The Smithsonian Magazine has an article this week proposing that we consider Mars as the origin of Terrestrial Life. This notion stems from Steven Benner’s Four Paradoxes: The Tar Paradox, The Water Paradox, The Single Biopolymer Paradox and The Probability Paradox. Each of these is described in the abstract of his work, and do add up to a possible alternative for life’s origin. However, as compelling as his arguments may be, the origin of life will always be a mystery veiled in time. Even if we were to find evidence of life on Mars that is very much like that on Earth, it would be difficult to say whether Terrestrial life was the origin of Martian life, or vice versa.
Another problem I have with tracing the origins of life off-planet is that it does not solve anything, but merely relocates the source. So it’s not that I feel that Benner’s work is uninteresting or unworthy of consideration, but presently, Ockham’s razor precludes seriously considering extra-terrestrial origins without a good deal more hard evidence. Further, relocating the source or life’s origin does little to change how we think about origins. Regardless or where life started, it is still highly probably that it began with RNA, a unique molecule in that even today it serves dual roles as an information-carrying molecule and a structural one that often has enzymatic function. And, that the addition of the more stable , DNA molecule as the primary source of information happened later – as adding protein synthesis also did for providing an alternative structural / functional molecule.
Evolution of the Central Dogma?
DNA -> RNA RNA -> Protein
DNA -> RNA -> Protein