Posting my Nature of Science IA - Writing Wednesday

Hello everybody and welcome back to another blog post, 

As many of you will already know, as part of the International Baccalaureate, I studied Nature of Science which was a subject that combined elements of biology, chemistry, and physics, alongside a deeper analyses of the scientific method. For the Internal Assessment (coursework), we had to construct our own essay question based on a topic of our choice. I really enjoyed learning about the Miller-Urey experiment in class so I decided to write about this and frame my question into the wider context of the origin of life. In this essay, therefore, I discuss the value of the Miller-Urey experiment, which was carried out in the 1960s, and I also cover if the experiment, based on my findings, significantly changed the way scientists perceive the origins of life. I know that there is a lot of scientific jargon in this but I've subheaded sections for your clarity. I hope you enjoy this read and let me know what you guys think in the comments below!

Did the Miller-Urey experiment create a paradigm shift in the way scientists understand the origin of life?

Introduction:

Stanley Miller and Harold Urey’s Miller-Urey experiment pioneered the way scientists understood and considered the origins of life. Through their experiment, Miller and Urey were able to provide evidence to support a molecular origin of life, granting the first steppingstone for scientists to understand one of biology’s most unexplored questions; where did life begin? The two scientists carefully preserved their findings in sealed vials and scientific papers, to aid further research into the field of study. However, later observations of the results produced in the Miller-Urey experiment, revealed that there were gaps in the original experiment that had the potential to discredit Miller and Urey’s hypothesis. This led to future scientists modifying the experiment and supporting opposing possible explanations for the origins of life.

A paradigm shift, as stated by the philosopher of science Thomas Khun in 1962, is “a fundamental change in approach or underlying assumptions” [AB1]  (Kuhn, 1962) meaning that for the Miller-Urey experiment to be a paradigm shift, it would have to fundamentally change the way that scientists frame their understanding on the origin of life. Therefore, in this paper, I will be comparing the Miller-Urey experiment to the experiments and modifications made by other scientists such as Bada, as well as contrasting explanations for life’s origins such as the Panspermia theory, to interpret the significance of Miller and Urey’s claims and whether they prevent the Miller-Urey experiment from being a widely accepted explanation for the origin of life. This will help me to determine whether the Miller-Urey experiment created a paradigm shift in the way that scientists understand the origin of life. [AB2] This research question explores the nature of a paradigm shift and whether the Miller-Urey experiment radically changed the way that scientists conceptualise the origin of life.

The original consensus of the origin of life and the Miller-Urey experiment:

Many individuals have made different claims into the origins of life, but it was not until the 20th century when an official scientific consensus on this topic began to be developed. The oldest beliefs on the origins of life were viewed from a religious perspective, with many people in ancient history believing that the world was divinely created. It was ideas such as creationism that first dominated people’s understanding of the topic. The creationists were a group of Christians who believed that life, nature, and culture was of divine creation and was therefore made by God.[AB3]  The Book of Genesis recounts how God created the world, the plants, and the animals in a period of six days (Wikipedia, Book of Genesis, 2001). This was a book that many Christians relied upon for their knowledge of the origin of life because it provided an easy explanation for life’s origins (BBC, 2009). However, the first memorable scientific idea that gained recognition was the Oparin-Haldane hypothesis, developed by Russian biochemist Alexander Oparin and British scientist J. B. P Haldane in 1924. This hypothesis suggested that life originated in a “primordial soup” where inorganic compounds reacted together to create the complex organic molecules needed for life (Lazcano, 2015). This [AB4]  hypothesis was developed because at the time, scientists believed that early Earth was largely made up of reducing gases [AB5]  such as ammonia (NH4), methane (CH4), hydrogen (H2), and water (H2O) and Oparin and Haldane believed that these gases could have reacted in the ocean to create organic molecules. This was how the theory of Abiogenesis was first created. Abiogenesis is the process by which life arose from simple organic compounds. (Wikipedia, 2001) Many scientists create hypothesises which are explanatory statements about the world that can be true or false and can be tested through either experimentation or observation.[AB6]   The Miller-Urey experiment was the first to put Oparin-Haldane hypothesis into practise to see whether the explanatory statement about the origin of life was true. [AB7] 

In 1952, Stanley Miller, supervised by Harold Urey, at the University of Chicago, carried out an experiment where they attempted to simulate the conditions of early Earth to see if the conditions provided the mechanism for organic molecules to form. Figure 1 demonstrates the system used by Miller and Urey. In their experiment, water was heated in a flask to mimic the ocean being heated by the sun. The water vapour that was produced as a result was combined with the gases (methane, hydrogen, and ammonia) in a connecting flask, creating their artificial atmosphere. The gases were stimulated with electrical sparks using electrodes to simulate lighting, and the new gas molecules were condensed in a cooling tube so that they could be collected into a primordial soup or the artificial ocean (Bhattacharjee, 2013). Through a chemical analysis of the remaining ‘soup,’ Miller and Urey were able to detect 5 amino acids[AB8]  4 of which were proteinogenic and therefore essential for life (Daily, 2008). This experiment showed that complex organic molecules needed for life (such as amino acids), could be formed from the simple inorganic compounds that were already found on primordial Earth. In the past, some scientists [AB9]  believed that the origin of life was too complex to study in the laboratory. Even Harold Urey himself in 1962, highlighted the challenges that scientists faced when researching this field stating that “All of us who study the origin of life find that the more we look into it, the more we feel that it is too complex to have evolved from anywhere.” (Urey, 1962) In 1952, scientists James Watson and Francis Crick discovered the double-helical structure of DNA which changed scientist’s understanding of molecular biology (Pray, 2008). With this new information, it can be assumed that Miller and Urey then understood the complexity of life’s origins, so they began to reconsider the claims that they had made in the past. Science is designed so that even if individuals are biased, the methodologies, institutions, and practices remain largely unbiased. Urey could clearly see through the Miller-Urey experiment that life was an incredibly complex field to study scientifically and was not a simple field of research.

Nevertheless, in 1952, Miller and Urey’s work seemed to be a pioneering experiment on the study of the origin of life as it was the first experiment to highlight a potential molecular origin for life. Some scientists such Jeffrey Bada and Eric Parker have argued that the Miller-Urey experiment caused a paradigm shift in the field of prebiotic chemistry as it radically changed how essential concepts (on the origin of life) were understood or framed. This report will explore a variety of different scientific experiments on the origin of life to see if this judgement is correct.

Parker and Bada’s modifications of the Miller-Urey experiment:

The main criticism made by scientists such as of [AB10]  the Miller-Urey experiment was that the reducing gases that were used in the experiment (H2, H2O, CH4, and NH3), [AB11]  would not have been the most common gases that were found in the atmosphere of early Earth. Instead, rock analysis suggests that Earth’s early atmosphere would have been mainly comprised of weakly reducing gases such as carbon dioxide (CO2) and nitrogen (N2), as well as a small percentage of the four gases that Miller and Urey used in their original experiment. Doctor Scott M. Huse, author of “The Collapse of Evolution” (p.153) said, “The concentrations of methane and ammonia were carefully selected to ensure the production of organic molecules. There is no evidence to suggest the Earth’s atmosphere was so characterized.” (Huse, 1986) Research involves analysing the data that is stored in databases to look for unique patterns and events to deduce areas of improvement or further experimentation. As a result in 1983, after this issue was highlighted, Stanley Miller attempted to modify his original approach with a mixture of gases that would more accurately represent the gases that would have been present in Earth’s early atmosphere[AB12]  Applying the same method, Miller used a mixture of gases that was largely made up of carbon dioxide and nitrogen, but this time a colourless liquid containing few amino acids, instead of the “brown broth” rich in amino acids, had formed. (Fox D. , 2007)[AB13] 

Despite the disappointing findings, Miller can be credited on the thoroughness by which he was able to record their results and archive the components of their experiments. The role of a scientist when carrying out experimentation is to make the data clear and available to other researchers. The data, which is then stored in databases, can be subsequently reviewed in the objective view of another scientist. In the case of Jeffrey Bada and Eric Parker, it was then easy for them to review Miller’s work and apply their modifications because Miller made a conscious effort to preserve the data and results of their experiments. Bada and Parker’s own findings on the Miller-Urey experiment were placed into the peer-reviewed journal “Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment”, under the Proceedings of the National Academy of Sciences of the United States of America. Under this organisation, it was checked by anonymous, unbiased scientists[AB14]  As well as this, the paper was cited a total of 147 times by other researchers, according to the PNAS.  This suggests that it is a reliable [AB15]  source of information for this investigation.

Upon reviewing Miller’s 1983 experiment, Bada had discovered that nitrates, which destroyed the amino acids, had formed as a result of the chemical reactions that were taking place. The nitrates were also turning the water acidic, preventing the production of amino acids. To resolve this, Bada added iron and carbonate bases (minerals that would have been present on primitive Earth), to the experiment, to neutralise the nitrates and the acidic solution (Fox D. , 2007) [AB16]  Although Bada ended up with a solution that looked similar to Miller’s initial results, after a chemical analysis of the solution was taken, the solution was found to be full of amino acids. Through this study, Bada showed that the procedure and the mechanism that was outlined by the Miller-Urey experiment was still accurate because amino acids could still be formed by just using a combination of carbon-rich gases and minerals that were found on primitive Earth. This shows that the Miller-Urey experiment still provided an accurate representation for how complex organic molecules needed for life could be formed from simple inorganic compounds.

As well as this, Parker showed that the Miller-Urey experiment was a lot more valuable to scientists than people had originally thought. It can often be easy for scientists to miss important findings, due to the limitations of their time and for Miller and Urey, it was particularly difficult for them to understand the significance of their results because they did not have the technology that was sophisticated enough to obtain this knowledge. However, the recent growth in computing power and sensor technology, has allowed scientists to revisit past work to check the accuracy of the results. Looking through Miller’s past experiments, Parker found an archived set of results from an experiment that was conducted in 1958, where the gases CH4, NH3, and CO2, combined with H2S, were used to simulate Earth’s early atmosphere. The paper chromatography methods that Miller was originally using could only detect a limited number of organic molecules. However, Parker applied a more modern technique through using high-performance liquid chromatography-UV fluorescence detection. With this method, Parker was able to detect the presence of 23 amino acids, as well as 4 amines from Miller’s 1958 silent discharge experiment (Bada, 2011).

There are 20 amino acids that are essential for life. They are proteinogenic, meaning that they make up the genetic code of all living organisms. When analysing the graph of Miller's results from his 1958 silent discharge experiment, 10 of the essential amino acids: Alanine, Glycine, Serine, Threonine, Aspartic acid, Valine, Glutamic acid, Methionine, Isoleucine and Leucine, were found in the data. Although not all the essential amino acids were detected, the majority were still present, suggesting that the Miller-Urey experiments were pioneering for scientists studying the origins of life because the results proved to be more significant than originally expected.

Through observing Miller’s past experiments, Bada was able to apply the correct set of gases and minerals to the Miller-Urey experiment and achieve the same results as the original experiment. As well as this, Parker was able to show that there were more amino acids and amines in the 1958 silent discharge experiment, than initially recorded by Miller. Bada and Parker’s experiments and analyses are one piece of evidence to suggest that the Miller-Urey experiment did create a paradigm shift in the way that scientists understand the origin of life. It shows that the method used by Miller and Urey was fundamentally correct as it was still able to produce the organic molecules, with the correct combination of gases and minerals, and 5 more of the essential amino acids needed for life were detected in one of Miller’s original set of results.

Formation of nucleobases in a Miller-Urey reducing atmosphere:

In a recent study, a group of Czech scientists had attempted to highlight the significance of the original Miller-Urey experiment. The group of scientists had identified that the main issue to do with the original Miller-Urey experiment was that the gases that were used in the experiment were considered “too reducing” (Packham, 2017) so[AB17]  they attempted to test the Miller-Urey hypothesis of abiogenesis[AB18]  in a reducing atmosphere,[AB19]  using a mixture of simple reducing gases, to see whether this had an impact on the results. The Czech study is a reliable source of information for this investigation because the findings that were made by the scientists were placed into a peer-reviewed journal where they were checked by anonymous, unbiased scientists. However, considering that this source of information has been peer-reviewed and, it has only been cited 74[AB20]  times according to the Proceedings of the National Academy of Sciences of the United States of America, which could suggest that other researchers may not have found it reliable. This could discredit the information.

Instead of using a more complex mixture of reducing gases such as H2, H2O, CH4, and NH3, the scientists used a mixture of simple reducing gases which consisted of NH3 + CO and H2O (Ferus, 2017).[AB21]  As well as applying the electric stimulation to the water vapour, the scientists also applied powerful laser discharges to replicate the plasmas resulting from asteroid impact shock waves (Packham, 2017). This was something that Miller and Urey could not replicate during their time because technology was not yet advanced enough to have access to equipment such as lasers. This was technology that the Czech scientists did have access to and so took full advantage of in order to improve the results. The recent growth of computing power has allowed people such as the Czech scientists, to represent a hypothesis or scenario more accurately and thus generate more accurate results.

The[AB22]  difference in gases combined with the extra energy source, was not only able to produce amino acids but also formamide and hydrogen cyanide (HCN). In the past, experiments had suggested that formamide and HCN, at high temperatures under UV light, had served as intermediate stages in the creation of RNA nucleobases, the building blocks of RNA and DNA (Packham, 2017). The emission spectrum of the Czech scientist’s experiment using a reducing atmosphere consisting of NH3, CO, and H2O,[AB23]  detected HCN at an emission intensity of 2x107 arbitrary units, which shows that a detectable amount of HCN, a key component in the creation of RNA nucleobases, was created.[AB24]  The spectrometer also detected trace amounts of formamide. Although HCN and formamide are not presented in abundance according to the spectrographs, the Czech study still proves that with a reducing atmosphere, using the same system as the Miller-Urey, the experiment has the potential to create formamide and HCN. This could suggest that similar processes may have occurred on primordial Earth. Moreover, before the research had been conducted by the Czech scientists, it was thought that formamide came from exceptional sources such as comets, chemistry in interstellar space, and reducing atmospheres (Ferus, 2017). Not only were the scientists able to show that by applying powerful laser discharges to a reducing atmosphere, molecules such as formamide and HCN could be produced, but they had also shown that these molecules could also be curated through abiogenesis, the theory supported by Miller and Urey.

It is because of scientific collaboration that the Miller-Urey experiment could be clarified. The global interchange of information has allowed the Czech scientists to review and apply a different perspective to the experiment, and thus exemplify its significance. Although the Czech scientists had made some minor modifications to the original experiment, the process had largely remained the same because a source of energy was still applied to a mixture of reducing gases and a mixture of organic molecules were created. Furthermore, the results of this experiment were higher yielding which implied that the Miller-Urey experiment was a lot more significant to scientists than people had originally thought at the time. Nick Lane, Professor of Evolutionary Biochemistry in the Department of Genetics, Evolution and Environment at the University College London said, “Amino acids are old hat and are a million miles from life.” However, the fact that formamide and HCN, specialised organic molecules that aid in the formation of RNA nucleobases, were created using a similar method to that of the original experiment, showed that the Miller-Urey experiment pioneered scientist’s understanding of the origin of life. The Czech study is yet another piece of evidence to suggest that the Miller-Urey experiment might have created a paradigm shift in the way scientists understood the origin of life because they proved that the process outlined by the experiment formed the fundamental basis of the study into the origin of life.

Hydrothermal vents in the production of organic molecules:

As Jeffrey Bada and Eric Parker had analysed, although a reducing atmosphere that was composed of H2, H2O, CH4, and NH3 was used in the Miller-Urey experiment, rock analysis now suggests that the atmosphere of early Earth was primarily made up of a more neutral combination of carbon-rich gases. Bada had highlighted the importance of minerals, such as iron and carbonate, in neutralising the acidity of the solution produced and allowing organic molecules to form as a result. This was how Bada was able to produce amino acids in an atmosphere of weakly reducing gases that were made up of primarily carbon dioxide and nitrogen. However, astrobiologists have now formulated a new potential origin for life and that is hydrothermal vents on the ocean floor, that are created when geothermically-heated water escapes from a crack in the oceanic crust (Joseph, 2017). To some, they are the best place for life to form because the fluid that leaves the rifts in the oceanic crust, mixes with the water from the ocean, as well as the minerals from the hydrothermal vents, and the extreme conditions allow chemical reactions to take place that produce organic molecules (Condie, 2005). This means that instead of the energy source of the experiment being the electric or the laser stimulation, the energy of the experiment would come from the hydrothermal vents[AB25]  themselves.

Scientists spend a considerable amount of time reading the published results of other scientists, seeing what they can objectively bring to the experiment that the original scientists did not include. The growth of computing power has allowed scientists to derive new understandings of certain areas of science. With the advent of modern technology, scientists are now able to use powerful sensor technology to detect the rock minerals inside hydrothermal vents and analyse their significance in the study into the origins of life.

Scientist, Lauren White, at NASA’s Jet Propulsion Laboratory, alongside her supervisor, JPL scientist, Michael Russel and the rest of her colleagues, created an experiment to try and determine if hydrothermal vents could have been a potential source of life. This particular study into the origins of life is reliable because the findings were placed into a peer-reviewed journal, where it was checked by anonymous, unbiased scientists. This makes it a reliable source of information for this investigation.[AB26] 

In their experiment, the team of scientists brought together hydrogen-rich water (to simulate the water that escaped the hydrothermal vents), seawater enriched with carbon dioxide, as well as a few minerals that would have been present in the environment at the time, to see if any organic molecules could form (NASA, 2020). In a previous experiment, White had observed that water flowing through rocks in the hydrothermal vents, could produce iron sulphides, a catalyst that could reduce the energy required for the hydrogen and the carbon found in the water, to combine (NASA, 2020). This was one of the minerals that were included in the experiment. The scientists could not replicate hydrothermal vents that allowed high temperature water to escape in the laboratory setting, so instead the scientists aimed to copy as accurately as possible, the hydrothermal vents that released water at around 100°C. To mimic the motion of the fluids in the experiment, the scientists had to simulate deep-sea conditions (approximately 1km below the ocean surface) by using multiple high-pressure chambers, installing a blast shield in between them and the experiment, so that they could safely observe the results (NASA, 2020).

The results of the experiment were not the amino acids that Miller and Urey were able to create in their experiment, but a prerequisite to these complex organic molecules. In their resulting solution, the scientists had found formate and trace amounts of methane (NASA, 2020). These are both simple organic molecules as they both contain at least one C-H covalent bond. However, these molecules still do not provide strong enough evidence to suggest that life could have evolved from hydrothermal vents as these are only simple organic molecules being created. Miller and Urey benefitted from having a more varied sample of inorganic gases to begin with and however inaccurate these gases were to that of the original atmosphere at the time, they were still able to provide a direct pathway to the creation of complex organic molecules like amino acids. Even with the modifications applied by Parker, Bada, and the Czech scientists, complex organic molecules were still formed using a similar method to that of the original Miller-Urey experiment. In this regard, there is still more research to be done to show that life could have evolved from hydrothermal vents, and White’s analyses therefore does not completely discredit the Miller-Urey experiment.

Furthermore, although the sources of energy and the elements of White’s experiment were different to that of the Miller-Urey experiment, the process that led to the eventual creation of organic molecules, had remained largely the same because a hydrous mix of inorganic compounds reacting together with an energy source to create organic molecules. This showed that the system outlined by the Miller-Urey experiment was fundamental as it was used as a basis for other experiments in the study for the origin of life. The fact the Miller-Urey experiment not only proved that the origin of life could be studied in the laboratory setting but was also replicated in alternate forms by other scientists, suggests that the experiment did create a paradigm shift as it radically changed the way that scientists “framed and understood” the “essential concepts” of the origin of life.

The Panspermia theory and the Murchison Meteorite:

It has been argued that the most contrasting theory to that of the Miller-Urey experiment, in the study of the origin of life, is the Panspermia theory. The Panspermia hypothesis suggested that the “seeds” of life, which were already embedded in the universe, were transported to Earth via extra-terrestrial forces (Fizbit, 2008). Panspermia, from its ancient[AB27]  Greek origins, means “all seed” and the hypothesis was first formulated by the Ancient Greek philosopher, Anaxagoras, in the 5th century BC. Originally, panspermia was a hypothesis because it was an observation of how life came to be on Earth, that was not supported by much evidence or data from experimentation. However, panspermia is now considered to be a theory because the hypothesis has been tested through the works of scientists such as British biologist, Francis Crick.

The Miller-Urey experiment explored the possibility of life beginning on a terrestrial level, with inorganic molecules found on Earth, reacting together to make organic molecules, the first building blocks of life. However, the Panspermia hypothesis provided an alternative view to the experiment, that life could have begun on an extra-terrestrial level, with amino acids being transported from space to Earth via comets, asteroids, meteorites, and interstellar dust particle. Most scientists believed in the Panspermia theory because the Miller-Urey experiment produced a mix of organic molecules that were still not diverse enough to create life at Earth’s current level of complexity. Also taking into consideration the age of the Earth, some scientists speculate that DNA or molecular based life, as depicted by the Miller-Urey experiment, could have evolved within the Earth’s lifespan. Therefore[AB28] , Earth may have needed an external source to create the complex organisms that can be seen today (Kaufman, 2017).

In 1969, a meteorite exploded in the atmosphere just above Murchison, Victoria in Australia (Matson, 2010). I have used the Murchison meteorite to discuss the Panspermia theory because it can provide detailed evidence to show whether the theory is valid (Koberlein, 2015).[AB29]  However, unlike the other sources of information in this essay which were all in the form of experiments, the findings from the Murchison meteorite have not been peer-reviewed and therefore might be invalid.

This meteorite was significant because a chemical analysis of the rock showed that it carried over 70 different types of amino acids, the building blocks of life. Dr. John Lovering at the University of Melbourne had detected a strange smell coming from one of the sealed tubes that contained a fragment of the meteorite, recalling the odour to be of a similar smell to methylated spirits. He concluded that the meteorite was a rare carbonaceous chondrite, the only type of meteorite that could carry organic molecules. (Smith, 2019) The discovery of the amino acids on the meteorite was significant because it showed that these molecules that were needed for life, could survive the extreme heat generated from the impact of the meteorite hitting the Earth, thus suggesting that these organic molecules could have transported to primordial Earth via external sources.

Francis Crick and British chemist Leslie Orgel proposed the bold hypothesis that these organic molecules were purposefully transported to Earth by intelligent extra-terrestrial organisms, since it was previously said that life could have emerged twice within the evolution of the universe (Orlic, 2013). As well as this, Crick and Orgel also believed that it was possible that the seeds of life could be carried safely from planet to planet via comets and asteroids. Crick is a credible scientist who in 1962, alongside James Watson and Maurice Wilkins, won the Nobel Prize in Physiology and Medicine for his work identifying the helical structure of DNA. However, although Crick’s expertise was in the field of genetic evolution and biology, his claim on Directed Panspermia lacks credibility because whilst it is possible that RNA could be transported to different planets, the probability that a civilization of advanced intelligence was created within the age of the universe is still fairly low. Crick’s claims and the Panspermia theory do not abide by Occam’s Razor, that “the simplest explanation is usually the best one” (Wikipedia, 2001) because the theories are too complex to override any other view on the origin of life.

Eric Parker’s chemical analysis of the samples from Miller’s 1958 experiment, detected the presence of 23 amino acids, as well as 4 amines, far more than the 5 that Miller had originally detected. However, the fact that 70 amino acids were found on the Murchison meteorite suggests extra-terrestrial parameters, if they were not the singular origin of life, could have helped to provide a more diverse mixture of amino acids, leading to the creation of more complex organisms.

However, the Panspermia theory, as represented by the Murchison meteorite, still does not discredit the Miller-Urey experiment. It is still possible that the amino acids found on the Murchison meteorite could have still been created through a process that is similar to the one outlined by the Miller-Urey experiment. Inorganic molecules that were originally found on the meteorite would have been exposed to the UV light in space and may have therefore reacted together to make organic molecules like amino acids. This still follows the process outlined by the Miller-Urey experiment that a source of energy allows inorganic molecules to react together to make organic molecules like amino acids. This proves how influential the Miller-Urey experiment was in the study of the origin of life.

Conclusion:

The scientific study into the origins of life did not happen until the beginning of the 20th century because for most scientists, the origin of life was too broad and complex of a study, to analyse within the confines of a laboratory. Hence why, before the advent of scientific ideas such as the Oparin-Haldane hypothesis (which in turn initiated the Miller-Urey experiment), most ordinary people looked at the origins of life from a very creationist perspective because it supported their view of the world. The only other scientists who attempted to deviate from the creationist view, were people like biologist Francis Crick and chemist Leslie Orgel, who provided an alternative perspective from their observations, through the Panspermia Theory. However, few ultimately believed in this hypothesis because the chances of it being true were sufficiently low. To prevent a bias of opinion, most scientists question all information before choosing to accept the validity of the information. They adopt a sceptical attitude towards claims, and they suspend all judgement until they have good reason to believe a claim to be true or false. In the case of the claims delivered by Francis Crick and Leslie Orgel, despite generally being credible scientists, many found reason to reject their arguments. Hence, the Miller-Urey experiment was the test that presided that view.

From my research, I can deduce that the Miller-Urey experiment did have a significant impact on the way modern prebiotic explanations and experiments are either framed or carried out today. Both Parker and Bada’s experiment, as well as the Czech study, proved that the Miller-Urey experiment was still accurate because even with a carbon-rich and less reducing artificial atmosphere, complex organic molecules such as amino acids and RNA nucleobases had formed. Parker, Bada, and the Czech scientists used experimentation to obtain evidence in the form of data. The data and the outcomes of these experiments were used as further evidence, supporting the Miller-Urey experiment. This strengthened the argument put forth by Miller and Urey, suggesting that the scientists did create a paradigm shift in our understanding of the origin of life.[AB30] 

Although White’s hydrothermal vent experiment and the Panspermia theory proposed a different origin of where life began, however contrasting the theories were, they still do not disprove the Miller-Urey experiment. The mechanism of inorganic compounds combining through an energy source to make more complex organic molecules, could still have occurred in the hydrothermal vents or whilst the meteorites that collided with Earth were still in space. This only strengthened the argument proposed by Miller and Urey. The role of a scientist is to carry out experiments and place their findings into databases to make them available to other researchers. It has become clear from my research that Miller’s meticulous storing of evidence and data, has allowed scientists such as Parker and White to build upon the original experiment accurately, showing to the rest of the scientific community that the experiment was significant in launching the scientific study into the origins of life.

As stated in the beginning, Thomas Khun’s definition of a paradigm shift is “a fundamental change in approach or underlying assumptions.” The studies that were conducted by Bada and Parker, the Czech scientists, and White, all attempted to challenge some of the inaccuracies that were present in the Miller-Urey experiment, but all came to the similar conclusion that the system that was outlined by the experiments, remained fundamentally correct. This showed that the experiment did create paradigm shift in the field of prebiotic chemistry because its validity reveals that organic molecules could be extrapolated from the inorganic chemicals that were present on primordial Earth, overturning underlying assumptions that this was not possible.

My overall research has been limited because the origin of life is still a complex field of study that scientists still do not have all the answers to. The Miller-Urey experiment outlined how inorganic molecules became complex organic molecules, but it still did not provide a detailed enough answer to explain how DNA was eventually formed from these complex organic molecules, nor did it outline how cells eventually evolved within the timeline of life. Thus, the idea of self-replicating RNA has become a new field of study that scientists are continuing to investigate. For the Miller-Urey experiment to be considered valid and significant, it would have to have formed the basis of the subsequent bio-chemical processes that led to the creation of life as it exists today but because the origin of life is so big and complex, as more research into this topic is still being conducted, it was difficult to determine this. This has meant that my research into the Miller-Urey experiment and the origins of life, has been limited because I had to start by focusing mainly on the early stages of the overall process. I would have to do further research into the topic to synthesise the main scientific consensus regarding the next stages in life’s evolution. However, this does not completely deny the significance of the Miller-Urey experiment as the results from the subsequent experiments that were later conducted by other scientists, suggest that the Miller-Urey experiment did have valid outcomes and initiated the scientific question regarding the origins of life overall. This shows that the Miller-Urey experiment was indeed very influential.

In the future I would hope to improve my investigation into the origins of life and the validity of the Miller-Urey experiment by exploring the current scientific research behind the evolution of more complex organic molecules which form the foundation of living organisms, to determine if the research supports or challenges the idea that abiogenesis provided a logical starting point to life. My initial research for this paper primarily focused on the experiments that were conducted by other scientists after and in relation to the Miller-Urey experiment, which enabled me to better understand how correct the judgements from the original set of experiments were, thus helping me to determine the significance of the experiment. Although I had to gather some of my contextual information regarding the history of the origin of life from Wikipedia pages, I was able to incorporate a lot of scientific journals from other qualified scientists within my paper as well, which enabled me to come to an accurate conclusion regarding the significance of the Miller-Urey experiment. However, if I were to explore the origin of life topic more deeply, I would also review papers on topics such as the DNA theory and self-replicating RNA, to see if any parallels between this and the Miller-Urey experiment can be drawn on a broader scale.  Then it can be more accurately deduced as to whether the Miller-Urey experiment was significant enough to create a paradigm shift because if it did provide a logical starting point to life and the creation of DNA, it can begin to explain how the organisms that exist today, eventually came to be.

To be involved in science is to be involved in a community of inquiry, with common principles and methodologies. Through Parker and Bada, the Czech scientists, and White’s further research into the Miller-Urey experiment, using similar methodologies, these scientists were able to add to people’s knowledge on the origin of life. Although there were inaccuracies with the Miller-Urey experiment, the scientists discovered that the fundamental process that was outlined by the Miller-Urey experiment was still correct. The fact that modern scientists choose to support abiogenesis as the first steppingstone for further research, suggests that the Miller-Urey experiment was very influential in the field of prebiotic chemistry. This suggests that the Miller-Urey experiment did in fact create a paradigm shift in the way that scientists understand the origin of life.[AB31] 

Bibliography

Jeffrey L. Bada, E. T. (2011, February 14). Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment. Retrieved from Proceedings of National Academy of Sciences of the United States of America: https://www.pnas.org/content/108/14/5526

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