Molar crown inner structural organization in JavaneseHomo erectus

Making meaning from fragmentary fossils: Early Homo in the Early to early Middle Pleistocene

In celebration of the 50th anniversary of the Journal of Human Evolution, we re-evaluate the fossil record for early Homo (principally Homo erectus, Homo habilis, and Homo rudolfensis) from early diversification and dispersal in the Early Pleistocene to the ultimate demise of H. erectus in the early Middle Pleistocene. The mid-1990s marked an important historical turning point in our understanding of early Homo with the redating of key H. erectus localities, the discovery of small H. erectus in Asia, and the recovery of an even earlier presence of early Homo in Africa. As such, we compare our understanding of early Homo before and after this time and discuss how the order of fossil discovery and a focus on anchor specimens has shaped, and in many ways biased, our interpretations of early Homo species and the fossils allocated to them. Fragmentary specimens may counter conventional wisdom but are often overlooked in broad narratives. We recognize at least three different cranial and two or three pelvic morphotypes of early Homo. Just one postcranial morph aligns with any certainty to a cranial species, highlighting the importance of explicitly identifying how we link specimens together and to species; we offer two ways of visualizing these connections. Chronologically and morphologically H. erectus is a member of early Homo, not a temporally more recent species necessarily evolved from either H. habilis or H. rudolfensis. Nonetheless, an ancestral-descendant notion of their evolution influences expectations around the anatomy of missing elements, especially the foot. Weak support for long-held notions of postcranial modernity in H. erectus raises the possibility of alternative drivers of dispersal. New observations suggest that the dearth of faces in later H. erectus may mask taxonomic diversity in Asia and suggest various later mid-Pleistocene populations could derive from either Asia or Africa. Future advances will rest on the development of nuanced ways to affiliate fossils, greater transparency of implicit assumptions, and attention to detailed life history information for comparative collections; all critical pursuits for future research given the great potential they have to enrich our evolutionary reconstructions for the next fifty years and beyond.

A Middle Pleistocene Denisovan molar from the Annamite Chain of northern Laos

The Pleistocene presence of the genus Homo in continental Southeast Asia is primarily evidenced by a sparse stone tool record and rare human remains. Here we report a Middle Pleistocene hominin specimen from Laos, with the discovery of a molar from the Tam Ngu Hao 2 (Cobra Cave) limestone cave in the Annamite Mountains. The age of the fossil-bearing breccia ranges between 164–131 kyr, based on the Bayesian modelling of luminescence dating of the sedimentary matrix from which it was recovered, U-series dating of an overlying flowstone, and U-series–ESR dating of associated faunal teeth. Analyses of the internal structure of the molar in tandem with palaeoproteomic analyses of the enamel indicate that the tooth derives from a young, likely female, Homo individual. The close morphological affinities with the Xiahe specimen from China indicate that they belong to the same taxon and that Tam Ngu Hao 2 most likely represents a Denisovan.

Evidence for the presence of Homo during the Middle Pleistocene is limited in continental Southeast Asia. Here, the authors report a hominin molar from Tam Ngu Hao 2 (Cobra Cave), dated to 164–131 kyr. They use morphological and paleoproteomic analysis to show that it likely belonged to a female Denisovan.

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.

Further analyses of the structural organization of Homo luzonensis teeth: Evolutionary implications

The species Homo luzonensis has recently been described based on a set of dental and postcranial elements found at Callao Cave (Northern Luzon, Philippines) and dated to at least 50-67 ka. Seven postcanine maxillary teeth are attributed to this taxon, five of them belonging to the same individual (CCH6) and representing the holotype of H. luzonensis, whereas the isolated upper premolar CCH8 and the upper third molar CCH9 are paratypes of the species. The teeth are characterized by their small dimensions associated with primitive features, as also found in Homo floresiensis, another hominin having evolved in an insular environment of Southeast Asia. Postcranial bones of the hands and feet of H. luzonensis and H. floresiensis show Homo habilis-like or australopith-like features, whereas cranial and dental morphology are more consistent with the Asian Homo erectus morphology. Due to this mosaic morphology, the origin and phylogenetic relationships of both H. luzonensis and H. floresiensis are still debated. To test the hypotheses that H. luzonensis derives from H. erectus or from an earlier small-brained hominin, we analyzed the µCT scans of the teeth. We investigated both external and internal tooth structure using morphometric methods including: crown outline shape, tooth crown tissue proportions, enamel-dentine junction shape, and pulp morphology. Homo luzonensis external crown morphology aligns more with H. erectus than with H. habilis/H. rudolfensis. The internal structural organization of H. luzonensis teeth exhibits more affinities with that of H. erectus and H. floresiensis than with Neanderthals and modern humans. Our results suggest that both H. floresiensis and H. luzonensis likely evolved from some H. erectus groups that dispersed in the various islands of this region and became isolated until endemic speciation events occurred at least twice during the Pleistocene in insular environments.

Premolar enamel thickness and distribution of a Miocene hominid Lufengpithecus hudienensis compared with Pleistocene and extant hominids

Lufengpithecus hudienensis is a Late-Miocene hominid from the Yuanmou basin of southwestern China. Previous studies link Lufengpithecus to either the Sivapithecus-orangutan clade or a derived branch from the basal stem of the Hominidae. Despite a rich fossil assemblage, the taxonomy of L. hudienensis and its phylogenetic relationship with other hominids is still unclear. Enamel thickness in fossil and modern hominids can provide insights into taxonomy, phylogeny, and dietary reconstructions. In this study, 24 upper and lower L. hudienensis premolars were imaged using high-resolution microcomputed tomography. Three-dimensional average enamel thickness and relative enamel thickness (RET) indices, as well as whole-crown enamel distribution patterns were recorded for the L. hudienensis specimens and compared with a total of 113 specimens of fossil and extant apes and recent modern humans (RMH): fossil Pongo (n = 36), Gigantopithecus blacki (n = 21), Pan troglodytes (n = 11), Gorilla gorilla (n = 7), and RMH (n = 38). RET of the premolars of L. hudienensis was found to be similar to that of fossil Pongo, P. troglodytes, and G. gorilla, but less than Gi. blacki and RMH values. The distribution of enamel thickness shows a taxon-specific pattern for L. hudienensis, generally characterized by thicker enamel on the lateral wall than on the cusp apex, on the lingual cusp of the upper and buccal cusp of the lower premolars, with some differences with respect to fossil Pongo, Gi. blacki, P. troglodytes, and G. gorilla patterns. Additional characterizations of enamel thickness distribution patterns of the molars and other dental endostructural morphologies are needed to further explore the phylogenetic relationships of L. hudienensis with other hominids.

Crown tissue proportions and enamel thickness distribution in the Middle Pleistocene hominin molars from Sima de los Huesos (SH) population (Atapuerca, Spain)

Dental enamel thickness, topography, growth and development vary among hominins. In Homo, the thickness of dental enamel in most Pleistocene hominins display variations from thick to hyper-thick, while Neanderthals exhibit proportionally thinner enamel. The origin of the thin trait remains unclear. In this context, the Middle Pleistocene human dental assemblage from Atapuerca-Sima de los Huesos (SH) provides a unique opportunity to trace the evolution of enamel thickness in European hominins. In this study, we aim to test the hypothesis if the SH molar sample approximates the Neanderthal condition for enamel thickness and/or distribution. This study includes 626 molars, both original and comparative data. We analysed the molar inner structural organization of the original collections (n = 124), belonging to SH(n = 72) and modern humans from Spanish origin (n = 52). We compared the SH estimates to those of extinct and extant populations of the genus Homo from African, Asian and European origin (estimates extracted from literature n = 502). The comparative sample included maxillary and mandibular molars belonging to H. erectus, East and North African Homo, European Middle Pleistocene Homo, Neanderthals, and fossil and extant H. sapiens. We used high-resolution images to investigate the endostructural configuration of SH molars (tissue proportions, enamel thickness and distribution). The SH molars exhibit on average thick absolute and relative enamel in 2D and 3D estimates, both in the complete crown and the lateral enamel. This primitive condition is shared with the majority of extinct and extant hominin sample, except for Neanderthals and some isolated specimens. On the contrary, the SH molar enamel distribution maps reveal a distribution pattern similar to the Neanderthal signal (with thicker enamel on the lingual cusps and more peripherally distributed), compared to H. antecessor and modern humans. Due to the phylogenetic position of the SH population, the thick condition in molars could represent the persistence of the plesiomorphic condition in this group. Still, more data is needed on other Early and Middle Pleistocene populations to fully understand the evolutionary meaning of this trait.

Evidence for increased hominid diversity in the Early to Middle Pleistocene of Indonesia

Since the first discovery of Pithecanthropus (Homo) erectus by E. Dubois at Trinil in 1891, over 200 hominid dentognathic remains have been collected from the Early to Middle Pleistocene deposits of Java, Indonesia, forming the largest palaeoanthropological collection in South East Asia. Most of these fossils are currently attributed to H. erectus. However, because of the substantial morphological and metric variation in the Indonesian assemblage, some robust specimens, such as the partial mandibles Sangiran 5 and Sangiran 6a, were formerly variably allocated to other taxa (Meganthropus palaeojavanicus, Pithecanthropus dubius, Pongo sp.). To resolve the taxonomic uncertainty surrounding these and other contentious Indonesian hominid specimens, we used occlusal fingerprint analysis (OFA) to reconstruct their chewing kinematics; we also used various morphometric approaches based on microtomography to examine the internal dental structures. Our results confirm the presence of Meganthropus as a Pleistocene Indonesian hominid distinct from Pongo, Gigantopithecus and Homo, and further reveal that Dubois's H. erectus paratype molars from 1891 are not hominin (human lineage), but instead are more likely to belong to Meganthropus.

Mosaic dental morphology in a terminal Pleistocene hominin from Dushan Cave in southern China

Recent studies reveal high degrees of morphological diversity in Late Pleistocene humans from East Asia. This variability was interpreted as complex demographic patterns with several migrations and possible survival of archaic groups. However, lack of well-described, reliably classified and accurately dated sites has seriously limited understanding of human evolution in terminal Pleistocene. Here we report a 15,000 years-old H. sapiens (Dushan 1) in South China with unusual mosaic features, such as large dental dimensions, cingulum-like structures at the dentine level in the posterior dentition and expression of a "crown buccal vertical groove complex", all of which are uncommon in modern humans and more typically found in Middle Pleistocene archaic humans. They could represent the late survival of one of the earliest modern humans to settle in an isolated region of southern China and, hence, the retention of primitive-like traits. They could also represent a particularity of this group and, hence, reflect a high degree of regional variation. Alternatively, these features may be the result of introgression from some late-surviving archaic population in the region. Our study demonstrates the extreme variability of terminal Pleistocene populations in China and the possibility of a complex demographic story in the region.

Disentangling isolated dental remains of Asian Pleistocene hominins and pongines

Scholars have debated the taxonomic identity of isolated primate teeth from the Asian Pleistocene for over a century, which is complicated by morphological and metric convergence between orangutan (Pongo) and hominin (Homo) molariform teeth. Like Homo erectus, Pongo once showed considerable dental variation and a wide distribution throughout mainland and insular Asia. In order to clarify the utility of isolated dental remains to document the presence of hominins during Asian prehistory, we examined enamel thickness, enamel-dentine junction shape, and crown development in 33 molars from G. H. R. von Koenigswald's Chinese Apothecary collection (11 Sinanthropus officinalis [= Homo erectus], 21 "Hemanthropus peii," and 1 "Hemanthropus peii" or Pongo) and 7 molars from Sangiran dome (either Homo erectus or Pongo). All fossil teeth were imaged with non-destructive conventional and/or synchrotron micro-computed tomography. These were compared to H. erectus teeth from Zhoukoudian, Sangiran and Trinil, and a large comparative sample of fossil Pongo, recent Pongo, and recent human teeth. We find that Homo and Pongo molars overlap substantially in relative enamel thickness; molar enamel-dentine junction shape is more distinctive, with Pongo showing relatively shorter dentine horns and wider crowns than Homo. Long-period line periodicity values are significantly greater in Pongo than in H. erectus, leading to longer crown formation times in the former. Most of the sample originally assigned to S. officinalis and H. erectus shows greater affinity to Pongo than to the hominin comparative sample. Moreover, enamel thickness, enamel-dentine junction shape, and a long-period line periodicity value in the "Hemanthropus peii" sample are indistinguishable from fossil Pongo. These results underscore the need for additional recovery and study of associated dentitions prior to erecting new taxa from isolated teeth.

The Middle Pleistocene (MIS 12) human dental remains from Fontana Ranuccio (Latium) and Visogliano (Friuli-Venezia Giulia), Italy. A comparative high resolution endostructural assessment

The penecontemporaneous Middle Pleistocene sites of Fontana Ranuccio (Latium) and Visogliano (Friuli-Venezia Giulia), set c. 450 km apart in central and northeastern Italy, respectively, have yielded some among the oldest human fossil remains testifying to a peopling phase of the Italian Peninsula broadly during the glacial MIS 12, a stage associated with one among the harshest climatic conditions in the Northern hemisphere during the entire Quaternary period. Together with the large samples from Atapuerca Sima de los Huesos, Spain, and Caune de l’Arago at Tautavel, France, the remains from Fontana Ranuccio and Visogliano are among the few mid-Middle Pleistocene dental assemblages from Western Europe available for investigating the presence of an early Neanderthal signature in their inner structure. We applied two- three-dimensional techniques of virtual imaging and geometric morphometrics to the high-resolution X-ray microtomography record of the dental remains from these two Italian sites and compared the results to the evidence from a selected number of Pleistocene and extant human specimens/samples from Europe and North Africa. Depending on their preservation quality and on the degree of occlusal wear, we comparatively assessed: (i) the crown enamel and radicular dentine thickness topographic variation of a uniquely represented lower incisor; (ii) the lateral crown tissue proportions of premolars and molars; (iii) the enamel-dentine junction, and (iv) the pulp cavity morphology of all available specimens. Our analyses reveal in both samples a Neanderthal-like inner structural signal, for some aspects also resembling the condition shown by the contemporary assemblage from Atapuerca SH, and clearly distinct from the recent human figures. This study provides additional evidence indicating that an overall Neanderthal morphological dental template was preconfigured in Western Europe at least 430 to 450 ka ago.

Tooth crown tissue proportions and enamel thickness in Early Pleistocene Homo antecessor molars (Atapuerca, Spain)

Tooth crown tissue proportions and enamel thickness distribution are considered reliable characters for inferring taxonomic identity, phylogenetic relationships, dietary and behavioural adaptations in fossil and extant hominids. While most Pleistocene hominins display variations from thick to hyper-thick enamel, Neanderthals exhibit relatively thinner. However, the chronological and geographical origin for the appearance of this typical Neanderthal condition is still unknown. The European late Early Pleistocene species Homo antecessor (Gran Dolina-TD6 site, Sierra de Atapuerca) represents an opportunity to investigate the appearance of the thin condition in the fossil record. In this study, we aim to test the hypothesis if H. antecessor molars approximates the Neanderthal condition for tissue proportions and enamel thickness. To do so, for the first time we characterised the molar inner structural organization in this Early Pleistocene hominin taxon (n = 17) and compared it to extinct and extant populations of the genus Homo from African, Asian and European origin (n = 355). The comparative sample includes maxillary and mandibular molars belonging to H. erectus, East and North African Homo, European Middle Pleistocene Homo, Neanderthals, and fossil and extant H. sapiens. We used high-resolution images to investigate the endostructural configuration of TD6 molars (tissue proportions, enamel thickness and distribution). TD6 permanent molars tend to exhibit on average thick absolute and relative enamel in 2D and 3D estimates, both in the complete crown and the lateral enamel. This condition is shared with the majority of extinct and extant hominin sample, except for Neanderthals and some isolated specimens. However, while the total crown percentage of dentine in TD6 globally resembles the low modern values, the lateral crown percentage of dentine tends to be much higher, closer to the Neanderthal signal. Similarly, the H. antecessor molar enamel distribution maps reveal a relative distribution pattern that is more similar to the Neanderthal condition (with the thickest enamel more spread at the periphery of the occlusal basin) rather than that of other fossil specimens and modern humans (with thicker cuspal enamel). Future studies on European Middle Pleistocene populations will provide more insights into the evolutionary trajectory of the typical Neanderthal dental structural organization.

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.

The fossil teeth of the Peking Man

This study provides new original data, including the endostructure of most Zhoukoudian H. erectus teeth preserved to date, since the publication of Black in 1927 and Weidenreich in 1937. The new evidence ratifies the similarities of Zhoukoudian with other East Asian mid-Middle Pleistocene hominins such as Hexian and Yiyuan, and allows defining a dental pattern potentially characteristic of this population commonly referred to as classic H. erectus. Given the possible chronological overlaps of classic H. erectus with other archaic Homo, the characterization of this group becomes a key issue when deciphering the taxonomy and evolutionary scenario of the Middle Pleistocene hominins in East Asia. Internally, the most remarkable feature of Zhoukoudian teeth is the highly crenulated enamel-dentine junction (EDJ) and its imprint on the roof of the pulp cavity. So far, this "dendrite-like" EDJ has been found only in East Asia Middle Pleistocene hominins although a large group of samples were assessed, and it could be useful to dentally define classic H. erectus in China. The crenulated EDJ surface, together with the stout roots and the taurodontism could be a mechanism to withstand high biomechanical demand despite a general dentognathic reduction, particularly of the crowns, in these populations.

The potential of statistical shape modelling for geometric morphometric analysis of human teeth in archaeological research

This paper introduces statistical shape modelling (SSM) for use in osteoarchaeology research. SSM is a full field, multi-material analytical technique, and is presented as a supplementary geometric morphometric (GM) tool. Lower mandibular canines from two archaeological populations and one modern population were sampled, digitised using micro-CT, aligned, registered to a baseline and statistically modelled using principal component analysis (PCA). Sample material properties were incorporated as a binary enamel/dentin parameter. Results were assessed qualitatively and quantitatively using anatomical landmarks. Finally, the technique’s application was demonstrated for inter-sample comparison through analysis of the principal component (PC) weights. It was found that SSM could provide high detail qualitative and quantitative insight with respect to archaeological inter- and intra-sample variability. This technique has value for archaeological, biomechanical and forensic applications including identification, finite element analysis (FEA) and reconstruction from partial datasets.

Neanderthal and Denisova tooth protein variants in present-day humans

Environment parameters, diet and genetic factors interact to shape tooth morphostructure. In the human lineage, archaic and modern hominins show differences in dental traits, including enamel thickness, but variability also exists among living populations. Several polymorphisms, in particular in the non-collagenous extracellular matrix proteins of the tooth hard tissues, like enamelin, are involved in dental structure variation and defects and may be associated with dental disorders or susceptibility to caries. To gain insights into the relationships between tooth protein polymorphisms and dental structural morphology and defects, we searched for non-synonymous polymorphisms in tooth proteins from Neanderthal and Denisova hominins. The objective was to identify archaic-specific missense variants that may explain the dental morphostructural variability between extinct and modern humans, and to explore their putative impact on present-day dental phenotypes. Thirteen non-collagenous extracellular matrix proteins specific to hard dental tissues have been selected, searched in the publicly available sequence databases of Neanderthal and Denisova individuals and compared with modern human genome data. A total of 16 non-synonymous polymorphisms were identified in 6 proteins (ameloblastin, amelotin, cementum protein 1, dentin matrix acidic phosphoprotein 1, enamelin and matrix Gla protein). Most of them are encoded by dentin and enamel genes located on chromosome 4, previously reported to show signs of archaic introgression within Africa. Among the variants shared with modern humans, two are ancestral (common with apes) and one is the derived enamelin major variant, T648I (rs7671281), associated with a thinner enamel and specific to the Homo lineage. All the others are specific to Neanderthals and Denisova, and are found at a very low frequency in modern Africans or East and South Asians, suggesting that they may be related to particular dental traits or disease susceptibility in these populations. This modern regional distribution of archaic dental polymorphisms may reflect persistence of archaic variants in some populations and may contribute in part to the geographic dental variations described in modern humans.

A mandible from the Middle Pleistocene Hexian site and its significance in relation to the variability of Asian Homo erectus

OBJECTIVES

This study presents the first detailed morphological description and comparison of a Middle Pleistocene hominin mandibular fragment (PA 831) and associated teeth from the Hexian site in Eastern China. We aim to investigate where the Hexian mandible fits within the genus Homo variability in the light of an increased and better characterized Asian fossils record.

METHODS

Comparative samples include Pleistocene Homo mandibles and teeth from Africa, Asia, and Europe, as well as earlier African hominins (Australopithecus and early Homo) and Holocene recent humans. Both conventional morphological description and metric analysis were used. In addition, virtual reconstructions of the enamel dentine junction (EDJ) surface, pulp cavity, and roots with micro-CT were used to the mandible and teeth.

RESULTS

The Hexian mandible is characterized by a plesiomorphic structural pattern for the Homo clade, with strong corpus robustness and a subparallel and low-positioned mylohyoid line that differentiates the swollen subalveolar planum from the shallow subalveolar fossa. Features that are derived compared to early Homo include a moderately curved dental arcade, a well-developed lateral prominence placed at the M₂ -M₃ level, and multiple mental foramina. The Hexian mandible's complex enamel surface and strong, stout root structure are primitive traits for the Homo clade. Finally, the highly crenulated "dendrite-like" EDJ found in the molars may represent a dental feature specific to the continental Asian Homo erectus, but more data is needed to confirm this.

CONCLUSIONS

Mandibular and dental features indicate that the Hexian mandible and teeth differ from northern Chinese H. erectus and European Middle Pleistocene hominins, but show some affinities with the Early Pleistocene specimens from Africa (Homo ergaster) and Java (H. erectus), as well as the Middle-Late Pleistocene mandible from Penghu, Taiwan. Compared to contemporaneous continental Asian hominin populations, the Hexian fossils may represent the survival of a primitive hominin, with more primitive morphologies than other contemporaneous or some chronologically older Asian hominin specimens.

Unique Dental Morphology of Homo floresiensis and Its Evolutionary Implications

Homo floresiensis is an extinct, diminutive hominin species discovered in the Late Pleistocene deposits of Liang Bua cave, Flores, eastern Indonesia. The nature and evolutionary origins of H. floresiensis' unique physical characters have been intensively debated. Based on extensive comparisons using linear metric analyses, crown contour analyses, and other trait-by-trait morphological comparisons, we report here that the dental remains from multiple individuals indicate that H. floresiensis had primitive canine-premolar and advanced molar morphologies, a combination of dental traits unknown in any other hominin species. The primitive aspects are comparable to H. erectus from the Early Pleistocene, whereas some of the molar morphologies are more progressive even compared to those of modern humans. This evidence contradicts the earlier claim of an entirely modern human-like dental morphology of H. floresiensis, while at the same time does not support the hypothesis that H. floresiensis originated from a much older H. habilis or Australopithecus-like small-brained hominin species currently unknown in the Asian fossil record. These results are however consistent with the alternative hypothesis that H. floresiensis derived from an earlier Asian Homo erectus population and experienced substantial body and brain size dwarfism in an isolated insular setting. The dentition of H. floresiensis is not a simple, scaled-down version of earlier hominins.