turner, 1990b Lipschultz, 1997; Bailey et al., 1998; Hawkey, 1998). Because teeth preserve extremely well over long periods of time, the same approach can be easily applied to both present and past populations. NEANDERTHAL DENTAL MORPHOLOGY Neanderthals are known to have had large anterior teeth marked by strong shoveling, marked labial convexity, and prominent lingual tubercles, as well as postcanine teeth with enlarged pulp chambers (taurodontism) (Figure 1). Beyond this, it is generally assumed that Neanderthal postcanine tooth morphology is just like that in modern humans (e.g., Smith, 1976) Wiley-Liss, Inc.

2 ARTICLE THE ANATOMICAL RECORD (NEW ANAT.) 149 BOX 1. THE MODERN HUMAN ORIGINS DEBATE For the past two decades Neanderthals have been interpreted in terms of one of two competing models for modern human origins (see Figure). Supporters of the Recent African Origin model (a) posit that Neanderthals were replaced by emigrating African modern humans and contributed little or nothing to the modern human gene pool (e.g., Stringer, 1992; Stringer and Bräuer, 1994). Supporters of Multiregional Evolution (b) believe Neanderthals may have played a significant role in modern human origins (even if they stress that the role of Neanderthals is not central to their model) (Frayer et al., 1993; Wolpoff et al., 1984). Where proponents of these models disagree most is in deciding whether or not Neanderthals were too different from modern humans to have played a significant role in their evolution. Intermediate models have been proposed but prove difficult to test with the fossil record. Note: dotted lines indicate gene flow between ancient populations. Figure. Two competing models for modern human origins: Recent African origin model (a) and multiregional evolution (b). (Modified from Stringer and Gamble, 1993). However, recent studies indicate that this may not be the case. The Arizona State University Dental Anthropology System, or ASUDAS, is a standardized system for recording variation in the tooth crowns and roots of modern humans (Box 2). Several studies within the past 5 years have shown that the system can be applied effectively to fossil hominids as well (Stringer et al., 1997; Irish, 1998; Tyrell and Chamberlain, 1998; Bailey and Turner, 1999; Bailey, 2000b; Coppa et al., 2001). Results from these studies suggest that the differences between Neanderthals and modern humans go beyond those observed on the incisors and postcanine roots (at least in trait frequencies). For example, when the frequencies of 10 morphologic traits in Neanderthals were compared with ranges observed in large groups of geographically diverse contemporary modern humans, the frequencies for five traits fell within the modern human range, whereas the frequencies for the other five fell outside the modern human range (Figure 2) (Bailey, 2000a). Based on all the dental evidence that has been analyzed thus far, the Neanderthal dental pattern can be described in terms of low and high frequency ASUDAS traits (Table 1). It is now clear that relative to modern humans, Neanderthals exhibit a unique dental morphologic pattern. Teeth contain a large array of morphologic information that is controlled to a greater extent by genes than are skeletal features. However, to date, no study has systematically explored what this uniqueness means in an evolutionary sense. We do not know, for example, whether or not the Neanderthal dental pattern is a primitive one or even whether or not there are yet-to-be-described dental morphologic characters that are uniquely derived in (autapomorphic for) Neanderthals. This is likely due to the fact that ASUDAS is based on modern human variation and was developed for the purpose of deciphering population relationships, not evolutionary ones. Therefore, when applied to fossil hominids, this system is biased in that only those characters in fossil hominids that are present and variable in modern humans are evaluated. Characters that are present but invariable or absent in modern humans are not included in the system, as they would not be useful for the purpose for which it was designed. On the basis of descriptive studies of Mid to Late Pleistocene hominid teeth (Patte, 1959; Genet-Varcin, 1962, 1966, 1972; Smith, 1976; Trinkaus, 1978; Tillier, 1979, 1991; Tillier et al., 1989), there is reason to believe that the Neanderthal dentition differs from that of modern humans in more than trait frequencies and includes dental traits that are not currently part of the ASUDAS. Unfortunately, characterization and quantification of

3 150 THE ANATOMICAL RECORD (NEW ANAT.) ARTICLE Figure 1. Marked shoveling (1), labial convexity (2), and lingual tubercles (3) on maxillary incisors (a) and taurodontism (arrow) of mandibular molars (b) have been the primary focus of dental morphologic research on Neanderthals. (Photo (a) by E. Trinkaus.) these traits and their variation have generally been lacking. One of the goals of my research is to correct this problem, in part, by developing a supplemental scoring system for fossil hominids. The purpose of this particular study is to describe and define the variation in some mandibular postcanine tooth crown traits that are not part of the ASUDAS and to draw attention to the fact that these variations (and others) appear to have phylogenetic significance. Of primary concern is determining whether significant differences exist between Neanderthals and modern humans. The results presented here are part of an ongoing study of Neanderthal postcanine dentition. In the interest of space, only the mandibular dentition is discussed; the maxillary dentition will be discussed in a subsequent study. THE STUDY The Neanderthals used in this study include specimens from both Europe and Western Asia. Previous studies have shown that, although some geographic variation exists between these samples, they always form a group separate from modern humans (Bailey and Turner, 1999; Bailey, 2000a). The modern human sample includes early modern humans, Upper Paleolithic modern humans, and contemporary modern humans from six geographic regions (see Table 2). To ascertain the polarity of these traits, a small outgroup sample (Homo erectus) is included in the analyses. Finally, comparisons are made with a small sample of teeth from Arago and Mauer, which are European Middle Pleistocene hominids sometimes attributed to the species Homo heidelbergensis. The samples in which the postcanine teeth could be adequately scored are presented in Table 2. The individual count method used in this study involves scoring both right and left sides of the dentition but only by using the antimere with the highest trait expression in the analysis (Scott and Turner, 1988). This strategy results in smaller sample sizes but avoids biasing the results toward individuals with both antimeres present. For the most part, specimens were included if they exhibited only minimal to moderate wear (fissure pattern visible and cusp tips only moderately worn). However, for some traits (e.g., P 4 transverse crest, see below), assessment of trait s presence could be ascertained even when the tooth was quite worn. The premolar traits used in the analysis include lingual cusp number, transverse crest, lingual crown contour, and metaconid position (Figure 3). Of these, only lingual cusp number is part of the ASUDAS. The other traits were chosen because of their apparent low variation of expression in modern human populations (Kraus and Furr, 1953; Ludwig, 1957; Biggerstaff, 1969) and because previous research suggested to me that they may have evolutionary (phylogenetic) significance. No reference plaques have yet been developed to represent expression of these new traits. BOX 2. THE ARIZONA STATE UNIVERSITY DENTAL ANTHROPOLOGY SYSTEM The Arizona State University Dental Anthropology System (ASUDAS) is becoming the worldwide standard for morphologic study. It currently consists of more than 28 morphologic traits of proven utility for population comparisons. Traits are scored by using a combination of plaques (see figure) and written descriptions of the variation (Turner et al., 1991). Although many more traits are present on teeth than are included in the ASUDAS (see Morris, 1965), those that are used were chosen because they are relatively easy to score, remain even after moderate wear, and have proven useful in characterizing intra- and interpopulation variability and relationships. Figure. A sample scoring plaque from the ASUDAS (canine distal acessory ridge).

4 ARTICLE THE ANATOMICAL RECORD (NEW ANAT.) 151 Figure 2. Bar graphs illustrating how frequencies of Arizona State University Dental Anthropology System traits found in Neanderthals compare with those observed in recent human populations. Of the 10 traits for which comparisons were possible, 5 fall within the observed ranges of variation in recent humans (a) and 5 fall outside the observed ranges of variation in recent humans (b). Groups exhibiting high frequencies of traits are shown in black and those exhibiting low frequencies are shown in grey. Note that the Neanderthal dental pattern does not correspond to that of any living modern humans. SS, sub-saharan; W, western, N, north. All modern human data are taken from Scott and Turner (1997). The mid-trigonid crest (MTC) is the only mandibular molar trait reported in this study. The MTC is an enamel bridge that joins the protoconid and metaconid (Figure 4). This trait was chosen because of its apparent low frequency in modern humans (Wu and Turner, 1993) and high frequency in Neanderthals (Zubov, 1992). It is currently part of the ASUDAS, but the scoring procedure used here differs from the one described in Turner et al. (1991). Table 3 presents the trait descriptions, scoring procedures, and the presence/absence breakpoints used in this analysis. NEANDERTHAL POSTCANINE DENTAL MORPHOLOGY After examining 26 Neanderthals P 4 s, a distinct configuration emerged one that is marked by a complex occlusal surface topography and an asymmetrical lingual contour. The tooth s complex topography results from a combination of a strong and continuous transverse crest, a high and well-developed metaconid, and extra fissures, ridges, and lingual cusps (Figure 5a). The modern human sample consisted of 125 P 4 s. In contrast to a typical Neanderthal P 4, modern human P 4 s, more often than not, exhibit a greatly simplified occlusal morphology. Although multiple lingual cusps are not uncommon in modern populations, P 4 s of both contemporary and fossil modern humans typically lack a well-developed continuous transverse crest, as well as other accessory ridges and fissures. Moreover, modern human P 4 s almost invariably exhibit a symmetrical lingual crown contour. One of the most notable features of the modern human P 4 s is the occurrence of a metaconid that is so reduced that it forms only a lingual shelf or is lacking altogether (Figure 5d). This condition was never observed in the Neanderthal sample. Figure 6 illustrates how the traits mentioned above are distributed among Neanderthals and modern human populations. As suspected, Neanderthals exhibit the highest frequencies for multiple lingual cusps (93%), transverse crest (88%), and asymmetrical lingual crown contour (96%). Although multiple lingual cusps are also found in moderate to high frequencies in modern groups (50 80%), the other two traits occur in much lower frequencies (0 6% in recent groups and 18% in the Upper Paleolithic group). The presence of a transverse crest is more frequent in the early modern human sample (50%) than it is in other modern human samples; however, a sample size of two individuals requires cautious interpretation. Frequencies for metaconid placement are presented in Figure 6 to illustrate that a mesi- TABLE 1. High and low frequency dental morphological traits* found in Neanderthals High frequency traits Low frequency traits Incisor shoveling Incisor double shoveling Incisor labial convexity Four cusped M 2 Incisor lingual tubercles Three cusped M 2 Cusp 5 M 1 M 1 enamel extension Y-groove pattern M 2 Canine mesial ridge Carabelli s cusp M 1 Presence of M 3 *Based on the Arizona State University Dental Anthropology System (Turner et al., 1991).

5 152 THE ANATOMICAL RECORD (NEW ANAT.) ARTICLE TABLE 2. List of samples and teeth used in this study Neanderthals Europe P 4 only M 1or2 only Western Asia P 4 only M 1or2 only Early modern humans only Upper Paleolithic modern humans P 4 only M 1or2 only Contemporary modern humans Africa Europe North Asia West Asia India Australasia Homo erectus Asia: Africa: M 1or2 only Homo heidelbergensis ally placed metaconid (quite common in modern humans) is not necessarily associated with an asymmetrical tooth crown (rare in modern humans). Further analysis reveals that, although traits that contribute to the unique Neanderthal P 4 morphology (such as a continuous transverse crest, a large metaconid, and an asymmetrical lingual crown contour) may be present in modern populations, the combination of all three traits in an individual is not. In fact, only 2.4% of the modern humans exhibited even two of the traits in combination. In marked contrast, 35% of Neanderthals exhibited two traits and 59% exhibited all three traits in combination (Figure 7). As is true of the P 4 s, Neanderthal mandibular molars also tend to possess extra occlusal fissures and crests. This Pontnewydd, Hortus, Petit Puymoyen, Le Moustier, Krapina Monsempron Montmaurin, Ehringsdorf, La Quina, La Ferrassie, Gibraltar, Grotta Brueii Kebara, Amud, Shanidar Tabun Qafzeh, Skhul Le Rois, St. Germaine-la-Rivière, Dolni Vestonice, Gough s Cave, Oberkassel Brno Fourneau du Diable Fontéchevade, Isturits, Vachons, Abeilles, La Ferrassie, Mieslingtal, Fontana Ranuccio, Madeleine, Greze North Africa British Neolithic, Hungary, Germany, Austria, Yugoslavia, Bulgaria, Greece, Crete Japan, China, Korea Tel Hesi, Jericho India Australia, New Guinea Zhoukoudian, Sangiran KNM-ER, KNM-WT, Olduvai, Tighenif Sidi Abderrahman Arago, Mauer Figure 3. Premolar crown characters referred to in the text: transverse crest (a), metaconid (b), lingual contour (c), and lingual cusps (d). The symbol indicates orientation of the tooth: B, buccal or cheek side of the tooth; L, lingual or tongue side; M, mesial or toward the front of the mouth; and D, distal or toward the back of the mouth. observation is not remarkable in and of itself, as occlusally complex molars typify most fossil hominids and are found with some frequency among modern humans as well. The most remarkable feature observed on Neanderthal mandibular molars is its wide and deep anterior fovea bordered mesially by a low mesial margin and distally by a continuous MTC (Figure 8a). In contrast, modern human mandibular molars typically lack a bridge between these cusps. Although the crests of C1 and C2 may be well developed, they generally do not join to form a continuous ridge (see Figure 8). In this case, the cusps are separated by the sagittal sulcus, which either terminates in the anterior fovea (b) or runs the length of the tooth (c). Most often the crests are not very well developed. The frequencies for the MTC are given in Figure 9. It is clear that Neanderthals show the highest frequencies for this trait (90 100%). Notable as well is that, in modern humans, the MTC is even less frequently observed in M 2 and M 3, but in Neanderthals the frequencies are relatively constant in all three molars. To determine whether these characters are primitive retentions or derived features, high definition casts of 7 P 4 s, 9 M 1 s, and 7 M 2 s from East African and Asian Homo erectus were examined. Superficially, Homo erectus P 4 s resemble Neanderthal P 4 s in size and morphologic complexity. However, they lack the unique Neanderthal morphol- Figure 4. Molar crown characters referred to in the text: protoconid (a); metaconid (b); anterior fovea (c); mid-trigonid crest (d). Symbol orientations as in Figure 3.

6 ARTICLE THE ANATOMICAL RECORD (NEW ANAT.) 153 TABLE 3. Scoring procedure and presence/absence breakpoints for traits used in this study Trait Definition and scoring procedure Presence/absent breakpoint Transverse crest (P 4 ) Presence of a crest or ridge connecting the Presence Grades 2 3 buccal and lingual cusps 0 absent; 1 weak expression or interrupted crest; 2 moderate expression; 3 marked expression Metaconid position (P 4 ) Position of the metaconid relative to the Presence mesial position of the protoconid apex. Scored as mesial, central or distal. Lingual crown contour (P 4 ) Shape of the lingual contour of the tooth Presence asymmetrical when viewed occlusally. Scored a symmetrical or asymmetrical Mid-trigonid crest (M 123 ) An enamel ridge that connects the Presence Grade 2 protoconid (Cusp 1) and metaconid (Cusp 2). 0 absent; 1 crests are well developed but do not form a bridge; 2 crests form a complete bridge ogy described above. Instead, they exhibit a symmetrical (almost square) lingual contour and the transverse crest is either completely lacking or is divided by the longitudinal fissure (Figure 5b). In this way, they resemble the modern human P 4 more than the Neanderthal P 4. The mandibular molars of Homo erectus are morphologically complex, and the crests of C1 and C2 are often well developed. However, the MTC so frequent in Neanderthals is rare or absent in this sample (Figure 8b): only 1 of the 14 teeth examined exhibited a bridge-like crest. Table 4 summarizes the characters and character states discussed above. Although some variation in each group exists, certain character states can be said to typify a particular group. A comparison of these states among the sample groups indicates that (assuming Homo erectus presents the primitive conditions) the Neanderthal dental pattern is the result of derived dental morphology rather than primitive retentions. It also indicates that, relative to the derived conditions observed in Neanderthals, modern humans retain the primitive condition for several of these morphologic features. The samples Arago and Mauer were also included in this study to investigate whether dental morphology would support the claim that they, as members of the species Homo heidelbergensis, should be considered a chronospecies that gave rise exclusively to Neanderthals (Rosas and Bermúdez de Castro, 1998). Although the sample size is small (3 P 4 ;3M 1 ;5 M 2 ;and2m 3 ) and this investigation is based on only a few morphologic characters, some general observations can be made. All P 4 s resemble those of Homo erectus and Neanderthals in Figure 5. A comparison of mandibular second premolars. The Neanderthal P 4 (a) presents an asymmetrical lingual contour, marked transverse crest, a mesially placed metaconid and extra lingual cusps. The Homo erectus (b) and modern human P 4 s(c,d) all have symmetrical lingual contours and lack a prominent transverse crest. The marked metaconid reduction and shelf-like morphology seen in d is common in recent modern human P 4 s. but not found in Neanderthals or in Homo erectus. a, Krapina; b, Zhoukoudian; c, Dolni Vestonice; d, recent Australian. Symbol orientation as in Figure 3.

7 154 THE ANATOMICAL RECORD (NEW ANAT.) ARTICLE Figure 6. A comparison of P 4 trait frequencies among samples. Neanderthals show the highest frequencies of multiple lingual cusps (MLC), presence of a well-developed continuous transverse crest (TRCRST), and lingual crown asymmetry (ASYM mesial). Lingual contour asymmetry does not appear to be directly related to the position of the metaconid. METPOS, mesial; UP, Upper Paleolithic; NE, North East; W., West. exhibits a strong MTC, as do two of the four M 2 s (Figure 11b), whereas the single scorable M 3 does not exhibit an MTC. In sum, certain teeth in the Arago sample possess traits that occur in uniquely high frequencies in Neanderthals. This evidence could be used as tentative support for the hypothesis that they are members of a group that gave rise exclusively to Neanderthals (Rosas and Bermúdez de Castro, 1998). It would be more difficult to make this case based on the Mauer mandible alone, as it does not show any particular affinity to Neanderthals based on its tooth crown morphology. It is important to keep in mind, however, that the dental characteristics discussed here comprise only a small portion of the entire set of dental traits available for analysis. My on-going research will take into consideration all dental traits in order to better test the dental affinity of the Middle Pleistocene hominids. Figure 7. The frequency at which a transverse crest, a well-developed metaconid, and lingual crown asymmetry occurs in combination in modern humans and Neanderthals. See text for explanation. their size and morphologic complexity. The Mauer and Arago 13 P 4 s are quite similar to each other and overall resemble Homo erectus P 4 s: both exhibit symmetrical lingual contours and lack a continuous transverse crest (Figure 10a,b). The Arago 28 P 4, however, exhibits a mixed morphology: it possesses a mesially placed metaconid together with a strong transverse crest but a symmetrical lingual contour (Figure 10c). As was the case for the P 4, the Mauer molars also resemble the Homo erectus condition: completely lacking a MTC (Figure 11a). The Arago molars are variable (as were the P 4 s). One of the two M 1 s CONCLUSIONS Neanderthal premolars and molars have received less attention than their incisors owing to the assumption that Neanderthal postcanine dental morphology is much like our own. Recent research, however, has shown this not to be the case, as Neanderthals exhibit a unique pattern of dental morphologic trait frequencies (Stringer et al., 1997; Irish, 1998; Bailey, 2000a; Coppa et al., 2001). The results of this particular study corroborate earlier ones by providing evidence for some newly described dental morphologic traits that are rare-to-absent in modern humans. In particular, the mandibular P 4 s present a unique combination Figure 9. A comparison of mid-trigonid crest frequencies among sample groups. Neanderthals show the highest frequencies for all three molars (M1 3). UP, Upper Paleolithic; NE, North East; W., West.

8 ARTICLE THE ANATOMICAL RECORD (NEW ANAT.) 155 Figure 8. A comparison of mandibular molars. Arrows point to the mid-trigonid crest (a) or the sagittal sulcus (b,c). A, Grotta Brueil, Neanderthal [flipped]; b, KNM-WT 15000, Homo erectus; c, Abeille, Upper Paleolithic Homo sapiens. Symbol orientation as in Figure 3. TABLE 4. Characters and character state distribution Character H. erectus Neanderthal H. sapiens P 4 Lingual crown outline Symmetrical Asymmetrical Symmetrical P 4 Transverse crest Absent/divided Present Absent Frequency of a welldeveloped Frequent Frequent Infrequent P 4 metaconid Mid-trigonid crest (M 1 ) Absent/divided Continuous Absent/divided Mid-trigonid crest (M 2 ) Absent Continuous Absent Figure 10. A comparison of Homo heidelbergensis P 4 s. All resemble Homo erectus in their symmetrical lingual crown contour and complex occlusal topography. The continuous transverse crest present in Arago 28 (c) is a typical Neanderthal character. It is absent in both Mauer (a) and Arago 13 (b). See text for explanation. Symbol orientation as in Figure 3. Figure 11. A comparison of the Mauer M 1 (a) and an M 2 from Arago (b: flipped). Both exhibit a complex tooth crown, but Mauer lacks a mid-trigonid crest (a typical Neanderthal character), and in Arago, it is present. See text for explanation. Symbol orientation as in Figure 3. of dental characters that was neither observed in modern humans nor in the Homo erectus outgroup. This finding suggests that the characters are not primitive retentions but are instead Neanderthal dental autapomorphies. The preponderance of evidence thus far suggests that, relative to modern humans and regardless of geological age or geography, Neanderthals are uniquely derived in their dental morphology. Not surprisingly, this finding also holds true when Neanderthals are compared with a hypothetical dental ancestor of modern humans (Stringer et al., 1997). However, that Neanderthals exhibit a unique dental morphologic pattern may not be particularly surprising, given that distinct dental patterns are found in contemporary modern humans of different geographic origins (Hanihara, The preponderance of evidence thus far suggests that, relative to modern humans, regardless of geologic age or geography, Neanderthals are uniquely derived in their dental morphology. 1969; Mayhall et al., 1982; Turner, 1983; Irish, 1994; Hawkey, 1998). What is interesting is that modern human dental patterns appear to have great antiquity. For example, contemporary Europeans link closely with Upper Paleolithic modern humans, and contemporary Africans link closely with Late Pleistocene Africans (Bailey, 2000a). Yet, the Neanderthal dental pattern has no modern representatives and, instead, seems to disappear with its possessors. In addition, incipient Neanderthal dental traits can, however, be found among earlier archaic Homo sapiens (specifically Arago this study), suggesting that the Neanderthal dental pattern may have been evolving separately from modern humans for a long time. Moreover, neither the unique Neanderthal dental pat-

9 156 THE ANATOMICAL RECORD (NEW ANAT.) ARTICLE tern (in trait frequencies) nor the morphology described herein has been found in Upper Paleolithic modern humans, as may be expected if the two groups were interbreeding for a substantial length of time. ACKNOWLEDGMENTS Thanks to Bill Kimbel, Don Johanson, and Ken Mowbray and the anonymous reviewer for their helpful comments on the manuscript and to all the curators who provided access to the many fossils included in this study. This research was made possible by funding from the LSB Leakey Foundation and National Science Foundation (Award No. BCS ). LITERATURE CITED Bailey SE. 2000a. Dental morphological affinities among late Pleistocene and recent humans. Dent Anthropol 14:1 8. Bailey SE. 2000b. Implications of dental morphology for population affinity among Late Pleistocene and recent humans (abstract). J Hum Evol 38:A5 A6. Bailey SE, Turner CG Jr A new look at some old teeth: an analysis of nonmetric dental traits in Neandertals and Old World modern humans (abstract). Am J Phys Anthropol 27:87. Bailey SE, Turner CG Jr, du Souich P Dental morphological evidence for population affinities of the Iberian Peninsula (100 BC 1300 AD) and Western Balearic Islands (abstract). Am J Phys Anthropol 25:65. Biggerstaff R The basal area of posterior tooth crown components: the assessment of within tooth variations of premolars and molars. Am J Phys Anthropol 31: Coppa A, Dicintip F, Vargiu R, Lucci M, Cucina A Morphological dental traits to reconstruct phenetic relationships between Late Pleistocene-Ancient Holocene human groups from Eurasia and North Africa (abstract). Am J Phys Anthropol 32:54. Frayer D, Wolpoff M, Thorne A, Smith F, Pope G Theories of modern human origins: the paleontological test. Am Anthropol 95: Genet-Varcin E Évolution de la couronne de la seconde prémolaire inférieure chez les hominidés. Ann Paléontol 48: Genet-Varcin E Étude des dents permanentes provenant du gisement moustérien de la crose de Dua. Ann Paléontol (Vertébrés) 52: Genet-Varcin E Étude de molaires inférieures humaines découvertes dans le gisement du Placard (Charente). Ann Paléontol 58: Hanihara K Mongoloid dental complex in the permanent dentition: proceedings of the VIIIth International Congress of Anthropological and Ethnological Sciences, Tokyo and Kyoto, Tokyo: Science Council of Japan. p Hanihara T Affinities of the Philippine Negritos as viewed from dental characters: a preliminary report. J Anthropol Soc Jpn 97: Hawkey D Out of Asia: dental evidence for affinities and microevolution of early populations from India/Sri Lanka. PhD thesis, Arizona State University, Tempe, Arizona. Irish J The African dental complex: diagnostic morphological variants of modern sub-saharan populations (abstract). Am J Phys Anthropol 18:112. Irish J Ancestral dental traits in recent sub-saharan Africans and the origins of modern humans. J Hum Evol 34: Irish JD, Turner CG, II West African dental affinity of Late Pleistocene Nubians: peopling of the Eurafrican-South Asian triangle II. Homo 41: Kraus B, Furr M Lower first premolars. I: A definition and classification of discrete morphologic traits. J Dent Res 32: Lipschultz JG Who were the Natufians? A dental assessment of their population affinities. Master s thesis, Arizona State University, Tempe, Arizona. Ludwig F The mandibular second premolars: morphologic variation and inheritance. J Dent Res 36: Mayhall J, Saunders S, Belier P The dental morphology of North American Whites: a reappraisal. In: Kurten B, editor. Teeth: form, function, and evolution. New York: Columbia University Press. p Morris D The anthropological utility of dental morphology. PhD thesis. University of Arizona, Tucson, Arizona. Patte E La dentition des Néandertaliens. Ann Paléontol 45. Rosas A, Bermúdez de Castro J The Mauer mandible and the evolutionary significance of Homo heidelbergensis. Geobios 31: Scott GR, Turner CG II Dental anthropology. Annual Review of Anthropology 17: Scott GR, Turner CG II The Anthropology of Modern Human Teeth. Dental Morphology and its Variation in Recent Human Populations. Cambridge: Cambridge University Press. Smith F The Neandertal remains from Krapina. Department of Anthropology, University of Tennessee. Rep. Invest. 15: Sofaer J, Smith P, Kaye E Affinities between contemporary and skeletal Jewish and non-jewish groups based on tooth morphology. Am J Phys Anthropol 70: Stringer C Replacement, continuity, and the origin of Homo sapiens. In: Bräuer G, Smith F, editors. Continuity or replacement? Controversies in Homo sapiens evolution. Rotterdam: Balkema. p Stringer CB, Gamble C In search of Neanderthals: solving the puzzle of human origins. London: Thames and Hudson. Stringer C, Bräuer G Methods, misreading and bias. Am Anthropol 96: Stringer C, Humphrey L, Compton T Cladistic analysis of dental traits in recent humans using a fossil outgroup. J Hum Evol 32: Tattersall I, Schwartz J Extinct humans. New York: Nevraumont Publishing Co. Tillier A-m Le dentition de l enfant moustérien Châteauneuf 2 découverte a l Abri de Hauteroche. L Anthropologie 83: Tillier A-m Le mandible et les dents: Le Squelette Moustérian de Kebara 2. Paris: CNRS. Tillier A-m, Arensburg B, Duday H La mandibule et les dents du neandertalien de Kebara (Homo 2) Mont Carmel, Israel. Paleorient 15: Trinkaus E Dental remains from the Shanidar adult Neanderthals. J Hum Evol 7: Turner CG II Sinodonty and Sundadonty: a dental anthropological view of Mongoloid microevolution, origin, and dispersal into the Pacific basin, Siberia, and the Americas. In: Vasilievsky R, editor. Late Pleistocene and Early Holocene cultural connections of Asia and America. Novosibirsk: USR Academy of Science Siberian Branch. p Turner CG II. 1990a. Major features of Sundadonty and Sinodonty, including suggestions about East Asian microevolution, population history, and late Pleistocene relationships with Australian Aboriginals. Am J Phys Anthropol 82: Turner CG II. 1990b. Origin and affinity of the prehistoric people of Guam: a dental anthropological assessment. In: Hunter- Anderson R, editor. Recent advances in Micronesian Archaeology, Micronesia supplement No. 2. Mangilao: University of Guam Press. Turner CG II, Nichol CR, Scott GR Scoring procedures for key morphological traits of the permanent dentition: The Arizona State University Dental Anthropology System. In: Kelley MA, Larsen CS, editors. Advances in Dental Anthropology. New York: Wiley-Liss. p Tyrell A, Chamberlain A Non-metric trait evidence for modern human affinities and the distinctiveness of Neanderthals. J Hum Evol 34: Wolpoff M, Wu X, Thorne A Modern Homo sapiens origins: a general theory of hominid evolution involving the fossil evidence from East Asia. In: Smith F, Spencer F, editors. The origins of modern humans: a world survey of the fossil evidence. New York: Alan R. Liss, Inc. p Wu L, Turner CG, II Variation in the frequency and form of the lower permanent molar middle trigonid crest (brief communication). Am J Phys Anthropol 91: Zubov A The epicristid or middle trigonid crest defined. Dent Anthropol Newsletter 6:9 10.