Brainy

The fact is that relative to our body size our brains are huge.
There has never been data to support the concept, however, that WITHIN the human species brain size reflects any aspect of "intelligence"; it just means the owner has a big head.
That being said, the size of our brain has allowed us to extend our functionality, especially in the areas of hand dexterity--think writing, painting, caressing--and speech. But I still think the major adaptation that allowed for all this was walking upright. Perhaps the poetic remark that we stand tall in order to reach the stars isn't too sappy? It may be true. But we couldn't reach the heights if we hadn't stood up in the first place....