I'm not sure of where the concentration is highest although brown hair is common in places like Central and Eastern Europe and the US.
Brown hair most common in Europe and the US, so maybe that's a possibility.
I have brown hair, but it's pretty light. So light that sometimes under the right lighting it looks blond! The thing is that brown hair does vary from being light brown to an almost black brown. But what causes a person's hair to change? I know age is a factor but I sort of wish to have a different hair color already, Apparently melanin levels vary over time, causing the hair color change. Ok, guess I'll have to hope my melanin changes early. Another thing I worry about is my light skin pigmentation. What is the worry, is it that you can be called white or fair? No more so that I'll have trouble getting a tan. Another thing is that do you know where most people with brown hair lives?
Brown hair is common among populations in the Western world, especially among those from Central Europe, Southeastern Europe, Eastern Europe, Southern Europe, Southern Cone, the United States, and also some populations in the Greater Middle East where it transitions smoothly into black hair.