This paper describes in detail the external morphology of LB1/1, the nearly complete and only known cranium of 'Homo floresiensis'. Comparisons were made with a large sample of early groups of the genus 'Homo' to assess primitive, derived, and unique craniofacial traits of LB1 and discuss its evolution. Principal cranial shape differences between 'H. floresiensis' and 'Homo sapiens' are also explored metrically. The LB1 specimen exhibits a marked reductive trend in its facial skeleton, which is comparable to the 'H. sapiens' condition and is probably associated with reduced masticatory stresses. However, LB1 is craniometrically different from 'H. sapiens' showing an extremely small overall cranial size, and the combination of a primitive low and anteriorly narrow vault shape, a relatively prognathic face, a rounded oval foramen that is greatly separated anteriorly from the carotid canal/jugular foramen, and a unique, tall orbital shape. Whereas the neurocranium of LB1 is as small as that of some 'Homo habilis' specimens, it exhibits laterally expanded parietals, a weak suprameatal crest, a moderately flexed occipital, a marked facial reduction, and many other derived features that characterize post-'habilis Homo'. Other craniofacial characteristics of LB1 include, for example, a relatively narrow frontal squama with flattened right and left sides, a marked frontal keel, posteriorly divergent temporal lines, a posteriorly flexed anteromedial corner of the mandibular fossa, a bulbous lateral end of the supraorbital torus, and a forward protruding maxillary body with a distinct infraorbital sulcus. LB1 is most similar to early Javanese 'Homo erectus' from Sangiran and Trinil in these and other aspects. We conclude that the craniofacial morphology of LB1 is consistent with the hypothesis that 'H. floresiensis' evolved from early Javanese 'H. erectu's with dramatic island dwarfism. However, further field discoveries of early hominin skeletal remains from Flores and detailed analyses of the finds are needed to understand the evolutionary history of this endemic hominin species.

Earlier observations of the virtual endocast of LB1, the type specimen for 'Homo floresiensis', are reviewed, extended, and interpreted. Seven derived features of LB1's cerebral cortex are detailed: a caudallypositioned occipital lobe, lack of a rostrally-located lunate sulcus, a caudally-expanded temporal lobe, advanced morphology of the lateral prefrontal cortex, shape of the rostral prefrontal cortex, enlarged gyri in the frontopolar region, and an expanded orbitofrontal cortex. These features indicate that LB1's brain was globally reorganized despite its ape-sized cranial capacity (417 cm³). Neurological reorganization may thus form the basis for the cognitive abilities attributed to 'H. floresiensis'. Because of its tiny cranial capacity, some workers think that LB1 represents a 'Homo sapiens' individual that was afflicted with microcephaly, or some other pathology, rather than a new species of hominin. We respond to concerns about our earlier study of microcephalics compared with normal individuals, and reaffirm that LB1 did not suffer from this pathology. The intense controversy about LB1 reflects an older continuing dispute about the relative evolutionary importance of brain size versus neurological reorganization. LB1 may help resolve this debate and illuminate constraints that governed hominin brain evolution.

The carpals from the 'Homo floresiensis' type specimen (LB1) lack features that compose the shared, derived complex of the radial side of the wrist in Neandertals and modern humans. This paper comprises a description and three-dimensional morphometric analysis of new carpals from at least one other individual at Liang Bua attributed to 'H. floresiensis': a right capitate and two hamates. The new capitate is smaller than that of LB1 but is nearly identical in morphology. As with capitates from extant apes, species of 'Australopithecus', and LB1, the newly described capitate displays a deeply-excavated nonarticular area along its radial aspect, a scaphoid facet that extends into a J-hook articulation on the neck, and a more radially-oriented second metacarpal facet; it also lacks an enlarged palmarly-positioned trapezoid facet. Because there is no accommodation for the derived, palmarly blocky trapezoid that characterizes 'Homo sapiens' and Neandertals, this individual most likely had a plesiomorphically wedge-shaped trapezoid (like LB1). Morphometric analyses confirm the close similarity of the new capitate and that of LB1, and are consistent with previous findings of an overall primitive articular geometry. In general, hamate morphology is more conserved across hominins, and the 'H. floresiensis' specimens fall at the far edge of the range of variation for 'H. sapiens' in a number of metrics. However, the hamate of 'H. floresiensis' is exceptionally small and exhibits a relatively long, stout hamulus lacking the oval-shaped cross-section characteristic of human and Neandertal hamuli (variably present in australopiths). Documentation of a second individual with primitive carpal anatomy from Liang Bua, along with further analysis of trapezoid scaling relative to the capitate in LB1, refutes claims that the wrist of the type specimen represents a modern human with pathology. In total, the carpal anatomy of 'H. floresiensis' supports the hypothesis that the lineage leading to the evolution of this species originated prior to the cladogenetic event that gave rise to modern humans and Neandertals.

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'.

Excavations at Liang Bua, Flores, Indonesia, have yielded evidence for an endemic human species, 'Homo floresiensis', a population that occupied the cave between ~95-17 ka. This discovery has major implications for early hominin evolution and dispersal in Africa and Asia, attracting worldwide interest. This preface describes the rationale for the excavations in historical, geographical, and wider research contexts, as well as the methods used. It also introduces the other papers on aspects of Liang Bua research that feature in this edition of the 'Journal of Human Evolution'.