Thanks! That's essentially what I was looking for. From what I understand the only good definition of "better" in an evolutionary system would be "more able to survive in its given environment." For intelligence though, I was thinking along the lines of "Better able to (intentionally?) manipulate its given environment to a wider range of purposes." Though, this is of course an extremely rough definition. The mad scientist in me was just (implausibly) dreaming of a way to breed 'smarter' companions from socially intelligent species of the kind we usually keep as pets (dogs, cats, [other] primates). I'd read about the domestication of the wild Silver Fox and was wondering if a similar experiment might be run for intelligence, instead of 'kindness'. As you said, though, there's likely to be (currently) insurmountable barriers, given the relative complexity of intelligence vs a single behavioral trait.