Earliest known human burial in Africa.

The origin and evolution of hominin mortuary practices are topics of intense interest and debate1-3. Human burials dated to the Middle Stone Age (MSA) are exceedingly rare in Africa and unknown in East Africa1-6. Here we describe the partial skeleton of a roughly 2.5- to 3.0-year-old child dating to 78.3 ± 4.1 thousand years ago, which was recovered in the MSA layers of Panga ya Saidi (PYS), a cave site in the tropical upland coast of Kenya7,8. Recent excavations have revealed a pit feature containing a child in a flexed position. Geochemical, granulometric and micromorphological analyses of the burial pit content and encasing archaeological layers indicate that the pit was deliberately excavated. Taphonomical evidence, such as the strict articulation or good anatomical association of the skeletal elements and histological evidence of putrefaction, support the in-place decomposition of the fresh body. The presence of little or no displacement of the unstable joints during decomposition points to an interment in a filled space (grave earth), making the PYS finding the oldest known human burial in Africa. The morphological assessment of the partial skeleton is consistent with its assignment to Homo sapiens, although the preservation of some primitive features in the dentition supports increasing evidence for non-gradual assembly of modern traits during the emergence of our species. The PYS burial sheds light on how MSA populations interacted with the dead.

Similarities and differences in the dental tissue proportions of the deciduous and permanent canines of Early and Middle Pleistocene human populations.

The two- and three-dimensional assessment of dental tissues has become routine in human taxonomic studies throughout the years. Nonetheless, most of our knowledge of the variability of the enamel and dentine dimensions of the human evolutionary lineage comes from the study of permanent dentition, and particularly from molars. This leads to a biased view of the variability of these features. Due to their early formation and rapid development, the deciduous teeth allow more simplified inferences regarding the processes involved in the dental tissue development of each group. Therefore, their study could be very valuable in dental palaeohistology. In this research, we have explored the dental tissue proportions of the deciduous canines belonging to some human samples of the Early and Middle Pleistocene. The purpose of this was to discuss the meaning of the similarities and differences observed in their histological pattern, as well as to evaluate the degree of covariance with that observed in the permanent dentition of these populations. Our results show that, although there are some similarities in the dental tissue proportions between the deciduous and permanent canines of the study samples, the two dental classes do not provide a similar or comparable pictures of the dental tissue pattern present in the dentition of fossil hominins. Future works on the dental tissue patterns of the anterior and posterior dentition, including deciduous teeth, of fossil samples, may help to shed light on this hypothesis.

Early Pleistocene hominin teeth from Gongwangling of Lantian, Central China.

The fossil hominin individual from Gongwangling of Lantian, Central China, represents one of the earliest members attributed to Homo erectus in East Asia. Recent paleomagnetic analyses have yielded an age of 1.63 Ma for the Gongwangling hominin. The fossils from this site are critical to characterize the morphological features of early hominins in East Asia and to understand their relationships with other earlier and later members of the genus Homo. However, most morphological details of the Gongwangling cranium were obliterated due to postmortem erosion and deformation. Here we used high-resolution microcomputed tomography and three-dimensional virtual imaging techniques to extract the teeth and reconstruct the worn/damaged areas, describe the external morphology, measure crown diameters, record nonmetric traits of the crown and root, and investigate the shape of the enamel-dentine junction using geometric morphometrics. We compared the data obtained from the six teeth of the Gongwangling hominin with African early Homo, African and Georgian Homo erectus s.l., Asian Homo erectus, Homo antecessor, pre-Neanderthals, Neanderthals, and modern humans. Our results show that the Gongwangling specimens display affinities with other specimens attributed to H. erectus s.l. The highly divergent and noncoalesced three-root system in the Gongwangling specimens is comparable to that in the Early Pleistocene members of H. erectus s.l., and differs from Middle Pleistocene representatives of the species. The enamel-dentine junction shape of the Gongwangling molars prefigures the Asian H. erectus pattern later found in East Asian Middle Pleistocene H. erectus. The morphological comparisons between East Asian Early Pleistocene (e.g., Gongwangling, Meipu, and Quyuan River Mouth) and Middle Pleistocene H. erectus (e.g., Zhoukoudian, Hexian, and Yiyuan) suggest a potential temporal trend within this species in East Asia.

Comparing the Boxgrove and Atapuerca (Sima de los Huesos) human fossils: Do they represent distinct paleodemes?

The early Middle Pleistocene human material from Boxgrove (West Sussex, UK) consists of a partial left tibia and two lower incisors from a separate adult individual. These remains derive from deposits assigned to the MIS 13 interglacial at about 480 ka and have been referred to as Homo cf. heidelbergensis. The much larger skeletal sample from the Sima de los Huesos (Atapuerca, Spain) is dated to the succeeding MIS 12, at about 430 ka. This fossil material has previously been assigned to Homo heidelbergensis but is now placed within the Neanderthal clade. Because of the scarcity of human remains from the Middle Pleistocene and their morphological variability, this study assessed whether the Boxgrove specimens fit within the morphological variability of the homogeneous Sima de los Huesos population. Based on morphometric analyses performed against 22 lower incisors from Sima de los Huesos and published material, the data from the Boxgrove incisors place them comfortably within the range of Sima de los Huesos. Both assemblages present robust incisors distinct from the overall small recent Homo sapiens incisors, and Boxgrove also aligns closely with Homo neanderthalensis and some other European Middle Pleistocene hominins. Following morphological and cross-sectional analyses of the Boxgrove tibia compared to seven adult Sima de los Huesos specimens and a set of comparative tibiae, Boxgrove is shown to be similar to Sima de los Huesos and Neanderthals in having thick cortices and bone walls, but in contrast resembles modern humans in having a straight anterior tibial crest and a suggestion of a lateral concavity. Based on the patterns observed, there is no justification for assigning the Boxgrove and Sima de los Huesos incisors to distinct paleodemes, but the tibial data show greater contrasts and suggest that all three of these samples are unlikely to represent the same paleodeme.

Testing the inhibitory cascade model in the Middle Pleistocene Sima de los Huesos (Sierra de Atapuerca, Spain) hominin sample.

The Middle Pleistocene Sima de los Huesos (SH) site has yielded more than 7.500 human fossil remains belonging to a minimum of 29 individuals. Most of these individuals preserve either the complete mandibular molar series or at least the first (M1 ) and second (M2 ) molars. The inhibitory cascade mathematical model was proposed by Kavanagh et al. (Nature, 449, 427-433 [2007]) after their experimental studies on the dental development of murine rodent species. The activator-inhibitor mechanism of this model has shown its ability for predicting evolutionary size patterns of mammalian teeth, including hominins. The main aim of this study is to test whether the size molar patterns observed in the SH hominins fit the inhibitory cascade model. With this purpose, we have measured the crown area of all SH molars in photographs, using a planimeter and following techniques used and well contrasted in previous works. Following one of the premises of the inhibitory cascade model, we expect that the central tooth (M2 in our case) of a triplet would have the average size of the two outer teeth. The absolute difference between the observed and the expected values for the M2 s ranges from 0.23 to 8.46 mm2 in the SH sample. In terms of percentage, the difference ranges between 0.25% and 10.34%, although in most cases, it is below 5%. The plot of the estimated M3 /M1 and M2 /M1 size ratios obtained in the SH hominins occupies a small area of the theoretical developmental morphospace obtained for rodent species. In addition, the majority of the values are placed near the theoretical line which defines the relationship predicted by the inhibitory cascade model in these mammals. The values of the slope and intercept of the reduced major regression obtained for the SH individuals do not differ significantly from those obtained for rodent species, thus confirming that the size of the molars of the SH hominins fits the inhibitory cascade model. We discuss these results in terms of dental development. Despite the promising results in the SH sample, we draw the attention to the fact that most Early Pleistocene Homo specimens exhibit a pattern (M1  < M2  > M3 ), which is outside the expected theoretical morphospace predicted by the inhibitory cascade model. The shift from the M1 < M2 < M3 size relationship observed in early hominins (including H. habilis) to the M1 > M2 > M3 size relationship, which is predominant in modern humans, includes sequences that depart from predictions of the inhibitory cascade model. Additional studies are required to understand these deviations.

Testing the inhibitory cascade model in a recent human sample.

The Inhibitory Cascade Model was proposed by Kavanagh and colleagues (Nature, 449, 427-433 [2007]) after their experimental studies on the dental development of murine rodent species. These authors described an activator-inhibitor mechanism that has been employed to predict evolutionary size patterns of mammalian teeth, including hominins. In the present study, we measured the crown area of the three lower permanent molars (M1, M2, and M3) of a large recent modern human sample of male and female individuals from a collection preserved at the Institute of Anthropology of the University of Coimbra (Portugal). The main aim of the present study is to test if the size molar patterns observed in this human sample fits the Inhibitory Cascade Model. For this purpose, we first measured the crown area in those individuals preserving the complete molar series. Measurements were taken in photographs, using a planimeter and following well-tested techniques used in previous works. We then plot the M3 /M1 and M2 /M1  size ratios. Our results show that the premise of the Inhibitory Cascade Model, according to which the average of the crown area of M2 is approximately one-third of the sum of the crown area of the three molars, is fulfilled. However, our results also show that the individual values of a significant number of males and females are out of the 95% confidence interval predicted by the Inhibitory Cascade Model in rodents. As a result, the present analyses suggest that neither the sample of males, nor that of females, nor the pooled sample fits the Inhibitory Cascade Model. It is important to notice that, although this model has been successfully tested in a large number of current human populations, to the best of our knowledge this is the first study in which individual data have been obtained in a recent human population rather than using the average of the sample. Our results evince that, at the individual level, some factors not yet known could interfere with this model masking the modulation of the size on the molar series in modern humans. We suggest that the considerable delay in the onset of M3 formation in modern humans could be related to a weakening of the possible activation/inhibition process for this tooth. Finally, and in support of our conclusions, we have checked that the absolute and relative size of M1 and M2 is not related to the M3 agenesis in our sample. In line with other studies in primates, our results do not support the Inhibitory Cascade Model in a recent human sample. Further research is needed to better understand the genetic basis of this mechanism and its relationship to the phenotype. In this way, we may be able to find out which evolutionary changes may be responsible for the deviations observed in many species, including Homo sapiens.

Comparative dental study between Homo antecessor and Chinese Homo erectus: Nonmetric features and geometric morphometrics.

The Chinese Middle Pleistocene fossils from Hexian, Xichuan, Yiyuan, and Zhoukoudian have been generally classified as Homo erectus s.s. These hominins share some primitive features with other Homo specimens, but they also display unique cranial and dental traits. Thus, the Chinese Middle Pleistocene hominins share with other European and Asian hominin populations the so-called 'Eurasian dental pattern'. The late Early Pleistocene hominins from Gran Dolina-TD6.2 (Spain), representing the species Homo antecessor, also exhibit the Eurasian dental pattern, which may suggest common roots. To assess phylogenetic affinities of these two taxa, we evaluated and compared nonmetric and metric dental features and interpreted morphological differences within a comparative hominin framework. We determined that the robust roots of the molars, the shelf-like protostylid, the dendrite-like pattern of the enamel-dentine junction surface of the upper fourth premolars and molars, the strongly folded dentine of the labial surface of the upper incisors, and the rare occurrence of a mid-trigonid crest in the lower molars, are all characteristic of Chinese H. erectus. With regard to H. antecessor, we observed the consistent expression of a continuous mid-trigonid crest, the absence of a cingulum in the upper canines, a complex root pattern of the lower premolars, and a rhomboidal occlusal contour and occlusal polygon and protrusion in the external outline of a large a bulging hypocone in the first and second upper molars. Using two-dimensional geometric morphometrics, we further demonstrated that H. antecessor falls outside the range of variation of Chinese H. erectus for occlusal crown outline shape, the orientation of occlusal grooves, and relative locations of anterior and posterior foveae in the P4s, P3s, M1s, M2s, and M2s. Given their geographic and temporal separation, the differences between these two species suggest their divergence occurred at some point in the Early Pleistocene, and thereafter they followed different evolutionary paths.

The Ratón Pérez collection: Modern deciduous human teeth at the Centro Nacional de Investigación sobre la Evolución Humana (Burgos, Spain).

OBJECTIVES: The aim of this report is to present the large deciduous tooth collection of identified children that is housed at the National Research Center on Human Evolution (CENIEH) in Burgos, Spain. METHODS: Yearly, members of the Dental Anthropology Group of the CENIEH are in charge of collecting the teeth and registering all the relevant information from the donors at the time of collection. In compliance with Spanish Law 14/2007 of July 3, 2007, on Biomedical Research (BOE-A-2007-12945), all individuals are guaranteed anonymity and confidentiality. When the donor hands in the tooth, they fill out a Donor Information Form and sign the Informed Consent Form. At the same time, another person completes the data label for the transparent polyethylene zip lock bag where the tooth is temporarily stored. All teeth are then transferred to the CENIEH Restoration lab, where the specialists apply the same protocol as for the fossil remains. RESULTS: Although the sample is still growing, from the first collection campaign in 2014 to date it comprises 2977 teeth of children whose ages of tooth loss are between 2 and 15 years. Each tooth is associated with basic information of the individuals and their parents and grandparents (sex, date, and place of birth, ancestry, country of residence), as well as important data about early life history (pregnancy duration, breastfeeding, bottle-feeding) and other relevant information provided by the donors (such as if they are twins, dental loss, or dental extraction). CONCLUSIONS: Due to the scarcity of deciduous dental samples available, the Ratón Pérez collection represents a highly valuable sample for a wide range of disciplines such as forensic, dental, and anthropological fields among others.

Inner morphological and metric characterization of the molar remains from the Montmaurin-La Niche mandible: The Neanderthal signal.

Here, we present a metric and morphological study of the molar remains from the Montmaurin-La Niche mandible by means of microcomputed tomography. According to the last analysis, based on the combination of geomorphological and paleontological data, the level bearing this human mandible probably corresponds to the marine isotope stages (MIS) 7. These data place the Montmaurin-La Niche in a chronologically intermediate position between the Neanderthals and the Middle Pleistocene fossils (e.g., Sima de los Huesos, la Caune de l'Arago). A recent study has revealed that while the mandible is more closely related to the Early and Middle Pleistocene African and Eurasian populations, the morphology of the outer enamel surfaces of its molars is typical of the Neanderthal linage. The data presented here are in line with this finding because the morphology of the enamel-dentine junction of the molars is similar to that of Neanderthals, whereas the absolute and relative enamel thickness values (2D and 3D) are closer to those exhibited by some Early Pleistocene hominins. Moreover, the pulp cavity morphology and proportions are in concordance with the Neanderthal populations. Our results strengthen the hypothesis that the settlement of Europe could be the result of several migrations, at different times, originated from a common source population. Thus, the variability in the European Middle Pleistocene populations (e.g., Montmaurin, Sima de los Huesos, Arago, Mala Balanica) could indicate different migrations at different times and/or population fragmentation, without excluding the possible hybridization between residents and new settlers.

Sexual dimorphism of the enamel and dentine dimensions of the permanent canines of the Middle Pleistocene hominins from Sima de los Huesos (Burgos, Spain).

Sexual dimorphism is an important component of the total variation seen in populations and plays a key role in taxonomic debates. In this study, microtomographic (microcomputed tomography) techniques were applied to a sample of hominin teeth from the Sima de los Huesos site (Spain). Dental tissue proportions of the permanent canines were assessed to characterize the pattern and degree of sexual dimorphism within this population. In addition, the possible similarities and differences with the Homo neanderthalensis remains from Krapina (Croatia) and with a recent modern human sample were evaluated. A combination of classical statistical approaches with more novel techniques allowed us not only to ratify the sex allocation of the individuals previously assigned in the literature but also to estimate the sex of the youngest individuals, which were not assessed in previous studies. Likewise, the sexes of certain extensively worn canines and isolated pieces were estimated. As a result, the sex ratio observed in our dental sample from the Sima de los Huesos population is 5:9 (Nm:Nf). In general terms, both Sima de los Huesos and Krapina dental samples have a degree of sexual dimorphism in their permanent canine tissue proportions that does not surpass that of modern humans. The marked dimorphic root volume of Sima de los Huesos mandibular canines is the exception, which surpasses the modern human mean, although it falls within the 95% confidence interval. Therefore, our results do not support that dental tissue proportions of the European Middle Pleistocene populations were more dimorphic than in modern humans. However, the differences in canine tissue proportions are great enough to allow sex estimation with a high degree of confidence.

A descriptive and comparative study of two Early Pleistocene immature scapulae from the TD6.2 level of the Gran Dolina cave site (Sierra de Atapuerca, Spain).

Here we present the descriptive and comparative study of two immature scapulae recovered from the TD6.2 level of the Gran Dolina cave site (Sierra de Atapuerca, Spain) and assigned to Homo antecessor. This is the first time that data on the morphology and dimensions of the scapulae of a European late Early Pleistocene hominin population are provided. Considering the state of development and the linear dimensions, the scapula ATD6-116 could belong to a child of about 2-4 years. The morphology of ATD6-116 clearly departs from that of the Australopithecus afarensis juvenile specimen DIK-1-1, pointing to functional differences in locomotor behavior between Australopithecus and the late Early Pleistocene hominins. The immature scapula ATD6-118 belonged to an immature individual with a development of the scapula equivalent to that of adolescents of recent human populations. The scapulae ATD6-118 and KNM-WT 15000 present a similar state of development. Although the scapula KNM-WT 15000 is clearly larger than ATD6-118, these two specimens share some characteristics such as their relative narrowness and the value of the axilloglenoid and spinoglenoid angles. The glenoid fossa of ATD6-116 show a lateral orientation, whereas in ATD6-118 the glenoid fossa is slightly cranially oriented, but still within the range of variation of modern humans. The glenoid index of both ATD6-116 and ATD6-118 is low in accordance to the values usually observed in other early hominins, thus showing the primitive condition for this feature. Both scapulae show a ventrally placed axillary sulcus. The presence of this primitive feature in ATD-116 confirms that the shape of the axillary border has a genetic basis and it is not related to physical activity.

Ectopic maxillary third molar in Early Pleistocene Homo antecessor from Atapuerca-Gran Dolina site (Burgos, Spain).

OBJECTIVES: Here we describe the case of an ectopic maxillary third molar (M3 ), preventing the eruption of the M2 , in the individual H3 of the hominin hypodigm of level TD6.2 of the Early Pleistocene site of Gran Dolina (Sierra de Atapuerca, Spain). MATERIALS AND METHODS: The fossil remains from the TD6.2 level of the Gran Dolina site (about 170 specimens) are assigned to Homo antecessor. Different geochronological methods place these hominins in the oxygen isotopic stage 21, between 0.8 and 0.85 million years ago (Ma). The immature individual H3 is represented by an almost complete midface (ATD6-69), preserving various teeth in situ. We used high-resolution microtomograhy (mCT) to investigate the abnormal position of the left M3 , virtually reconstruct M2 , and M3 as well as assessing the development stage of these. Finally, we compare this case with extinct and extant populations. RESULTS: Based on the identified signs, we suggest that individual H3 suffered from a unilateral impaction of the M2 as a result of the ectopic position of the developing M3 . DISCUSSION: We conclude that the most likely etiology for the ectopic position of the M3 is the lack of space in the maxilla. We discuss possible contributing factors, such as morphometric aspects of the maxilla and the early mineralization of the M3 , to support the M2 impaction. Finally, due to the early age at death of this individual we did not identify any secondary lesion associated with the M2 impaction.

New permanent teeth from Gran Dolina-TD6 (Sierra de Atapuerca). The bearing of Homo antecessor on the evolutionary scenario of Early and Middle Pleistocene Europe.

Here we analyze the unpublished hominin dental remains recovered from the late Early Pleistocene Gran Dolina-TD6.2 level of the Sierra de Atapuerca (northern Spain), as well as provide a reassessment of the whole TD6.2 hominin dental sample. Comparative descriptions of the outer enamel surface (OES) and the enamel-dentine junction (EDJ) are provided. Overall, the data presented here support the taxonomic validity of Homo antecessor, since this species presents a unique mosaic of traits. Homo antecessor displays several primitive features for the genus Homo as well as some traits exclusively shared with Early and Middle Pleistocene Eurasian hominins. Some of these Eurasian traits were retained by the Middle Pleistocene hominins of Europe, and subsequently became the typical condition of the Neanderthal lineage. Although other skeletal parts present resemblances with Homo sapiens, TD6.2 teeth do not show any synapomorphy with modern humans. In addition, TD6.2 teeth can be well differentiated from those of Asian Homo erectus. The dental evidence is compatible with previous hypothesis about H. antecessor belonging to the basal population from which H. sapiens, Homo neanderthalensis, and Denisovans emerged. Future findings and additional research may help to elucidate the precise phylogenetic link among them.

Sexual dimorphism of dental tissues in modern human mandibular molars.

OBJECTIVES: Previous studies have revealed that human permanent dental tissue proportions differ significantly between males and females, with females having relatively thicker enamel relative to overall crown area than males. The aims of this study are to investigate sexual dimorphism in permanent mandibular molars and to determine whether such differences can be used to estimate sex in modern humans reliably. MATERIALS AND METHODS: The permanent mandibular molars used in this study (n = 51) originate from 36 individuals of known sex from a Spanish anthropological collection. Eight variables were assessed from two-dimensional (2D) mesial planes of section obtained from microtomographic scans. Binary stepwise logistic regression was then applied to the data. RESULTS: Male molars possess significantly greater quantities of dentine than females, both absolutely and proportionally. Females differed significantly from males by having greater relative enamel thickness. Logistic regression identified the proportion of dentine (relative dentine area [RDA]) as the most important sex discriminator, which can be used to correctly classify specimens with an overall accuracy rate of 74.36%. DISCUSSION: These results confirm that sexual dimorphism in mandibular molar size is a result of males having a greater amount of dentine, both absolutely and proportionally. The findings suggest that 2D measurements of RDA may be useful for sex determination, although further research is required to test the reliability of these predictive techniques across different populations.

Modern humans sex estimation through dental tissue patterns of maxillary canines.

OBJECTIVES: Dental tissue proportions of human permanent canines is one of only a few sexually dimorphic features that is present in childhood and maintained in adults, offering the opportunity for this to be used in sex determination. This study assesses dental tissue volumes and surface areas of maxillary permanent canines in a sample of known sex to provide new data and to explore the potential of these variables as reliable sexual estimators. MATERIALS AND METHODS: The teeth studied here derive from 56 individuals (27 females and 29 males) of known sex and age, and of different geographic origins. The teeth were scanned and three-dimensional (3D) measurements (volumes and surface areas) were obtained. In addition, a discriminant function analysis was applied. RESULTS: The results presented here concur with those previously published in relation to both size and dental tissue patterns. Male maxillary canines have a greater dentine component, whereas female enamel is thicker, leading to a difference in dental size in favor of males. Discriminant functions were calculated using these histological variables successfully identifying sex in between 87.5% and 93.75% of the known-sex hold-out sample, with 92.3% correctly assigned when all functions were applied together. DISCUSSION: The present study supports that methods for sex determination based on dental tissue measurements can achieve high allocation accuracies, being especially useful in the case of subadults or when no other appropriate method is available.

Dentine morphology of Atapuerca-Sima de los Huesos lower molars: Evolutionary implications through three-dimensional geometric morphometric analysis.

OBJECTIVES: This study aims to explore the affinities of the Sima de los Huesos (SH) population in relation to Homo neanderthalensis, Arago, and early and contemporary Homo sapiens. By characterizing SH intra-population variation, we test current models to explain the Neanderthal origins. MATERIALS AND METHODS: Three-dimensional reconstructions of dentine surfaces of lower first and second molars were produced by micro-computed tomography. Landmarks and sliding semilandmarks were subjected to generalized Procrustes analysis and principal components analysis. RESULTS: SH is often similar in shape to Neanderthals, and both groups are generally discernible from Homo sapiens. For example, the crown height of SH and Neanderthals is lower than for modern humans. Differences in the presence of a mid-trigonid crest are also observed, with contemporary Homo sapiens usually lacking this feature. Although SH and Neanderthals show strong affinities, they can be discriminated based on certain traits. SH individuals are characterized by a lower intra-population variability, and show a derived dental reduction in lower second molars compared to Neanderthals. SH also differs in morphological features from specimens that are often classified as Homo heidelbergensis, such as a lower crown height and less pronounced mid-trigonid crest in the Arago fossils. DISCUSSION: Our results are compatible with the idea that multiple evolutionary lineages or populations coexisted in Europe during the Middle Pleistocene, with the SH paradigm phylogenetically closer to Homo neanderthalensis. Further research could support the possibility of SH as a separate taxon. Alternatively, SH could be a subspecies of Neanderthals, with the variability of this clade being remarkably higher than previously thought.

Contribution of dental tissues to sex determination in modern human populations.

OBJECTIVES: Accurate sex estimation is an essential step for the reconstruction of the biological profile of human remains. Earlier studies have shown that elements of the human permanent dentition are sexually dimorphic. The aims of this study are to determine the degree of sexual dimorphism in the dental tissue volumes and surface areas of mandibular canines and to explore its potential for reliable sex determination. METHOD: The teeth included in this study (n = 69) were selected from anthropological collections from Spain, South Africa and Sudan. In all cases, the sex of the individuals was known. The teeth were scanned and three-dimensional (3D) measurements (volumes and surfaces areas) were obtained. Finally, a dsicriminant function analysis was applied. RESULTS: Our results showed that sexual dimorphism in canine size is due to males having greater amounts of dentine, whereas enamel volume does not contribute significantly to overall tooth size dimorphism. Classification accuracy of the multivariable equations tested on slightly worn teeth ranged from 78 to 90.2% for the crossvalidation, and from 71.43 to 84.62% for the hold-out sample validation. When all functions were applied together, the sex was correctly assigned 92.30% of the time. CONCLUSIONS: Our results suggest that the 3D variables from mandibular canine dental tissues are useful for sex determination as they present a high degree of dimorphism. The results obtained show the importance of 3D dental tissue measurements as a methodology in sex determination, which application should be considered as a supplemental method to others.

Quantifying the impact of µCT-scanning of human fossil teeth on ESR age results.

Fossil human teeth are nowadays systematically CT-scanned by palaeoanthropologists prior to any further analysis. It has been recently demonstrated that this noninvasive technique has, in most cases, virtually no influence on ancient DNA preservation. However, it may have nevertheless an impact on other techniques, like Electron Spin Resonance (ESR) dating, by artificially ageing the apparent age of the sample. To evaluate this impact, we µCT-scanned several modern enamel fragments following the standard analytical procedures employed by the Dental Anthropology Group at CENIEH, Spain, and then performed ESR dose reconstruction for each of them. The results of our experiment demonstrate that the systematic high-resolution µCT-scanning of fossil hominin remains introduces a nonnegligible X-ray dose into the tooth enamel, equivalent to 15-30 Gy depending on the parameters used. This dose may be multiplied by a factor of ∼8 if no metallic filter is used. However, this dose estimate cannot be universally extrapolated to any µCT-scan experiment but has instead to be specifically assessed for each device and set of parameters employed. The impact on the ESR age results is directly dependent on the magnitude of the geological dose measured in fossil enamel but could potentially lead to an age overestimation up to 40% in case of Late Pleistocene samples, if not taken into consideration.

Early Pleistocene hominin deciduous teeth from the Homo antecessor Gran Dolina-TD6 bearing level (Sierra de Atapuerca, Spain).

OBJECTIVES: During the last 13 years, the late Early Pleistocene Gran Dolina-TD6-2 level (Sierra de Atapuerca, northern Spain) has yielded an additional sample of 26 dental specimens attributed to Homo antecessor. In this report, we present a descriptive and comparative study of the six deciduous teeth. METHODS: We provide external and internal morphological descriptions following classical terminology, as well as the mesiodistal and buccolingual measurements of the teeth. The internal morphology was described by means of micro-CT technique. RESULTS: The TD6 deciduous teeth preserve primitive features regarding the Homo clade, such as the presence of styles in lower and upper canines and developed anterior and posterior foveae in the dm2 . However, other features related to the complexity of the crown morphology (e.g., cingulum) are not present in this sample. Furthermore, the great reduction of the talonid of the dm1 s is also noteworthy. Despite the limited comparative evidence, the presence of a remarkably well-developed tuberculum molare in the dm1 and dm1 s from TD6 can be also considered a derived feature in the genus Homo. The TD6 hominins exhibit dental dimensions similar to those of other Pleistocene hominins. The dm1 s are buccolingually elongated and the buccolingual diameter of ATD6-93 is the largest recorded so far in the Homo fossil record. CONCLUSIONS: This study expands the list of plesiomorphic features of H. antecessor, and provides some information on the evolutionary status of this species. However, the identification of some advanced traits evinces a step towards the derived morphology of European Pleistocene teeth. The study of the deciduous dentition confirms the mosaic pattern of H. antecessor morphology revealed in previous studies of this hominin sample.

New methodology to reconstruct in 2-D the cuspal enamel of modern human lower molars.

OBJECTIVES: In the last years different methodologies have been developed to reconstruct worn teeth. In this article, we propose a new 2-D methodology to reconstruct the worn enamel of lower molars. Our main goals are to reconstruct molars with a high level of accuracy when measuring relevant histological variables and to validate the methodology calculating the errors associated with the measurements. METHODS: This methodology is based on polynomial regression equations, and has been validated using two different dental variables: cuspal enamel thickness and crown height of the protoconid. In order to perform the validation process, simulated worn modern human molars were employed. The associated errors of the measurements were also estimated applying methodologies previously proposed by other authors. RESULTS: The mean percentage error estimated in reconstructed molars for these two variables in comparison with their own real values is -2.17% for the cuspal enamel thickness of the protoconid and -3.18% for the crown height of the protoconid. This error significantly improves the results of other methodologies, both in the interobserver error and in the accuracy of the measurements. CONCLUSIONS: The new methodology based on polynomial regressions can be confidently applied to the reconstruction of cuspal enamel of lower molars, as it improves the accuracy of the measurements and reduces the interobserver error. The present study shows that it is important to validate all methodologies in order to know the associated errors. This new methodology can be easily exportable to other modern human populations, the human fossil record and forensic sciences.