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The analysis of dental remains is a valuable tool to archaeologists. Teeth are hard, highly mineralised and chemically stable, so therefore preserve well and are one of the most commonly found animals remains. [1] Analysis of these remains also yields a wealth of information. It can not only be used to determine the sex [2] and age of the individual [3] whose mandibular or dental remains have been found, but can also shed light on their diet, pathology, [4] and even their geographic origins through isotope analysis. [5]
As a result, dental analysis is applied to both the recent and long-dead. It is a crucial part of forensic anthropology in terms of identifying the deceased, [6] and can be applied to archaeological remains to learn about an individual from a burial, or track larger changes in diet of a population if more data is available. [4]
The methods to estimate age based on dentition are divided into two groups; the methods based on the development and growth of teeth that are applied to infants, children and juveniles, and the methods that are based on changes to dentition after formation which is used to estimate the age of adults. [7]
It is easier to estimate the age of an individual using their dental remains during infancy and childhood than it is during adulthood since the emergence of teeth and their development in young people provide good and relatively reliable indicators of age. [8] Since teeth eruption follows a pattern, with the eruption of deciduous teeth occurring after birth to the end of infancy at the age of two, and permanent teeth erupting between the ages of five and fourteen, [7] observing which teeth are erupted and developing in a mandible, or whether a tooth is deciduous or permanent in isolated remains, can reveal the age of the individual. This evaluation of tooth eruption can be done by viewing images of the dental remains via radiographs, MRIs, and CT scans. [9]
Among adults with fully developed dentition, numerous techniques have been developed for age estimation by looking at various characteristics including periodontosis, cementum apposition, tooth-root translucency, [3] root resorption, secondary dentine deposition and the attrition of the occlusal surface. [10] The tooth-root translucency method was pioneered in the 1990s and involves taking two measurements of a tooth when viewing it under a light, and then placing the values into a formula to gain an age estimation. [3] Another common method involves counting the number of alternating light and dark bands in the cementum. [3] Such methods that are based on post-formation changes rely more on microscopic observations. [9] A more holistic approach can be taken to assess the overall wear of the teeth too, for example using the Brothwell chart of 1963. [11] Assessing teeth wear like this is common since it is a more reliable indicator of age than signs of wear in bones. [12]
The simplest methods of estimating the sex of an individual are based on common differences in size between the teeth of male and female individuals. The dimensions measured are the mesiodistal and buccolingual dimensions, and are commonly applied to the mandibular canines which show the greatest sexual dimorphism, but premolars and some molars and maxillary incisors also show size differences between males and females. [13] Other morphological differences can be used to support sex estimation, for example by comparing the frequencies of discrete traits such as the deflecting wrinkle of the lower first molars and the distal accessory ridge of the canines. [14] One potential problem with these forms of morphological identification, aside from the fact that the variation in teeth is continuous, is that the possibility of mistakes increases in cases where the morphology of the teeth has been altered by taphonomic processes. [15]
More advanced methods for sex determination involve DNA analysis, in which DNA extracted from dental pulp can be amplified using the polymerase chain reaction and then analysed. However this is a destructive process that tends to destroy the sample, either via the cryogenic grinding, or the opening of the root canals to extract the pulp. [16] Protein enamel analysis is another molecular technique in which the different signatures of amelogenin in males and female individuals provides the basis of sex estimation. [17]
Since dental apparatus comes into direct contact with the foods consumed, teeth provide direct and some of the best evidence for the diet that an individual ate in life. [18] The analysis of features on the teeth and jaws such as cavities, hypoplasias and striations can all reveal the sorts of foods that were consumed. [19]
Starting with cavities, which are usually the result of high-sugar and high-carbohydrate diets, so the prevalence of cavities in dental remains suggests the existence of such foods in the diet. For example, dental analysis of skeletal remains of hunter-gatherers in Morocco from 15,000 -13,700 years BP revealed that a diet that was high in starchy foods may have caused the high rates of tooth decay seen in the population. [20] When inferring a high-carbohydrate and sugar diet from the prevalence of cavities, it is necessary to consider other factors that may increase the severity of dental diseases such as the immune system of the individual. If it is already impaired by other infections then cavities and signs of dental diseases will be more prevalent, and thus such features should not automatically be attributed to just more sugar consumption. [21]
Enamel hypoplasia is the result of disturbances in the enamel, and can take the form of thinner or missing areas of enamel, lines, furrows and pits. [22] Most enamel hypoplasias are the result of external, negative, environmental conditions, like poor nutrition and diseases, and as a result they can tell us about the lifestyle of the individual. [23] Metabolic disorders resulting from poor diet or disease have a particularly significant effect on enamel, and a range of other non-specific diseases can cause the feature, such as measles, diphtheria and deficiency in vitamin A, D and C. [24] The identification of enamel hypoplasias is best done with microscopic analysis of tooth thin sections. [25] The position of the hypoplasia on the tooth can also tell you when the childhood stress that caused the disruption in the tooth enamel occurred by measuring the distance from the hypoplasia to the cemento-enamel junction [23] since the enamel does not remodel once formed. [22]
When there is a large sample size, tracking changes in dentition over many generations can show how diets and lifestyles were changing, and this line of inquiry has been successful in many cases. An example of one that looked at enamel hypoplasia was conducted by Starling and Stock who looked at the hypoplasias of five populations in the Nile Valley from different time periods. The population from 13,0000 to 15,000BCE had fewer hypoplasias that the proto-agriculturalist population of 5000-4000 BCE, which demonstrates that the period in which early agriculture emerged was one with high levels of stress. [26] In a similar vein, dental remains of a population from Roman Cibalae were analysed and revealed a significantly higher frequency of enamel hypoplasias in females than males. This has been interpreted as showing that the women in the area were worse off in terms of diet and disease. [27]
Some hypoplasias are related to inherited conditions too. [23] Stress is not the sole cause. Additionally, when hypoplasias do occur the severity of the hypopplasia does not directly correlate to the severity of stress - characteristics such as tooth morphology, enamel structure, and developmental timing and speed are all factors as well. [28] As a result, it is necessary to use multiple teeth types to infer the stress that an individual may have experienced.
Tooth wear is another key feature of dental remains that can be analysed to infer past diets. Wear that is the result of natural contact between upper and lower teeth is called attrition, and wear that is the result of external objects like food coming into contact with the teeth is called abrasion. [29] The wear is further subdivided into that which is studied and seen with the naked eye (macrowear), and that which is studied and seen with a microscope (microwear). [30] This microwear constitutes the pits and scratches seen on the enamel surface, and different patterns of microwear can occur as a result of different diets. [31]
Some of the most conspicuous macrowear constitutes chips in the teeth which is seen in irregular surfaces, in contrast to crown wear which is the more gradual and incremental. [32] Chipping usually occurs when the enamel cannot withstand the force exerted by the jaws, and as a result a fracture can arise in the teeth, particularly when a foreign element is between the teeth. Causes, therefore, include inclusions within food, such as a bit of grit or bone, or more commonly today actions like biting your nails or chewing a pen. Injuries and force can also cause dental trauma like this. [33] In relation to inferring diet, chipping can suggest inclusions within a meal, potentially bits of loose grindstone making its way into the finished cereal, and studies have also shown that hunter-gatherers have more chipping on their molars, whilst agricultural communities have the highest frequencies of chippings on the incisors. [34]
Moving to microwear, pits are microscopic cracks in the structure of the enamel that are the result of hard particles being driven into the tooth surface that cause tiny bits of the enamel to fracture off. Harder foods require more force when chewing to grind down the foods, and as a result they result in more pits whilst the consumption of softer foods creates more scratches on the enamel. [31] Tough but soft foods also create scratches as opposing surfaces slide past each other during mastication. [35] When analysing microwear the most common technique used to involve the use of an electron microscope, but these days white light confocal microscopes can be used to observe the enamel on the tooth surface. [31]
At the site of Abu Hureyra in Syria, scanning electron microscope photos were taken of teeth from Mesolithic and Neolithic layers and the patterns of microwear were analysed. This revealed that the food eaten in the Neolithic was harder and coarser, reflecting a switch from the small grained seeds eaten in the Mesolithic to the large grained cereals that were dominant in the Neolithic, as well as the switch from roots and wild grains to domesticated cereals. [36] There is also a change between the 2a and 2b Neolithic layers at Abu Hureyra, with teeth from the later layers showing less attrition, potentially due to a change in food preparation, or potentially due to the shift to the consumption of more domesticated meats. [37]
Stable isotope analysis is the final category of dental analysis for diet that can be considered, as the usual techniques of isotope analysis applied to bones to infer diet, can also be applied to teeth. Carbon, nitrogen, oxygen and strontium are the most commonly studied. [38] A common technique is to distinguish a C3-based diet from a C4-based diet based on the ratio of the carbon isotopes 13C and 12C that are found within the hydroxyapatite. [39] Consumption of plants that use the C3 pathway in photosynthesis, like most temperate zone vegetation, incorporate less 13C into their tissues than plants that use the C4 pathways, including many tropical and savanna grasses. [40] The use of these stable isotopes have shown the increasing importance of millet and rice at a Neolithic site in Shandong, China. [41] Nitrogen isotopes are also commonly studied as they can suggest an agricultural or marine-based diet since the ratio of 15N to 14N increases higher up the food chain. [42]
Strontium and oxygen isotope ratios in hydroxyapatite have been used to study the geographical origins and movements of ancient people too. Strontium isotope ratios vary in different types of rock and soil, so there are differences in isotopic ratios in plants and animals living in regions with different geology as a result. [41]
The possibilities of using dental calculus for analysis has been increasingly recognised and it can be used for both stable isotope and DNA analysis. One of its main benefits is that it is a secondary material and not an inherent part of the skeletal remains, and as a result people may be less hesitant to use it for such analysis, since those techniques destroy and damage the sample. [43] Additionally, you can get both macrofossils and microfossils trapped in calculus; fragments of cereals, fibres and even phytoliths can all be found in calculus, making it a useful tool for reconstructing past diets [44]
Human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. As such, they are considered part of the human digestive system. Humans have four types of teeth: incisors, canines, premolars, and molars, which each have a specific function. The incisors cut the food, the canines tear the food and the molars and premolars crush the food. The roots of teeth are embedded in the maxilla or the mandible and are covered by gums. Teeth are made of multiple tissues of varying density and hardness.
Tooth enamel is one of the four major tissues that make up the tooth in humans and many animals, including some species of fish. It makes up the normally visible part of the tooth, covering the crown. The other major tissues are dentin, cementum, and dental pulp. It is a very hard, white to off-white, highly mineralised substance that acts as a barrier to protect the tooth but can become susceptible to degradation, especially by acids from food and drink. In rare circumstances enamel fails to form, leaving the underlying dentin exposed on the surface.
Forensic dentistry or forensic odontology involves the handling, examination, and evaluation of dental evidence in a criminal justice context. Forensic dentistry is used in both criminal and civil law. Forensic dentists assist investigative agencies in identifying human remains, particularly in cases when identifying information is otherwise scarce or nonexistent—for instance, identifying burn victims by consulting the victim's dental records. Forensic dentists may also be asked to assist in determining the age, race, occupation, previous dental history, and socioeconomic status of unidentified human beings.
Tooth whitening or tooth bleaching is the process of lightening the color of human teeth. Whitening is often desirable when teeth become yellowed over time for a number of reasons, and can be achieved by changing the intrinsic or extrinsic color of the tooth enamel. The chemical degradation of the chromogens within or on the tooth is termed as bleaching.
The term bioarchaeology has been attributed to British archaeologist Grahame Clark who, in 1972, defined it as the study of animal and human bones from archaeological sites. Redefined in 1977 by Jane Buikstra, bioarchaeology in the United States now refers to the scientific study of human remains from archaeological sites, a discipline known in other countries as osteoarchaeology, osteology or palaeo-osteology. Compared to bioarchaeology, osteoarchaeology is the scientific study that solely focus on the human skeleton. The human skeleton is used to tell us about health, lifestyle, diet, mortality and physique of the past. Furthermore, palaeo-osteology is simple the study of ancient bones.
Dental fluorosis is a common disorder, characterized by hypomineralization of tooth enamel caused by ingestion of excessive fluoride during enamel formation.
Early childhood caries (ECC), formerly known as nursing bottle caries, baby bottle tooth decay, night bottle mouth and night bottle caries, is a disease that affects teeth in children aged between birth and 71 months. ECC is characterized by the presence of 1 or more decayed, missing, or filled tooth surfaces in any primary tooth. ECC has been shown to be a very common, transmissible bacterial infection, usually passed from the primary caregiver to the child. The main bacteria responsible for dental caries are Streptococcus mutans and Lactobacillus. There is also evidence that supports that those who are in lower socioeconomic populations are at greater risk of developing ECC.
Archaeolemur is an extinct genus of subfossil lemurs known from the Holocene epoch of Madagascar. Archaeolemur is one of the most common and well-known of the extinct giant lemurs as hundreds of its bones have been discovered in fossil deposits across the island. It was larger than any extant lemur, with a body mass of approximately 18.2–26.5 kg (40–58 lb), and is commonly reconstructed as the most frugivorous and terrestrial of the fossil Malagasy primates. Colloquially known as a "monkey lemur," Archaeolemur has often been compared with anthropoids, specifically the cercopithecines, due to various morphological convergences. In fact, it was even misidentified as a monkey when remains were first discovered. Following human arrival to Madagascar just over 2000 years ago, many of the island’s megafauna went extinct, including the giant lemurs. Radiocarbon dating indicates that Archaeolemur survived on Madagascar until at least 1040-1290 AD, outliving most other subfossil lemurs.
Enamel hypoplasia is a defect of the teeth in which the enamel is deficient in quantity, caused by defective enamel matrix formation during enamel development, as a result of inherited and acquired systemic condition(s). It can be identified as missing tooth structure and may manifest as pits or grooves in the crown of the affected teeth, and in extreme cases, some portions of the crown of the tooth may have no enamel, exposing the dentin. It may be generalized across the dentition or localized to a few teeth. Defects are categorized by shape or location. Common categories are pit-form, plane-form, linear-form, and localised enamel hypoplasia. Hypoplastic lesions are found in areas of the teeth where the enamel was being actively formed during a systemic or local disturbance. Since the formation of enamel extends over a long period of time, defects may be confined to one well-defined area of the affected teeth. Knowledge of chronological development of deciduous and permanent teeth makes it possible to determine the approximate time at which the developmental disturbance occurred. Enamel hypoplasia varies substantially among populations and can be used to infer health and behavioural impacts from the past. Defects have also been found in a variety of non-human animals.
Mesowear is a method, used in different branches and fields of biology. This method can apply to both extant and extinct animals, according to the scope of the study. Mesowear is based on studying an animal's tooth wearing fingerprint. In brief, each animal has special feeding habits, which cause unique tooth wearing. Rough feeds cause serious tooth abrasion, while smooth one triggers moderate abrasion, so browsers have teeth with moderate abrasion and grazers have teeth with rough abrasion. Scoring systems can quantify tooth abrasion observations and ease comparisons between individuals.
Odontometrics is the measurement and study of tooth size. It is used in biological anthropology and bioarchaeology to study human phenotypic variation. The rationale for use is similar to that of the study of dentition, the structure and arrangement of teeth. There are a number of features that can be observed in human teeth through the use of odontometrics.
Tooth pathology is any condition of the teeth that can be congenital or acquired. Sometimes a congenital tooth disease is called a tooth abnormality. These are among the most common diseases in humans The prevention, diagnosis, treatment and rehabilitation of these diseases are the base to the dentistry profession, in which are dentists and dental hygienists, and its sub-specialties, such as oral medicine, oral and maxillofacial surgery, and endodontics. Tooth pathology is usually separated from other types of dental issues, including enamel hypoplasia and tooth wear.
Tricho–dento–osseous syndrome (TDO) is a rare, systemic, autosomal dominant genetic disorder that causes defects in hair, teeth, and bones respectively. This disease is present at birth. TDO has been shown to occur in areas of close geographic proximity and within families; most recent documented cases are in Virginia, Tennessee, and North Carolina. The cause of this disease is a mutation in the DLX3 gene, which controls hair follicle differentiation and induction of bone formation. All patients with TDO have two co-existing conditions called enamel hypoplasia and taurodontism in which the abnormal growth patterns of the teeth result in severe external and internal defects. The hair defects are characterized as being rough, course, with profuse shedding. Hair is curly and kinky at infancy but later straightens. Dental defects are characterized by dark-yellow/brownish colored teeth, thin and/or possibly pitted enamel, that is malformed. The teeth can also look normal in color, but also have a physical impression of extreme fragility and thinness in appearance. Additionally, severe underbites where the top and bottom teeth fail to correctly align may be present; it is common for the affected individual to have a larger, more pronounced lower jaw and longer bones. The physical deformities that TDO causes become more noticeable with age, and emotional support for the family as well as the affected individual is frequently recommended. Adequate treatment for TDO is a team based approach, mostly involving physical therapists, dentists, and oromaxillofacial surgeons. Genetic counseling is also recommended.
Changes to the dental morphology and jaw are major elements of hominid evolution. These changes were driven by the types and processing of food eaten. The evolution of the jaw is thought to have facilitated encephalization, speech, and the formation of the uniquely human chin.
Ursus rossicus is an extinct species of bear that lived in the steppe regions of northern Eurasia and Siberia during the Pleistocene.
Medieval Bioarchaeology is the study of human remains recovered from medieval archaeological sites. Bioarchaeology aims to understand populations through the analysis of human skeletal remains and this application of bioarchaeology specifically aims to understand medieval populations. There is an interest in the Medieval Period when it comes to bioarchaeology, because of how differently people lived back then as opposed to now, in regards to not only their everyday life, but during times of war and famine as well. The biology and behavior of those that lived in the Medieval Period can be analyzed by understanding their health and lifestyle choices.
Linear enamel hypoplasia (LEH) is a failure of the tooth enamel to develop correctly during growth, leaving bands of reduced enamel on a tooth surface. It is the most common type of enamel hypoplasia reported in clinical and archaeological samples, with other types including plane-form enamel hypoplasia and pitting enamel hypoplasia.
The diet of known human ancestors varies dramatically over time. Strictly speaking, according to evolutionary anthropologists and archaeologists, there is not a single hominin Paleolithic diet. The Paleolithic covers roughly 2.8 million years, concurrent with the Pleistocene, and includes multiple human ancestors with their own evolutionary and technological adaptations living in a wide variety of environments. This fact with the difficulty of finding conclusive evidence often makes broad generalizations of the earlier human diets very difficult. Our pre-hominin primate ancestors were broadly herbivorous, relying on either foliage or fruits and nuts and the shift in dietary breadth during the Paleolithic is often considered a critical point in hominin evolution. A generalization between Paleolithic diets of the various human ancestors that many anthropologists do make is that they are all to one degree or another omnivorous and are inextricably linked with tool use and new technologies. Nonetheless, according to the California Academy of Sciences, "Prior to about 3.5 million years ago, early humans dined almost exclusively on leaves and fruits from trees, shrubs, and herbs—similar to modern-day gorillas and chimpanzees."
Pliopapio is an extinct genus of Old World monkey known from the latest part of the Miocene to the early Pliocene Epochs from the Afar Region of Ethiopia. It was first described based on a very large series of fossils from the site of Aramis in the Middle Awash, which has been dated by 40Ar/39Ar to 4.4 million years old. It has since been found from similarly aged sediments at Gona, approximately 75 km to the North. Additional fossils from the Middle Awash extend its known time range back to at least 5.3 million years ago. There is only one known species, Pliopapio alemui.
Near Eastern bioarchaeology covers the study of human skeletal remains from archaeological sites in Cyprus, Egypt, Levantine coast, Jordan, Turkey, Iran, Saudi Arabia, Qatar, Kuwait, Bahrain, United Arab Emirates, Oman, and Yemen.