Why do we call different types of humans "a different race" instead of "a different species"

Actually, you are wrong. Weather a person is black, European or mixed they are apart of the same group but with just different variation like the bear example. However you clified a bear it is still a bear. To refer to an African or European person as two different species would be wrong, because it would mean they are of another group entirely when that is not the case. The way someone appear or their skin shade don't affect their clification as an Sapien.