How Did Life on Earth Begin?

There are a variety of scientific opinions about how life on earth began. Some believe that life on earth arose from outer space, either as primitive cell or as DNA deposited from another planet. The hypothesis that life began on some far-off planet, at best, simply begs the question. How did life begin on that planet? A more scientific explanation is that life slowly formed under conditions present on our planet 4 to 5 billion years ago, Evidence supporting this idea has come from experiments in the laboratory that reconstruct the of the primitive earth. Many experiments along this line have been done within the last 20 years. When plausible conditions on primitive earth are simulated in reaction vessel, many simple organic compound s of biological significance from spontaneously and in relative abundance these includes amino acids, aliphatic hydrocarbons, sugar, purines, and pyrimidines, which are the precursors of proteins and nucleic acids. To carry this to the next logical steps, investigators have produced peptides, but in relative small amounts. If dry amino acids are heated from week or so at 1200 C, large numbers of protein-like molecules with molecular weights of about 10,000 can be produced. Similarly, polymers of nucleotides can be produced,

This brings up an important question, which came the first protein (the chicken) or the nucleic acid (the egg)? The protein catalyze biological reaction including synthesis of nucleic acid s provide the information required to make proteins. It would seem that you can not have one without the other. This was indeed a big quandary until the early 1980’s when Thomas Cech discovered for the first time that nucleic acids, specifically RNA, could also catalyze reactions. This was true an astounding discovery, and in 1989 he was awarded the Nobel Prize.

It is now postulated the evolution began with RNA molecules performing the catalytic activities necessary to assemble themselves from nucleotide precursors. The RNA molecules evolved in sell replicating patterns, using recombination and mutation (RNA mutation is much more rapidly than DNA mutation) to explore new functions and adapt to new niches. RNA molecules then began to synthesize proteins, eventually arranging them according to RNA templates. Eventually protein was able to carry out catalytic functions better than RNA. At some points, single single –stranded DNA appeared with its unique properties of increased stability and faithful self replication.

How did cells arise? Most scientist believe that protocells , the precursors of modern-day cells, developed first . These were cluster of proteins and nucleic acids. Billions of years ago nucleic acid evolved more capacity to encode new proteins that stabilized the protococells, and primitive bacteria arose. Further evolution over about 3 billion years gave rise to what we see around us.