Fossil Hominins Research Articles

A re-analysis of Chibanian Pleistocene tracks from Vértesszőlős, Hungary, employing photogrammetry and 3D analysis

The Vértesszőlős quarry, the Palaeolithic site where the “Samu” hominin fossil remains ( Homo heidelbergensis ) were found, is located in North West Hungary. The site is dated between the Early and Middle Pleistocene (ca. 310 ka). A short distance from where the Samu remains were found is an exposed surface of calcareous mudstone, preserving numerous fossil tracks made by a range of mammals and birds. Of particular interest are three elongate impressions - two potentially successive and one isolated. These tracks have previously been referred to either hominin or ursine trackmakers. Since bear pes tracks can superficially resemble human tracks, we attempted to discern the 3D morphology of the traces using digital photogrammetry. Our analysis suggests the isolated impression is likely the product of two superimposed tracks of a cloven hoofed ungulate. However, the two potentially successive tracks are more problematic. The highly weathered surface (first exposed in the 1960’s) has made interpretation difficult. Both impressions seem to possess a narrow, rounded end similar to the posterior heel margin of a human track. At the anterior end the impressions are broader, and bounded by smaller impressions that could be interpreted as toe marks. However, these two tracks differ considerably in their length/width ratios and are too widely spaced to be part of a single bipedal trackway. It is conceivable that one or both of these impressions may be highly weathered hominin tracks. However, given the highly weathered nature of the exposed surface, and the lack of morphological detail in the tracks, we cannot at this time confidently attribute the tracks to any specific trackmaker, despite our digital models of the tracks which provide a relatively objective means of analysis independent of prior assumptions.

New excavations in the MNK Skull site, and the last appearance of the Oldowan and Homo habilis at Olduvai Gorge, Tanzania

MNK Skull is one of the most significant archaeological sites in Olduvai Gorge, particularly due to the previous discovery of human fossils referred to in the paper where the Homo habilis taxon was originally defined. An important archaeological assemblage is contained in the same horizon as the hominin fossils, constituting the last evidence of both Homo habilis remains and handaxe-free tool kits in the Olduvai Gorge sequence. Our excavations at the site are the first to be conducted since the original work in the 1960s, and sought to refine the archaeological context wherein the Homo habilis remains were discovered. Chronostratigraphic results place the MNK Skull sequence in Middle Bed II prior to deposition of Tuff IIB. The assemblage was deposited near the shoreline, as Palaeolake Olduvai withdrew into the basinal depocentre, and fossils and stone tools were subjected to significant post-depositional processes. The assemblage was affected by mudflow deposits that buried and preserved the assemblage but also entrained surficial bone and lithic elements into the flow. Rather than an occupation site as originally interpreted, the assemblage is better understood as a background deposit, possibly accumulated on an unconformity surface over a long period of time. The stone tool assemblage is typical of the Oldowan, with no technological elements announcing the appearance of the Acheulean, which is well attested to across the Olduvai sequence in post-Tuff IIB times. Our results highlight that, with an approximate age of circa 1.67 Ma, MNK Skull stands as a key site to understand the late Oldowan and the disappearance of Homo habilis in East Africa.

Sex differences in bonobo (Pan paniscus) terrestriality: implications for human evolution.

Recent finds in hominin fossil environments place the transition to terrestriality in a wooded or forested habitat. Therefore, forest-dwelling apes can aid in understanding this important evolutionary transition. Sex differences in ape locomotion have been previously attributed to sexual dimorphism or ecological niche differences between males and females. This study examined the hypothesis that differential advantages of terrestrial travel may impact mating success in male bonobos. We examined whether males are more terrestrial when there are mating benefits for fast travel. We analyzed behavioral data on wild bonobos over a ten-month period in the Lomako Forest, DRC and examined the proportion of time spent at lower heights compared to higher heights between adult females and males relative to their location to feeding contexts with high mating frequencies. We found a significant interaction between sex and height class away from food patches (F=4.65, df =1, p <0.05) such that females were primarily arboreal whereas there was no difference between males across height classes. However, there was also a significant interaction between sex and height class (F =29.35, df =1, p <0.0001) for adults traveling near or entering a food patch. Males often arrived at food patches terrestrially and females arrived almost exclusively arboreally. We found a significant difference between the expected and observed distribution of matings by food patch context (G =114.36, df =4, p <0.0001) such that most mating occurred near or in a food patch. These results suggest that males may travel terrestrially to arrive at food patches before cohesive parties of females arrive arboreally, in order to compete with other males for mating access to these females. Such intrasexual selection for sex differences in locomotion may be important in considerations of the evolution of locomotion strategies in hominins in a forested environment.

Frontal bone virtual reconstruction and geometric morphometric analysis of the mid-Pleistocene hominin KNM-OG 45500 (Olorgesailie, Kenya).

KNM-OG 45500 is a hominin fossil composed of parts of a frontal bone, left temporal bone, and cranial vault pieces. Since its discovery along the Olorgesailie Formation (Kenya) in 2003, it has been associated with the Homo erectus hypodigm. The specimen, derived from a geological context dated to ca. 900 Ka BP, has been described as a very small individual of probable female sex. However, despite its status as an important hominin specimen, it has not been used in a quantitative comparative framework because of its fragmentary condition. Here, we undertake a virtual reconstruction of the better-preserved fragment, the frontal bone. We additionally apply geometric morphometric analyses, using a geographically diverse fossil and modern human sample, in order to investigate the morphological affinities of KNM-OG 45500. Our results show that the frontal shape of KNM-OG 45500 exhibits similarities with Early Pleistocene fossils from Eurasia and Africa that are assigned to H. erectus sensu lato (s.l.). Its size, on the other hand, is notably smaller than most other Homo erectus fossils and modern humans and similar to the specimens from Dmanisi (Georgia) and to Homo naledi. Taken together, our analyses of the frontal bone suggest a taxonomic attribution of KNM-OG 45500 to H. erectus s.l. and extend even further the range of size variability associated with this taxon around 900 Ka BP.

Magnetostratigraphy of the Hominin Sites and Paleolakes Drilling Project (HSPDP) Baringo-Tugen Hills-Barsemoi core (Kenya)

The principal objective of the Hominin Sites and Paleolakes Drilling project (HSPDP) is to study the relationship between climate and environmental change and the implications on human evolution in eastern Africa. For this purpose, HSPDP has recovered a 228 m core in the Chemeron Formation of the Baringo Basin (Kenya). The Chemeron Formation spans approximately 3.7 Myr, from around 1.6 to 5.3 Ma, and has yielded many vertebrate fossils, including fossil hominins. The magnetostratigraphy of the Baringo core contributes to the chronological framework. A total of 567 individual paleomagnetic samples were collected from 543 levels at regular intervals throughout the core and 264 were processed using thermal and alternative field stepwise demagnetizations. In most samples, distinct Low-Temperature (LT; 20–150 °C) and High-Temperature (HT; 150–550 °C) Characteristic Remanent Magnetization (ChRM) could be determined. Typical demagnetization behaviors and some rock magnetic experiments suggest titanomagnetite acts as the main carrier of the HT ChRM with pervasive secondary overprints in normal polarity expressed by the LT component. Normal and reversed polarities were identified based on the secondary overprints LT ChRM directions, either parallel or antiparallel to the HT ChRM directions respectively. Our study identified four paleomagnetic reversals interpreted as the Matuyama-Gauss, Gauss-Kaena, Kaena-Gauss and the Gauss-Mammoth transitions. These boundaries provide chronostratigraphic tie-points that can be combined with those derived from 40Ar/39Ar dating of tuffs (Deino et al., 2020) and together indicate that the HSPDP Baringo core has an age range of ~3.3 Ma to ~2.6 Ma. The consistent paleomagnetic and radioisotopic age constraints are incorporated into a Bayesian age model of the core (Deino et al., 2020).

Virtual reconstruction of the Kebara 2 Neanderthal pelvis

The paucity of well-preserved pelvises in the hominin fossil record has hindered robust analyses of shifts in critical biological processes throughout human evolution. The Kebara 2 pelvis remains one of the best preserved hominin pelvises, providing a rare opportunity to assess Neanderthal pelvic morphology and function. Here, we present two new reconstructions of the Kebara 2 pelvis created from CT scans of the right hip bone and sacrum. For both reconstructions, we proceeded as follows. First, we virtually reconstructed the right hip bone and the sacrum by repositioning the fragments of the hip bone and sacrum. Then, we created a mirrored copy of the right hip bone to act as the left hip bone. Next, we 3D printed the three bones and physically articulated them. Finally, we used fiducial points collected from the physically articulated models to articulate the hip bones and sacrum in virtual space. Our objectives were to (1) reposition misaligned fragments, particularly the ischiopubic ramus; (2) create a 3D model of a complete pelvis; and (3) assess interobserver reconstruction variation. These new reconstructions show that, in comparison with previous measurements, Kebara 2 possessed a higher shape index (maximum anteroposterior length/maximum mediolateral width) for the pelvic inlet and perhaps the outlet and a more anteriorly positioned sacral promontory and pubic symphysis relative to the acetabula. The latter differences result in a lower ratio between the distances anterior and posterior to the anterior margins of the acetabula. Generally, the new reconstructions tend to accentuate features of the Kebara 2 pelvis––the long superior pubic ramus and anteriorly positioned pelvic inlet––that have already been discussed for Kebara 2 and other Neanderthals.

Searching for the “Roots” of Masculinity in Primates and the Human Evolutionary Past

The reconstruction and prioritization of masculinity in human evolution (and thus human nature) is often rooted in reference to other primates and the hominin fossil and archaeological record. And it almost always involves violence. Whether it be the “demonic males” hypothesis, the trope of aggressive alpha maleness and sexual coercion, or gender-biased representations of toolmaking, hunting, and fierce encounters between different populations of the genus Homo in the Pleistocene, a particular pattern of masculinity (maleness)—and violence—permeates most popular discourse and much of the academic discourse. While there are some significant sexual differences and divergent strategies among our closest cousins, and the fossil record does offer important insights into the development and deployment of gender, much of the data do not fit seamlessly with typical assumptions. In fact, much in our contemporary understandings of other primate behavior and the hominins either contradicts or complexifies assumptions and assertions about the origins and “ancestral” patterns of contemporary human masculinity and its associated violence. This paper articulates what we do and do not know about maleness in primates and past humans and offers some possibilities for how such information might assist in elaborating more integrative understandings of the complexities of human masculinities.

Chipping and wear patterns in extant primate and fossil hominin molars: ‘Functional’ cusps are associated with extensive wear but low levels of fracture

Chipping and wear patterns in extant primate and fossil hominin molars: ‘Functional’ cusps are associated with extensive wear but low levels of fracture

In situ observations on the dentition and oral cavity of the Neanderthal skeleton from Altamura (Italy).

The Neanderthal specimen from Lamalunga Cave, near Altamura (Apulia, Italy), was discovered during a speleological survey in 1993. The specimen is one of the most complete fossil hominins in Europe and its state of preservation is exceptional, although it is stuck in calcareous concretions and the bones are mostly covered by calcite depositions. Nevertheless, it is possible to carry out some observations on craniodental features that have not previously been described. In this work, we present an account of the oral cavity, made possible by the use of a videoscope, which allowed us to reach some hidden parts of the mandible and palate. This is the first detailed overview of the teeth and maxillary bones of the Neanderthal skeleton from Altamura. The dentition is almost complete. However, two teeth (upper right P3 and upper left M1) were lost ante mortem and four teeth (lower right I1 and P3 and lower left I1 and I2) were lost most probably post mortem. Dental wear is marked. The erupted M3s and the inversion of the compensating curve of Wilson in the M1s and M2s but not in the M3s suggest that the individual is fully adult, but not old. Although most of the teeth have their roots exposed for several millimeters, the periodontal bone appears to be in good condition overall, except in correspondence of the two ante-mortem tooth losses. X-rays of the anterior teeth show a periapical lesion, probably linked to the advanced dental wear. We also observed a weak expression of taurodontism in the posterior dentition and the presence of a retromolar space, features consistent with an attribution to the Neanderthal hypodigm; this attribution is also supported by aspects of the cranial morphology, the morphometric analysis of the scapula and preliminary mtDNA data. There is also a well-developed palatine torus, to the best of our knowledge a feature not previously described in Neanderthals.

Ingestive behaviors in bearded capuchins (Sapajus libidinosus)

The biomechanical and adaptive significance of variation in craniodental and mandibular morphology in fossil hominins is not always clear, at least in part because of a poor understanding of how different feeding behaviors impact feeding system design (form–function relationships). While laboratory studies suggest that ingestive behaviors produce variable loading, stress, and strain regimes in the cranium and mandible, understanding the relative importance of these behaviors for feeding system design requires data on their use in wild populations. Here we assess the frequencies and durations of manual, ingestive, and masticatory behaviors from more than 1400 observations of feeding behaviors video-recorded in a wild population of bearded capuchins (Sapajus libidinosus) at Fazenda Boa Vista in Piauí, Brazil. Our results suggest that ingestive behaviors in wild Sapajus libidinosus were used for a range of food material properties and typically performed using the anterior dentition. Coupled with previous laboratory work indicating that ingestive behaviors are associated with higher mandibular strain magnitudes than mastication, these results suggest that ingestive behaviors may play an important role in craniodental and mandibular design in capuchins and may be reflected in robust adaptations in fossil hominins.

Exploring the diversity of fossil hominin dental patterns in the western Indonesian archipelago during the Quaternary by Geometric Morphometric Analysis. Application on second upper and lower molars

Islands of the western part of the Indonesian archipelago were impacted by climatic and sea level changes during Pleistocene, which affected the dispersals and/or isolation of hominins in this region. This study aims to characterize the diversity of ancient human populations in the Sundaland based on dental collections from several localities in Sumatra and Java. The material consists of 111 teeth, 57 from Pleistocene hominins and 54 from Holocene Homo sapiens. The study of external morphology was done by geometric morphometric analysis on the occlusal surface of the upper (N=47) and lower second molars (N=64). We observe group clustering among the samples. There are at least four groups (dental types) of hominins during Pleistocene times. Result suggest that there is an overlapping among them throughout the Lower and early Middle Pleistocene; another group persists until the Late Pleistocene, and two other groups of H. sapiens are present during the Holocene. The implication of this study sheds light on the history of ancient human occupation (continuity/rupture) in Island Southeast Asia during the Quaternary period.

Rediscovery of fossils from the middle gravels and lower loam at Barnfield Pit, Swanscombe, Kent (UK)

Swanscombe is the most important early human fossil site in the UK, and one of the richest locations for Middle Pleistocene fauna. Famed for three 400,000-year-old hominin skull fragments recovered from Barnfield Pit between 1935 and 1955, the site is now legally protected and has not seen substantial excavation for decades. New fossil material from Swanscombe is fleetingly rare. Here we report the rediscovery of a collection of fossils recovered from Barnfield Pit between 1951 and 1955 by John Carreck. The ‘Carreck Collection’ includes multiple mammalian fossils from the hominin fossil and artefact-bearing Middle Gravels and Lower Loam. Detailed notes contained in the collection reveal that most were recovered prior to John Wymer’s discovery of the third hominin skull fragment on the 30th of July 1955. Several, however, were collected in the months immediately after this, including at least two fossils recovered from the ‘New Skull Site’ on the 3rd of August 1955. Given their provenance and the nature of their discovery, these fossils are of significance to the history of British human origins research. Only a portion of the Carreck Collection, however, is currently accounted for. There is potential, therefore, for other fossils from Barnfield Pit to be rediscovered, including those with significance to our understanding of human prehistory in the UK.

Characterized by Darkness: Reconsidering the Origins of the Brutish Neanderthal.

The extinct human relatives known as Neanderthals (Homo neanderthalensis) have long been described as brutish and dumb. This conception is often traced to paleontologist Marcellin Boule (1861-1942), who published a detailed analysis on a Neanderthal skeleton in the early twentieth century. The conventional historical narrative claims that Boule made an error in his analysis, causing the Neanderthals to be considered brutish. This essay challenges the narrative of "Boule's error," arguing instead that the brutish Neanderthal concept originated much earlier in the history of Neanderthal research and was, in fact, an invention of the earliest analyses of the first specimen recognized as a Neanderthal in the mid-nineteenth century. I argue that temporally relocating this conception of Neanderthals allows for a better understanding of the interconnected nature of the study of fossil humans and the science of living human races during the nineteenth century. This new view of the brutish Neanderthal sheds light on the earliest phases of the science that became paleoanthropology, while examining the racial, cultural, and political attitudes about race and extinction that accompanied the science at that time. By inspecting the ways in which the Neanderthals' image was a product of a particular time and place, we gain a perspective that provides a new basis for thinking about the conceptions of hominin fossil species.

Microevolution in our megadont relative

Cranial variation in South African specimens of Paranthropus robustus illustrate temporal changes that suggest how the morphology of this hominin fossil species related to its palaeoenvironment and microevolutionary processes.

The Sima de los Huesos Middle Pleistocene hominin site (Burgos, Spain). Estimation of the number of individuals.

After 34 years of research and findings in the Middle Pleistocene site of the Sima de los Huesos (SH) of the Sierra de Atapuerca (Burgos, Spain), we present an update of the estimation of the number of individuals (ENI) identified in the SH hominin assemblage. The last ENI, published in 2004, was 28. Although the number of specimens recovered has almost doubled since then and more complete information is now available, this new analysis suggests that the ENI is 29. Some individuals are still represented by only one or a few teeth and the upper and lower jaws of various individuals have not been completed. We suggest that the amateur cavers, who accessed the SH site for years looking for bear fossils, destroyed a significant number of hominin fossils. Despite this, we have a good picture of the group of hominins represented in the SH assemblage. Because complete corpses were accumulated in SH and it is a closed cavity, it is expected that a significant number of hominin fossils remains to be discovered. According to the previous estimates, the representation of females is greater than that of males. However, the observed sex ratio is not significantly different from the 1:1 ratio. With the exception of the possible presence of a child individual, most of the remaining 28 individuals are teenagers or young adults (24/28=0.857). The ages of death of SH hominins appear to conform to a catastrophic profile.

Growth and development of the third permanent molar in Paranthropus robustus from Swartkrans, South Africa

Third permanent molars (M3s) are the last tooth to form but have not been used to estimate age at dental maturation in early fossil hominins because direct histological evidence for the timing of their growth has been lacking. We investigated an isolated maxillary M3 (SK 835) from the 1.5 to 1.8-million-year-old (Mya) site of Swartkrans, South Africa, attributed to Paranthropus robustus. Tissue proportions of this specimen were assessed using 3D X-ray micro-tomography. Thin ground sections were used to image daily growth increments in enamel and dentine. Transmitted light microscopy and synchrotron X-ray fluorescence imaging revealed fluctuations in Ca concentration that coincide with daily growth increments. We used regional daily secretion rates and Sr marker-lines to reconstruct tooth growth along the enamel/dentine and then cementum/dentine boundaries. Cumulative growth curves for increasing enamel thickness and tooth height and age-of-attainment estimates for fractional stages of tooth formation differed from those in modern humans. These now provide additional means for assessing late maturation in early hominins. M3 formation took ≥ 7 years in SK 835 and completion of the roots would have occurred between 11 and 14 years of age. Estimated age at dental maturation in this fossil hominin compares well with what is known for living great apes.

Comparative anatomy and 3D geometric morphometrics of the El Sidrón atlases (C1)

The first cervical vertebra (atlas, C1) is an important element of the vertebral column because it connects the cranial base with the cervical column, thus helping to maintain head posture and contributing to neck mobility. However, few atlases are preserved in the fossil record because of the fragility of this vertebra. Consequently, only eight well-preserved atlases from adult Neandertals have been recovered and described. Here, we present nine new atlas remains from the El Sidrón Neandertal site (Asturias, Spain), two of which (SD-1643 and SD-1605/1595) are sufficiently well preserved to allow for a detailed comparative and three-dimensional geometric morphometric analysis. We compared standard linear measurements of SD-1643 and SD-1605/1595 with those of other Neandertal atlases and carried out three-dimensional geometric morphometric analyses to compare size and shape of SD-1643 and SD-1605/1595 with those of 28 Pan (Pan troglodytes and Pan paniscus), a broad comparative sample of 55 anatomically modern humans from African and European populations, and other fossil hominins (Neandertals, Homo antecessor, Paranthropus boisei). The El Sidrón atlas fossils show typical features of the Neandertal atlas morphology, such as caudal projection of the anterior tubercle, gracility of both the posterior tubercle and the tuberosity for the insertion of the transverse ligament, and an anteroposteriorly elongated neural canal. Furthermore, when compared with atlases from the other taxa, Neandertals exhibit species-specific features of atlas morphology including a relatively lower lateral mass height, relatively narrower transverse foramina, and flatter and more horizontally oriented articular facets. Some of these features fit with previous suggestions of shorter overall length of the cervical spine and potential differences in craniocervical posture and mobility. Our results may support a different spinopelvic alignment in this species, as the atlas morphology suggests reduced cervical lordosis.

Birth of Homo erectus.

Eugène Dubois was the pioneer of human origins research in South-East Asia, specifically on two of the islands, Sumatra and Java, now included in Indonesia. Dubois was a polymath, whose research interests embraced encephalization and hydrology as well as paleoanthropology. His interpretations of the hominin fossil evidence he collected, which he eventually assigned to Pithecanthropus erectus, changed over the years, and he evidently felt defensive about those interpretations, but in his 1894 paper he presents cogent reasons for his decision. The taxon he introduced is still recognized, and while it is no longer seen as "the" link between fossil apes and modern humans, it is currently one of the longest surviving hominin taxa.

A comprehensive survey of Retzius periodicities in fossil hominins and great apes

Recent studies have provided great insight into hominin life history evolution by utilizing incremental lines found in dental tissues to reconstruct and compare the growth records of extant and extinct humans versus other ape taxa. Among the hominins, studies that have examined Retzius periodicity (RP) variation have come to contradictory conclusions in some instances. To clarify RP variation among hominins and better place this variation in its broader evolutionary context, we conduct the most comprehensive analysis of published RP values for hominins and great apes to date. We gathered all available data from the literature on RP data from extant humans, great apes, and fossil hominins and assessed their variation using parametric and nonparametric analyses of variance. We also performed phylogenetic generalized least-squares regressions of RP data for these taxa as well as a larger set of hominoids for which RP data have been published against data for body mass, encephalization, and mean semicircular canal radius (a proxy for metabolic rate). Our results show that modern humans have a mean RP significantly differing from that of other hominins. Pongo also is significantly different from nearly all other taxa in all analyses. Our results also demonstrate that RP variation among hominins scales with respect to body mass, encephalization, and semicircular canal radius similarly to other hominids but that modern humans and Pongo stand out in this regard. Operating within the hypothesis that RP reflects autonomic biorhythms that regulate multiple life history variables, our results reinforce the idea that Homo sapiens has evolved a life history distinct from other hominins, even from other members of Homo, and suggest that many of these life history differences may be driven by hypothalamic output from the brain.

A Major Change in Rate of Climate Niche Envelope Evolution during Hominid History.

SummaryHomo sapiens is the only species alive able to take advantage of its cognitive abilities to inhabit almost all environments on Earth. Humans are able to culturally construct, rather than biologically inherit, their occupied climatic niche to a degree unparalleled within the animal kingdom. Precisely, when hominins acquired such an ability remains unknown, and scholars disagree on the extent to which our ancestors shared this same ability. Here, we settle this issue using fine-grained paleoclimatic data, extensive archaeological data, and phylogenetic comparative methods. Our results indicate that whereas early hominins were forced to live under physiologically suitable climatic conditions, with the emergence of H. heidelbergensis, the Homo climatic niche expanded beyond its natural limits, despite progressive harshening in global climates. This indicates that technological innovations providing effective exploitation of cold and seasonal habitats predated the emergence of Homo sapiens.