On the taxonomic affinities of the Dmanisi mandible (Georgia)

The recent discovery of unexpectedly ancient human remains has fuelled interest about the first dispersion of Homo outside Africa. The Dmanisi mandible is perhaps one of the most interesting findings, as it supposedly represents one of the oldest hominids outside of Africa. Recently, different interpretations have been published about this specimen. Our comparison of the Dmanisi mandible with a large sample of mandibles and teeth has led us to a new interpretation. In our view, the Dmanisi mandible exhibits a unique combination of traits. Some of its features, taken in isolation, may be attributed to morphological extremes within the genus Homo. The architecture of the mandible as well as the morphology and dimensions of incisors, canines, and P3s are clearly primitive. However, dental traits such as the reduction of the talonid in the P4s and a distally decreasing molar series seems to be derived. Some combinations of these traits are found in specimens of Homo ergaster and differ from those generally present in later hominids. Thus, we propose that the Dmanisi mandible might be taxonomically classified as Homo sp. indet. (aff. ergaster). Furthermore, some aspects of the dentition in Dmanisi display close similarities to Asian Homo erectus. If the 1.8–1.6 Myr dating for the Dmanisi mandible is correct, the differentiation of the Asian branch of the genus Homo could be regarded as a very ancient event. Am J Phys Anthropol 107:145–162, 1998. © 1998 Wiley-Liss, Inc.     

Human evolution

The common ancestor of modern humans and the great apes is estimated to have lived between 5 and 8 Myrs ago, but the earliest evidence in the human, or hominid, fossil record is Ardipithecus ramidus, from a 4.5 Myr Ethiopian site. This genus was succeeded by Australopithecus, within which four species are presently recognised. All combine a relatively primitive postcranial skeleton, a dentition with expanded chewing teeth and a small brain. The most primitive species in our own genus, Homo habilis and Homo rudolfensis, are little advanced over the australopithecines and with hindsight their inclusion in Homo may not be appropriate. The first species to share a substantial number of features with later Homo is Homo ergaster, or ‘early African Homo erectus’, which appears in the fossil record around 2.0 Myr. Outside Africa, fossil hominids appear as Homo erectus-like hominids, in mainland Asia and in Indonesia close to 2 Myr ago; the earliest good evidence of ‘archaic Homo’ in Europe is dated at between 600–700 Kyr before the present. Anatomically modern human, or Homo sapiens, fossils are seen first in the fossil record in Africa around 150 Kyr ago. Taken together with molecular evidence on the extent of DNA variation, this suggests that the transition from ‘archiac’ to ‘modern’ Homo may have taken place in Africa.     

Dental variability inSaimiri and the taxonomic status ofNeosaimiri fieldsi,an early squirrel monkey from La Venta,Colombia

Neosaimiri fieldsi, from the South American middle Miocene locality of La Venta, is represented by a relatively complete mandible and dentition that strongly resembles that of extantSaimiri. Comparison with a large sample of mandibles ofSaimiri indicates that this specimen cannot be distinguished from modern populations on the basis of any reportedly diagnostic feature, such as cingulid development, molar length ratio, trigonic/talonid ratio, or mandibular depth. The fossil is best considered an extinct species of the modern genusSaimiri until further material indicates otherwise.     

The Magdalenian child from the cave Le Figuier (Ardeche) France

The skeletal remains from the cave of the Figuier are believed now to be of Magdalenian date. They belong to a three year old child. Though the mandible and the dentition show some archaic morphological trends, the majority of the characters are not essentially different from those of modern children of the same age living now. These remains must be related to Homo sapiens sapiens.     

Revision of fossil hominid jaws from the plio/pleistocene of hadar,in ethiopia including a new species of the genusHomo (hominoidea: homininae)

The assignment of fossil hominoid jaws from the Plio/Pleistocene of Hadar to a single genus,Australopithecus Dart, 1925, is a misnomer. They are morphologically unrestricted to and inconsistent with the diagnosis and evolutionary trend ofAustralopithecus. The morphological pattern of four large jaws is indeed australopithecine and similar toA. africanus Dart, 1925, but six small jaws reveal a pre-habilis stage of dental development early in theHomo lineage. On the basis of their unique hominine dentition, they are reinterpreted as representing a new species,Homo antiquus n.sp.     

Bushman rock shelter,Origstad, Eastern Transvaal,South Africa

Absolute dating of several stratigraphic levels position an infant's mandible relatively to about 29,500 years ago. This mandible may represent the infant stage of an early Negroid from of Homo sapiens afer and was probably associated with cultural material belonging to the transition of the Middle Stone Age to the Late Stone Age.     

Longgupo: EarlyHomo colonizer or late plioceneLufengpithecus survivor in south China?

A fragment of mandible and a maxillary incisor of different individuals from the Longgupo Cave, China have been cited as evidence of an early dispersal ofHomo from Africa to Asia. More specifically, these specimens are said to resemble “Homo ergaster” orHomo habilis, rather than the species usually thought to be the first Asian colonizer,Homo erectus. If this supposition is correct, it calls into question which hominid (sensu stricto) first left Africa, and why hominids became a colonizing species. Furthermore, the Longgupo remains have been used to buttress the argument thatHomo erectus evolved uniquely in Asia and was not involved in the origins of modern humans. We question this whole line of argument because the mandibular fragment cannot be distinguished from penecontemporary fossil apes, especially the Late Miocene-Pliocene Chinese genusLufengpithecus, while the incisor is indistinguishable from those of recent and living east Asian people and may be intrusive in the deposit. We believe that the Longgupo mandible represents the relic survival of a Late Miocene ape lineage into a period just prior to the dispersal of hominids into southeastern Asia, with some female dental features that parallel the hominid condition. If the Longgupo mandibular fragment represents a member of theLufengpithecus clade, it demonstrates that hominoids other thanGigantopithecus and the direct ancestor of the orangutan persisted in east Asia into the Late Pliocene, while all other Eurasian large-bodied hominoids disappeared in the Late Miocene.     

A non‐aquatic otter (Mammalia,Carnivora, Mustelidae) from the Late Miocene (Vallesian,MN 10) of La Roma 2 (Alfambra,Teruel, Spain): systematics and functional anatomy

A new genus and species of otter‐like mustelid, Teruelictis riparius, is created on the basis of a partial skeleton from the Late Miocene (Vallesian age, MN 10) locality of La Roma 2 (Teruel, Spain), including several postcranial elements, the skull, and the mandible. The combination of a typically lutrine dentition, similar to that of other fossil otters such as Paralutra jaegeri, with a very slender postcranial skeleton, including a long back and gracile long bones and metacarpals, thus lacking any aquatic adaptations, was previously unknown in the fossil record. This mosaic of features strongly suggests the possibility that the aquatic lifestyle of otters could have appeared after the initial development of the distinctive dental morphology of this specialized group of mustelids. © 2013 The Linnean Society of London     

Dietary correlates associated with the mental foramen in primates: implications for interpreting the fossil record

The mandibular nerve is a sensory and motor nerve that innervates the muscles of mastication, the lower dentition, and the lower lip and surrounding structures. Although this nerve contains both efferent and afferent fibers, the mental nerve, a terminal branch of the mandibular nerve, is a strictly sensory nerve that exits the mental foramen and innervates the lower lip, the skin overlaying the mandible, and the oral mucosa around the mandible. Osteological foramina are often used as proxies for nerve cross section area and they often correlate well with some aspect of a primate's ecology (e.g., optic foramen and visual acuity). The primary objective of this study is to explore the correlation between the mental foramen and dietary preference among primates. The mental foramen of 40 primate species (n = 180) was measured from 3‐D surface models of the mandible. Both conventional and phylogenetic tests indicate that although frugivores have larger mental foramina than folivores, the differences were not significant. These results show that while structures like the infraorbital foramen correlate well with diet and touch sensitivity, the mental foramen does not. Based on these findings, the mental foramen is not a suggested morphological character for interpreting of the fossil record. J. Morphol. 277:978–985, 2016. © 2016 Wiley Periodicals, Inc.     

The dating of Lantian man and his significance for analyzing trends in human evolution

The Lantian fossil hominid cranium from Southern Shensi Province, China, provides the earliest record of Homo erectus in northern east Asia, and is morphologically the most primitive specimen in the entire world. Importantly, the Kungwangling Lantian cranium (calvarium plus face), with associated stone tools in good geologic and paleontological context, is demonstrably both earlier and more primitive than the Choukoutien I remains. Faunal and palynological evidence support a mid-Mosbachium equivalent age (some 700,000 years). These facts are not recognized in the original Chinese reports. The Chenchiawo Lantian mandible, like the Choukoutien I remains, is attributable to the Holstein-equivalent in China (some 300,000 years ago), and therefore should no longer be temporally associated with the Kungwangling Lantian cranium. However, that the mandible may be morphologically associated with either calls attention to the relative independence of the mandible in human evolution. A comparative study of some modern Mongoloid populations in which very large mandibles may or may not be associated with a scaphoid keel or sagittal elevation depending upon the size and shape of the cranium demonstrates the relative autonomy of the mandible. Continuing selection pressure for a masticatory complex with large jaws provides another point of continuity between East Asian fossil and modern Mongoloid hunting populations such as Eskimos and Aleuts. A number of morphological features of the cranium, especially vault thickness, cranial capacity and reinforcement system, conform to expectation and confirm a general trend of reduction in vault thickness and reinforcement system with increase in cranial capacity over time within the single human species.     

The history of the genusHomo

The genusHomo was established by Carolus Linnaeus in 1758. During the course of the past 150 years, the addition of fossil species to the genusHomo has resulted in a genus that, according to the taxonomic interpretation, could span as much time as 2.5 Myr, and include as many as ten species. This paper reviews the fossil evidence for each of the species involved, and sets out the case for their inclusion inHomo. It suggests that while the case for the inclusion of some species in the genus (e.g.Homo erectus) is well-supported, in the case of two of the species,Homo habilis andHomo rudolfensis, the case for their inclusion is much weaker. Neither the cladistic evidence, nor evidence about adaptation suggest a particularly close relationship with laterHomo.     

Skull of early Eocene Cantius abditus (primates: Adapiformes) and its phylogenetic implications,with a reevaluation of “Hesperolemur” actius

A substantially complete skull and mandible of the primitive adapiform Cantius is reported from the Early Eocene Willwood Formation of Wyoming. The mandible contains an almost complete lower dentition in which the lower incisors are strongly inclined and have spatulate crowns, I₂ is larger than I₁, and the canine is large and projecting. The cranium shares many features with those of Notharctus and Smilodectes but differs in having nasals that broaden proximally. Presence of a prominent canine and strong sagittal crest may indicate that it represents a male. The basicranium preserves auditory structures almost identical to those in extant noncheirogaleid lemurs, including a large bony tube for the stapedial artery and a small, open sulcus for the distal portion of the promontorial artery. The dentition is sufficiently primitive to be compatible with a relationship to either strepsirrhines or anthropoids, but the anatomy of the auditory region is more consistent with either specific relationship to lemurs or, more likely, a basal position that approximates the euprimate morphotype. Certain features of the basicranium of “Hesperolemur” actius, described by Gunnell ([1995] Am. J. Phys. Anthropol. 98:447–470) as being unlike that of any other adapiform, were either misinterpreted or are apparently no longer present in the holotype. Reassessment of these and other features indicates that in fact “H.” actius differs little from Cantius and should not be separated from the latter at the genus level, although on dental grounds the species appears to be distinct (as C. actius). Am J Phys Anthropol 109:523–539, 1999. © 1999 Wiley-Liss, Inc.     

Progressive changes in brain size and musculo-skeletal traits in seven hominoid populations

Neurological complexity has increased over evolutionary time for invertebrates and vertebrates alike, with the hominid brain tripling in size over the last 3 million years. Since magnetic resonance imaging (MRI) studies among humans indicate a significant correlation (meanr>0.40) between individual differences in brain size and general cognitive ability, it is reasonable to hypothesize that increasing brain size confers greater intelligence. However, larger brains have associated costs, taking longer to build and requiring more energy to run. Sufficient advantages must have accrued for them to override these trade-offs. The present paper documents that in hominoids, as brain size increased from 380 to 1364 cm³ over seven hominoid groups (chimpanzees to australopithecines toHomo habilis toHomo erectus to differences amongHomo sapiens), it was accompanied by changes in 74 musculo-skeletal traits (rs=0.90). These occurred on both cranial traits (temporalis fossae, post-orbital constrictions, mandibles, dentition, nuchal muscle attachments) and on post-cranial traits (pelvic widths, femoral heads, tibial plateaus). It is concluded that in the evolutionary competition to find and fill new niches, there was “room at the top” for greater behavioral complexity and larger brain size, leading to cascading effects on other traits.     

The plagiosaurid temnospondyl Plagiosuchus pustuliferus (Amphibia: Temnospondyli) from the Middle Triassic of Germany: anatomy and functional morphology of the skull

The cranial anatomy of the plagiosaurid temnospondyl Plagiosuchus pustuliferus, from the Middle Triassic of Germany, is described in detail on the basis of a newly discovered skull and mandibular material. The highly derived skull is characterized by huge orbitotemporal fenestrae, a reduction of the circumorbital bones – the prefrontal, postfrontal and (probably) postorbital are lost – and the expansion of the jugal to occupy most of the lateral skull margin. Ventrally the extremely long subtemporal vacuities correlate with the elongate adductor fossa of the mandible. The dentition is feebly developed on both skull and mandible. Ossified ?ceratobranchials and ‘branchial denticles’ indicate the presence of open gills clefts in life. The remarkably divergent cranial morphology of P. pustuliferus highlights the extraordinary cranial diversity within the Plagiosauridae, probably unsurpassed within the Temnospondyli. Specific structural aspects of the skull – including an extremely short marginal tooth row, feeble dentition and an elongated chamber for adductor musculature – together with evidence for a hyobranchial skeleton, suggests that P. pustuliferus utilized directed suction feeding for prey capture. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 348–373.     

Taxonomic status of the hominid mandible KNM-ER TI 13150 from the middle pliocene of tabarin,in Kenya

A partial mandible with two molars intact was recovered between 1981 and 1984 from deposits of the Middle Pliocene at Tabarin, in Kenya. It has been described and assigned toAustralopithecus cf.afarensis Johanson, White, andCoppens, 1978, with the condition that if ‘A. afarensis’ is revised, then the attribution may change. The taxon ‘A. afarensis’ was found to be invalid and was revised. The smaller specimens of ‘A. afarensis,’ to which the Tabarin mandible was said to be similar, were redescribed asHomo antiquus Ferguson, 1984. Since the Tabarin mandible andH. antiquus are successive transients of the same gens and are allopatric, the Tabarin hominid population is described as an earlier chronosubspecies,Homo antiquus praegens ssp. n.     

Homologies of the anterior teeth in indriidae

Schwartz ('74) proposed revised homologies of the deciduous and permanent anterior teeth in living lemuriform primates of the family Indriidae. Gingerich ('77) described a juvenile specimen of Avahi and emphasized the importance of functional integrity in controlling the pattern of dental reduction in primates, neither of which supports Schwartz's interpretation. Schwartz ('78) recently reiterated his position without adequately discussing the Avahi evidence and the functional basis that probably controls dental reduction. Avahi has a deciduous dentition intermediate in morphology between that of Lemuridae and Indriidae, and similar to both. Thus the lower deciduous dental formula of Indriidae is probably 2.1.3, which is the typical and maximum deciduous complement known in living and fossil lemuriform primates. The formula of the lower permanent dentition in Indriidae is thus 2.0.2.3.     

Rethinking the dispersal of Homo sapiens out of Africa

Current fossil, genetic, and archeological data indicate that Homo sapiens originated in Africa in the late Middle Pleistocene. By the end of the Late Pleistocene, our species was distributed across every continent except Antarctica, setting the foundations for the subsequent demographic and cultural changes of the Holocene. The intervening processes remain intensely debated and a key theme in hominin evolutionary studies. We review archeological, fossil, environmental, and genetic data to evaluate the current state of knowledge on the dispersal of Homo sapiens out of Africa. The emerging picture of the dispersal process suggests dynamic behavioral variability, complex interactions between populations, and an intricate genetic and cultural legacy. This evolutionary and historical complexity challenges simple narratives and suggests that hybrid models and the testing of explicit hypotheses are required to understand the expansion of Homo sapiens into Eurasia.     

Some strange properties of the logistic equation defined with r and K: Inherent defects or artifacts?

In some situations the logistic equation in the usual expression, dN/dt=r(1−N/K)N, exhibits properties that are biologically unrealistic. For example, when r≦0 the population can no longer show any normal, negative response in per-capita growth rate to increasing density. Also, when the equation is employed in the Volterra's competition model, a familiar but incredible conclusion is derived which says that the outcome of competition is entirely independent of the reproductive potential r of each species. It is shown that all such strange properties are mere artifacts arising peculiarly in this r-K model from its misleading implicit supposition that K could be independent of r, and they can be readily removed by alternative use of a plainer, classical form of the model, dN/dt=(r−hN)N.     

Les restes humains du Pliocène final et du début du Pléistocène inférieur de Dmanissi, Géorgie (1991-2000). I - Les crânes, D 2280, D 2282, D 2700

Since 1991, several human remains: 5 skulls, 4 mandibles and numerous postcranial fragments have been discovered on the Dmanissi prehistoric open site. It is an exceptional discovery due to the stratigraphical, paleontological and cultural context, which is well known and accurately well dated (Upper Pliocene-Early Pleistocene). Most of the hominids discovered in the level V and VI are dated between 1.81 My (level V) and 1.77 My (level VI) corresponding to a 40,000 years period. The assemblage of fossil human remains is peculiar due to (1) the quality of bone representation (distinct parts of the skeleton are preserved: skull, thorax, upper and lower limbs, belt), (2) the high degree of bone preservation (skulls and long bones are entire, rarely broken or crushed), (3) the diversity age at death estimated for each of the 5 individuals (3 adults, 1 young adult, 1 adolescent of both sexes). The study dealing with the first discovered mandibles and skulls has begun with Leo Gabounia since 1991 and represents several interests: 1) a paleoanthropological interest: the Dmanissi skulls are characterized by their small size; they are short, narrow and low. The skullcaps are less elevated than those of the Homo erectus group and even those of Homo ergaster. They are more elevated than those of Homo habilis and very close to Homo rudolfensis. The elevation and the transversal development of the middle part of the skull in the parietotemporal region are more significant: the Dmanissi specimens are intermediate between Homo habilis and Homo ergaster. In term of cranial capacity, a similar trend is observed. Generally speaking, the skull is slender. The vault is more flat than in Homo erectus, the frontal bone is less developed, divergent and the postorbital constriction is strong. The temporal bone is long, flat and the mastoid part is short. The upper part of the occipital bone is low and narrow. Crests are thin, less developed than in the Homo erectus group. The superior temporal crests are in a high position and a torus angularis is present on the adult-male specimen. The glenoid cavity is large with strong edges. The petrotympanic region is slender with a tympanic circle individualized and it shows a horizontal rotation in a posterior position, which is distinct from Homo erectus. The orthognathic trend of the face distinguishes the Dmanissi specimens from the early Pleistocene hominids (Homo habilis, Homo ergaster) and from the first Eurasian Homo erectus. Nevertheless, the subnasal region of the face is projected. The morphology of the mid-face, showing a developed pillar of the canine, an inframalar incurvation and an anterior position of the root of the zygomaticomaxillary crest, suggests strong masticatory stress. Considering the overall morphology, cranial and metrical features, the Dmanissi fossil skulls are intermediate to the Homo habilis-rudolfensis group and Homo ergaster while they are closer to the former and peculiarly to Homo rudolfensis (ER 1470). However, the Dmanissi fossil skulls are distinct from Homo rudolfensis by numerous features and among them: by their large maximum cranial width (Euryon-Euryon), the posterior rotation of their petrotympanic structure and the strong development of the pillar of their canine. Due to the gracility of their face, the narrowness of their occipital bone, and their cranial base pattern (mastoid region and petrotympanic structure), the Dmanissi fossil skulls are different from the Homo erectus group: 2) the abundance of the human fossils discovered in Dmanissi site provides information about the biodiversity of these hominids with the establishment of the morphological features related to either growth or sexual patterns: 3) compared to modern humans, the Dmanissi fossil skulls seem to follow a different growth pattern. The present study of the fossil skulls discovered is a pioneer step. Indeed, the Dmanissi site has yielded the oldest evidences of the first settlements in Eurasia, which were, until now, attributed to Homo erectus. The Dmanissi fossil skulls are close to the Homo habilis-rudolfensis African group. We attribute these hominids to Homo georgicus.     

The posterior border of the sphenoid greater wing and its phylogenetic usefulness in human evolution

The elucidation of patterns of cranial skeletal maturation and growth in fossil hominids is possible not only through dental studies but also by mapping different aspects of ossification in both extant African apes and humans. However, knowledge of normal skeletal development in large samples of extant great apes is flimsy. To remedy this situation, this paper offers an extensive survey and thorough discussion of the ossification of the posterior border of the sphenoid greater wing. Indeed, this area provides much information about basicranial skeletal maturation. We investigate three variants: the absence of the foramen spinosum and the position of both the foramen spinosum and the foramen ovale in relation to the sphenosquamosal suture. Providing original data about humans and 1,425 extant great ape skulls and using a sample of 64 fossil hominids, this study aimed to test whether different ossification patterns occurred during the course of human evolution. The incidence of three derived morphologies located on the posterior border of the sphenoid greater wing increases during human evolution at different geological periods. The evolutionary polarity of these three derived morphologies is assessed by outgroup comparison and ontogenetic methods. During human evolution, there is a clear trend for the foramen spinosum to be present and wholly located on the posterior area of the sphenoid greater wing. Moreover, in all the great ape species and in Australopithecus afarensis, the sphenosquamosal suture may split the foramen ovale. Inversely, the foramen ovale always lies wholly within the sphenoid greater wing in Australopithecus africanus, robust australopithecines, early Homo, H. erectus (and/or H. ergaster), and Homo sapiens. From ontogenetic studies in humans, we conclude that, during human evolution, the ossification of the posterior area of the sphenoid greater wing progressively surrounded the middle meningeal artery (passing through the foramen spinosum) and the small meningeal artery (passing through the foramen ovale). Am J Phys Anthropol 107:387–399, 1998. © 1998 Wiley-Liss, Inc.