I am pretty sure nobody would deny that some dogs are more intelligent than others, or more loving, or more hostile.
However, humans don't breed like that. We looked for specific traits in dogs, and bred them to intensify them. Often, intelligence was a factor. For some things, a smart dog was great, for other things a smart dog was not great. So, you get what amounts to huge families of dogs. One family is going to be a little smarter, one family is going to be a little more hostile, one family is going to be a little faster, one is going to be taller, etc.
I am sure if we started breeding people like that, we'd end up with the same types of differences. We'd end up with people with exaggerated traits. Human breeding has always been more or less random, so I don't believe for a minute that there are significant mental or athletic differences between the "races" at all.
Anyway, I find the concept of race to be outmoded, for reasons stated here. What does it mean to be "black" exactly? What does it mean to be "white?" If you can't think of the answer, then isn't worth considering that these concepts are meaningless outside of the pure aesthetic values of them? I only use the concept of race when I am describing a person, simply because it's the most obvious feature anyone has. In a description, skin tone is the first thing I mention. It's like the background.