Synopsis for the published article: Ashwini Kumar Lal,
"Origin of Life",Astrophysics & Space Science (2008) 317: 267-278
(DOI 10.1007/s10509-008-9876-6)
SCIENCE REMAINS CLUELESS REGARDING ORIGIN OF LIFE
Myth surrounding origin of life on earth and elsewhere in the universe appears to have unfolded. It is beyond the realms of science to pinpoint when and where precisely life had its beginning in the universe. Writing in a leading European journal, Astrophysics & Space Science, Ashwini Kumar Lal has come out with this revelation after detailed review of the the existing theories relating to origin of life. Lal's interesting concusion is based on the latest research in the fields of genetics, astrobiology, and space science.In the invited review article, Lal has concluded that " Ever since Oparin and Haldane initiated the modern theory of life''s origin from nonlife in 1930s, we have learnt much about how life operatees, but almost nothing about how it originates. It is a puzzle whose mystery will perhaps remain unknown to the humanity ad infinitum".
The prominent hypotheses about origin of life like abiogenesis, RNA World, iron-sulphur world(deep-sea-origin of liife), and panspermia fail to provide clues regarding the exact origin of life. Though panspermia provides an alternative to the earthly abiogenesis (generation of life from non-living matter), it fails to address nagging uncertainties pertaining to the timing of commencement of the process of evolution of life on the primitive earth and elsewhere in the universe. As per panspermia, life arises everywhere, but seeds of life can trvel across galaxies as life 'spores'' protected in comets from ultraviolet radiation, and seed the planets in the solar system and elsewhere in the universe. Panspermia requires life to have been introduced to earth some 4 billion years ago, with an ongoing incidence of microorganisms arriving on the earth from space, hitchhiking on comets and meteorites, that continues until today.
Lal mentions about 'extremophiles'which are usually unicellular microbes(bacteria and archaea) that can survive in the harshest of environment on the earth-considered extremely inhospitable by humans and other creatures, in his paper. Such microorganisms thrive in extreme cold, extreme hot, extreme acidic, and extreme alkaline conditions. Some thermophiles have been found to flourish at a depth of 2.8 km in gold mines in South Africa, while methane-oxidizing microbes have been reported to be thriving at a record depth of 1.62 km beneath the Atlantic seabed at simmering temperature of 60-100 degree Celsius. Given the potential of extremophiles to survive in highly inhospitable environments on earth, possibility of life on extraterrestrial bodies like Mars, Europa, Enceladus, Titan , in the solar system could not be ruled out. Keeping in view the great survival instinct of extremophiles on earth, possibility of traces of life being found on
billions of unexplored planetary bodies outside our solar system cannot be negated as well.
According to Lal, there is general consensus among biologists that bacterial cells cannot evolve from nonliving chemicals in one step. It is speculated there must be some form of precellular life. Of the various theories of precellular life, in the early stages of evolution of life on earth, the most popular contender today is 'RNA World'.The self-replicating RNA molecules were believed to be common 3.6 billion years ago...There is growing evidence to support the idea that emergence of self-replicating RNA was a crucial early step in the evolution of life on earth. How the RNA came into being, however, remains unknown so far. Nor the experiments involving biologically produced RNA have provided concrete proof regarding RNA World being the pathway between nonlife and life.
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