Hello John Sullivan,
My thesis is as follows: the common nature of these aspects of life on a molecular level is very strong evidence that they only originated once & evolved as life did. We do not see the existence of entirely dissimilar genetic or metabolic systems that would illustrate entirely separate origins.
Do a search on "RNA World" ... it appears the best explanation to date is that RNA evolved chemically and out-competed other systems for self-replicating molecules, but then DNA evolved chemically and took over.
Some old threads of mine on this topic are
Panspermic Pre-Biotic Molecules - Life's Building Blocks (Part I) and
Self-Replicating Molecules - Life's Building Blocks (Part II) -- they are both old and there has likely been much discovered since.
... as proof of ...
Do you prove theories in chemistry? I know it works in math, but generally in science it seems we develop theories as the best known explanations rather than prove them.
Can we ever prove that life evolved chemically from molecules or are we limited to developing the best explanation based on the evidence we know and the known behavior of chemicals?
Enjoy