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Chai H. Edge chipping patterns in posterior teeth of hominins and apes. J Mech Behav Biomed Mater 2024; 156:106582. [PMID: 38781774 DOI: 10.1016/j.jmbbm.2024.106582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 05/11/2024] [Accepted: 05/14/2024] [Indexed: 05/25/2024]
Abstract
Chip scars in fossil teeth are a lasting evidence that bears on human evolution. Chip dimensions in posterior teeth of hominins, apes and white-lipped peccary (Tayassu pecari) are measured from published occlusal images. The results are plotted as D/Dm vs. h/Dm, where h, D and Dm denote indent distance, chip width and mean tooth crown diameter. The hominin species follow a similar pattern where D/Dm monotonically increases up to h/Dm ≈ 0.3. The behavior for the apes is characterized by two phases. In the first, h/Dm monotonically increases up to h/Dm ≈ 0.26 while in the second (h/Dm ≈ 0.26 to 0.42), D/Dm experiences a drastic change in behavior. The interpretation of chip morphology is assisted by results from controlled spherical indentation tests on extracted human molars. This study shows that in addition to the commonly recognized chipping due to cusp loading, a chip may also initiate from the inner wall of the tooth's central fossa. Accordingly, it is suggested that the chipping in hominins generally initiates from a (worn) cusp while that in apes involves cusp loading up to h/Dm ≈ 0.26 and fossa loading thereafter. The behavior for T. pecari is much similar to that of the apes. The fossa chipping is facilitated by a consumption of hard, large-size diet (e.g., plants, roots, barks and nuts) and presence of broad central fossa, conditions that are met in apes. Finally, a simple expression for the critical chipping force Pch due to fossa loading is developed.
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Affiliation(s)
- Herzl Chai
- School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv, Israel.
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2
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Martin JM, Leece AB, Baker SE, Herries AIR, Strait DS. A lineage perspective on hominin taxonomy and evolution. Evol Anthropol 2024; 33:e22018. [PMID: 38217397 DOI: 10.1002/evan.22018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 12/16/2023] [Accepted: 12/18/2023] [Indexed: 01/15/2024]
Abstract
An uncritical reliance on the phylogenetic species concept has led paleoanthropologists to become increasingly typological in their delimitation of new species in the hominin fossil record. As a practical matter, this approach identifies species as diagnosably distinct groups of fossils that share a unique suite of morphological characters but, ontologically, a species is a metapopulation lineage segment that extends from initial divergence to eventual extinction or subsequent speciation. Working from first principles of species concept theory, it is clear that a reliance on morphological diagnosabilty will systematically overestimate species diversity in the fossil record; because morphology can evolve within a lineage segment, it follows that early and late populations of the same species can be diagnosably distinct from each other. We suggest that a combination of morphology and chronology provides a more robust test of the single-species null hypothesis than morphology alone.
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Affiliation(s)
- Jesse M Martin
- Palaeoanthropology Lab, Department of Archaeology and History, La Trobe University, Bundoora, Victoria, Australia
| | - A B Leece
- Palaeoanthropology Lab, Department of Archaeology and History, La Trobe University, Bundoora, Victoria, Australia
- Geoarchaeology and Archaeometry Research Group, Southern Cross Geoscience, Southern Cross University, Lismore, New South Wales, Australia
| | - Stephanie E Baker
- Palaeo-Research Institute, University of Johannesburg, Gauteng, South Africa
| | - Andy I R Herries
- Palaeoanthropology Lab, Department of Archaeology and History, La Trobe University, Bundoora, Victoria, Australia
- Palaeo-Research Institute, University of Johannesburg, Gauteng, South Africa
| | - David S Strait
- Palaeo-Research Institute, University of Johannesburg, Gauteng, South Africa
- Department of Anthropology, Washington University in St. Louis, St. Louis, Missouri, USA
- DFG Center for Advanced Studies "Words, Bones, Genes, Tools", University of Tübingen, Tübingen, Germany
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Delezene LK, Scott JE, Irish JD, Villaseñor A, Skinner MM, Hawks J, Berger LR. Sex-biased sampling may influence Homo naledi tooth size variation. J Hum Evol 2024; 187:103490. [PMID: 38266614 DOI: 10.1016/j.jhevol.2023.103490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 12/20/2023] [Accepted: 12/21/2023] [Indexed: 01/26/2024]
Abstract
A frequent source of debate in paleoanthropology concerns the taxonomic unity of fossil assemblages, with many hominin samples exhibiting elevated levels of variation that can be interpreted as indicating the presence of multiple species. By contrast, the large assemblage of hominin fossils from the Rising Star cave system, assigned to Homo naledi, exhibits a remarkably low degree of variation for most skeletal elements. Many factors can contribute to low sample variation, including genetic drift, strong natural selection, biased sex ratios, and sampling of closely related individuals. In this study, we tested for potential sex-biased sampling in the Rising Star dental sample. We compared coefficients of variation for the H. naledi teeth to those for eight extant hominoid samples. We used a resampling procedure that generated samples from the extant taxa that matched the sample size of the fossil sample for each possible Rising Star dental sex ratio. We found that variation at four H. naledi tooth positions-I2, M1, P4, M1-is so low that the possibility that one sex is represented by few or no individuals in the sample cannot be excluded. Additional evidence is needed to corroborate this inference, such as ancient DNA or enamel proteome data, and our study design does not address other potential factors that would account for low sample variation. Nevertheless, our results highlight the importance of considering the taphonomic history of a hominin assemblage and suggest that sex-biased sampling is a plausible explanation for the low level of phenotypic variation found in some aspects of the current H. naledi assemblage.
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Affiliation(s)
- Lucas K Delezene
- Department of Anthropology, University of Arkansas, Fayetteville, AR, 72701, USA; Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS, 2050, South Africa.
| | - Jeremiah E Scott
- Department of Medical Anatomical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, CA, 91766, USA
| | - Joel D Irish
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS, 2050, South Africa; School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, L3 3AF, UK
| | - Amelia Villaseñor
- Department of Anthropology, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Matthew M Skinner
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS, 2050, South Africa; Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103, Leipzig, Germany
| | - John Hawks
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS, 2050, South Africa; Department of Anthropology, University of Wisconsin-Madison. Madison, WI, 53706, USA
| | - Lee R Berger
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS, 2050, South Africa; National Geographic Society, 1145 17th Street NW, Washington DC, 20036, USA
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Villaseñor A, Uno KT, Kinyanjui RN, Behrensmeyer AK, Bobe R, Advokaat EL, Bamford M, Carvalho SC, Hammond AS, Palcu DV, Sier MJ, Ward CV, Braun DR. Pliocene hominins from East Turkana were associated with mesic environments in a semiarid basin. J Hum Evol 2023; 180:103385. [PMID: 37229946 DOI: 10.1016/j.jhevol.2023.103385] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 04/15/2023] [Accepted: 04/19/2023] [Indexed: 05/27/2023]
Abstract
During the middle Pliocene (∼3.8-3.2 Ma), both Australopithecus afarensis and Kenyanthropus platyops are known from the Turkana Basin, but between 3.60 and 3.44 Ma, most hominin fossils are found on the west side of Lake Turkana. Here, we describe a new hominin locality (ET03-166/168, Area 129) from the east side of the lake, in the Lokochot Member of the Koobi Fora Formation (3.60-3.44 Ma). To reconstruct the paleoecology of the locality and its surroundings, we combine information from sedimentology, the relative abundance of associated mammalian fauna, phytoliths, and stable isotopes from plant wax biomarkers, pedogenic carbonates, and fossil tooth enamel. The combined evidence provides a detailed view of the local paleoenvironment occupied by these Pliocene hominins, where a biodiverse community of primates, including hominins, and other mammals inhabited humid, grassy woodlands in a fluvial floodplain setting. Between <3.596 and 3.44 Ma, increases in woody vegetation were, at times, associated with increases in arid-adapted grasses. This suggests that Pliocene vegetation included woody species that were resilient to periods of prolonged aridity, resembling vegetation structure in the Turkana Basin today, where arid-adapted woody plants are a significant component of the ecosystem. Pedogenic carbonates indicate more woody vegetation than other vegetation proxies, possibly due to differences in temporospatial scale and ecological biases in preservation that should be accounted for in future studies. These new hominin fossils and associated multiproxy paleoenvironmental indicators from a single locale through time suggest that early hominin species occupied a wide range of habitats, possibly including wetlands within semiarid landscapes. Local-scale paleoecological evidence from East Turkana supports regional evidence that middle Pliocene eastern Africa may have experienced large-scale, climate-driven periods of aridity. This information extends our understanding of hominin environments beyond the limits of simple wooded, grassy, or mosaic environmental descriptions.
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Affiliation(s)
- Amelia Villaseñor
- Department of Anthropology, The University of Arkansas, 330 Old Main, Fayetteville, AR, 72701, USA.
| | - Kevin T Uno
- Lamont-Doherty Earth Observatory of Columbia University, Division of Biology and Paleo Environment, Palisades, NY, 10964, USA
| | - Rahab N Kinyanjui
- Department of Earth Sciences, National Museums of Kenya, Nairobi, 40658-00100, Kenya; Department of Archaeology, Max Planck Institute of Geoanthropology, 07745, Jena, Germany; Human Origins Program, National Museum of Natural History, Smithsonian Institution, MRC 121, Washington, DC, 20013, USA
| | - Anna K Behrensmeyer
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, MRC 121, Washington, DC, 20013, USA
| | - René Bobe
- Primate Models for Behavioural Evolution Lab, Institute of Human Sciences, University of Oxford, 64 Banbury Road, Oxford, OX2 6PN, UK; Gorongosa National Park, Sofala, Mozambique
| | - Eldert L Advokaat
- Department of Earth Sciences, Utrecht University, Princetonlaan 8A, 3584 CB Utrecht, the Netherlands
| | - Marion Bamford
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, P Bag 3, WITS, 2050, South Africa
| | - Susana C Carvalho
- Primate Models for Behavioural Evolution Lab, Institute of Human Sciences, University of Oxford, 64 Banbury Road, Oxford, OX2 6PN, UK; Gorongosa National Park, Sofala, Mozambique; Interdisciplinary Center for Archaeology and Evolution of Human Behaviour (ICArEHB), Universidade do Algarve, 8005-139, Faro, Portugal
| | - Ashley S Hammond
- Division of Anthropology, American Museum of Natural History (AMNH), New York, NY, 10024, USA; New York Consortium in Evolutionary Primatology at AMNH, New York, NY, 10024, USA
| | - Dan V Palcu
- Oceanographic Institute of the University of São Paulo, Brazil; Paleomagnetic Laboratory 'Fort Hoofddijk', Utrecht University, Budapestlaan 17, 3584 CD, Utrecht, the Netherlands
| | - Mark J Sier
- Centro Nacional de Investigación Sobre la Evolución Humana (CENIEH), Paseo Sierra de Atapuerca 3, 09002, Burgos, Spain; Department of Earth Sciences, University of Oxford, South Parks Road, OX1 3AN, Oxford, UK; Department of Earth Sciences, Utrecht University, Princetonlaan 8A, 3584 CB Utrecht, the Netherlands
| | - Carol V Ward
- Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO, USA
| | - David R Braun
- Center for the Advanced Study of Human Paleobiology, Anthropology Department, George Washington University, Washington, DC, USA
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Comparative description and taxonomic affinity of 3.7-million-year-old hominin mandibles from Woranso-Mille (Ethiopia). J Hum Evol 2022; 173:103265. [PMID: 36306541 DOI: 10.1016/j.jhevol.2022.103265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 09/02/2022] [Accepted: 09/02/2022] [Indexed: 11/06/2022]
Abstract
Fossil discoveries of early Australopithecus species from Woranso-Mille have played a significant role in improving our understanding of mid-Pliocene hominin evolution and diversity. Here, we describe two mandibles with dentitions, recovered from sediments immediately above a tuff radiometrically dated to 3.76 ± 0.02 Ma, and assess their taxonomic affinity. The two mandibles (MSD-VP-5/16 and MSD-VP-5/50) show morphological similarities with both Australopithecus anamensis and Australopithecus afarensis. Some of the unique features that distinguish Au. anamensis from Au. afarensis are present in the mandibles, which also share a few derived features with Au. afarensis. Their retention of more Kanapoi Au. anamensis-like traits, compared to the fewer derived features they share with Au. afarensis, and the presence of Au. anamensis at Woranso-Mille in 3.8-million-year-old deposits, lends support to their assignment to Au. anamensis. However, it is equally arguable that the few derived dentognathic features they share with Au. afarensis could be taxonomically more significant, making it difficult to conclusively assign these specimens to either species. Regardless of which species they are assigned to, the mosaic nature of the dentognathic morphology and geological age of the two mandibles lends further support to the hypothesized ancestor-descendant relationship between Au. anamensis and Au. afarensis. However, there is now limited fossil evidence indicating that these two species may have overlapped in time. Hence, the last appearance of Au. anamensis and first appearance of Au. afarensis are currently unknown. Recovery of Australopithecus fossils from 4.1 to 3.8 Ma is critical to further address the timing of these events.
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Mosaic habitats at Woranso-Mille (Ethiopia) during the Pliocene and implications for Australopithecus paleoecology and taxonomic diversity. J Hum Evol 2022; 163:103076. [PMID: 34998271 DOI: 10.1016/j.jhevol.2021.103076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 08/27/2021] [Accepted: 08/27/2021] [Indexed: 11/21/2022]
Abstract
Many important Pliocene hominin specimens have been recovered from Woranso-Mille, a paleontological research area in the Afar region of Ethiopia, including the complete cranium of Australopithecus anamensis, a partial skeleton of Australopithecus afarensis, mandibular and maxillary elements representing a new species, Australopithecus deyiremeda, and a partial foot of an as-yet-unnamed species. Woranso-Mille is the only site, so far, to have reported the co-existence of more than one early hominin species between 3.8 and 3.3 Ma and the temporal overlap between A. anamensis and A. afarensis. Thus, the site has important implications for our understanding of the paleoecology and taxonomic diversity of early hominins and their ecological niche. This paper explores the paleohabitats of Woranso-Mille through its faunal community ecological structure and taxonomic composition using correspondence analysis and Forbes modified similarity index. The results suggest that Pliocene Woranso-Mille was a mosaic of different habitat types, with riparian woodland and floodplain grassland along rivers draining into a lake, along with less mesic habitats such as woodland, grassland, and shrubland. The apparent high level of vegetation heterogeneity may have promoted dietary specializations and niche differentiation among the different Australopithecus species at Woranso-Mille and allowed for their co-existence at the site.
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