It's pretty clear that we are not the only animals with brains, so there are other animals who use their brains to make decisions, such as how to hunt and when to sleep and so on. We make what is in our opinion more sophisticated decisions, but that arguably is a human-centric conceit. There are ant colonies that span continents, and they aren't building any nuclear weapons. Are we really sure we are more intelligent than them?
I don't think it is fair to say that our brain makes us more adaptable to new environments than other species. Compared to the many single-celled species that have survived hundreds of millions of years, the bacteria that can survive hibernation for millions of years, and our current inability to agree on the existence of global warming, is it realistic to project the survival of our species beyond even the next thousand years?
The brain is an instrument that allows a species to be more adaptable to new environments, of course there are other ways to achieve adaptability, being simple and generic is one of them. Being a symbiote/parasite of an adaptable species (like bacteria are of us) is another.
I think the battle between complex organisms and simple organisms is an ongoing one. At the moment we rely on the simple organisms on our insides to protect us against the simple organisms on the outside. If there is any threat to the survival of our species it lies there. A nuclear holocaust or a few degrees of global warming isn't going to do it, unless you define 'our species' as 'inhabitants of new york'.
Wether we are more intelligent that some other intelligent animals is dependent on how you measure intelligence. If you define it as having many offspring in many continents, I'm not sure ants would win, but I'm not sure humans would either.
What I feel makes us different from animals is not being able to adapt, as you pointed out (many animals exhibit learned behavior and conscious decision making), it's not even being self-conscious (it's been proven animals can be too), it's in my opinion the ability to observe and act on your own thought-streams.
And this is deeply linked to language, as language is a way to receive informations you don't already have and coerce your thoughts streams (or not) along them to make predictions that are not based on experience. In my opionion it is very important to make this distinction between predictions learned by experience and predictions learned by the books. I think we here can measure this difference very well.
To me it looks like this added layer of brain cells we have acts as an observer on life happening on the floor below, kind of a god of your own brain, acting not on experience-learned behaviour but solely on a combination of representation learned from others (connections created willfully from other's discourse) and abstractions made from adaptive learning done on signals coming from the layers below (I envision an isolated system whose only object of observation is regular thoughts and whose only sense is signals coming through connections to layers producing those thoughts).
It feel likes what makes us apart is first this simple fact we learn from our own though patterns. This enables us to make what (at least) feels like free decisions based on abstracted representation and not mere immediate experience. This enables us to think outside the box of our own experiences and form models of other's. This enables us to delibarately picture in our minds things that we have never experienced, or things that cannot be experienced (think abstract models in sciences). This finally enables us to accept information from our peers as valid signals to model our though-paths on. If this layer was anything real, to me it would mainly be an experience or information-sharing device. This thing that makes possible, and makes useful, the kind of social structure we know and live in.
I may be rehashing common knowledge, I don't know.
I don't think it is fair to say that our brain makes us more adaptable to new environments than other species. Compared to the many single-celled species that have survived hundreds of millions of years, the bacteria that can survive hibernation for millions of years, and our current inability to agree on the existence of global warming, is it realistic to project the survival of our species beyond even the next thousand years?