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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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Brophy JK, Bolter DR, Elliott M, Hawks J, Berger LR. An examination of Homo naledi early juveniles recovered from the Rising Star cave system, South Africa. Ann Hum Biol 2024; 51:2321128. [PMID: 38509686 DOI: 10.1080/03014460.2024.2321128] [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: 12/10/2023] [Accepted: 02/06/2024] [Indexed: 03/22/2024]
Abstract
BACKGROUND Six Homo naledi early juveniles were recovered from U.W. 101 (Dinaledi Chamber), U.W. 102 (Lesedi Chamber), and U.W. 110 in the Rising Star cave system. AIM This paper develops the information for the H. naledi early juvenile life stage, as defined by a combination of deciduous and permanent dentition, and the eruption of the first permanent molar. SUBJECTS AND METHODS The growing number of young individuals recovered from the Rising Star cave system allows us to gain a better understanding of their variation, or lack thereof, and provides a basis to estimate broad ranges for age at death of the individuals. The individuals are identified and described through craniodental remains and spatial associations. RESULTS AND CONCLUSION Our results show that the teeth are remarkably consistent across the localities in their metric and non-metric traits, and our analyses refine previous estimations on dental eruptions with the first permanent molar erupting first in the sequence among permanent teeth.
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Affiliation(s)
- Juliet K Brophy
- Department of Geography and Anthropology, LA State University, Baton Rouge, LA, USA
- The Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
| | - Debra R Bolter
- The Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
- Department of Anthropology, Modesto Junior College, Modesto, CA, USA
- Department of Anthropology, CA State University Stanislaus, Turlock, CA, USA
| | - Marina Elliott
- The Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
- Department of Archaeology, Simon Fraser University, Burnaby, BC, Canada
| | - John Hawks
- The Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
- Department of Anthropology, University of WI-Madison, Madison, WI, USA
| | - Lee R Berger
- The Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
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