Molar microwear textures and the diets of Australopithecus anamensis and Au

Department of Anthropology, University of Arkansas, Old Main 330, Fayetteville, AR 72701, USA.
Philosophical Transactions of The Royal Society B Biological Sciences (Impact Factor: 7.06). 10/2010; 365(1556):3345-54. DOI: 10.1098/rstb.2010.0033
Source: PubMed


Many researchers have suggested that Australopithecus anamensis and Australopithecus afarensis were among the earliest hominins to have diets that included hard, brittle items. Here we examine dental microwear textures of these hominins for evidence of this. The molars of three Au. anamensis and 19 Au. afarensis specimens examined preserve unobscured antemortem microwear. Microwear textures of these individuals closely resemble those of Paranthropus boisei, having lower complexity values than Australopithecus africanus and especially Paranthropus robustus. The microwear texture complexity values for Au. anamensis and Au. afarensis are similar to those of the grass-eating Theropithecus gelada and folivorous Alouatta palliata and Trachypithecus cristatus. This implies that these Au. anamensis and Au. afarensis individuals did not have diets dominated by hard, brittle foods shortly before their deaths. On the other hand, microwear texture anisotropy values for these taxa are lower on average than those of Theropithecus, Alouatta or Trachypithecus. This suggests that the fossil taxa did not have diets dominated by tough foods either, or if they did that directions of tooth-tooth movement were less constrained than in higher cusped and sharper crested extant primate grass eaters and folivores.

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Available from: Mark F Teaford, Oct 08, 2015
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    • "Microwear texture attributes were produced using the scale-sensitive fractal analysis software packages ToothFrax and SFrax (SurFract Corp) [Scott et al., 2005; Ungar et al., 2010]. Variables measured include complexity (Asfc or area-scale fractal complexity), anisotropy (epLsar or exact proportion length-scale anisotropy of relief), textural fill volume (Tfv), scale of maximum complexity (Smc), and heterogeneity of complexity (HAsfc or heterogeneity of area-scale fractal complexity). "
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    ABSTRACT: Recent dental microwear studies have shown that fossil species differ from one another in texture attributes-both in terms of central tendency and dispersion. Most comparative studies used to interpret these results have relied on poorly provenienced museum samples that are not well-suited to consideration of within species variation in diet. Here we present a study of two species of platyrrhine monkeys, Alouatta belzebul (n = 60) and Sapajus apella (n = 28) from Pará State in the Brazilian Amazon in order to assess effects of habitat variation on microwear (each species was sampled from forests that differ in the degree of disturbance from highly disturbed to minimally disturbed). Results indicate that microwear texture values vary between habitats-more for the capuchins than the howler monkeys. This is consistent with the notion that diets of the more folivorous A. belzebul are less affected by habitat disturbance than those of the more frugivorous S. apella. It also suggests that microwear holds the potential to reflect comparatively subtle differences in within-species variation in fossil taxa if sample size and control over paleohabitat allow. Am. J. Primatol. © 2015 Wiley Periodicals, Inc.
    American Journal of Primatology 09/2015; DOI:10.1002/ajp.22461 · 2.44 Impact Factor
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    • "africanus (Scott et al., 2005) and Au. afarensis (Ungar et al., 2010) shows a highly variable diet with last meals mostly comprising either soft or tough materials. Animal tissues may be quite tough and require significant masticatory effort (Wrangham and Conklin-Brittain, 2003), but this is not problematic if only small amounts of meat were eaten (Hardus et al., 2012). "
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    ABSTRACT: Two fossil specimens from the DIK-55 locality in the Hadar Formation at Dikika, Ethiopia, are contemporaneous with the earliest documented stone tools, and they collectively bear twelve marks interpreted to be characteristic of stone tool butchery damage. An alternative interpretation of the marks has been that they were caused by trampling animals and do not provide evidence of stone tool use or large ungulate exploitation by Australopithecus-grade hominins. Thus, resolving which agents created marks on fossils in deposits from Dikika is an essential step in understanding the ecological and taphonomic contexts of the hominin-bearing deposits in this region and establishing their relevance for investigations of the earliest stone tool use. This paper presents results of microscopic scrutiny of all non-hominin fossils collected from the Hadar Formation at Dikika, including additional fossils from DIK-55, and describes in detail seven assemblages from sieved surface sediment samples. The study is the first taphonomic description of Pliocene fossil assemblages from open-air deposits in Africa that were collected without using only methods that emphasize the selective retention of taxonomically-informative specimens. The sieved assemblages show distinctive differences in faunal representation and taphonomic modifications that suggest they sample a range of depositional environments in the Pliocene Hadar Lake Basin, and have implications for how landscape-based taphonomy can be used to infer past microhabitats. The surface modification data show that no marks on any other fossils resemble in size or shape those on the two specimens from DIK-55 that were interpreted to bear stone tool inflicted damage. A large sample of marks from the sieved collections has characteristics that match modern trampling damage, but these marks are significantly smaller than those on the DIK-55 specimens and have different suites of characteristics. Most are not visible without magnification. The data show that the DIK-55 marks are outliers amongst bone surface damage in the Dikika area, and that trampling is not the most parsimonious interpretation of their origin. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Journal of Human Evolution 08/2015; DOI:10.1016/j.jhevol.2015.06.013 · 3.73 Impact Factor
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    • "Additional studies have tested whether striations on the labial surfaces of hominin and recent modern human incisors could determine handedness (Bax and Ungar, 1999; Bermúdez de Castro et al., 1988; Lalueza Fox and Frayer, 1997), while others have investigated whether such cultural factors as lip labret use, clamping and grasping activities, tool chipping, and weaving practices yield specific microwear signatures (Krueger, 2011, 2014; Krueger and Ungar, 2010; Lukacs and Pastor, 1988; Ryan, 1980, 1993; Ryan and Johanson, 1989; Ungar and Spencer, 1999). More recent work on incisor microwear has established its importance for determining the dietary strategies, abrasive loads, and non-dietary anterior tooth use behaviors of modern humans and Neandertals (Krueger, 2011; Krueger and Ungar, 2010, 2012). This work focused its methods on texture analysis, an objective and repeatable technique for the study of dental microwear. "
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    ABSTRACT: Diet and behavioral strategies of modern humans are examined through several indirect and direct lenses. One of the direct lenses is dental microwear texture analysis (DMTA), which examines enamel texture signatures asso-ciated with food fracture properties or behavioral regimes. While molar texture signatures are linked to dietary proclivities, those of incisors appear to reflect diet, abrasives, and non-dietary anterior tooth use behaviors. This study builds upon previous research of incisor microwear textures with the addition of six recent modern human groups. This expands the known database of incisor microwear textures to 11 bioarchaeological samples. Dental microwear textures from six bioarchaeological samples (n = 142) were collected using a white-light confocal profiler with a 100× objective lens. High-resolution casts of maxillary central incisors were scanned for clean, antemortem microwear textures. Four adjacent scans of the labial surface, nearest the incisal edge, were created, defects were removed, and scans were characterized for microwear textures using SFrax and Toothfrax scale-sensitive fractal analysis software packages. Results show that the samples differ significantly from each other in four texture variables: anisotropy, textural fill volume, heterogeneity, and complexity. These data strengthen previous hypotheses concerning anisotropy and textural fill volume as indicators of non-dietary anterior tooth use and anterior loading regimes, respectively. Moreover, while heterogeneity indicates abrasive load exposure, this measure may be exacerbated by non-dietary behaviors. Complexity is found to be significant in the current study and may reflect a balance between abrasive loads and non-dietary regimes.
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