There are many ancient secrets that are unknown to us. Many of them stay hidden until someone discovers them and presents them to world.
The same is true when we talk about africans living in ancient China. Many artifacts have been discovered in Gansu and Magao caves in China, showing that africans did actually exist in ancient China. So the best thing we can do is to keep an open mind, as there are many other things in our world that have yet to be discovered.