Homo floresiensis: a cladistic analysis

The announcement of a new species, Homo floresiensis, a primitive hominin that survived until relatively recent times is an enormous challenge to paradigms of human evolution. Until this announcement, the dominant paradigm stipulated that: 1) only more derived hominins had emerged from Africa, and 2) H. sapiens was the only hominin since the demise of Homo erectus and Homo neanderthalensis. Resistance to H. floresiensis has been intense, and debate centers on two sets of competing hypotheses: 1) that it is a primitive hominin, and 2) that it is a modern human, either a pygmoid form or a pathological individual. Despite a range of analytical techniques having been applied to the question, no resolution has been reached. Here, we use cladistic analysis, a tool that has not, until now, been applied to the problem, to establish the phylogenetic position of the species. Our results produce two equally parsimonious phylogenetic trees. The first suggests that H. floresiensis is an early hominin that emerged after Homo rudolfensis (1.86 Ma) but before H. habilis (1.66 Ma, or after 1.9 Ma if the earlier chronology for H. habilis is retained). The second tree indicates H. floresiensis branched after Homo habilis.     

Liang Bua Homo floresiensis mandibles and mandibular teeth: a contribution to the comparative morphology of a new hominin species

In 2004, a new hominin species, Homo floresiensis, was described from Late Pleistocene cave deposits at Liang Bua, Flores. H. floresiensis was remarkable for its small body-size, endocranial volume in the chimpanzee range, limb proportions and skeletal robusticity similar to Pliocene Australopithecus, and a skeletal morphology with a distinctive combination of symplesiomorphic, derived, and unique traits. Critics of H. floresiensis as a novel species have argued that the Pleistocene skeletons from Liang Bua either fall within the range of living Australomelanesians, exhibit the attributes of growth disorders found in modern humans, or a combination of both. Here we describe the morphology of the LB1, LB2, and LB6 mandibles and mandibular teeth from Liang Bua. Morphological and metrical comparisons of the mandibles demonstrate that they share a distinctive suite of traits that place them outside both the H. sapiens and H. erectus ranges of variation. While having the derived molar size of later Homo, the symphyseal, corpus, ramus, and premolar morphologies share similarities with both Australopithecus and early Homo. When the mandibles are considered with the existing evidence for cranial and postcranial anatomy, limb proportions, and the functional anatomy of the wrist and shoulder, they are in many respects closer to African early Homo or Australopithecus than to later Homo. Taken together, this evidence suggests that the ancestors of H. floresiensis left Africa before the evolution of H. erectus, as defined by the Dmanisi and East African evidence.     

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.     

A geometric morphometric analysis of hominin upper second and third molars, with particular emphasis on European Pleistocene populations

The study of dental morphology by means of geometric morphometric methods allows for a detailed and quantitative comparison of hominin species that is useful for taxonomic assignment and phylogenetic reconstruction. Upper second and third molars have been studied in a comprehensive sample of Plio- and Pleistocene hominins from African, Asian and European sites in order to complete our analysis of the upper postcanine dentition. Intraspecific variation in these two molars is high, but some interspecific trends can be identified. Both molars exhibit a strong reduction of the distal cusps in recent hominin species, namely European Homo heidelbergensis, Homo neanderthalensis and Homo sapiens, but this reduction shows specific patterns and proportions in the three groups. Second molars tend to show four well developed cusps in earlier hominin species and their morphology is only marginally affected by allometric effects. Third molars can be incipiently reduced in earlier species and they evince a significant allometric component, identified both inter- and intraspecifically. European Middle Pleistocene fossils from Sima de los Huesos (SH) show a very strong reduction of these two molars, even more marked than the reduction observed in Neanderthals and in modern human populations. The highly derived shape of SH molars points to an early acquisition of typical Neanderthal dental traits by pre-Neanderthal populations and to a deviation of this population from mean morphologies of other European Middle Pleistocene groups.     

Conclusions: implications of the Liang Bua excavations for hominin evolution and biogeography

Excavations at Liang Bua, on the Indonesian island of Flores, have yielded a stratified sequence of stone artifacts and faunal remains spanning the last 95 k.yr., which includes the skeletal remains of two human species, Homo sapiens in the Holocene and Homo floresiensis in the Pleistocene. This paper summarizes and focuses on some of the evidence for Homo floresiensis in context, as presented in this Special Issue edition of the Journal of Human Evolution and elsewhere. Attempts to dismiss the Pleistocene hominins (and the type specimen LB1 in particular) as pathological pygmy humans are not compatible with detailed analyses of the skull, teeth, brain endocast, and postcranium. We initially concluded that H. floresiensis may have evolved by insular dwarfing of a larger-bodied hominin species over 880 k.yr. or more. However, recovery of additional specimens and the numerous primitive morphological traits seen throughout the skeleton suggest instead that it is more likely to be a late representative of a small-bodied lineage that exited Africa before the emergence of Homo erectus sensu lato. Homo floresiensis is clearly not an australopithecine, but does retain many aspects of anatomy (and perhaps behavior) that are probably plesiomorphic for the genus Homo. We also discuss some of the other implications of this tiny, endemic species for early hominin dispersal and evolution (e.g., for the “Out of Africa 1” paradigm and more specifically for colonizing Southeast Asia), and we present options for future research in the region.     

Hominin teeth from the early Late Pleistocene site of Xujiayao,Northern China

It is generally accepted that from the late Middle to the early Late Pleistocene (～340–90 ka BP), Neanderthals were occupying Europe and Western Asia, whereas anatomically modern humans were present in the African continent. In contrast, the paucity of hominin fossil evidence from East Asia from this period impedes a complete evolutionary picture of the genus Homo, as well as assessment of the possible contribution of or interaction with Asian hominins in the evolution of Homo sapiens and Homo neanderthalensis. Here we present a comparative study of a hominin dental sample recovered from the Xujiayao site, in Northern China, attributed to the early Late Pleistocene (MIS 5 to 4). Our dental study reveals a mosaic of primitive and derived dental features for the Xujiayao hominins that can be summarized as follows: i) they are different from archaic and recent modern humans, ii) they present some features that are common but not exclusive to the Neanderthal lineage, and iii) they retain some primitive conformations classically found in East Asian Early and Middle Pleistocene hominins despite their young geological age. Thus, our study evinces the existence in China of a population of unclear taxonomic status with regard to other contemporary populations such as H. sapiens and H. neanderthalensis. The morphological and metric studies of the Xujiayao teeth expand the variability known for early Late Pleistocene hominin fossils and suggest the possibility that a primitive hominin lineage may have survived late into the Late Pleistocene in China. Am J Phys Anthropol 156:224–240, 2015. © 2014 Wiley Periodicals, Inc.     

LB1 and LB6 Homo floresiensis are not modern human (Homo sapiens) cretins

Excavations in the late Pleistocene deposits at Liang Bua cave, Flores, have uncovered the skeletal remains of several small-bodied and small-brained hominins in association with stone artefacts and the bones of Stegodon. Due to their combination of plesiomorphic, unique and derived traits, they were ascribed to a new species, Homo floresiensis, which, along with Stegodon, appears to have become extinct ∼17 ka (thousand years ago). However, recently it has been argued that several characteristics of H. floresiensis were consistent with dwarfism and evidence of delayed development in modern human (Homo sapiens) myxoedematous endemic (ME) cretins. This research compares the skeletal and dental morphology in H. floresiensis with the clinical and osteological indicators of cretinism, and the traits that have been argued to be associated with ME cretinism in LB1 and LB6. Contrary to published claims, morphological and statistical comparisons did not identify the distinctive skeletal and dental indicators of cretinism in LB1 or LB6 H. floresiensis. Brain mass, skeletal proportions, epiphyseal union, orofacial morphology, dental development, size of the pituitary fossa and development of the paranasal sinuses, vault bone thickness and dimensions of the hands and feet all distinguish H. floresiensis from modern humans with ME cretinism. The research team responsible for the diagnosis of ME cretinism had not examined the original H. floresiensis skeletal materials, and perhaps, as a result, their research confused taphonomic damage with evidence of disease, and thus contained critical errors of fact and interpretation. Behavioural scenarios attempting to explain the presence of cretinous H. sapiens in the Liang Bua Pleistocene deposits, but not unaffected H. sapiens, are both unnecessary and not supported by the available archaeological and geochronological evidence from Flores.     

The hominins of Flores: Insular adaptations of the lower body

The fossil remains of Homo floresiensis have been debated extensively over the past few years. This paper will give a brief summary of the current debate, which can be summed up in three main competing explanations for the morphology of the type specimen: pathology, descendent of an early australopith-like hominin, or insular descendent of H. erectus. This paper will make a case for island dwarfing being the most plausible scenario, with H. erectus as the mainland ancestor. Additionally, the morphology of the pelvis and lower limbs are compared to other insular vertebrates and interpreted in terms of function and adaptation to the island environment of Flores.     

Receiving an Ancestor in the Phylogenetic Tree

A comparison is made between the scientific receptions of three proposed new members of the hominin phylogenetic tree: the first finds of Neanderthal Man, those of Homo erectus, and those of Homo floresiensis. In each case, the leading scientists of the moment of discovery heavily debated the finds and neglected the meaning of those finds. At least it took/will take one generation before the meaning of those finds were/will be accepted.     

Middle pleistocene humans from africa

Patterns of human evolution in the Middle Pleistocene remain poorly understood. There is general consensus that by the onset of this time period, populations ofHomo erectus were dispersed from Africa into Eurasia, including the Far East. In the western part of this range (perhaps in Africa),Homo erectus then produced a daughter lineage exhibiting more advanced characters of the face, braincase and cranial base. How this new species should be defined is currently debated. In my view, fossils from sites such as Bodo and Broken Hill in Africa may be lumped with material from earlier Middle Pleistocene localities in Europe. Such a taxon is appropriately namedHomo heidelbergensis. Whether the hypodigm should be extended to include fossils from China is another question. In any case, this group of hominids is plausibly ancestral to both the specialized Neanderthals of Europe and more modern humans of the later Middle Pleistocene.     

Mass spectrometric U-series dating of Huanglong Cave in Hubei Province,central China: Evidence for early presence of modern humans in eastern Asia

Most researchers believe that anatomically modern humans (AMH) first appeared in Africa 160-190 ka ago, and would not have reached eastern Asia until ∼50 ka ago. However, the credibility of these scenarios might have been compromised by a largely inaccurate and compressed chronological framework previously established for hominin fossils found in China. Recently there has been a growing body of evidence indicating the possible presence of AMH in eastern Asia ca. 100 ka ago or even earlier. Here we report high-precision mass spectrometric U-series dating of intercalated flowstone samples from Huanglong Cave, a recently discovered Late Pleistocene hominin site in northern Hubei Province, central China. Systematic excavations there have led to the in situ discovery of seven hominin teeth and dozens of stone and bone artifacts. The U-series dates on localized thin flowstone formations bracket the hominin specimens between 81 and 101 ka, currently the most narrow time span for all AMH beyond 45 ka in China, if the assignment of the hominin teeth to modern Homo sapiens holds. Alternatively this study provides further evidence for the early presence of an AMH morphology in China, through either independent evolution of local archaic populations or their assimilation with incoming AMH. Along with recent dating results for hominin samples from Homo erectus to AMH, a new extended and continuous timeline for Chinese hominin fossils is taking shape, which warrants a reconstruction of human evolution, especially the origins of modern humans in eastern Asia.     

Body size and body shape in early hominins - implications of the Gona Pelvis

Discovery of the first complete Early Pleistocene hominin pelvis, Gona BSN49/P27, attributed to Homo erectus, raises a number of issues regarding early hominin body size and shape variation. Here, acetabular breadth, femoral head breadth, and body mass calculated from femoral head breadth are compared in 37 early hominin (6.0-0.26 Ma) specimens, including BSN49/P27. Acetabular and estimated femoral head sizes in the Gona specimen fall close to the means for non-Homo specimens (Orrorin tugenesis, Australopithecus africanus, Paranthropus robustus), and well below the ranges of all previously described Early and Middle Pleistocene Homo specimens. The Gona specimen has an estimated body mass of 33.2 kg, close to the mean for the non-Homo sample (34.1 kg, range 24-51.5 kg, n = 19) and far outside the range for any previously known Homo specimen (mean = 70.5 kg; range 52-82 kg, n = 17). Inclusion of the Gona specimen within H. erectus increases inferred sexual dimorphism in body mass in this taxon to a level greater than that observed here for any other hominin taxon, and increases variation in body mass within H. erectus females to a level much greater than that observed for any living primate species. This raises questions regarding the taxonomic attribution of the Gona specimen. When considered within the context of overall variation in body breadth among early hominins, the mediolaterally very wide Gona pelvis fits within the distribution of other lower latitude Early and Middle Pleistocene specimens, and below that of higher latitude specimens. Thus, ecogeographic variation in body breadth was present among earlier hominins as it is in living humans. The increased M-L pelvic breadth in all earlier hominins relative to modern humans is related to an increase in ellipticity of the birth canal, possibly as a result of a non-rotational birth mechanism that was common to both australopithecines and archaic Homo.     

New evidence for a 67,000-year-old human presence at Callao Cave, Luzon, Philippines

Documentation of early human migrations through Island Southeast Asia and Wallacea en route to Australia has always been problematic due to a lack of well-dated human skeletal remains. The best known modern humans are from Niah Cave in Borneo (40-42 ka), and from Tabon Cave on the island of Palawan, southwest Philippines (47 ± 11 ka). The discovery of Homo floresiensis on the island of Flores in eastern Indonesia has also highlighted the possibilities of identifying new hominin species on islands in the region. Here, we report the discovery of a human third metatarsal from Callao Cave in northern Luzon. Direct dating of the specimen using U-series ablation has provided a minimum age estimate of 66.7 ± 1 ka, making it the oldest known human fossil in the Philippines. Its morphological features, as well as size and shape characteristics, indicate that the Callao metatarsal definitely belongs to the genus Homo. Morphometric analysis of the Callao metatarsal indicates that it has a gracile structure, close to that observed in other small-bodied Homo sapiens. Interestingly, the Callao metatarsal also falls within the morphological and size ranges of Homo habilis and H. floresiensis. Identifying whether the metatarsal represents the earliest record of H. sapiens so far recorded anywhere east of Wallace’s Line requires further archaeological research, but its presence on the isolated island of Luzon over 65,000 years ago further demonstrates the abilities of humans to make open ocean crossings in the Late Pleistocene.     

Reconstructing cranial evolution in an extinct hominin

Homo erectus is the first hominin species with a truly cosmopolitan distribution and resembles recent humans in its broad spatial distribution. The microevolutionary events associated with dispersal and local adaptation may have produced similar population structure in both species. Understanding the evolutionary population dynamics of H. erectus has larger implications for the emergence of later Homo lineages in the Middle Pleistocene. Quantitative genetics models provide a means of interrogating aspects of long-standing H. erectus population history narratives. For the current study, cranial fossils were sorted into six major palaeodemes from sites across Africa and Asia spanning 1.8–0.1 Ma. Three-dimensional shape data from the occipital and frontal bones were used to compare intraspecific variation and test evolutionary hypotheses. Results indicate that H. erectus had higher individual and group variation than Homo sapiens, probably reflecting different levels of genetic diversity and population history in these spatially disperse species. This study also revealed distinct evolutionary histories for frontal and occipital bone shape in H. erectus, with a larger role for natural selection in the former. One scenario consistent with these findings is climate-driven facial adaptation in H. erectus, which is reflected in the frontal bone through integration with the orbits.     

The Atapuerca sites and their contribution to the knowledge of human evolution in Europe

Over the last two decades, the Pleistocene sites of the Sierra de Atapuerca (Spain) have provided two extraordinary assemblages of hominin fossils that have helped refine the evolutionary story of the genus Homo in Europe. The TD6 level of the Gran Dolina site has yielded about one hundred remains belonging to a minimum of six individuals of the species Homo antecessor. These fossils, dated to the end of the Lower Pleistocene (800 kyr), provide the earliest evidence of hominin presence in Western Europe. The origin of these hominins is unknown, but they may represent a speciation event from Homo ergaster/Homo erectus. The TD6 fossils are characterized by a significant increase in cranial capacity as well as the appearance of a “sapiens” pattern of craniofacial architecture. At the Sima de los Huesos site, more than 4,000 human fossils belonging to a minimum of 28 individuals of a Middle Pleistocene population (ca. 500–400 kyr) have been recovered. These hominins document some of the oldest evidence of the European roots of Neanderthals deep in the Middle Pleistocene. Their origin would be the dispersal out of Africa of a hominin group carrying Mode 2 technologies to Europe. Comparative study of the TD6 and Sima de la Huesos hominins suggests a replacement model for the European Lower Pleistocene population of Europe or interbreeding between this population and the new African emigrants.     

Nacurrie 1: Mark of ancient Java, or a caring mother’s hands, in terminal Pleistocene Australia?

There has been a protracted debate over the evidence for intentional cranial modification in the terminal Pleistocene Australian crania from Kow Swamp and Coobool Creek. Resolution of this debate is crucial to interpretations of the significance of morphological variation within terminal Pleistocene-early Holocene Australian skeletal materials and claims of a regional evolutionary sequence linking Javan Homo erectus and Australian Homo sapiens. However, morphological comparisons of terminal Pleistocene and recent Australian crania are complicated by the significantly greater average body mass in the former. Raw and size-adjusted metric comparisons of the terminal Pleistocene skeleton from Nacurrie, south-eastern Australia, with modified and unmodified H. sapiens and H. erectus, identified a suite of traits in the frontal, parietal, and occipital bones associated with intentional modification of a neonate’s skull. These traits are also present in some of the crania from Kow Swamp and Coobool Creek, which are in close geographic proximity to Nacurrie, but not in unmodified H. sapiens or Javan H. erectus. Frontal bone morphology in H. erectus was distinct from all of the Australian H. sapiens samples. During the first six months of life, Nacurrie’s vault may have been shaped by his mother’s hands, rather than though the application of fixed bandages. Whether this behaviour persisted only for several generations, or hundreds of years, remains unknown. The reasons behind the shaping of Nacurrie’s head, aesthetics or otherwise, and why this cultural practice was adopted and subsequently discontinued, will always remain a matter of speculation.