It doesn't? Gee, a lot of horse farms will be interested to know that their horses ain't horses.
Since you credit the Chinese story of inter-primate breeding, should I believe you when you define two breeds of dogs as two species?
"It doesn't? Gee, a lot of horse farms will be interested to know that their horses ain't horses."
Don't be silly!
The distinction is, of course, that horses (with the possible exception of, say, Shetland ponies and Clysdales) can naturally breed, and would not have to rely on artificial reproduction, as would a Mastiff and a Taco Bell dog.
The scientific definition of a "species" is well known; it's not mine.
To take the issue to a less emotional topic than inter-primate breeding, Google "Liger" and see what you find.