Torri,
Darwinian evolution by natural selection is really an application of a broader principle to the particular field of biology; in the simpler world of organic chemistry the insatiable bonding appetite of carbon and oxygen in particular sees simpler short chain carbon compounds being absorbed over time into longer chain compounds of greater complexity. These precursor compounds leave no rock-bound fossils for us to study so it is harder for us to reconstruct the ancient pathways that led to the formation of DNA. But DNA is so extraordinarily complex, a landmark in the evolution of complexity on this planet, that there is no way it could have just appeared spontaneously out of nowhere. Figuring out those pathways is the stuff of abiogenesis. One precursor compound, RNA, is still with us, and is involved in gene expression within every cell of your body, and some believe that before DNA there was an 'RNA World' supporting simpler forms of pre life but incapable of the range of function that comes with DNA. We have created self replicating RNA in the lab now, so this is not just science fiction. Here's an article on RNA
https://www.ncbi.nlm.nih.gov/books/NBK26876/#A1133
Yup indeed. Worth pointing out that chromosome counts give a big clue to the evolution of DNA too. We have 46 (23 pairs), earthworms 36, goldfish 104. Some species of fern on the other hand have 1,200. Does that mean the goldfish and ferns are in some way more "sophisticated" species than
Homo sapiens?
Nope - it just means that they've been around longer so their DNA has had more opportunities to mutate, just as you'd expect in fact with an evolutionary process subject to natural selection.
Funny that.