The wisdom of crowds

It is incredible to me that a group of people can find the answer to a nearly impossible question, without consulting each other, and simply by averaging their reponses. Its like this, if you ask a group of people to run 100km, their average time will not be faster than those of the fastest runners, it will be quite mediocre in fact. But if you ask a group of people to solve a problem, the solution they come up with, when you average the aggregate of their responses, will be (normally) far more accurate than the response of the smartest person in the group. Its amazing to me, but I'm just one guy, not a hyper-intelligent group of people.