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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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Delezene LK, Skinner MM, Bailey SE, Brophy JK, Elliott MC, Gurtov A, Irish JD, Moggi-Cecchi J, de Ruiter DJ, Hawks J, Berger LR. Descriptive catalog of Homo naledi dental remains from the 2013 to 2015 excavations of the Dinaledi Chamber, site U.W. 101, within the Rising Star cave system, South Africa. J Hum Evol 2023; 180:103372. [PMID: 37229947 DOI: 10.1016/j.jhevol.2023.103372] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 03/31/2023] [Accepted: 03/31/2023] [Indexed: 05/27/2023]
Abstract
More than 150 hominin teeth, dated to ∼330-241 thousand years ago, were recovered during the 2013-2015 excavations of the Dinaledi Chamber of the Rising Star cave system, South Africa. These fossils comprise the first large single-site sample of hominin teeth from the Middle Pleistocene of Africa. Though scattered remains attributable to Homo sapiens, or their possible lineal ancestors, are known from older and younger sites across the continent, the distinctive morphological feature set of the Dinaledi teeth supports the recognition of a novel hominin species, Homo naledi. This material provides evidence of African Homo lineage diversity that lasts until at least the Middle Pleistocene. Here, a catalog, anatomical descriptions, and details of preservation and taphonomic alteration are provided for the Dinaledi teeth. Where possible, provisional associations among teeth are also proposed. To facilitate future research, we also provide access to a catalog of surface files of the Rising Star jaws and teeth.
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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.
| | - Matthew M Skinner
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa; School of Anthropology and Conservation, University of Kent, Marlowe Building, Canterbury CT2 7NR, UK; Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany
| | - Shara E Bailey
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany; Department of Anthropology, Center for the Study of Human Origins, New York University, New York, NY 10003, USA
| | - Juliet K Brophy
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa; Department of Geography and Anthropology, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Marina C Elliott
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa; Department of Archaeology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, USA
| | - Alia Gurtov
- Stripe, Inc., 199 Water Street, 30th Floor, New York, NY 10038, 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
| | - Jacopo Moggi-Cecchi
- Laboratory of Anthropology, Department of Biology, University of Florence, Via del Proconsolo 12, Firenze 50122, Italy
| | - Darryl J de Ruiter
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa; Department of Anthropology, Texas A&M University, College Station, TX 77843, USA
| | - 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
- National Geographic Society, 1145 17th Street NW, Washington, DC 20036, USA; Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa
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Schroeder L, Ackermann RR. Moving beyond the adaptationist paradigm for human evolution, and why it matters. J Hum Evol 2023; 174:103296. [PMID: 36527977 DOI: 10.1016/j.jhevol.2022.103296] [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: 04/25/2022] [Revised: 11/12/2022] [Accepted: 11/12/2022] [Indexed: 12/23/2022]
Abstract
The Journal of Human Evolution (JHE) was founded 50 years ago when much of the foundation for how we think about human evolution was in place or being put in place, providing the main framework for how we consider our origins today. Here, we will explore historical developments, including early JHE outputs, as they relate to our understanding of the relationship between phenotypic variation and evolutionary process, and use that as a springboard for considering our current understanding of these links as applied to human evolution. We will focus specifically on how the study of variation itself has shifted us away from taxonomic and adaptationist perspectives toward a richer understanding of the processes shaping human evolutionary history, using literature searches and specific test cases to highlight this. We argue that natural selection, gene exchange, genetic drift, and mutation should not be considered individually when considering the production of hominin diversity. In this context, we offer suggestions for future research directions and reflect on this more complex understanding of human evolution and its broader relevance to society. Finally, we end by considering authorship demographics and practices in the last 50 years within JHE and how a shift in these demographics has the potential to reshape the science of human evolution going forward.
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Affiliation(s)
- Lauren Schroeder
- Department of Anthropology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada; Human Evolution Research Institute, University of Cape Town, Rondebosch, 7701, South Africa.
| | - Rebecca Rogers Ackermann
- Human Evolution Research Institute, University of Cape Town, Rondebosch, 7701, South Africa; Department of Archaeology, University of Cape Town, Rondebosch, 7701, South Africa.
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Teeth, prenatal growth rates, and the evolution of human-like pregnancy in later Homo. Proc Natl Acad Sci U S A 2022; 119:e2200689119. [PMID: 36191229 PMCID: PMC9564099 DOI: 10.1073/pnas.2200689119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Evidence of how gestational parameters evolved is essential to understanding this fundamental stage of human life. Until now, these data seemed elusive given the skeletal bias of the fossil record. We demonstrate that dentition provides a window into the life of neonates. Teeth begin to form in utero and are intimately associated with gestational development. We measured the molar dentition for 608 catarrhine primates and collected data on prenatal growth rate (PGR) and endocranial volume (ECV) for 19 primate genera from the literature. We found that PGR and ECV are highly correlated (R2 = 0.93, P < 0.001). Additionally, we demonstrated that molar proportions are significantly correlated with PGR (P = 0.004) and log-transformed ECV (P = 0.001). From these correlations, we developed two methods for reconstructing PGR in the fossil record, one using ECV and one using molar proportions. Dental proportions reconstruct hominid ECV (R2 = 0.81, P < 0.001), a result that can be extrapolated to PGR. As teeth dominate fossil assemblages, our findings greatly expand our ability to investigate life history in the fossil record. Fossil ECVs and dental measurements from 13 hominid species both support significantly increasing PGR throughout the terminal Miocene and Plio-Pleistocene, reflecting known evolutionary changes. Together with pelvic and endocranial morphology, reconstructed PGRs indicate the need for increasing maternal energetics during pregnancy over the last 6 million years, reaching a human-like PGR (i.e., more similar to humans than to other extant apes) and ECV in later Homo less than 1 million years ago.
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