Blankenship-Sefczek 2013.3 15 Brief communication: maxillary lateral incisor morphology and uncommon trait expression: a case study from prehistoric Paa-ko, New Mexico Erin C. Blankenship-Sefczek The Ohio State University, Columbus, OH 43210 ABSTRACT Prehistoric American Southwest exhib- its a high frequency of dental morphological varia- bility. This high variability may be the result of gene flow and subsequent genetic drift occurring in early periods (pre CE 900), though few studies report on dental variability in later periods. Mor- phological traits of the maxillary lateral incisors were analyzed from the Pueblo IV site of Paa-ko, New Mexico (CE 1300-1425) yielding high fre- quencies of four traits (shovel, double shovel, tu- berculum dentale, interruption groove) and un- common variants (barrel-shovel, triform, peg- shaped). Lateral incisor morphology is un- derrepresented in the literature but could be use- ful in determining population migration and affin- ity. Key words: Dental morphology, Upper Central Incisors, Discrete Dental Trait, Prehistory, Iberian Peninsula. Dental morphological traits, such as shoveling, tuberculum dentale, and interruption groove, re- flect population affinity and movement (Scott and Turner, 1997). Within the New World, the greatest dental morphological variability is found in the prehistoric American Southwest (Scott et al., 1983; Bailey-Schmidt, 1995; Scott and Turner, 1997; McClelland, 2003; Kuba, 2006).This high variabil- ity may be a result of migration and genetic drift, as introduction of new genes and subsequent pop- ulation isolation changes the expression of dental traits (LeBlanc et al., 2008).Mitochondrial DNA evidence from the prehistoric Southwest region suggests there was migration followed by popula- tion isolation in several areas, including the New Mexico Pueblo region (Malhi et al., 2003). Archae- ological evidence indicates migration into the Southwest from surrounding areas prior to the Pueblo IV period (CE 900-1500; Wilcox and Haas, 1994; LeBlanc, 1999; Malhi et al., 2003; LeBlanc et al., 2008) was likely a response to resource unpre- dictability caused by warm droughts and high seasonal resource stress (Dean, 1996; Benson et al., 2007). Unfortunately, few bioarchaeological stud- ies dealing with dental morphology in the later Pueblo IV period have been produced, limiting our ability to address this pre-contact period of population movement. This study interprets den- tal morphology of one tooth, the maxillary lateral incisor, from the site of Paa-ko, New Mexico in order to add to our understanding of Southwest dental morphological variability. Expressions of discrete dental traits are used to determine biological distance, population move- ment, and evolutionary trends (Turner et al., 1991; Scott and Turner, 1997; Irish and Guatelli- Steinberg, 2003). Maxillary lateral incisors, having the highest amount of variation in trait expression of all tooth types, is a key tooth for understanding genetic relationships and population comparisons (Turner et al., 1991; Bailey-Schmidt, 1995; Scott and Turner, 1997). Scott and Turner (1997:32) de- scribe categories of discrete trait variation in max- illary lateral incisors, including barrel-shovel, tri- form, and peg-shaped or conical incisors, which deviate from the more prevalent morphological forms of shovel and tuberculum dentale. Studies on dental morphology throughout the prehistoric American Southwest reveal higher var- iability of maxillary lateral incisor trait expression than any other location worldwide, particularly for shovel, barrel shovel, and full expression of tuberculum dentale and its variants (Sofaer et al. 1972; LeBot and Salmon 1977; Turner and Swin- dler 1978; Kieser and Preston 1981; Bailey- Correspondence to: Erin C. Blankenship-Sefczek The Ohio State University Department of Anthropology 4034 Smith Laboratory 174 W. 18th Ave. Columbus, OH 43210 (916) 752-2436 blankenship-sefczek.1@buckeyemail.osu.edu 16 Schmidt, 1995; Scott and Turner 1997; Burnett and Weets 2001; McClelland 2003; Bollini et al., 2008; LeBlanc et al., 2008). This study analyzes the fre- quency of maxillary lateral incisor traits from the prehistoric site of Paa-ko, New Mexico (CE 1300- 1425), adding to the literature on Pueblo IV South- west dental morphology. MATERIALS AND METHODS Skeletal remains analyzed for this study were recovered from Paa-ko, New Mexico between 1935 and 1937 as a joint venture of the Museum of New Mexico, the School of American Research, and the University of New Mexico, with funds allotted by the Works Progress Administration (Lambert, 1954). Paa-ko is located between Albuquerque and Santa Fe, New Mexico (Lambert, 1954). Occupied from CE 1300-1425, Paa-ko was established through population migration during the Pueblo IV period (Lambert 1954). This study uses a popu- lation count of 178 individuals, the majority of which are infants and children (9 years of age and younger). Taphonomic processes affecting the recovered dentition include severe postmortem damage and postmortem loss, both of which im- pacted observation and recording. For this study, only individuals with intact, fully erupted anterior maxillary dentition were used. Dental morpholo- gy was observed and recorded for 53 maxillary lateral incisors associated with 34 individuals; nine subadults (10-17 years), and 25 adults (18 + years). Males and females were not considered separately because of low correlation between sex bias and trait expression (Scott and Turner 1997; Kuba 2006). Dental morphology of 37 discrete and continu- ous dental traits were examined and scored fol- lowing the extensive sequencing of Turner et al’s (1991) ASUDAS to ensure accurate recognition. For this study variations of shovel, double shovel, interruption grove, and tuberculum dentale were the focus. In cases where dental attrition or tapho- nomic processes inhibited scoring of morphologi- cal traits, traits were recorded as missing data. RESULTS Fifty-three maxillary incisors from 34 individ- uals were examined. Table 1 shows trait frequen- cies. The most frequently expressed trait was shovel- ing, occurring in 26 individuals (79%, n=43 teeth). Of these individuals, 13 (38.2%, n=13 teeth) exhibit either shovel, or marked shovel (Turner et al. 1991). Barrel-shaped incisor was exhibited in one individual (2.9%, n=2 teeth). Double shoveling was exhibited in 12 individuals (35%, n=17 teeth). Interruption groove was expressed in 21 individu- als (61%, n=32 teeth). Tuberculum dentale was present in 22 individuals (64.7%, n=35 teeth). Thirteen of the individuals (55.8%, n=19 teeth) with a tuberculum dentale expressed either a weak cuspule with a free apex or a strong cusp with free apex, which are the highest ASUDAS grades (Turner et al 1991:16). One individual (2.9%, n=1 tooth) expressed a triform, bifurcated lateral incisor. This tooth exhibited a developed transverse ridge on the incisal surface originating from the tuberculum dentale dividing two fossae (Lee et al. 1988; Bailey-Schmidt 1995). Mesiodistal and labiolingual dimensions of this tooth were greatly expanded as a result of this morphological arrangement. Four individuals (11.7%, n=4 teeth) expressed a peg-shaped, or conical, lateral incisor. Eight individuals (23.5%, n=11 teeth) expressed some degree of all observed traits (shovel, double shovel, interruption groove, tuberculum dentale). Six individuals (17.6%, n=7 teeth) exhibit maxil- lary lateral incisor variants which are considered rare in expression (barrel-shovel, peg-incisor, tri- form; Scott and Turner, 1997). TABLE 1. Frequency of Lateral Incisor Trait Traits # of Individuals Scored and Percent Expressed n % Shovel 26 0.790 Full Shovel 8 0.235 Marked 5 0.147 Barrel 1 0.290 Double Shovel 12 0.350 Interruption Groove 21 0.610 Tuberculum dentale 22 0.647 Well-developed 13 0.382 Triform 1 0.029 Peg-shaped 4 0.117 17 DISCUSSION Paa-ko is a quintessential example of prehis- toric Southwest dental morphological variation. There is a high prevalence of all four maxillary lateral incisor traits analyzed (shovel, double shovel, tuberculum dentale, and interruption groove) and most correspond with previously re- ported Native American samples (Sofaer et al., 1972; Scott et al., 1983; Bailey-Schmidt, 1995; Scott and Turner, 1997; McClelland, 2003). Seventeen percent of the Paa-ko sample exhibits uncommon lateral incisor trait variants, barrel-shovel (Figure 1), triform (Figure 2), and peg-shape (Figure 3), a higher frequency than other reported prehistoric Southwest populations (Sofaer et al., 1972; Burnett and Weets, 2001; McClelland, 2003). An outline of specific migration patterns is beyond the scope of this paper because its focus remains on one population; however, a discussion is necessary to determine the high variability and rare trait expression within the maxillary lateral incisor of Paa-ko. Increased trait prevalence is most likely the result of gene flow into the South- west followed by period of population isolation (Malhi et al., 2003; LeBlanc et al., 2008). Migration into the region, including into the San Juan Basin (Benson et al., 2007) where Paa-ko is located, oc- curred prior to the Pueblo IV period. Lambert (1953) argues that Paa-ko was established by com- munities from the west. High frequencies of mor- phological variation and prevalence of uncommon traits may be reflective of the broad admixture resulting from eastern migration (Malhi et al., 2003).The Pueblo pattern of large site abandon- ment followed by isolated community aggregation (Fagan, 2000) likely resulted in short term genetic drift, and contributed to the higher prevalence of rare dental traits observed within Paa-ko. Adaptive significance can also influence the expression of certain dental traits, as functional demands impact tooth morphology (Hunter and Jernval, 1995). Shoveling and tuberculum dentale may be adapted to strengthen teeth by adding to structural durability with extra enamel (Dahlberg, 1963; Bailey-Schmidt, 1995).However, this expla- nation is less likely to be the case because traits Fig. 1. Barrel-shovel lateral incisors observed in burial 1971-82-122. Fig. 2.Triform variant of right lateral incisor ob- served in burial 1971-82-21. Fig. 3. Peg-incisor observed on left maxillary lat- eral incisor of burial 1971-82-96. 18 associated with advantageous adaptive changes would be seen in high prevalence throughout the region, not localized to Paa-ko. Additionally, an- terior teeth are not used in primary mastication. CONCLUSION Prehistoric Native American Southwest exhib- its high dental variability in the lateral incisors (Sofaer et al., 1972; Bailey-Schmidt, 1995; Scott and Turner, 1997; McClelland, 2003), especially at Paa- ko, New Mexico (CE 1300-1425). High prevalence of four discreet traits (shovel, double shovel, inter- ruption groove, and tuberculum dentale) and their morphological variants (barrel-shovel, peg- incisors, triform) were observed in Paa-ko, New Mexico. The high observed variability is likely the result of gene flow into the region followed by short term population isolation prior to the Pueblo IV period (CE 900-1500). Even though maxillary lateral incisor traits are good indicators of genetic relationships and population movement (Scott and Turner, 1997),they are underrepresented in the literature. This article provides an additional pre- historic Southwest population for future research on regional behaviors, migration, and population affinity. ACKNOWLEDGEMENTS Thanks go to the San Diego Museum of Man for the opportunity to conduct research on this collec- tion. To Tori D. Randall, thank you for your sup- port of this project. Thank you to G. Richard Scott, and Shara Bailey for aiding in the identification of the triform lateral incisor. Special thanks go to Debbie Guatelli-Steinberg for guidance and advice in analysis and writing. The author thanks the editor-in-chief Christopher W. Schmidt and anon- ymous reviewers for their critical advice on this work. LITERATURE CITED Bailey-Schmidt S. 1995. 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