Abstract
Excavations at the Longtan Cave, Hexian, Anhui Province of Eastern China, have yielded several hominin fossils including crania, mandibular fragments, and teeth currently dated to 412±25 ka. While previous studies have focused on the cranial remains, there are no detailed analyses of the dental evidence. In this study, we provide metric and morphological descriptions and comparisons of ten teeth recovered from Hexian, including microcomputed tomography analyses. Our results indicate that the Hexian teeth are metrically and morphologically primitive and overlap with H. ergaster and East Asian Early and mid-Middle Pleistocene hominins in their large dimensions and occlusal complexities. However, the Hexian teeth differ from H. ergaster in features such as conspicuous vertical grooves on the labial/buccal surfaces of the central incisor and the upper premolar, the crown outline shapes of upper and lower molars and the numbers, shapes, and divergences of the roots. Despite their close geological ages, the Hexian teeth are also more primitive than Zhoukoudian specimens, and resemble Sangiran Early Pleistocene teeth. In addition, no typical Neanderthal features have been identified in the Hexian sample. Our study highlights the metrical and morphological primitive status of the Hexian sample in comparison to contemporaneous or even earlier populations of Asia. Based on this finding, we suggest that the primitive-derived gradients of the Asian hominins cannot be satisfactorily fitted along a chronological sequence, suggesting complex evolutionary scenarios with the coexistence and/or survival of different lineages in Eurasia. Hexian could represent the persistence in time of a H. erectus group that would have retained primitive features that were lost in other Asian populations such as Zhoukoudian or Panxian Dadong. Our study expands the metrical and morphological variations known for the East Asian hominins before the mid-Middle Pleistocene and warns about the possibility that the Asian hominin variability may have been taxonomically oversimplified.
Highlights
During the decades of the 1970s and the 1980s, surveys and excavations at the Longtan Cave, Anhui County, Eastern China, uncovered a nearly complete skullcap, a left partial mandibular corpus with two teeth in situ, and ten isolated teeth among some other fragmentary hominin fossils [1]
The Indonesian material is globally referred to as Early Pleistocene, in the discussion we will make some distinctions about the Pucangan and the Kabuh Formations if it is relevant for our interpretation
The metric and morphological features of ten Middle Pleistocene hominin teeth from Hexian, China, were described and compared with several hominin teeth recovered from Africa, Asia, and Europe
Summary
During the decades of the 1970s and the 1980s, surveys and excavations at the Longtan Cave, Anhui County, Eastern China, uncovered a nearly complete skullcap, a left partial mandibular corpus with two teeth in situ, and ten isolated teeth among some other fragmentary hominin fossils [1] Since their discovery, most of the studies have focused in the cranial elements [2,3,4,5,6,7,8,9,10] pointing to the expression of features that are classically considered typical of Asian H. erectus. From all these we can assume that, in geological terms, all the human fossils were accumulated in a relatively short period and have the same geo-chronological age
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