That is one conclusion one can reach, but your evidence is not true. You assert that other species haven't changed (they have) and repeat that humans are in some way different. Yes, we are--it improved our survival as a species to have a bigger brain along with manipulating hands, social relationships, language, and so on. That makes us unique, but it is in no way unnatural.Proto-man was just one of many animal species fighting for survival over the millennia. If his brain could evolve through processes of natural selection, then why did the brains of other creatures not similarly evolve - at least a little? The fact is that the brains of other creatures have remained practically the same size while man’s has “evolved”. This is inconsistent, and it will be recalled that the hallmark of the objective universe - and deistic proof of God - is its consistency. By the law of averages - which applies to natural selection as much as to anything else - there should have been at least some species other than man evolving in intelligence at least partway to the human level. There is none.
By the laws of nature that we have observed over time, by all accounts another species should have developed at least a brain remotely close to ours. And none have, for the most part every single surviving creature has remained exactly the same except us.
So what has taken place?
We are left with the explanation: Deliberate Cause
And this implies an isolate intelligence working through our physical being (brain / body)
As for the argument that no other brains are like ours: nonsense. The other great apes also have brains larger and more complicated than most other animals, and are significantly more intelligent than most other similarly-sized mammals. Dolphins and other cetaceans have brains as big as or larger than, and at least as complex as, human brains--and they show considerable signs of intelligence and language use. Elephants and their now-extinct relatives also have (and had) large, complex brains and apparently use language.
While there is debate about the measurements, etc., (and even moreso the relevance and meaning) in biology it's well established that brains of vertebrates have generally increased in size over time, especially among larger body sizes in the mammals.
Your assertion that "by all accounts another species should have developed," is incorrect. By what "accounts," exactly, do you base this assertion on? There is no imperative in evolution that implies any species "should" have a large brain, or appendages that can manipulate things, or so on. That we humans do is a lovely accident of evolution--our ancestors survived because they had those traits, and we inherited them. We appear to be the only line of species SO FAR on earth that combine these traits--but that in itself does not mean we "should" have them, or that any other species "should" develop them. Nature shows us there are lots of ways for living creatures to survive; we're just lucky to have the traits we do.