Three Puzzles of the Dominant Yinping Tone in Mandarin Onomatopoeias

： Yinping tone is dominant in Mandarin onomatopoeias and there are three puzzles behind it: (a) Does this tonal distribution pattern exist since ancient or is it caused by diachronic evolution? (b) If this tonal distribution is caused by diachronic evolution, then what is the process of the diachronic evolution? (c) What is the restrictive mechanism behind this pattern of tonal distribution? First, this article examines the tonal distribution pattern, diachronic evolution of syllable size and structure type from five historical periods: from the Western Zhou Dynasty to the Spring and Autumn Period, the Tang Dynasty, the Yuan Dynasty, the middle Qing Dynasty and the contemporary China. Second, it tries to provide the key that unlocks the three puzzles one by one. Finally, four conclusions related to the subject are presented.