A new skull of early Homo from Dmanisi, Georgia

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.

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.

Early Pleistocene stratigraphy, sedimentary environments, and formation contexts at Dmanisi in the Georgian Caucasus

The Early Pleistocene site of Dmanisi is now well known for its large number of fossils of early Homo erectus as well as associated artifacts and faunal remains, recovered mainly in pipe-related geologic features. Testing in the M5 unit 100 m to the west of the main excavations revealed a thick stratigraphy with no evidence of pipes or gullies, indicating that the geologic record at Dmanisi included spatially distinct sedimentary environments that needed further investigation. Here we report the results of a geoarchaeological program to collect data bearing on contexts and formation processes over a large area of the promontory. That work has defined over 40,000 m² of in situ deposits with artifacts and faunas. Stratum A ashes bury the uppermost Mashavera Basalt, which we have dated to 1.8 Ma in the M5 block. The Stratum A deposits contain stratified occupations that accumulated quickly and offer good potential for recovery of in situ materials. Stratum B1 deposits above the A/B unconformity include all of the pipe and gully facies at Dmanisi, reflecting a brief but very intense phase of geomorphic change. Those deposits contain the majority of faunas and all of the hominin fossils. B1 slope facies offer excellent formation contexts away from the piped area, and all B1 deposits are sealed by Stratum B2 over the whole promontory. Strata B2 to B5 register a return to slope facies, with no further evidence of pipes or gullies. Those deposits also present excellent contexts for recovery of in situ occupations. Overall, Dmanisi's geologic history preserves an exceptional record of the activities and environmental context of occupations during the first colonization of Eurasia.

Small mammals (Insectivora, Rodentia, Lagomorpha) from the Early Pleistocene hominin-bearing site of Dmanisi (Georgia)

Small mammals (insectivores, rodents, and lagomorphs) from Dmanisi are here reviewed for the first time and used as a tool for paleoenvironmental proxies. The small mammal faunal list is composed of shrews (Beremendia fissidens, cf. Beremendia minor, Crocidura kornfeldi), hamsters (Cricetulus sp., Allocricetus bursae), gerbils (Parameriones aff. obeidiyensis), murids (Apodemus cf. atavus), arvicolids (Mimomys pliocaenicus, Mimomys aff. pusillus), and pikas (Ochotona sp.). A paleoenvironmental reconstruction based on the habitat weighting method has been applied to the rodent assemblage. According to this method, the most common elements indicate an open-dry habitat (36.5%), followed by water edge (25.7%) and rocky (21.0%) elements. Open-wet (15.5%) and woodland elements (1.3%) are rare. Therefore, the habitat occupied by the hominids of Dmanisi was characterized by the prevalence of arid conditions, from steppe or semi-desert to open Mediterranean forest, with stony or rocky substrate and bushy areas. The presence of permanent aquatic environments is also documented. From a biogeographic point of view, the small mammal community from Dmanisi is composed mainly by Western or Central Asian elements, with a poor representation of European elements (Mimomys, Apodemus). It is concluded that Dmanisi hominins most possibly had ecological requirements which were different from those of the Early Pleistocene hominins from Western Europe, which settled on wetter habitats. It could be also possible that Dmanisi hominins entered Southern Caucasus at an interglacial phase before the deposition of the Dmanisi site.

A comparative study of the Early Pleistocene carnivore guild from Dmanisi (Georgia)

The carnivore guild of the Early Pleistocene site of Dmanisi is among the most diverse of the Early Pleistocene of the entire Old World. It includes 14 carnivoran taxa: Homotherium latidens, Megantereon whitei, Panthera onca georgica, Acinonyx pardinensis, Lynx issiodorensis; Pachycrocuta brevirostris; Canis (Xenocyon) lycaonoides, Canis borjgali, Vulpes alopecoides; Ursus etruscus; Lutra sp., Martes sp., Meles sp., and Pannonictis sp. The analysis of this rich carnivore guild was carried out under different methodological approaches to compare the assemblage with other chronological coeval European, Asian, and African sites from a paleobiological perspective. To achieve the goal, we used a permutational hierarchical method called boostrapping cluster analysis based on taxonomic absence/presence matrices (at both generic and specific level) and on ecological matrices (considering dietary preferences/hunting strategies of each carnivoran) and carried out Mantels tests assessing magnitude of time, space, ecology, and taxonomy as source of difference between guilds. Our results suggest a close similarity among the Dmanisi carnivore assemblage and other guilds recorded from European late Villafranchian sites such as Pirro Nord, Venta Micena, and Apollonia 1 and, in a lesser extent, to European Epivillafranchian sites as Vallonnet, Untermassfeld, or the Vallparadís Section. Early to Middle Pleistocene Asian carnivore assemblages display several similarities with the Dmanisi guild mainly in the record and diversity of felid and the canid ecomorphotypes. Eastern African sites such as Olduvai and Omo, as well as South African sites, display a lower similarity with the studied sample, basically for the most diverse hyenid taphocoenoses. To sum up, the present study suggests a close similarity between the Dmanisi carnivore guild and other European Late Early Pleistocene assemblages without close parallels with African or Asian assemblages.

The primitive brain of early Homo

The brains of modern humans differ from those of great apes in size, shape, and cortical organization, notably in frontal lobe areas involved in complex cognitive tasks, such as social cognition, tool use, and language. When these differences arose during human evolution is a question of ongoing debate. Here, we show that the brains of early Homo from Africa and Western Asia (Dmanisi) retained a primitive, great ape-like organization of the frontal lobe. By contrast, African Homo younger than 1.5 million years ago, as well as all Southeast Asian Homo erectus, exhibited a more derived, humanlike brain organization. Frontal lobe reorganization, once considered a hallmark of earliest Homo in Africa, thus evolved comparatively late, and long after Homo first dispersed from Africa.

Continuous presence of proto-cereals in Anatolia since 2.3 Ma, and their possible co-evolution with large herbivores and hominins

Cereals are a central resource for the human diet and are traditionally assumed to have evolved from wild grasses at the onset of the Neolithic under the pressure of agriculture. Here we demonstrate that cereals may have a significantly longer and more diverse lineage, based on the study of a 0-2.3 Ma, 601 m long sedimentary core from Lake Acıgöl (South-West Anatolia). Pollen characteristic of cereals is abundant throughout the sedimentary sequence. The presence of large lakes within this arid bioclimatic zone led to the concentration of large herbivore herds, as indicated by the continuous occurrence of coprophilous fungi spores in the record. Our hypothesis is that the effects of overgrazing on soils and herbaceous stratum, during this long period, led to genetic modifications of the Poaceae taxa and to the appearance of proto-cereals. The simultaneous presence of hominins is attested as early as about 1.4 Ma in the lake vicinity, and 1.8 Ma in Georgia and Levant. These ancient hominins probably benefited from the availability of these proto-cereals, rich in nutrients, as well as various other edible plants, opening the way, in this region of the Middle East, to a process of domestication, which reached its full development during the Neolithic.

Coping with arid environments: A critical threshold for human expansion in Europe at the Marine Isotope Stage 12/11 transition? The case of the Iberian Peninsula

Archaeological remains have highlighted the fact that the interglacial Marine Isotope Stage (MIS) 11 was a threshold from the perspective of hominin evolution in Europe. After the MIS 12 glaciation, considered one of the major climate-driven crises experienced by hominins, the archaeological records show an increasing number of occupations, evidence of new subsistence behaviors, and significant technical innovations. Here, we used statistical and geographic techniques to analyze the amphibian- and reptile-based paleoclimate and habitat reconstructions generated from a large data set of the Iberian Peninsula to (1) investigate if temperature, precipitation, and/or forest cover may have impacted the hominin occupation of the territory during the Early and Middle Pleistocene, (2) propose an 'Iberian' ecological model before and after the MIS 12/11 transition, and (3) evaluate, based on this model, the potential hominin occupation at a European scale. The results indicate the existence of climatic constraints on human settlement related to rainfall and environmental humidity. The Early Pleistocene and the first half of the Middle Pleistocene are dominated by the occupation of relatively humid wooded areas, whereas during the second part of the Middle Pleistocene, a broadening of the earlier ecological niche is clearly observed toward the occupation of more open arid areas. Based on the estimated occupational niche for hominins, a maximum potential distribution for early hominins is proposed in Europe before and after 426 ka. Results also indicate that parts of the Iberian Peninsula may not have been suitable for early hominin occupation. Our ecological model is consistent with the pattern of hominin occupation observed in northern and central Europe, where the earliest evidence reflects only pioneering populations merely extending their ranges in response to the expansion of their preferred habitats, as compared with a more sustained occupation by 400 ka.

Growth and development of the third permanent molar in Paranthropus robustus from Swartkrans, South Africa

Third permanent molars (M3s) are the last tooth to form but have not been used to estimate age at dental maturation in early fossil hominins because direct histological evidence for the timing of their growth has been lacking. We investigated an isolated maxillary M3 (SK 835) from the 1.5 to 1.8-million-year-old (Mya) site of Swartkrans, South Africa, attributed to Paranthropus robustus. Tissue proportions of this specimen were assessed using 3D X-ray micro-tomography. Thin ground sections were used to image daily growth increments in enamel and dentine. Transmitted light microscopy and synchrotron X-ray fluorescence imaging revealed fluctuations in Ca concentration that coincide with daily growth increments. We used regional daily secretion rates and Sr marker-lines to reconstruct tooth growth along the enamel/dentine and then cementum/dentine boundaries. Cumulative growth curves for increasing enamel thickness and tooth height and age-of-attainment estimates for fractional stages of tooth formation differed from those in modern humans. These now provide additional means for assessing late maturation in early hominins. M3 formation took ≥ 7 years in SK 835 and completion of the roots would have occurred between 11 and 14 years of age. Estimated age at dental maturation in this fossil hominin compares well with what is known for living great apes.

Reassessment of the TM 1517 odonto-postcranial assemblage from Kromdraai B, South Africa, and the maturational pattern of Paranthropus robustus

OBJECTIVES

The Pleistocene taxon Paranthropus robustus was established in 1938 following the discovery at Kromdraai B, South Africa, of the partial cranium TM 1517a and associated mandible TM 1517b. Shortly thereafter, a distal humerus (TM 1517g), a proximal ulna (TM 1517e), and a distal hallucial phalanx (TM 1517k) were collected nearby at the site, and were considered to be associated with the holotype. TM 1517a-b represents an immature individual; however, no analysis of the potentially associated postcranial elements has investigated the presence of any endostructural remnant of recent epiphyseal closure. This study aims at tentatively detecting such traces in the three postcranial specimens from Kromdraai B.

MATERIALS AND METHODS

By using μXCT techniques, we assessed the developmental stage of the TM 1517b's C-M3 roots and investigated the inner structure of TM 1517g, TM 1517e, and TM 1517k.

RESULTS

The M2 shows incompletely closed root apices and the M3 a half-completed root formation stage. The distal humerus was likely completely fused, while the proximal ulna and the distal hallucial phalanx preserve endosteal traces of the diaphyseo-epiphyseal fusion process.

DISCUSSION

In the hominin fossil record, there are few unambiguously associated craniodental and postcranial remains sampling immature individuals, an essential condition for assessing the taxon-specific maturational patterns. Our findings corroborate the original association of the craniodental and postcranial remains representing the P. robustus type specimen. As with other Plio-Pleistocene hominins, the odonto-postcranial maturational pattern of TM 1517 more closely fits an African great ape rather than the extant human pattern.

The bears from Dmanisi and the first dispersal of early Homo out of Africa

We report on the taxonomy and paleodiet of the bear population that inhabited the emblematic palaeoanthropological Early Pleistocene (1.8 Ma) site of Dmanisi (Georgia), based on a dual approach combining morphometrics and microwear of upper and lower teeth. Given that the teeth of Ursus etruscus Cuvier, 1823 from Dmanisi show considerable size variability, their systematic position has been debated. However, a comparative study of the coefficients of variation for tooth size measurements in several modern bear species shows that the variability in tooth size of the ursid population from Dmanisi could result from sexual dimorphism. The analysis of tooth microwear indicates that these bears inhabited a mixed environment of open plain with forest patches, where they had a browsing diet with a substantial contribution of meat and/or fish. Comparative tooth morphometric analyses of modern ursids and fossil U. etruscus indicate that this extinct species had an omnivorous behavior similar to that of extant brown bears. The ecological interactions of the Dmanisi bears with other members of the large mammals community, including the first hominins that dispersed out of Africa, are discussed in the light of this new evidence.

Human behavior and Homo-mammal interactions at the first European peopling: new evidence from the Pirro Nord site (Apricena, Southern Italy)

Recent functional and zooarchaeological studies conducted on the archeological finds of Pirro Nord (PN13) produced new, reliable data on early European hominid subsistence activities. The age of the site is estimated to be ~ 1.3-1.6 Ma, based on bio-chronological data, and the archeological excavation of the Pirro Nord 13 fissure led to the discovery of more than 300 lithic artifacts associated with thousands of vertebrate fossil remains of the final Villafranchian (Pirro Nord Faunal Unit). The analysis of the fossil faunal remains allowed for the identification of anthropogenic traces linked to the exploitation of different animal carcass (cut marks and intentional bone breakages). Use-wear traces were also observed on some flint artifacts and have been interpreted as the result of the exploitation of animal resources by early hominids and carnivores. It has not been possible to identify the type of access that hominins developed on the carcasses, although it has been established that the hominins competed with carnivores for animal resources. The stone tools and faunal remains with anthropogenic traces recovered in the PN13 fissure represent among the earliest evidence of hominin faunal exploitation in Europe.

Complete permanent mandibular dentition of early Homo from the upper Burgi Member of the Koobi Fora Formation, Ileret, Kenya

The KNM-ER 64060 dentition derives from a horizon that most likely dates to between 2.02 and 2.03 Ma. A proximate series of postcranial bones (designated KNM-ER 64061) derives from the same siltstone unit and may be associated with the dentition, but their separation on the surface of the site leaves some room for doubt. KNM-ER 64060 is one of fewer than ten hominin specimens from the Early Pleistocene of East Africa that comprises a full or nearly complete mandibular dentition. Its taxonomic attribution is potentially significant, especially if the postcranial elements are related. At least three, and probably four hominin species, including Paranthropus boisei and Homo erectus (= H. ergaster), are known at about this time in East Africa. Other penecontemporaneous fossils have been referred to a single, highly variable species, H. habilis, or two taxa, namely H. habilis and H. rudolfensis. Although the weight of evidence supports the attribution of these specimens to two species, there is notable lack of agreement over the assignation of individual fossils. We take a conservative approach and group all such specimens under the designation "early Homo sp." for comparative purposes. KNM-ER 64060 is clearly attributable to Homo rather than Paranthropus. The preponderance of the evidence suggests that the affinities of KNM-ER 64060 are with fossils assigned to the early Homo sp. category rather than with H. erectus. This is indicated by the overall sizes of the KNM-ER 64060 canine, premolar and molar crowns, the size relationships of the P₃ to P₄, the relative narrowness of its premolar crowns, the cusp proportions of the M₁ and especially those of the M₂ and M₃, and seemingly the possession of a two-rooted P₄. Some of these comparisons suggest further that among the fossils comprising the early Homo sp. sample, the KNM-ER 64060 dentition exhibits greater overall similarity to specimens such as OH 7 and OH 16 that represent Homo habilis sensu stricto.

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.

Functional and molecular outcomes of the human masticatory muscles

The masticatory muscles achieve a broad range of different activities such as chewing, sucking, swallowing, and speech. In order to accomplish these duties, masticatory muscles have a unique and heterogeneous structure and fiber composition, enabling them to produce their strength and contraction speed largely dependent on their motor units and myosin proteins that can change in response to genetic and environmental factors. Human masticatory muscles express unique myosin isoforms, including a combination of thick fibers, expressing myosin light chains (MyLC) and myosin class I and II heavy chains (MyHC) -IIA, -IIX, α-cardiac, embryonic and neonatal and thin fibers, respectively. In this review, we discuss the current knowledge regarding the importance of fiber-type diversity in masticatory muscles versus supra- and infrahyoid muscles, and versus limb and trunk muscles. We also highlight new information regarding the adaptive response and specific genetic variations of muscle fibers on the functional significance of the masticatory muscles, which influences craniofacial characteristics, malocclusions, or asymmetry. These findings may offer future possibilities for the prevention of craniofacial growth disturbances.

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.

The affinities of Homo antecessor – a review of craniofacial features and their taxonomic validity

The phylogenetic affinities of Homo antecessor, a hominin dating from the early Middle Pleistocene of Europe, are still unclear. In this study we conducted a comprehensive review of the TD6 hypodigm within the context of the historical development of paleoanthropological issues concerning this species. H. antecessor, based on all available craniofacial features to date, displays a midfacial morphology very similar to specimens attributed to Classic Homo erectus, suggesting that H. antecessor is the geographical European variant of Classic H. erectus.

Early Homo, plasticity and the extended evolutionary synthesis

The Modern Synthesis led to fundamental advances in understandings of human evolution. For human palaeontology, a science that works from ancestral phenotypes (i.e. the fossil record), particularly important have been perspectives used to help understand the heritable aspects of phenotypes and how fossil individuals might then be aggregated into species, and relationships among these groups understood. This focus, coupled with the fragmentary nature of the fossil record, however, means that individual phenotypic variation is often treated as unimportant 'noise', rather than as a source of insight into population adaptation and evolutionary process. The emphasis of the extended evolutionary synthesis on plasticity as a source of phenotypic novelty, and the related question of the role of such variation in long-term evolutionary trends, focuses welcome attention on non-genetic means by which novel phenotypes are generated and in so doing provides alternative approaches to interpreting the fossil record. We review evidence from contemporary human populations regarding some of the aspects of adult phenotypes preserved in the fossil record that might be most responsive to non-genetic drivers, and we consider how these perspectives lead to alternate hypotheses for interpreting the fossil record of early genus Homo. We conclude by arguing that paying closer attention to the causes and consequences of intraspecific phenotypic variation in its own right, as opposed to as noise around a species mean, may inspire a new generation of hypotheses regarding species diversity in the Early Pleistocene and the foundations for dispersal and regional diversification in Homo erectus and its descendants.

The earliest evidence for Upper Paleolithic occupation in the Armenian Highlands at Aghitu-3 Cave

With its well-preserved archaeological and environmental records, Aghitu-3 Cave permits us to examine the settlement patterns of the Upper Paleolithic (UP) people who inhabited the Armenian Highlands. We also test whether settlement of the region between ∼39-24,000 cal BP relates to environmental variability. The earliest evidence occurs in archaeological horizon (AH) VII from ∼39-36,000 cal BP during a mild, moist climatic phase. AH VI shows periodic occupation as warm, humid conditions prevailed from ∼36-32,000 cal BP. As the climate becomes cooler and drier at ∼32-29,000 cal BP (AH V-IV), evidence for occupation is minimal. However, as cooling continues, the deposits of AH III demonstrate that people used the site more intensively from ∼29-24,000 cal BP, leaving behind numerous stone artifacts, faunal remains, and complex combustion features. Despite the climatic fluctuations seen across this 15,000-year sequence, lithic technology remains attuned to one pattern: unidirectional reduction of small cores geared towards the production of bladelets for tool manufacture. Subsistence patterns also remain stable, focused on medium-sized prey such as ovids and caprids, as well as equids. AH III demonstrates an expansion of social networks to the northwest and southwest, as the transport distance of obsidian used to make stone artifacts increases. We also observe the addition of bone tools, including an eyed needle, and shell beads brought from the east, suggesting that these people manufactured complex clothing and wore ornaments. Remains of micromammals, birds, charcoal, pollen, and tephra relate the story of environmental variability. We hypothesize that UP behavior was linked to shifts in demographic pressures and climatic changes. Thus, by combining archaeological and environmental data, we gain a clearer picture about the first UP inhabitants of the Armenian Highlands.

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.

Bayesian analysis of a morphological supermatrix sheds light on controversial fossil hominin relationships

The phylogenetic relationships of several hominin species remain controversial. Two methodological issues contribute to the uncertainty-use of partial, inconsistent datasets and reliance on phylogenetic methods that are ill-suited to testing competing hypotheses. Here, we report a study designed to overcome these issues. We first compiled a supermatrix of craniodental characters for all widely accepted hominin species. We then took advantage of recently developed Bayesian methods for building trees of serially sampled tips to test among hypotheses that have been put forward in three of the most important current debates in hominin phylogenetics--the relationship between Australopithecus sediba and Homo, the taxonomic status of the Dmanisi hominins, and the place of the so-called hobbit fossils from Flores, Indonesia, in the hominin tree. Based on our results, several published hypotheses can be statistically rejected. For example, the data do not support the claim that Dmanisi hominins and all other early Homo specimens represent a single species, nor that the hobbit fossils are the remains of small-bodied modern humans, one of whom had Down syndrome. More broadly, our study provides a new baseline dataset for future work on hominin phylogeny and illustrates the promise of Bayesian approaches for understanding hominin phylogenetic relationships.

Human Brain Expansion during Evolution Is Independent of Fire Control and Cooking

What makes humans unique? This question has fascinated scientists and philosophers for centuries and it is still a matter of intense debate. Nowadays, human brain expansion during evolution has been acknowledged to explain our empowered cognitive capabilities. The drivers for such accelerated expansion remain, however, largely unknown. In this sense, studies have suggested that the cooking of food could be a pre-requisite for the expansion of brain size in early hominins. However, this appealing hypothesis is only supported by a mathematical model suggesting that the increasing number of neurons in the brain would constrain body size among primates due to a limited amount of calories obtained from diets. Here, we show, by using a similar mathematical model, that a tradeoff between body mass and the number of brain neurons imposed by dietary constraints during hominin evolution is unlikely. Instead, the predictable number of neurons in the hominin brain varies much more in function of foraging efficiency than body mass. We also review archeological data to show that the expansion of the brain volume in the hominin lineage is described by a linear function independent of evidence of fire control, and therefore, thermal processing of food does not account for this phenomenon. Finally, we report experiments in mice showing that thermal processing of meat does not increase its caloric availability in mice. Altogether, our data indicate that cooking is neither sufficient nor necessary to explain hominin brain expansion.

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.

Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa

Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.

Diagnosing Homo sapiens in the fossil record

BACKGROUND

Diagnosing Homo sapiens is a critical question in the study of human evolution. Although what constitutes living members of our own species is straightforward, in the fossil record this is still a matter of much debate. The issue is complicated by questions of species diagnoses and ideas about the mode by which a new species is born, by the arguments surrounding the behavioural and cognitive separateness of the species, by the increasing appreciation of variation in the early African H. sapiens record and by new DNA evidence of hybridization with extinct species.

METHODS AND RESULTS

This study synthesizes thinking on the fossils, archaeology and underlying evolutionary models of the last several decades with recent DNA results from both H. sapiens and fossil species.

CONCLUSION

It is concluded that, although it may not be possible or even desirable to cleanly partition out a homogenous morphological description of recent H. sapiens in the fossil record, there are key, distinguishing morphological traits in the cranium, dentition and pelvis that can be usefully employed to diagnose the H. sapiens lineage. Increasing advances in retrieving and understanding relevant genetic data provide a complementary and perhaps potentially even more fruitful means of characterizing the differences between H. sapiens and its close relatives.

The role of character displacement in the molarization of hominin mandibular premolars

Closely related species are likely to experience resource competition in areas where their ranges overlap. Fossil evidence suggests that hominins in East Africa c. 2-1.5 million years ago may have lived synchronically and sympatrically, and that competition may have contributed to the different tooth sizes observed in Homo and Paranthropus. To assess the likelihood that these taxa overlapped, we applied a character displacement model to the postcanine tooth size of fossil hominins and validated this model in populations of living primates. Mandibular fourth premolar (P4 ) crown size was measured from fossil taxa and from living primate species where dietary overlap is established. Dimensions of the P4 crown were fitted to a character matrix and described as the response variables of a generalized linear model that took taxon and location as input variables. The model recovered significant divergence in samples of closely related, living primates. When applied to fossil hominins the same model detected strong indications of character displacement between early Homo and Paranthropus (P = 0.002) on the basis of their P4 crown size. Our study is an example of how ecologically informed morphologies measured in appropriate extant referents can provide a comparative context for assessing community and ecological evolution in the fossil record.

Spatial and temporal variation of body size among early Homo

The estimation of body size among the earliest members of the genus Homo (2.4-1.5Myr [millions of years ago]) is central to interpretations of their biology. It is widely accepted that Homo ergaster possessed increased body size compared with Homo habilis and Homo rudolfensis, and that this may have been a factor involved with the dispersal of Homo out of Africa. The study of taxonomic differences in body size, however, is problematic. Postcranial remains are rarely associated with craniodental fossils, and taxonomic attributions frequently rest upon the size of skeletal elements. Previous body size estimates have been based upon well-preserved specimens with a more reliable species assessment. Since these samples are small (n < 5) and disparate in space and time, little is known about geographical and chronological variation in body size within early Homo. We investigate temporal and spatial variation in body size among fossils of early Homo using a 'taxon-free' approach, considering evidence for size variation from isolated and fragmentary postcranial remains (n = 39). To render the size of disparate fossil elements comparable, we derived new regression equations for common parameters of body size from a globally representative sample of hunter-gatherers and applied them to available postcranial measurements from the fossils. The results demonstrate chronological and spatial variation but no simple temporal or geographical trends for the evolution of body size among early Homo. Pronounced body size increases within Africa take place only after hominin populations were established at Dmanisi, suggesting that migrations into Eurasia were not contingent on larger body sizes. The primary evidence for these marked changes among early Homo is based upon material from Koobi Fora after 1.7Myr, indicating regional size variation. The significant body size differences between specimens from Koobi Fora and Olduvai support the cranial evidence for at least two co-existing morphotypes in the Early Pleistocene of eastern Africa.

Trend of different molecular markers in the last decades for studying human migrations

Anatomically modern humans are known to have widely migrated throughout history. Different scientific evidences suggest that the entire human population descended from just several thousand African migrants. About 85,000 years ago, the first wave of human migration was out of Africa, that followed the coasts through the Middle East, into Southern Asia via Sri Lanka, and in due course around Indonesia and into Australia. Another wave of migration between 40,000 and 12,000 years ago brought humans northward into Europe. However, the frozen north limited human expansion in Europe, and created a land bridge, "Bering land bridge", connecting Asia with North America about 25,000 years ago. Although fossil data give the most direct information about our past, it has certain anomalies. So, molecular archeologists are now using different molecular markers to trace the "most recent common ancestor" and also the migration pattern of modern humans. In this study, we have studied the trend of molecular markers and also the methodologies implemented in the last decades (2003-2014). From our observation, we can say that D-loop region of mtDNA and Y chromosome based markers are predominant. Nevertheless, mtDNA, especially the D-loop region, has some unique features, which makes it a more effective marker for tracing prehistoric footprints of modern human populations. Although, natural selection should also be taken into account in studying mtDNA based human migration. As per technology is concerned, Sanger sequencing is the major technique that is being used in almost all studies. But, the emergence of different cost-effective-and-easy-to-handle NGS platforms has increased its popularity over Sanger sequencing in studying human migration.

Endocasts: possibilities and limitations for the interpretation of human brain evolution

Brains are not preserved in the fossil record but endocranial casts are. These are casts of the internal bony braincase, revealing approximate brain size and shape, and they are also informative about brain surface morphology. Endocasts are the only direct evidence of human brain evolution, but they provide only limited data ('paleoneurology'). This review discusses some new fossil endocasts and recent methodological advances that have allowed novel analyses of old endocasts, leading to intriguing findings and hypotheses. The interpretation of paleoneurological data always relies on comparative information from living species whose brains and behavior can be directly investigated. It is therefore important that future studies attempt to better integrate different approaches. Only then will we be able to gain a better understanding about hominin brain evolution. © 2014 S. Karger AG, Basel.

A re-examination of the human fossil specimen from Bački Petrovac (Serbia)

A fragmented human calotte was discovered during the early 1950s near Bački Petrovac (Serbia), in association with Palaeolithic stone tools. After its initial publication, the fossil specimen remained largely unknown outside of the Serbian academe and no detailed comparative study has ever been carried out. Since the whereabouts of the fossil itself are currently unknown, and given its potential significance for the Pleistocene human evolution, we re-examine the data published by Živanović (1966, 1975). Using the original measurements, mostly taken on the frontal bone, and a wide comparative sample of 68 fossil specimens, the fossil was compared and analyzed by statistical multivariate methods. We also conducted a visual examination of the morphology based on the available photographic material. Our analysis reveals phenetic similarity with Middle Pleistocene archaic Homo from Africa and anatomically modern Homo sapiens. However, the absence of primitive cranial traits in Bački Petrovac indicates a clear modern Homo sapiens designation. Although lost at the moment, there is a chance for the re-discovery of the fossil in the years to come. This would give us an opportunity to acquire absolute dates and to study the specimen in a more detailed manner.

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.

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

The site of Dmanisi, Georgia, has yielded an impressive sample of hominid cranial and postcranial remains, documenting the presence of Homo outside Africa around 1.8 million years ago. Here we report on a new cranium from Dmanisi (D4500) that, together with its mandible (D2600), represents the world's first completely preserved adult hominid skull from the early Pleistocene. D4500/D2600 combines a small braincase (546 cubic centimeters) with a large prognathic face and exhibits close morphological affinities with the earliest known Homo fossils from Africa. The Dmanisi sample, which now comprises five crania, provides direct evidence for wide morphological variation within and among early Homo paleodemes. This implies the existence of a single evolving lineage of early Homo, with phylogeographic continuity across continents.

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

The Plio-Pleistocene hominin sample from Dmanisi (Georgia), dated to 1.77 million years ago, is unique in offering detailed insights into patterns of morphological variation within a paleodeme of early Homo. Cranial and dentoalveolar morphologies exhibit a high degree of diversity, but the causes of variation are still relatively unexplored. Here we show that wear-related dentoalveolar remodeling is one of the principal mechanisms causing mandibular shape variation in fossil Homo and in modern human hunter-gatherer populations. We identify a consistent pattern of mandibular morphological alteration, suggesting that dental wear and compensatory remodeling mechanisms remained fairly constant throughout the evolution of the genus Homo. With increasing occlusal and interproximal tooth wear, the teeth continue to erupt, the posterior dentition tends to drift in a mesial direction, and the front teeth become more upright. The resulting changes in dentognathic size and shape are substantial and need to be taken into account in comparative taxonomic analyses of isolated hominin mandibles. Our data further show that excessive tooth wear eventually leads to a breakdown of the normal remodeling mechanisms, resulting in dentognathic pathologies, tooth loss, and loss of masticatory function. Complete breakdown of dentognathic homeostasis, however, is unlikely to have limited the life span of early Homo because this effect was likely mediated by the preparation of soft foods.

Evaluating developmental shape changes in Homo antecessor subadult facial morphology

The fossil ATD6-69 from Atapuerca, Spain, dated to ca. 900 ka (thousands of years ago) has been suggested to mark the earliest appearance of modern human facial features. However, this specimen is a subadult and the interpretation of its morphology remains controversial, because it is unclear how developmental shape changes would affect the features that link ATD6-69 to modern humans. Here we analyze ATD6-69 in an evolutionary and developmental context. Our modern human sample comprises cross-sectional growth series from four populations. The fossil sample covers human specimens from the Pleistocene to the Upper Paleolithic, and includes several subadult Early Pleistocene humans and Neanderthals. We digitized landmarks and semilandmarks on surface and CT scans and analyzed the Procrustes shape coordinates using multivariate statistics. Ontogenetic allometric trajectories and developmental simulations were employed in order to identify growth patterns and to visualize potential adult shapes of ATD6-69. We show that facial differences between modern and archaic humans are not exclusively allometric. We find that while postnatal growth further accentuates the differences in facial features between Neanderthals and modern humans, those features that have been suggested to link ATD6-69's morphology to modern humans would not have been significantly altered in the course of subsequent development. In particular, the infraorbital depression on this specimen would have persisted into adulthood. However, many of the facial features that ATD6-69 shares with modern humans can be considered to be part of a generalized pattern of facial architecture. Our results present a complex picture regarding the polarity of facial features and demonstrate that some modern human-like facial morphology is intermittently present in Middle Pleistocene humans. We suggest that some of the facial features that characterize recent modern humans may have developed multiple times in human evolution.

Homo floresiensis contextualized: a geometric morphometric comparative analysis of fossil and pathological human samples

The origin of hominins found on the remote Indonesian island of Flores remains highly contentious. These specimens may represent a new hominin species, Homo floresiensis, descended from a local population of Homo erectus or from an earlier (pre-H. erectus) migration of a small-bodied and small-brained hominin out of Africa. Alternatively, some workers suggest that some or all of the specimens recovered from Liang Bua are pathological members of a small-bodied modern human population. Pathological conditions proposed to explain their documented anatomical features include microcephaly, myxoedematous endemic hypothyroidism (“cretinism”) and Laron syndrome (primary growth hormone insensitivity). This study evaluates evolutionary and pathological hypotheses through comparative analysis of cranial morphology. Geometric morphometric analyses of landmark data show that the sole Flores cranium (LB1) is clearly distinct from healthy modern humans and from those exhibiting hypothyroidism and Laron syndrome. Modern human microcephalic specimens converge, to some extent, on crania of extinct species of Homo. However in the features that distinguish these two groups, LB1 consistently groups with fossil hominins and is most similar to H. erectus. Our study provides further support for recognizing the Flores hominins as a distinct species, H. floresiensis, whose affinities lie with archaic Homo.