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Objectives: In the first issue of the American Journal of Physical Anthropology, E.A. Hooton noted the expression of Eskimoid characteristics in the Icelandic skull, one of which was mandibular torus. Our goal is to evaluate this trait in another North Atlantic population, the Greenlandic Norse. Materials and methods: An investigation of mandibular torus was carried out on all Greenlandic Norse skeletons disinterred up to 1986 (n = 109), along with comparative samples from Iceland (n = 82), Norway (n = 98), and Denmark (n = 64). Torus expression was scored on a six grade scale with absence and five degrees of trait presence. Results: Greenlanders and Icelanders show extraordinarily high frequencies (65-97%) and pronounced expressions of mandibular torus. More surprising was the almost complete absence of this trait in a Danish Viking sample (9%) and a significantly lower frequency in medieval Norwegians (48%). Discussion: The dramatic expression of mandibular torus in the Greenlandic Norse and their contrast to related Scandinavian populations in Europe stimulated the collection of data from the literature and the database of Christy G. Turner II for 49,970 individuals in 335 populations. When plotted on a global scale, mandibular torus shows a strong clinal distribution with the highest frequencies in northern latitudes and the lowest frequencies around the equator. Although mandibular torus has some hereditary component, as indicated by family studies, the trait has a strong environmental component of variance. How factors of a northern environment, including climatic stress and dietary behavior, influence torus expression remains enigmatic.
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BRIEF COMMUNICATION
Northern exposure: Mandibular torus in the Greenlandic Norse
and the whole wide world
G. Richard Scott
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Roman Schomberg
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Victoria Swenson
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Donovan Adams
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Marin A. Pilloud
Department of Anthropology/MS 0096,
University of Nevada Reno, Reno, NV
89557
Correspondence
G. Richard Scott, Department of
Anthropology/MS 0096, University of
Nevada Reno, Reno NV 89557
Email: grscott@unr.edu
Abstract
Objectives: In the rst issue of the American Journal of Physical Anthropology, E.A. Hooton noted
the expression of Eskimoid characteristics in the Icelandic skull, one of which was mandibular
torus. Our goal is to evaluate this trait in another North Atlantic population, the Greenlandic
Norse.
Materials and methods: An investigation of mandibular torus was carried out on all Greenlandic
Norse skeletons disinterred up to 1986 (n5109), along with comparative samples from Iceland
(n582), Norway (n598), and Denmark (n564). Torus expression was scored on a six grade scale
with absence and ve degrees of trait presence.
Results: Greenlanders and Icelanders show extraordinarily high frequencies (6597%) and pro-
nounced expressions of mandibular torus. More surprising was the almost complete absence of
this trait in a Danish Viking sample (9%) and a signicantly lower frequency in medieval Norwe-
gians (48%).
Discussion: The dramatic expression of mandibular torus in the Greenlandic Norse and their con-
trast to related Scandinavian populations in Europe stimulated the collection of data from the
literature and the database of Christy G. Turner II for 49,970 individuals in 335 populations. When
plotted on a global scale, mandibular torus shows a strong clinal distribution with the highest fre-
quencies in northern latitudes and the lowest frequencies around the equator. Although
mandibular torus has some hereditary component, as indicated by family studies, the trait has a
strong environmental component of variance. How factors of a northern environment, including
climatic stress and dietary behavior, inuence torus expression remains enigmatic.
1
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INTRODUCTION
The Norse colonized Greenland from Iceland in A.D. 986. During their
500 year occupancy of the island, the Norse exhibited a number of
temporal trends, including decreases in tooth, brain, and body size and
an increase in third molar agenesis (Scott, Halman, & Pedersen,
1992). Another trait that exhibits an interesting pattern of variation is
mandibular torus, a bony growth on the lingual side of the mandible.
Mandibular torus has long been known to be common among northern
groups, especially Eskimos, Aleuts, and Lapps (Hrdlička, 1940; Moor-
rees, 1957; Oschinsky, 1964; Schreiner, 1935). None, however, exhibit
this torus to such a degree as the Greenlanders (Scott, Halman, &
Pedersen, 1992; Sellevold, 1980).
Researchers have long debated the etiology of mandibular tori.
The higher frequencies in Asians compared to Europeans (Jainkittivong
& Langlais, 2000) led some to argue the trait is heritable (Carson, 2006;
Sawyer, Allison, Elzay, & Rezzia, 1979). Even granted this pattern of
variation, there is disagreement as to how genes contribute to the
development of these bony exostoses. Early studies described the
mode of inheritance as either autosomal dominant or autosomal reces-
sive (Alvesalo & Kari, 1972; Johnson, Gorlin, & Anderson, 1965; Krahl,
1949; Suzuki & Sakai, 1960). Some studies suggest mandibular torus is
inherited as a monoallelic trait with complete or partial penetrance, an
explanation utilized when patterns of segregation are not consistent
with simple Mendelian models (e.g., Gould, 1964). Moorrees, Osborne,
and Wilde (1952) suggested three independent loci control tori
American Journal of Physical Anthropology 2016; 00: 00-00 wileyonlinelibrary.com/journal/ajpa V
C2016 Wiley Periodicals, Inc.
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1
Received: 29 April 2016
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Revised: 20 June 2016
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Accepted: 1 July 2016
DOI 10.1002/ajpa.23053
expression. In a recent study, researchers found 93.6% of monozygotic
twins were concordant for mandibular torus expression. Dizygotic
twins, by contrast, had a concordance rate of 79.4% (Au
skalnis et al.,
2015). The most parsimonious interpretation holds that mandibular
torus is a threshold trait with a polygenic mode of inheritance. Despite
disagreement on mode of inheritance, family and twin studies nonethe-
less indicate heredity plays some role in mandibular torus development.
Several environmental causes have been proposed to explain the
presence and variation in mandibular torus. Eggen (1989) examined
individuals with mandibular torus in two categories: those who brux
and those who do not. From this comparison, he estimated that 30%
of mandibular torus expression is dictated by genes with the remaining
70% reecting environmental factors (e.g., occlusal stress). Occlusal
stress and parafunctional activity may be important components of the
production of these exostoses (Hassett, 2006; Igarashi, 2016; Johnson,
1959; Kerdpon & Sirirungrojying, 1999; Pechenkina & Benfer, 2002).
Mayhall (1970) and Eggen and Natvig (1991) suggest a coarse diet pro-
motes the development of mandibular torus. Eggen (1993) also pro-
posed that a marine diet with high levels of omega-3 fatty acids and
vitamin D might promote excessive bone growth with a possible inu-
ence on unusually large mandibular and palatine tori. This idea was
tested by Baumann, Lynnerup, and Scott (in press) who examined the
relationship between torus expression and stable carbon and nitrogen
isotope compositions in Greenlandic Inuit and Norse. For the most
part, these authors found no signicant association between stable iso-
topes and torus. The only statistically signicant nding was an inverse
relationship between mandibular torus expression and stable nitrogen
isotope levels in the Inuit (but not the Norse).
Mandibular torus is uncommon in young individuals although rela-
tively high frequencies have been reported for Lapp and Aleut children
(Moorrees, Osborne, and Wilde, 1952). Haugen (1992) found a larger
number of individuals with mandibular torus in the 35- to 65-year-age
group. Jainkittivong and Langlais (2000) identied a statistically signi-
cant prevalence that increases with age in a Thai sample. Topazian and
Mullen (1977) suggest those with a predisposition for mandibular torus
exhibit continuous growth of this exostosis throughout life. Other
researchers have found it becoming more pronounced over the course
of an individuals lifetime relative to specic climatic, dietary, and life-
style factors (Axelsson & Hedegård, 1981; Eggen, 1989; Hrdlička,
1940; Ihunwo & Phukubye, 2006; Jainkittivong & Langlais, 2000;
Pechenkina & Benfer, 2002). This suggests that while mandibular torus
is heritable, environmental factors such as masticatory stress inuence
the degree to which tori are expressed (Carson, 2006; Moorrees,
Osborne, and Wilde, 1952).
There is disagreement among researchers regarding sex dierences
in mandibular torus. Some have found no sex dierences in torus expres-
sion while others report higher frequencies in either males or females.
No consistent pattern has emerged across dozens of studies and hun-
dreds of samples. This contrasts with palatine torus, which shows a con-
sistent bias in favor of females (Halman, Scott, & Pedersen, 1992).
Our goal is to evaluate the geographic and temporal variation of
mandibular torus among Norse populations in the North Atlantic, with
a focus on Greenlanders. Additionally, we want to determine how the
pattern of torus variation among Europeans in this part of the world
compares to populations in every environmental setting imaginable,
from the Arctic to subarctic, temperate deciduous forests, grasslands,
tropical rainforests, deserts, and Pacic islands. Excluding Antarctica,
every continent is sampled.
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MATERIALS
All Greenlandic Norse skeletons excavated up to 1986 were examined
in this study. The Eastern settlement sites of Herjolfnes and Gardar
along with the Western settlement sites of Sandnes and Anavik were
excavated by P. Nørlund and A. Roussel between 1921 and 1932
(Nørlund, 1924, 1929; Roussell, 1936, 1941). The Benedictine Convent
of the Eastern settlement was excavated by C.L. Vebæk from 1945 to
1948 (Vebæk, 1956). K. Krogh and J.B. Jørgensen excavated Thjod-
hilds Church during the 1960s (Krogh, 1967; Lynnerup, 1998).
Comparative data were collected from Icelandic, Norwegian, and
Danish samples. The Icelandic sample, excavated in 1905 by V. Stean-
son, dates around the 14th and 15th centuries and is comprised of
remains excavated from Alftanes Island and Haordery (Hooton,
1918). C. Long excavated the Norwegian sample in the 1970s from the
medieval church of St. Gregorys in Trondheim, Norway (Hanson,
FIGURE 1 Six grade scale used to score mandibular torus
expression in the Norse; grade 1 not shown as it is only evident
through palpation
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SCOTT ET AL.
1986). This sample dates from the early 12th century to 1531. While
the Norwegian and Icelandic samples are medieval in age, the Danish
sample came from a variety of Viking age burials dating between A.D.
800 and 1000.
Although the dates of each burial location in Greenland are not
precise, they can be placed in a broad temporal framework. Thjodhilds
Church, dating to the early years of occupation (ca. A.D. 10001150),
is referred to as the Early Eastern Settlement. Burials from the sites of
Sandnes and Anavik make up the Western Settlement sample. Due to
temporal complications and small sample sizes, Gardar, Herjolfnes, and
the Benedictine Convent were combined to create a Middle Late East-
ern Settlement sample that is roughly contemporaneous with the
Western settlement sample (ca. 13th-14th centuries). Radiocarbon
dates on human bone corroborate these temporal assignments (Arne-
borg et al., 1999).
The above data were collected by the rst author (GRS). However,
to put the North Atlantic Norse into a broader world context, data
were obtained from a wide variety of published sources. When geo-
graphic areas were underrepresented, we went through the original
data sheets of Christy G. Turner II (CGT II) to ll in the blanks. This was
particularly true for Southeast Asia, Australia and the Pacic, Mesoa-
merica, and South America. We report mandibular torus frequencies
for 335 world populations. From the literature, data were obtained for
42,418 individuals from 202 samples; an additional 7,552 individuals
TABLE 1 Expression of mandibular torus in Vikings, Norwegians, Icelanders, and Norse Greenlanders
Age Grade of Expression Total X
2
X
2
Mean trait
Sample Sex Range n0 1 2 3 4 5 Frequency age sex score
Vikings M 1830 16 93.8 6.3 0.0 0.0 0.0 0.0 6.3
F 7 100.0 0.0 0.0 0.0 0.0 0.0 0.0 NA
M30622 95.5 4.5 0.0 0.0 0.0 0.0 4.5 NA
F 19 78.9 15.8 5.3 0.0 0.0 0.0 21.1 NA
Total 64 90.6 7.8 1.6 0.0 0.0 0.0 9.4 0.109
Norwegians M 1830 15 73.3 13.3 13.3 0.0 0.0 0.0 26.7
F 16 43.8 31.3 25.0 0.0 0.0 0.0 56.2 0.036
M30635 54.3 34.3 8.6 2.9 0.0 0.0 45.7 1.447
F 32 43.8 37.5 6.3 12.5 0.0 0.0 56.2 0.333
Total 98 52.0 31.6 11.2 5.0 0.0 0.0 47.8 0.694
Iceland M 1830 9 44.4 22.2 0.0 11.1 22.2 0.0 55.6
F 15 33.3 40.0 13.3 13.3 0.0 0.0 66.7 1.600
M30615 26.7 13.3 26.7 6.7 26.7 0.0 73.3 2.105
F 43 25.6 39.5 20.9 14.0 0.0 0.0 74.4 0.333
Total 82 29.3 32.9 18.3 12.2 7.3 0.0 70.7 1.353
Greenland Eastern
Early (EE)
M1830 2 0.0 50.0 50.0 0.0 0.0 0.0 100.0
F 5 0.0 40.0 40.0 20.0 0.0 0.0 100.0 NA
M30620 5.0 40.0 25.0 15.0 15.0 0.0 95.0 1.210
F 7 0.0 14.3 0.0 28.6 28.6 28.6 100.0 NA
Total 34 2.9 35.3 23.5 17.6 14.7 5.9 97.0 2.235
Greenland Eastern
Middle Late (EML)
M1830 1 0.0 0.0 100.0 0.0 0.0 0.0 100.0
F 10 40.0 40.0 10.0 10.0 0.0 0.0 60.0 NA
M30610 0.0 20.0 40.0 30.0 10.0 0.0 100.0 7.410*
F 17 17.6 41.2 29.4 0.0 11.8 0.0 82.4 1.266
Total 38 18.4 34.2 28.9 10.5 7.9 0.0 81.5 1.553
Greenland Western
Settlement (West)
M1830 2 0.0 100.0 0.0 0.0 0.0 0.0 100.0
F 10 30.0 50.0 10.0 0.0 10.0 0.0 70.0 NA
M3066 33.3 0.0 16.7 33.3 0.0 16.7 66.7 1.009
F 19 42.1 21.1 15.8 10.5 10.5 0.0 57.9 0.862
Total 37 35.1 29.7 13.5 10.8 8.1 2.7 64.8 1.351
EE: Thjodhilds Church.
EML: Gardar, Herjolfnes, Benedictine Convent.
West: Sandnes, Anavik.
SCOTT ET AL.
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3
were tabulated from the CGT II database from 133 samples. The total
number tabulated equals 49,970, with the North Atlantic samples
bringing the total to over 50,000. Although there might be minor dier-
ences in how researchers score the lowest grades of mandibular torus,
the large number of samples and individuals smooth out issues associ-
ated with interobserver error.
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METHODS
Mandibular torus is a bony growth expressed on the internal aspect of
the mandible below the lower canine and extending back as far as the
second molar. Trait expression varies among individuals who exhibit
one continuous growth or have expression broken down into two or
more distinct lobes. Determining the degree of torus expression does
not lend itself to interval scale measurement as there are no consistent
landmarks. However, the bony ridges and lumpy nodules that make up
the torus vary considerably in size, both in terms of linear length along
and projection away from the body of the mandible (Hassett, 2006). To
accommodate this variation, a ranked scale was developed that
includes grade 0 (absence) and grades 1 through 5 (increasingly pro-
nounced degrees of expression). When a mandible lacks a torus alto-
gether, this is determined through a combination of visual examination
and palpation. When there are no visible signs of torus and no slight
bony projection detectable by touch, the individual is scored as grade
0. A rank of 1 is assigned to a torus that cannot be visibly identied
but is evident by palpation. Grades 2 and above are all visually observ-
able and range from slight to pronounced protuberances (Figure 1).
4
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RESULTS
4.1
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Torus expression by age and sex
Table 1 shows the class frequency distributions for mandibular torus in
the six Scandinavian samples broken down by two adult age categories
and sex. Although age may be implicated in torus development, there
is no signicant dierence between young adults and older adults in
any sample. Torus was so rare in Vikings that a test of sex dierence
was not possible. For the remaining samples, four of ve show no sig-
nicant dierence between males and females. There was a signicant
dierence for the Eastern Middle Late sample but small sample sizes
may be implicated in this nding. At least for the samples in this study,
age and sex dierences are minimal or nonexistent.
4.2
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Geographic variation
While the Scandinavian samples exhibit no patterned dierences in
age and sex, they show pronounced temporal and geographic variation.
In the Viking age sample, mandibular torus is extremely rare. A few
jaws exhibit palpable tori but only one shows a small grade 2 form.
Over 90% of this sample fails to show any torus whatsoever and mean
trait expression is 0.109. The closest sample to the Vikings is medieval
Norwegians. For this group, about half (47.8%) of the sample exhibits
some form of torus with palpable expressions the most common
(31.6%). Mean trait expression is 0.694. The Icelanders and Green-
landers dier dramatically from the Vikings and Norwegians. The most
pronounced tori are found in the Eastern Early sample, which has a
total frequency of 97% and a mean trait score of 2.235. These values
are signicantly higher than those for Icelanders (70.7%; mts 51.353)
FIGURE 2 Class frequency distributions for mandibular torus in
the Greenlandic Norse, along with Vikings and medieval Norwegians
and Icelanders
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SCOTT ET AL.
and the two medieval Greenlandic samples (81.5 and 64.8%;
mts 51.553 and 1.351). This dramatic dierence is illustrated in Figure
2 that shows the distribution of torus expression in the two European
samples and the four North Atlantic samples.
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DISCUSSION
The Greenlandic Norse were exposed to an inhospitable climate
where wood was scarce and agriculture impossible due to short
growing seasons and the presence of permafrost. During the 500
year Norse occupation of Greenland, expression of mandibular torus
was at a maximum in the settlement period population (see Table 1
and Figure 2). It is dicult to determine the extent to which environ-
mental factors in Greenland contributed to this pattern because the
settlement period population came directly from Iceland. Although
we examined medieval Icelanders, we do not know how settlement
period populations from Iceland exhibited mandibular torus. Medie-
val Greenlanders show dramatic torus frequencies and expressions
consistent with observations of medieval Icelanders, but these are
less pronounced than what we see in the earliest colonizers of
Greenland. All three Greenlandic samples and the Icelanders exhibit
more mandibular torus than related populations from Denmark and
Norway. Given the presumably similar genetic backgrounds of Scan-
dinavian populations in Europe and the Norse colonists in the North
Atlantic, it seems that environmental pressures trump genetic back-
ground in determining mandibular torus expression in these
TABLE 2 Mean frequencies of mandibular torus for 15 regional groups
Regional group kMean % S.D. 95% condence limits References
Greenland and Iceland 11 0.512 0.2036 0.3750.649 (Axelsson & Hedegård, 1981; Drenann, 1937; Fischer-Møller,
1942; Igarashi, Ohzeki, Uesu, Nakabayashi, & Kanazawa, 2008;
Oschinsky, 1964; Steensen, 1969)
Northern Europe 15 0.177 0.1418 0.0980.255 (Alvesalo & Kari, 1972; Axelsson & Hedegård, 1981; Drenann,
1937, Furst & Hansen, 1915; Haugen, 1992; Howells, 1941; Kolas
et al., 1953; McLoughlin, 1950; Mellquist & Sandberg, 1939;
Oschinsky, 1964; Schreiner, 1935; Sognnaes, 1954) (CGT 6)
Southern Europe 10 0.147 0.1633 0.0300.264 (Cunha, 1994; Czarnetzki, 1975; Galera, Garralda, Casas, Cleuve-
not, & Rocha, 1995; Hrdlička, 1940; Reichart, Neuhaus, &
Sookasem, 1988; Rouas & Midy, 1997; Witkop & Barros, 1963)
North Africa and
Middle East
17 0.030 0.0635 0.0030.062 (Irish, 1993; Khaki, 2000; Salem, Holm, Fattah, Basset, & Nasser,
1987; Sawair, Shayyab, Al-Rababah, & Saku, 2009) (CGT 1)
South Asia 8 0.163 0.1277 0.0560.270 (Kaul & Anand, 1979; Ohno, Sakai, & Mizutani, 1988; Shah,
Sanghavi, Chawda, & Shah, 1992; Zoubov, 1973) (CGT 1)
Sub-Saharan Africa 27 0.039 0.0692 0.0120.067 (Adeyemo, Emeka, Taiwo, & Adeyemi, 2009; Agbaje, Arowojolu,Kolude,
& Lawoyin, 2005; Bruce, Ndanu, & Addo, 2004; de Villiers, 1968; Dosum,
Arotiba, & Ogunyinka, 1998; Drenann, 1937; Ihunwo & Phukubye, 2006;
Irish & Konigsberg, 2007; Rightmire, 1972; Shaw, 1931) (CGT 2)
North Asia 56 0.408 0.1894 0.3570.458 (Akabori, 1939; Dodo, 1974; Dodo & Ishida, 1987; Djurić-Srejić&
Nikolić, 1995; Hrdlička, 1940; Igarashi, in press; Igarashi et al., 2008;
Miyashita, 1935; Ohno, Sakai, & Mizutani, 1988; Pechenkina &
Benfer, 2002; Rouas & Midy, 1997; Sakai, 1954; Sugihara et al.,
2003; Tamaki, Marzola, & Tamaki, 1970; Zoubov, 1973) (CGT 29)
Southeast Asia 31 0.097 0.0989 0.0610.134 (Hashim, Haidar, & Kalsom, 1983; Jainkittivong, Apinhasmit, &
Swasdison, 2007; Kerdpon & Sirirungrojying, 1999; Nair, Samar-
anayake, Philipsen, & Itthagarun, 1996; Reichart et al. 1988; Van
den Broek, 1941; Zoubov, 1973) (CGT 24)
Australia-Melanesia 31 0.018 0.0344 0.0060.031 (Campbell & 1925; Fenner, 1939; Hrdlička, 1940) (CGT 27)
Polynesia and
Micronesia
15 0.030 0.0492 0.0020.057 (Turner & Scott, 1977; Witkop & Barros, 1963) (CGT 12)
Circumpolar
(Eskimo-Aleuts)
38 0.596 0.1825 0.5360.656 (Dodo & Ishida, 1987; Furst & Hansen, 1915; Hrdlička, 1940; Jarvis
& Gorlin, 1972; Jorgensen, 1953; Mayhall, 1970; Mayhall, Dahlberg,
& Owen, 1970; Mayhall & Mayhall, 1971; Moorrees, 1957;
Moorrees et al., 1952; Oschinsky, 1964; Ossenberg, 1978; Russell &
Huxley, 1899; Schreiner, 1935; Scott, 1991; Steensen, 1969; 85)
Native North America
(North)
14 0.290 0.2000 0.1740.405 (Cybulski, 1975; Ossenberg, 1978) (CGT 3)
Native North America
(South)
31 0.233 0.1882 0.1640.302 (Birkby, 1973; Blakely, 1973; Buikstra, 1972; El-Najja, 1974;
Hooton, 1918; Hooton, 1930; Hrdlička, 1940; Ossenberg, 1978;
Sublett, 1970; Wiltschke-Schrotta, 1988) (CGT 9)
Mesoamerica 13 0.053 0.0854 0.0010.104 (Escobar, Conneally, & Lopez, 1977) (CGT 10)
South America 18 0.053 0.0592 0.0240.083 (Balaez, Diaz, & Perez, 1983; Bernaba, 1977; Hrdlička, 1940;
Sawyer et al., 1979; Yaacob, Tirmzi, & Ismail, 1983; 85) (CGT 9)
World total 335 0.224 0.2425 Literature (202); CGT (133)
SCOTT ET AL.
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5
colonizing populations. To evaluate this question further, these six
Scandinavian samples are viewed in the context of torus expression
around the world.
5.1
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World variation
The 335 samples tabulated for total mandibular torus frequencies were
broken down into 15 major geographic areas (see Table 2). The rst
group, representing the Norse colonists of Greenland and Iceland, does
not include the samples reported in this study. Those were independ-
ent observations provided by other researchers. Western Eurasia is
broken down into four regions, including Northern and Southern
Europe, North Africa-Middle East, and South Asia. Africa has been less
intensively studied for torus than other regions so there is only a single
Sub-Saharan Africa category. Asia and the Pacic are more complex.
Asia is divided into North Asia and Southeast Asia. The Pacicisbro-
ken down into Australia-Melanesia and Polynesia-Micronesia. Over a
third of the world samples come from the Americas which are divided
into ve regions: Circumpolar, North America (North), North America
(South), Mesoamerica, and South America.
In terms of percentages, the geographic pattern of mandibular
torus variation is clear if regions are broken down into high (40%1),
moderate (2039%), low (1019%), and very low frequency (<10%)
groupings. Not surprisingly the high frequency group is headed by Cir-
cumpolar populations (Eskimo-Aleuts) with a mean frequency of
59.6%. Greenland and Iceland have the next highest average frequency
(51.2%), followed by North Asians (40.8%). The high frequencies in Cir-
cumpolar and North Asian populations likely reect genetic relation-
ships to some extent. The same cannot be said for Greenland and
Iceland where convergence rather than similar genetic backgrounds is
indicated. Only two regions fall in the moderate frequency category:
American Indians in the northern reaches of North America and those
found at lower latitudes as far south as the U.S.-Mexican border. Popu-
lations in the northern and southern parts of Europe, along with Asiatic
Indians, fall in the low frequency grouping. Almost half of all world
samples fall in the very low frequency group. Southeast Asia is close to
10% (i.e., 9.7%) but the remaining six groups are at or below 5%. Fre-
quencies are very low in Sub-Saharan Africans along with North
Africans-Middle Easterners. The worldslowestfrequenciesareinthe
Pacic, especially Australia and Melanesia, although Polynesia and
Micronesia are not far behind. In marked contrast to their neighbors to
the north, American Indians in Mesoamerica and South America have
low mean torus frequencies that are exactly the same at 5.3%.
In addition to the broad regional characterizations, individual
sample frequencies were plotted on a world map to illustrate the
pattern of variation for mandibular torus. Figure 3 shows that man-
dibular torus is strongly correlated with latitude. High latitude popu-
lations of both Asian and European descent show the highest torus
frequencies in the world. Torus frequencies are markedly reduced in
populations approaching the equator. The clinal maps are basically
blank in Africa, Australia, the Pacic, Mesoamerica, and South Amer-
ica despite being represented by dozens of samples and thousands
of individuals. The contrast in the Americas is especially telling.
North American Indians dier to some extent from Mesoamerican
and South American Indians, but the distinction between these areas
for mandibular torus is far more dramatic than we see in genetic or
dental markers (cf., Cavalli-Sforza, Menozzi, & Piazza, 1994; Scott &
Turner, 1997).
The suggestion that mandibular torus development might be asso-
ciated with wear is without foundation for a very basic reason. North-
ern populations have no monopoly on tooth crown wear. Researchers
who have not worked with Eskimo-Aleut samples often assume they
show an extraordinarily high degree of wear, but this is not the case.
They show pronounced wear but no more than countless other groups
who live at or near the equator and rarely express mandibular torus (e.
g., Australian aboriginals). If bruxism impacts mandibular torus, occlusal
stress may play a small role in its development but only a small role.
What is it about northern latitudes that trigger unusually large tori?
Beyond stress, cold and a high protein diet are two major factors that
might be involved in torus formation. Until a test is devised to tease
out divergent proximate causes, we can only conclude that genetics
plays a small role but environmental agencies play the predominant
FIGURE 3 World map showing clinal variation in mandibular torus frequencies; the highest frequencies are shown as dark gold with the
lowest frequencies as light gold
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SCOTT ET AL.
role in the manifestation of frequent and pronounced mandibular tori
in northern populations from disparate genetic backgrounds.
ACKNOWLEDGMENTS
Remarkably, the late Christy G. Turner II collected more data on
mandibular torus than any other single individual but, to the authors
knowledge, he never did anything with these data. He published
extensively, but his eorts were devoted primarily to how tooth
crown and root morphology could be used to address anthropologi-
cal issues (e.g., peopling of New World and Pacic). Going through
his original data sheets allowed us to evaluate populations from geo-
graphic regions largely unknown for mandibular torus frequencies (e.
g., Australia, New Guinea, Mesoamerica). Although the picture that
emerged from a consideration of 202 sample frequencies taken from
the literature pointed strongly in the direction of latitudinal clines in
torus frequencies, the addition of 133 samples from the CGT collec-
tion solidied the point considerably, especially for equatorial
populations.
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... The prevalence of the three oral characteristics range from 0.4% to 66.5% for palatine torus (Loukas et al., 2013;MacInnis et al., 1998),mandibular torus frequencies range from 0.5% to 63.4% (Loukas et al., 2013;Sonnier et al., 1999), and palatal exostoses are reported at 30.0% to 40.53% (Larato, 1972;Nery, Corn, & Eisenstein, 1977) and buccal exostoses 0.9% to 56.0% (Antoniades et al., 1998;Jainkittivong & Langlais, 2000). Scott, Schomberg, Swenson, Adams, and Pilloud (2016) reports a worldwide distribution in archeological material of mandibular torus with the circumpolar and northern latitude populations having the highest frequencies (40+) and North African, Western Asia and Australia having some of the lowest frequencies (<10%). ...
... A number of clinical studies have found a correlation between high dental wear and the presence one or more oral tori (Al-Bayaty et al., 2001;Igarashi et al., 2008;Kerdpon & Kirirungrojying, 1999;Morrison & Tamini, 2013) Bertazzo-Silveria et al. (2019 systematic review (SR) of heavy dental wear studies found a positive correlation between abnormal tooth wear and tori, specifically mandibular torus. Others (eg, Scott et al., 2016) disagree that wear plays a significant role in tori development (mandibular torus specifically), rather other factors such as diet or climate may have a higher influence. Walker (1978) noted dental wear is not just a function of age but also of abrasiveness of the diet. ...
... A trait was considered present if there was a bony outgrowth greater than 2 mm from the jaw surface. Scott et al. (2016) notes the measurement of the mandibular torus expression does not lend itself easily to interval scale measurement due to lack of consistent landmarks. The bony ridges and nodules which make up the torus can vary considerably in size and projection (Hassett, 2006). ...
Article
Full-text available
Objective This study evaluates the correlations amongst mandibular torus, palatine torus, oral exostoses to dental wear/loss and temporomandibular damage. Methods The sample consists of 504 skulls from the Hamann‐Todd Osteological Collection; 223 African American and 281 European Americans aged between 30 and 80 years. The sample was analyzed using Pearson's Chi‐square for significance of sex, age, ancestry, and wear as well as the interactions between the demographic variables and the presence of mandibular torus, palatine torus and oral exostoses. Results Wear was statistically significant by age and sex but not ancestry. The maxillary exostoses varied significantly by age, ancestry and wear but not sex. Mandibular torus frequencies varied significantly by wear, sex and ancestry. The palatine torus varied significantly across wear groups, sex and ancestry. Discussion The etiology of nonmetric oral cavity characteristics, mandibular torus, palatine torus and oral exostosis, is complex. The degree to which traits' presence and expression is the result of genetic and environmental interactions is not fully understood. More than age, sex or ancestry, the degree of dental wear and tooth loss influences the presence and expression of the oral cavity traits. The sample can be characterized as the presence of exostoses in higher frequencies in young African American males with little tooth loss. Males of both ancestral groups with heavy wear have higher frequencies of mandibular tori than females. The palatine torus is more common in edentulous European American females.
... TM frequency differs amongst popula-tions with a higher prevalence in the circumpolar regions and East Asian ancestries (Ossenberg, 1981;Pechenkina and Benfer, 2002;García-García et al., 2010). The prevalence is greatest in high-latitude populations (Scott et al., 2016) with a secular trend towards decreasing frequency due to biocultural factors (Haugen, 1992;Hosoi et al., 2003;Igarashi, 2016;Scott et al., 2016). While there is a demonstrable north-south cline in Asia, TM frequencies vary between modern and archaeological samples from East and Southeast Asia (Yaacob et al., 1983;Jainkittivong and Langlais, 2000;Pechenkina and Benfer, 2002;Choi et al., 2012). ...
... TM frequency differs amongst popula-tions with a higher prevalence in the circumpolar regions and East Asian ancestries (Ossenberg, 1981;Pechenkina and Benfer, 2002;García-García et al., 2010). The prevalence is greatest in high-latitude populations (Scott et al., 2016) with a secular trend towards decreasing frequency due to biocultural factors (Haugen, 1992;Hosoi et al., 2003;Igarashi, 2016;Scott et al., 2016). While there is a demonstrable north-south cline in Asia, TM frequencies vary between modern and archaeological samples from East and Southeast Asia (Yaacob et al., 1983;Jainkittivong and Langlais, 2000;Pechenkina and Benfer, 2002;Choi et al., 2012). ...
... The majority of the literature examines a single population from a specific time period, and the present study is unique in that the comparison of archaeological and modern skeletal populations with biological, cultural, and geographical affinities can contribute to a better understanding of the genetic and environmental influences. The aims of the present study are twofold: (i) to describe the pattern of mandibular tori in the Korean peninsula to corroborate or refute previous studies that report highprevalence statistics among East Asians, and (ii) to compare archaeological and modern skeletal samples from Korea to investigate the secular trend in TM as observed in Nordic (Scott et al., 1991(Scott et al., , 2016 and Japanese populations (Igarashi, 2016). ...
Article
Torus mandibularis (TM), or mandibular tori, are nodular, excessive bony growths along the lingual side of the lower jaw. TM occurs in varying frequencies in different populations with a higher prevalence in Asiatic and circumpolar groups. The tori are associated with mechanical stress from masticatory and paramasticatory behaviors, heredity, sex, age, and environmental factors. We investigated the presence, location, symmetry, and degree of TM frequencies in two skeletal populations with cultural, biological, and geographical affinities: 15th-18th-century Joseon Dynasty Koreans (n = 119) and 20th-21st-century modern Koreans (n = 77). TM frequency is significantly higher among modern Koreans (54.6%) than Joseon Dynasty individuals (13.3%) for females and males. There are no sex differences in TM prevalence in the archaeological and modern groups and an age-related trend in the TM frequency is not observed in either sample. Our results are consistent with the literature, which reports a higher frequency in Asiatic populations, but contrary to the general worldwide trend of decreasing prevalence over time. Modern Koreans have not undergone significant dietary changes since the Joseon Dynasty, and the quasicontinuous model with external factors may be responsible for the development of TM.
... Characters that reflect the dissipation of forces include pinched nasal bones and thickened tympanic plates. Perhaps tied to this in some way, Eskimo-Aleuts have the world's highest frequencies of palatine and mandibular tori (11,12). ...
... Obilježja koja odražavaju rasipanje sila uključuju izbočene nosne kosti i zadebljane timpanične ploče. Možda na neki način vezano za ovo, Eskimi Aleuti imaju najveću učestalost palatinalnog i mandibularnog torusa na svijetu (11,12). ...
Article
Full-text available
Abstract Objective of work: This paper provides an overview of crown and root morphology in Eskimo-Aleut populations of the American Arctic. For context, Eskimo-Aleut dental variation is compared to closely related American Indians and distantly related Europeans. Materials and methods: The characterization of dental trait frequency variation is based on observations made on approximately 10,000 dentitions scored by the late Christy G. Turner II and the author. Sixteen crown and five root traits were scored following the conventions outlined in the Arizona State University Dental Anthropology System. Results: Of the 21 dental traits considered, only three showed slight differences among Eskimo-Aleuts, American Indians, and Europeans (UM1 cusp 5, LM2 groove pattern, LM2 root number). For the remaining traits, there was typically a dramatic contrast between the two New World populations and Europeans. While generally similar, Eskimo-Aleuts and American Indians showed differences in UI1 winging, shoveling, and double shoveling, UM1 Carabelli trait, 2-cusped UM2, 3-rooted UM2, and especially 3-rooted LM1. Conclusion: The differences between the three groups are likely a product of genetic drift and founder effect although recent work on the EDAR V370A allele suggests some dental variables like shoveling and lower molar cusp number may indirectly reflect natural selection operating on other variables influenced by this allele.
... Although torus mandibularis has some hereditary component, it has a strong environmental component of variance. How the latter influences torus expression remains enigmatic (Scott, Schomberg, Swenson, Adams, & Pilloud, 2016). ...
Article
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In contrast to large-scale prehistoric migrations, associated with massive population shifts and changes in material culture, movements of small human groups or single individuals are barely visible but no less important. In publications of the 1960s–2000s, specificity of craniological, odontological, and metrical characteristics as well as stable isotope values of some individuals distinguishing the Late Mesolithic cemetery of Vasylivka II among other Mesolithic and Neolithic burial sites in the Dnipro River basin was explained by some gene flows. However, archaeologists could not develop these views since the original excavation report of 1953 and all grave goods from Vasylivka II were considered lost. Another old field document, where pendants of the pharyngeal teeth of fish, and the shells of spiral, probably Mediterranean, molluscs found there were mentioned, allowed the recent suggestion of the author of the current article that several individuals from the Danube Iron Gates region were interred in the cemetery. Previous arguments along with new evidence are presented here to develop this hypothesis. Re-found personal ornaments from one burial, the only available grave goods from Vasylivka II, are published here for the first time. The established regularity that most relatively young men and women from the graveyard have conditional “Danubian” δ ¹³ C values in the range from −20 to −21‰ assumes the mutual exchange of marriage partners born in the Iron Gates and the Dnipro Rapids. A waterborne route is discussed as a more probable mode of communication between these regions.
... Although he observed over 23,000 skeletons for these traits, he never published data for either variable. Scott, Schomberg, Swenson, Adams, and Pilloud (2016) incorporated the observations of Turner in a paper on the world variation of mandibular torus. The goal here is to provide a comparable survey of rocker jaw variation based on a sample of 12,733 individuals from around the world. ...
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Our goal is to describe the global distribution of the “rocker jaw” variant in human populations. Rocker jaw refers to mandibles that lack the antegonial notch, making them unstable on a flat surface. Data were collected by C.G. Turner II on 9,207 individuals from Asia, Europe, the Pacific, and the Americas, and by J.D. Irish on 3,526 individuals from North and South Africa. With a focus on Polynesia, where the trait is most common, frequencies are presented for subdivisions of Oceania, Australasia, Eurasia, the Americas, and Africa. While the rocker jaw is a Polynesian characteristic, the trait is found throughout the world. Within major geographic regions, there are interesting contrasts, for example, (a) the similarity of Jomon and Ainu and their difference from modern Japanese; (b) Aleuts and Northwest Coast Indians are similar and both are distinct from the Inuit and other Native Americans; and (c) North and Sub‐Saharan Africans show a regional difference that parallels genetic and dental distinctions. Skeletons in South America that exhibit the rocker jaw have been interpreted as Polynesian voyagers who ventured to the west coast of South America. The rarity of rocker jaw in South American natives supports this view. The rocker jaw can be attributed to the unique basicranium morphology and large upper facial height of Polynesians, which highlights the integrated growth of a functional module (i.e., mastication) of the craniofacial complex. The unusually high frequency of the trait in Polynesians is a product of both function and founder effect/genetic drift.
... At present, the etiology of tori is considered multifactorial. [10][11][12][13][14][15][16][17] In a recent review by Garcia, explained the formation of tori by Osteogenic-Periosteal Stretch Hypothesis, according to which the chin is prevented from undergoing excessive deformation due to the mental process. Humans lack the simian shelf but have instead developed an external chin to strengthen the weakest part of the mandible. ...
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Abstract Introduction: Oral tori are bony growths present in oral cavity and are not considered as pathological lesions. Torus mandibularis (TM) is usually present in lingual aspect of alveolar process in canine‑premolar region of mandible. The objective of the study is to determine the TM’ prevalence among outpatients attending tertiary care center and its relevance with parafunctional activities. Materials and Methods: The study was conducted in the out patients attending the hospital between December 2017 and May 2019. Fourteen thousand and two hundred and eight patients were screened for the presence of TM as per inclusion and exclusion criteria. The data were collected and subjected to the statistical analysis. Results: Out of 14,208 patients, 157 patients were presented with TM. The prevalence found to be 1.1%. Tori were more frequent in males than females. The most commonly observed type was bilateral solitary type. The association of TM with parafunctional activities and temperomandibular disorder was found to be significant. The higher frequency of TM was seen in the subjects residing at high altitudes. Discussion: The prevalence of TM in our study was found to be low. The study was undertaken to record the preliminary data regarding TM in this region and its association with parafunctional activity. Conclusion: We suggest performing thorough clinical examination and imaging to rule out underlying parafunctional activity, if TM is incidental finding.
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Objective: To determine the prevalence and pattern of presentation of mandibular and palatal tori in a Nigerian population. Method: A prospective observational study of mandibular and palatal tori among adolescents and adults subjects, attending the Oral and Maxillofacial Clinic of the Lagos University Teaching Hospital, Lagos, Nigeria, from January to December 2008 was conducted. Patients were examined by visual inspection and digital palpation for the presence of torus palatinus and torus mandibularis. Result: A total of 1004 subjects (424 males, 580females) were examined during the period of the study. The subjects were aged 15-90 years, (mean 32.7 ± 13.5 years). The prevalence of mandibular and/or palatal tori was 13.6% (136 of 1004). Of the 136 subjects, 24 had both mandibular and palatal tori, 48 had palatal tori only and 64 had mandibular tori only. Both the mandibular and palatine tori were commonly seen in female subjects. The most common location was the lingual surface of the mandible around canine-premolar region. The prevalence of mandibular torus was 8.8% and that of palatal torus was 7.2%. There was no statistically significant difference in the prevalence of mandibular tori in both sexes (P=0.48), whereas palatal tori were significantly commoner in females than males (P=0.00). Tori were commonly seen in the 3rd and 4th decades of life and were asymptomatic in 97% of subjects examined. Conclusion: The prevalence of tori in this study was higher than previously reported in Nigeria. Fourteen percent of those examined in the present study were found to have mandibular and/or palatal tori. Tori located on the lingual surface of the mandible around canine-premolar region were the most commonly seen tori in agreement with the previous study from Nigeria. Key words: Torus mandibularis; torus palatinus; Nigerians