Explain how race is both a reality and a myth.?

In a nutshell: The myth is that human beings of different color vary greatly from human beings of a different color. This has been believed since the beginning of history and was so obvious that it was never questioned. Science finally disproved the myth and it's now a fact that we're pretty much all the same. The reality is that thousands of years passed in which the myth was firmly believed as a fact. The world was run and structured by people who firmly believed the myth was true. Today's society is still, if not dominated, at least based on that same system which was built by the myth.