The signal gone. For genes such as DNA and RNA polymerases which we can trace back quite a distance in time but not to any single origin, we can understand what the process is, and how long it takes in various life forms (for example RNA viruses evolve some ten million-fold faster than the DNA of Eukaryote nuclei). But we also know that there was no single common ancestor of all genes. There is plenty of information about all of this, adding more complete genomes of more organisms does not help with this particular question.

For just one example of de-novo protein-coding genes arising over time, we can observe the "accessory genes" such as tat, rev, vif, nef and vpr arising in the lentiviruses over the past 2 - 10 million years. All of the endogenous retroviruses, including the endogenous lentiviruses found in several mammalian genomes (weasels, Madagascar lemurs, rabbits) are simple gag-pol-env retroviruses lacking these accessory genes, and we can see that some evolved early and are shared by all modern lentiviruses (primate, feline, equine, bovine, caprine and others) while others have evolved more recently and are only shared by a few which shared a recent common ancestor (such as vpu found in HIV-1, SIV-CPZ and SIV-gorilla). We may even be observing yet another new gene evolving today in a subset of the HIV-1 M group; the "anti-sense protein" coding region on the opposite strand of the env gene seems to be more conserved (no stop codons being introduced by mutations in env, for example) than can be explained by factors other than selection for conservation of this open reading frame.

Thank you Artur and Brian for clarifying this.

I can imagine now that such consensus gene might not even been composed of the common DNA/RNA/Protein elements at all but probably something more simple and easier to catalyze (and with building blocks more common in nature). Probably some self replicating organic polymer (again with some preservations on the organic part).

There is another question that bothers me: Why this process of evolution never occurred again? Does the natural fauna and flora prevent evolution from starting over?

It was one heck of a job to get biological life started in the first place; to work out using a few building blocks like sugars, amino acids, nucleotides, and so on. And then to come up with machines like polymerases and ribosomes and house them in cell membranes was a very huge deal. It took a billion years or more to get the basic self-replicating cells going. There are millions or billions of other planets circling suns in other parts of the universe, so it is possible something like life got going somewhere else. But no evidence of other complex self-replicating systems on earth, as far as I know (other than man-made in computers etc). Most new species of life go extinct on earth, and I am not sure how another system could out-compete or even survive the current biological competition.