This is a hard questions since race is generally agreed on as a concept by historians. In other words, there is no such thing as biological race. Race is something that we as a society have created. Through out history, the idea of "race" has changed. It was not always about the color of skin. I will point out this video for a good introduction on the concept. For further reading.

For some history about the first meet between people who falls into the modern definition of race, maybe someone else can venture in...