Critique of ‘Australopithecus afarensis’ as a single species based on dental metrics and morphology

Ferguson, Walter W.

doi:10.1007/bf02380881

Cited by 4 publications

(4 citation statements)

References 17 publications

(13 reference statements)

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“…Leonard and Hegmon 78 have suggested that, based on P3 morphology, vast differences between certain specimens can be explained if female individuals of the species were subject to different selective pressures than male individuals. This conclusion is rejected by Ferguson 32 . Perhaps, as Schmid argues 79 , Lucy does not belong to the same species as the presumed 'males' of the species; or there may be more than one morphotype in this hypodigm.…”

Section: Fossil 'Outliers'mentioning

confidence: 97%

“…afarensis and modern H. sapiens. His conclusion is that dental variation in modern H. sapiens is 'not evidence of normal dental variation in hominids' 32 . The aim of the present study was to provide a visualisation of both the range of variability and, more importantly, the pattern of general size/shape variability that would be expected of selected hominoid species, in the context of sexual dimorphism.…”

Section: Introductionmentioning

confidence: 99%

“…Understanding this difference is important because the typically high ranges of variability in modern human skeletal elements (including teeth) are often used as benchmarks for quantifying the expected range of variability in skeletal elements of fossil hominin species, and further, in species such as Australopithecus afarensis, modern human-like sexual dimorphism is cited as the primary factor to explain such high variability between specimens of this species. 30,31 In this context, Ferguson 32 strongly emphasises the need to take into account factors such as globalisation and differences in selfdomestication between modern human populations before comparing dental variation between a fossil hominin species such as Au. afarensis and modern H. sapiens.…”

Section: Introductionmentioning

confidence: 99%

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morphometric analysis of hominin teeth attributed to Australopithecus, Paranthropus and Homo

Dykes¹

2016

S. Afr. J. Sci.

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Teeth are the most common element in the fossil record and play a critical role in taxonomic assessments. Variability in extant hominoid species is commonly used as a basis to gauge expected ranges of variability in fossil hominin species. In this study, variability in lower first molars is visualised in morphospace for four extant hominoid species and seven fossil hominin species. A size-versus-shape-based principle component analysis plot was used to recognise spatial patterns applicable to sexual dimorphism in extant species for comparison with fossil hominin species. In three African great ape species, variability occurs predominantly according to size (rather than shape), with the gorilla sample further separating into a male and a female group according to size. A different pattern is apparent for the modern human sample, in which shape variability is more evident. There is overlap between male and female modern humans and some evidence of grouping by linguistic/tribal populations. When fossil hominin species are analysed using equivalent axes of variance, the specimens group around species holotypes in quite similar patterns to those of the extant African great apes, but six individual fossil molars fall well outside of polygons circumscribing holotype clusters; at least three of these specimens are of interest for discussion in the context of sexual dimorphism, species variability and current species classifications. An implication of this study is that, especially in the case of modern humans, great caution needs to be exercised in using extant species as analogues for assessing variability considered to be a result of sexual dimorphism in fossil hominin species.

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Section: Fossil 'Outliers'mentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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morphometric analysis of hominin teeth attributed to Australopithecus, Paranthropus and Homo

Dykes¹

2016

S. Afr. J. Sci.

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“…Primatologists utilize such studies of diversity to obtain a better understanding of the natural history of the hominoids and promote conservation of endangered groups (for example, Wolfheim, 1983; Oates, 1996; Butynski, 2003; Kalpers et al, 2003; Kormos et al, 2003; Taylor & Goldsmith, 2003; Bergl, 2006; Oates et al, 2007; Williamson & Fawcett, 2008; Plumptre et al, 2010; Junker et al, 2012; Nater et al, 2017). Anthropologists and paleoanthropologists study species-subspecies diversity to provide analogues upon which to base conclusions regarding alpha taxonomy and the naming of new species in the fossil hominin context (Vitzthum, 1984; Ferguson, 1989; Wood, Li & Willoughby, 1991; Uchida, 1992; Uchida, 1996; Albrecht & Miller, 1993; Shea, Leigh & Groves, 1993; Richmond & Jungers, 1995; Braga, 1995; Plavcan & Cope, 2001; Albrecht, Gelvin & Miller, 2003; Pilbrow, 2003; Braun, Thackeray & Loots, 2004; Mitteroecker et al, 2004; Scott & Lockwood, 2004; Lee, 2005; Baab, 2008; Lordkipanidze et al, 2013). Extant hominoid species that are closely related to extinct hominin species are considered to be valuable proxies or analogues of morphological variability in fossil hominin species (Kimbel & Martin, 1993; Ackermann, 2003).…”

Section: Introductionmentioning

confidence: 99%

A mathematical landmark-based method for measuring worn molars in hominoid systematics

Dykes

Pilbrow

2019

PeerJ

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Worn teeth pose a major limitation to researchers in the fields of extinct and extant hominoid systematics because they lack clearly identifiable anatomical landmarks needed to take measurements on the crown enamel surface and are typically discarded from a study. This is particularly detrimental when sample sizes for some groups are already characteristically low, if there is an imbalance between samples representing populations, sexes or dietary strategies, or if the worn teeth in question are type specimens of fossil species or other key specimens. This study proposes a methodology based predominantly on mathematically-derived landmarks for measuring size and shape features of molars, irrespective of wear. With 110 specimens of lower second molars from five species of extant hominoids (Pan troglodytes, P. paniscus, Gorilla gorilla, G. beringei, Homo sapiens), n ≥ 20 per species, n ≥ 10 per subspecies, good species separation in morphospace is achieved in a principal components analysis. Classification accuracy in a discriminant function analysis is 96.4% at the species level and 88.2% at the subspecies level (92.7% and 79.1%, respectively, on cross-validation). The classification accuracy compares favorably to that achieved by anatomically-derived measurements based on published research (94% and 84% at the species and subspecies level respectively; 91% and 76% on cross-validation). The mathematical landmarking methodology is rapid and uncomplicated. The results support the use of mathematical landmarks to enable the inclusion of worn molar teeth in dental studies so as to maximize sample sizes and restore balance between populations and/or sexes in hominoid systematic studies.

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Australopithecus afarensis and the single species hypothesis

Leonard

1991

Primates

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ABSTRACT. FERGUSON (1989) has recently argued that the variability seen in the fossils assigned to A. afarensis is far more than expected for a single hominid species, and therefore proposes they represent multiple taxa.. In particular, he utilizes data on variation in dental metrics and in premolar morphology in support of this hypothesis.A re-evaluation of these data finds the above conclusion to be unwarranted. Variation in dental metrics provides no basis for separating this sample into multiple taxa, regardless of the analog that is used (i.e. modern primate species or fossil hominid species). Additionally, data on Pa morphology indicate that the pattern of variation seen in the Laetoli/Hadar sample is comparable to the sexual variation seen within a single hominoid species. Overall, the balance of the evidence at present indicates that the fossils from Laetoli and Hadar represent a single hominid species, A. afarensis.

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Critique of ‘Australopithecus afarensis’ as a single species based on dental metrics and morphology

Cited by 4 publications

References 17 publications

morphometric analysis of hominin teeth attributed to Australopithecus, Paranthropus and Homo

morphometric analysis of hominin teeth attributed to Australopithecus, Paranthropus and Homo

A mathematical landmark-based method for measuring worn molars in hominoid systematics

Australopithecus afarensis and the single species hypothesis

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