The Origin of Life
Life has been around for a long time on earth - The Origin of Life introduction. Scientists believe that the conditions on Earth were suitable for life to evolve some 3,800,000,000 years ago. That seams like a long time and if we compare that to the date we believed the earth was formed, 4,600,000,000 years ago, we find that for most of earth’s history some form of life has been around. The earliest fossils found on Earth indicate to us that life was present 3,500,000,000 years ago, but this life was only in the form of simple cellular life, no sign of the large multicellular organisms found in this time period. The question is; how did this life come to exist at all? What was the origin of life on Earth?
To answer this question we need to know more about the environment this early life was living in. Scientists have looked at the moon and seen the craters that exist there. Why are there no such craters on Earth? The answer to that is, there are craters on earth. They have just either been worn away by natural processes or are hidden under the ocean. This means that early earth must have been bombarded by comets, creating a highly hostile environment. This brings us to the first theory as to the origins of life on earth. As so many meteorites were colliding with the earth, it is not impossible to assume that several of these meteorites may have contained elements not found in abundance on earth at this time.
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Comets found in recent years have yielded many elements that were not thought to have existed in such abundance. So, could this have been the method of ‘seeding life’ onto the planet Earth? There is great debate as to this theory, which is called panspermia. In modern day meteorites extraterrestrial organic compounds, including amino acids, have been found. Biochemists recently demonstrated that organic molecules extracted from meteorites produced small vesicles when mixed with water. We have not yet seen any evidence of life existing anywhere else in the universe, so it may be safe to assume that these comets didn’t play a pivotal role in the evolution of life.
Other early environmental events include the formation of the oceans. Vast expanses of water were formed in a relatively short time period. Scientists have uncovered evidence, which suggests that life started in the oceans. There were layers of tar protecting the oceans from the intense UV rays that the sun released. Within the oceans, there was a mixture of Amino acids, sugars, porphyrins and other unknown substances. Scientists of today have recreated this ‘soup’ to the best of their ability, and have found that the results were very encouraging. Life didn’t spring forth, but they were close. So, if this theory of ‘spontaneous generation’ was true, then just what was created?
We believe that the first elements of ‘life’ were not cells themselves, but simple strands of RNA. This era was coined the ‘RNA world’. This RNA was comprised of a string of amino acids. The string had several three base units we call a triplet code. Each triplet code comprises of three of the following bases, which can be in any order in the code; Adenine, Cytosine, Guanine, Uracil. Each can be used from once to three times in each triplet code. This provides several possible triplet codes, which can be linked in any order to form an almost innumerable number of RNA molecules.
RNA molecule Triplet code
Notice that RNA was the original element of life, not DNA. We believe DNA is a mutation of RNA, which then enabled more complex life forms to evolve.
RNA itself is not ‘life’, but the formation of RNA allowed for inorganic precursors to form into organic molecules. Prokaryotes were born. Simple single cellular organisms capable of self-replication due to RNA. This couldn’t happen in the modern day world, because of the oxygen rich environment. Oxygen attacks chemical bonds and we believe that the oxygen rich environment we live in today is a product of waste gases produced by prokaryotes over many millions of years. Evidence suggests that the early atmosphere comprised of water, Carbon dioxide and Nitrogen. These prokaryotes then ruled alone for 2,000,000,000 years before the evolution of DNA based life.
Many Scientists doubt that it was actually the atmosphere that played the pivotal role in these early chemical reactions. They believe that it was the deep-sea vents and submerged volcanoes that actually spewed forth the elements of life. But wherever these elements came from, the provided the basis for self-replication, and thus life was created. This life lived off of the raw materials found in the early oceans, but that was not going to be an endless supply. The prokaryotes evolved over time and developed systems for harvesting light energy given off by the sun, to fix carbon dioxide, found in abundance at the lime. We call these the cyanobacteria.
The reason that we know what we do about these early forms of life is derived from observations of modern day prokaryotes and that of fossil evidence dating back some 3,800,000,000 years, in rocks called Stromatolites. The fossils are very similar to species of cyanobacteria found today in ocean lagoons. All life now found on earth can be traced back to these simple prokaryotes. Over millions of years, the waste gas oxygen was produced by prokaryotes, and this led to its accumulation in the Earth’s atmosphere.
This allowed for oxygen metabolising organisms to evolve. Eukaryotic organisms evolved to use the more complex DNA molecule and multicellular life was born. So, the evidence presented to us suggests that the origin of life was a spontaneous generation of nucleotides into an RNA molecule, but we can’t be certain as to whether this is true or not. Perhaps future scientific methods will allow us to take a better look into the past and give us further insight as to the all important origin of life.
Because we don’t know for sure what the origin of life is, a vast majority of people reject our scientific theories and evidence for evolution. Instead they believe religion will solve the problem. There are many human faiths across the globe, Buhidism, Chistianity and Judaism for example. People who follow these faiths often believe very strongly in their ideals. Many faiths contain ‘holy scripts’ like the Bible in Christianity. The Bible tells us that the world was created by an almighty being called God.
It states that he created all life in his image and he was the one who created all of the people and all of the animals on earth. This theory as to the origins of life goes against everything that science stands for. Scientists need evidence, and the evidence that we have goes against everything these texts say. Most faiths believe that some sort of Supreme Being created life, and people may believe this because it is the easy way out of the question, what was the origin of life on earth?
I have included this religious argument because it is believed in by a vast amount of people. It may not be very scientific, but it proves that science is not the only method people use to solve this question. In fact religion has been one of the greatest ever hindrances on scientific study, because religious groups were afraid of what we might find.
Have we found the answer to the question, what was the origin of life? The answer is, we don’t know, we can only theorize as to the origins of life. Perhaps one day we will be advanced enough to know for sure. But whatever it was, we’re thankful that it came to pass!