Dental Anthropology

An international European research collaboration led by scientists at the Max Planck Institute for Evolutionary Anthropology reports evidence for a rapid developmental pattern in a 100,000 year old Belgian Neanderthal (Homo neanderthalensis).

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A new report details how the team used growth lines both inside and on the surfaces of the child’s teeth to reconstruct tooth formation time and its’ age at death.

Scientists found differences in the duration of tooth growth in the Neanderthal when compared to modern humans, with the former showing shorter times in most cases. This faster growth resulted in a more advanced pattern of dental development than in fossil and living members of our own species (Homo sapiens).

The Scladina juvenile, which appears to be developmentally similar to a 10-12 year old human, was estimated to be in fact about 8 years old at death. This pattern of development appears to be intermediate between early members of our genus (e.g., Homo erectus) and living people, suggesting that the characteristically slow development and long childhood is a recent condition unique to our own species.

Neanderthal life history, or the timing of developmental and reproductive events, has been under great debate during the past few decades. Across primates, tooth development, specifically the age of molar eruption, is related to other developmental landmarks such as weaning and first reproduction.

Scientists have previously found evidence to both support and refute the idea that Neanderthals grew up differently than our own species. In this new study, researchers used information from the inside of a molar tooth, coupled with data from micro-computed tomography (micro-CT), as well as evidence of developmental stress on the outsides of tooth crowns and roots.

This yields the first chronology, or time sequence, for Neanderthal tooth growth, which differs from living humans. The Scladina Neanderthal grew teeth over a shorter period of time, and has more teeth erupted (present in the mouth), than similarly-aged fossil or living humans (Homo sapiens).

This suggests that other aspects of physical development were likely more rapidly achieved as well, implying significant differences in the behaviour or social organization of these ancient humans.

Journal reference: Tanya M. Smith, Michel Toussaint, Donald J. Reid, Anthony J. Olejniczak, Jean-Jacques Hublin, Rapid Dental Development in a Middle Paleolithic Belgian Neanderthal, Proceedings of the National Academy of Sciences USA December 2007

The long period of development leading up to a modern human’s adulthood arose relatively late in our evolutionary history, according to an analysis of growth patterns in fossil teeth in the 6 December issue of the journal Nature, written by Christopher Dean of University College, London, and colleagues including Alan Walker, distinguished professor of anthropology and biology at Penn State.

“One of the things that sets modern humans apart from the living great apes is our long period of growth and development,” Dean explains. “While humans take a good 18 to 20 years to grow up, other primate species like chimpanzees and gorillas take just 11 or 12 years.” A supporting article, written by Jacopo Moggi-Cecchi of the University of Florence in Italy, is included in the “News and Views” section of the journal. The research was designed to determine when the prolonged growth period we have today arose during our long evolutionary history.

“Dental development is a good measure of overall growth and development,” says Walker, who pioneered the study of living primates as a basis for the analysis of fossils and was one of the first to use scanning electron microscope studies of fossil teeth. “Teeth grow in an incremental manner like trees or shells, preserving a record of their growth with daily marks along the prisms that make up the enamel.” By making thin sections of modern and fossil teeth, the researchers were able to count the daily incremental markings within the enamel of humans, apes, and fossil “hominin” species in the human lineage in order to calculate and compare their rates of enamel formation.

“Of the 13 fossil tooth fragments we studied–both those attributed to the earliest australopith hominins that lived roughly between 4 and 1 million years ago, and those of the earliest members of our own Homo genus that lived about 1.5 million years ago–none showed the slower pattern of modern human enamel growth,” says Walker, who in 1984 was a key member of the team that discovered a juvenile skeleton in Kenya from one of the earliest species in the Homo genus, Homo erectus. “We found that the first dental evidence for a modern human-like growth period appears much more recently, in a Neanderthal fossil that lived about 120,000 years ago.”

The results are surprising because researchers had expected that Homo erectus–the first fossil human ancestor to show a suite of modern human-like characteristics including body proportions, body weight, and small teeth and jaws–would show evidence of a modern human-like growth period. However, because the brain in Homo erectus was still not as large as a modern human’s and because a long growth period is linked with the time needed to grow and learn to use a large brain, the researchers say these findings are compatible with predictions that could be made on the basis of brain size alone.

As part of their research, the scientists used the incremental growth markings to calculate the formation times of individual teeth as a clue in the solution to another mystery about the age at death of the Homo erectus fossil found in Kenya.

“Using these tooth-formation times, we can speculate about the age at which key teeth emerged into the mouth in Homo erectus,” Dean explains. “It seems likely that the first permanent molar tooth, which erupts at around 6 years in modern humans and about 3.5 years in apes, erupted between 4 and 4.5 years in Homo erectus. Previously, most people accepted this boy was close to 11 or 12 years of age, but now it seems more likely he was closer to 8 years of age, which is a surprise because he was already 5 feet 3 inches tall.”

“It seems our prolonged period of growth and development may be a more recent evolutionary acquisition that arose in step with our comparatively recent development of a larger, modern, human-sized brain,” Walker says.

This research was supported by the Royal Society and the Leverhulme Trust.

This internship project will be directed by Cidália Duarte at the Instituto Português de Arqueologia, located in Belem, Lisbon, Portugal.  The internship will focus on the skeletal remains from the Final Neolithic-Chalcolithic dolmens (burial tombs) of Monte Abraão, Estria and Pedra dos Mouros that were excavated in the late 19th and later housed in the Geological Museum though never thoroughly studied. The information obtained from these studies will be used in the doctoral dissertation of Rui Boaventura who is studying the dolmens in the region of Lisbon.
 
 
  Students will be given more latitude and independent work loads in this internship program and are expected to be already familiar with the basic principals and methodologies of osteology and/or dental anthropology.  While other skeletal material will be reviewed and studied, the bulk of the
 
  
 
 
 collections to be considered are the dental remains. This internship will deal primarily with dental anthropology and morphology, the description and classification of teeth as well as the various pathologies that are evident in teeth.
 
 
 Students will begin by washing, cataloging and inventorying the various collections which are comprised of hundreds of teeth.  Within individual collections, or dolmen, students will be instructed how to properly study, classify and analyze the skeletal remains in order to answer such questions as the quantity of individuals in each tomb, their age and sex as well as any evident pathologies
 

Dental nonmetric traits were scored on eighty-nine deciduous teeth that were recovered from the ancient Mesopotamian site of Tell Leilan (mid-third millennium BC) in northeastern Syria. Notable features of the dentition include a mild form of shoveling on the maxillary incisors, presence of Carabelli’s trait in 71% of maxillary second molars, and a rarity of accessory cusps on the mandibular second molars. Although based on a small sample, this study is intended as a contribution to the very limited amount of published data on deciduous dental morphology.

This study, based on 518 sets of dental models of secondary school children and adults from Kelantan and Perak State, aimed to characterize normal odontometric variation within and between Malaysian populations. The sample included the four main ethnic groups living on the Malaysian Peninsula; Malays, Chinese, Indians and Jahai. Mesiodistal and buccolingual crown dimensions of all permanent teeth, except third molars, were measured to an accuracy of 0.01mm with automatic digital callipers. Tooth size was larger in males than females for more than 75% of the variables in Malays, Chinese and Indians. The magnitude of sexual dimorphism in buccolingual diameters tended to be greater than for mesiodistal diameters in all groups studied. Our findings confirm that there is considerable variation within and between Malaysian populations in permanent tooth size and this variability needs to be taken into consideration when undertaking anthropological and forensic investigations.

The Kircchoff’s model considers to the West of Mesoamérica like a marginalized region, recent works have contributed to contrast this hypothesis. Information of the dental morphology variation has been found on Mesoamerican populations. This article gathers the greatest number of populations of Pre-Hispanic Mexico. In the following work, samples are provided by eight West Mesoamerican groups and compared with other six samples listed in the bibliography for Nuclear Mesoamerica. For the bio-distance and clustering analysis, the Dental Anthropology System of the Arizona State University (DAS/ASU) has been used. The correlation between the geographical and genetic distance is illustrated in a genetic barriers map among populations. The results are discussed on the basis of history and dynamics of populations, taking into account other anthropological disciplines. In Early Periods there was few isolation between West and Nuclear Mesoamerican populations, and in Late Period there was no real genetic barrier or genetic discontinuity

The objective of this study is to evaluate the mandibular angle and to analyze the relationship of the angle to the gender; height and breadth of the ramus of the mandible so as to study its role in the anthropological diagnosis. The angles, height and breadth of the ramus of adult dry human mandibles of both the sexes were measured using a mandibulometer. The values obtained were analyzed statistically. The present study showed a statistically significant difference in the angle as well as height of the ramus of the mandible between both the sexes. The mean mandibular angle of Indian population when compared to that of European population was found to be lower by 9 degrees. The findings of this study might be useful in providing anthropological data that can also be used in dental and medical practice. However, the Indian mandible cannot be used for sexual dimorphism as is usual in anthropological work, whereas it appears to possess important unfavourable anatomic factors that may predispose the individuals to difficult laryngoscopy or intubation.

Teeth are an excellent material in living and non-living populations for anthropological, genetic, odontologic and forensic investigations. To define the morphometric criteria for teeth in Haryana, the present study has been conducted in 102 patients (Male: 52, Female: 50) in the age group of 17-28 years. It was seen that statistically significant sexual dimorphism exist in the mandibular canine and intercanine distance weather measurements are taken on casts or intra-orally. It is concluded that whenever the mesio-distal diameter of mandibular canine is greater than 7.2 mm, the probability of sex being male is hundred percent. If the intercanine distance is greater than 25 mm, the age of male and female is more than 14 and 12 years in male and female respectively.

Very little is known about the role of chewing of tobacco and areca nut on the oral dental hard tissues. An attempt was made to observe the effects of these materials on dental hard tissues. A total of 365 subjects (168 chewers and 197 non chewers) were enrolled randomly. The chewers were addicted to different chewing preparations. Examination of teeth was carried out clinically and dental attrition and staining were observed. The results indicated significantly higher frequency of dental attrition, sensitivity and staining of teeth among chewers than non-chewers. Further, analysis of data indicated a significantly higher attrition score for molar and anterior teeth among chewers with respect to non-chewers. The attrition score was also higher for premolar but this was not statistically significant with respect to non-chewers. The chewing these materials also leads to staining of teeth, which was also significantly higher among chewers.  Chewing areca nut and tobacco have the adverse effect on dentine structure and function as more dentine attrition and sensitivity was observed among chewers than non-chewers.

Sexual variation in the human skeleton and dentition is of great concern for both anthropologists and odontologists. Assessment of variation in dental size gives a clue about the behavior of a population, and also differences between the sexes. The purpose of this study was to analyze dental dimensions and sexual variation in Iranians and develop forensic techniques to identify human remains from the teeth when any other technique is not available or not reliable. The study is composed of 100 stone casts of Azad University dental students from Iranian population of either sex ranging age from 18 to 24 years. Bucco-lingual breadths from 14 teeth (I1 through M2 of the maxilla and mandible) are taken from the left side and analyzed using the discriminant function statistics. Results of the study revealed that males exceeded females significantly (P < 0:001) in dimensions. Stepwise discriminant function statistics suggested that upper M2 and lower C are the most contributory teeth to the function. In conclusion this research supports earlier studies that sexual dimorphism is population specific.