You really lack an elementary understanding of biology.
Races and species are not the same thing. You want them to be, but they're not.
If you believe in evolution and go back a billion years or more on earth, most species did not exist. So yes you may be related to a lion if you go back far enough.
I know they are not the same. While certain species can breed with another for example lions and tigers or a male donkey and female horse, the offspring is almost always sterile.
The thing is races can interbreed yet they have developed separate and the diversity touted as a strength in the West is only possible because of distinct races. One mongrel society is not as diverse as three societies with different races each.
Garebear, you should know all about a homogeneous society given that you have lived in China. I have no problem with (and prefer) a world like that. Nigeria for Nigerians and China for Chinese. That's diversity!