Human-like enamel growth in Homo naledi

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Objectives: A modern pattern (rate and duration) of dental development occurs relatively recently during human evolution. Given the temporal overlap of Homo naledi with the first appearance of fossil Homo sapiens in Africa, this small-bodied and small-brained hominin presents an opportunity to elucidate the evolution of enamel growth in the hominin clade. Here we conduct the first histological study of two permanent mandibular canines and one permanent maxillary first molar, representing three individuals attributed to H. naledi. We reconstruct the rate and duration of enamel growth and compare these findings to those reported for other fossil hominins and recent humans. Materials and Methods: Thin sections of each tooth were produced using standard histological methods. Daily and longer period incremental markings were measured to reconstruct enamel secretion and extension rates, Retzius periodicity, canine crown and molar cusp formation time. Results: Daily enamel secretion rates overlapped with those from recent hominins. Canine crown formation time is similar to that observed in recent Europeans but is longer than canine formation times reported for most other hominins including Australopithecus and H. neanderthalensis. The extended period of canine formation appears to be due to a relatively tall enamel crown and a sustained slow rate of enamel extension in the cervical portion of the crown. A Retzius periodicity of 11 days for the canines, and nine days for the molar, in H. naledi parallel results found in recent humans. An 11-day periodicity has not been reported for Late Pleistocene Homo (H. erectus, H. neanderthalensis) and is rarely found in Australopithecus and Paranthropus species. Discussion: Enamel growth of H. naledi is most similar to recent humans though comparative data are limited for most fossil hominin species. The high Retzius periodicity values do not follow expectations for a small-brained hominin.

OriginalsprogEngelsk
Artikelnummere24893
TidsskriftAmerican journal of biological anthropology
Vol/bind184
Udgave nummer1
Antal sider14
ISSN2692-7691
DOI
StatusUdgivet - 2024

Bibliografisk note

Funding Information:
Funding for the excavation and recovery of the material was from the National Geographic Society and the Lyda Hill Foundation. Support for transportation of the specimens was from the Lee R Berger Foundation for Exploration. PM acknowledges support from The Royal Society and The Leverhulme Trust (grant numbers RG110435 and RPG‐2018‐226). The participation of MMS was supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 819960). PPM and EC are supported by the European Commission through the Marie S. Curie European Training Network ‘PUSHH’ (grant number 861389). AJT, LB, JH and EC are supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant number 101021361). The participation of MCO was supported by the ERC under the Horizon 2020‐MSCA‐IF‐2020 (grant agreement No. 101026776).

Publisher Copyright:
© 2024 The Authors. American Journal of Biological Anthropology published by Wiley Periodicals LLC.

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