1
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Nava A, Lugli F, Lemmers S, Cerrito P, Mahoney P, Bondioli L, Müller W. Reading children's teeth to reconstruct life history and the evolution of human cooperation and cognition: the role of dental enamel microstructure and chemistry. Neurosci Biobehav Rev 2024:105745. [PMID: 38825260 DOI: 10.1016/j.neubiorev.2024.105745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 05/25/2024] [Accepted: 05/30/2024] [Indexed: 06/04/2024]
Abstract
Studying infants in the past is crucial for understanding the evolution of human life history and the evolution of cooperation, cognition, and communication. An infant's growth, health, and mortality can provide information about the dynamics and structure of a population, their cultural practices, and the adaptive capacity of a community. Skeletal remains provide one way of accessing this information for humans recovered prior to the historical periods. Teeth in particular, are retrospective archives of information that can be accessed through morphological, micromorphological, and biogeochemical methods. This review discusses how the microanatomy and formation of teeth, and particularly enamel, serve as archives of somatic growth, stress, and the environment. Examining their role in the broader context of human evolution, we discuss dental biogeochemistry and emphasize how the incremental growth of tooth microstructure facilitates the reconstruction of temporal data related to health, diet, mobility, and stress in past societies. The review concludes by considering tooth microstructure as a biomarker and the potential clinical applications.
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Affiliation(s)
- Alessia Nava
- Department of Odontostomatological and Maxillofacial Sciences, Sapienza University of Rome, via Caserta 6, 00161, Rome, Italy.
| | - Federico Lugli
- Institut of Geosciences, Goethe University Frankfurt, Frankfurt am Main, Germany; Department of Chemical and Geological Science, University of Modena and Reggio Emilia, via Giuseppe Campi, 103, 41125 Modena, Italy.
| | - Simone Lemmers
- Elettra Sincrotrone Trieste S.C.p.A., AREA Science Park, s.s. 14 km 163,500, Basovizza, Trieste, Italy; Department of Psychiatry, Harvard Medical School, 401 Park Drive, Boston, Massachusetts, USA; Center for Genomic Medicine, Massachusetts General Hospital, 185 Cambridge Street, Boston, Massachusetts, USA.
| | - Paola Cerrito
- Department of Evolutionary Anthropology, University of Zürich, Zürich, Switzerland.
| | - Patrick Mahoney
- School of Anthropology and Conservation, University of Kent, Giles Ln, CT2 7NZ, Canterbury, UK.
| | - Luca Bondioli
- Department of Cultural Heritage, University of Padua, Piazza Capitaniato, 7, 35139, Padua, Italy.
| | - Wolfgang Müller
- Institut of Geosciences, Goethe University Frankfurt, Frankfurt am Main, Germany; Frankfurt Isotope and Element Research Center (FIERCE), Goethe University Frankfurt, Frankfurt am Main, Germany.
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2
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Mahoney P, McFarlane G, Taurozzi AJ, Madupe PP, O'Hara MC, Molopyane K, Cappellini E, Hawks J, Skinner MM, Berger L. Human-like enamel growth in Homo naledi. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2024; 184:e24893. [PMID: 38180115 DOI: 10.1002/ajpa.24893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 11/12/2023] [Accepted: 12/14/2023] [Indexed: 01/06/2024]
Abstract
OBJECTIVES A modern pattern (rate and duration) of dental development occurs relatively recently during human evolution. Given the temporal overlap of Homo naledi with the first appearance of fossil Homo sapiens in Africa, this small-bodied and small-brained hominin presents an opportunity to elucidate the evolution of enamel growth in the hominin clade. Here we conduct the first histological study of two permanent mandibular canines and one permanent maxillary first molar, representing three individuals attributed to H. naledi. We reconstruct the rate and duration of enamel growth and compare these findings to those reported for other fossil hominins and recent humans. MATERIALS AND METHODS Thin sections of each tooth were produced using standard histological methods. Daily and longer period incremental markings were measured to reconstruct enamel secretion and extension rates, Retzius periodicity, canine crown and molar cusp formation time. RESULTS Daily enamel secretion rates overlapped with those from recent hominins. Canine crown formation time is similar to that observed in recent Europeans but is longer than canine formation times reported for most other hominins including Australopithecus and H. neanderthalensis. The extended period of canine formation appears to be due to a relatively tall enamel crown and a sustained slow rate of enamel extension in the cervical portion of the crown. A Retzius periodicity of 11 days for the canines, and nine days for the molar, in H. naledi parallel results found in recent humans. An 11-day periodicity has not been reported for Late Pleistocene Homo (H. erectus, H. neanderthalensis) and is rarely found in Australopithecus and Paranthropus species. DISCUSSION Enamel growth of H. naledi is most similar to recent humans though comparative data are limited for most fossil hominin species. The high Retzius periodicity values do not follow expectations for a small-brained hominin.
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Affiliation(s)
- Patrick Mahoney
- Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Gina McFarlane
- Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Alberto J Taurozzi
- Section for GeoGenetics, Globe Institute, University of Copenhagen, Copenhagen, Denmark
| | - Palesa P Madupe
- Section for GeoGenetics, Globe Institute, University of Copenhagen, Copenhagen, Denmark
- Human Evolution Research Institute, University of Cape Town, Rondebosch, South Africa
| | - Mackie C O'Hara
- Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Keneiloe Molopyane
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
- The National Geographic Society, Washington, District of Columbia, USA
| | - Enrico Cappellini
- Section for GeoGenetics, Globe Institute, University of Copenhagen, Copenhagen, Denmark
| | - John Hawks
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
- Department of Anthropology, University of Wisconsin-Madison, USA
| | - Matthew M Skinner
- Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Lee Berger
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
- The National Geographic Society, Washington, District of Columbia, USA
- The Carnegie Institution for Science, Washington, District of Columbia, USA
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3
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Emken S, Witzel C, Kierdorf U, Frölich K, Kierdorf H. Wild boar versus domestic pig-Deciphering of crown growth in porcine second molars. J Anat 2023; 242:1078-1095. [PMID: 36774334 PMCID: PMC10184542 DOI: 10.1111/joa.13838] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 01/15/2023] [Accepted: 01/18/2023] [Indexed: 02/13/2023] Open
Abstract
Based on the previously established periodicity of enamel growth marks, we reconstructed crown growth parameters of mandibular second molars from two wild boar and two domestic pigs of the Linderöd breed. Body weight gain and progression of dental development were markedly faster in the domestic pigs than the wild boar. While the final crown dimensions of the M2 did not differ between domestic pigs and wild boar, mean crown formation time (CFT) of this tooth was considerably shorter in the domestic pigs (162 days) than in the wild boar (205 days). The difference in CFT was mainly attributable to a higher enamel extension rate (EER) in the domestic pig. Generally, EER was highest in the cuspalmost deciles of the length of the enamel-dentine-junction and markedly dropped in cervical direction, with lowest values occurring in the cervicalmost decile. In consequence, the cuspal half of the M2 crown was formed about three times faster than the cervical half. In contrast to the EER, no marked difference in daily enamel secretion rate (DSR) was recorded between domestic pigs and wild boar. The duration of enamel matrix apposition as well as linear enamel thickness in corresponding crown portions was only slightly lower in the domestic pigs than the wild boar. Thus, the earlier completion of M2 crown growth in the domestic pig was mainly achieved by a higher EER and not by an increased DSR. The more rapid recruitment of secretory ameloblasts in the course of molar crown formation of domestic pigs compared to wild boar is considered a side-effect of the selection for rapid body growth during pig domestication.
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Affiliation(s)
- Simon Emken
- Department of Biology, University of Hildesheim, Hildesheim, Germany
| | - Carsten Witzel
- Department of Biology, University of Hildesheim, Hildesheim, Germany
| | - Uwe Kierdorf
- Department of Biology, University of Hildesheim, Hildesheim, Germany
| | - Kai Frölich
- Department of Biology, University of Hildesheim, Hildesheim, Germany.,Tierpark Arche Warder e.V, Warder, Germany
| | - Horst Kierdorf
- Department of Biology, University of Hildesheim, Hildesheim, Germany
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4
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Dietary strategies of Pleistocene Pongo sp. and Homo erectus on Java (Indonesia). Nat Ecol Evol 2023; 7:279-289. [PMID: 36646949 DOI: 10.1038/s41559-022-01947-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Accepted: 11/09/2022] [Indexed: 01/18/2023]
Abstract
During the Early to Middle Pleistocene, Java was inhabited by hominid taxa of great diversity. However, their seasonal dietary strategies have never been explored. We undertook geochemical analyses of orangutan (Pongo sp.), Homo erectus and other mammalian Pleistocene teeth from Sangiran. We reconstructed past dietary strategies at subweekly resolution and inferred seasonal ecological patterns. Histologically controlled spatially resolved elemental analyses by laser-based plasma mass spectrometry confirmed the preservation of authentic biogenic signals despite the effect of spatially restricted diagenetic overprint. The Sr/Ca record of faunal remains is in line with expected trophic positions, contextualizing fossil hominid diet. Pongo sp. displays marked seasonal cycles with ~3 month-long strongly elevated Sr/Ca peaks, reflecting contrasting plant food consumption presumably during the monsoon season, while lower Sr/Ca ratios suggest different food availability during the dry season. In contrast, omnivorous H. erectus shows low and less accentuated intra-annual Sr/Ca variability compared to Pongo sp., with δ13C data of one individual indicating a dietary shift from C4 to a mix of C3 and C4 plants. Our data suggest that H. erectus on Java was maximizing the resources available in more open mosaic habitats and was less dependent on variations in seasonal resource availability. While still influenced by seasonal food availability, we infer that H. erectus was affected to a lesser degree than Pongo sp., which inhabited monsoonal rain forests on Java. We suggest that H. erectus maintained a greater degree of nutritional independence by exploiting the regional diversity of food resources across the seasons.
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5
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Guatelli‐Steinberg D, Schwartz GT, O'Hara MC, Gurian K, Rychel J, McGraw WS. Molar form, enamel growth, and durophagy in Cercocebus and Lophocebus. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2022; 179:386-404. [PMCID: PMC9796247 DOI: 10.1002/ajpa.24592] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 06/20/2022] [Accepted: 06/29/2022] [Indexed: 05/29/2023]
Abstract
Objectives To test the hypothesis that differences in crown structure, enamel growth, and crown geometry in Cercocebus and Lophocebus molars covary with differences in the feeding strategies (habitual vs. fallback durophagy, respectively) of these two genera. Relative to Lophocebus molars, Cercocebus molars are predicted to possess features associated with greater fracture resistance and to differ in enamel growth parameters related to these features. Materials and Methods Sample proveniences are as follows: Cercocebus atys molars are from the Taï Forest, Ivory Coast; Lophocebus albigena molars are from a site north of Makoua, Republic of Congo; and a Lophocebus atterimus molar is from the Lomako Forest, Democratic Republic of Congo. For μCT scans on which aspects of molar form were measured, sample sizes ranged from 5 to 35 for Cercocebus and 3 to 12 for Lophocebus. A subsample of upper molars was physically sectioned to measure enamel growth variables. Results Partly as a function of their larger size, Cercocebus molars had significantly greater absolute crown strength (ACS) than Lophocebus molars, supporting the hypothesis. Greater crown heights in Cercocebus are achieved through faster enamel extension rates. Also supporting the hypothesis, molar flare and proportional occlusal basin enamel thickness were significantly greater in Cercocebus. Relative enamel thickness (RET), however, was significantly greater in Lophocebus. Discussion If ACS is a better predictor of fracture resistance than RET, then Cercocebus molars may be more fracture resistant than those of Lophocebus. Greater molar flare and proportional occlusal basin thickness might also afford Cercocebus molars greater fracture resistance.
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Affiliation(s)
| | - Gary T. Schwartz
- School of Human Evolution and Social Change and Institute of Human OriginsArizona State UniversityTempeArizonaUSA
| | - Mackie C. O'Hara
- Department of AnthropologyThe Ohio State UniversityColumbusOhioUSA
- School of Anthropology and ConservationUniversity of KentCanterburyUK
| | - Kaita Gurian
- Department of AnthropologyThe Ohio State UniversityColumbusOhioUSA
| | - Jess Rychel
- Department of AnthropologyThe Ohio State UniversityColumbusOhioUSA
| | - W. Scott McGraw
- Department of AnthropologyThe Ohio State UniversityColumbusOhioUSA
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6
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Distinguishing primate taxa with enamel incremental variables. J Hum Evol 2022; 164:103139. [PMID: 35123173 DOI: 10.1016/j.jhevol.2021.103139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 12/23/2021] [Accepted: 12/23/2021] [Indexed: 11/23/2022]
Abstract
Enamel has long been of interest for its functional and phylogenetic significance among fossil hominins and other primates. Previous studies demonstrated that enamel incremental features distinguish among hominin fossil taxa, suggesting utility for highlighting taxonomy. However, not all features appear to be useful in mixed samples of fossils, living humans, and apes. Here we tested enamel incremental data from closely related primate taxa to determine which features, if any, distinguish among them. Enamel incremental variables were measured from the M2 of 40 living primate taxa, and we tested our variables using discriminant function analysis at the taxonomic ranks of parvorder, family, tribe, and genus. We then included enamel incremental data from Australopithecus afarensis, Australopithecus africanus, Paranthropus aethiopicus, Paranthropus boisei, and Paranthropus robustus to determine if these features distinguished fossil taxa from living humans and apes. Our initial results show that enamel incremental variables distinguish among primate taxa, but with low classification rates. Further testing with jackknifing methods shows overlap between groups at all taxonomic ranks, suggesting enamel incremental variables are unreliable for taxonomy. The addition of many common enamel incremental growth variables also resulted in multicollinearity in our multivariate analysis. As the dentition and isolated teeth remain a significant portion of the hominin fossil record, verifying enamel incremental features as a useful taxonomic tool is fundamentally important for hominin paleobiology.
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7
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O'Hara MC, Guatelli-Steinberg D. Reconstructing tooth crown heights and enamel caps: A comparative test of three existing methods with recommendations for their use. Anat Rec (Hoboken) 2022; 305:123-143. [PMID: 33843152 DOI: 10.1002/ar.24637] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 03/04/2021] [Accepted: 03/04/2021] [Indexed: 01/05/2023]
Abstract
Studies of enamel growth and thickness, whether in paleoanthropology, bioarchaeology, or primatology, require measurements of crown height (CH), cuspal enamel thickness (CET), average (AET), and/or regional enamel thickness (RegAET) on complete, unworn crowns. Yet because fully unworn crowns are uncommon, three methods to bolster sample sizes by reconstructing slightly worn teeth have been developed: Profile, Polynomial, and Pen Tool. Although these methods have been tested for accuracy, no study has yet directly compared the three methods to assess their performance across CH, CET, AET, and RegAET measurements. Moreover, it is currently unclear how accurate the methods are when reconstructing crowns with varying degrees of wear. The present study addresses this gap in our understanding of how these methods perform on four key dental measurements, evaluates the degree of wear for which accurate crown reconstructions can be completed, and offers recommendations for applying these methods. Here, the methods are compared on Paranthropus robustus mandibular molars, a sample chosen because it exhibits variable morphology, presenting a challenge for reconstruction methods. For minimally worn teeth, Profile, Polynomial, and Pen Tool methods can be employed (in that order) for all measurements except CET, which cannot be reliably measured on reconstructions. For teeth with wear that obliterates the nadir of the occlusal basin or dentin horns, CH and AET can be measured using Profile and Polynomial reconstructions; however, no other measurements or methods were reliable. Recommendations provided here will make it possible to increase sample sizes and replicability, enhancing studies of enamel thickness and growth.
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Affiliation(s)
- Mackie C O'Hara
- Department of Anthropology, The Ohio State University, Columbus, Ohio, USA
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8
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McGrath K, Limmer LS, Lockey AL, Guatelli-Steinberg D, Reid DJ, Witzel C, Bocaege E, McFarlin SC, El Zaatari S. 3D enamel profilometry reveals faster growth but similar stress severity in Neanderthal versus Homo sapiens teeth. Sci Rep 2021; 11:522. [PMID: 33436796 PMCID: PMC7804262 DOI: 10.1038/s41598-020-80148-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 12/16/2020] [Indexed: 01/19/2023] Open
Abstract
Early life stress disrupts growth and creates horizontal grooves on the tooth surface in humans and other mammals, yet there is no consensus for their quantitative analysis. Linear defects are considered to be nonspecific stress indicators, but evidence suggests that intermittent, severe stressors create deeper defects than chronic, low-level stressors. However, species-specific growth patterns also influence defect morphology, with faster-growing teeth having shallower defects at the population level. Here we describe a method to measure the depth of linear enamel defects and normal growth increments (i.e., perikymata) from high-resolution 3D topographies using confocal profilometry and apply it to a diverse sample of Homo neanderthalensis and H. sapiens anterior teeth. Debate surrounds whether Neanderthals exhibited modern human-like growth patterns in their teeth and other systems, with some researchers suggesting that they experienced more severe childhood stress. Our results suggest that Neanderthals have shallower features than H. sapiens from the Upper Paleolithic, Neolithic, and medieval eras, mirroring the faster growth rates in Neanderthal anterior teeth. However, when defect depth is scaled by perikymata depth to assess their severity, Neolithic humans have less severe defects, while Neanderthals and the other H. sapiens groups show evidence of more severe early life growth disruptions.
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Affiliation(s)
- Kate McGrath
- CNRS, MCC, PACEA, UMR 5199, Univ. Bordeaux, Bâtiment B8, Allée Geoffroy Saint-Hilaire, 33615, Pessac, France. .,Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, 800 22nd St. NW, Suite 6000, Washington, DC, 20052, USA.
| | - Laura Sophia Limmer
- Paleoanthropology, Senckenberg Center for Human Evolution and Paleoenvironment, Universität Tübingen, Rümelinstraße 23, 72070, Tübingen, Germany
| | - Annabelle-Louise Lockey
- Paleoanthropology, Senckenberg Center for Human Evolution and Paleoenvironment, Universität Tübingen, Rümelinstraße 23, 72070, Tübingen, Germany
| | - Debbie Guatelli-Steinberg
- Department of Anthropology, Department of Evolution, Ecology and Organismal Biology, The Ohio State University, 4034 Smith Laboratory, 174 W 18th Avenue, Columbus, OH, 43210, USA.,Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Canterbury, Kent, CT2 7NZ, UK
| | - Donald J Reid
- Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, 800 22nd St. NW, Suite 6000, Washington, DC, 20052, USA
| | - Carsten Witzel
- Department of Biology, Universität Hildesheim, Universitätsplatz 1, 31141, Hildesheim, Germany
| | - Emmy Bocaege
- Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Canterbury, Kent, CT2 7NZ, UK
| | - Shannon C McFarlin
- Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, 800 22nd St. NW, Suite 6000, Washington, DC, 20052, USA.,Human Origins Program, National Museum of Natural History, Smithsonian Institution, 10th Street & Constitution Avenue NW, Washington, DC, 20560, USA
| | - Sireen El Zaatari
- Paleoanthropology, Senckenberg Center for Human Evolution and Paleoenvironment, Universität Tübingen, Rümelinstraße 23, 72070, Tübingen, Germany
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9
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McFarlane G, Guatelli-Steinberg D, Loch C, White S, Bayle P, Floyd B, Pitfield R, Mahoney P. An inconstant biorhythm: The changing pace of Retzius periodicity in human permanent teeth. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 175:172-186. [PMID: 33368148 DOI: 10.1002/ajpa.24206] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 11/06/2020] [Accepted: 12/06/2020] [Indexed: 12/25/2022]
Abstract
OBJECTIVES Human tooth enamel retains evidence of growth in the form of Retzius lines. The number of daily growth increments between the regularly occurring lines defines their repeat interval, or periodicity. Retzius periodicity is often incorporated into enamel formation times, age-at-death reconstructions, or used to provide a basis from which to explore an underlying biorhythm. Biological anthropologists typically assume that RP remains constant within an individual and does not vary along the tooth-row. Here, we test that assumption. MATERIALS AND METHODS RP was calculated from n = 223 thin sections of human permanent teeth from individuals of British and southern African origin. Forty individuals provided multiple teeth (n = 102 teeth) and a further 121 individuals each provided a single tooth. RESULTS We report first evidence that RP of permanent teeth does not always remain constant within an individual. Of those individuals that provided multiple teeth, 42% (n = 17/40) demonstrated a decrease in RP along the tooth row, with most shifting by two or more days (n = 11). Across the entire sample, mean RP of anterior teeth was significantly higher than molars. Mean premolar RP tended to be intermediate between anterior teeth and molars. DISCUSSION Our data do not support the assumption that RP invariably remains constant within the permanent teeth of an individual. Transferring RP from molars to incisors within an individual can result in a miscalculation of formation time and age-at-death by up to 1 year. Implications for biological anthropologists and the source of the underlying long period biorhythm are discussed.
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Affiliation(s)
- Gina McFarlane
- Human Osteology Lab, School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Debbie Guatelli-Steinberg
- Human Osteology Lab, School of Anthropology and Conservation, University of Kent, Canterbury, UK.,Department of Anthropology, The Ohio State University, Columbus, Ohio, USA
| | - Carolina Loch
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, New Zealand
| | - Sophie White
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, New Zealand
| | | | - Bruce Floyd
- School of Social Sciences, University of Auckland, New Zealand
| | - Rosie Pitfield
- Human Osteology Lab, School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Patrick Mahoney
- Human Osteology Lab, School of Anthropology and Conservation, University of Kent, Canterbury, UK
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10
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Dean C, Zanolli C, Le Cabec A, Tawane M, Garrevoet J, Mazurier A, Macchiarelli R. Growth and development of the third permanent molar in Paranthropus robustus from Swartkrans, South Africa. Sci Rep 2020; 10:19053. [PMID: 33149180 PMCID: PMC7642444 DOI: 10.1038/s41598-020-76032-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 10/15/2020] [Indexed: 11/24/2022] Open
Abstract
Third permanent molars (M3s) are the last tooth to form but have not been used to estimate age at dental maturation in early fossil hominins because direct histological evidence for the timing of their growth has been lacking. We investigated an isolated maxillary M3 (SK 835) from the 1.5 to 1.8-million-year-old (Mya) site of Swartkrans, South Africa, attributed to Paranthropus robustus. Tissue proportions of this specimen were assessed using 3D X-ray micro-tomography. Thin ground sections were used to image daily growth increments in enamel and dentine. Transmitted light microscopy and synchrotron X-ray fluorescence imaging revealed fluctuations in Ca concentration that coincide with daily growth increments. We used regional daily secretion rates and Sr marker-lines to reconstruct tooth growth along the enamel/dentine and then cementum/dentine boundaries. Cumulative growth curves for increasing enamel thickness and tooth height and age-of-attainment estimates for fractional stages of tooth formation differed from those in modern humans. These now provide additional means for assessing late maturation in early hominins. M3 formation took ≥ 7 years in SK 835 and completion of the roots would have occurred between 11 and 14 years of age. Estimated age at dental maturation in this fossil hominin compares well with what is known for living great apes.
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Affiliation(s)
- Christopher Dean
- Department of Earth Sciences, Natural History Museum, London, UK. .,Department of Cell and Developmental Biology, University College London, London, UK.
| | - Clément Zanolli
- Univ. Bordeaux, CNRS, MCC, PACEA, UMR 5199, 33600 Pessac, France.,Department of Maxillofacial and Oral Surgery, Sefako Makgatho Health Sciences University, Ga-Rankuwa, Pretoria, South Africa
| | - Adeline Le Cabec
- Univ. Bordeaux, CNRS, MCC, PACEA, UMR 5199, 33600 Pessac, France.,Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Mirriam Tawane
- Ditsong National Museum of Natural History, Pretoria, South Africa
| | - Jan Garrevoet
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
| | - Arnaud Mazurier
- IC2MP, UMR 7285 CNRS, Université de Poitiers, Poitiers, France
| | - Roberto Macchiarelli
- UMR 7194 CNRS, Muséum National D'Histoire Naturelle, Musée de L'Homme, Paris, France.,Unité de Formation Géosciences, Université de Poitiers, Poitiers, France
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11
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Abstract
The early onset of weaning in modern humans has been linked to the high nutritional demand of brain development that is intimately connected with infant physiology and growth rate. In Neanderthals, ontogenetic patterns in early life are still debated, with some studies suggesting an accelerated development and others indicating only subtle differences vs. modern humans. Here we report the onset of weaning and rates of enamel growth using an unprecedented sample set of three late (∼70 to 50 ka) Neanderthals and one Upper Paleolithic modern human from northeastern Italy via spatially resolved chemical/isotopic analyses and histomorphometry of deciduous teeth. Our results reveal that the modern human nursing strategy, with onset of weaning at 5 to 6 mo, was present among these Neanderthals. This evidence, combined with dental development akin to modern humans, highlights their similar metabolic constraints during early life and excludes late weaning as a factor contributing to Neanderthals' demise.
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12
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Dean MC, Le Cabec A, Van Malderen SJ, Garrevoet J. Synchrotron X-ray fluorescence imaging of strontium incorporated into the enamel and dentine of wild-shot orangutan canine teeth. Arch Oral Biol 2020; 119:104879. [DOI: 10.1016/j.archoralbio.2020.104879] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/10/2020] [Accepted: 08/10/2020] [Indexed: 10/23/2022]
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13
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Dirks W, Lemmers SAM, Ngoubangoye B, Herbert A, Setchell JM. Odontochronologies in male and female mandrills (
Mandrillus sphinx
) and the development of dental sexual dimorphism. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 172:528-544. [DOI: 10.1002/ajpa.24094] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 02/18/2020] [Accepted: 05/15/2020] [Indexed: 12/13/2022]
Affiliation(s)
- Wendy Dirks
- Department of AnthropologyDurham University Durham UK
| | - Simone A. M. Lemmers
- Department of AnthropologyDurham University Durham UK
- Science and Technology in Archaeology Research CenterThe Cyprus Institute Nicosia Cyprus
| | | | - Anaïs Herbert
- Centre de Primatologie, Centre Internationale de Recherches Médicales Franceville Gabon
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14
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Dean MC, Humphrey L, Groom A, Hassett B. Variation in the timing of enamel formation in modern human deciduous canines. Arch Oral Biol 2020; 114:104719. [DOI: 10.1016/j.archoralbio.2020.104719] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 03/07/2020] [Accepted: 04/05/2020] [Indexed: 01/17/2023]
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15
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Faster growth corresponds with shallower linear hypoplastic defects in great ape canines. J Hum Evol 2019; 137:102691. [PMID: 31704354 DOI: 10.1016/j.jhevol.2019.102691] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 10/10/2019] [Accepted: 10/10/2019] [Indexed: 11/24/2022]
Abstract
Deeper or more 'severe' linear enamel hypoplasia (LEH) defects are hypothesized to reflect more severe stress during development, but it is not yet clear how depth is influenced by intrinsic enamel growth patterns. Recent work documented inter- and intraspecific differences in LEH defect depth in extant great apes, with mountain gorillas having shallower defects than other taxa, and females having deeper defects than males. Here, we assess the correspondence of inter- and intraspecific defect depth and intrinsic aspects of enamel growth: enamel extension rates, outer enamel striae of Retzius angles, and linear enamel thickness. Thin sections of great ape canines (n = 40) from Gorilla beringei beringei, Gorilla gorilla gorilla, Pan troglodytes, and Pongo spp. were analyzed. Enamel extension rates were calculated within deciles of enamel-dentine junction length. Linear enamel thickness and the angle of intersection between striae of Retzius and the outer enamel surface were measured in the imbricational enamel. Mountain gorillas have faster enamel extension rates and shallower striae angles than the other taxa examined. Mountain gorillas have thinner imbricational enamel than western lowland gorillas and orangutans, but not chimpanzees. In the combined-taxon sample, females exhibit larger striae angles and thicker imbricational enamel than males. Enamel extension rates are highly negatively correlated with striae angles and LEH defect depth. Enamel growth variation corresponds with documented inter- and intraspecific differences in LEH defect depth in great ape canines. Mountain gorillas have shallower striae angles and faster extension rates than other taxa, which might explain their shallow LEH defect morphology and the underestimation of their LEH prevalence in previous studies. These results suggest that stressors of similar magnitude and timing might produce defects of different depths in one species or sex vs. another, which has implications for interpretations of stress histories in hominins with variable enamel growth patterns.
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16
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Xing S, Tafforeau P, O’Hara M, Modesto-Mata M, Martín-Francés L, Martinón-Torres M, Zhang L, Schepartz LA, de Castro JMB, Guatelli-Steinberg D. First systematic assessment of dental growth and development in an archaic hominin (genus, Homo) from East Asia. SCIENCE ADVANCES 2019; 5:eaau0930. [PMID: 30746445 PMCID: PMC6357757 DOI: 10.1126/sciadv.aau0930] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 12/06/2018] [Indexed: 05/28/2023]
Abstract
Several human dental traits typical of modern humans appear to be associated with the prolonged period of development that is a key human attribute. Understanding when, and in which early hominins, these dental traits first appeared is thus of strong interest. Using x-ray multiresolution synchrotron phase-contrast microtomography, we quantify dental growth and development in an archaic Homo juvenile from the Xujiayao site in northern China dating to 161,000-224,000 years or 104,000-125,000 years before present. Despite the archaic morphology of Xujiayao hominins, most aspects of dental development of this juvenile fall within modern human ranges (e.g., prolonged crown formation time and delayed first molar eruption). For its estimated age-at-death (6.5 years), its state of dental development is comparable to that of equivalently aged modern children. These findings suggest that several facets of modern human dental growth and development evolved in East Asia before the appearance of fully modern human morphology.
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Affiliation(s)
- Song Xing
- Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
- CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China
| | - Paul Tafforeau
- European Synchrotron Radiation Facility, CS-40220, 38043 Grenoble Cedex 09, France
| | - Mackie O’Hara
- Department of Anthropology, The Ohio State University, Columbus, OH 43210, USA
| | - Mario Modesto-Mata
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Paseo Sierra de Atapuerca 3, 09002 Burgos, Spain
- Equipo Primeros Pobladores de Extremadura, Casa de la Cultura Rodríguez Moñino, Av. Cervantes s/n, 10003 Cáceres, Spain
- Anthropology Department, University College London, 14 Taviton Street, London WC1H 0BW, UK
| | - Laura Martín-Francés
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Paseo Sierra de Atapuerca 3, 09002 Burgos, Spain
- UMR 5189 PACEA Université de Bordeaux, CNRS MCC, Bordeaux, France
| | - María Martinón-Torres
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Paseo Sierra de Atapuerca 3, 09002 Burgos, Spain
- Anthropology Department, University College London, 14 Taviton Street, London WC1H 0BW, UK
| | - Limin Zhang
- Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | - Lynne A. Schepartz
- HVIRU, School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2193, South Africa
| | - José María Bermúdez de Castro
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Paseo Sierra de Atapuerca 3, 09002 Burgos, Spain
- Anthropology Department, University College London, 14 Taviton Street, London WC1H 0BW, UK
| | - Debbie Guatelli-Steinberg
- Department of Anthropology, The Ohio State University, Columbus, OH 43210, USA
- Department of Anthropology/Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH 43210, USA
- School of Anthropology and Conservation, University of Kent, Canterbury, Kent CT2 7NR, UK
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17
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Kierdorf H, Breuer F, Witzel C, Kierdorf U. Pig enamel revisited – Incremental markings in enamel of wild boars and domestic pigs. J Struct Biol 2019; 205:48-59. [DOI: 10.1016/j.jsb.2018.11.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 11/19/2018] [Accepted: 11/21/2018] [Indexed: 10/27/2022]
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18
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Guatelli-Steinberg D, O'Hara MC, Le Cabec A, Delezene LK, Reid DJ, Skinner MM, Berger LR. Patterns of lateral enamel growth in Homo naledi as assessed through perikymata distribution and number. J Hum Evol 2018; 121:40-54. [DOI: 10.1016/j.jhevol.2018.03.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 03/19/2018] [Accepted: 03/21/2018] [Indexed: 11/24/2022]
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19
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Mahoney P, Miszkiewicz JJ, Chapple S, Le Luyer M, Schlecht SH, Stewart TJ, Griffiths RA, Deter C, Guatelli‐Steinberg D. The biorhythm of human skeletal growth. J Anat 2018; 232:26-38. [PMID: 29023695 PMCID: PMC5735060 DOI: 10.1111/joa.12709] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2017] [Indexed: 12/15/2022] Open
Abstract
Evidence of a periodic biorhythm is retained in tooth enamel in the form of Retzius lines. The periodicity of Retzius lines (RP) correlates with body mass and the scheduling of life history events when compared between some mammalian species. The correlation has led to the development of the inter-specific Havers-Halberg oscillation (HHO) hypothesis, which holds great potential for studying aspects of a fossil species biology from teeth. Yet, our understanding of if, or how, the HHO relates to human skeletal growth is limited. The goal here is to explore associations between the biorhythm and two hard tissues that form at different times during human ontogeny, within the context of the HHO. First, we investigate the relationship of RP to permanent molar enamel thickness and the underlying daily rate that ameloblasts secrete enamel during childhood. Following this, we develop preliminary research conducted on small samples of adult human bone by testing associations between RP, adult femoral length (as a proxy for attained adult stature) and cortical osteocyte lacunae density (as a proxy for the rate of osteocyte proliferation). Results reveal RP is positively correlated with enamel thickness, negatively correlated with femoral length, but weakly associated with the rate of enamel secretion and osteocyte proliferation. These new data imply that a slower biorhythm predicts thicker enamel for children but shorter stature for adults. Our results develop the intra-specific HHO hypothesis suggesting that there is a common underlying systemic biorhythm that has a role in the final products of human enamel and bone growth.
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Affiliation(s)
- Patrick Mahoney
- Human Osteology LabSkeletal Biology Research CentreSchool of Anthropology and ConservationUniversity of KentCanterburyUK
| | - Justyna J. Miszkiewicz
- Skeletal Biology and Forensic Anthropology Research GroupSchool of Archaeology and AnthropologyAustralian National UniversityCanberraACTAustralia
| | - Simon Chapple
- Human Osteology LabSkeletal Biology Research CentreSchool of Anthropology and ConservationUniversity of KentCanterburyUK
| | - Mona Le Luyer
- Human Osteology LabSkeletal Biology Research CentreSchool of Anthropology and ConservationUniversity of KentCanterburyUK
- De la Prehistoire à l'Actuel: CultureEnvironment et Anthropologie (UMR 5199 PACEA)Université de BordeauxPessacFrance
| | | | - Tahlia J. Stewart
- Skeletal Biology and Forensic Anthropology Research GroupSchool of Archaeology and AnthropologyAustralian National UniversityCanberraACTAustralia
| | - Richard A. Griffiths
- Durrell Institute of Conservation and EcologySchool of Anthropology and ConservationUniversity of KentCanterburyUK
| | - Chris Deter
- Human Osteology LabSkeletal Biology Research CentreSchool of Anthropology and ConservationUniversity of KentCanterburyUK
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20
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Guatelli‐Steinberg D, Pampush JD, O'Hara MC, Xing S, McGraw WS, Ferrell RJ. Do Mid‐Crown Enamel Formation Front Angles Reflect Factors Linked to the Pace of Primate Growth and Development? Anat Rec (Hoboken) 2017; 301:125-139. [DOI: 10.1002/ar.23703] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 08/31/2017] [Accepted: 09/01/2017] [Indexed: 11/05/2022]
Affiliation(s)
| | - James D. Pampush
- Department of Exercise ScienceHigh Point UniversityHigh Point North Carolina 27268
| | - Mackie C. O'Hara
- Department of AnthropologyThe Ohio State University, 4034 Smith LaboratoryColumbus Ohio 43210‐1106
| | - Song Xing
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of SciencesInstitute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of SciencesBeijing, 100044
| | - W. Scott McGraw
- Department of AnthropologyThe Ohio State University, 4034 Smith LaboratoryColumbus Ohio 43210‐1106
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21
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Nava A, Coppa A, Coppola D, Mancini L, Dreossi D, Zanini F, Bernardini F, Tuniz C, Bondioli L. Virtual histological assessment of the prenatal life history and age at death of the Upper Paleolithic fetus from Ostuni (Italy). Sci Rep 2017; 7:9427. [PMID: 28842603 PMCID: PMC5572742 DOI: 10.1038/s41598-017-09773-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 07/31/2017] [Indexed: 01/08/2023] Open
Abstract
The fetal remains from the Ostuni 1 burial (Italy, ca 27 ka) represent a unique opportunity to explore the prenatal biological parameters, and to reconstruct the possible patho-biography, of a fetus (and its mother) in an Upper Paleolithic context. Phase-contrast synchrotron X-ray microtomography imaging of two deciduous tooth crowns and microfocus CT measurements of the right hemimandible of the Ostuni 1b fetus were performed at the SYRMEP beamline and at the TomoLab station of the Elettra - Sincrotrone laboratory (Trieste, Italy) in order to refine age at death and to report the enamel developmental history and dental tissue volumes for this fetal individual. The virtual histology allowed to estimate the age at death of the fetus at 31–33 gestational weeks. Three severe physiological stress episodes were also identified in the prenatal enamel. These stress episodes occurred during the last two months and half of pregnancy and may relate to the death of both individuals. Compared with modern prenatal standards, Os1b’s skeletal development was advanced. This cautions against the use of modern skeletal and dental references for archaeological finds and emphasizes the need for more studies on prenatal archaeological skeletal samples.
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Affiliation(s)
- Alessia Nava
- Dipartimento di Biologia Ambientale, Università di Roma "La Sapienza", Rome, Italy. .,Servizio di Bioarcheologia, Museo delle Civiltà, Rome, Italy.
| | - Alfredo Coppa
- Dipartimento di Biologia Ambientale, Università di Roma "La Sapienza", Rome, Italy
| | - Donato Coppola
- Università degli Studi di Bari "Aldo Moro", Bari, Italy.,Museo di Civiltà Preclassiche della Murgia Meridionale, Ostuni, Italy
| | - Lucia Mancini
- Elettra - Sincrotrone Trieste S.C.p.A., Basovizza, Trieste, Italy
| | - Diego Dreossi
- Elettra - Sincrotrone Trieste S.C.p.A., Basovizza, Trieste, Italy
| | - Franco Zanini
- Elettra - Sincrotrone Trieste S.C.p.A., Basovizza, Trieste, Italy
| | - Federico Bernardini
- Centro Fermi, Museo Storico della Fisica e Centro di Studi e Ricerche "Enrico Fermi", Piazza del Viminale 1, 00184, Roma, Italy.,Multidisciplinary Laboratory, The "Abdus Salam" International Centre for Theoretical Physics, Strada Costiera 11, 34014, Trieste, Italy
| | - Claudio Tuniz
- Centro Fermi, Museo Storico della Fisica e Centro di Studi e Ricerche "Enrico Fermi", Piazza del Viminale 1, 00184, Roma, Italy.,Multidisciplinary Laboratory, The "Abdus Salam" International Centre for Theoretical Physics, Strada Costiera 11, 34014, Trieste, Italy.,Centre for Archaeological Science, University of Wollongong, Northfields Ave, Wollongong, NSW 2522, Australia
| | - Luca Bondioli
- Servizio di Bioarcheologia, Museo delle Civiltà, Rome, Italy
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22
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Nava A, Bondioli L, Coppa A, Dean C, Rossi PF, Zanolli C. New regression formula to estimate the prenatal crown formation time of human deciduous central incisors derived from a Roman Imperial sample (Velia, Salerno, Italy, I-II cent. CE). PLoS One 2017; 12:e0180104. [PMID: 28700601 PMCID: PMC5507505 DOI: 10.1371/journal.pone.0180104] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 06/09/2017] [Indexed: 11/28/2022] Open
Abstract
The characterization and quantification of human dental enamel microstructure, in both permanent and deciduous teeth, allows us to document crucial growth parameters and to identify stressful events, thus contributing to the reconstruction of the past life history of an individual. Most studies to date have focused on the more accessible post-natal portion of the deciduous dental enamel, even though the analysis of prenatal enamel is pivotal in understanding fetal growth, and reveals information about the mother's health status during pregnancy. This contribution reports new data describing the prenatal enamel development of 18 central deciduous incisors from the Imperial Roman necropolis of Velia (I-II century CE, Salerno, Italy). Histomorphometrical analysis was performed to collect data on prenatal crown formation times, daily secretion rates and enamel extension rates. Results for the Velia sample allowed us to derive a new regression formula, using a robust statistical approach, that describes the average rates of deciduous enamel formation. This can now be used as a reference for pre-industrial populations. The same regression formula, even when daily incremental markings are difficult to visualize, may provide a clue to predicting the proportion of infants born full term and pre-term in an archaeological series.
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Affiliation(s)
- Alessia Nava
- Dipartimento di Biologia Ambientale, Università di Roma ‘La Sapienza’, Rome, Italy
- Museo delle Civiltà. Museo Nazionale Preistorico Etnografico ‘Luigi Pigorini’, Section of Bioarchaeology, Rome, Italy
| | - Luca Bondioli
- Museo delle Civiltà. Museo Nazionale Preistorico Etnografico ‘Luigi Pigorini’, Section of Bioarchaeology, Rome, Italy
| | - Alfredo Coppa
- Dipartimento di Biologia Ambientale, Università di Roma ‘La Sapienza’, Rome, Italy
| | - Christopher Dean
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Paola Francesca Rossi
- Museo delle Civiltà. Museo Nazionale Preistorico Etnografico ‘Luigi Pigorini’, Section of Bioarchaeology, Rome, Italy
| | - Clément Zanolli
- Laboratoire AMIS, UMR 5288, Université Toulouse III, Toulouse, France
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23
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Modesto-Mata M, García-Campos C, Martín-Francés L, Martínez de Pinillos M, García-González R, Quintino Y, Canals A, Lozano M, Dean MC, Martinón-Torres M, Bermúdez de Castro JM. New methodology to reconstruct in 2-D the cuspal enamel of modern human lower molars. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 163:824-834. [DOI: 10.1002/ajpa.23243] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 01/29/2017] [Accepted: 04/23/2017] [Indexed: 11/11/2022]
Affiliation(s)
- Mario Modesto-Mata
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH); Burgos 09002 Spain
- Equipo Primeros Pobladores de Extremadura, Casa de la Cultura Rodríguez Moñino; Cáceres Spain
| | - Cecilia García-Campos
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH); Burgos 09002 Spain
- Anthropology Department; University College London; London UK
| | - Laura Martín-Francés
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH); Burgos 09002 Spain
- Anthropology Department; University College London; London UK
| | - Marina Martínez de Pinillos
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH); Burgos 09002 Spain
- Anthropology Department; University College London; London UK
| | - Rebeca García-González
- Laboratorio de Evolución Humana, Área de Paleontología, Dpto. de Ciencias Históricas y Geografía, Universidad de Burgos; Burgos Spain
| | - Yuliet Quintino
- Laboratorio de Evolución Humana, Área de Paleontología, Dpto. de Ciencias Históricas y Geografía, Universidad de Burgos; Burgos Spain
| | - Antoni Canals
- Equipo Primeros Pobladores de Extremadura, Casa de la Cultura Rodríguez Moñino; Cáceres Spain
- IPHES Institut Català de Paleoecologia Humana i Evolució Social; C/Marcel.lí Domingo s/n, Campus Sescelades URV (Edifici W3) Tarragona 43007 Spain
- Àrea de Prehistòria Universitat Rovira i Virgili (URV); Tarragona 43002 Spain
| | - Marina Lozano
- IPHES Institut Català de Paleoecologia Humana i Evolució Social; C/Marcel.lí Domingo s/n, Campus Sescelades URV (Edifici W3) Tarragona 43007 Spain
| | - M. Christopher Dean
- Department of Cell and Developmental Biology; University College London; London UK
| | - María Martinón-Torres
- Anthropology Department; University College London; London UK
- Laboratorio de Evolución Humana, Área de Paleontología, Dpto. de Ciencias Históricas y Geografía, Universidad de Burgos; Burgos Spain
| | - José María Bermúdez de Castro
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH); Burgos 09002 Spain
- Anthropology Department; University College London; London UK
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24
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O'Hara M. Applying standard perikymata profiles to Pongo pygmaeus canines to estimate perikymata counts between linear enamel hypoplasias. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 163:213-222. [PMID: 28211566 DOI: 10.1002/ajpa.23194] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 02/03/2017] [Accepted: 02/06/2017] [Indexed: 11/10/2022]
Abstract
OBJECTIVES Recently, studies have interpreted regular spacing and average number of perikymata between dental enamel defects in orangutans to reflect seasonal episodes of physiological stress. To estimate the amount of time between developmental defects (enamel hypoplasia), studies have relied on perikymata counts. Unfortunately, perikymata are frequently not continuously visible between defects, significantly reducing data sets. A method is presented here for estimating the number of perikymata between defects using standard perikymata profiles (SPP) that allow the number of perikymata between all pairs of defects across a tooth to be analyzed. The SPP method should allow the entire complement of defects to be analyzed within the context of an individual's crown formation time. MATERIALS AND METHODS The average number of perikymata were established per decile and charted to create male and female Pongo pygmaeus SPPs. The position of the beginning of each defect was recorded for lower canines from males (n = 6) and females (n = 17). The number of perikymata between defects estimated by the SPP was compared to the actual count (where perikymata were continuously visible). RESULTS The number of perikymata between defects estimated by the SPPs was accurate within three perikymata and highly correlated with the actual counts, significantly increasing the number of analyzable defect pairs. CONCLUSION SPPs allow all defect pairs to be included in studies of defect timing, not just those with continuously visible perikymata. Establishing an individual's entire complement of dental defects makes it possible to calculate the regularity (and potential seasonality) of defects.
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Affiliation(s)
- Mackie O'Hara
- Department of Anthropology, The Ohio State University, Columbus, Ohio, 43210
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25
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Reid DJ, Guatelli-Steinberg D. Updating histological data on crown initiation and crown completion ages in southern Africans. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 162:817-829. [DOI: 10.1002/ajpa.23173] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 12/22/2016] [Accepted: 12/27/2016] [Indexed: 11/05/2022]
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26
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Bocaege E, Hillson S. Disturbances and noise: Defining furrow‐form enamel hypoplasia. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2016; 161:744-751. [DOI: 10.1002/ajpa.23070] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 07/23/2016] [Accepted: 08/01/2016] [Indexed: 12/20/2022]
Affiliation(s)
- E. Bocaege
- Université de Bordeaux, CNRS, MCC, UMR 5199 PACEA, Équipe A3P, Bâtiment B8, Allée Geoffroy St HilairePessac Cedex France
| | - S. Hillson
- Institute of Archaeology, University College LondonLondon,WC1H 0PY UK
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27
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Bocaege E, Humphrey L. Lateral enamel growth in human incisors from Çatalhöyük in Turkey. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2016; 161:656-666. [DOI: 10.1002/ajpa.23069] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 07/27/2016] [Accepted: 08/01/2016] [Indexed: 11/08/2022]
Affiliation(s)
- E. Bocaege
- Université de Bordeaux, CNRS, MCC, UMR 5199 PACEABâtiment B8, Allée Geoffroy StHilaire Pessac Cedex France
| | - L.T. Humphrey
- Department of Earth SciencesNatural History MuseumLondonSW7 5BD UK
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28
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Wang C, Zhao L. Perikymata distribution on anterior teeth of Miocene Lufengpithecus lufengensis from Yunnan, Southern China. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2016; 162:191-196. [PMID: 27670624 DOI: 10.1002/ajpa.23102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 08/11/2016] [Accepted: 09/01/2016] [Indexed: 11/09/2022]
Abstract
OBJECTIVES The present study investigated the distribution of perikymata on anterior teeth of Miocene Lufengpithecus lufengensis so as to broaden the comparative data of developmental variation within and among hominoids. We also compared perikymata-spacing pattern of Lufengpithecus lufengensis with hominins and extant African great apes to understand the implication of dental development. MATERIALS AND METHODS A total of 30 anterior teeth (including 6 I1, 10 I2, and 14 C) of Lufengpithecus lufengensis were examined using a scanning electron microscope and Keyence VHX-600EOS digital microscope to document the number and distribution of perikymata on their labial surfaces. The labial crown height of each tooth was divided into 10 equal deciles and the total perikymata number in each decile was recorded. The mean number of perikymata per millimeter was then calculated for each decile. SPSS statistical software was used to perform analyses of these data, including t-tests for sexual dimorphism and plots showing the perikymata distribution in Lufengpithecus lufengensis. RESULTS Perikymata counts of Lufengpithecus lufengensis in the first three deciles are fewer than the remaining deciles, and with perikymata becoming increasingly more closely packed as growth progresses from cusp to cervix, but decrease in density in the cervical decile. Besides, total labial perikymata counts of canines tend to display very significant sexual dimorphism. DISCUSSION Lufengpithecus lufengensis anterior teeth are more similar in their distribution of labial perikymata to those of Australopithecus than those of other hominins and extant African great apes from previous studies.
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Affiliation(s)
- Cuibin Wang
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lingxia Zhao
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China
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Xing S, Guatelli-Steinberg D, O'Hara M, Wu X, Liu W, Reid DJ. Perikymata distribution in Homo with special reference to the Xujiayao juvenile. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2015; 157:684-93. [PMID: 26059551 DOI: 10.1002/ajpa.22760] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Accepted: 04/20/2015] [Indexed: 11/06/2022]
Abstract
OBJECTIVES This study investigates where the Xujiayao juvenile (I(1) and C(1) ) fits into the array of perikymata distribution patterns found within the genus Homo. MATERIALS AND METHODS In addition to the I(1) and the C(1) of the Xujiayao juvenile, this study includes samples of early Homo (H. rudolfensis and H. erectus), Neandertals, early modern humans (Qafzeh), and recent modern humans from Southern Africa, Newcastle (UK), and North America (Inupiaq, AK). Three sets of analyses were undertaken, including a comparison of percentage of perikymata in the cervical half of the crown, repeated measures analysis of the percentage of total perikymata in each decile, and canonical variates analysis using both total perikymata number and the percentage of perikymata in the cervical half of the crown. RESULTS The I(1) and C(1) of early Homo and Neandertals have a lower percentage of perikymata in the cervical half of the crown than modern human samples. Repeated measures analysis reveals clear distinctions in the distribution of perikymata between the modern human and fossil samples. Canonical variates analysis suggests greater differences between modern humans and the fossil samples than within the fossil samples, and classifies the Xujiayao teeth among modern humans. DISCUSSION The present study further clarifies variation of perikymata distribution patterns within the genus Homo. The perikymata distribution of the Xujiayao juvenile tends to be more similar to that of modern humans than to either early Homo or Neandertals.
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Affiliation(s)
- Song Xing
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China
| | | | - Mackie O'Hara
- Department of Anthropology, the Ohio State University, Columbus, OH, 43210
| | - Xiujie Wu
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China
| | - Wu Liu
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China
| | - Donald J Reid
- Department of Anthropology, the George Washington State University, Washington, DC, 20052
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Mahoney P. Dental fast track: Prenatal enamel growth, incisor eruption, and weaning in human infants. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2014; 156:407-21. [DOI: 10.1002/ajpa.22666] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Revised: 10/28/2014] [Accepted: 10/28/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Patrick Mahoney
- Human Osteology Research Lab.; School of Anthropology and Conservation, University of Kent; Canterbury CT2 7NR UK
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31
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Dean MC, Liversidge HM, Elamin F. Combining radiographic and histological data for dental development to compare growth in the past and the present. Ann Hum Biol 2014; 41:336-47. [DOI: 10.3109/03014460.2014.922614] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Kierdorf H, Breuer F, Richards A, Kierdorf U. Characterization of Enamel Incremental Markings and Crown Growth Parameters in Minipig Molars. Anat Rec (Hoboken) 2014; 297:1935-49. [DOI: 10.1002/ar.22951] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 04/09/2014] [Accepted: 04/11/2014] [Indexed: 11/12/2022]
Affiliation(s)
- Horst Kierdorf
- Department of Biology; University of Hildesheim; Germany
| | | | | | - Uwe Kierdorf
- Department of Biology; University of Hildesheim; Germany
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Horvath JE, Ramachandran GL, Fedrigo O, Nielsen WJ, Babbitt CC, St Clair EM, Pfefferle LW, Jernvall J, Wray GA, Wall CE. Genetic comparisons yield insight into the evolution of enamel thickness during human evolution. J Hum Evol 2014; 73:75-87. [PMID: 24810709 DOI: 10.1016/j.jhevol.2014.01.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 10/29/2013] [Accepted: 01/09/2014] [Indexed: 12/29/2022]
Abstract
Enamel thickness varies substantially among extant hominoids and is a key trait with significance for interpreting dietary adaptation, life history trajectory, and phylogenetic relationships. There is a strong link in humans between enamel formation and mutations in the exons of the four genes that code for the enamel matrix proteins and the associated protease. The evolution of thick enamel in humans may have included changes in the regulation of these genes during tooth development. The cis-regulatory region in the 5' flank (upstream non-coding region) of MMP20, which codes for enamelysin, the predominant protease active during enamel secretion, has previously been shown to be under strong positive selection in the lineages leading to both humans and chimpanzees. Here we examine evidence for positive selection in the 5' flank and 3' flank of AMELX, AMBN, ENAM, and MMP20. We contrast the human sequence changes with other hominoids (chimpanzees, gorillas, orangutans, gibbons) and rhesus macaques (outgroup), a sample comprising a range of enamel thickness. We find no evidence for positive selection in the protein-coding regions of any of these genes. In contrast, we find strong evidence for positive selection in the 5' flank region of MMP20 and ENAM along the lineage leading to humans, and in both the 5' flank and 3' flank regions of MMP20 along the lineage leading to chimpanzees. We also identify putative transcription factor binding sites overlapping some of the species-specific nucleotide sites and we refine which sections of the up- and downstream putative regulatory regions are most likely to harbor important changes. These non-coding changes and their potential for differential regulation by transcription factors known to regulate tooth development may offer insight into the mechanisms that allow for rapid evolutionary changes in enamel thickness across closely-related species, and contribute to our understanding of the enamel phenotype in hominoids.
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Affiliation(s)
- Julie E Horvath
- North Carolina Museum of Natural Sciences, Nature Research Center, Raleigh, NC 27601, USA; Department of Biology, North Carolina Central University, Durham, NC 27707, USA; Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA; Duke Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA
| | | | - Olivier Fedrigo
- Duke Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA
| | | | - Courtney C Babbitt
- Duke Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA; Department of Biology, Duke University, Durham, NC 27708, USA
| | | | | | - Jukka Jernvall
- Institute for Biotechnology, University of Helsinki, Helsinki, Finland
| | - Gregory A Wray
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA; Duke Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA; Department of Biology, Duke University, Durham, NC 27708, USA
| | - Christine E Wall
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.
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McFarlane G, Littleton J, Floyd B. Estimating striae of Retzius periodicity nondestructively using partial counts of perikymata. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2014; 154:251-8. [DOI: 10.1002/ajpa.22501] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 02/14/2014] [Indexed: 11/06/2022]
Affiliation(s)
- Gina McFarlane
- Department of Anthropology; The University of Auckland; Auckland 1142 New Zealand
| | - Judith Littleton
- Department of Anthropology; The University of Auckland; Auckland 1142 New Zealand
| | - Bruce Floyd
- Department of Anthropology; The University of Auckland; Auckland 1142 New Zealand
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Elhechmi I, Braga J, Dasgupta G, Gharbi T. Accelerated measurement of perikymata by an optical instrument. BIOMEDICAL OPTICS EXPRESS 2013; 4:2124-2137. [PMID: 24156069 PMCID: PMC3799671 DOI: 10.1364/boe.4.002124] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 08/01/2013] [Accepted: 08/04/2013] [Indexed: 06/02/2023]
Abstract
The proposed device considerably reduces the measuring time of important microscopic features of tooth crown surfaces. The instrumentation is accompanied by a computer program to analyse the results. Tooth enamel is formed by ameloblasts, which demonstrate daily secretory rhythms developing tissue-specific structures known as cross striations, and longer period markings that are referred as striae of Retzius. These striae correspond to linear structures on the enamel surface. This newly developed optical measuring instrument can automatically, precisely and accurately record the number and periodicity of perikymata on the dental crown. Furthermore it can characterize the variability in periodicity of perikymata in hominids. The depth of field can be extended as desired by taking several images with different focus positions and combining them into a single composite image that contains all regions fully focused.
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Affiliation(s)
- Imen Elhechmi
- Nanomedicine Lab, Imagery and Therapeutics, EA 4662 Université de Franche-Comté, 25030 Besançon cedex,
France
- CHU Jean Minjoz, 3 Boulevard Alexandre Fleming, 25030 Besançon cedex,
France
| | - José Braga
- Laboratoire d’Anthropobiologie (UMR 5288 CNRS) Université de Paul Sabatier Toulouse III, 31073 Toulouse cedex 3,
France
| | - Gautam Dasgupta
- Civil Engineering & Engineering Mechanics, Columbia University, NY, New York, NY 10027,
USA
| | - Tijani Gharbi
- Nanomedicine Lab, Imagery and Therapeutics, EA 4662 Université de Franche-Comté, 25030 Besançon cedex,
France
- CHU Jean Minjoz, 3 Boulevard Alexandre Fleming, 25030 Besançon cedex,
France
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36
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Kierdorf H, Kierdorf U, Frölich K, Witzel C. Lines of evidence-incremental markings in molar enamel of Soay sheep as revealed by a fluorochrome labeling and backscattered electron imaging study. PLoS One 2013; 8:e74597. [PMID: 24040293 PMCID: PMC3765360 DOI: 10.1371/journal.pone.0074597] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 08/06/2013] [Indexed: 01/17/2023] Open
Abstract
We studied the structural characteristics and periodicities of regular incremental markings in sheep enamel using fluorochrome injections for vital labeling of forming enamel and backscattered electron imaging in the scanning electron microscope. Microscopic analysis of mandibular first molars revealed the presence of incremental markings with a daily periodicity (laminations) that indicated successive positions of the forming front of interprismatic enamel. In addition to the laminations, incremental markings with a sub-daily periodicity were discernible both in interprismatic enamel and in enamel prisms. Five sub-daily increments were present between two consecutive laminations. Backscattered electron imaging revealed that each sub-daily growth increment consisted of a broader and more highly mineralized band and a narrower and less mineralized band (line). The sub-daily markings in the prisms of sheep enamel morphologically resembled the (daily) prisms cross striations seen in primate enamel. Incremental markings with a supra-daily periodicity were not observed in sheep enamel. Based on the periodicity of the incremental markings, maximum mean daily apposition rates of 17.0 µm in buccal enamel and of 13.4 µm in lingual enamel were recorded. Enamel extension rates were also high, with maximum means of 180 µm/day and 217 µm/day in upper crown areas of buccal and lingual enamel, respectively. Values in more cervical crown portions were markedly lower. Our results are in accordance with previous findings in other ungulate species. Using the incremental markings present in primate enamel as a reference could result in a misinterpretation of the incremental markings in ungulate enamel. Thus, the sub-daily growth increments in the prisms of ungulate enamel might be mistaken as prism cross striations with a daily periodicity, and the laminations misidentified as striae of Retzius with a supra-daily periodicity. This would lead to a considerable overestimation of crown formation times in ungulate teeth.
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Affiliation(s)
- Horst Kierdorf
- Department of Biology, University of Hildesheim, Hildesheim, Germany
| | - Uwe Kierdorf
- Department of Biology, University of Hildesheim, Hildesheim, Germany
| | - Kai Frölich
- Department of Biology, University of Hildesheim, Hildesheim, Germany
- Tierpark Arche Warder e.V., Warder, Germany
| | - Carsten Witzel
- Department of Biology, University of Hildesheim, Hildesheim, Germany
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Dean MC, Cole TJ. Human life history evolution explains dissociation between the timing of tooth eruption and peak rates of root growth. PLoS One 2013; 8:e54534. [PMID: 23342167 PMCID: PMC3544739 DOI: 10.1371/journal.pone.0054534] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 12/12/2012] [Indexed: 12/20/2022] Open
Abstract
We explored the relationship between growth in tooth root length and the modern human extended period of childhood. Tooth roots provide support to counter chewing forces and so it is advantageous to grow roots quickly to allow teeth to erupt into function as early as possible. Growth in tooth root length occurs with a characteristic spurt or peak in rate sometime between tooth crown completion and root apex closure. Here we show that in Pan troglodytes the peak in root growth rate coincides with the period of time teeth are erupting into function. However, the timing of peak root velocity in modern humans occurs earlier than expected and coincides better with estimates for tooth eruption times in Homo erectus. With more time to grow longer roots prior to eruption and smaller teeth that now require less support at the time they come into function, the root growth spurt no longer confers any advantage in modern humans. We suggest that a prolonged life history schedule eventually neutralised this adaptation some time after the appearance of Homo erectus. The root spurt persists in modern humans as an intrinsic marker event that shows selection operated, not primarily on tooth tissue growth, but on the process of tooth eruption. This demonstrates the overarching influence of life history evolution on several aspects of dental development. These new insights into tooth root growth now provide an additional line of enquiry that may contribute to future studies of more recent life history and dietary adaptations within the genus Homo.
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Affiliation(s)
- M Christopher Dean
- Cell and Developmental Biology, University College London, Gower Street, London, United Kingdom.
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