Most people do not really think to ask this question about Evolution. However, it has become quite the important question in determining the validity of the paradigm. In this post when I refer to "evolution" I am referring to macroevolution (see my post "Useful or Useless Evolutionary Terms"). If I am talking about microevolution, I will make the distinction.As I discussed in the previously cited post, random mutation does happen, and natural selection does operate on those mutations. This observation has been extrapolated over time into the theory of Evolution. According to the paradigm, life began as a single-cell organism, and through the process noted, we arrive at the state of life today (complex, mega-multicellular organisms).