The study of human evolution is an ongoing journey, with new discoveries continually reshaping our understanding of the past. For many years, the debate surrounding the origin of anatomically modern humans (AMHS) has focused largely on the fossil evidence from Africa and Europe. However, East Asia, which has long been a site of significant hominin discoveries, has often been overlooked in these discussions. Despite the relatively large number of late Middle Pleistocene hominin fossils found in East Asia, their role in the broader narrative of human evolution, particularly in relation to contemporary hominins from Africa and Europe, has not been fully explored. Recent work by Dr. Liu Wu, of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences, along with his international collaborators, aims to address this gap by providing a detailed analysis of four hominin teeth recovered from the late Middle Pleistocene Panxian Dadong cave site in Guizhou, southwestern China.
The Panxian Dadong teeth, which are dated to the Middle Pleistocene period (approximately 130,000 to 300,000 years ago), present a unique opportunity to examine the evolutionary trajectory of hominins in East Asia during this critical period. These teeth, consisting of the first and second incisors (I1), canine (C1), and two premolars (P3), exhibit a combination of archaic and derived traits that offer new insights into the debate over the origins and phylogenetic relationships of early human populations in Asia. The study, published online on March 4, 2013, in the Journal of Human Evolution, sheds light on the morphological diversity of the prehistoric populations that once inhabited East Asia and how these traits compare to those of hominins from Africa and Europe.
The Panxian Dadong Cave, located at 25°37’38” N and 104°8’44” E, is part of a larger karst system in the region. The cave has yielded numerous mammalian fossils, stone tools, and evidence of hominin activities over the past several decades. Excavations conducted between 1992 and 2005 by a collaborative team of scientists from China and other countries resulted in the discovery of four hominin teeth and a lithic assemblage associated with a fauna that included species such as the giant panda (Ailuropoda) and Stegodon. The faunal and lithic evidence suggests that hominins were present at the site during the late Middle Pleistocene, and the surrounding cave sediments, dated using Uranium-series and electron spin resonance techniques, support the conclusion that the deposits were formed between marine isotope stages 8 and 6 (130-300 ka). This timeframe places the Panxian Dadong fossils in a critical period of human evolution, during which the ancestors of modern humans were undergoing significant changes.
The researchers compared the Panxian Dadong teeth to other hominin fossils from Africa, Asia, and Europe, focusing on those from the Middle and Upper Pleistocene periods. In particular, they examined samples from China, which provided insights into the dental evolution of East Asian hominins. The Panxian Dadong teeth displayed both archaic and derived features, offering a glimpse into the complex evolutionary processes at play in East Asia during this time. For example, the first incisor (I1) exhibited robust features, including a pronounced tuberculum dentale, a structure often associated with archaic hominins such as Homo erectus from the mid-Middle Pleistocene. However, these features were somewhat less complex than those observed in H. erectus fossils from China, suggesting that the Panxian Dadong individuals were more advanced than their predecessors.
The second tooth, a canine (C1), was found to be robust and symmetrical in shape, without the cingulum (a raised ridge of enamel) that is often seen in other hominin species. The morphology of the canine, however, was consistent with the characteristics of later hominins from East Asia, indicating that the Panxian Dadong population was not a direct ancestor of modern humans but likely shared a common ancestry with them. The premolars (P3) exhibited a mix of traits, with the morphology of one of the premolars displaying more derived features similar to those found in early modern humans from Europe and West Asia, including Homo sapiens and Neanderthals. These derived traits were particularly evident in the shape and size of the teeth, suggesting that the Panxian Dadong population may have had closer evolutionary ties to the early modern human populations of West Asia than to the archaic hominins of East Asia.
In addition to the individual features of the teeth, the researchers noted that the Panxian Dadong teeth presented a mosaic of primitive and derived characteristics, a pattern commonly observed in other Middle Pleistocene hominins. This mosaic of traits provides important information about the evolutionary trends in East Asia and raises the possibility of new evolutionary trajectories that have yet to be fully understood. The study suggests that the late Middle Pleistocene hominin populations of East Asia may have experienced different evolutionary pressures compared to those of Africa and Europe, which could explain the unique dental traits seen in the Panxian Dadong fossils.
Dr. Liu Wu, the lead author of the study, emphasized that the Panxian Dadong teeth contribute to the ongoing debate about the origin of modern humans. While the Panxian Dadong fossils share some morphological similarities with European Middle Pleistocene groups and Neanderthals, they do not exhibit the distinctive Neanderthal traits or the clear markers of Homo sapiens. This finding raises important questions about the relationship between the hominin populations of East Asia, Africa, and Europe. The Panxian Dadong fossils do not directly align with either Neanderthals or early Homo sapiens, but rather represent a unique population with traits that suggest an evolutionary path distinct from the better-known hominins of Europe and Africa.
The study also highlights the need for further research on the Middle Pleistocene hominin populations of Africa and Asia. Dr. María Martinón-Torres, a coauthor of the study from the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) in Spain, noted that the Panxian Dadong fossils are more derived than the contemporaneous fossils from North Africa, such as the C1 tooth from Jebel Irhoud. However, she cautioned that the phylogenetic position of Middle Pleistocene fossils from Africa remains unclear, in part due to the scarcity of fossils from this period and region. These gaps in the fossil record make it difficult to determine whether the hominins of East Asia belong to the same lineage as H. sapiens, Neanderthals, or a distinct hominin group that evolved independently in the region.
Dr. Lynne A. Schepartz, from the University of the Witwatersrand in South Africa, also pointed out that the differences between the African and Asian Middle Pleistocene fossil assemblages could indicate distinct evolutionary trends for the populations on each continent. The fossil evidence from East Asia, including the Panxian Dadong teeth, suggests that the region may have harbored a unique evolutionary path, possibly involving an isolated population of Homo erectus or even a distinct hominin lineage. However, Dr. Schepartz noted that the current data do not provide definitive answers to these questions, and future fossil discoveries and improved chronological frameworks will be necessary to better understand the relationships between these populations.
Dr. Erik Trinkaus, a coauthor from Washington University in Saint Louis, emphasized the importance of integrating the Panxian Dadong fossils into the broader discussion of human evolution. He argued that the study of these fossils underscores the need to investigate the morphological features present in the Middle Pleistocene groups, particularly in Asia, in order to identify traits that may be characteristic of Neanderthals, H. sapiens, or other hominin groups. As new fossil discoveries are made and as more precise dating techniques are applied to existing specimens, it will be possible to build a more comprehensive understanding of the evolutionary history of hominins in Asia and their relationship to other populations across the globe.
The findings from the Panxian Dadong site contribute significantly to the understanding of human evolutionary history. The mosaic of archaic and derived traits in the Panxian Dadong teeth provides evidence of the complex and diverse nature of hominin populations in East Asia during the late Middle Pleistocene. While these fossils do not align directly with either Neanderthals or early H. sapiens, they offer important insights into the evolutionary processes at work in Asia and the potential for unique evolutionary paths in this region. Further research, including new fossil discoveries and more refined chronologies, will help to clarify the position of East Asian hominins in the broader narrative of human evolution and their relationship to contemporary populations in Africa and Europe.
More information: dx.doi.org/10.1016/j.jhevol.2012.10.012