John, in that sense evolution is as solidly established as the "theory" of gravity. About which, at the lowest level, we don't know either. As Newton put it, hypotheses non fingo. Some questions just have to be left until we have more information.

Evolutionary biologists do not recognise a difference between adaptation and evolution. Indeed, "species" is nowadays seen as merely a convenient label for organisms that are more like each other (increasingly based on DNA content) than they are like other organisms. It is worth noting that groupings of species based on similariries of structure have been overwhelmingly confirmed by DNA analysis, and interesting and instructive when surprises have turned up.