Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China.
Institute of Global Environmental Change, Xi'an Jiaotong University, 710049, Xi'an, China.
J Hum Evol. 2023 Sep;182:103411. doi: 10.1016/j.jhevol.2023.103411. Epub 2023 Jul 31.
Excavations in Hualongdong (HLD), East China, have yielded abundant hominin fossils dated to 300 ka. There is a nearly complete mandible that fits well with a partial cranium, and together they compose the skull labeled as HLD 6. Thus far, detailed morphological description and comparisons of the mandible have not been conducted. Here we present a comprehensive morphological, metric, and geometric morphometric assessment of this mandible and compare it with both adult and immature specimens of Pleistocene hominins and recent modern humans. Results indicate that the HLD 6 mandible exhibits a mosaic morphological pattern characterized by a robust corpus and relatively gracile symphysis and ramus. The moderately developed mental trigone and a clear anterior mandibular incurvation of the HLD 6 mandible are reminiscent of Late Pleistocene hominin and recent modern human morphology. However, the weak expression of all these features indicates that this mandible does not possess a true chin. Moreover, a suite of archaic features that resemble those of Middle Pleistocene hominins includes pronounced alveolar planum, superior transverse torus, thick corpus, a pronounced endocondyloid crest, and a well-developed medial pterygoid tubercle. The geometric morphometric analysis further confirms the mosaic pattern of the HLD 6 mandible. The combination of both archaic and modern human features identified in the HLD 6 mandible is unexpected, given its late Middle Pleistocene age and differs from approximately contemporaneous Homo members such as Xujiayao, Penghu, and Xiahe. This mosaic pattern has never been recorded in late Middle Pleistocene hominin fossil assemblages in East Asia. The HLD 6 mandible provides further support for the high morphological diversity during late Middle Pleistocene hominin evolution. With these findings, it is possible that modern human morphologies are present as early as 300 ka and earlier than the emergence of modern humans in East Asia.
在中国华东的华龙洞（HLD）发掘出了大量距今约 30 万年的人类化石。其中有一个近乎完整的下颌骨，与部分颅骨非常吻合，它们共同构成了被标记为 HLD6 的头骨。到目前为止，还没有对这块下颌骨进行详细的形态描述和比较。在这里，我们对这块下颌骨进行了全面的形态、测量和几何形态测量评估，并将其与更新世人类和现代人类的成年和未成年标本进行了比较。结果表明，HLD6 下颌骨表现出一种镶嵌形态模式，具有粗壮的体部和相对纤细的联合部和支部。HLD6 下颌骨中度发达的颏三角和明显的前下颌骨弯曲类似于晚更新世人类和现代人类的形态。然而，所有这些特征的微弱表达表明，这块下颌骨没有真正的颏部。此外，一系列类似于中更新世人类的古老特征包括明显的牙槽嵴平面、上横向嵴、厚实的体部、明显的内髁突嵴和发达的内侧翼状突结节。几何形态测量分析进一步证实了 HLD6 下颌骨的镶嵌形态模式。HLD6 下颌骨中既有古老的特征又有现代人类的特征，这是出乎意料的，因为它的年代属于中更新世晚期，与同期的许家窑、澎湖、和下河等人类成员不同。这种镶嵌模式在东亚中更新世晚期人类化石组合中从未有过记录。HLD6 下颌骨为中更新世晚期人类进化过程中存在高度形态多样性提供了进一步的支持。有了这些发现，现代人类的形态可能早在 30 万年前就已经存在，比现代人类在东亚的出现还要早。
