Why is it that when they find some tribe of people stuck in the neolithic age, they are never Caucasian?

I would like to add that I am a non-racist, however this is a question I have been pondering for a long time. What is the explanaition? Did whites advance faster due to their location on the planet? I would think that temperate climates would necesitate more innovation simply because of the cold; in temperate climates is is also more difficult to ride out the winters without certain innovations in food preservation and heat/shelter. I am aware that geneticly we are all virtually the same so the explaination must lay in the location of origin of the races. I am also aware of the theory that we all originated from Africa and that those that left became whiter and smarter through evolution. I don't know about that. Tell me what you think.