One cannot talk about the mechanisms and functions and structure and chemistry of DNA without at some point thinking about how it all came to be in the first place. The whys and hows of it now were the whys and hows of it when it first came together. It is assumed at this time that evolution just had things "fall into place" over an almost umlimited time period. While it MAY have happened a long time ago, the assumption that it was basically an accident of chemistry and lightning and conditions is only in itself a speculation, though it is promulgated as fact to the lay public.