Malocclusions in Xia Dynasty in China

Background The prevalence of malocclusion in modern population is higher than that in the excavated samples from the ancient times.Presently,the prevalence of juvenile malocclusion in the early stage of permanent teeth is as high as 72.92% in China.This study aimed to observe and evaluate the prevalence and severity of malocclusions in a sample of Xia Dynasty in China,and to compare these findings with the modern Chinese population.Methods The material consisted of 38 male and 18 female protohistoric skulls of Xia Dynasty 4000 years ago.Of 86 dental arches,29 cases had the jaw relationships.Tooth crowding,diastema,individual tooth malposition and malocclusion were studied.Results Of the samples,23.3% showed tooth alignment problems including crowding （8.1%）,diastema （9.3%）,and individual tooth malposition （5.8%）.The prevalence of malocclusion was 27.6%,mainly presented as Angle Class Ⅰ.Conclusions It is indicated that over thousands of years from Neolithic Age （6000-7000 years ago） to Xia Dynasty （4000 years ago）,the prevalence of malocclusion did not change significantly.The prevalence of malocclusion of Xia Dynasty samples was much lower than that of modern population.

Multiple evidences indicate no relationship between prehistoric disasters in Lajia site and outburst flood in upper Yellow River valley, China

All around the world, ancient legends exist about the Great Flood, and the influence of the Great Flood in human evolutionary history is a hotly debated topic. In China, the legend of the prehistoric Great Flood and Yu the Great's flood control has a long history and is considered to be closely linked to the establishment of the Xia Dynasty. However, there is a lack of solid scientific evidence. Against this issue, some scholars have proposed that an earthquake around 1920 BCE in the Guanting Basin along the upper reaches of the Yellow River led to the creation of a lake by damming in the Jishi Gorge and that the outburst of water from that lake led to the massive flood in the Yellow River region. These studies provided new scientific evidence for the Chinese legend. In this paper, we date skeletal samples embedded in earthquake sand blasting from the Lajia site, analyze remains from natural disasters(such as earthquakes and floods) and also archaeological remains. In addition, we compared the skeletal samples dating with that of sediments from the dammed-up lake. Our results are inconsistent with those of previous scholars. The earthquake at the Lajia site occurred no earlier than 1800 BCE, and the dammed-up lake in Jishi Gorge had disappeared by 3600 BCE. Thus, the formation and outburst of the dammed lake, the sudden death of ancient humans at the Lajia site and the ancient earthquake were independent events occurring at different times. In addition, the massive flood in the upper reaches of the Yellow River did not actually happen. Thus, we argue against and invalidate the hypothesis that the massive flood was related to Yu the Great's flood control and the establishment of the Xia Dynasty.