In my previous post, I suggested that a number of other species demonstrate many similar traits as humans, suggesting near human intelligence. These traits include the ability to use language, create tools, and interact in complex social hierarchies. Recently, elephants were added to the list of creatures thought to be able to recognize their reflections as an image of themselves, rather than another animal. Self-consciousness suggests an ability to have mental concepts, including an idea of a self. This has also been observed in chimpanzees, bonobos and orangutans, and humans (by two years of age).
Another recent discovery notes similar types of brain cells in humpback whales and humans, of a sort that may relate to intelligence. These types of cells are not found in dolphins, but are found in other primates.
One of the reasons many reject evolution is that they don't want to accept that humans are not special. These people like the idea, promoted by certain religions, that humans were a special creation of God, and that everything in the universe is essentially an elaborate stage. God's attention is focused on us and us alone. This notion has also gone farther, with certain ethnic and cultural groups believing that God does not even favor all humans equally, but gave special information to one tribe of people and no one else. This kind of elitism is betrayed for what it is, pride, when we objectively look at the world. There are many cultures, many religions, and there is beauty and worth in each of these religions, even if none is completely right about everything. Likewise, there are other creatures that differ from us by very little.
It is likely that humans could only achieve our current situation because, in addition to our intelligence, we walked upright, had hands that could make tools, and vocal cords that could make a great variety of sounds. And, as noted in other posts, it is very unlikely that we are the only planet in the universe with intelligent life.