Study Of Uranium-series Dating Of Late Homo Sapiens Sites In Yunnan

For the past more than 20 years, the origin, dispersal and evolution of modern Homo sapiens have been one of the subjects of an intensive debate between the exponents of two competing hypotheses, "regional continuity" versus "recent out of Africa". Establishing a reliable chronological framework is essential to this study.Xianren Cave is located ca. 300 m southeast to the town of Xichou County, Yunnan Province. From the deposits inside the cavern, 5 hominid teeth together with an abundance of mammalian fossils representing 33 species have been recovered. 4 fossil teeth samples are selected from the museum collection. Judging by the adhered matrix deposits, 3 of them (XRD-1, 2, 3) should come from the Middle Layer, from which the hominid teeth were believed to come, while another one (XRD-4) may come from the Upper Layer. 230Th / 234U dating is carried out on all the 4 samples, yielding results in the range of 47 and 105 ka B.P.. Independent 227Th / 230Th determinations on XRD-2 and 4 give results consistent within errors with those from 230Th / 234U. It seems thus plausible to attribute the hominid teeth in a range of 47-105ka B.P..Longtanshan No. 1 Cave is located in the south of Chenggong County, Yunnan Province. Systematic excavation since 1977 have led to the discovery of 2 hominid teeth assigned to late Homo sapiens, mammalian fossils representing 12 species. The 230Th / 234U dating has been carried out on 5 intercalated calcite samples and 3 fossil ones. The results from calcite samples are much too old to be compatible with the biostratigraphy, indicating an urgent need to re-study the complicated stratigraphic sequences. The fossil samples provide an age range between 60 and 79 ka B.P., which may represent the chronology of the hominid teeth. However, compared with the well established U-series dating of speleothem calcites, the U-series dates on fossil materials tend to be much younger. So it is highly possible for the above dates of the two localities to be underestimated.Based on the U-series dating of intercalated speleothem formations, the chronology of several hominid sites in Yunnan, including the locality of Lijiang hominid, have been studied. The results show that these sites are much older than the previously estimated age of 40 ka B.P.. Taking into account the dating results on other sites having been studied previously in Guangxi Zhuang Autonomous Region and Jiangsu Province, the appearance of modern H. sapiens in China may be an event as early as in West Asia and South Africa.