I'm familiar with that study actually, I'd forgotten about it. There has only been shown to be a tenuous link between brain size and IQ - but setting that aside, say for the sake of argument there's a strong correllation, that's still missing the point entirely.

Higher IQ's will propogate where having a high IQ is advantageous. If you look at the racial history of America that possibly applied less to blacks at some point, since starting a business, going to college etc was not an option. It doesn't now - so if you can establish a lower average IQ in blacks it means absolutely nothing except that it references a historical reproductive pattern - that gap will close where a higher IQ becomes reproductively attractive. And there are numerous studies to the effect that this gap has been closing for decades. That all makes IQ nothing inherent to race - stupid people have stupid kids in every race, as far as I'm aware.