That's testable. Splice the human gene in to the chimpanzee genome and see if the outcome is the talking chimpanzee. If not then there are more genes active.
It's a fascinating idea, especially what would their language (syntax) be like if they didn't have the concepts (semantics). Or would it turn out that they do have enough in the way of concepts, and have only lacked the language to express it? Or does syntax play a greater role in intelligence than we'd thought - not fully whorf-sapir, but perhaps there is some contribution, in the way that going from regular to context-free languages makes a difference? (personally, I think most of the power of our language comes from a huge vocabulary and combining it in regular ways; the CFG aspect doesn't seem so to be so profound in practice to me)
There's this weird thing though, we don't seem to have much in terms of 'intermediately intelligent' creatures. It seems to be an all-or-nothing thing, you can't be for instance smart enough to develop a 50,000 word vocabulary and write a thesis if you can not also speak, or at least have a speech center (no insult intended to deaf people).
It's hard to generalize from a single instance, but you may have something there. It is striking that both means of expressing large numbers of ideas - vocabulary and syntax - only occur in us. I would guess that they were driven by the same evolutionary pressures and benefits.
There was an article about a (potentially) intermediate "proto-syntax" language used by an animal. Even since your comment, I've been wracking my brains for what it was. I can't even recall what type of animal it was... ah, now that you prompt me to put it into words :), I can google "proto-syntax": http://www.sciencedaily.com/releases/2009/12/091212144710.ht...
