Anthropology and Dentistry

Key points

  • Anthropology is the study of human variation and evolution; physical anthropology focuses on biological and anatomical aspects of human variation.
  • Dental anthropology is a branch of physical anthropology that focuses on the development, evolution, and variability of teeth and related orofacial structures.
  • Forensic odontology (or forensic dentistry) is the branch of forensic anthropology that focuses on identification and analysis of human teeth in a legal context.
Introduction

Anthropology is the study of human variation and evolution, and encompasses all aspects of human life, sociocultural, cognitive, and biological.  This academic field, which transcends the boundaries of the natural and the social sciences, intersects with dentistry and the oral health sciences, as well as other medical sciences, in a number of different ways.

The Four Fields of Anthropology

Anthropology is traditionally divided into four distinct but often overlapping fields: social (or cultural) anthropology, physical (or biological) anthropology, linguistics, and archaeology.

As the study of biological human evolution, physical anthropology integrates a number of sciences, including anatomy, evolutionary biology, and genetics, to name a few.  Since humans are social organisms who have created complex cultures, it is also closely integrated with cultural anthropology, often linked by behavioral studies of living primates, and archaeology, the study of human societies from the past.1

While archaeology is generally considered the study of cultural remains of past societies, it often finds itself somewhere between cultural and physical anthropology, particularly when human remains are involved.  The study of human remains associated with archaeological sites is referred to as bioarchaeology or osteoarchaeology within a wider cultural context, or osteology when referring to the study of the skeletal remains themselves.  Further, when human or primate remains belong to a period preceding human societies or are ancient enough to have fossilized, the study of such fossils is called paleoanthropology. Ancient Homo sapiens and closely related taxa such as Neanderthals (Homo neanderthalensis) and the Denisovans span this period between paleontology and archaeology, not only because many of their remains have fossilized, but because these species mark the beginnings of human culture.

Physical anthropologists and osteologists analyze skeletal remains to determine or estimate a range of characteristics like sex, race, age at death, injuries and pathologies, stature, and even occupation.  Histological and molecular analyses can help determine geographic residence or diet of an individual.  These analyses can be used to interpret population relationships and affinities, lifestyles, community health, and migration patterns of ancient communities as well as to build phylogenetic, behavioral and ecological theories of fossil species.  In forensic anthropology, these analyses may be used to help determine the identity of an individual and help estimate time or manner of death.

Traditionally, data from analyzed skeletal material (measurements and coordinate data, non-metric traits, pathological lesions) has been recorded into databases or published as supplemental material for use by other researchers.  Advances in technology have now allowed 3D scanning of bones and other materials which can be analyzed by computer software or printed as high-resolution replicas and physically studied.

Dental anthropology

Anthropology has a long history of using teeth to investigate the relationships of people throughout time and place.  Dental anthropology is a distinct subfield of physical anthropology, attempting to answer questions about the evolution and diversity of humans and our ancestors by analyzing variations in the morphology and dimensions of human teeth, as well as micro- and molecular analysis of dental components.

Teeth in Anthropology

Teeth are abundant in the fossil record,2 and are the prevalent fossil specimens among primates and hominoids.3-5  Tooth enamel is the hardest tissue in the body, being 96% dense inorganic hydroxyapatite,6 which makes teeth highly resistant to taphonomic and diagenetic change, unlike bone which is readily destroyed and easily absorbs materials from the surrounding matrix.7, 8  Additionally, teeth provide the benefit of allowing analysis in a “non-destructive, cost-efficient, and straightforward manner.”9  Thus, the value of the dentition in anthropological analyses lies in its “preservability, observability, variability, and heritability.”10

Teeth are an integral part of physical anthropology, not only because they are a durable part of the human body and last indefinitely in the fossil record, but because of what morphological variation (metric and non-metric) as well as pathologies can tell us about past peoples.  Tooth size and shape are under strong genetic control,11, 12 and development is “relatively independent”13 of the more plastic (and thus environmentally influenced) orofacial tissues,13, 14  making teeth more genetically informative than their skeletal counterparts.9  This means that dental morphological data may be used as a proxy for genetic information, particularly when studying population affinities and evolutionary relationships.  Teeth are also an excellent reservoir of ancient DNA.15

Identification and Nomenclature of Teeth in Anthropology

Anthropologists often use a dental identification system that differs from clinical dentistry.  A common method in anthropology is to label teeth according to category and number; I for incisor, C for canine, P for premolar, and M for molar; superscript numbers referring to the tooth in sequence indicate upper and subscript lower; R and L would indicate right or left side, respectively.  Small case represents the deciduous dentition.16-19  Using this method, a permanent maxillary right central incisor would be RI1 and its deciduous mandibular counterpart Ri1.

Because the anthropological terminology takes evolution into account, unlike the clinical sciences, the human premolars (bicuspids) are usually labeled P3 and P4, since the first and second premolars were lost in humans throughout evolutionary history.18  Alternatively, dental anthropologists sometimes use the FDI system, in which each tooth is assigned a two-digit code representing the quadrant and sequential number of the tooth; the upper right central incisor would thus be labeled 11.  Deciduous dentition quadrants are labeled 5-8.

Mammals can be classified according their “dental formula,” the number of each category of tooth per quadrant.  Humans, for example, are classified as having the 2-1-2-3 pattern: 2 incisors, 1 canine, 2 premolars, and 3 molars in each quadrant.

Evolution of the human dentition

One of the characteristics of early mammals is the development of a more complex dentition than undifferentiated, conical reptilian teeth. A transitory haplodont stage arose in which these singular conical teeth merged, becoming cusps, and differentiating into several tooth types.19, 20  These cusps are still exhibited in the mamelons and labial grooves of the incisors, while posterior teeth have developed distinct cusps.19  Mammals eventually developed a triconodont stage with noticeably different types of teeth (heterodonty), corresponding to modern incisors, canines, premolars and molars, which began with the Permian and Triassic era therapsids, reptiles that included the cynodonts, which would eventually lead to mammals.  Later mammals developed the triangular-cusp pattern to the molars characteristic of extant carnivores (tritubercular), and eventually the formation of opposing occlusion in the quadritubercular (four-cusped) stage,19, 20 and the five-cusped pattern typical in humans and apes.20

Modern eutherian mammals typically shed only one set of teeth in their lifetime (diphyodonty) as opposed to the reptilian and earlier condition of the constant replacement of teeth (polyphyodonty) and are characterized, generally, by a 3-1-4-3 permanent dentition; it has been more common throughout evolution for species to lose teeth rather than to gain teeth.  The differentiation of types of teeth allows a more generalized or varied diet, resulting in the ability to exploit a wider variety of environments.  The reduction of the snout in primates further allows a wider range of movement during occlusion, again allowing a greater dietary variety, or omnivory.1

Functional Morphology of Teeth

The dentition of mammals can be described as consisting of two distinct functional modules, the anterior (incisors and canines) and the posterior (premolars and molars) dentitions, which appear to evolve independently.21  The size and shape of the teeth are associated with diet and function, with the anterior module evolved for grasping and the posterior module for chewing.  Incisors allow cutting and help move food into the mouth.6, 19, 22  Relatively large incisors are characteristic of frugivores, for dehusking fruits and seeds,22 while sharp and pointed canines can grasp or hold prey.  Relatively long canine size is typically associated with aggression, and is common in predatory animals, as well as with sexual dimorphism and rigid social hierarchies in primates.  Premolars seem to provide a dual function between the canines and molars, both helping to grasp as well as to grind and shear.6  Primates (monkeys, apes, and humans) have evolved a more generalized (i.e., less sharp) postcanine crown morphology as opposed to many mammals that have specialized posterior teeth adapted to specific diets.1  Leaf-eaters tend to have relatively high molar cusps to aid chewing and processing;22 the molars of herbivorous ungulates, although generally flat, are so specialized to this task, with such deep and numerous furrows into the dentine, as to make it difficult to recognize molariform cusps.20

Miocene Apes (22.5 – 5 million years ago, [mya])

The evolution of modern humans can be traced back to the Miocene epoch (22.5-5 mya) and the proliferation of a number of ape species, or hominoids, one of which would eventually lead to the direct ancestors of modern humans during the Plio-Pleistocene period (~5 mya-12 kya).  The radiation of ape taxa during the Miocene throughout Africa, Europe and Asia makes it difficult to assign a last common ancestor (LCA) to the descendant hominid line, and several fossil species exhibit features that characterize later hominids.

The form of the modern human dentition begins to become recognizable in the Miocene apes,19 which, although already sharing the 2-1-2-3 dental formula characteristic of Old World Monkeys, lose the “canine honing complex,” an interlocking of the canines with the adjacent mandibular premolar (P3) which continually sharpens the long canines during occlusion.23  Reduction of canine length is evident early in Miocene Africa with Proconsul africanus, and in the later African fossil species Sahelanthropus tchadensis, Orrorin tugenensis, and Ardipithecus kadabba,4, 23 as well as the European Oreopithecus bambolii.24  The European Dryopithecus is especially noted for its Y-5 molar pattern describing the grooves among the five mandibular M1 cusps,1, 18 a pattern typical in modern great apes (pongids) and common among humans.1, 10

Despite the radiation of Miocene apes throughout the Old World, research consensus is that the LCA of modern humans and other hominids most likely originated in Sub-Saharan Africa around 6 mya,23, 25 after the last fossil evidence of apes in Europe around 9 mya.25

Pliocene Hominids (5 – 2.5 mya)

Canine size continued to reduce in many of the Miocene apes, particularly by the time Ardipithecus ramidus shows up in the early Pliocene, just over 4 mya, exhibiting a noticeably “less threatening”4 canine, thinner molar enamel (intermediate between later hominids and modern chimpanzees), and low crown morphology in its posterior teeth, morphology that is more consistent with later hominids than with extant apes.4

Traditionally, Pliocene fossil bipedal hominids had been categorized as the Australopithecines, with a “robust” group, exhibiting more primitive features, and a “gracile” group, believed to have led to modern Homo species.  In recent years, the robust Australopithecines are typically referred to under the genus name Paranthropus, suggested to be a possible descendent of a more primitive Australopithecine.23  Gracile Australopithecus species continued the reduced canine size evident in Ardipithecus ramidus (a possible ancestor) but also show a distinct increase in enamel thickness in the posterior teeth, a condition referred to as postcanine megadontia.26, 27  Australopithecus and Paranthropus lower molars typically have 5 main cusps, and Paranthropus molars show a distinct ‘flare’ or bulge of the crown.19

The Transition to Homo

A number of specimens from the Plio-Pleistocene period (from around 5 mya to 12 kya) seem to bridge gaps between typical Australopithecines and later Homo, many regarded as Homo habilis, and have been found largely in Eastern Africa.  Homo erectus, possibly a descendant of Homo habilis, left the African continent and specimens have been found throughout Asia and into Europe from approximately 1 mya.

Among the key characteristics of fossil Homo species is a significant reduction of facial prognathism, along with a more parabolic dental arch (as opposed to the “rectangular” arch of Miocene and living apes), as well as the loss of a maxillary diastema between the lateral incisor and canine, common in apes and the Australopithecines.1, 19, 28 While both Australopithecus and early Homo both exhibit relatively rectangular crown shape, in contrast to an oval shape in Paranthropus, Homo postcanine crown sizes began to reduce and are characterized by a larger M1 relative to posterior molars and more variable cusp patterns (M3 is particularly variable), and eventual reduction in root size.28  Variability in molar crown morphology drives investigations into human population history and relationships.3

In Homo erectus the anterior dentition shows distinctive incisor shoveling,1 particularly in the Eurasian specimens,29 and exhibits a variety that is better represented by frequencies in regional populations, similar to those of modern humans.30  Eurasian and African specimens of this period can be distinguished by these complexes of traits according to functional module.  The anterior dentition of Eurasian species is characterized by “mass additive” traits, with more complex and robust features such as shoveling, cingular derivations and mesial canine ridges, and strong labial convexity, while the posterior dentition of Eurasian specimens shows reductions in robusticity and simplification of cusp patterns.29, 31  Conversely, in the African specimens, the anterior dentitions are characterized by lower frequencies of such mass additive, robust features and the posterior dentition feature more mass additive traits, including a higher frequency of accessory cusps and complex occlusal patterns.29, 31

Anthropological analyses of teeth

Estimating age at death

Development and Eruption Sequence

The regular pattern, sequence, and timing of development and eruption of the dentition provides arguably the most accurate method of estimating age at death of children and adolescents.  From the time that the first deciduous teeth begin to emerge at approximately 6 months, to the eruption of the M3 at around age 18 years, several patterns emerge than can easily categorize a child or adolescent into general age groups.18, 32  The eruption sequence of the molars from M1 to M3 occurs typically at 6, 12, and 18 years, respectively, which can allow one to easily categorize subadults through visual examination.  This method is particularly useful for subadults when estimated dental age can be checked against the associated skeleton’s symphyseal age (i.e., age determination based upon the fusing of the ends of bones).33

A seminal chart of dental development was published by Schour and Massler in JADA in 1941, which categorized eruption patterns into 22 stages starting from 5 months in utero to 35 years.34  A number of other charts followed in years to come using data from more populations, including Ubelaker’s 1989 method and the more recent London Atlas of Human Tooth Development and Eruption.35, 36

Tooth Wear and Attrition

“Our ancestors wore the enamel off of their teeth,”6 so levels of occlusal wear have been used to estimate age in adult skeletons from pre-medieval and non-Western populations.18, 37  A number of studies have shown that premodern skeletons can be aged reliably by wear patterns,16, 18 but these studies likely underestimate individuals over 50 years of age, due to the nature of attrition and tooth loss over the lifespan.18

Population histories and affinities

Teeth have been used as a proxy for genetic studies, due to their high heritability, when estimating population relationships and affinities.9  There is geographic and historical variation in tooth dimensions, overall size, number of teeth (hypo- and hyperdontia) and crown and root morphology.38  Thus, the distribution frequencies of these metric and non-metric traits can contribute to the determination of an individual’s ancestry.

Metric Dental Variation

Crown dimensions (particularly mesiodistal and buccolingual) vary among human populations, but cannot be explained by a simple geographic or environmental explanation.  There has been a distinct reduction in crown sizes throughout human evolution,11 but there is wide intraregional variation in size among modern populations: Australian natives have the largest total crown size among modern humans, along with Neanderthals and Homo erectus,11, 38-40  while the smallest crowns are distributed as widely as the Lapps of Scandinavia and the San Bushmen of southern Africa.11, 38  One study has found that on a global level, overall tooth size indicates large geographic population distinctions (but with wide intra-regional variation), with native populations of Australia having the largest teeth, followed by native North American and Sub-Saharan Africans; East Asians, Indians, and Europeans were found to have the smallest teeth.40  Despite the high heritability of tooth dimensions, overall tooth size may be affected by prenatal and developmental stress.41

Non-Metric Dental Traits

Non-metric traits, particularly accessory cusps, fissure patterns and incisor shoveling have been shown to be more indicative of population history and relationships, and frequencies of such traits vary according to major racial groupings.11, 39  The tubercle of Carabelli, or Carabelli’s cusp, is a supplemental tubercle, or fifth cusp, along the mesiolingual cusp of maxillary molars ranging in expression from a small furrow to a full cusp.11, 19  It is common among Europeans (up to 85%) and least common among Pacific Islanders.

Seminal research on nonmetric dental trait complexes have distinguished between Asian and Caucasian dental complexes and have further divided Asian traits into a Sinodont pattern of “trait intensification” among Southeast Asians, Pacific Islanders, and the Jomon.39  Additionally, three major groups of the native peoples of the Americas can be distinguished by their expression of a three-rooted mandibular first molar: Eskimo-Aleut, Na-Dene, and “others.”39

Incisor shoveling, described as a measurably deep lingual fossa, as well as double-shoveling, are found more frequently in East/Northeast Asia and the Americas, and least frequently in North Africa and Sub-Saharan Africa.42  As predicted by a number of anthropological studies, Sub-Saharan Africans show the highest level of intraregional variation in non-metric dental traits,42 which is consistent with the Out-of-Africa theory of modern human origins.41

Diets and health

Teeth are particularly vulnerable to physical and biological trauma, unlike other skeletal elements, because they come into direct contact with the external environment.  Investigating pathological or deliberate alterations to human teeth can tell us not only about the individual being examined, but the customs, diets, and health of a population.  Modifications to teeth, particularly dental work, are tremendously valuable in forensic identification.

Occupational, cultural, and lifestyle habits can be determined from physical modifications to tooth structure, from intentional evulsion to observable grooves from tooth-picking.11, 18  Grooves appearing on posterior teeth have also been attributed to the removal of sinewy material from animal prey.2, 11  Intentional mutilation of teeth—commonly the anterior teeth—for cosmetic or cultural purposes has been practiced for several thousands of years in the Americas, Africa, and parts of Asia.2

Diets can be inferred by patterns of tooth wear.18, 38  Generally, hunter-gatherers exhibit more occlusal wear than agriculturalists, particularly in incisors which were often used to process hides.  Agriculturalists that used stone grinding tools to process grains show increased pitting43 and heavily abraded posterior teeth.38, 44  While tooth wear (attrition and abrasion) has drastically decreased since the Middle Ages, there has been a concomitant increase in caries, non-carious cervical lesions, and erosion,43 resulting from dietary as well as food-processing changes.

The advent of agriculture and reliance on fermentable carbohydrates has led to a drastic increase in dental caries,18  which became a “major health scourge” after 1500.38  In the past, social status and sex may have affected the distribution of caries because of an unequal distribution of high-sugar foods18; in modern times, females consistently exhibit higher caries rates than males,38, 45 with explanatory hypotheses ranging from more frequent snacking to hormonal changes during pregnancy.45, 46

Calculus, or calcified plaque, is commonly found in archaeological remains in both supragingival and subgingival forms.11, 20, 44  Calculus is easily observable and is indicative of periodontal disease, while periodontitis can be observed by porosity or pitting of the alveolar bone or the presence of abscesses.43, 44  Periodontal disease has been found throughout antiquity and as far back as 3 mya in a specimen of Australopithecus africanus.44  Presence of nutritional deficiencies such as that indicated by scurvy has been associated with periodontal disease in historical studies, as have cultural practices such as cocoa-leaf and betel-nut chewing.43, 44

The enamel matrix of teeth is secreted by ameloblasts in a circadian rhythm, leaving microscopic lines in enamel structure called cross striations, which form circaseptan bands referred to as brown striae of Retzius.8, 41  The rhythmic slowing-down of the production of ameloblasts evident on the surface of the tooth produces perikymata; periods of pathology or other nutritional disturbances or periods of stress produce noticeable striae often referred to as Wilson bands8, 11 or linear enamel hyposplasia (LEH).39, 41, 43  These hypoplastic lines can tell us that a period of environmental stress, illness, or nutritional deficiency occurred at a certain point in an individual’s life and can indicate a marked period of stress or famine for a community.39, 41, 43, 47  LEH may be difficult to assess in modern populations, in which teeth are “heavily abraded by toothbrushing.”48

Trace analysis

An additional result of the incremental deposition of the enamel matrix during tooth development is that components of hydroxyapatite crystals are subject to replacement by elements to which they are exposed during mineralization; the resulting striations can be analyzed histologically to determine presence of trace elements or isotopes, that can be used to reconstruct dietary lifestyle changes, geographic movements, stressful environmental periods, or exposure to toxicity in an individual’s life.49, 50  In particular, lead and strontium isotopes carry heavy geographic signals, which can be used to determine an individual’s geographic origin or migrations.7, 51

Barium/calcium (Ba/Ca) ratios have been used to investigate weaning times among primates.  Barium is highly concentrated in mother’s milk and, like lead, follows calcium pathways; nursing infants absorb barium from mother’s milk much more easily than from other dietary sources.52, 53  Research on Ba/Ca ratios from the shed teeth of orangutans found that after an initial drop in barium levels between 16 and 18 months, the ratio varied cyclically with seasonal availability of fruits and other foods. This suggests that during lean times, the growing orangutans supplement their diet with mother’s milk, extending the weaning period well into childhood, sometimes as long as into the 9th year.52 This finding corresponds to other research on primates in marginal environments, and sheds light on the causes of the shortened weaning time of modern and archaic humans. A 2013 study of a juvenile Neanderthal tooth showed a drop in barium after 7.5 months, falling to prenatal levels at 1.2 years, which is well within the range of weaning practices of modern humans.53

ADA policies relating to dental anthropology

Dental Radiographs for Victim Identification (Trans.2003:364; 2012:442)

Resolved, that the ADA promote to practicing dentists the importance of providing, as permitted by law, radiographs, images and records on patients of record that are requested by a legally authorized entity for victim identification and which will be returned to the dentist when no longer needed, and be it further

Resolved, that copies of these records should be retained by dentists as required by law.

American Dental Association

Adopted 2003; Amended 2012; Reviewed 2017

Study of Human Remains for Forensic and Other Scientific Purposes (Trans.2002:421)

The American Dental Association supports the preservation and study of human remains for forensic, scientific or other research purposes, provided that ethical, legal, cultural and religious considerations are addressed and the dignity and privacy of the individual are respected.


American Dental Association
Adopted 2002; Reviewed 2017

Dental Identification Teams (Trans.1994:654; 2012:441) 

Resolved, that the American Dental Association supports the American Board of Forensic Odontologists’ recommendation to develop dental identification teams that can be mobilized at times of need for local or regional mass fatality incidents (MFI), and be it further

Resolved, that state and regional ID teams receive initial and ongoing training by forensic odontologists experienced in MFI response.


American Dental Association
Adopted 1994; Amended 2012; Reviewed 2012

Dental Identification Efforts (Trans.1985:588)

Resolved, that the ADA encourage dental societies, related dental organizations and the membership to participate in efforts designed to assist in identifying missing and/or deceased individuals through dental records and other appropriate mechanisms.


American Dental Association
Adopted 1985; Reviewed 2017

Uniform Procedure for Permanent Marking of Dental Prostheses (Trans.1979:637; 2012:448)

Resolved, that the American Dental Association support the use of uniform methods of marking dental prostheses for identification purposes, and be it further

Resolved, that a system of dental prosthetic identification should meet the following criteria:

  1. Patient specific identification, used with patient consent, should be incorporated into the dental prosthesis.
  2. The identification should be legible and permanent.
  3. The procedure for applying the identification markings should be clinically safe, economically practical and cosmetically acceptable.


American Dental Association
Adopted 1979; Amended 2012; Reviewed 2017

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Last Updated: April 24, 2020

Prepared by:

Department of Scientific Information, Evidence Synthesis & Translation Research, ADA Science & Research Institute, LLC.


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