What is outside of our expectations in terms of the evolution of intelligence is based on a set of assumptions.
I wouldn't assume that the evolution higher intelligence is impossible. Just the right conditions can set off a whole raft of adaptions, each adding layers of processing power to the brain.
Our brain is no different in fundamental makeup, neural networks, etc, than other animals, what essentially sets us apart is a more developed prefrontal cortex.
Just look at how the senses of other animals far surpass our own in terms of sight, hearing, smell.....what a dog can do with its sense of smell is astounding. We went with reasoning power....
