Han et al. (2014). Ancient DNA provides new insight into the maternal lineages and domestication of Chinese donkeys BMC Evolutionary Biology 2014, 14:246 http://www.biomedcentral.com/1471-2148/14/246
Han et al (2014) in a study of Chinese donkeys found that the Chinese donkeys are descendant from the Nubian wild ass (Equus africanus africanus) . They believe these donkeys were in China before the Han empire.
The researchers noted that the: “ First, Chinese historical records state that 4000 years ago, the donkey was a treasure that was rare and only found in the aristocratic and imperial palaces”. This is an interesting finding because I have shown elsewhere that the Kushites from Nubia: Mande and Dravidian speakers founded the first civilizations of China: Xia and Shang respectively. This finding offers further support to the Kushite origin of the Xia and Shang.
You can find out more about the Blacks of Xia and Shang in my book: