Uh, no. Race exists in all species, it is a subdivision of that species, just like species is a subdivision of a genus. In dogs we call them breeds. Where the boundaries lie between races is somewhat arbitrary. Between these groups, physical and biological differences are the rule, not the exception. If it helps you to call them "ethnicities", go right ahead, because those differences are smaller but still exist.
This doesn't mean an individual is defined by his or her race, only that they tend toward different means than those of other races. Nor does it excuse discrimination under the law, or treating members of some races poorly simply because they're a member of that race.
This is scientific, biological reality. Even if all the races died except for one, in 50,000 years there would be multiple races again, provided different populations were allowed to separate entirely for a while.