In the anicent period Spanish Priest father Saurez (1548-1671) forwarded the theory that life was originated by some supernatural power of god. According to his theory, world was made in six days. In the first day heaven and earth were created, sky on second on the third day, The sun, moon and stars on the fourth Bird and fishes on the fifth and finally man and women were created. According to him first man was Adam and Women was Eve. This theory has no scientific proof so it is not accepted.
The Greek philosphers of Prechristian era Thales (640-546BC), Anaximender (611-547BC), Empedocles(495_435BC), Plato and Aristoles (384-322BC) followed the theory of Spontaneous generation(Abiogenesis) . According to this theory life originated from non-living materials automatically from time to time. It was belived that frogs, mice, toads, snakes arose from the mud, parisites, beetles and flies arose from the sweat and manure, aplids and others insects arose under the influences of heat and moisture and micro organism arose from air or water.
Later on the theory of Biogenesis i.e Living beings only was forwarded by different scientists due to which the theory of Abiogenesis fails. Francesco Redii (1626-1698) had experimentally proved the theory of Biogenesis. He had taken three jars with meat. First jar was kept open, second jar was covered by net and third one was covered by a piece of paper. He observed little white worms and larvae (maggots). opened jar. In other two jar worms and larvae developed outside the net and paper. He concluded that maggotswere borne due to contamination of meat by flies. Another scientist Lazaaro Spallanzani (1729-1799) performed experiment to conclude that even primatives, unicellular oeganisms lso cannot aeises from non-living matters. Louis Pasture (1822-1895) a french microbiologists disproved the theory of Abiogenesis of microbes. He had proved that self generation of organism is impossible.
CHEMICAL EVOLUTION OF LIFE
chemical is the most modern and convincing theory of origin of life. Russian Biochemist Alexander Ivanovich Oparin (1923) and englishman J.B.S Haldine(1928) independently gave the "Biochemical theory of origin of life" This theory purposed the origin of life occured along the origin and evolution of earth and its atmosphere. This theory is called "oparin-Haldane Theory" . Accordindg to this theory life on the earth was originated by non-living molecules throughout the series of chemical reactions.The inorganic molecules formed simal organic compound, simple compound forms more complex compound which finally formed first living being, cell. Oparin have rxplain about this theory in a book called "The origin of life on earth" which was published in 1936. yhis theoty can be explained in two ways
1. Chemical Evolution (Chemogeny)
2. Biological Evolution(Biogeny)