Tristan Money
Life Sciences Research Task 2016
25/06/2016
How Plausible Are the Theories of the Origins of Life on Earth? Which Theory(s) Is The Most Credible?
For thousands of years, theories of the origins of life on Earth has differentiated vastly due to science, religious belief and philosophy. Although we are unable to specify which of all these theories are correct (hence, the use of the term ‘theories’), science has seemed to provide the most logical and supported conclusions to how it really began. While all scientific theories have logical formulations to how they were concluded, it is important to understand that only one, if any, may be correct and, thus; the theory with both the most evidence supporting it and the least evidence discouraging it must be taken into account as to being the most plausible.
It is also important to acknowledge that scientific research and experimentation has concluded that the universe had started 13,7 billion years ago. Thus, any theory involving the origins the Earth having occurred before then are currently irrelevant and, thus, implausible. Alongside that; scientific evidence has, so far, concluded that the origination of the Earth occurred back to about 4,55 billion years ago. This, in essence, further discredits any theories of life having originated before then.
So, where do we begin? Ah, yes’ ‘evolution’. Evolution is defined as ‘the ongoing transformation or development of something’. Evolution does not only apply to biology, but the origins and advancements of anything and everything. ‘Biological evolution’ may be defined as ‘the change in the gene pool of a population during the course of time by such processes as mutation, natural selection and genetic drift’.
Before the 1700’s, most scientists believed that species were not linked and that they had remained unvaried. This was due to the belief that the universe and all within it was created by a ‘God’ or Godlike power. Scientists also believed that the Earth was young and static.
However, between the 1700’s and early 1800’s, these concepts were confronted by Erasmus Darwin and Jean-Baptiste Lamarck. Both these men, from their interest in the study of fossil collections and their knowledge of how largely diverse living organisms on Earth are, were seemingly confident in that species slowly transformed over time. They were, therefore, convinced that the Earth had to be much older than what was, at the time, most popularly believed. These were not the only theories that these men had, however these were the only two common theories between them.These two men later came to the conclusion (due to their original beliefs) that species have shared ancestors. As a result of this conclusion they were also able to conclude that, to be put briefly, evolution took place within species as a need to adapt to their environment. At this point, however, a considerable means for evolution had not yet been determined.
‘Primitive Earth was very different than the way things are now. There were probably many oceans and seas with many hot vents at the bottom of these waters and quite a bit of volcanic activity on land. The atmosphere most likely contained water, methane, ammonia, and hydrogen, unlike our current atmosphere, which is mostly nitrogen and oxygen.’
Charles Darwin (Erasmus Darwin’s grandson) had, taking into account the concept of common ancestry and the need to adapt to a new environment, further supposed his idea of ‘diversification’ as species were continuously evolving into new species. Darwin explains that this was due to a ‘branching’ affect. Much like how two people may not be blood relatives of one another, but can be traced down (through many generations) to one common ancestor using their family trees. He also arose the topic of species being extinct, which is evident through fossil records. This is referred to as ‘descent with modification’.
Alfred Russel Wallace and Charles Darwin, while both working towards formulating an acceptable explanation for how evolution may have occurred, had come across one another’s ideas. It turned out that both these ideas were very similar to each other, encouraging these men to work together. Putting their ideas together, they published what we know today as ‘natural selection’; which is Darwin’s most important contribution to science. Natural selection states that individuals which are best adapted to their environment will leave the most offspring.
In order to conclude a plausible theory on how life on Earth originated; It must be understood that, ‘The origin of life on Earth is a set of paradoxes. In order for life to have gotten started, there must have been a genetic molecule’something like DNA or RNA’capable of passing along blueprints for making proteins, the workhorse molecules of life.’
Each and every form of life on Earth had to have all descended from one common ancestor. The diversity and variation between life on Earth has developed over an extremely large period of time. This is a concept called ‘macro-evolution’, which may be defined as ‘the descent of different species from a common ancestor over many generations’.
The idea of there being a single origin of life is, currently, the most scientifically accepted opinion of how life originated. This theory is substantiated by the fact that all life on Earth share the same genetic code and analogous basic enzymes. This, however, still does not explain how life actually originated on Earth.
Today’s understanding of evolution is strongly supported by the following eight concepts of biology:
‘ Fossil records
‘ Biogeography
‘ DNA and molecular biology
‘ Homologies and comparative anatomy
‘ Embryology
‘ Vestigial Organs
‘ Biodiversity
‘ Physiology
‘Relative dating’ and ‘radiometric dating’ (absolute dating) are methods used to determine the age of a rock layer. We are, thus, able to determine the age of a fossil that is entrenched within that rock. The dating of fossils is a very important tool in determining the origins of life.
What is assumed to have been the earliest organisms ‘ namely ‘stromatolites’ (fossilised Cyanobacteria) were discovered in South Africa (Barberton in Mpumalanga). Stromatolites are said to have formed from strata of blue-green algae. Scientists were able to compose that this is yet to be the earliest evidence of life due to fossil dating.
‘Stromatolites are layered mounds, columns, and sheet-like sedimentary rocks. They were originally formed by the growth of layer upon layer of cyanobacteria, a single-celled photosynthesizing microbe that lives today in a wide range of environments ranging from the shallow shelf to lakes, rivers, and even soils. Cyanobacteria are prokaryotic cells (the simplest form of modern carbon-based life) in that they lack a DNA-packaging nucleus. Bacteria, including the photosynthetic cyanobacteria, were the only form of life on Earth for the first 2 billion years that life existed on Earth.’
Up to date, stromatolites being the eldest form of life yet to have been discovered, thus we are obligated to believe that these were the origin of life. However, there is still no evidence supporting where or from what Cyanobacteria had originated from. In an ever changing society, scientists are constantly making new discoveries daily. Therefore, we need to ask the question: ‘Will there ever be a definite answer to how life on Earth originated?’
Even when scientists believe that they have ‘cracked the code’ ‘ the next day somebody might make a discovery that completely contradicts their theory. Who knows, there might even be a discovery that one day completely contradicts all that we know and understand about evolution. Who is to say that religious belief or, even, a specific religious belief is incorrect in its explanation of the origins of life? And has anybody been able to provide evidence that religion does not explain the truth to the origins of life? No ‘ or not yet, anyways.
We can only build onto what we already know up to this point. However, for there to be furthered suppositions to how life originated, evidence must be provided that supports that supposition. ‘Evidence’, in essence, is what makes this concept of science and biology so challenging to improve on. And, just as is required for evolution in itself, improving and hopefully, sometime in the future, finalising a theory and bringing it to being fact will only occur over time. ‘The evolution of the idea of the origins of evolution’.
Due to a lack of evidence, Cyanobacteria did not evolve from another organism nor did it evolve from anything on Earth. This, essentially, in some ways both supports and contradicts Darwin’s theory (descent with modification). Supporting his theory in that Cyanobacteria is the common ancestor of all living things. Discouraging/contradicting his theory in that surely Cyanobacteria would then have had to have originated from another organism which acts as a common ancestor for many other species of organisms.
However, it is clear that, while none theories are yet to have been proven to be correct, the most plausible and credible theory to date, in essence, is: Cyanobacteria is the origin of all life on Earth, as this is evidently the oldest organism yet to be discovered.