I think most of the people on this site know about the famous Baltimore paper describing the ability of the poliovirus to replicate itself without the need of cells but I want to expand on the issue and ask could it be possible to have truly "cell-free" Life-e.g. life forms that do not have cells in any form according to modern biology but yet can be considered "alive" by its standards? This is the first paper in historical context describing the possibility of creating a self-replicating molecule in the laboratory. Well, it's about a viral genome and it only can self-replicate so it's not like it's alive according to what we consider "true" living organism, but nevertheless it triggers an interesting chain of assumptions in my mind. What if we could design a system where nucleic acid can evolve outside of cells? Then, what if we managed to provide an energy source t drive this evolution outside of the context of cells? Would such nucleic acid evolving on its own in a test tube depending only on the energy source we provide and on the specific conditions in the test tube be considered equal to a gene evolving in a "true" living organism? What if then we managed to add more nucleic acid's molecules to the system, just enough to have all the components involved in the replication of the evolving nucleic acid molecules synthesized by the system itself? Then can we consider this system analogous to a living organism, e.g. truly alive? What if we continued adding nucleic acid molecules to the system to the point when it was able to produce ATP from organic molecules used by what we commonly consider to be "alive", e.g. entities we prescribe the name living organisms, like glucose, for example. Then what would be the difference between this chemical reaction system and a genuine living organism? What if we continued building up this "in vitro metabolism" to the point when we have a genuine "molecule laboratory" testing the fitness of new nucleic acid molecules to itself. A true evolving, replicating and self-organizing molecular "machinery" we could "grow" in a test tube. Would we then consider such a thing a genuine living organism and if so why?
Yes, I know it's a "fringe question" and out of the scope of almost all branches of biology but nevertheless I think it's one of those questions that can "capture our mind". So, do you think there could possibly be such a thing that we could deem "alive" but have no cells at all? Something organized in such a way that we can readily call it a life form but yet not organized in the "way we think" about Life in general? If this is possible, when do you think this system of reactions could be called genuine living organism?
To the moderators-my question is different than the question "Why isn't a virus alive?" because it has a much broader perspective than it-a cell free form of Life can be anything-from a self-replicating "grey goo" to an evolving tornado. Viruses are only one small particular subset of possible answers. Plus the question you are referring to isn't about synthetic biology and the possible diversity of life forms as is mine but is only about a particular aspect of what we call a virus-its pertaining to the set of life forms or not. My question has both different direction and different set of objects it's aimed at. How can the two be identical, then?