Doesn't that just beg the question? If life originated on some other planet and made it to Earth, why did only the DNA-based lifeform(s) make it here?
If we assume that different kinds of life based on different nucleic acids can co-exist, then it seems unlikely that a single kind would have happened to be carried to Earth by a natural process.
If we assume DNA has some inherent fitness advantage (so that only DNA-based life survived the journey), than we don't need the additional assumption of panspermia: perhaps only the DNA-based life survived some early period in Earth's history.
Also, for abiogenesis, given that we still can't reliably reproduce something like that, and that we have never seen new kinds of life spontaneously appearing on Earth, we do have some circumstantial evidence for the possibility that it is an incredibly unlikely event, such that it might have only happened once in Earth's history.
Edit: There is also another simple possibility: perhaps given the resources available on Earth, either forever or in the period where abiogenesis was possible, perhaps DNA(+RNA) is the only molecule with the right properties to act as genetic material. Perhaps there is no common ancestor to all life on Earth, but a "forest" of inter-breeding, spotnaneously arisen original organisms, but they were all DNA/RNA-based simply because of the available resources.
If we assume that different kinds of life based on different nucleic acids can co-exist, then it seems unlikely that a single kind would have happened to be carried to Earth by a natural process.
If we assume DNA has some inherent fitness advantage (so that only DNA-based life survived the journey), than we don't need the additional assumption of panspermia: perhaps only the DNA-based life survived some early period in Earth's history.
Also, for abiogenesis, given that we still can't reliably reproduce something like that, and that we have never seen new kinds of life spontaneously appearing on Earth, we do have some circumstantial evidence for the possibility that it is an incredibly unlikely event, such that it might have only happened once in Earth's history.
Edit: There is also another simple possibility: perhaps given the resources available on Earth, either forever or in the period where abiogenesis was possible, perhaps DNA(+RNA) is the only molecule with the right properties to act as genetic material. Perhaps there is no common ancestor to all life on Earth, but a "forest" of inter-breeding, spotnaneously arisen original organisms, but they were all DNA/RNA-based simply because of the available resources.