I agree there's genetic influence in how we talk. I for example know a few unconnected(they dont know each other) East Asians who were adopted by rural mid western familes, grew up there their whole lives, and yet they still have distinct "Asia" sounds to their voices. They sound like Asains who grow up in America with Asain parents. Same is true for Africans. I knowAfricans adopted by white families who have distinct "black" voices.