response: It's common in various parts of Europe, as well as the US and parts of the Middle East.
original_response: Haha! Yeah, pink and green are a bit too crazy for me! If you don't mind me asking, is your wife European? I hear brown hair is pretty common there.
history: my wife has brown hair, it's so pretty i really love it Oh, that's nice. Your wife has the second-most common hair color for humans. Huh, I didn't know that. Where is brown hair common?
knowledge: 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.