Are there (according to science) different human races? Disclaimer: 
I have no intention to receive answers which justify racism or a hierarchy of races.
All people are worth the same.
I am not a native english speaker.

Question:
Is there scientific proof of different human races? If not, what is the difference between, for example Asian and African people called? 
Is it correct to compare human distinctions with animal distinctions (i.e. Dogs —&gt; Labrador vs. Shepherd)?

I am looking forward to a fact based discussion. 