SciCombinator

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Concept: Homo ergaster

318

Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.

Concepts: Human, Africa, Species, Kenya, Human evolution, Homo erectus, Homo ergaster, Homo habilis

170

The Middle Pleistocene is a crucial time period for studying human evolution in Europe, because it marks the appearance of both fossil hominins ancestral to the later Neandertals and the Acheulean technology. Nevertheless, European sites containing well-dated human remains associated with an Acheulean toolkit remain scarce. The earliest European hominin crania associated with Acheulean handaxes are at the sites of Arago, Atapuerca Sima de los Huesos (SH), and Swanscombe, dating to 400-500 ka (Marine Isotope Stage 11-12). The Atapuerca (SH) fossils and the Swanscombe cranium belong to the Neandertal clade, whereas the Arago hominins have been attributed to an incipient stage of Neandertal evolution, to Homo heidelbergensis, or to a subspecies of Homo erectus A recently discovered cranium (Aroeira 3) from the Gruta da Aroeira (Almonda karst system, Portugal) dating to 390-436 ka provides important evidence on the earliest European Acheulean-bearing hominins. This cranium is represented by most of the right half of a calvarium (with the exception of the missing occipital bone) and a fragmentary right maxilla preserving part of the nasal floor and two fragmentary molars. The combination of traits in the Aroeira 3 cranium augments the previously documented diversity in the European Middle Pleistocene fossil record.

Concepts: Human, Evolution, Neanderthal, Human evolution, Homo erectus, Homo ergaster, Acheulean, Homo heidelbergensis

150

African archaic humans dated to around 1,0 Ma share morphological affinities with Homo ergaster and appear distinct in cranio-dental morphology from those of the Middle Pleistocene that are referred to Homo heidelbergensis. This observation suggests a taxonomic and phylogenetic discontinuity in Africa that ranges across the Matuyama/Brunhes reversal (780 ka). Yet, the fossil record between roughly 900 and 600 ka is notoriously poor. In this context, the Early Stone Age site of Gombore II, in the Melka Kunture formation (Upper Awash, Ethiopia), provides a privileged case-study. In the Acheulean layer of Gombore II, somewhat more recent than 875 ±10 ka, two large cranial fragments were discovered in 1973 and 1975 respectively: a partial left parietal (Melka Kunture 1) and a right portion of the frontal bone (Melka Kunture 2), which probably belonged to the same cranium. We present here the first detailed description and computer-assisted reconstruction of the morphology of the cranial vault pertaining to these fossil fragments. Our analysis suggest that the human fossil specimen from Gombore II fills a phenetic gap between Homo ergaster and Homo heidelbergensis. This appears in agreement with the chronology of such a partial cranial vault, which therefore represents at present one of the best available candidates (if any) for the origin of Homo heidelbergensis in Africa.

Concepts: Human, Africa, Skull, Human evolution, Homo erectus, Homo ergaster, Acheulean, Homo heidelbergensis

143

Bipedalism is a defining feature of the human lineage. Despite evidence that walking on two feet dates back 6-7 Ma, reconstructing hominin gait evolution is complicated by a sparse fossil record and challenges in inferring biomechanical patterns from isolated and fragmentary bones. Similarly, patterns of social behavior that distinguish modern humans from other living primates likely played significant roles in our evolution, but it is exceedingly difficult to understand the social behaviors of fossil hominins directly from fossil data. Footprints preserve direct records of gait biomechanics and behavior but they have been rare in the early human fossil record. Here we present analyses of an unprecedented discovery of 1.5-million-year-old footprint assemblages, produced by 20+ Homo erectus individuals. These footprints provide the oldest direct evidence for modern human-like weight transfer and confirm the presence of an energy-saving longitudinally arched foot in H. erectus. Further, print size analyses suggest that these H. erectus individuals lived and moved in cooperative multi-male groups, offering direct evidence consistent with human-like social behaviors in H. erectus.

Concepts: Human, Human behavior, Neanderthal, Human evolution, Hominina, Homo erectus, Hominini, Homo ergaster

96

Human evolutionary scholars have long supposed that the earliest stone tools were made by the genus Homo and that this technological development was directly linked to climate change and the spread of savannah grasslands. New fieldwork in West Turkana, Kenya, has identified evidence of much earlier hominin technological behaviour. We report the discovery of Lomekwi 3, a 3.3-million-year-old archaeological site where in situ stone artefacts occur in spatiotemporal association with Pliocene hominin fossils in a wooded palaeoenvironment. The Lomekwi 3 knappers, with a developing understanding of stone’s fracture properties, combined core reduction with battering activities. Given the implications of the Lomekwi 3 assemblage for models aiming to converge environmental change, hominin evolution and technological origins, we propose for it the name ‘Lomekwian’, which predates the Oldowan by 700,000 years and marks a new beginning to the known archaeological record.

Concepts: Human, Evolution, Human evolution, Archaeology, Homo ergaster, Savanna, Stone tool, Archaeological site

91

The evolutionary origin of Homo floresiensis, a diminutive hominin species previously known only by skeletal remains from Liang Bua in western Flores, Indonesia, has been intensively debated. It is a matter of controversy whether this primitive form, dated to the Late Pleistocene, evolved from early Asian Homo erectus and represents a unique and striking case of evolutionary reversal in hominin body and brain size within an insular environment. The alternative hypothesis is that H. floresiensis derived from an older, smaller-brained member of our genus, such as Homo habilis, or perhaps even late Australopithecus, signalling a hitherto undocumented dispersal of hominins from Africa into eastern Asia by two million years ago (2 Ma). Here we describe hominin fossils excavated in 2014 from an early Middle Pleistocene site (Mata Menge) in the So'a Basin of central Flores. These specimens comprise a mandible fragment and six isolated teeth belonging to at least three small-jawed and small-toothed individuals. Dating to ~0.7 Ma, these fossils now constitute the oldest hominin remains from Flores. The Mata Menge mandible and teeth are similar in dimensions and morphological characteristics to those of H. floresiensis from Liang Bua. The exception is the mandibular first molar, which retains a more primitive condition. Notably, the Mata Menge mandible and molar are even smaller in size than those of the two existing H. floresiensis individuals from Liang Bua. The Mata Menge fossils are derived compared with Australopithecus and H. habilis, and so tend to support the view that H. floresiensis is a dwarfed descendent of early Asian H. erectus. Our findings suggest that hominins on Flores had acquired extremely small body size and other morphological traits specific to H. floresiensis at an unexpectedly early time.

Concepts: Human, Neanderthal, Homo erectus, Homo floresiensis, Flores, Homo ergaster

82

Homo floresiensis is an extinct, diminutive hominin species discovered in the Late Pleistocene deposits of Liang Bua cave, Flores, eastern Indonesia. The nature and evolutionary origins of H. floresiensis' unique physical characters have been intensively debated. Based on extensive comparisons using linear metric analyses, crown contour analyses, and other trait-by-trait morphological comparisons, we report here that the dental remains from multiple individuals indicate that H. floresiensis had primitive canine-premolar and advanced molar morphologies, a combination of dental traits unknown in any other hominin species. The primitive aspects are comparable to H. erectus from the Early Pleistocene, whereas some of the molar morphologies are more progressive even compared to those of modern humans. This evidence contradicts the earlier claim of an entirely modern human-like dental morphology of H. floresiensis, while at the same time does not support the hypothesis that H. floresiensis originated from a much older H. habilis or Australopithecus-like small-brained hominin species currently unknown in the Asian fossil record. These results are however consistent with the alternative hypothesis that H. floresiensis derived from an earlier Asian Homo erectus population and experienced substantial body and brain size dwarfism in an isolated insular setting. The dentition of H. floresiensis is not a simple, scaled-down version of earlier hominins.

Concepts: Human, Hominidae, Neanderthal, Human evolution, Homo erectus, Homo floresiensis, Flores, Homo ergaster

47

The archaeological record indicates that elephants must have played a significant role in early human diet and culture during Palaeolithic times in the Old World. However, the nature of interactions between early humans and elephants is still under discussion. Elephant remains are found in Palaeolithic sites, both open-air and cave sites, in Europe, Asia, the Levant, and Africa. In some cases elephant and mammoth remains indicate evidence for butchering and marrow extraction performed by humans. Revadim Quarry (Israel) is a Late Acheulian site where elephant remains were found in association with characteristic Lower Palaeolithic flint tools. In this paper we present results regarding the use of Palaeolithic tools in processing animal carcasses and rare identification of fat residue preserved on Lower Palaeolithic tools. Our results shed new light on the use of Palaeolithic stone tools and provide, for the first time, direct evidence (residue) of animal exploitation through the use of an Acheulian biface and a scraper. The association of an elephant rib bearing cut marks with these tools may reinforce the view suggesting the use of Palaeolithic stone tools in the consumption of large game.

Concepts: Human evolution, Paleolithic, Stone Age, Prehistory, Homo ergaster, Stone tool, Lithics, Acheulean

44

Our understanding of the origin of the genus Homo has been hampered by a limited fossil record in eastern Africa between 2.0 and 3.0 million years ago (Ma). Here we report the discovery of a partial hominin mandible with teeth from the Ledi-Geraru research area, Afar Regional State, Ethiopia, that establishes the presence of Homo at 2.80-2.75 Ma. This specimen combines primitive traits seen in early Australopithecus with derived morphology observed in later Homo, confirming that dentognathic departures from the australopith pattern occurred early in the Homo lineage. The Ledi-Geraru discovery has implications for hypotheses about the timing and place of the origin of the genus Homo.

Concepts: Human, Observation, Human evolution, Australopithecus afarensis, Hominina, Homo ergaster, Horn of Africa, Transitional fossil

28

The biomechanical characterization of lower limb long bones in the chrono-ecogeographically diverse species Homo erectus is a fundamental step for assessing evolutionary changes in locomotor mode and body shape that occurred within the genus Homo. However, the samples available for the Early and earlier Middle Pleistocene are small and widely scattered in time and space, thus limiting our understanding of the nature and polarity of morphological trends. Compared to the African fossil record, loading histories based on detailed biomechanical assessment of diaphyseal strength in Indonesian H. erectus lower limb long bones have not been assessed. By using a microtomographic record (μCT), we performed a quantitative analysis of the biomechanical properties and structural organization of Kresna 11, a late Early Pleistocene adult H. erectus femoral shaft from the Sangiran Dome, Central Java. Relative to the modern human condition, Kresna 11 shows the predominant mediolateral cortical thickening (hypertrophy) and the distal displacement of the minimum diaphyseal breadth characteristic of early Homo femora, associated nonetheless with relatively modest cortical thickness within the mid-proximal portion. Synthetic functional imaging of the shaft through the planar representation of its inner structure has revealed distal thickening of the medial cortex, a feature previously unreported in H. erectus. The increase in relative mediolateral bending strength observed in Kresna 11 supports the hypothesis that, rather than simply reflecting differences in patterns of locomotor loading, biomechanical properties of the femoral shaft in archaic Homo are strongly influenced by body shape, i.e., variations in pelvic breadth and femoral neck length.

Concepts: Human, Evolution, Cerebral cortex, Fossil, Human evolution, Archaic Homo sapiens, Homo erectus, Homo ergaster