It would if the size was constant but what you do in your life actually affects it. Then there's cases like Einstein with a smaller than average brain. So the hardware metrics aren't everything.

Idk man, I'm not convinced. Maybe we can pool money to coerce a Jap to adopt a black so we can settle it once and for all lol. There might be a 'half breed raised in Japan' study though but I guess that wouldn't be conclusive anyways unless you can compare it to the same kind of half-breed but raised in America.