Variations in enamel thickness and structure in East African hominids

Beynon, A.D.; Wood, B. A.

doi:10.1002/ajpa.1330700205

Cited by 153 publications

(125 citation statements)

References 23 publications

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“…One of these specimens, KNM-ER 1482 (a taxonomically enigmatic mandible) (24,36,37), has a δ 13 C value of −0.4‰. The other, KNM-ER 2607 (a taxonomically enigmatic lower molar fragment) (24,36,38), has a δ 13 C value of −9.2‰.…”

Section: Resultsmentioning

confidence: 99%

Stable isotope-based diet reconstructions of Turkana Basin hominins

Cerling

Manthi

Mbua

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

181

178

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Hominin fossil evidence in the Turkana Basin in Kenya from ca . 4.1 to 1.4 Ma samples two archaic early hominin genera and records some of the early evolutionary history of Paranthropus and Homo . Stable carbon isotopes in fossil tooth enamel are used to estimate the fraction of diet derived from C 3 or C 4 resources in these hominin taxa. The earliest hominin species in the Turkana Basin, Australopithecus anamensis , derived nearly all of its diet from C 3 resources. Subsequently, by ca . 3.3 Ma, the later Kenyanthropus platyops had a very wide dietary range—from virtually a purely C 3 resource-based diet to one dominated by C 4 resources. By ca . 2 Ma, hominins in the Turkana Basin had split into two distinct groups: specimens attributable to the genus Homo provide evidence for a diet with a ca . 65/35 ratio of C 3 - to C 4 -based resources, whereas P. boisei had a higher fraction of C 4 -based diet ( ca . 25/75 ratio). Homo sp. increased the fraction of C 4 -based resources in the diet through ca . 1.5 Ma, whereas P. boisei maintained its high dependency on C 4 -derived resources.

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Section: Resultsmentioning

confidence: 99%

Stable isotope-based diet reconstructions of Turkana Basin hominins

Cerling

Manthi

Mbua

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

181

178

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“…Bromage and Dean (1985) reassessed the age at death of fossil hominids using incremental features, and concluded that early humans were characterized by ape-like dental development, in contrast to the previously assumed modern human pattern. These were followed by many more studies of fossil hominids that examined the nature of enamel development and enamel thickness as revealed by microstructure (Beynon and Wood, 1986;Dean et al, 1986;Beynon and Dean, 1987;Beynon and Wood, 1987;Dean, 1987a,b;Beynon and Dean, 1988;Grine and Martin, 1988;Mann et al, 1991;Beynon, 1992;Dean et al, 1993a;Ramirez Rozzi, 1993a,b;Mann et al, 1994;Ramirez Rozzi, 1994;Dean, 1995;Ramirez Rozzi, 1997;Ramirez Rozzi et al, 1997;Ramirez Rozzi, 1998;). These investigations have provided information on age at death in individuals with developing dentitions, the absolute and relative timing of dental development, differences in the developmental pathways of enamel formation, and life history characteristics.…”

Section: Introductionmentioning

confidence: 99%

Enamel thickness, microstructure and development in Afropithecus turkanensis

Smith

Martin

Leakey

2003

Journal of Human Evolution

118

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Afropithecus turkanensis, a 17-17.5 million year old large-bodied hominoid from Kenya, has previously been reported to be the oldest known thick-enamelled Miocene ape. Most investigations of enamel thickness in Miocene apes have been limited to opportunistic or destructive studies of small samples. Recently, more comprehensive studies of enamel thickness and microstructure in Proconsul, Lufengpithecus, and Dryopithecus, as well as extant apes and fossil humans, have provided information on rates and patterns of dental development, including crown formation time, and have begun to provide a comparative context for interpretation of the evolution of these characters throughout the past 20 million years of hominoid evolution. In this study, enamel thickness and aspects of the enamel microstructure in two A. turkanensis second molars were quantified and provide insight into rates of enamel apposition, numbers of cells actively secreting enamel, and the time required to form regions of the crown. The average value for relative enamel thickness in the two molars is 21.4, which is a lower value than a previous analysis of this species, but which is still relatively thick compared to extant apes. This value is similar to those of several Miocene hominoids, a fossil hominid, and modern humans. Certain aspects of the enamel microstructure are similar to Proconsul nyanzae, Dryopithecus laietanus, Lufengpithecus lufengensis, Graecopithecus freybergi and Pongo pygmaeus, while other features differ from extant and fossil hominoids. Crown formation times for the two teeth are 2.4-2.6 years and 2.9-3.1 years respectively. These times are similar to a number of extant and fossil hominoids, some of which appear to show additional developmental similarities, including thick enamel. Although thick enamel may be formed through several developmental pathways, most Miocene hominoids and fossil hominids with relatively thick enamel are characterized by a relatively long period of cuspal enamel formation and a rapid rate of enamel secretion throughout the whole cusp, but a shorter total crown formation time than thinner-enamelled extant apes.

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“…Physical cross-sections of molar teeth have been used to measure enamel thickness by a number of workers (e.g., Molnar and Gantt, 1977;Martin, 1985;Beynon and Wood, 1986;Grine and Martin, 1988;Macho and Berner, 1993;Dumont, 1995;Schwartz, 2000b;Grine, 2002Grine, , 2004Grine, , 2005Grine et al, 2005). Physical sections provide an accurate portrayal of enamel thickness in a particular plane of section, but problems with specimen orientation (i.e., section obliquity) may render some of these data less than ideal.…”

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confidence: 99%

Assessment of the accuracy of dental enamel thickness measurements using microfocal X‐ray computed tomography

2006

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Tooth enamel thickness has long been an important character in studies of primate and especially hominin phylogeny, taxonomy, and adaptation. Current methods for accurately assessing enamel thickness involve the physical sectioning of teeth, because measurements of enamel thickness using some radiographic techniques are unreliable. However, because destructive methods limit sample sizes and access to important fossil specimens, it is desirable that they be replaced with nondestructive techniques. Although microfocal X-ray computed tomography (mCT) has been used recently in studies of enamel thickness, the accuracy of this technique has yet to be established. The present research compares physical sections to computer-generated mCT sections of teeth from a variety of primate and nonprimate, recent and fossil taxa to examine whether enamel thickness, tooth size, and diagenetic remineralization (fossilization) impact the ability of mCT to measure enamel thickness accurately. Results indicate that recent teeth of varying size and thickness are clearly and accurately depicted in mCT scans, with measurements from nearly identical planes in physical and mCT sections differing by 3-5%. A fossil papionin molar (ca. 2 Myr) was also accurately measured using mCT scans, although thinner enamel in much older therapsid (ca. 263-241 Myr) teeth could not be distinguished from dentine. mCT is thus an accurate technique for measuring enamel thickness in recent taxa, although heavily mineralized teeth pose an obstacle to the ability of mCT to distinguish dental tissues. Moreover, absolutely thin enamel (less than ϳ 0.10 mm) is difficult to resolve adequately in raw mCT images based on pixel values alone. Therefore, caution must be exercised in the application of mCT to the study of fossilized teeth. © 2006 Wiley-Liss, Inc.Key words: mCT; microfocal X-ray computed tomography; enamel thickness; measurement accuracy; diagenesis; dental enamel; dentine Tooth enamel thickness has long been considered to be of importance in the interpretation of human evolution because of its purported taxonomic and phylogenetic value

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Variations in enamel thickness and structure in East African hominids

Cited by 153 publications

References 23 publications

Stable isotope-based diet reconstructions of Turkana Basin hominins

Stable isotope-based diet reconstructions of Turkana Basin hominins

Enamel thickness, microstructure and development in Afropithecus turkanensis

Assessment of the accuracy of dental enamel thickness measurements using microfocal X‐ray computed tomography

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