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The growth pattern of Neandertals, reconstructed from a juvenile skeleton from El Sidrón (Spain)

Ontogenetic studies help us understand the processes of evolutionary change but no one single system defines the ontogeny of an individual. Previous studies of Neanderthals have focused more on the pace than the pattern of growth. Thirteen genetically related Neanderthals have been recovered from the 49 ky site of El Sidrón, Asturias, Spain, including a new juvenile partial skeleton for which there is associated dental, cranial and postcranial material. This individual provides the first opportunity to establish chronological age using dental histology with which to compare growth across the skeleton. A team of scientists based in Madrid (led by CSIC's Antonio Rosas and Luis Ríos) and at UCL (CBD's Christopher Dean) and QMUL (Institute of Dentistry's Helen Liversidge) have together explored the development of this specimen. Maturation of almost all cranio-dental and postcranial elements falls within the expected range of modern humans of this age. However, at around 7.7 years of age, the most striking difference in growth between Neanderthals and modern humans occurs in the vertebral column. The atlas and the mid-thoracic vertebral bodies and neural arches remain unfused and at a stage more typical of a modern 5-6 year old child and so appearing to take longer to establish the larger more capacious adult morphology of the Neanderthal chest. Furthermore, a number of endocranial features suggest that at the time of death brain growth was not yet completed. The implication of these findings is that Neanderthal brain growth and somatic growth must have incorporated changes in both rate and timing that differ slightly from modern humans today in order to achieve their adult size.

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A 1.5 million year old archaeological site at the Olduvai Gorge featured extensive river action

This paper investigates the formation history of the early Acheulean site of EF-HR (Olduvai Gorge, Tanzania). The study focuses on the main site (T2-Main Trench) and adjacent trenches (T12 and T9), which constitute the bulk of the archaeological assemblage recently excavated in the EF-HR area (de la Torre et al., submitted). Site formation processes are investigated through taphonomic proxies and spatial analysis, and consider artifact features, orientation patterns, and topographic data retrieved during archaeological excavation. This enables an assessment of the impact of natural agents on the assemblage and a discussion of the relevance of water disturbance in shaping the structure of the EF-HR archaeological record. The results indicate that fluvial action over the assemblage was significant, although it is likely that EF-HR still preserves areas marginally affected by water sorting and rearrangement. In summary, by applying a novel approach that combines a systematic analysis of artifact attributes with GIS spatial analysis of archaeological remains and topographic features, our study aims to provide a fresh look at the interaction of human and natural agents in the formation of Early Stone Age assemblages at Olduvai Gorge.

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Evolutionary processes shaping diversity across the Homo lineage

Recent fossil finds have highlighted extensive morphological diversity within our genus, Homo, and the co-existence of a number of species. However, little is known about the evolutionary processes responsible for producing this diversity. Understanding the action of these processes can provide insight into how and why our lineage evolved and diversified. Here, cranial and mandibular variation are examined and diversification from the earliest emergence of our genus at 2.8 Ma until the Late Pleistocene (0.126–0.0117 Ma), using statistical tests developed from quantitative genetics theory to evaluate whether stochastic (genetic drift) versus non-stochastic (selection) processes were responsible for the observed variation. Results show that random processes can account for species diversification for most traits, including neurocranial diversification, and across all time periods. Where selection was found to shape diversification, we show that: 1) adaptation was important in the earliest migration of Homo out of Africa; 2) selection played a role in shaping mandibular and maxillary diversity among Homo groups, possibly due to dietary differences; and 3) Homo rudolfensis is adaptively different from other early Homo taxa, including the earliest known Homo specimen. These results show that genetic drift, and, likely, small population sizes were important factors shaping the evolution of Homo and many of its novel traits, but that selection played an essential role in driving adaptation to new contexts.

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Computer modelling suggests that cannibalism could have been a factor in the extinction of Homo neanderthalensis

After more than 100,000 years of evolutionary success in Western Eurasia, Neanderthals rapidly went extinct between 40,000 and 30,000 years ago, almost coinciding with the spread of Anatomically Modern Homo sapiens (AMHS) in Europe. Several scenarios relate their extinction to competition with AMHS, climatic changes during the last glacial period or a combination of both. Here we propose a much simpler scenario, in which the cannibalistic behaviour of Neanderthals may have played a major role in their eventual extinction. We show that this trait was selected as a common behaviour at moments of environmental or population stress. However, as soon as Neanderthals had to compete with another species that consumed the same resources (AMHS in this case) cannibalism had a negative impact, leading, in the end, to their extinction. To test this hypothesis, an agent-based model computer simulation was used. The model is simple, with only traits, behaviours and landscape features defined and with no attempt to re-create the exact landscape in which Neanderthals lived or their cultural characteristics. The basic agent of our system is a group of individuals that form a community. The most important state variable of the model is the location of the group, coupled with a defined home range and two additional factors: cannibalism and the chance of fission. The result of the simulation shows that cannibalistic behaviour is always selected when resources are scarce and clustered. However, when a non-cannibalistic species (late Pleistocene AMHS) is introduced into the same environment, the cannibalistic species retreats and the new species grows until it has reached the carrying capacity of the system. The cannibalistic populations that still survive are displaced from the richest areas, and live on the borders with arid zones, a situation which is remarkably similar to what we know about the end of the Neanderthals.

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Accurate age estimation in small-scale societies

Understanding demographic and evolutionary processes shaping human life history diversity depends on precise age estimations. Inferring age is a challenge in small-scale societies, and especially in those societies that do not follow a calendar year. This method opens possibilities in demographic and life history studies allowing cross-sectional data to be incorporated in cross-cultural comparisons and a better understanding of the adaptive importance of human life history variation. This research was conducted by a team of anthropologists and geneticists at the UCL Department of Anthropology and the UCL Genetics Institute

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Further evidence suggests that the EDJ can discriminate to the highest accuracy between different species of hominin

This study explores the morphological differences between the enamel–dentine junction (EDJ) of maxillary and mandibular molars of Neanderthals (n = 150) and recent modern humans (n = 106), and between an earlier Neanderthal sample (consisting of Pre-Eemian and Eemian Neanderthals dating to before 115 ka) and a later Neanderthal sample (consisting of Post-Eemian Neanderthals dating to after 115 ka). The EDJ was visualised by segmenting microtomographic scans of each molar. A geometric morphometric methodology compared the positioning of the dentine horns, the shape of the marginal ridge between the dentine horns, and the shape of the cervix. The palaeoanthropologists also examined the manifestation of non-metric traits at the EDJ including the crista obliqua, cusp 5, and post-paracone tubercle. Furthermore, the team report on additional morphological features including centrally placed dentine horn tips and twinned dentine horns. The results indicate that EDJ morphology can discriminate with a high degree of reliability between Neanderthals and recent modern humans at every molar position, and discriminate between the earlier and the later Neanderthal samples at every molar position, except for the M3 in shape space. The cervix in isolation can also discriminate between Neanderthals and recent modern humans, except at the M3 in form space, and is effective at discriminating between the earlier and the later Neanderthal samples, except at the M2/M2 in form space. In addition to demonstrating the taxonomic valence of the EDJ, the analysis reveals unique manifestations of dental traits in Neanderthals and expanded levels of trait variation that have implications for trait definitions and scoring.

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Rabbit Burrowing casts doubt on Regourdou Homo neanderthalensis burial

The understanding of Neanderthal societies, both with regard to their funerary behaviors and their subsistence activities, is hotly debated. Old excavations and a lack of taphonomic context are often factors that limit our ability to address these questions. To better appreciate the exact nature of what is potentially the oldest burial in Western Europe, Regourdou (Montignac-sur-Vézère, Dordogne), and to better understand the taphonomy of this site excavated more than 50 years ago, it is reported in this contribution a study of the most abundant animals throughout its stratigraphy: the European rabbit (Oryctolagus cuniculus). In addition to questions surrounding the potential bioturbation of the site's stratigraphy, analysis of the Regourdou rabbits could provide new information on Neandertal subsistence behavior. The mortality profile, skeletal-part representation, breakage patterns, surface modification, and comparison with modern reference collections supports the hypothesis that the Regourdou rabbit remains were primarily accumulated due to natural (attritional) mortality. Radiocarbon dates performed directly on the rabbit remains give ages ranging within the second half of Marine Isotope Stage 3, notably younger than the regional Mousterian period.The rabbits dug their burrows within Regourdou's sedimentological filling, likely inhabiting the site after it was filled. The impact of rabbit activity now brings into question both the reliability of the archaeostratigraphy of the site and the paleoenvironmental reconstructions previously proposed for it, and suggests rabbits may have played a role in the distribution of the Neandertal skeletal remains.

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The Greek hominin skull of Apidima 2 has been radiometrically dated to 160,000 years of age

Laser ablation U-series dating results on a human cranial bone fragment from Apidima, on the western cost of the Mani Peninsula, Southern Greece, indicate a minimum age of 160,000 years. The dated cranial fragment belongs to Apidima 2, which preserves the facial skeleton and a large part of the braincase, lacking the occipital bone. The morphology of the preserved regions of the cranium, and especially that of the facial skeleton, indicates that the fossil belongs to the Neanderthal clade. The dating of the fossil at a minimum age of 160,000 years shows that most of the Neanderthal traits were already present in the MIS 6 and perhaps earlier. This makes Apidima 2 the earliest known fossil with a clear Neanderthal facial morphology. Together with the nearby younger Neanderthal specimens from Lakonis and Kalamakia, the Apidima crania are of crucial importance for the evolution of Neanderthals in the area during the Middle to Late Pleistocene. It can be expected that systematic direct dating of the other human fossils from this area will elucidate our understanding of Neanderthal evolution and demise.

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New methodology designed to reconstruct worn wisdom teeth of Homo sapiens

In the last years different methodologies have been developed to reconstruct worn teeth. In this article, a team of palaeoanthropologists, including those of the Department of Anthropology University College London propose a new 2-D methodology to reconstruct the worn enamel of lower molars. Our main goals are to reconstruct molars with a high level of accuracy when measuring relevant histological variables and to validate the methodology calculating the errors associated with the measurements. The new methodology based on polynomial regressions can be confidently applied to the reconstruction of cuspal enamel of lower molars, as it improves the accuracy of the measurements and reduces the interobserver error. The present study shows that it is important to validate all methodologies in order to know the associated errors. This new methodology can be easily exportable to other modern human populations, the human fossil record and forensic sciences.

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Australopithecus sediba was uniquely related to Australopithecus africanus

Malapa Hominin (MH) 1, an immature individual whose second permanent molars had recently reached occlusion at the time of death, is the holotype of Australopithecus sediba, a 2-myr-old South African taxon that has been hypothesized to link phylogenetically australopith-grade hominins to the Homo clade. Given the existence of 2.8 myr-old fossils of Homo in eastern Africa, this hypothesis implies a ghost lineage spanning at least 800 kyr. An alternative hypothesis posits a unique relationship between Au. sediba and Australopithecus africanus, which predates the Malapa hominins in southern Africa and whose phylogenetic relationships remain ambiguous. The craniofacial morphology of MH 1 looms large in the framing of the two hypotheses. These alternatives were evaluated in two ways. First, it was investigated whether the craniofacial morphology of MH 1 was ontogenetically stable at death. Based on data from a late-growth series of chimpanzee, gorilla, and modern human crania, we found that key aspects of MH 1's resemblance to Homo can be accounted for by its immaturity. Second, MH 1 was studied with an eye to identifying craniofacial synapomorphies shared with Au. africanus. In this case, MH 1 shows unambiguous affinities in its zygomaticomaxillary and supraorbital morphology to crania from Sterkfontein Member 4, which we found to exhibit unusual derived morphology compared to Homo and other australopiths. It is argued that MH 1 provides clear evidence that A. sediba was uniquely related to Au. africanus and that the hypothesis of an extensive ghost lineage connecting Au. sediba to the root of the Homo clade is unwarranted.

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Hominin evolution in subequatorial Africa

New discoveries and dating of fossil remains from the Rising Star cave system, Cradle of Humankind, South Africa, have strong implications for our understanding of Pleistocene human evolution in Africa. Direct dating of Homo naledi fossils from the Dinaledi Chamber (Berger et al., 2015) shows that they were deposited between about 236 ka and 335 ka (Dirks et al., 2017), placing H. naledi in the later Middle Pleistocene. Hawks and colleagues (Hawks et al., 2017) report the discovery of a second chamber within the Rising Star system (Dirks et al., 2015) that contains H. naledi remains. Previously, only large-brained modern humans or their close relatives had been demonstrated to exist at this late time in Africa, but the fossil evidence for any hominins in subequatorial Africa was very sparse. It is now evident that a diversity of hominin lineages existed in this region, with some divergent lineages contributing DNA to living humans and at least H. naledi representing a survivor from the earliest stages of diversification within Homo. The existence of a diverse array of hominins in subequatorial comports with our present knowledge of diversity across other savanna-adapted species, as well as with palaeoclimate and paleoenvironmental data. H. naledi casts the fossil and archaeological records into a new light, as we cannot exclude that this lineage was responsible for the production of Acheulean or Middle Stone Age tool industries.

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Pressure flaking to serrate bifacial points for the hunt during the MIS5 at Sibudu Cave (South Africa)

Projectile technology is considered to appear early in the southern African Middle Stone Age (MSA) and the rich and high resolution MSA sequence of Sibudu Cave in KwaZulu-Natal has provided many new insights about the use and hafting of various projectile forms. The results of a functional and technological analysis are presented on a series of unpublished serrated bifacial points recently recovered from the basal deposits of Sibudu Cave. These serrated tools, which only find equivalents in the neighbouring site of Umhlatuzana, precede the Still Bay techno-complex and are older than 77 ka BP. Independent residue and use-wear analyses were performed in a phased procedure involving two separate analysts, which allowed the engagement between two separate lines of functional evidence. Thanks to the excellent preservation at Sibudu Cave, a wide range of animal, plant and mineral residues were observed in direct relation with diagnostic wear patterns. The combination of technological, wear and residue evidence allowed us to confirm that the serration was manufactured with bone compressors and that the serrated points were mounted with a composite adhesive as the tips of projectiles used in hunting activities. The suite of technological and functional data pushes back the evidence for the use of pressure flaking during the MSA and highlights the diversity of the technical innovations adopted by southern African MSA populations. It is suggested the serrated points from the stratigraphic units Adam to Darya of Sibudu illustrate one important technological adaptation of the southern African MSA and provide another example of the variability of MSA bifacial technologies.

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Neandertal and Denisovan DNA from Pleistocene sediments

Although a rich record of Pleistocene human-associated archaeological assemblages exists, the scarcity of hominin fossils often impedes the understanding of which hominins occupied a site. Using targeted enrichment of mitochondrial DNA we show that cave sediments represent a rich source of ancient mammalian DNA that often includes traces of hominin DNA, even at sites and in layers where no hominin remains have been discovered. By automation-assisted screening of numerous sediment samples we detect Neandertal DNA in eight archaeological layers from four caves in Eurasia. In Denisova Cave we retrieved Denisovan DNA in a Middle Pleistocene layer near the bottom of the stratigraphy. Our work opens the possibility to detect the presence of hominin groups at sites and in areas where no skeletal remains are found.

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A team of archaeologists claim archaeological evidence at the 130,000 year old Cerutti Mastodon site, California, USA

The earliest dispersal of humans into North America is a contentious subject, and proposed early sites are required to meet the following criteria for acceptance: (1) archaeological evidence is found in a clearly defined and undisturbed geologic context; (2) age is determined by reliable radiometric dating; (3) multiple lines of evidence from interdisciplinary studies provide consistent results; and (4) unquestionable artefacts are found in primary context1, 2. Here a team of scientists describe the Cerutti Mastodon (CM) site, an archaeological site from the early late Pleistocene epoch, where in situ hammerstones and stone anvils occur in spatio-temporal association with fragmentary remains of a single mastodon (Mammut americanum). The CM site contains spiral-fractured bone and molar fragments, indicating that breakage occured while fresh. Several of these fragments also preserve evidence of percussion. The occurrence and distribution of bone, molar and stone refits suggest that breakage occurred at the site of burial. Five large cobbles (hammerstones and anvils) in the CM bone bed display use-wear and impact marks, and are hydraulically anomalous relative to the low-energy context of the enclosing sandy silt stratum. 230Th/U radiometric analysis of multiple bone specimens using diffusion–adsorption–decay dating models indicates a burial date of 130.7 ± 9.4 thousand years ago. These findings confirm the presence of an unidentified species of Homo at the CM site during the last interglacial period (MIS 5e; early late Pleistocene), indicating that humans with manual dexterity and the experiential knowledge to use hammerstones and anvils processed mastodon limb bones for marrow extraction and/or raw material for tool production. Systematic proboscidean bone reduction, evident at the CM site, fits within a broader pattern of Palaeolithic bone percussion technology in Africa, Eurasia and North America. The CM site is, to the knowledge of the scientists, the oldest in situ, well-documented archaeological site in North America and, as such, substantially revises the timing of arrival of Homo into the Americas.

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