2016 年 124 巻 2 号 p. 93-105
A complete deciduous dentition was excavated from the Mesolithic site of Damdama (8800– 8600 BC) in the Gangetic Plain of north India. The site yielded remains of 47 individuals, including one child specimen 3.0–3.5 years of age, in association with an aceramic, microlithic technology and a seminomadic foraging pattern. Because sub-adult dental remains from Mesolithic contexts are very rare in South Asia, this specimen yields critical insight into deciduous dental attributes, including: (i) tooth crown size and temporal trends in dental reduction; (ii) non-metric dental morphology and biological affinity; and (iii) dental pathology, physiological stress, and diet. Standardized methods were employed in each component of the analysis, and most comparative samples were analyzed by the author, reducing the potential for inter-observer variance in data collection.
This child specimen (DDM 5) has large mesiodistal and buccolingual crown dimensions and the largest summed tooth crown area in a comparative field of six prehistoric and three living Asian samples. In dental morphology, it exhibits simplified crown structure with few accessory cusps, ridges or wrinkles. This pattern parallels that of Damdama permanent teeth and is divergent from Hanihara’s East Asian (‘Mongoloid’) dental complex. It has closer affinity to the European (‘Caucasian’) dental complex as biodistance analysis of permanent teeth has suggested. The dentition of DDM 5 is free from most pathological lesions (abscess cavities, alveolar resorption, antemortem tooth loss, calculus, and caries), but exhibits ‘plane-form’ enamel hypoplasia of the canine teeth. Localized hypoplasia of primary canines (LHPC) indicates perinatal physiological stress and is an example of early developmental stress in association with early mortality, a model known as the Barker Hypothesis (or more generally, the developmental origins of health and disease hypothesis). The potential for deciduous dental remains to reveal important evidence bearing on biological adaptations and affinities of past populations is informative and promising.
This expression reflects the precocious and perceptive insights with which children often surprise parents and other adults. It is adopted here as a metaphor to illustrate the potential of an early Holocene child to inform us about the health status and biological variations in sub-adults in past populations. The significance of sub-adults in bioarchaeology research comes from the evidence they provide regarding adaptations and life stresses of infants and children in past populations (Saunders and Barrans, 1999; Sobolik, 2002; Lewis, 2007). Despite their potential utility, the value of subadults is often unappreciated. This report documents the dental remains of a 3.5 year old child specimen (DDM 5) from the early Holocene Mesolithic site of Damdama (Pratapgarh District, Uttar Pradesh, India). This evaluation of biological variables includes analyses of: (i) dental attrition— wear of the occlusal and interproximal surfaces; (ii) tooth size—crown length and breadth; (iii) non-metric traits of tooth crown morphology; and (iv) dental pathology. These attributes are then compared with existing dental data from prehistoric South Asia to achieve three goals:
An abridged timeline of prehistoric sites in South Asia that have yielded human skeletal samples is provided in Table 1, as a guide to the sites and skeletal series discussed below. The lessons to be learned from this early Holocene child have special significance for the bioarchaeology of India because sub-adults are rare in prehistoric South Asian mortuary samples. However, exceptions exist among Chalcolithic sites of the Deccan Plateau, at Inamgaon (Lukacs and Walimbe, 1986) and Nevasa (Mushrif-Tripathy and Walimbe, 2006), where sub-adults are more frequent than adults. No sub-adults were recovered from Mesolithic graves at the nearby site of Sarai Nahar Rai (Kennedy et al., 1986). Two children were recovered from Mahadaha (MDH 7 and MDH 20), though neither has yielded extensive dental or osteological data. Specimen MDH 7 is very incomplete, fragmentary and lacks dental remains (Kennedy et al., 1992). By contrast, specimen MDH 20 is represented by a complete skeleton and partial mandibular dentition of a 4–5 year old child (Lukacs and Hemphill, 1992: see fig. 13, p. 184). Unfortunately this specimen was unavailable for the study (lifted en bloc, on display in a showcase in Allahabad University, Museum of Archaeology). In the greater Indus Valley of Pakistan, one perinatal skeleton was excavated in 1988 from cemetery R-37 at Harappa and sub-adults were absent from Neolithic (MR 3) levels at Mehrgarh (Baluchistan Province, Pakistan). Deciduous teeth recovered from the early Chalcolithic (MR 2) graveyard at Mehrgarh allowed preliminary descriptions of crown morphology and odontometrics (Lukacs and Hemphill, 1991). By contrast, Late Chalcolithic levels in MR 1 excavation area yielded 30 neonatal and perinatal specimens in small mud-brick tombs. The skeletons of these specimens are incomplete and fragmented; however, 11 specimens retained 47 deciduous teeth that have been examined and measured (Lukacs, 1983).
My own interest in the study of deciduous teeth began with the analysis of human remains from the early farming village of Inamgaon (1400–700 BC) in western Maharashtra (central India). Approximately 85% of the skeletons excavated at Inamgaon were sub-adult specimens whose preservation was facilitated by interment in single or twin urn burials (Lukacs and Walimbe, 1986; Dhavalikar, 1988; Dhavalikar et al., 1988). Data from the large sample of deciduous teeth from Inamgaon have been used to answer questions regarding: (i) deciduous tooth size in prehistoric and living South Asians (Lukacs, 1981; Lukacs et al., 1983); (ii) biological affinity and population history—using non-metric attributes of dental morphology (Lukacs and Walimbe, 1984); (iii) physiological stress and mode of subsistence— using developmental enamel defects (Lukacs and Walimbe, 1998; Lukacs et al., 2001); and (iv) dental pathology (caries prevalence) and tooth size across the subsistence transition from farming to foraging (Lukacs and Walimbe, 2000, 2005; Lukacs, 2007).
Comprehensive works on dental anthropology do not typically include data on deciduous dental morphology, pathology, or crown dimensions (Hillson, 1996; Kieser, 1990; Scott and Turner, 1997). However, significant contributions have been made to the analysis of deciduous dental variation, including odontometric variation in Liberians (Moss and Chase, 1966), Australian aboriginals (Margetts and Brown, 1978; Townsend, 1980), and native Americans (Sciulli, 2001) as well as living Japanese (Kitagawa et al., 2002), and prehistoric Jomon and Yayoi (Matsumura, 1991). Evolutionary changes in deciduous tooth size of Near Eastern populations were documented by Smith (1978). Deciduous dental asymmetry has been studied in Dominican mulatto and south Australian children (Townsend and Garcia-Godoy, 1984; Townsend and Farmer, 1998). Correlation and discrimination of deciduous dental metrics and morphology have focused on European, American, and global samples (Harris and Lease, 2005; Lease and Sciulli, 2005; Edgar and Lease, 2007). Fused and double primary teeth have been reported in archaeological samples and living populations in India and elsewhere (Tasa, 1998; Tasa and Lukacs, 2001; Smith and Wojcinski, 2011). Non-metric variations of the deciduous tooth crown have been documented in medieval and modern Danes by Jørgensen (1956), in Japanese and Ainu by Hanihara (1961, 1966) and Kitagawa (Kitagawa et al., 1995, 2002; Kitagawa, 2000), in native North Americans by Sciulli (1998) and in early hominids and South African Blacks by Grine (1984, 1986). Variation in deciduous dental morphology has been used to detect biological siblings in mortuary samples (Paul and Stojanowski, 2015). Unique attributes of deciduous dental morphology, such as the talon cusp, have been noted in prehistoric and living Southeast Asians (Lukacs and Kuswandari, 2009; Halcrow and Tayles, 2010), in an archaeological series from Argentina (Pomeroy, 2009), and in medieval Portugal (Silva and Subtil, 2009). Pathological lesions of the deciduous teeth reveal class differences in oral health in early modern Japan (Oyamada et al., 2008). Deciduous enamel hypoplasias, regarded as evidence of disruptions in growth and development, have been reported for Edo Japanese (Yamamoto, 1989) and associated with climate and subsistence change in skeletal series from Mendes, Egypt (Lovell and Whyte, 1999) and Chalcolithic Inamgaon, India (Lukacs and Walimbe, 1998; Lukacs et al., 2001).
The prehistoric site of Damdama was discovered in 1978 and excavated in the 1980s by the Department of Ancient History, Culture and Archaeology under the direction of J.N. Pal (Varma et al., 1985; Pal, 1994). Excavations yielded evidence of an early Holocene (8800–8600 BP) settlement of semi-nomadic foragers with an aceramic, microlithic technology (Pal, 1994; Lukacs et al., 1996). The adult skeletons from Damdama yield many insights regarding adaptations and lifeways among Mesolithic hunter-foragers of north India (Lukacs, 2016). They exhibit few pathological lesions, suggesting nutritional and infectious diseases were uncommon, as were traumatic injuries. Skeletal indicators of activity (entheses and anomalies) suggest habitual behaviors involved stresses from locomotion and posture, and from forceful use of the upper limb and forearm (Lukacs, 2016). The Damdaman adults have structurally robust jaws, large teeth (total crown area = 1383 mm2), and were tall statured (male 178.7 cm, female 167.8 cm) (Lukacs and Pal, 1993, 2016).
Although numerous adults were excavated at Damdama, the only sub-adult with dental remains is specimen DDM 5 (Pal, 1988, 1992, 2002; Lukacs and Pal, 2016). The child’s skeleton is represented exclusively by cranial bones including flat bones of the neurocranium and the mandible. The frontal, right and left parietal, squamous portion of the occipital and a small segment of the right and left temporal are present. While postmortem compression toward the mid-sagittal plane has distorted their shape, the maxilla and mandible are less affected by post-burial diagenesis. The maxilla is broken along the mid-line. The left maxilla has slightly shifted in an anterior and medial direction. Alveolar bone is missing from the labial and buccal aspects of the maxilla, yet the lingual (palatal) bone is preserved. Exfoliation of alveolar bone reveals developing permanent tooth germs; right and left lateral incisors (I2) in palatal view, right and left central incisors (I1) in anterior view, and right and left canines (C) in superior view. Viewing the maxilla from the posterior, the germs of right and left first permanent molar teeth are visible, and were extracted for analysis. As in the maxilla, the mandible lacks most alveolar bone from the labial, lateral, and buccal surfaces; however, bone of the medial alveolar surface is well preserved. The left corpus is present from the mandibular symphysis to the anterior wall of the crypt of the left first permanent molar. The right corpus is similarly preserved, but includes a portion of the right ascending ramus and the right first permanent molar is present in the crypt. The mandibular foramen is visible on the medial aspect of the ascending ramus and the mylohyoid line is visible though faintly marked.
The full complement of 20 deciduous teeth and four first permanent molar teeth are well preserved. The deciduous teeth are all erupted and in full functional occlusion, the permanent first molars are unerupted and retained in their developmental crypts (Figure 1). Several deciduous teeth have had small chips of enamel removed from the crown postmortem. This damage is localized and is evident in the mesiolingual aspect of the incisal edge of the maxillary left central incisor (ldi1), the labial surface near the cementoenamel junction of the maxillary right lateral incisor (rdi2), and the distal and labial aspect of the cusp apex of the maxillary left canine (ldc). Mandibular incisors have lost small flecks of enamel from the labial surface along the cementoenamel junction.
Occlusal views of DDM 5; maxilla (left), mandible (right). Arrows indicate scale: MD diameter of left dm2 = 9.9 mm; MD diameter of left dm2 = 11.0 mm. Note: Large size of unerupted permanent left first upper and lower molars.
Standard manuals of sub-adult anatomy and osteology were used to identify and inventory the skeletal elements of specimen DDM 5 (Scheuer and Black, 2000). Age determination employed a series of standards on dental development, including tooth crown formation (Moorrees et al., 1963a, b; Haavikko, 1970; Gustafson and Koch, 1974) and timing of tooth eruption (Ubelaker, 1978; Ferembach et al., 1980). The London Atlas of Human Tooth Development and Eruption (AlQahtani et al., 2010) was consulted to confirm age at death estimates. Age estimation in prehistoric, non-Western sub-adults are constrained by the absence of dental eruption and calcification standards from ethnically appropriate reference populations (Halcrow et al., 2007). Furthermore, living groups with high masticatory stress (Australian aborigines, for example) may have accelerated dental development in comparison with Westernized groups whose diet is highly processed (Brown, 1978). This makes the use of dental development standards of modern populations inappropriate for age assessment of pre-agricultural hunter-foragers. Occlusal surface wear was graded using standards described by Smith (1984) for permanent teeth. Maximum dimensions of tooth crown length (mesiodistal) and breadth (buccolingual) were measured following guidelines recommended for permanent teeth by Moorrees (1957) as summarized by Kieser (1990). Classification of variation in expression of non-metric morphological traits employed a variety of methods and standards depending on the trait analyzed. Methods for grading each of the 22 morphological traits observed in deciduous teeth are summarized by Lukacs and Kuswandari (2013: 469–476), which relies heavily on the pioneering research by Hanihara (1961, 1963, 1966, 1968).
The analysis of specimen DDM 5 is subdivided into five sections that address estimation of age at death, tooth wear, odontometry, morphology, and pathology.
All the deciduous teeth were fully erupted and in functional occlusion at time of death, which indicates an age of more than 2.5–3.0 years (Ubelaker, 1978; Ferembach et al., 1980; AlQahtani et al., 2010). Occlusal wear is slight throughout the deciduous dentition, with enamel polish visible on the cusps of deciduous second molar teeth. The low level of tooth wear suggests the deciduous teeth have not been functional for a long period of time. Maxillary and mandibular permanent first molar crowns are unerupted and incompletely calcified, though crown completion is imminent. Since the London Atlas is based in part on calcification and emergence data from Moorrees and colleagues (1963a, b) it yields an age estimate for DDM 5 of between 3.5 and 4.0 years of age. Calcification of permanent molar teeth progresses at different rates in males and females and exhibits a range of variation in timing by jaw (Gustafson and Koch, 1974). Maxillary first permanent molars complete crown calcification between 2.5 and 4.5 years, with a mode of 3.0 years. Mandibular isomers attain crown completion at between 2.5 and 4.0 years, with a mode of 2.7 years. Another study suggests little difference the median age at which the first permanent molar crown completes formation, ca. 3.5 years, with little difference by sex or by jaw (Haavikko, 1970). These independent indicators suggest the approximate age at death of DDM 5 is between 3 and 4 years. The absence of ethnically relevant standards and the possibility of accelerated development in a prehistoric non-Western group with high masticatory stress makes the younger part of this range (3.0–3.5 years) more likely. The sex of DDM 5 is indeterminate and hence unknown. Attribution of sex in sub-adults is typically not possible because secondary sex characteristics are not expressed in the skeleton until adolescence and skeletal evidence in this individual is limited to poorly preserved cranial bones (Scheuer and Black, 2004).
Because all teeth were preserved in anatomical contact with each other, the extent of interproximal wear was assessed by direct observation of the amount of interdental contact. Slight interproximal wear is present in both maxillary and mandibular incisors, though to a greater degree in the latter. No interproximal wear was observed from the mesial aspect of canine to the second molar in both jaws. The minor amount of interproximal wear is consistent with the sequence of deciduous dental eruption and implies brief functional use.
The degree of occlusal wear in DDM 5 is presented in Table 2 (see also Figure 1). Degree of wear varies by tooth class, decreasing progressively from di1 through dm2 in both the maxillary and mandibular dental arcades, which is primarily dependent on the timing of dental eruption. Time of eruption is linked to the length of time the occlusal surface functions in masticating food and in tooth–tooth contact. Upper and lower incisor teeth exhibit traces of slight dentine exposure along the incisal edge. Canine and molar teeth show only enamel polish and no dentine exposure. Given the high degree of wear visible in the permanent teeth of some mature adults at Damdama (including pulp exposure and tooth dislocation) the degree of wear in DDM 5 is consistent with a fully erupted dentition that has been functional for a short period of time. No unique or idiosyncratic patterns of tooth wear as might be associated with habitual use in specialized modes of ingestion or occupational non-dietary activities were observed.
An odontometric assessment of DDM 5 is included here because of the specimen’s antiquity and the insights it gives into trends in deciduous tooth size in Indian prehistory. Mesiodistal and buccolingual dimensions and crown areas of the deciduous teeth of DDM 5 are provided in the left half of Table 3. Mean crown areas (CAs) of comparative samples are given in the right half of the table. Summary variables— maxillary, mandibular and total CAs—cannot be compared statistically, yet DDM 5 has the largest values for all three variables. Statistical comparison of CAs used a one-sample Student’s t-test (GraphPad software; Thomas, 1976; Zar, 1999), to compare a single variate (right side CA of DDM 5) to the sample mean CA for which the standard deviation and sample size are known. Table 3 reveals fewer significant differences between DDM 5 and earlier samples such as Neolithic (MR 3) and Chalcolithic (MR 2) Mehrgarh. By contrast, later samples more frequently display smaller mean CAs than DDM 5. The single living South Asian sample is from Gujarat and all mean CAs are highly significantly smaller than DDM 5 (P = 0.0001). The Malay sample from Java could not be statistically evaluated because they were derived from the product of mean MD and mean BL values, and therefore lack measures of dispersion (standard deviation or standard error of the mean). Nevertheless, Malay CAs are similar to values for the Hindu sample from Gujarat and the corresponding CAs of DDM 5 would likely be significantly larger than the CAs of Javanese Malay.
Abbreviations: MD, mesiodistal; BL, buccolingual; CA, crown area; d, deciduous.
Comparison groups: MR 3, Neolithic Merhgarh; MR 2, Chalcolithic Mehrgarh; INM, Inamgaon; TMG, Timargarha; Guj, Gujarati Hindus; Malay, Javanese Malay.
Comparison of CAs used a one-sample Student’s t-test (GraphPad software; Thomas, 1976; Zar, 1999), to compare a single variate (right side CA of DDM 5) to the sample mean CA for which standard deviation and sample size are known. Significant differences are marked with an asterisk (*P < 0.05), all Gujarati values are highly significant (P < 0.0001).
Graphic comparison of DDM 5 tooth size is provided in Figure 2. CAs of the DDM deciduous dentition are contrasted with mean CAs of four prehistoric and two living groups. Sites are arranged along the x-axis in chronological order from DDM on the left to the two living samples, on the right: Indians from Gujarat and ethnic Malay from Java, Indonesia. The data for Damdama are for the one sub-adult DDM 5, data for other groups represent the sum of mean CAs for individual teeth in the upper and lower jaws. For this reason standard deviations (error bars) cannot be included to show range of variation in these variables. The pattern of variation in Figure 2 is familiar because it is consistent with CA data presented elsewhere for the permanent dentition from these sites (Lukacs and Walimbe, 2005; Lukacs and Pal, 1993, 2016). Maxillary CAs are greater than mandibular CAs and total CA tends to decline through time from DDM to the living samples.
A final comparison of total deciduous tooth crown areas places DDM 5 in context with prehistoric and living South and East Asian samples (Figure 3). Total crown area (in mm2; y-axis) is plotted against time, in thousands of years (x-axis; see Table 4 for dates and references). Three East Asian samples are included in this plot: two prehistoric— Neolithic Jomon (4000–2300 BP) and Yayoi (2300–1700 BP); and one modern—Japanese (from Kitagawa et al., 2002). Note that the three living groups (Javanese Malay, Gujarati, and modern Japanese) have the smallest summed tooth crown areas, and DDM 5, the earliest specimen in the plot, has the largest tooth size. The trend in deciduous tooth size reduction is indicated by a negative slope of the regression line among these Asian samples. This amounts to a decline in deciduous tooth size of approximately 5.5 mm2 (or approximately 1.1%) per millennium, a result that parallels the rate of post-Pleistocene decrease in size of permanent teeth (ca. 1%) documented in different regional samples throughout the world (Brace et al., 1987). As in the permanent teeth, the rate of reduction in deciduous tooth size accelerates in post-Pleistocene populations of the Near East and is similar to the rate of reduction documented here for South Asia (Smith, 1978).
Expression of non-metric traits of the deciduous teeth of DDM 5 are presented in Table 5. The crown morphology of this specimen can be described as consistent with the expression of non-metric traits in the permanent teeth from Damdama (Lukacs and Pal, 2013, 2016). In essence, crown morphology is structurally simple, with anterior teeth lacking marginal ridging and with weak forms of shovel-shape and tuberculum dentale. Post-canine teeth are not complex in form either. They lack, or exhibit small-sized, accessory cusps in maxillary and mandibular molars. It is challenging to compare the degree of expression of non-metric dental traits in one individual with trait frequencies for comparative groups. However, the expression of each trait in DDM 5 is compared with the frequency of that grade of expression in two deciduous dental samples one prehistoric (Chalcolithic Inamgaon, western India) and one living (Javanese Malay, Yogyakarta, Indonesia) in Table 5. All the comparative data were collected by the author using the same set of standards. For example, shovel shape in the upper lateral incisor (di2) is grade 2 in DDM 5, this grade of expression occurs in 19.2% (n = 26) of Inamgaon di2s and in 57.3% (n = 131) of Javanese Malay di2s. Likewise the paramolar tubercle (or parastyle) is absent from right and left upper first molar teeth of DDM 5 (r and ldm1), the trait is also absent from all Inamgaon dm1s, but is only absent from 56.1% (n = 148) Javanese Malay.
A second way of placing the dental morphology of DDM 5 is to compare it with the ‘Mongoloid’ dental complex of Hanihara (1966). This obsolete racial label refers to an association of deciduous non-metric dental traits that tend to occur with high frequency in East Asian and native North American populations (Japanese, Eskimo, and Pima), compared to the European dental trait complex (labeled ‘Caucasian’ by Hanihara, 1966). The East Asia (native American) complex has high frequencies of six traits: shovel shape in di1 and di2, and the protostylid, deflecting wrinkle, cusp 6 and cusp 7 in the lower dm2. By contrast, the European-derived, American White sample is characterized by very low frequencies of these traits. Two additional traits that show significant differences between these samples is the cusp of Carabelli, which is more frequent in Europeans and absent in East Asian (native Americans), and the deciduous canine breadth index, which is high in Europeans and low in East Asians/native Americans. Data for the East Asian/native American dental complex, DDM 5, and European-derived (American White) samples are plotted in Figure 4. The position of DDM 5 is clearly aligned with the European dental complex for most traits. However, in the deciduous canine breadth index (dc/di1 × 100) DDM 5 has a value 105.6 which is midway between American Whites and the Pima, a native American group. The biological affinities of DDM 5 to the European are consistent with findings derived from a more comprehensive multivariate statistical analysis of non-metric traits of the permanent teeth of the Damdama sample (Lukacs and Pal, 2013, 2016).
Dental morphology of DDM 5 relative to Hanihara’s (1966) ‘Mongoloid’ and ‘Caucasian’ dental complexes. Trait abbreviations: SS_di1, shovel shape of deciduous upper central incisor; SS_di2, shovel shape of deciduous upper lateral incisor; Proto_dm2, protostylid in deciduous lower second molar; DefWr_dm2, deflecting wrinkle in deciduous lower second molar; c6_dm2, cusp six in deciduous lower second molar; c7_dm2, cusp 7 in deciduous lower second molar; Cara_dm2, Carabelli’s cusp in upper second molar; dc/di1 Index, canine breadth index (mesiodistal length of the deciduous canine/mesiodistal length of the deciduous central incisor × 100). Note: right y-axis applies only to deciduous canine breadth index (dc/di1 × 100).
No evidence of dental abscess cavities, alveolar recession, antemortem tooth loss or caries was observed. The only pathological lesion present in DDM 5 is enamel hypoplasia of the primary canines. Enamel hypoplasia (EH) is expressed in different ways in both permanent and deciduous teeth. Linear enamel hypoplasia (LEH) is the most commonly observed and studied form of EH and more frequently affects permanent than deciduous teeth (Goodman and Rose, 1990). Other expressions of enamel hypoplasia include depressed areas of enamel known as ‘pit-patches’ (Goodman et al., 1992), cuspal enamel hypoplasia of molar teeth (Ogden, 2008), and LHPC (Skinner, 1986). Although LEH and pitpatch hypoplasia were observed in the permanent teeth of the Damdama skeletons, LHPC was observed in the only sub-adult with deciduous teeth (DDM 5). Following a pattern of expression commonly observed in clinical studies of the trait, the maxillary canines were unaffected while both mandibular canines exhibited this ‘plane-form’ type of EH (Skinner and Hung, 1986, 1989; Hillson and Bond, 1997). The labial surface of mandibular right and left primary canines were affected though the defects exhibited significant asymmetry in trait expression (Figure 5); the number, size, and location of defects were different in antimeres. The lower left canine has a single small defect located on the distal aspect of the labial face somewhat below mid-crown. The area affected is small (<1.0 mm in diameter) and appears hour-glass shaped; it is restricted or pinched at mid-height. The right mandibular canine exhibits a double defect that covers a significantly larger area and is located on the mesial aspect of the labial surface. The superior/mesial defect is much larger than the lower defect, which is inferior and posterior to it. The two defects are separated by a faint but distinct narrow band of enamel that extends anteriorly and inferiorly. The height of the two defects is approximately 3.0 mm and occupies the middle third of the mesiolabial face of the crown. Various sources estimate that approximately 30–33% of the deciduous mandibular canine is calcified at birth (Moorrees et al., 1963a; Lunt and Law, 1974; Schour and Massler’s 1941 development charts in Nelson and Ash, 2010). Since formation of the planar hypoplastic lesion on the right mandibular canine of DDM 5 commenced formation at approximately one-third crown complete, the inference that this lesion was initiated at or about the time of birth is reasonable. Enamel formation returns to normal with about one-third of crown formation remaining. Since enamel formation is complete in mandibular deciduous canine teeth at between 6 and 9 months of age, the lesion may have recovered earlier at between 3 and 5 months of age.
Localized hypoplasia of primary canine teeth (LHPC). Large double defect (left panel) on right deciduous canine, and small single defect (right panel) on left canine.
Measurements of defect size, shape, and location were made from digital images using SigmaScan Pro (v. 5.0.0) image analysis software. The results of this metrical quantification of the size, shape, and location of the LHPC defects are presented (Lukacs and Pal, 2016), and confirm the asymmetry of defect size on right (area = 3.75 mm2) and left (0.87 mm2) deciduous canines (see Figure 5).
Evidence derived from the metric, morphologic, and pathologic attributes of the DDM 5 deciduous dentition yield valuable insight into biological variation and adaptation during childhood in Mesolithic India. The large and essentially disease-free deciduous dentition of DDM 5 reflects the general trend observed in the permanent dentition of Damdama, which was supportive of a tough and minimally processed diet of a semi-nomadic hunter-gatherer population in north India. The relative position of DDM 5 in Figure 3, significantly above the regression line, confirms the theoretical expectation that foragers consuming tough fibrous foods with basic food-processing technology have larger dental dimensions. Wild plant foods are significantly tougher than domesticated cultigens and farmers usually practice more extensive processing of grains. The tough and abrasive diet of foragers often includes wild fruits that are low in disaccharide sugar and high in roughage (Milton, 2002). These features probably contribute to the lower rate of dental disease.
Post-Pleistocene evolutionary trends in dental reduction have focused on the permanent dentition with little or no attention to temporal trends in deciduous tooth size. Calcagno (1989) reviews explanations for the process of dental reduction in humans including: the probable mutation effect (Brace, 1963, 1964); and five directional selection models: compensatory interaction (Sofaer, 1973; Sofaer et al., 1971), somatic budget (Jolly, 1970), selective compromise (Calcagno and Gibson, 1991), caries resistance (Greene, 1972), and population pressure (Macchiarelli and Bondioli, 1988). Although an extensive literature exists in support and critique for each of them, these models do not give attention to trends or mechanisms of deciduous dental reduction. The observed decrease in deciduous tooth size over time may result from a mix of the potential causal factors listed above, combined with increasing reliance on agricultural subsistence and on improvements in food-processing technology. The adoption of pottery for producing gruel and porridge and increasingly finely ground grains are commonly invoked mechanisms (Brace et al., 1991), but changes in dental pathology profile may also be responsible (Calcagno and Gibson, 1991). The idea that natural selection may impose different stresses or levels of intensity in sub-adults and adults has not been addressed. Is crown size reduction of deciduous teeth a secondary effect of directional selection on permanent teeth, or are selective pressures resulting in tooth size reduction acting somewhat differently on each dental complement? These issues deserve attention from clinical and bioarchaeological researchers.
The absence of pathological lesions in DDM 5, including caries, abscess cavities, alveolar resorption, and calculus, may be partly attributed to the coarse and abrasive texture of a forager diet, but also to the minimal level of food processing practiced by the semi-nomadic foragers of Damdama. The presence of developmental enamel defects in the canine teeth of DDM 5 provides information about perinatal physiological stress. Evidence from clinical studies of living populations suggests that higher frequencies of LHPC are associated with low income and disadvantaged lifestyles (Skinner and Hung, 1989; Lukacs and Walimbe, 1998). It is not possible to identify specific stress factors that might have caused the hypoplastic lesions in DDM 5, but febrile diseases and nutritional deficiencies of the mother are possible causes. Stress levels were sufficiently severe to result in disruption of physiological homeostasis during tooth enamel formation at about the time of birth.
The absence of caries lesions in association with LHPC in DDM 5 may have significance for understanding diet and oral health in Mesolithic India. In both clinical and bioarchaeological studies LEH and LHPC have been linked with caries development. The hypoplastic depressions, pits, and transverse grooves serve as traps for food and dental plaque that predispose processes of demineralization and cavitation of enamel—key factors in cariogenesis (Cook and Buikstra, 1979; Duray, 1990, 1992, 1996). Contrary to this, the fact that LHPC lesions in DDM 5 did not become sites for cariogenesis is informative and may be attributable to: (i) the coarse, abrasive, and non-cariogenic nature of the forager diet, and partly also to (ii) early mortality and the brief time the deciduous teeth had been erupted, functional, and subject to pathogens in the oral environment.
The latter explanation should be interpreted in terms of individual ontogeny of DDM 5, i.e. vital systemic functions appear to have been compromised at an early stage of development and impacted later adaptive capabilities of DDM 5. The broad theoretical foundation for this interpretation is referred to as the ‘developmental origins of health and disease hypothesis’ or the ‘Barker hypothesis.’ According to this hypothesis—a central theme in evolutionary medicine— Barker and colleagues contend that nutrient supply and demand vary during pregnancy and are influenced by many factors: maternal body composition and diet, placental blood flow, and fetal genotype (Barker, 1998, 2004). Adverse uterine environments may result in high or low neonatal birth weight, predisposing to physiological imbalances and disruptions later in life (type 2 diabetes, metabolic syndrome, and obesity; Barker, 2012). Bioarchaeological support for this hypothesis comes from the association of earlier mortality of individuals with LEH (Armelagos et al., 2009); however, this relationship has not been documented for LHPC. Further research is needed on the relationship between ‘plane-form’ enamel defects of deciduous canine teeth (LHPC) and age at death in archaeological samples.
The diverse lessons learned from the deciduous dentition of DDM 5 from Mesolithic Damdama highlight the important insights that can be gained from meticulous analysis of the dental remains of sub-adults from archaeological contexts. Perhaps this study will stimulate further studies on deciduous teeth from prehistoric populations.
My investigations of bioarchaeology and dental anthropology in South Asia over the past three decades have been supported by research grants from: the Alexander von Humboldt Foundation, the National Geographic Society, the National Science Foundation, the Smithsonian Institution (Foreign Currency Program), and the Wenner Gren Foundation for Anthropological Research. Fellowships in support of research come from the American Institute of Indian Studies and the Council for International Exchange of Scholars (Indo-American Fellowship Program).
Access to museum or field collections of prehistoric human skeletal remains has been provided by the University of Allahabad (V.D. Misra and especially J.N. Pal, who excavated human remains from Damdama in the mid-1980s); Deccan College (G.L. Badam, S.R. Walimbe, and institute directors past and present); the French Archaeological Mission to Pakistan (J.-F. and Catherine Jarrige); University of Mainz (Wolfram Berhnard); and the University of California Berkeley Harappa Project (George F. Dales). The support and co-operation of agencies, administrators, and colleagues in research is deeply appreciated.
Masato Nakatsukasa (editor-in-chief) and the editorial staff at Anthropological Science gave extensive assistance in preparing the final version of this manuscript. Their efforts are much appreciated.