AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 128:287–298 (2005) Metric Dental Variation of Major Human Populations Tsunehiko Hanihara1* and Hajime Ishida2 1 2 Department of Anatomy and Biological Anthropology, Saga Medical School, Saga 849-8501, Japan Department of Anatomy, Faculty of Medicine, University of the Ryukyus, Nishihara, 903-0215, Japan KEY WORDS relationships odontometrics; phenotypic diversity; geographic variation; interpopulation ABSTRACT Mesiodistal and buccolingual crown diameters of all teeth recorded in 72 major human population groups and seven geographic groups were analyzed. The results obtained are ﬁvefold. First, the largest teeth are found among Australians, followed by Melanesians, Micronesians, sub-Saharan Africans, and Native Americans. Philippine Negritos, Jomon/Ainu, and Western Eurasians have small teeth, while East/Southeast Asians and Polynesians are intermediate in overall tooth size. Second, in terms of odontometric shape factors, world extremes are Europeans, aboriginal New World populations, and to a lesser extent, Australians. Third, East/Southeast Asians share similar dental features with sub-Saharan Africans, and fall in the center of the phenetic space occupied by a wide array of samples. Fourth, the patterning of dental variation among major geographic populations is more or less consistent with those obtained from genetic and craniometric data. Fifth, once differences in population size between sub-Saharan Africa, Europe, South/West Asia, Australia, and Far East, and genetic drift are taken into consideration, the pattern of sub-Saharan African distinctiveness becomes more or less comparable to that based on genetic and craniometric data. As such, worldwide patterning of odontometric variation provides an additional avenue in the ongoing investigation of the origin(s) of anatomically modern humans. Am J Phys Anthropol 128:287–298, 2005. © 2005 Wiley-Liss, Inc. During the last few decades, many dental anthropologists have focused on nonmetric crown and root traits for deﬁning the dental characteristics of major geographic groups, and for reconstructing the population history, structure, and origin of modern humans (Hanihara, 1966, 1968; Turner, 1983; Irish, 1997, 1998; Scott and Turner, 1997; Stringer et al., 1997; Tyrrell and Chamberlain, 1998; Irish and Guatelli-Steinberg, 2003). On the other hand, odontometric variation has often been used in the investigation of hominid evolution and/or diversity of local and regional population groups (e.g., Brace, 1967, 1980; Wolpoff, 1971; Hanihara, 1976; Frayer, 1977; Brace and Hinton, 1981; Brace et al., 1984, 1991; Lukacs and Hemphill, 1991; Hillson, 1996; Lukacs et al., 1998; Bermudez de Castro et al., 2004). During the past few decades, some articles on metric dental variation covering a wide range of regional populations were published (Lasker and Lee, 1957; Falk and Corruccini, 1982; Harris and Bailit, 1988; Kieser, 1990; Harris and Rathbun, 1991; Schnutenhaus and Rösing, 1998), and these studies classiﬁed contemporary and recent populations as microdontic, mesodontic, and megadontic (Harris and Rathbun, 1991). However, few researchers have attempted a systematic analysis of geographic variation in metric dental traits on a worldwide scale. Recent genetic studies demonstrated that the majority of the diversity exists within regional populations, with much less among large geographic population groups (Lewontin, 1972; Latter, 1980; Barbujani et al., 1997; Jorde et al., 2000; Brown and Armelagos, 2001). Apart from issues of among-regional variation, analyses of within-group variation consistently reveal that highest levels occur among sub-Saharan Africans (Cann et al., 1987; Stoneking and Cann, 1989; Stoneking, 1993; Bowcock et al., 1994). It is generally accepted that morphological varia- tion among recent human populations is greater than genetic variation (Stringer and Andrews, 1988). Using the craniometric data of Howells (1973, 1989, 1995), Relethford (1994, 2002) and Relethford and Harpending (1994) showed that craniometric diversity among major geographic regions is very limited, at ca. 11–14% of the total variance, and sub-Saharan Africans show the greatest intraregional variation. Relethford and Harpending (1994, 1995) showed, moreover, that sub-Saharan Africa accounted for ca. 50% of the total population size during recent human evolution using craniometric data. Until now, however, assessments of odontometric diversity among and within group variation in major geographical regions have not been presented. The present study has two objectives. The ﬁrst is to present the odontometric characteristics and interpopulation relationships among human populations of major geographic regions to elucidate how such data contribute to © 2005 WILEY-LISS, INC. Grant sponsor: Ministry of Education, Science and Culture in Japan; Grant numbers: Grants-in-Aid for Scientiﬁc Research 1440521, 14540659; Grant sponsor: Japan Fellowship for Research in United Kingdom, Japan Society for the Promotion of Science; Grant sponsor: Smithsonian Opportunities for Research and Study, Smithsonian Institution Fellowship Program. *Correspondence to: Tsunehiko Hanihara, Department of Anatomy and Biological Anthropology, Saga Medical School, 5-1-1 Nabeshima, Saga 849-8501, Japan. E-mail: [email protected] Received 26 July 2003; accepted 1 April 2004. DOI 10.1002/ajpa.20080 Published online 18 April 2005 in Wiley InterScience (www.interscience.wiley.com). 288 T. HANIHARA AND H. ISHIDA our understanding of the patterning of population afﬁnities among modern humans. The second is to present the estimates of the degree of population differentiation within, and diversity among, world regions based on odontometric data. MATERIALS AND METHODS The principal analyses performed in the present study are limited to males because of larger sample sizes than in females, and are based mainly on samples drawn from countries, tribes, and cultural background. Table 1 provides the sample name, sample size, and brief information for those samples included in the dataset. Mesiodistal and buccolingual crown diameters of all teeth (a total of 32 metric variables) were recorded by T.H. to avoid possible interobserver differences. Using a Japanese male sample, intraobserver error was tested by t-statistics and found to be insigniﬁcant. Dental measurements were taken according to the procedures of Moorrees (1957) and Hillson (1996). Datasets were analyzed in the classic way, with the use of principal component analysis (PCA) based on the pooled within-group variance-covariance matrix weighted by sample sizes. Two separate analyses were performed using raw measurements and C-scores to investigate the possible effects of size and shape (Howells, 1989; Brace and Hunt, 1990). Fst values were calculated for both male and female samples drawn from broad geographical areas, following the methods outlined by Relethford and Blangero (1990) and Relethford (1994) to estimate the relative degree of dental variation among regional groups. The detailed procedures for calculation were given elsewhere (Relethford, 1991, 1994; Relethford and Blangero, 1990; Relethford and Harpending, 1994, 1995). Brieﬂy, FST is deﬁned as F ST ⫽ (⌺w i C ii )/(2t ⫹ ⌺w i C ii ), where t is the number of traits and wi is the weighting factors, the relative size of population i, deﬁned as w i ⫽ N i /⌺N j . Nj is the effective size of population j. Cii is the diagonal element of codivergence matrix (C), computed as C ⫽ ⌬G ⫺ 1⌬ⴕ, where G⫺1 is the inverse of the pooled within-group additive genetic variance-covariance matrix, and the elements of ⌬ are the deviations of group means from the total means averaged over all populations weighted by population size. Calculation of the pooled within-group additive genetic variance-covariance matrix (G) from the phenotypic variance-covariance matrix (V) requires an estimate of average heritability for phenotypic traits. According to Relethford (1994), for any given trait, G ⫽ h2V, where h2 is the heritability of the trait. The lowest possible value of FST, the minimum FST, is given when h2 ⫽ 1 (G ⫽ V). The actual Fst, or estimated Fst, requires the estimates of average heritability of odontometric traits. Estimates of standard errors for FST are approximated by the jackknife method (Miller, 1974; Relethford et al., 1997). Many investigators reported relatively high heritability rates for dental dimensions based on family and twin studies (Garn et al., 1968; Goose 1971; Alvesalo and Tigerstedt, 1974; Potter et al., 1976; Townsend and Brown, 1978; summarized by Hillson, 1996). Mizoguchi (1977) reported the heritabilities of mesiodistal crown diameters in permanent dentitions of modern Japanese as ranging from 0.07–1.00 with an average of 0.81 in males, and from 0.41–1.00 with an average of 0.74 in females. Townsend and Brown (1978) estimated heritability valued to average 0.54 ⫾ 0.23 for mesiodistal dimensions and 0.68 ⫾ 0.27 for buccolingual dimensions in Australians. In these studies, however, the upper and lower third molars were not included. As heritability rate (h2) increases, C decreases, so does Fst. In this study, therefore, we tentatively choose an estimate of average heritability for odontometric dimension of 0.55 based on Townsend and Brown’s (1978) mesiodistal estimation to avoid the underestimate of actual Fst values (intraregional variation). We employed the R matrix approach developed by Relethford and Blangero (1990) to estimate interpopulation relationships. The R matrix is given as R ⫽ C(1 ⫺ F ST )/2t. The elements of an R matrix are converted into distances: d ij2 ⫽ r ii ⫹ r jj ⫺ 2r ij . The distance matrix controlled for effective population size and the potential effects of genetic drift on the genetic distance is obtained from scaled R matrix. That is, S ⫽ W 1/2RW 1/2, where W is a diagonal matrix with relative size wi for the ith population. The effect of this transformation is to change the relationship rij between populations i and j to rij(wiwj)1/2 (Relethford and Harpending, 1994, 1995). RESULTS The results of PCA applied to raw measurements are given in Table 2, which summarizes the eigenvectors and proportions of total variation accounted for by each of the ﬁrst three principal components (PCs) with eigenvalues greater than 0.50. The ﬁrst PC, which is only one factor with eigenvalues greater than 1.0, represents overall tooth size, and this factor plays a major role in odontometric variation measured by raw data. Variation in the overall dental size assessed by the ﬁrst PC scores is shown in Figure 1. The Philippine Negrito, Jomon/Ainu, and Western Eurasian samples are characterized by small dentition, and the Australian samples prove to have the largest teeth, followed by the Melanesian, Micronesian, sub-Saharan African, and New World samples, with East/Southeast Asians and Polynesians in between. Table 3 shows the results of PCA based on the C-score. The ﬁrst three PCs which account for just over half (56.7%) of the total variance can be interpreted as representing the relative size of mesiodistal crown diameters against buccolingual diameters, that of molar teeth against other teeth, and that of anterior teeth against premolars, respectively. Figure 2 provides scattergrams of the ﬁrst and second (Fig. 2a) as well as ﬁrst and third (Fig. 2b) PC scores in each sample. In Figure 2a, the shape factors of the dental measurements identify separate phenotypic relationships, with the Native American, Arctic, and Northeast Asian samples having relatively large mesiodistal crown diameters, in contrast to Polynesian and Western Eurasian samples with narrow mesiodistal crown diameters. Polynesian and Western Eurasian samples are separated by the second PC representing the relative size of molars. With the exception of Jomon and Ainu, East and Southeast Asian DENTAL VARIATION OF MAJOR HUMAN POPULATIONS 289 TABLE 1. Materials used and brief information1 Sample name N Information East Asia 1. Japanese 2. Ainu 47–50 25–77 3. Jomon 20–77 4. Northern Chinese 19–53 5. Southern Chinese 12–58 6. Tibetans/Nepalese Northeast Asia 7. Mongol/Buryats 11–77 Tohoku and Kanto regions, Northern part of Honshu (Univ. of Tokyo) Mainly from Hokkaido, including a few specimens from Sakhalin Island (Univ. of Tokyo) Prehistoric (Neolithic) Japan, Middle to the latest Jomon periods (5,300–2,300 years B.P.) (Univ. of Tokyo, National Sci. Museum, Tokyo) Chinese from north of Cheng Kiang River (Univ. of Tokyo, American Museum of Natural History) Chinese from south of Cheng Kiang River (Natural History Museum, Musée de l’Homme, American Museum of Natural History) Tibet and Nepal (lowland) (Natural History Museum, Cambridge Univ.) 27–95 8. Chukchis/NE Asia 6–18 Southeast Asia 9. Vietnam/Thailand 21–130 10. Myanmar 14–90 11. Malay 11–55 12. Early SE Asia 27–60 13. Andaman/Nicobar 14–67 14. Java/Sumatra 27–88 15. Borneo 11–76 16. Philippines 26–89 17. Lesser Sunda 18–51 18. Negritos 13–37 Arctic 19. Aleutian Islands 20. Eskimos North America 21. Northwest Coast 22. Plateau/Great Basin 21–51 17–125 13–86 9–27 23. California 14–53 24. Southwest 20–40 25. Plains/North 31–52 26. Plains/South 11–35 27. Northeastern Woodland/West 21–38 28. Northeastern Woodland/East 18–40 29. Southeastern Woodland 38–55 Ulan Bator, Mongol/Troiskosavsk, Buryats (Musée de l’Homme, Natural History Museum, American Museum of Natural History, National Museum of Natural History) Mainly Chukchis, including a few samples of Evenki Yukagirs and Yakuts (Musée de l’Homme, American Museum of Natural History, National Museum of Natural History) Saigon, Bangkok; Vietnam, and Thailand (Musée de l’Homme, Natural History Museum, American Museum of Natural History) Arakan Hill, Rangoon, Karen; Myanmar (Natural History Museum, Cambridge Univ.) Mainly from Singapore (Natural History Museum, American Museum of Natural History) Mesolithic Malay, Gua Cha; Neolithic Vietnam and Laos; Bang Chang site, early Iron age, Thailand (Cambridge Univ., Musée de l’Homme, Univ. of Hawaii) Recent Andamanese (Onge, Jarawa, etc.) and Nicobarese (Natural History Museum, Cambridge Univ.) Including Nias, Billiton, and Mentawei Islands, Batavia, Madura, Fagal, Pekalongan (Natural History Museum, Cambridge Univ., American Museum of Natural History, Musée de l’Homme) Mainly Land Dayaks, including Iban, Sea Dayaks (Natural History Museum, Cambridge Univ., Musée de l’Homme) Non-Negrito Filipinos from Luzon, Palawan, Panay, Negroes, and Mindanao (Natural History Museum, Cambridge Univ., Musée de l’Homme) Bali, Sumbawa, Flores, and Timor Islands and Celebes and Molucca Island chain (Natural History Museum, Cambridge Univ., Musée de l’Homme, American Museum of Natural History) Mainly Aeta, Luzon, Philippines (Univ. of Tokyo, Natural History Museum, Musée de l’Homme, National Museum of Natural History) Unalaska, Unga, Umnak, Shiplock, Amaknak, Kagamil, Atka, Kanaga, Amlia, Adak, Amchitka, Kiska, Attu, Agatu Islands (American Museum of Natural History, National Museum of Natural History) Lower Yukon River basin, Seward Peninsula, Point Barrow around Bafﬁn Bay, Somerset Island, Prince of Wales, Victoria Island, Greenland (Natural History Museum, American Museum of Natural History, National Museum of Natural History) Tlingit and Bancouver Island (American Museum of Natural History, National Museum of Natural History, Natural History Museum) Washington, Oregon, Utah, Colorado, Wyoming, and Nevada (National Museum of Natural History, American Museum of Natural History) Sacramento Angel Island, San Nicolas Island, Angeles Bay, Santa Barbara, Santa Rosa Island, and Santa Cruz Island (National Museum of Natural History, Musée de l’Homme) Arizona and New Mexico (American Museum of Natural History, National Museum of Natural History) North and South Dakota, Montana, Iowa, and Nebraska (National Museum of Natural History) Kansas, Missouri, Arkansas, Texas, and Oklahoma (National Museum of Natural History) Illinois, Michigan, Wisconsin, Indiana, and Ohio (National Museum of Natural History) New York, Massachusetts, Connecticut, New Jersey, Pennsylvania, Delaware, Maryland, and Kentucky (American Museum of Natural History, National Museum of Natural History) Virginia, Tennessee, Georgia, Alabama, North and South Carolina, Louisiana, Mississippi, and Florida (National Museum of Natural History) (continued) 290 T. HANIHARA AND H. ISHIDA TABLE 1. (Continued) Sample name Central/South America 30. Mexico 31. Peru 32. Fuegians/Patagonians Australia 33. Australia/East 34. Australia/South 35. Australia/North and West Melanesia 36. Papua New Guinea N Information 12–78 Mainly recent Mexico Indians, including Central Cultural region (American Museum of Natural History, National Museum of Natural History) Recent Peruvians (Natural History Museum, National Museum of Natural History) Terra del Fuego and Patagonia region (Natural History Museum, Cambridge Univ., American Museum of Natural History, National Museum of Natural History) 112–115 10–38 19–68 54–155 12–36 11–156 Queensland, New South Wales, and Victoria (Australian Museum, American Museum of Natural History, Natural History Museum, National Museum of Natural History, Cambridge Univ., Musée de l’Homme) Near Adelaide and Murray River Basin (South Australian Museum) Northern Territory and Western Australia (American Museum of Natural History, Natural History Museum, National Museum of Natural History, Cambridge Univ., Musée de l’Homme) Purari River, Fly River, Sepik River, including Torres Strait (Australian Museum, Univ. of Sydney, South Australian Museum, Natural History Museum) Bismarck Archipelago, New Ireland, New Britain (Australian Museum, Univ. of Sydney, South Australian Museum, American Museum of Natural History, National Museum of Natural History, Natural History Museum) Solomon, New Caledonia, Vanuatu, and Fiji (Australian Museum, Univ. of Sydney, South Australian Museum, American Museum of Natural History, National Museum of Natural History, Natural History Museum, Bishop Museum) 37. West Melanesia 24–105 38. East Melanesia 21–148 Micronesia 39. Mariana Islands 40. Caroline Islands 35–75 17–33 Guam, Saipan, and Tinian Islands (Bishop Museum, Musée de l’Homme) Yap, Palau, and Ponape Islands (American Museum of Natural History, Univ. of Tokyo) Polynesia 41. Society 42. Cook 15–48 20–54 Mainly from Tahiti (Musée de l’Homme, Natural History Museum) Manuai, Atiu, Titiaroa, and Mangaia Islands (Natural History Museum, Kyoto Univ., Musée de l’Homme) New Zealand and Chatham Islands (Australian Museum, Univ. of Sydney, South Australian Museum, Natural History Museum, Cambridge Univ., American Museum of Natural History, National Museum of Natural History) Hatua Tua, Nuku Hiva, Ua Huka, and Fatu Hiva (Bishop Museum, Natural History Museum, Musée de l’Homme, American Museum of Natural History) Mainly from Mokapu site, Oahu (Bishop Museum, Cambridge Univ.) Including a few samples from Lanai and Kauai (Bishop Museum) Kona site, H1 site; Hawaii Island (Bishop Museum) 43. Maori/Moriori 15–119 44. Marquesas 15–71 45. Oahu/Hawaii 46. Maui-Molokai/Hawaii 47. Hawaii/Hawaii South Asia (India) 48. India/North 49. India/South West Asia 50. Afghanistan/Pakistan 51. Turkey/Cyprus 52. Early Iran/Israel 48–123 21–50 16–40 26–169 13–57 9–44 7–42 21–89 Bengal, Behar, Orissa, Bombay, Punjab, and Kashmir (Natural History Museum, American Museum of Natural History) Madras, Malabar, and Mysore (Natural History Museum, American Museum of Natural History) Helmand Valley; Mogul, Kandahar; Kotal; Priest; Pecheen Valley; Kalati; Pamir Plat., including a few specimens from West Asia (Natural History Museum, American Museum of Natural History) Adevis, Marash; Aintab; Adalea; Ephesos: Kurd, Mohammedan, Armenian; Hellenismic period of Cyprus (Natural History Museum, American Museum of Natural History) Tell Duweir (Lachish), Bronze and Iron Age; Israel/Bronze to Achaemenian period (6–4 centuries B.C.) of Iran (Natural History Museum, Univ. of Tokyo) North Africa 53. Egypt/Predynasty 54. Egypt/12–29th Dynasty 17–63 12–176 Badari and Naqada, ca. 5,000–4,000 B.P. (Cambridge Univ.) Lisht, Cairo, Omdurman, and Gizeh (Cambridge Univ., National Museum of Natural History) Europe 55. Greek 11–28 Ancient and recent Greece; Cyrene, Rhodes, Corfu, Athens, Attica (Natural History Museum) Crimea, Courland, Latvia, Pskoff, Uzbekistan, Odessa, Tambow (Natural History Museum, National Museum of Natural History) Charvaty, near Olomouc, Central Moravia; including a few samples from East Europe (Poland, Yugoslavia, Herzegovina) (South Australian Museum, Natural History Museum) (continued) 56. Russia 12–38 57. Czecho 12–54 DENTAL VARIATION OF MAJOR HUMAN POPULATIONS 291 TABLE 1. (Continued) Sample name N 58. Hungary 12–40 59. Germany 24–46 60. Austria/Swiss 10–40 61. Italy 62. France 26–93 12–56 63. Finland/Ural 10–72 64. UK/Ensay 65. UK/Poundbury 66. UK/Spitalﬁelds1 67. UK/Spitalﬁelds2 Sub-Saharan Africa 68. Nigeria/Ghana 69. Somalia 70. Kenya 36–59 47–95 10–64 33–54 34–259 13–59 19–77 71. Tanzania 13–94 72. South Africa 26–86 Information Demko-Hegy; Czakbereny, Roman Period; Demko Hegy, 11–12th centuries; Nagy-sap, Csakover, 11th century; Stuhlweisenberg; Pressburg (Natural History Museum, American Museum of Natural History) Berlin, Mainz, Holstein, Westphalia (Natural History Museum, National Museum of Natural History) Tirol; St. Peter above Tweng, Carinthia, 16–17th centuries; Malta, Millstatt, Carinthia; Raach, near Gloggnitz; Modling, near Vienna; Vienna/Austria; Lenz Canton, Grisons/Switzerland (American Museum of Natural History National Museum of Natural History) Ancient and recent Italians (Natural History Museum) Merovingian, Gallo-Roman, Brittany times; Paris, etc. (Natural History Museum) Recent Finns, including a few specimens of Ural language people (Natural History Museum) Late Medieval to Postmedieval periods, Scotland (Natural History Museum) Late Roman period, Southwest England (Natural History Museum) Mid-Victorian period, London (Natural History Museum) Pre-17th century, London (Cambridge Univ.) Ibo and Ashanti tribes (Natural History Museum, Cambridge Univ.) Erigavo District, Ogaden Somali (Cambridge Univ.) Ngorongoro, Turkana, Kikuyu, Kaurite to Fort Hall (Cambridge Univ., Natural History Museum, Cambridge Univ., American Museum of Natural History) Tanganika Territory, Loe, Haya Tribe (Natural History Museum, Cambridge Univ., American Museum of Natural History) Zulu and once called Kafﬁrs (Natural History Museum, Cambridge Univ., American Museum of Natural History, National Museum of Natural History) 1 N, range of N in samples (since each of traits observed has a different N); Univ., University; Sci., Science; Univ. of Tokyo, Tokyo, Japan; Kyoto Univ., Kyoto, Japan; National Sci. Museum, Tokyo, Japan; American Museum of Natural History, New York; National Museum of Natural History, Washington, DC; Bishop Museum, Honolulu; Univ. of Hawaii, Honolulu; Natural History Museum, London, UK; Cambridge Univ., Cambridge, UK; Musée de l’Homme, Paris, France; Australian Museum, Sydney, Australia; Univ. of Sydney, Sydney, Australia; South Australian Museum, Adelaide, Australia. samples together with the Melanesian and Micronesian samples share similar characteristics with each other and with sub-Saharan African samples. Australian, Jomon, and Indian Subcontinent samples occupy a position intermediate between New World and Western Eurasian samples. The Ainu sample is plotted at the near position of Northeast Asian samples. The Australian samples show distinctive dental features in the third PC representing relatively large anterior teeth. Among-group dental variation estimated by Fst was computed for ﬁve Old World samples (Far East, Australia, South/West Asia, Europe, and sub-Saharan Africa) and seven worldwide samples including Paciﬁc and New World in both male and female datasets. The geographic groups used and the number of individuals for each sex are provided in Table 4. Table 5 gives the minimum Fst values and estimated Fst values using an average heritability of 0.55. The Fst values obtained reveal that extensive odontometric diversity exists within regional populations, with much less diversity between regional populations. Table 6 gives the results of the method of Relethford and Blangero (1990) for estimating intraregional variations under the assumption of equal effective population size. Intraregional variation is largest in the sub-Saharan African group, followed closely by the Australian group. The New World and European groups, on the other hand, show small intraregional variation. Using the estimated Fst values, the R matrix for the ﬁve Old World samples is calculated. The New World and Paciﬁc samples are excluded, since they represent newly diverged populations (Relethford and Harpending, 1994). Figure 3a illustrates the interpopulation relationships derived from the ﬁrst two eigenvectors of the R matrix scaled by the square root of the corresponding eigenvalues, assuming equal effective population sizes in the ﬁve geographical samples. Among males, the Australian sample is distinctive, while sub-Saharan African and Far East samples appear close. On the other hand, Australian and sub-Saharan African samples are distinctive for females. Relethford and Harpending (1994, 1995) pointed out that it is necessary to control for variation in population size for reconstructing population relationships without the effect of different degrees of genetic drift. Following the suggestion of Relethford and Harpending (1994) that the population of sub-Saharan Africa was three times that of any of the other geographical regions, a scaled R matrix was calculated whereby Far East, Australia, South/West Asia, and Europe samples were weighted as one each and sub-Saharan Africa as three, to account for relative effective population size. Figure 3b was drawn using the scaled eigenvectors of the scaled R matrix. In both sexes, interpopulation relationships are similar to those obtained by unscaled R matrix analysis, in which the Australian sample stands out as distinctive. However, the sub-Saharan African sample moves more or less away from the Far East sample in males. DISCUSSION The results of this study conﬁrm the trifurcation of contemporary and recent populations into those that are microdontic, mesodontic, and megadontic (Harris and Rathbun, 1991). It was asserted for several decades that 292 T. HANIHARA AND H. ISHIDA TABLE 2. Eigenvalues and eigenvectors of variance-covariance matrix by PCA, based on raw measurement data Tooth UI1-MD UI2-MD UC-MD UP1-MD UP2-MD UM1-MD UM2-MD UM3-MD LI1-MD LI2-MD LC-MD LP1-MD LP2-MD LM1-MD LM2-MD LM3-MD UI1-BL UI2-BL UC-BL UP1-BL UP2-BL UM1-BL UM2-BL UM3-BL LI1-BL LI2-BL LC-BL LP1-BL LP2-BL LM1-BL LM2-BL LM3-BL Eigenvalues Proportion Cumulative proportion PC-1 PC-2 PC-3 0.16934 0.16405 0.18002 0.18397 0.18992 0.18779 0.19168 0.17043 0.17068 0.17968 0.18390 0.18213 0.18600 0.18651 0.19132 0.18675 0.16763 0.16277 0.17656 0.17897 0.18043 0.19254 0.18785 0.16091 0.12138 0.13628 0.15836 0.16610 0.16733 0.18717 0.19356 0.19159 4.40350 0.43823 0.43823 ⫺0.16099 ⫺0.29241 ⫺0.18091 ⫺0.09076 ⫺0.10830 ⫺0.14915 ⫺0.09757 ⫺0.08201 ⫺0.20374 ⫺0.21945 ⫺0.17263 0.02432 0.03953 ⫺0.16409 ⫺0.07491 0.01090 ⫺0.01470 ⫺0.00779 0.14221 0.11318 0.21718 ⫺0.01858 0.13670 0.23574 0.35629 0.36690 0.17372 0.28941 0.30720 ⫺0.12776 ⫺0.01166 0.04129 0.90329 0.08989 0.52812 ⫺0.19786 0.06159 0.08594 0.33084 0.16924 ⫺0.10561 ⫺0.07744 ⫺0.27485 ⫺0.01214 ⫺0.06007 0.07390 0.34568 0.22341 0.09128 ⫺0.11603 ⫺0.15608 ⫺0.20763 ⫺0.05580 ⫺0.20498 0.35693 0.17422 ⫺0.14932 ⫺0.14911 ⫺0.13629 ⫺0.24713 ⫺0.08257 ⫺0.12772 0.26393 0.15686 ⫺0.03258 ⫺0.07386 0.00403 0.56595 0.05632 0.58445 tooth size has been exposed to natural selective forces beginning in the Upper Paleolithic (Frayer, 1978; Calcagno and Gibson, 1988, 1991). Macchiarelli and Bondioli (1986) suggested the increasing population density effect on tooth size reduction. Brace (1967) and Brace et al. (1984, 1991) argued that tooth size reduction is a consequence of what they called the probable mutation effect, i.e., large tooth size is maintained by strong natural selection, but reduction in tooth size occurs in the absence of such pressures in relation to the development of sophisticated food preparation techniques and pottery use. As expected, modern Australian Aboriginals possess the least reduced teeth, followed by Melanesians, sub-Saharan Africans, and Native Americans. Together with the Philippine Negritos, the most extensive dental size reduction occurs in populations occupying the western part and eastern edge of the Eurasian continent, i.e., Europeans and the Jomon/Ainu of Japan. Such results are in agreement with the relationship between tooth size reduction and cultural background among recent populations of the world found by Brace et al. (1991). It is well-known that modern Europeans and the Ainu are living descendents of the ﬁrst people to use cooking in the preparation of food and to use pottery (Brace et al., 1991). The small tooth size observed in Negritos is likely a byproduct of an overall diminutization of body size (Hillson, 1996). When the allocation of relative tooth size across all 32 variables forms the basis of comparison, New World populations, including occupants of the Arctic, Polynesians, Europeans, and to a lesser extent, Australians, form the extremes of contemporary worldwide variation. East/Southeast Asians, Melanesians, and the Indian Subcontinent, together with sub-Saharan Africans, form an average group. Such ﬁndings are more or less consistent with those obtained by Scott and Turner (1997) from nonmetric dental traits. In Figure 2, the geographical groups with relatively large intraregional variation (Table 6) are plotted at a central position, and clinal variation of the traits is recognized. Such results may be consistent with the center and edge model proposed by Thorne and Wolpoff (1981), according to which phenotypic variation is expected to be greatest at the geographical center of a species range, and lower in peripheral populations. The present ﬁndings (Fig. 2) do not support the division of East Asian populations into sinodonts and sundadonts proposed (Turner, 1987, 1990; Scott and Turner, 1997) from analyses of nonmetric dental traits. Turner (1987, 1989, 1990, 1992) designated the major populations of China and Japan as sinodonts, and suggested that these populations were more similar in dental trait frequencies to Northeast Asians and New World populations than to the sundadont populations of Southeast Asia and the Paciﬁc. Turner (1990) identiﬁed the prehistoric Jomon and recent Ainu of the Japanese Archipelago as sundadont populations residing as isolated pockets within the range of sinodonts. The patterning of phenetic afﬁnities of East Asians based on relative dental size is profoundly different from those obtained from comparisons of morphological trait frequencies. The results of this study indicate that Chinese and Japanese populations are more like Southeast Asian populations, while the prehistoric Jomon show afﬁnities with Australian and Papuan populations. In direct opposition to results from dental morphological studies, patterning of relative tooth size among the Ainu shows similarities to that seen among Northeast Asian and New World populations. Recently, genetic afﬁnities between Ainu and East/ Northeast Asians and morphological similarities between Ainu and Paleoindians were suggested (Cavalli-Sforza et al., 1988; Nei, 1995; Omoto, 1995; Omoto and Saitou, 1997; Brace et al., 2001). Unfortunately, we cannot conﬁrm this Ainu-Paleoindian connection from results obtained in the current study. This is because an ancestordescendent relationship between Early and Late Holocene American populations remains, as yet, unconﬁrmed (Steele and Powell, 1992; Lahr, 1995; Jantz and Owsley, 2001, 2003; Van Vark et al., 2003). However, should it be that Native Americans are derived from prehistoric Northeast Asians with more generalized craniofacial features (Howells, 1959; Lahr, 1995, 1996), the dental morphological shift of Ainu to the Northeast Asians and Native Americans throws light on the relationships between prehistoric Northeast Asia and Hokkaido. Relethford (1994, 2002) emphasized that the patterning of modern human variation yields important insights into the origin and evolution of modern humans. However, the technique employed to estimate such variation (interregional diversity (Fst), intraregional variance, and interregional relationships based on R matrix method) requires neutrality with respect to natural selection (Relethford and Blangero, 1990; Relethford, 1994, 2002; Relethford and Harpending, 1994). It was asserted that tooth size has been exposed to strong natural selective force (Brace et al., 1991). It is true that overall tooth size plays a major role in odontometric variation, but when the effects of overall tooth size are eliminated with standardized data, several independent vectors with eigenvalues greater than 1.0 Fig. 1. First PC scores based on raw measurement data, representing overall tooth size. 294 T. HANIHARA AND H. ISHIDA TABLE 3. Eigenvalues and eigenvectors by PCA based on C-score data Tooth UI1-MD UI2-MD UC-MD UP1-MD UP2-MD UM1-MD UM2-MD UM3-MD LI1-MD LI2-MD LC-MD LP1-MD LP2-MD LM1-MD LM2-MD LM3-MD UI1-BL UI2-BL UC-BL UP1-BL UP2-BL UM1-BL UM2-BL UM3-BL LI1-BL LI2-BL LC-BL LP1-BL LP2-BL LM1-BL LM2-BL LM3-BL Eigenvalues Proportion Cumulative proportion PC-1 PC-2 PC-3 PC-4 PC-5 PC-6 PC-7 ⫺0.22335 ⫺0.18840 ⫺0.08187 ⫺0.16201 ⫺0.16839 ⫺0.20793 ⫺0.06484 ⫺0.11277 ⫺0.25291 ⫺0.22331 ⫺0.10153 ⫺0.16187 ⫺0.17386 ⫺0.21998 ⫺0.12699 ⫺0.11090 0.18270 0.17877 0.26706 0.16003 0.15295 0.13461 0.19935 0.06116 0.21111 0.23865 0.30723 0.21658 0.18150 0.03302 0.10675 0.01628 9.38943 0.29342 0.29342 0.10680 0.18218 0.18718 0.26421 0.16645 ⫺0.13457 ⫺0.14163 ⫺0.18236 0.12184 0.16635 0.18296 0.19182 0.09315 ⫺0.18262 ⫺0.22224 ⫺0.28359 0.08271 0.10280 0.14224 0.24739 0.19008 ⫺0.13838 ⫺0.12569 ⫺0.19313 0.07382 0.06074 0.05414 0.09345 0.06025 ⫺0.23382 ⫺0.27117 ⫺0.32702 5.44359 0.17011 0.46353 0.22973 0.17820 0.14032 ⫺0.23799 ⫺0.24958 0.04751 ⫺0.14380 0.05841 0.25650 0.24531 0.13036 ⫺0.23278 ⫺0.25798 0.04635 ⫺0.13627 0.01663 0.20935 0.11141 0.16187 ⫺0.23196 ⫺0.28895 0.03864 ⫺0.12785 ⫺0.01663 0.25434 0.22533 0.14797 ⫺0.14752 ⫺0.23137 0.04094 ⫺0.10987 0.03937 3.29825 0.10307 0.56660 ⫺0.00541 ⫺0.03247 0.03843 ⫺0.04328 ⫺0.04970 0.26044 0.13207 ⫺0.40860 ⫺0.03578 ⫺0.00497 0.08958 0.03189 0.05289 0.25125 0.20492 ⫺0.37093 0.05462 ⫺0.08483 0.01212 ⫺0.05023 ⫺0.10188 0.27499 0.12994 ⫺0.39146 0.05205 0.00336 0.02426 ⫺0.01182 ⫺0.02688 0.30512 0.18694 ⫺0.28955 2.32693 0.07272 0.63932 0.10623 0.06819 ⫺0.00379 0.03523 0.03963 0.21346 0.15127 0.06736 0.04473 0.02993 ⫺0.15519 ⫺0.22565 ⫺0.25353 ⫺0.08639 ⫺0.22937 ⫺0.14442 0.03569 ⫺0.00087 ⫺0.01250 0.16821 0.21729 0.39554 0.37601 0.25307 ⫺0.12802 ⫺0.19316 ⫺0.20117 ⫺0.17695 ⫺0.21049 ⫺0.08005 ⫺0.20762 ⫺0.16442 1.83195 0.05725 0.69657 ⫺0.06150 0.03326 0.02725 ⫺0.04944 0.19367 ⫺0.00186 0.48994 0.08997 ⫺0.09189 ⫺0.14679 ⫺0.12158 ⫺0.05344 0.13985 ⫺0.13264 0.30339 ⫺0.02909 0.15807 0.24452 0.13667 ⫺0.25620 ⫺0.08535 ⫺0.22107 0.12569 ⫺0.06073 0.08032 0.10494 0.08264 ⫺0.22781 ⫺0.16988 ⫺0.37151 ⫺0.03774 ⫺0.19843 1.58110 0.04941 0.74598 ⫺0.18813 ⫺0.07503 0.52194 ⫺0.00693 ⫺0.04832 0.01058 0.02062 0.06151 ⫺0.24680 ⫺0.10201 0.48720 ⫺0.02439 ⫺0.06685 0.00070 ⫺0.02905 0.09786 ⫺0.20974 ⫺0.07970 0.26124 ⫺0.01678 ⫺0.00503 0.06649 0.02953 ⫺0.00269 ⫺0.30195 ⫺0.18596 0.25746 ⫺0.14516 ⫺0.11698 ⫺0.03660 ⫺0.02409 0.05264 1.05119 0.03285 0.77883 TABLE 6. Intraregional variance TABLE 4. Number of individuals used in R-matrix method Number of individuals Geographical regions Male Female Far East Australia South/West Asia Europe Sub-Saharan Africa Paciﬁc New World 1,162 308 923 1,006 772 844 1,052 278 193 78 171 90 258 431 TABLE 5. Fst values reflecting relative degree of interregional variation for each sex Sex Male Female No. of regions Minimum Fst S.E. Estimated Fst S.E. 5 7 5 7 0.1275 0.1127 0.1328 0.1214 0.0013 0.0011 0.0036 0.0028 0.1958 0.1747 0.2033 0.1872 0.0012 0.0010 0.0032 0.0025 remain. The intention of these signiﬁcant eigenvectors conﬁrms that the dataset used as the basis for R matrix analyses provides information beyond overall size. Indeed, as shown in the PCA results based on raw measurement data, factors other than overall size account for more than half (56.7%) of the total variance. This study revealed that less than 20% of the overall patterning of odontometric diversity occurs between geographic regions (Table 5). As such, the apportionment of diversity estimated from metric dental data is in general Variance observed Regions 5 Old World regions Far East Australia South/West Asia Europe Sub-Saharan Africa 7 Worldwide regions Far East New World Australia Paciﬁc South/West Asia Europe Sub-Saharan Africa Male Female 1.0318 1.0885 0.9828 0.8893 1.0972 1.0034 1.0216 1.0038 0.9976 1.0279 1.0499 0.9561 1.1080 0.9816 0.9999 0.9057 1.1151 1.0353 0.9453 1.0528 1.0520 1.0424 1.0248 1.0579 concordance with results obtained from genetic markers, DNA polymorphism (6 –25%), and craniometrics (11–14%) (Ryman et al., 1983; Barbujani et al., 1997; Jorde et al., 2000; Relethford, 1994, 2002), all of which stand in direct opposition to between-group allocation estimates obtained from variation in skin color (ca. 90%) (Relethford, 2002). Many genetic studies document a higher level of withinregional diversity in sub-Saharan Africa than in other geographic regions (Cann et al., 1987; Stoneking and Cann, 1989; Rogers and Jorde, 1995). Relethford and Harpending (1994) found the same pattern of elevated within-regional diversity of sub-Saharan Africans in their worldwide craniometric study. The present results add another system of biological variation, odontometry, Fig. 2. Scattergrams of ﬁrst and second PC scores (a) and ﬁrst and third PC scores (b), based on C-score data. 296 T. HANIHARA AND H. ISHIDA Fig. 3. Scattergrams based on eigenvectors of R matrix under assumption of equal effective population sizes (a) and of scaled R matrix using relative effective population weights of sub-Saharan Africa ⫽ 3, and Far East ⫽ Australasia ⫽ South/West Asia ⫽ Europe ⫽ 1 (b). which indicates that the largest amount of intraregional diversity occurs among the inhabitants of sub-Saharan Africa. Examinations of the unscaled and scaled R matrix results reveal fundamentally different patterns by sex. Among males, Australians are identiﬁed as the most distinctive regional group. Among females, this distinctiveness occurs for sub-Saharan Africans rather than Austra- lians. Although potential problems remain with regard to estimation of hereditability of metric dental traits, sample selection, methodological concerns, and so forth, the patterns of variation presented here are in essential agreement with those obtained from genetic and craniometric analyses. While some investigators suggested that the low within- and between-group variance, relatively high interobserver error, and strong method dependency render DENTAL VARIATION OF MAJOR HUMAN POPULATIONS odontometric variation of little value for distinguishing between recent human populations on a microevolutionary level (Lasker and Lee, 1957; Harris and Bailit, 1988; Kieser, 1990; Falk and Corruccini, 1982; Schunutenhaus and Rösing, 1998), the results of the present study suggests that odontometric variation is efﬁcacious for assessment of patterning among modern human populations on a larger, worldwide scale. ACKNOWLEDGMENTS For their kind permission to study the materials under their care, we express our sincere thanks to T. Molleson, R. Kruszynski, L.T. Humphrey, and C. Stringer of the Natural History Museum, London; R. Foley, M.M. Lahr, and M. Bellatti of the Department of Biological Anthropology, University of Cambridge; A. Langaney and M.A. Pereira da Silva of the Laboratoire d’Anthropologie Biologique, Musée de l’Homme, Paris; D. Hunt, D. Owsley, S. Ousley, R. Potts, M. London, and D.H. Ubelaker of the Department of Anthropology, National Museum of Natural History, Smithsonian Institution, Washington, DC; I. Tattersall, K. Mowbray, and G. Sawyer of the Department of Anthropology, American Museum of Natural History, New York; J. Spechit, P. Gordon, L. Bonshek, and N. Goodsell of the Department of Anthropology, Australian Museum, Sydney; J. Stone and D. Donlon of the Department of Anatomy and Histology, University of Sydney; D. Henley of the New South Wales Aboriginal Land Council, Sydney; M. Chow, a dentist in Sydney; M. Hanihara of the School of Languages, Macquarie University, Sydney; C. Pardoe and G.L. Pretty of the Department of Anthropology, South Australian Museum, Adelaide; Y.H. Sinoto of the Department of Anthropology, the Bernice P. Bishop Museum, Honolulu; M. 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