The Edge of Evolution

I was watching C-span and I saw a talk by the author of a book called the Edge of Evolution. The argument that the book puts forth is that evolution does not explain a number of phenomena that can only be explained by a design theory. It was a little weird, but the author seemed to argue that, all of the mutations that were necessary to make a human starting with a single-celled organism are too improbable.

The problem with the reasoning that the author uses is that he never seemed to get the ideas that evolution is not purposeful and it is not necessary for every possible mutation to be exhausted before a viable mutation can occur. So his ideas are hinged upon the notion that there is only one correct evolutionary solution and that all other possible solutions were exhausted before the"correct" adaptation took place. If this were the case, I would imagine that it would be impossible for evolution to have brought about life on earth. However, with my limited understanding of biology and chemistry, this seems pretty stupid.