The origin of life remains one of the world's greatest mysteries even to this day. Several theories have attempted to explain this phenomenon, but thus far, there has been no conclusive evidence to support one theory over another.
One of the most popular theories is the primordial soup theory. This model purports that all life on the planet was created out of a “primordial soup." Oparin and Haldane, the scientists who developed this model, hypothesized that all life forms originated in a warm pond or ocean from a combination of chemicals that created amino acids. All the building blocks of life were already available in the atmosphere. These molecules were then “energized” by lightning, and combined to form amino acids which, in turn, folded into complex proteins. The first organisms to evolve were simple heterotrophs, which survived by consuming other organisms. Theoretically, this is plausible. Miller and Urey, in 1950, carried out a rather famous experiment to test this theory. They mixed gases believed to have been present in the primordial atmosphere and then energized the mixture with an electric spark. They discovered that all 20 amino acids could be produced in this manner.
However, there are several major flaws in this theory. First, the formation of proteins from amino acids is an extremely complex process. There are over a trillion ways amino acids can combine to form proteins, and hitting upon the right protein by accident is extremely improbable. Moreover, the primordial soup would have been way too diluted to achieve anything. In short, there is just too much left to chance. As one critic put it, “What are the chances that a monkey playing with an old typewriter will accidentally type out a bestseller?”
An alternative theory is that life originated deep underground, not in a water body. One could argue that “superbugs," which are present in deep soil even today, were the first life forms to evolve. They may have originated as microbes thriving on intense heat. However, there has been no satisfactory account of how these superbugs evolved from a mass of chemical compounds.
Another hypothesis is that life did not originate on the earth at all. The Panspermia theory suggests that life seeds came from outer space. This theory has found considerable support, as it explains the sudden spurt in life forms after millions of years of nothingness. Also, statistics show that 7.5% of rocks from Mars reach earth. Such rocks, from Mars or elsewhere, could have transported bacteria, which can easily survive the harsh environs of space. After all, there is evidence that meteorites contain amino acids and bacteria. Panspermia states that these meteorites carried bacteria, amino acids, methane and carbon. These substances were then deposited on earth, either in warm oceans or underground, and eventually grew into simple life forms. This theory merits further research because it has potential to explain not only the origin of life on earth, but also prove the presence of life beyond the earth.