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It is commonly accepted among origin-of-life scientists that the emergence of life was an evolutionary process involving at one stage or other the working of natural selection. Researchers disagree, however, on the nature of the chemical infrastructure that could have formed prebiotically, enabling the evolutionary process. The division of the origin-of-life research community into ‘geneticists’ and ‘metabolists’ usually revolves around the issue whether the first to arise prebiotically was a genetic polymer or a primitive metabolic system. In this paper I offer an alternative classification based on the attitude to the onset of natural selection. From this perspective I add to the conventional division between gene-first and metabolism-first groups a position I call “preparatory metabolism”. By this line of thought, an RNA or an RNA-like polymer could not have emerged prebiotically. Nevertheless, the onset of natural selection had to wait until such a polymer had arised. This paper examines the RNA-first, RNA-later, metabolism-first and preparatory-metabolism scenarios, assessing the weaknesses and strengths of each. I conclude that despite the recent theoretical advances in all these lines of research, and despite experimental breakthroughs, especially in overcoming several RNA-first hurdles, none of the examined paradigms has yet attained decisive experimental support. Demonstrating the evolvability of a potentially prebiotic infrastructure, whether genetic or metabolic, is a most serious challenge. So is the experimental demonstration of the emergence of such an infrastructure under prebiotic conditions. The current agenda before origin-of-life researchers of all stripes and colors is the search for the experimental means to tackle all these difficulties.
Are viruses alive? Until very recently, answering this question was often negative and viruses were not considered in discussions on the origin and definition of life. This situation is rapidly changing, following several discoveries that have modified our vision of viruses. It has been recognized that viruses have played (and still play) a major innovative role in the evolution of cellular organisms. New definitions of viruses have been proposed and their position in the universal tree of life is actively discussed. Viruses are no more confused with their virions, but can be viewed as complex living entities that transform the infected cell into a novel organism—the virus—producing virions. I suggest here to define life (an historical process) as the mode of existence of ribosome encoding organisms (cells) and capsid encoding organisms (viruses) and their ancestors.I propose to define an organism as an ensemble of integrated organs (molecular or cellular) producing individuals evolving through natural selection. The origin of life on our planet would correspond to the establishment of the first organism corresponding to this definition.
In fact, there is no life without living organisms and all presently known living organisms are thriving on planet Earth. If one day we hopefully meet friends from another world, it will then be possible to define “life” in term of the common properties shared by organisms from both planets.
Originally posted by SplitInfinity
reply to post by jiggerj
Some have raised the argument that LIFE cannot be created. This is not true. All one has to do is look at a VIRUS. A Virus has DNA but is NOT ALIVE!
"Viruses straddle the definition of life. They lie somewhere between supra molecular complexes and very simple biological entities. Viruses contain some of the structures and exhibit some of the activities that are common to organic life, but they are missing many of the others. In general, viruses are entirely composed of a single strand of genetic information encased within a protein capsule. Viruses lack most of the internal structure and machinery which characterize 'life', including the biosynthetic machinery that is necessary for reproduction. In order for a virus to replicate it must infect a suitable host cell".
Originally posted by Phagette
You know what really bums me out? Having access to all kinds of very good scientific literature (on all kinds of subjects) but it is all copyrighted. I can download the pdfs because I am affiliated with a university that has that various subscriptions, but I can't just link to the articles because they are for-pay for everyone else (frowny emoticon here that I will someday learn how to embed). Someday I'll write a thread on the topic because it really bothers me, but for now I'll cheat a little: