DENTAL ANTHROPOLOGY HILLSON PDF

About this title Teeth are among the best sources of evidence for both identification purposes and studies of demography, biological relationships, and health in ancient human communities. This text introduces the complex biology of teeth and provides a practical guide to all essential aspects of dental anthropology, including excavation, identification, microscopic study, and tooth age determination. Dental Anthropology is a concise yet comprehensive resource designed for students and researchers in anthropology and archaeology. Book Description: Providing a practical guide to all essential aspects of dental anthropology, this text introduces the complex biology of teeth, including excavation, identification, microscopic study, and tooth age determination. It is a concise yet comprehensive resource for students and researchers. The author has introduced a wealth of information served up into a highly digestible format.

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Richard Scott Dr. For organisms that use teeth to process food, tooth loss is directly related to survival — lose your teeth, lose your life Lucas Cultural buffering during the later stages of human evolution removed this dramatic relationship, but dental conditions are nonetheless dictated by long-term evolution, not recent cultural advances.

For that reason, human teeth, along with the teeth of all vertebrates, were formed under the influence of natural selection. For animals that eat meat, the dentition has slicing, dicing, and piercing elements with minimal emphasis on crushing and grinding teeth. Conversely, browsers and grazers process large quantities of plant foods and thereby have teeth devoted primarily to crushing and grinding, with little need for slicing and dicing.

For omnivores, including most primates, the dentition processes a more varied assortment of foods so the teeth are not as specialized as those of carnivores or herbivores Ungar Teeth are comprised of four different tissues: enamel, dentine, cementum, and pulp.

Enamel covers the dentine which in turn covers the pulp chamber that contains blood vessels and nerves. Cementum anchors the tooth roots in the sockets of the upper and lower jaws. This basic observation has many ramifications. For example, teeth are used to process food so their shape and size are strongly influenced by diet. Because teeth come together while masticating food objects, the enamel eventually wears down, exposing the dentine, and finally the pulp.

If wear is not too rapid, secondary dentine forms to protect the pulp from exposure to environmental variables, including oral microbiota that lead to infection. Another plus to the hardness of enamel is preservability. Teeth are often the most abundant remnant of the skeletal system in the archaeological and fossil record. Because tooth size and shape are linked to diet and survival, the dentition is under strong genetic control.

Minor variations are tolerated, such as accessory cusps, styles, ridges, and roots Fig. Still, minor changes that accrue over broad spans of time ultimately lead to major changes, providing a classic example of the relationship between microevolution and macroevolution emphasized by the modern synthetic theory of evolution. While dramatic changes occur over millions of years, as seen for example in the dentition of horses as they shifted from browsing to grazing Peyer , other changes are remarkably conservative.

For example, the adaptive zone of felids is defined broadly by the elements of hunting strategy ambush and pursuit , activity period nocturnal , and sociality solitary , but the subdivision of this zone by prey size resulted in a wide variation in felid body size 4 kg to over kg.

Despite variation in body size, including tooth size, the teeth of a small cat are basically identical to those of a lion or tiger from a morphological standpoint. One can see the same pattern in canids where body and tooth size vary considerably but tooth number and morphology are identical in most respects Hillson The point is this: if you maintain the same diet e.

With few exceptions, humans have the same number of deciduous teeth 20 and adult teeth 32 and the same types of teeth incisors, canines, premolars, molars , along with many commonalities in morphological details. Beyond that, human teeth are very similar to hominoid teeth, making it obvious that the great apes are our closest biological relatives Swindler However, human teeth can be distinguished from hominoid teeth in several ways.

The most important difference is in the size of the canines. The general primate dental pattern includes large, projecting canines that are primarily used in male-male competition for access to valued resources. These canines form a shearing complex with the lower first premolar which assumes a sectorial shape elongated front to back, or mesiodistally. For proper articulation of the two jaws, there is a space, or diastema, between the upper lateral incisors and canines to accommodate the lower canine.

Paleoanthropologists often note canine reduction, homomorphic lower premolars, and lack of a diastema as hallmarks of early hominids. All of these traits are linked to a single trait — canine size. Hominoids and many other primates also differ from hominins in the form and relative size of the incisors. Humans have relatively small anterior teeth incisors and canines that are vertically implanted in the jaws. Monkeys and apes, by contrast, have broad, spatulate incisors that are disproportionately large compared to the cheek teeth premolars, molars , and these are set obliquely in the jaw rather than vertically Agrawal et al.

This difference revolves around the degree to which different organisms manipulate food with their anterior teeth. Animals who emphasize incisal preparation of foodstuffs have broad incisors that jut out from the upper jaw at an angle. Hominoids also show variation in enamel thickness on individual cusps, along with better developed cingula; orangs and some chimps also exhibit many crenulations small ridges on the premolars and molars. Despite differences, the overall similarity in morphology is striking.

Definition Dental anthropology is a subdiscipline of physical anthropology that focuses on the use of teeth to resolve anthropological problems.

Teeth exhibit a wide array of variables, ranging from those largely controlled by genes to those largely dictated by environment. Dental variables under genetic control include crown and root morphology and size, along with tooth number i.

Dental variables that reflect environmental factors include tooth crown wear and chipping, caries, abscesses, periodontal disease, calculus, and linear enamel hypoplasia. Richard Scott Dental Anthropology SpringerReference Anthropological questions focusing on teeth include issues of population origins and relationships tooth morphology, size, number , diet and behavior attrition, crown chipping, tooth-tool use , health caries, abscesses, periodontal disease, calculus , and developmental stress hypoplasia, asymmetry.

Fields that involve significant elements of dental anthropology include bioarchaeology, forensic anthropology, human biology, paleoanthropology, and primate paleontology. Key Issues Population History For the past years, dental researchers have been aware of the fact that human populations from different geographic regions varied in tooth size, crown and root morphology, and tooth number. By , we knew that Australian aboriginals had the largest teeth in the world while Bushmen and Lapps had the smallest.

After , the number of papers using dental characters to assess population affinity grew exponentially.

Turner II developed many of the ranked standards for making observations Turner et al. He also examined thousands of Asian and Asian-derived samples to develop the Sinodont-Sundadont dichotomy in Asia and the three wave migration model for the peopling of the Americas from a northeast Asian Sinodont ancestor Greenberg et al.

Other researchers are using dental morphology to address issues ranging from regional microdifferentiation to global patterns of variation. Genetics and Development For teeth to be useful in the evaluation of phylogeny and population relationships, dental variables should be under strong genetic control. Although normal dental variation cannot be reduced to gene frequencies, twin and family studies have shown that traits defined by size or morphology are highly heritable Fig.

The environment can contribute to dental development but genes play a stronger role. Morphological traits, which are present or absent with variable degrees of expression when present, are quasicontinuous variants with polygenic modes of inheritance. Missing third molars, at one time thought to be a simple Mendelian trait, are also quasicontinuous.

Over the course of the past two decades, research in evo-devo evolution and development has advanced our understanding of the genetic-developmental basis of tooth size and shape. Going beyond the identification of individual variables associated with tooth size and shape, Jernvall and Jung describe four types of characters based on developmental principles; that is, characters of initiation, termination, cusp shape, and configuration.

These different developmental patterns are tied provisionally to size and presence of the hypocone and short cusps along with crown diameters, crown relief, and relative cusp size, etc. To tie different crown and root traits to regulatory genes will advance the analysis of tooth characters in both hominid fossils and recent human populations. With use, teeth wear down. Patterns of wear can be used to infer both diet and dietary behavior. Hunter-gatherers often use their anterior teeth to process hides, so the incisors in particular wear down more rapidly than the molars and premolars.

This is less evident in early agriculturalists that show less wear on the anterior teeth but more wear on the cheek teeth because of abrasives introduced by grinding stones in processing grains. Agriculturalists also exhibit a steeper wear plane on the cheek teeth compared to hunter-gatherers, a pattern that may reflect a reduction in food toughness tied to the use of grinding stones and cooking Smith In addition to attrition and abrasion which are characterized by incremental change and a smooth polished surface, teeth can also fracture.

As a brittle material with limited plasticity, enamel can be chipped when subjected to excessive force. Oral Health Some of the most common diseases in earlier human populations were those that impacted the oral cavity. The most widely studied of these pathologies is dental caries Fig. Richard Scott Dental Anthropology SpringerReference with complex carbohydrates, including foliage and tubers. One exception is Kabwe Rhodesian Man who suffered from multiple carious lesions and associated abscesses well over , years ago.

Even during medieval times in Europe, caries occurred primarily between the teeth interstitial rather than on the crown surfaces coronal. With the spread of refined sugars after CE , caries became a major health scourge.

An abscess almost invariably develops at the root apex when the pulp chamber is exposed to the oral environment. This exposure can be the result of extremely rapid crown wear, coronal or interstitial caries, significant crown fractures, or periodontal disease.

When oral bacteria invade the bloodstream, an individual is subject to a generalized infection. Many individuals in the archaeological record had active abscesses at death. To what extent such abscesses can be implicated in mortality is difficult to assess.

Caries and abscesses can both lead to antemortem tooth loss. Individuals who retain their teeth throughout life live at least a decade longer than those who lose one or more teeth. Developmental Stress Teeth are the calcified end product of an original protein template. As environmental and genetic exigencies can impact the calcification of this template, there are markers that leave an imprint on teeth that researchers use to evaluate stress-related growth disturbances.

The most commonly used marker is linear enamel hypoplasia LEH that takes the form of circumferential lines around a tooth Fig. Although all teeth can exhibit LEH, the anterior teeth show it most clearly. Hypoplastic lines can vary in degree of expression and number. Because teeth develop within relatively limited time periods, some authors evaluate timing in terms of the biological age of the subjects.

In Midwest Native Americans, these lines often occurred between the ages of two and four, leading researchers to conclude they were coincident with weaning infants off breast milk and transitioning them to a maize gruel lacking essential proteins Goodman et al. As the major triggers for LEH are nutritional deprivation or disease, interpretation of the lines always depends on context.

Populations can exhibit the same frequency and severity of lines but for altogether different reasons. In northern hunting populations, living in small, scattered communities with few endemic diseases, the trigger for LEH development is primarily seasonal food shortage. By contrast, in agricultural communities, periodic food shortages are less of an issue than diseases associated with crowding, including cholera, diphtheria, and typhus. Focus is primarily on bite marks left on the skin of victims of violent crimes.

Most bite mark experts come from the field of dentistry, not anthropology. Dental anthropologists nonetheless have much to contribute in forensic contexts. With isolated teeth, one can estimate minimum number of individuals and provide a reasonable estimate of age. Individual identification can sometimes be made on the basis of unusual if not unique patterns of occlusion, especially those evident on the anterior teeth.

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