The apportionment of tooth size and its implications in Australopithecus sediba versus other Plio‐pleistocene and recent African hominins

Abstract

The apportionment of tooth size and its implications in Australopithecus sediba versus other Plio-pleistocene and recent African hominins http://researchonline.ljmu.ac.uk/4279/ Article LJMU has developed LJMU Research Online for users to access the research output of the University more effectively. Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Users may download and/or print one copy of any article(s) in LJMU Research Online to facilitate their private study or for non-commercial research. You may not engage in further distribution of the material or use it for any profit-making activities or any commercial gain.The version presented here may differ from the published version or from the version of the record. Please see the repository URL above for details on accessing the published version and note that access may require a subscription. These findings parallel those in prior studies of dental and other skeletal data, including several that suggest A. sediba is a close relative of, if not ancestral to, Homo. 3The dental morphology of Australopithecus sediba has been characterized and compared with that of various fossil and recent hominins (Berger et al., 2010;Irish et al., , 2014. Dental measurements were also presented (Berger et al., 2010;) though, with exception (de Ruiter et al., 2013, inter-sample study of crown dimensions has been more limited. In brief, these earlier studies suggested the species: 1) is distinct from east African australopiths, 2) may be a sister species of A. africanus, and 3) along with A. africanus, is positioned at the stem of a clade comprising Homo, or otherwise shares a close relationship with the latter genus (i.e., Dembo et al., 2015). Dental morphological apomorphies relative to earlier australopiths, as well as Gorilla and Pan, include: faint shoveling of the upper central incisors (UI1), size variation between the two lingual cusps of lower fourth premolars (LP4), and increased expressions of key upper and lower molar variants (Carabelli's UM1, protostylid LM1, cusp 7 LM1) (Berger et al., 2010;Irish et al., , 2014. Odontometric apomorphies include general size reduction and a specific decrease in the canines and several posterior teeth, like that seen in later Homo (Berger et al., 2010;.The objective of this report is to expand further upon the latter topic, i.e., odontometrics in A. sediba and interspecific relationships. First, previously unpublished and several revised mesiodistal (MD) and buccolingual (BL) measurements are presented in the 1.977 Ma year-old MH1 Holotype and MH2 Paratype. The diameters are revised, albeit minimally, in that they are based on repeated-measures (re)estimates of worn and fractured crowns, and x-ray synchrotron microtomographic scans of teeth that were unerupted or are covered by matrix. Published data of the latter had originally been taken from lower resolution medical CT scans. Second, the highly heritable MD and BL crown dimensions (Alvesalo and Tigerstedt...

Dental size variability in Central African Pygmy hunter‐gatherers and Bantu‐speaking farmers

“…Tooth size apportionment (TSA) analysis was used to examine the relative size of different teeth in the dental arcade within and among groups (Harris & Bailit, ; Irish, Hemphill, de Ruiter, & Berger, ; Irish & Kenyhercz, ). Each crown dimension was divided by the geometric mean of all the dimensions used for each individual in the sample (Darroch & Mosimann, ).…”

Tooth size apportionment, Bayesian inference, and the phylogeny ofHomo naledi

“…Because TSA was found to be effective in comparing both modern human individuals and groups (Harris and Bailit, 1988;Harris and Rathbun, 1991;Hemphill et al, 1992;Lukacs and Hemphill, 1993;Harris, 1997Harris, , 1998Irish and Hemphill, 2001;Irish and Kenyhercz, 2013), which on an intraspecific level exhibit minimal variation, the approach was projected to be particularly effective in comparing more discernible interspecific dental differences in our hominin ancestors. This prediction was proven correct, as the grouping of species (in Irish et al, 2016) that were also included in other, albeit, cladistic studies (Strait et al, 1997;Strait and Grine, 2004;Smith and Grine, 2008) is congruent, as are results pertaining to specific relationships of A. sediba (Berger et al, 2010;Irish et al, , 2014Dembo et al, 2015Dembo et al, , 2016.…”

“…In this study tooth size apportionment (TSA) analysis was used to characterize further the recently defined hominin, Homo naledi , ~335-236 ka (Dirks et al, 2017), relative to other Plio-Pleistocene and recent comparative species. It builds on work demonstrating the efficacy of this odontometric technique for gauging phenetic affinities among various African hominin samples, including Australopithecus sediba, along with recent humans and Pan troglodytes (Irish et al, 2016). In TSA, the unit of study is the entire permanent dentition, rather than individual mesiodistal (MD) and buccolingual (BL) crown dimensions.…”

“…Thus, analyses of H. naledi, plus nine comparative samples of African and Eurasian Plio-Pleistocene hominin species, two regional samples of recent African H. sapiens, and Pan troglodytes will proceed as follows. First, as before (Irish et al, 2016), a standard phenetic strategy, using cluster analysis, principal components analysis, and a scatterplot is followed to obtain interspecific affinities from the continuous scaled MD and BL data. Second, for the first time in the study of hominin taxa, phylogenies are inferred based on continuous data using a Brownian-motion model and Bayesian inference (Höhna et al, 2016;Parins-Fukuchi, 2018a).…”

Population history of southern Italy during Greek colonization inferred from dental remains

“…Dental measurements were then converted into shape variables by dividing each measurement by the geometric mean for all the measurements in each individual (Jungers, Falsetti, & Wall, ). This standardization procedure removes gross size from the data in order to assess differences in the proportionate contribution of individual variables to overall tooth size (Harris & Lease, ; Hemphill, , ; Irish, Hemphill, de Ruiter, & Berger, ; Irish & Kenyhercz, ; Paul et al, ; Romero, Ramirez‐Rozzi, & Pérez‐Pérez, ; Scherer, ). Furthermore, this procedure adjusts for size differences between individuals that may result from sexual dimorphism.…”