In recent humans, the third root usually occurs on the mandibular first molar referred to as a 3RM1 but may also occur on the lower second and third molars; we refer to these collectively as 3RM 4 — 6. The 3RM may appear either unilaterally or bilaterally; the single twin study of which we are aware shows bilateral development in both twins, suggesting a genetic underpinning 7.
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The 3RM entered the clinical literature in 8 , being called radix entomolaris by Bolk 9 ; it was codified into the Arizona State University Dental Anthropology System in 2. The 3-rooted lower molar anomaly. Three-rooted lower first molar alveolar sockets showing distolingual position of accessory root and the 3-rooted lower first molar lingual view ; Inset 3-rooted lower second molar of Xiahe Denisovan individual lingual view. M, mesial; L, lingual; D, distal; B, buccal. The rarity of the 3RM in non-Asian H. Despite its high frequency in recent Asian-derived populations, the 3RM has not been reported in the earliest H.
Before the recent discoveries, the earliest example of a 3RM came from an H. The mandible, originally described by Macintosh et al. Given a lack of early evidence for 3RM, one explanation for its high frequency in Asia has been a relatively recent acquisition postdating the origin of H. Two recently described mandibles suggest a more ancient Asian origin for 3RM, and one that precedes H. The newly discovered individual from Xiahe, China—identified as Denisovan through paleoproteomics 1 —possesses a 3-rooted lower second molar 3RM2 Fig.
The recently described Penghu 1 mandible from Taiwan to 10 ka also exhibits a 3RM2 Although the authors suggest the 3RM2 differs from that described by Turner et al.
Like Xiahe, these exceptionally large molars are coupled with agenesis of the third molar For these reasons, Chen et al. Both mandibles show that the 3RM anomaly existed in archaic Asian hominins before H. These 2 recently reported fossils suggest that the 3RM 1 very likely originated in Asia and 2 evolved in a pre- sapiens population. Moreover, until a 3RM is found in more archaic hominins, it should be understood as a morphological trait that was transferred to H.
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Gene flow between H. Like the high-altitude related mutation, which is retained due to positive selection 21 , the retention of 3RM at high frequency in Asia may be related to selection for molar retention in populations with heavy masticatory loading Such selection also explains the lower frequency of 3RM in recent populations with higher Denisovan introgression e. Alternatively, 3RM frequencies may reflect an indirect influence resulting from selection on another trait under high selection, as has been suggested to be the case for incisor crown morphology and EDAR in North and East Asians and in the New World Whatever the cause, we argue that the 3RM anomaly is an example of a morphological character in recent humans that can be clearly traced to this archaic admixture.
The 3RM is an Asian-derived character that we can definitively trace to Denisovans. Thus, we now have very clear evidence that gene flow between archaic groups and H. There have been a number of Asian H. If the 3RM was transferred from archaic humans to H. The authors declare no conflict of interest. Published photographs 13 , 14 , however, show a small septum of the mesial root socket that may represent a bifurcated mesial root but no evidence of a lingual accessory root. The 3RM anomaly requires that the accessory root occurs between the mesial and distal root or as a lingual accessory of the distal root.
This article contains supporting information online at www. National Center for Biotechnology Information , U. Published online Jul 8. Shara E. Susan C. Author information Copyright and License information Disclaimer. Email: ude.
Human Evolution in China
Edited by James F. Published by PNAS. Keywords: Denisovan, introgression, dental anthropology, root morphology, Pleistocene Homo. Open in a separate window. Supplementary Material Supplementary File Click here to view. After a brief description of Chinese paleoanthropology all major Chinese sites are covered - and for the first time in one place. Original translations of Chinese-language materials and original analyses of a number of fossils are included.
The focus is on metric information for use in comparing the samples with fossils from other parts of the world.
Sections are organised as follows : 1 Fossil name and location of the site 2 how, when, and by whom found 3 detailed description 4 archaeological remains at the site 5 floral and faunal content of the site. The core of the book consists of the anatomical descriptions, which have been prepared by Wu, working from both the specimens themselves and reports published by other specialists.
Brief communication: Evidence of pathology on the frontal bone from Gongwangling
Western readers will be grateful to have access to material that has heretofore been hard to find. Here is a wealth of raw data essential for comparative purposes on China's rich hominoid and hominid fossil remains--including detailed morphological descriptions and metric data. This book is an essential tool. Visit Seller's Storefront. List this Seller's Books. Payment Methods accepted by seller. AbeBooks Bookseller Since: 20 September
Related Human Evolution in China: A Metric Description of Fossils and a Review of the Sites
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