Tooth Form and Function: Insights into Adaptation through the Analysis of Dental Microwear

Department of Anthropology, University of Arkansas, Fayetteville, AR 72701, USA.
Frontiers of oral biology 09/2009; 13:38-43. DOI: 10.1159/000242388
Source: PubMed

ABSTRACT Mammalian molar form is clearly adapted to fracture foods with specific material properties. Studies of dental functional morphology can therefore offer important clues about the diets of fossil taxa. That said, analyses of tooth form provide insights into ability to fracture resistant foods rather than the food preferences of individuals. Recent work suggests that specialized occlusal morphology can relate to either preferred foods, or to occasionally eaten fallback items critical for survival. This paper reviews dental microwear texture analysis, a new approach that can be used to infer fracture properties of foods eaten in life. High-resolution 3D point clouds of microwear surfaces are collected and analyzed using scale-sensitive fractal analyses. Resulting data are free from operator measurement error, and allow the characterization and comparison of within-species variation in microwear texture attributes. Examples given here include four extant primate species (two folivores and two hard object fallback feeders), and two fossil hominin taxa. All groups show at least some individuals with simple microwear surfaces that suggest a lack of consumption of hard and brittle abrasive foods during the last few meals. On the other hand, some hard object fallback specimens have very complex surfaces consistent with consumption of hard, brittle foods. The latter pattern is also found in one hominin species. These results suggest that dental microwear texture analysis can help us determine whether craniodental specializations in fossil species are adaptations to preferred foods, or to less often but still critical fallback items.

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    • "The field was systematized by the work of Ungar (2007, 2009, Ungar & Kay 1995) and by Teaford (1988, 1991, 1994). The significance of grit or dust particles taken up with food items has been described by Ungar (2009) and more particularly by Damuth and Janis (2011) and Strait et al. (2012). More recently, Scott et al. (2012) isolated four microwear parameters and analyzed a range of living monkeys and apes, confirming that microwear textures vary with diet in primates. "
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    ABSTRACT: Four types of taxon-free analysis of mammalian faunas are discussed to come to an understanding of the degree to which they are independent of taxonomy. Species richness patterns and size distributions of faunal assemblages provide general indications of palaeoecology and are based entirely on species identifications; ecomorphology targets specific taxonomic groups, but within the group it is partly independent of taxonomy; community ecology describes mammalian communities by their levels of diversity within distinct ecological categories rather than by their species, and two approaches are based either on qualitative evidence (ecological diversity) or on quantitative evidence, combining ecomorphological data for whole communities (community ecomorphology). No method is entirely taxon-free, but all have stronger ecological foundations than methods based on linking fossil species of unknown habitat with their supposed habitats based on their relationships with their living relatives.
    Annales Zoologici Fennici 04/2014; 51(1-2):269-284. DOI:10.5735/086.051.0225 · 1.03 Impact Factor
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    • "). Because they are important to the survival of the animal during these periods, fallback foods may be just as influential to primate molar form as preferred foods, or more so, even though they are eaten less often during the year (Rosenberger and Kinzey, 1976; Kinzey, 1978; Rosenberger, 1992; Marshall and Wrangham, 2007; Ungar, 2009). In chimpanzee populations, the specific types and proportions of these resources may be highly variable (Morgan and Sanz, 2006). "
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    ABSTRACT: Molar tooth morphology is generally said to reflect a compromise between phylogenetic and functional influences. Chimpanzee subspecies have been reported to exhibit differences in molar dimensions and nonmetric traits, but these have not been related to differences in their diets. And in fact, observations to date of the diets of chimpanzees have not revealed consistent differences among subspecies. This study uses dental topographic analyses shown to reflect diet-related differences in occlusal morphology among primate species, to assess within-species variation among chimpanzee subspecies. High-resolution casts from museum collections were examined by laser scanning, and resulting data were analyzed using GIS algorithms and a two-factor ANOVA model. Although differences were noted between wear stages within subspecies in surface slope, relief, and angularity, none were found to distinguish the subspecies from one another in these attributes. This might reflect limitations in the ability of this method to detect diet-related differences, but is also consistent with a lack of differences in functionally relevant aspects of occlusal morphology among chimpanzee subspecies.
    American Journal of Physical Anthropology 06/2012; 148(2):276-84. DOI:10.1002/ajpa.21592 · 2.51 Impact Factor
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    • "Species that consume more hard-brittle foods tend to have higher Asfc and lower epLsar values than closely related taxa that consume softer, tougher items. This holds whether comparing primates, bovids, carnivorans, or macropodid marsupials (Scott et al., 2006; Ungar et al., 2007, 2010a; Prideaux et al., 2009; Schubert et al., 2010). Complexity reflects change in roughness (measured here as the summed area of tiles of a given size laid across a surface divided by the projected or planimetric area of that surface) across scales of observation; it is the steepest slope of the curve fitted to a plot of relative area versus scale over an order of magnitude. "
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    ABSTRACT: Dental microwear analysis has proven to be a valuable tool for the reconstruction of aspects of diet in early hominins. That said, sample sizes for some groups are small, decreasing our confidence that results are representative of a given taxon and making it difficult to assess within-species variation. Here we present microwear texture data for several new specimens of Homo habilis and Paranthropus boisei from Olduvai Gorge, bringing sample sizes for these species in line with those published for most other early hominins. These data are added to those published to date, and microwear textures of the enlarged sample of H. habilis (n = 10) and P. boisei (n = 9) are compared with one another and with those of other early hominins. New results confirm that P. boisei does not have microwear patterns expected of a hard-object specialist. Further, the separate texture complexity analyses of early Homo species suggest that Homo erectus ate a broader range of foods, at least in terms of hardness, than did H. habilis, P. boisei, or the "gracile" australopiths studied. Finally, differences in scale of maximum complexity and perhaps textural fill volume between H. habilis and H. erectus are noted, suggesting further possible differences between these species in diet.
    Journal of Human Evolution 07/2011; 63(2):429-37. DOI:10.1016/j.jhevol.2011.04.006 · 3.87 Impact Factor
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