Middle Pleistocene teeth add new data to hominin evolution in Asia
|Four hominin teeth (I1, C1, P3 and P3) recovered from the late Middle Pleistocene cave site of Panxian Dadong [Credit: LIU Wu]|
Panxian Dadong Cave (25°37’38’’N, 104°8’44’’E), is part of a large karst system that contains three connected stacked caves. In 1990, mammalian fossils and stone artifacts were first found in the cave. From 1992 to 2005, a collaborative international team of scientists headed by the IVPP conducted several seasons of excavations that yielded four hominin teeth and a lithic assemblage associated with an Ailuropoda-Stegodon fauna. Additional evidence of hominin activities in the cave consists of cut-marked and burnt bone. Faunal comparisons, Uranium-series dates of speleothems, and electron spin resonance dates on tooth enamel indicate that most of the excavated levels at Dadong were deposited between MIS 8 and MIS 6 (130-300 ka). Studies in the past twenty years confirm that Panxian Dadong contains an extensive record of late Middle Pleistocene human activities involving behavioral flexibility and unique adaptations to a mountainous environment.
In order to examine East Asian dental evolutionary trends, researchers compared the Panxian Dadong teeth with a range of Middle and Upper Pleistocene hominins of Africa, Asia and Europe, particularly with several Chinese samples from early Middle Pleistocene, late Middle Pleistocene, Upper Pleistocene, and more recent prehistoric and modern human collections.
|Views of enamel dentine junction (EDJ) of the lingual aspect of the I1 (a) and the occlusal and lingual aspect of the C1 (b and c) created from micro-CT scanning [Credit: LIU Wu]|
“This mosaic of primitive and derived traits gives a glimpse of the high morphological diversity of the prehistoric populations that inhabited the vast geographical region of East Asia and raises the possibility of new evolutionary trends that have yet to be fully understood. Upper Pleistocene fossils from Africa and Europe have been generally classified as H. sapiens or Homo neanderthalensis. However, comparatively little is known about the evolution of human populations in Asia and the question remains how to relate late Middle Pleistocene and Upper Pleistocene fossils from Asia to either H. sapiens, Neanderthals, or to something else unique to Asia”, said Dr. LIU Wu, lead author of the study, “This problem is not exclusive to the Panxian Dadong sample, as it is a common problem when analyzing the Middle Pleistocene dental record from Africa and Asia”.
“Although the Panxian Dadong teeth overlap in some morphological trends and in their dimensions with European Middle Pleistocene groups and the Neanderthals, they do not show any of the so-called typical Neanderthal traits nor any apomorphic feature that allow us to directly relate them to H. sapiens. However, our analysis reveals that the Panxian Dadong fossils are generally more derived than the Pleistocene fossils from North Africa, including the roughly contemporaneous C1 from Jebel Irhoud”, said coauthor Dr. María Martinón-Torres, Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Burgos, Spain.
|Geographic location and view of the entrance to Panxian Dadong [Credit: LIU Wu]|
“We believe that the key to understanding the evolutionary fate of the Middle Pleistocene populations from Africa and Asia will derive from future fossil discoveries and more precise chronologies that help build a comparable fossil record and chronological framework between the continents. In the meantime, it is necessary to further investigate the polarity of morphological features present in the Middle Pleistocene groups and to identify Neanderthal and/or H. sapiens apomorphic traits”, said coauthor Dr. Erik Trinkaus, Department of Anthropology, Washington University, Saint Louis, “This study highlights the necessity of incorporating this new Asian evidence into the scientific debate about human evolution and the development of dental diversity in Homo lineages”.
This work was supported by the Chinese Academy of Sciences, the National Natural Science Foundation of China, the US National Science Foundation, the Henry Luce Foundation, the Wenner-Gren Foundation, the L.S.B. Leakey Foundation, the National Geographic Society, the Charles P. Taft Fund of the University of Cincinnati, the University of Cincinnati University Research Council, and the California State University, Stanislaus.
Source: Institute of Vertebrate Paleontology and Paleoanthropology [March 14, 2013]