For what it's worth I agree, but I can also see how it can get problematics. I don't know if I would agree that Vulcans are necessarily smarter than humans in Star Trek... their technology is more advanced, that's for certain, but nothing that is beyond humans' ability to understand or manipulate. Vulcans, and Gnomes, have the benefit of living longer life and have more chances to improve however.
You could argue: are gnomes naturally smarter than humans, or does their civilization simply values knowledge and technical skills more highly than humans and thus produces more technologically inclined people who then push the overall tech level of the civilization? In that case, the cultural component would explain the bump to INT.