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.     

Where are inion and endinion? Variations of the exo- and endocranial morphology of the occipital bone during hominin evolution

The occipital bone is frequently investigated in paleoanthropological studies because it has several features that help to differentiate various fossil hominin species. Among these features is the separation between inion and endinion, which has been proposed to be an autapomorphic trait in (Asian) Homo erectus. Methodologies are developed here to quantify for the first time the location of these anatomical points, and to interpret their variation due to the complex interactions between exocranial and endocranial size and shape of the occipital and nuchal planes, as well as the occipital lobes and cerebellum. On the basis of our analysis, neither ‘the separation between inion and endinion’ nor ‘endinion below inion’ can be considered as an autapomorphic trait in H. erectus, since this feature is a condition shared by extant African great apes and fossil hominins. Moreover, our results show that the exo- and endocranial anatomy of the occipital bone differs between hominins (except Paranthropus boisei specimens and KNM-ER 1805) and great apes. For example, chimpanzees and bonobos are characterized by a very high position of inion and their occipital bone shows an antero-posterior compression. However, these features are partly correlated with their small size when compared with hominins. Asian H. erectus specimens have a thick occipital torus, but do not differ from other robust specimens, neither in this feature nor in the analysed exo- and endocranial proportions of the occipital bone. Finally, the apparent brain size reduction during the Late Pleistocene and variation between the sexes in anatomically modern humans (AMH) reflect that specimens with smaller brains have a relatively larger posterior height of the cerebellum. However, this trend is not the sole explanation for the ‘vertical shift’ of endinion above inion that appears occasionally and exclusively in AMH.     

Dental microwear texture analysis and diet in the Dmanisi hominins

Reconstructions of foraging behavior and diet are central to our understanding of fossil hominin ecology and evolution. Current hypotheses for the evolution of the genus Homo invoke a change in foraging behavior to include higher quality foods. Recent microwear texture analyses of fossil hominin teeth have suggested that the evolution of Homo erectus may have been marked by a transition to a more variable diet. In this study, we used microwear texture analysis to examine the occlusal surface of 2 molars from Dmanisi, a 1.8 million year old fossil hominin site in the Republic of Georgia. The Dmanisi molars were characterized by a moderate degree of surface complexity (Asfc), low textural fill volume (Tfv), and a relatively low scale of maximum complexity (Smc), similar to specimens of early African H. erectus. While caution must be used in drawing conclusions from this small sample (n = 2), these results are consistent with continuity in diet as H. erectus expanded into Eurasia.     

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.     

Stature estimation from complete long bones in the Middle Pleistocene humans from the Sima de los Huesos, Sierra de Atapuerca (Spain)

Systematic excavations at the site of the Sima de los Huesos (SH) in the Sierra de Atapuerca (Burgos, Spain) have allowed us to reconstruct 27 complete long bones of the human species Homo heidelbergensis. The SH sample is used here, together with a sample of 39 complete Homo neanderthalensis long bones and 17 complete early Homo sapiens (Skhul/Qafzeh) long bones, to compare the stature of these three different human species. Stature is estimated for each bone using race- and sex-independent regression formulae, yielding an average stature for each bone within each taxon. The mean length of each long bone from SH is significantly greater (p < 0.05) than the corresponding mean values in the Neandertal sample. The stature has been calculated for male and female specimens separately, averaging both means to calculate a general mean. This general mean stature for the entire sample of long bones is 163.6 cm for the SH hominins, 160.6 cm for Neandertals and 177.4 cm for early modern humans. Despite some overlap in the ranges of variation, all mean values in the SH sample (whether considering isolated bones, the upper or lower limb, males or females or more complete individuals) are larger than those of Neandertals. Given the strong relationship between long bone length and stature, we conclude that SH hominins represent a slightly taller population or species than the Neandertals. However, compared with living European Mediterranean populations, neither the Sima de los Huesos hominins nor the Neandertals should be considered ‘short’ people. In fact, the average stature within the genus Homo seems to have changed little over the course of the last two million years, since the appearance of Homo ergaster in East Africa. It is only with the emergence of H. sapiens, whose earliest representatives were ‘very tall’, that a significant increase in stature can be documented.     

New 1.5 million-year-old Homo erectus maxilla from Sangiran (Central Java, Indonesia)

Sangiran (Solo Basin, Central Java, Indonesia) is the singular Homo erectus fossil locale for Early Pleistocene Southeast Asia. Sangiran is the source for more than 80 specimens in deposits with ⁴⁰Ar/³⁹Ar ages of 1.51-0.9 Ma. In April 2001, we recovered a H. erectus left maxilla fragment (preserving P³- M²) from the Sangiran site of Bapang. The find spot lies at the base of the Bapang Formation type section in cemented gravelly sands traditionally called the Grenzbank Zone. Two meters above the find spot, pumice hornblende has produced an ⁴⁰Ar/³⁹Ar age of 1.51 ± 0.08 Ma. With the addition of Bpg 2001.04, Sangiran now has five H. erectus maxillae. We compare the new maxilla with homologs representing Sangiran H. erectus, Zhoukoudian H. erectus, Western H. erectus (pooled African and Georgian specimens), and Homo habilis. Greatest contrast is with the Zhoukoudian maxillae, which appear to exhibit a derived pattern of premolar-molar relationships compared to Western and Sangiran H. erectus. The dental patterns suggest distinct demic origins for the earlier H. erectus populations represented at Sangiran and the later population represented at Zhoukoudian. These two east Asian populations, separated by 5000 km and nearly 800 k.yr., may have had separate origins from different African/west Eurasian populations.     

A SINGLE LINEAGE IN EARLY PLEISTOCENE HOMO: SIZE VARIATION CONTINUITY IN EARLY PLEISTOCENE HOMO CRANIA FROM EAST AFRICA AND GEORGIA

The relationship between Homo habilis and early African Homo erectus has been contentious because H. habilis was hypothesized to be an evolutionary stage between Australopithecus and H. erectus, more than a half‐century ago. Recent work re‐dating key African early Homo localities and the discovery of new fossils in East Africa and Georgia provide the opportunity for a productive re‐evaluation of this topic. Here, we test the hypothesis that the cranial sample from East Africa and Georgia represents a single evolutionary lineage of Homo spanning the approximately 1.9–1.5 Mya time period, consisting of specimens attributed to H. habilis and H. erectus. To address issues of small sample sizes in each time period, and uneven representation of cranial data, we developed a novel nonparametric randomization technique based on the variance in an index of pairwise difference from a broad set of fossil comparisons. We fail to reject the hypothesis of a single lineage this period by identifying a strong, time‐dependent pattern of variation throughout the sequence. These results suggest the need for a reappraisal of fossil evidence from other regions within this time period and highlight the critical nature of the Plio‐Pleistocene boundary for understanding the early evolution of the genus Homo.     

Dental microwear and diets of African early Homo

Conventional wisdom ties the origin and early evolution of the genus Homo to environmental changes that occurred near the end of the Pliocene. The basic idea is that changing habitats led to new diets emphasizing savanna resources, such as herd mammals or underground storage organs. Fossil teeth provide the most direct evidence available for evaluating this theory. In this paper, we present a comprehensive study of dental microwear in Plio-Pleistocene Homo from Africa. We examined all available cheek teeth from Ethiopia, Kenya, Tanzania, Malawi, and South Africa and found 18 that preserved antemortem microwear. Microwear features were measured and compared for these specimens and a baseline series of five extant primate species (Cebus apella, Gorilla gorilla, Lophocebus albigena, Pan troglodytes, and Papio ursinus) and two protohistoric human foraging groups (Aleut and Arikara) with documented differences in diet and subsistence strategies. Results confirmed that dental microwear reflects diet, such that hard-object specialists tend to have more large microwear pits, whereas tough food eaters usually have more striations and smaller microwear features. Early Homo specimens clustered with baseline groups that do not prefer fracture resistant foods. Still, Homo erectus and individuals from Swartkrans Member 1 had more small pits than Homo habilis and specimens from Sterkfontein Member 5C. These results suggest that none of the early Homo groups specialized on very hard or tough foods, but that H. erectus and Swartkrans Member 1 individuals ate, at least occasionally, more brittle or tough items than other fossil hominins studied.     

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.     

Molar microwear textures and the diets of Australopithecus anamensis and Australopithecus afarensis

Many researchers have suggested that Australopithecus anamensis and Australopithecus afarensis were among the earliest hominins to have diets that included hard, brittle items. Here we examine dental microwear textures of these hominins for evidence of this. The molars of three Au. anamensis and 19 Au. afarensis specimens examined preserve unobscured antemortem microwear. Microwear textures of these individuals closely resemble those of Paranthropus boisei, having lower complexity values than Australopithecus africanus and especially Paranthropus robustus. The microwear texture complexity values for Au. anamensis and Au. afarensis are similar to those of the grass-eating Theropithecus gelada and folivorous Alouatta palliata and Trachypithecus cristatus. This implies that these Au. anamensis and Au. afarensis individuals did not have diets dominated by hard, brittle foods shortly before their deaths. On the other hand, microwear texture anisotropy values for these taxa are lower on average than those of Theropithecus, Alouatta or Trachypithecus. This suggests that the fossil taxa did not have diets dominated by tough foods either, or if they did that directions of tooth–tooth movement were less constrained than in higher cusped and sharper crested extant primate grass eaters and folivores.     

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.     

How big were early hominids?

The recent discovery of new postcranial fossils, particularly associated body parts, of several Plio-Pleistocene hominids provides a new opportunity to assess body size in human evolution.¹ Body size plays a central role in the biology of animals because of its relationship to brain size, feeding behavior, habitat preference, social behavior, and much more. Unfortunately, the prediction of body weight from fossils is inherently inaccurate because skeletal size does not reflect body size exactly and because the fossils are from species having body proportions for which there are no analogues among modern species. The approach here is to find the relationship between body size and skeletal size in ape and human specimens of known body weight at death and to apply this knowledge to the hominid fossils, using a variety of statistical methods, knowledge of the associated partial skeletons of the of early hominids, formulae derived from a modern human sample, and, finally, common sense. The following modal weights for males and females emerge: Australopithecus afarensis, 45 and 29 kg; A. africanus, 41 and 30 kg; A. robustus, 40 and 32 kg; A. boisei, 49 and 34 kg; H. habilis, 52 and 32 kg. The best known African early H. erectus were much larger with weights ranging from 55 kg on up. These estimates imply that (1) in the earliest hominid species and the “robust” australopithecines body sizes remained small relative to modern standards, but between 2.0 and 1.7 m.y.a. there was a rapid increase to essentially modern body size with the appearance of Homo erectus; (2) the earliest species had a degree of body size sexual dimorphism well above that seen in modern humans but below that seen in modern gorillas and orangs which implies (along with other evidence) a social organization characterized by kin-related, multi-male groups with females who were not kin-related; (3) relative brain sizes increased through time; (4) there were two divergent trends in relative cheek-tooth size—a steady increase through time from A. afarensis to A. africanus to the “robust” australopithecines, and a decrease beginning with H. habilis to H. erectus to H. sapiens.     

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.     

L’architecture de l’épaule au sein du genre Homo : nouvelles interprétations

The morphology of human clavicles can be estimated by projecting them on two perpendicular planes in order to assess the shapes of their cranial and dorsal primary curvatures. In cranial view no differences in curvature appear within the genus Homo, which means the different species had similar arms elevation capacity, especially in protraction. On the contrary, in dorsal view two clavicles morphologies could be defined. The first one is characterized by two curvatures in dorsal view and is possessed by all Homo species, from Homo habilis to Neanderthal, including Homo ergaster, but not modern human, Upper Paleolithic and anatomically modern human remains, who possess clavicles of the second type, characterized by either one curvature, or two slightly pronounced ones in dorsal view. Clavicles displaying two pronounced curvatures in dorsal view are associated with scapula sitting high on the thorax in regard to modern human. However, shoulder with high scapula on the thorax displays two different kinds of architectures: (i) shoulder with short clavicles associated to scapulas sitting more laterally than those of modern human. This group includes earlier Homo like Homo habilis and Homo ergaster and (ii) shoulder with long clavicles associated to scapulas sitting more dorsally on the thorax, like those of modern human. This group includes Homoantecessor and Neanderthals. In other words, within the genus Homo, three shoulders would have existed. Evolution of the shoulder complex is far more complex than previously thought and the arrival of modern bipedalism was not associated to modern shoulder.     

Just how strapping was KNM-WT 15000?

For over twenty years, the young, male Homo erectus specimen KNM-WT 15000 has been the focus of studies on growth and development, locomotion, size, sexual dimorphism, skeletal morphology, and encephalization, often serving as the standard for his species. Prior research on KNM-WT 15000 operates under the assumption that H. erectus experienced a modern human life history, including an adolescent growth spurt. However, recent fossil discoveries, improvements in research methods, and new insights into modern human ontogeny suggest that this may not have been the case. In this study, we examine alternative life history trajectories in H. erectus to re-evaluate adult stature estimates for KNM-WT 15000. We constructed a series of hypothetical growth curves by modifying known human and chimpanzee curves, calculating intermediate growth velocities, and shifting the age of onset and completion of growth in stature. We recalculated adult stature for KNM-WT 15000 by increasing stature at death by the percentage of growth remaining in each curve. The curve that most closely matches the life history events experienced by KNM-WT 15000 prior to death indicates that growth in this specimen would have been completed by 12.3 years of age. These results suggest that KNM-WT 15000 would have experienced a growth spurt that had a lower peak velocity and shorter duration than the adolescent growth spurt in modern humans. As a result, it is likely that KNM-WT 15000 would have only attained an adult stature of 163 cm (∼5′4″), not 185 cm (∼6′1″) as previously reported. KNM-WT 15000's smaller stature has important implications for evolutionary scenarios involving early genus Homo.     

The endocast from Dana Aoule North (DAN5/P1): A 1.5 million year-old human braincase from Gona,Afar, Ethiopia

The nearly complete cranium DAN5/P1 was found at Gona (Afar, Ethiopia), dated to 1.5–1.6 Ma, and assigned to the species Homo erectus. Its size is, nonetheless, particularly small for the known range of variation of this taxon, and the cranial capacity has been estimated as 598 cc. In this study, we analyzed a reconstruction of its endocranial cast, to investigate its paleoneurological features. The main anatomical traits of the endocast were described, and its morphology was compared with other fossil and modern human samples. The endocast shows most of the traits associated with less encephalized human taxa, like narrow frontal lobes and a simple meningeal vascular network with posterior parietal branches. The parietal region is relatively tall and rounded, although not especially large. Based on our set of measures, the general endocranial proportions are within the range of fossils included in the species Homo habilis or in the genus Australopithecus. Similarities with the genus Homo include a more posterior position of the frontal lobe relative to the cranial bones, and the general endocranial length and width when size is taken into account. This new specimen extends the known brain size variability of Homo ergaster/erectus, while suggesting that differences in gross brain proportions among early human species, or even between early humans and australopiths, were absent or subtle.     

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.     

Brain size at birth throughout human evolution: a new method for estimating neonatal brain size in hominins

An increase in brain size is a hallmark of human evolution. Questions regarding the evolution of brain development and obstetric constraints in the human lineage can be addressed with accurate estimates of the size of the brain at birth in hominins. Previous estimates of brain size at birth in fossil hominins have been calculated from regressions of neonatal body or brain mass to adult body mass, but this approach is problematic for two reasons: modern humans are outliers for these regressions, and hominin adult body masses are difficult to estimate. To accurately estimate the brain size at birth in extinct human ancestors, an equation is needed for which modern humans fit the anthropoid regression and one in which the hominin variable entered into the regression equation has limited error. Using phylogenetically sensitive statistics, a resampling approach, and brain-mass data from the literature and from National Primate Research Centers on 362 neonates and 2802 adults from eight different anthropoid species, we found that the size of the adult brain can strongly predict the size of the neonatal brain (r² = 0.97). This regression predicts human brain size, indicating that humans have precisely the brain size expected as an adult given the size of the brain at birth. We estimated the size of the neonatal brain in fossil hominins from a reduced major axis regression equation using published cranial capacities of 89 adult fossil crania. We suggest that australopiths gave birth to infants with cranial capacities that were on average 180 cc (95% CI: 158–205 cc), slightly larger than the average neonatal brain size of chimpanzees. Neonatal brain size increased in early Homo to 225 cc (95% CI: 198–257 cc) and in Homo erectus to approximately 270 cc (95% CI: 237–310 cc). These results have implications for interpreting the evolution of the birth process and brain development in all hominins from the australopiths and early Homo, through H. erectus, to Homo sapiens.