Heh, since I'm in an auto shop waiting for my car to be worked on, I'll respond to a few points.
Scientific Theory: In science, a theory is an explanatory model. Nothing more, nothing less. No amount of verification will cause it to become anything else. A law is a generalized observation. The use of the word "theory" by creationists as if it had some sort of stigma is misinformed at best, disingenuous at worst. Other successful theories such as the germ theory of disease are supported by a mountain of evidence and entire industries are built around it, but nobody turns around an attempts to discredit them by calling them mere "theories".
The Decent of Humanity, as I understand it: The answer to why humans, or at least the homo genus, are unique in their intellectual capacity(let's ignore dolphins. even though they may be highly intelligent, it's not in the same way as ours) takes consideration into what else makes humanity unique. As primates, our fundamental feature is the opposable thumb. This trait allows the grabbing and manipulation of objects, be they sticks, rocks, or food. Now, to fully take advantage of this, one would need the proper brain capacity to coordinate. This presents itself as a selective pressure for higher intelligence because populations of primates that have higher intelligence will have a significant advantage due to already having the ability to use it. Chimpanzees are already fairly smart as animals go, and also fairly social. A dog, for example, won't see much benefit in obtaining greater ability to manipulate. All it has are paws. Now, with primates in general, there's a big catch: all four limbs are equal. The same limbs must be used for both manipulation and movement, meaning that what a primate can physically do is rather limited. They can sit down and do stuff, or they can scurry around... but not really both.
Now we come to the fundamental trait of the human family tree: walking upright. Our four limbs are not equal, they are specialized. Hind limbs are now primarily used for movement(our feet are vestigial hands, after all), and fore limbs are now free to do anything under almost any physical state. Active hunting with weapons/tools is now a possibility among many others. Advancements in intelligence now readily present advantages when they didn't before. The only way to go was up. Now, I'll get a little more speculative since I've only read a little on the subject... but I believe around 20,000 years ago the life span of humans got a big boost. The presence of elderly people in a tribe is possibly what elevated our social network to the point of civilization. Now, I really can't say whether or not that's the case, but it make sense.
