Abrasive, Silica Phytoliths and the Evolution of Thick Molar Enamel in Primates, with Implications for the Diet of Paranthropus boisei

Rabenold, Diana; Pearson, Osbjorn M.

doi:10.1371/journal.pone.0028379

Cited by 96 publications

(75 citation statements)

References 95 publications

(109 reference statements)

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“…Some authors contend that plant phytoliths, made of amorphous, hydrated and porous silica, are important wear agents [24][25][26][27]. However, although portrayed long ago as harder than enamel [24], phytoliths are actually softer, possibly rendering them ineffectual [28].…”

Section: Introductionmentioning

confidence: 99%

Mechanisms and causes of wear in tooth enamel: implications for hominin diets

Lucas

Omar

Al‐Fadhalah

et al. 2013

J. R. Soc. Interface.

241

303

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The wear of teeth is a major factor limiting mammalian lifespans in the wild. One method of describing worn surfaces, dental microwear texture analysis, has proved powerful for reconstructing the diets of extinct vertebrates, but has yielded unexpected results in early hominins. In particular, although australopiths exhibit derived craniodental features interpreted as adaptations for eating hard foods, most do not exhibit microwear signals indicative of this diet. However, no experiments have yet demonstrated the fundamental mechanisms and causes of this wear. Here, we report nanowear experiments where individual dust particles, phytoliths and enamel chips were slid across a flat enamel surface. Microwear features produced were influenced strongly by interacting mechanical properties and particle geometry. Quartz dust was a rigid abrasive, capable of fracturing and removing enamel pieces. By contrast, phytoliths and enamel chips deformed during sliding, forming U-shaped grooves or flat troughs in enamel, without tissue loss. Other plant tissues seem too soft to mark enamel, acting as particle transporters. We conclude that dust has overwhelming importance as a wear agent and that dietary signals preserved in dental microwear are indirect. Nanowear studies should resolve controversies over adaptive trends in mammals like enamel thickening or hypsodonty that delay functional dental loss.

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Section: Introductionmentioning

confidence: 99%

Mechanisms and causes of wear in tooth enamel: implications for hominin diets

Lucas

Omar

Al‐Fadhalah

et al. 2013

J. R. Soc. Interface.

241

303

View full text Add to dashboard Cite

show abstract

“…Evidence for the role of phytoliths in tooth wear comes from the discovery of siliceous plant opals embedded in tooth enamel at the ends of microwear scratches (10), as well as experimental study by Gügel et al (11) demonstrating that cereals with differing phytolith loads leave different microwear patterns in enamel after simulated chewing. It makes sense, then, that primate species known to consume more phytolith-rich foods tend to have thicker tooth enamel (12).…”

mentioning

confidence: 99%

New model to explain tooth wear with implications for microwear formation and diet reconstruction

Xia

Zheng

Huang

et al. 2015

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

105

114

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Paleoanthropologists and vertebrate paleontologists have for decades debated the etiology of tooth wear and its implications for understanding the diets of human ancestors and other extinct mammals. The debate has recently taken a twist, calling into question the efficacy of dental microwear to reveal diet. Some argue that endogenous abrasives in plants (opal phytoliths) are too soft to abrade enamel, and that tooth wear is caused principally by exogenous quartz grit on food. If so, variation in microwear among fossil species may relate more to habitat than diet. This has important implications for paleobiologists because microwear is a common proxy for diets of fossil species. Here we reexamine the notion that particles softer than enamel (e.g., silica phytoliths) do not wear teeth. We scored human enamel using a microfabrication instrument fitted with soft particles (aluminum and brass spheres) and an atomic force microscope (AFM) fitted with silica particles under fixed normal loads, sliding speeds, and spans. Resulting damage was measured by AFM, and morphology and composition of debris were determined by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Enamel chips removed from the surface demonstrate that softer particles produce wear under conditions mimicking chewing. Previous models posited that such particles rub enamel and create ridges alongside indentations without tissue removal. We propose that although these models hold for deformable metal surfaces, enamel works differently. Hydroxyapatite crystallites are "glued" together by proteins, and tissue removal requires only that contact pressure be sufficient to break the bonds holding enamel together. dental microwear | diet reconstruction | tooth wear

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“…Indeed, tissue removal is achieved with particles much softer than enamel. 33 In this light, it makes sense that primates known to consume phytolith-rich foods tend to have thicker tooth enamel 34 , that tell-tale siliceous plant opals have been found embedded in tooth enamel at the ends of microwear scratches 35 , and that experimental studies show cereals with different phytolith loads leave different microwear patterns 36 .…”

mentioning

confidence: 99%

Dental microwear differences between eastern and southern African fossil bovids and hominins

Ungar¹,

Scott²,

Steininger³

2016

S. Afr. J. Sci.

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Dental microwear has proven to be a valuable tool for reconstructing diets of fossil vertebrates. However, recent studies have suggested that the pattern of microscopic scratches and pits on teeth may be more reflective of environmental grit than of food preferences. Could differences in dental microwear between early hominins, for example, therefore be a result of dust level rather than of diet? We investigated this possibility using a palaeocommunity approach. We compared microwear texture differences between eastern and southern African Hominini, along with Plio-Pleistocene specimens representing two tribes of bovids, Alcelaphini and Antilopini, from the same deposits as the early hominins. If exogenous grit swamps diet signals, we would expect community-wide microwear patterns separating samples by region. Results indicate that each of the three tribes shows a different pattern of variation of microwear textures between eastern and southern Africa. These results imply that differences in microwear reflect diet rather than grit load, and that microwear can provide valuable information not just about environmental dust level, but about food preferences of fossil vertebrates.

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Abrasive, Silica Phytoliths and the Evolution of Thick Molar Enamel in Primates, with Implications for the Diet of Paranthropus boisei

Cited by 96 publications

References 95 publications

Mechanisms and causes of wear in tooth enamel: implications for hominin diets

Mechanisms and causes of wear in tooth enamel: implications for hominin diets

New model to explain tooth wear with implications for microwear formation and diet reconstruction

Dental microwear differences between eastern and southern African fossil bovids and hominins

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