Tooth wear and dentoalveolar remodeling are key factors of morphological variation in the Dmanisi mandibles

The "Smile Design and Space" Concept for Altering Vertical Dimension of Occlusion and Esthetic Restorative Material Selection

OBJECTIVE

This article introduces the smile design and space (SDS) concept for managing the vertical dimension of occlusion (VDO) in full-mouth reconstructions and its influence on the selection of esthetic restorative materials. Limitations of traditional VDO adjustment methods are being addressed through a facially driven treatment approach that enhances esthetics improves function and minimizes invasiveness.

CLINICAL CONSIDERATIONS

The SDS concept involves detailed evaluations of the incisal edges of the maxillary central incisors in relation to the upper lip at rest and at full smile. This includes analyzing variations in incisal exposure due to differing lip mobility, which can significantly impact gingival esthetics, particularly in cases with gingival exposure during smiling. The concept employs a strategic formula to determine the necessary alterations in VDO based on specific dental relationships and wear patterns.

CONCLUSIONS

The SDS concept provides guidelines for full-mouth reconstructions, emphasizing minimal invasiveness and the integration of esthetics with functional dynamics to enhance the predictability of clinical outcomes and reduce complications associated with traditional restoration techniques.

CLINICAL SIGNIFICANCE

The SDS concept enhances the precision of full-mouth reconstructions through individualized adjustment of the VDO, tailored to the esthetic and functional requirements of each patient.

Myths surrounding vertical dimension of occlusion in restorative dentistry: A scoping review

OBJECTIVE

This scoping review aims to clarify the concept of vertical dimension of occlusion (VDO) in prosthetic dentistry, addressing prevalent myths, and controversies regarding its clinical management and impact on the stomatognathic system.

METHODS

This paper critically examines common beliefs about VDO alteration and its effects on temporomandibular disorders (TMD) through an extensive literature review and an international survey. The survey included 862 general dentists and prosthodontists and explored their approaches to altering VDO and their perceptions of the clinical implications. The literature review provided a thorough analysis of existing research on VDO modification techniques, the adaptability of the stomatognathic system, and the relationship between VDO changes and TMD.

RESULTS

The survey revealed insights into dentists' perspectives on VDO, showing that while many practitioners test a new VDO due to concerns about patient adaptation, a significant majority observed that patients typically adjust well to a new VDO regardless of the technique used. The survey highlighted differing beliefs about the need for a gradual process and trial phase for VDO alteration, as well as the stability of modified VDO. Literature review suggests the stability and adaptability of VDO changes due to muscle adaptability and indicates no direct causal or curative link between VDO changes and TMD. Traditional methods for determining VDO in complete dentures may not be suitable for worn dentition, underscoring the need for tailored approaches.

CONCLUSION

This paper suggests that the traditional belief in the need for a prolonged trial phase for VDO alterations may be reconsidered in light of evidence supporting the adaptability of the stomatognathic system. Moreover, it emphasizes the importance of distinguishing between methods suitable for complete dentures and those for managing cases of worn dentition. The purported link between VDO alterations and TMD is also found to lack scientific evidence, highlighting the need for individualized patient care based on current evidence and clinical judgment.

Periodontitis and alveolar resorption in human skeletal remains: The relationship between quantitative alveolar bone loss, occlusal wear, antemortem tooth loss, dental calculus and age at death in a low socioeconomic status, modern forensic human collection from Yucatan

OBJECTIVE

This paper assesses the relationship between the distance between the cemento-enamel junction and alveolar crest and risk factors commonly associated with periodontitis.

MATERIALS

Eighty individuals between 28 and 92 years old with known biological sex and age were analyzed from a 20th century forensic human collection from Merida, Yucatan (Mexico).

METHODS

Macroscopic assessment, along with metric analysis, was employed using a probe.

RESULTS

Ante-mortem tooth loss was positively correlated with the distance between the cemento-enamel junction and alveolar crest, as was the presence of root calculus in females.

CONCLUSIONS

Cemento-enamel junction to alveolar crest distance is not a reliable indicator of periodontitis since it is not directly related to periodontitis-causing infectious pathogens, and since ante-mortem tooth loss can affect root exposure.

SIGNIFICANCE

This study demonstrates that a purely quantitative approach to diagnosing periodontitis in archaeological and forensic human remains can be misleading.

LIMITATIONS

The skeletal collection is only representative of the low socioeconomic class of Merida, and its female cohort is underrepresented. In addition, because the Xoclan collection is modern, limitations (particularly with respect to tooth wear) of the applicability of these interpretations to older archaeological remains exist.

SUGGESTION FOR FURTHER RESEARCH

A combination of quantitative and qualitative characteristics of alveolar bone is needed to reliably diagnose periodontitis in skeletal populations.

Life and death at Dmanisi, Georgia: Taphonomic signals from the fossil mammals

There are many hypotheses regarding influences on the early hominin biogeographic spread into Eurasia; among them is increased meat-eating. Dmanisi in Georgia is one of the rare Early Pleistocene sites in Eurasia, and here we present primary information and analysis of the medium and large mammal taphonomy, contributing information about site formation and the hominins' interaction with the fauna. Nearly 85% of the specimens come from the B1 stratum. Relative abundances of mammal families demonstrate some bias toward carnivores, especially Canis borjgali, and diverse Felidae species. Bones display little weathering. Post-depositional surface modifications and matrix obscure many bone surfaces, but carnivore tooth marking is the most common bone surface modification from the nutritive taphonomic phase. Tooth pits are large, in the size range of those made by modern Crocuta crocuta and Panthera leo. Breakage variables indicate most breaks occurred while the bones were still fresh, many by carnivore consumption. Fairly even limb bone representation of herbivores suggests carcasses were introduced to the site nearly whole. Hominin tool marks are present in low frequencies, but they suggest a variety of behaviors. These marks are found on Equus, Palaeotragus, Bison, large cervids, Pseudodama, Canis, and Mammuthus. Some were made by filleting proximal limb segments, and so are likely indicative of early access to carcasses, while other marks suggest scavenging. The Homo taphonomic variables resemble the rest of the taphonomic signatures from the site with little weathering, a slightly higher percentage of their bones are whole, but only a few have probable carnivore damage. The assemblage characteristics are compared to modern actualistic and experimental assemblages, and it is concluded that Dmanisi presents a palimpsest of hyena denning, felid activity, hominin meat-eating and likely natural deaths.

Evidence of dental agenesis in late pleistocene Homo

OBJECTIVE

Differential diagnosis and tabulation of cases of dental agenesis in Middle and Upper Paleolithic Western Eurasian humans to synthesize this data and to test previous hypotheses about when recent human patterns of third molar agenesis were established.

MATERIALS

139 Late Pleistocene human remains and 149 individuals from three Epi-Paleolithic/ Holocene non-agricultural comparative collections.

METHODS

All remains were visually and radiographically recorded by the author.

RESULTS

In addition to establishing that third molar agenesis was common during the Late Upper Paleolithic (22,500-10,000 years BP), this study suggests a pattern of increasing prevalence through time.

CONCLUSIONS

An increase in the prevalence of third molar agenesis in the Late Upper Paleolithic could indicate selection for dental size reduction and orthognathy, but also bio-cultural changes from more intensive food preparation techniques.

SIGNIFICANCE

Third molar agenesis, a well-known developmental defect, is often reported for recent human skeletal collections, but the prevalence of the condition for Pleistocene hominins had not been previously quantified in order to consider patterns through time. Hypotheses posited for the high prevalence of third molar agenesis, or hypodontia in general, in some recent human groups require an understanding of the prevalence of these traits in the past.

LIMITATIONS

Paleolithic skeletal remains are incomplete, so these values are under-estimations. Individuals are also separated diachronically and geographically and should not be assumed to represent a single population sample.

SUGGESTIONS FOR FURTHER RESEARCH

Hypotheses on some of the potential selective forces acting on dental size reduction and subsequent agenesis could be tested in recent humans.

What kind of hominin first left Africa?

Recent discoveries of stone tools from Jordan (2.5 Ma) and China (2.1 Ma) document hominin presence in Asia at the beginning of the Pleistocene, well before the conventional Dmanisi datum at 1.8 Ma. Although no fossil hominins documenting this earliest Out of Africa phase have been found, on chronological grounds a pre-Homo erectus hominin must be considered the most likely maker of those artifacts. If so, this sheds new light on at least two disputed subjects in paleoanthropology, namely the remarkable variation among the five Dmanisi skulls, and the ancestry of Homo floresiensis.

Broad-scale morpho-functional traits of the mandible suggest no hard food adaptation in the hominin lineage

An on-going debate concerning the dietary adaptations of archaic hominins and early Homo has been fuelled by contradictory inferences obtained using different methodologies. This work presents an extensive comparative sample of 30 extant primate species that was assembled to perform a morpho-functional comparison of these taxa with 12 models corresponding to eight fossil hominin species. Finite Element Analysis and Geometric Morphometrics were employed to analyse chewing biomechanics and mandible morphology to, firstly, establish the variation of this clade, secondly, relate stress and shape variables, and finally, to classify fossil individuals into broad ingesta related hardness categories using a support vector machine algorithm. Our results suggest that some hominins previously assigned as hard food consumers (e.g. the members of the Paranthropus clade) in fact seem to rely more strongly on soft foods, which is consistent with most recent studies using either microwear or stable isotope analyses. By analysing morphometric and stress results in the context of the comparative framework, we conclude that in the hominin clade there were probably no hard-food specialists. Nonetheless, the biomechanical ability to comminute harder items, if required as fallback option, adds to their strategy of increased flexibility.

The effect of tooth wear, age and sex on facial height assessed by soft tissue analysis

AIM

The aim of the study was to evaluate the effects of tooth wear, age and sex on facial height measurements based on soft tissue analysis.

METHODS

One hundred and twelve subjects (45 males and 67 females), 19-80 years of age (mean 43 ± 0.9 years), which were divided into three age groups, met the inclusion criteria. Tooth wear was assessed using a 5-point ordinal scale (0-4). Based on the tooth wear score, three groups were defined: mild, moderate and severe wear. Facial height was evaluated based on soft tissue measurements using frontal facial photographs. The dimension of the upper facial height (UFH) and lower facial height (LFH) and the ratio between the two (R-U-L) were measured.

RESULTS

Facial height dimensions (UFH, LFH) were significantly different between the three age groups and between the three tooth wear groups. Both the UFH and LFH measurements had a weak positive correlation with age (r = .40; r = .41, respectively) and with tooth wear (r = .40; r = .41, respectively). The R-U-L showed a significant difference (P < .001) between sexes as males showed slightly lower ratio compared with females; however, the R-U-L was not dependent upon age or tooth wear.

CONCLUSIONS

This study demonstrated that although facial height is affected by age and tooth wear, the proportion between the upper to lower facial segments is constant and is not affected by the same parameters. A statistically significant difference in the R-U-L relative to sexes was noted.

Human sound systems are shaped by post-Neolithic changes in bite configuration

Linguistic diversity, now and in the past, is widely regarded to be independent of biological changes that took place after the emergence of Homo sapiens We show converging evidence from paleoanthropology, speech biomechanics, ethnography, and historical linguistics that labiodental sounds (such as "f" and "v") were innovated after the Neolithic. Changes in diet attributable to food-processing technologies modified the human bite from an edge-to-edge configuration to one that preserves adolescent overbite and overjet into adulthood. This change favored the emergence and maintenance of labiodentals. Our findings suggest that language is shaped not only by the contingencies of its history, but also by culturally induced changes in human biology.

Enamel pearls: Their occurrence in recent human populations and earliest manifestation in the modern human lineage

OBJECTIVE

To document and describe the occurrence of an enamel pearl on the distal root surface of the maxillary M3 of the fossil hominin specimen from Florisbad, South Africa that is dated to ca. 259,000 years B.P., and is an early representative of Homo sapiens or as a member of the evolutionary line that was directly ancestral to modern humans.

DESIGN

The molar was examined macroscopically and by micro-computed tomography (μCT) to enable accurate measurement and visualization of the structure of the enamel pearl.

RESULTS

The single pearl has a diameter of 0.97 mm; it is a Type 2 "composite" pearl comprising an enamel cap and dentine core without pulp chamber involvement. The size of the Florisbad pearl falls within or just below the size ranges of this anomaly in modern human samples. Type 2 pearls are most commonly encountered in recent human populations, and the location of the pearl on the distal root surface of the Florisbad M³ is consistent with its most frequent location in recent humans. Pearls in recent human populations affect between 0.2-4.8% of individuals, and 1.7-6.8% of permanent molars. Pearls have been documented in several prehistoric human dentitions, and all examples are less than 4000 years old.

CONCLUSIONS

Enamel pearls have been associated with periodontal disease, but it is not possible to relate its presence to the advanced periodontal inflammation and alveolar bone loss in the Florisbad fossil. Florisbad presents the earliest evidence of this anomaly in the fossil record pertaining to modern humans.

Mandibular molar root and pulp cavity morphology in Homo naledi and other Plio-Pleistocene hominins

The craniomandibular morphology of Homo naledi shows variable resemblances with species across Homo, which confounds an easy assessment of its phylogenetic position. In terms of skull shape, H. naledi has its closest affinities with Homo erectus, while mandibular shape places it closer to early Homo. From a tooth crown perspective, the smaller molars of H. naledi make it distinct from early Homo and H. erectus. Here, we compare the mandibular molar root morphology of six H. naledi individuals from the Dinaledi Chamber to those of African and Eurasian Plio-Pleistocene fossil hominins (totalling 183 mandibular first, second and third molars). The analysis of five root metric variables (cervical plane area, root length, root cervix volume, root branch volume, and root surface area) derived from microCT reconstructions reveals that the molar roots of H. naledi are smaller than those of Homo habilis, Homo rudolfensis, and H. erectus, but that they resemble those of three Homo sp. specimens from Swartkrans and Koobi Fora in size and overall appearance. Moreover, though H. naledi molar roots are similar in absolute size to Pleistocene Homo sapiens, they differ from H. sapiens in having a larger root volume for a given cervical plane area and less taurodont roots; the root cervix-to-branch proportions of H. naledi are comparable to those of Australopithecus africanus and species of Paranthropus. H. naledi also shares a metameric root volume pattern (M₂ > M₃ > M₁) with Australopithecus and Paranthropus but not with any of the other Homo species (M₂ > M₁ > M₃). Our findings therefore concur with previous studies that found that H. naledi shares plesiomorphic features with early Homo, Australopithecus, and Paranthropus. While absolute molar root size aligns H. naledi with Homo from North and South Africa, it is distinguishable from these in terms of root volumetric proportions.

Variation among the Dmanisi hominins: Multiple taxa or one species?

OBJECTIVES

There is continuing controversy over the number of taxa documented by the Dmanisi hominins. Variation may reflect age and sex differences within a single population. Alternatively, two (or more) distinct species may be present. Our null hypothesis states that just one population is represented at the site.

MATERIALS AND METHODS

We assess the likely sources of variation in endocranial capacity, craniofacial and mandibular morphology, and the expression of characters related to aging and sex dimorphism. We use the coefficient of variation and a modified version of Levene's test for equal variances to compare trait variation at Dmanisi with that in fossil hominins and modern Homo sapiens from Africa.

RESULTS

Skull 5 presents a low, massive vault, and a muzzle-like lower face. Other individuals have larger brains and more globular vaults. Despite such variation, the five crania share numerous features. All of the mandibles possess marginal tubercles, mandibular tori, and a distinctive patterning of mental foramina. Relative variation at Dmanisi is comparable to that in selected reference groups. Further growth anticipated in Skull 3, age-related remodeling affecting the D2600 mandible, pathology, and sex dimorphism can account for much of the interindividual variation observed. The preponderance of evidence supports our null hypothesis.

DISCUSSION

Sources of the variation within ancient Homo assemblages remain poorly understood. Skull 5 is a very robust male, with a brain smaller than that of both a juvenile (Skull 3) and a probable female (Skull 2). Skull 1 has the largest brain, but cranial superstructures do not clearly mark this individual as male or female. It is likely that the Dmanisi hominins represent a single paleospecies of Homo displaying a pattern of sex dimorphism not seen in living hominids.

Morphological trends in arcade shape and size in Middle Pleistocene Homo

OBJECTIVES

Middle Pleistocene fossil hominins, often summarized as Homo heidelbergensis sensu lato, are difficult to interpret due to a fragmentary fossil record and ambiguous combinations of primitive and derived characters. Here, we focus on one aspect of facial shape and analyze shape variation of the dental arcades of these fossils together with other Homo individuals.

MATERIALS AND METHODS

Three-dimensional landmark data were collected on computed tomographic scans and surface scans of Middle Pleistocene fossil hominins (n = 8), Homo erectus s.l. (n = 4), Homo antecessor (n = 1), Homo neanderthalensis (n = 13), recent (n = 52) and fossil (n = 19) Homo sapiens. To increase sample size, we used multiple multivariate regression to reconstruct complementary arches for isolated mandibles, and explored size and shape differences among maxillary arcades.

RESULTS

The shape of the dental arcade in H. erectus s.l. and H. antecessor differs markedly from both Neanderthals and H. sapiens. The latter two show subtle but consistent differences in arcade length and width. Shape variation among Middle Pleistocene fossil hominins does not exceed the amount of variation of other species, but includes individuals with more primitive and more derived morphology, all more similar to Neanderthals and H. sapiens than to H. erectus s.l.

DISCUSSION

Although our results cannot reject the hypothesis that the Middle Pleistocene fossil hominins belong to a single species, their shape variation comprises a more primitive morph that represents a likely candidate for the shape of the last common ancestor of Neanderthals and H. sapiens, and a more derived morph resembling Neanderthals. The arcade shape difference between Neanderthals and H. sapiens might be related to different ways to withstand mechanical stress.

A Force on the Crown and Tug of War in the Periodontal Complex

The load-bearing dentoalveolar fibrous joint is composed of biomechanically active periodontal ligament (PDL), bone, cementum, and the synergistic entheses of PDL-bone and PDL-cementum. Physiologic and pathologic loads on the dentoalveolar fibrous joint prompt natural shifts in strain gradients within mineralized and fibrous tissues and trigger a cascade of biochemical events within the widened and narrowed sites of the periodontal complex. This review highlights data from in situ biomechanical simulations that provide tooth movements relative to the alveolar socket. The methods and subsequent results provide a reasonable approximation of strain-regulated biochemical events resulting in mesial mineral formation and distal resorption events within microanatomical regions at the ligament-tethered/enthesial ends. These biochemical events, including expressions of biglycan, decorin, chondroitin sulfated neuroglial 2, osteopontin, and bone sialoprotein and localization of various hypertrophic progenitors, are observed at the alkaline phosphatase-positive widened site, resulting in mineral formation and osteoid/cementoid layers. On the narrowed side, tartrate-resistant acid phosphatase regions can lead to a sequence of clastic activities resulting in resorption pits in bone and cementum. These strain-regulated biochemical and subsequently biomineralization events in the load-bearing periodontal complex are critical for maintenance of the periodontal space and overall macroscale joint biomechanics.

Skull 5 from Dmanisi: Descriptive anatomy, comparative studies, and evolutionary significance

A fifth hominin skull (cranium D4500 and mandible D2600) from Dmanisi is massively constructed, with a large face and a very small brain. Traits documented for the first time in a basal member of the Homo clade include the uniquely low ratio of endocranial volume to basicranial width, reduced vertex height, angular vault profile, smooth nasal sill coupled with a long and sloping maxillary clivus, elongated palate, and tall mandibular corpus. The convex clivus and receding symphysis of skull 5 produce a muzzle-like form similar to that of Australopithecus afarensis. While the Dmanisi cranium is very robust, differing from OH 13, OH 24, and KNM-ER 1813, it resembles Homo habilis specimens in the "squared off" outline of its maxilla in facial view, maxillary sulcus, rounded and receding zygomatic arch, and flexed zygomaticoalveolar pillar. These characters distinguish early Homo from species of Australopithecus and Paranthropus. Skull 5 is unlike Homo rudolfensis cranium KNM-ER 1470. Although it appears generally primitive, skull 5 possesses a bar-like supraorbital torus, elongated temporal squama, occipital transverse torus, and petrotympanic traits considered to be derived for Homo erectus. As a group, the Dmanisi crania and mandibles display substantial anatomical and metric variation. A key question is whether the fossils document age-related growth and sex dimorphism within a single population, or whether two (or more) distinct taxa may be present at the site. We use the coefficient of variation to compare Dmanisi with Paranthropus boisei, H. erectus, and recent Homo sapiens, finding few signals that the Dmanisi sample is excessively variable in comparison to these reference taxa. Using cranial measurements and principal components analysis, we explore the proposal that the Dmanisi skulls can be grouped within a regionally diverse hypodigm for H. erectus. Our results provide only weak support for this hypothesis. Finally, we consider all available morphological and paleobiological evidence in an attempt to clarify the phyletic relationship of Dmanisi to Homo species evolving >2.0 to 1.0 Ma.

A Critical Evaluation of the Down Syndrome Diagnosis for LB1, Type Specimen of Homo floresiensis

The Liang Bua hominins from Flores, Indonesia, have been the subject of intense scrutiny and debate since their initial description and classification in 2004. These remains have been assigned to a new species, Homo floresiensis, with the partial skeleton LB1 as the type specimen. The Liang Bua hominins are notable for their short stature, small endocranial volume, and many features that appear phylogenetically primitive relative to modern humans, despite their late Pleistocene age. Recently, some workers suggested that the remains represent members of a small-bodied island population of modern Austro-Melanesian humans, with LB1 exhibiting clinical signs of Down syndrome. Many classic Down syndrome signs are soft tissue features that could not be assessed in skeletal remains. Moreover, a definitive diagnosis of Down syndrome can only be made by genetic analysis as the phenotypes associated with Down syndrome are variable. Most features that contribute to the Down syndrome phenotype are not restricted to Down syndrome but are seen in other chromosomal disorders and in the general population. Nevertheless, we re-evaluated the presence of those phenotypic features used to support this classification by comparing LB1 to samples of modern humans diagnosed with Down syndrome and euploid modern humans using comparative morphometric analyses. We present new data regarding neurocranial, brain, and symphyseal shape in Down syndrome, additional estimates of stature for LB1, and analyses of inter- and intralimb proportions. The presence of cranial sinuses is addressed using CT images of LB1. We found minimal congruence between the LB1 phenotype and clinical descriptions of Down syndrome. We present important differences between the phenotypes of LB1 and individuals with Down syndrome, and quantitative data that characterize LB1 as an outlier compared with Down syndrome and non-Down syndrome groups. Homo floresiensis remains a phenotypically unique, valid species with its roots in Plio-Pleistocene Homo taxa.

Comparative analysis of dentognathic pathologies in the Dmanisi mandibles

OBJECTIVES

Due to the scarcity of the fossil record, in vivo changes in the dentognathic system of early Homo are typically documented at the level of individual fossil specimens, and it remains difficult to draw population-level inferences about dietary habits, diet-related activities and lifestyle from individual patterns of dentognathic alterations. The Plio-Pleistocene hominin sample from Dmanisi (Georgia), dated to 1.77 million years ago, offers a unique opportunity to study in vivo changes in the dentognathic system of individuals belonging to a single paleodeme of early Homo.

MATERIALS AND METHODS

We analyze dentognathic pathologies in the Dmanisi sample, and in comparative samples of modern Australian and Greenlander hunter-gatherer populations, applying clinical protocols of dentognathic diagnostics.

RESULTS

The Dmanisi hominins exhibit a similarly wide diversity and similar incidence of dentognathic pathologies as the modern human hunter-gatherer population samples investigated here. Dmanisi differs from the modern population samples in several respects: At young age tooth wear is already advanced, and pathologies are more prevalent. At old age, hypercementosis is substantial.

CONCLUSIONS

Results indicate that dentognathic pathologies and disease trajectories are largely similar in early Homo and modern humans, but that the disease load was higher in early Homo, probably as an effect of higher overall stress on the dentognathic system. Am J Phys Anthropol 160:229-253, 2016. © 2016 Wiley Periodicals, Inc.

Comment on "A complete skull from Dmanisi, Georgia, and the evolutionary biology of early Homo"

Lordkipanidze et al. (Research Article, 18 October 2013, p. 326) conclude, from gross morphological comparisons and geometric-morphometric analysis of general shape, that the five hominid crania from Dmanisi in Georgia represent a single regional variant of Homo erectus. However, dental, mandibular, and cranial morphologies all suggest taxic diversity and, in particular, validate the previously named H. georgicus.

On the variability of the Dmanisi mandibles

The description of a new skull (D4500) from the Dmanisi site (Republic of Georgia) has reopened the debate about the morphological variability within the genus Homo. The new skull fits with a mandible (D2600) often referred as 'big' or 'enigmatic' because of its differences with the other Dmanisi mandibles (D211 and D2735). In this report we present a comparative study of the variability of the Dmanisi mandibles under a different perspective, as we focus in morphological aspects related to growth and development. We have followed the notion of modularity and phenotypic integration in order to understand the architectural differences observed within the sample. Our study reveals remarkable shape differences between D2600 and the other two mandibles, that are established early in the ontogeny (during childhood or even before) and that do not depend on size or sexual dimorphism. In addition, D2600 exhibits a mosaic of primitive and derived features regarding the Homo clade, which is absent in D211 and D2735. This mosaic expression is related to the location of the features and can be explained under the concept of modularity. Our study would support the possibility of two different paleodemes represented at the Dmanisi site. This hypothesis has been previously rejected on the basis that all the individuals were constrained in the same stratigraphic and taphonomic settings. However, our revision of the complex Dmanisi stratigraphy suggests that the accumulation could cover an undetermined period of time. Even if "short" in geological terms, the hominin accumulation was not necessarily synchronic. In the same line we discard that the differences between D2600 and the small mandibles are consequence of wear-related dentoalveolar remodeling. In addition, dental wear pattern of D2600 could suggest an adaptation to a different ecological niche than the other Dmanisi individuals.