The model further assumes that coenzyme-like molecules (CLMs) changed surface properties of oil droplets (e.g., by oxidizing terminal carbons), and in this way, created and sustained favorable conditions for their own self-reproduction. Here, I argue that primordial life had no nucleic acids instead, heritable signs were represented by isolated catalytically active self-reproducing molecules, similar to extant coenzymes, which presumably colonized surfaces of oil droplets in water. However, the mechanisms of primordial heredity were different from those in contemporary cells. The origin of life means the emergence of heritable and evolvable self-reproduction. Sharov, in Habitability of the Universe Before Earth, 2018 Abstract A detailed experimental and theoretical study of the origin of life was now possible.Īlexei A. These two discoveries meant that we had both a plausible way of generating simple organic building blocks and an understanding of the macromolecules on which life depends.
In the same year, Crick and Watson published their structure for DNA, the first step in elucidating the fundamental molecular basis of life. Miller speculated that this was how organic compounds had been made on the early Earth. The experiment produced a mixture of several amino acids, the building blocks of proteins. Stanley Miller, then a graduate student working in the laboratory of Harold Urey, set up his famous experiment in which electrical discharges were passed through a mixture of gases (methane, ammonia, hydrogen, and water vapour) simulating a thunderstorm on the primitive Earth. Oparin and Haldane in the early twentieth century developed the idea that chemical reactions on the early Earth could have led to the production of a range of organic compounds, forming a ‘primordial soup’ in which the required building blocks for life would have been present.īut it was not until 1953 that these ideas received experimental support. If (and oh! what a big if!) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity present, that a protein compound was chemically formed, ready to undergo still more complex changes…. While the subject of the origin of life is hardly mentioned in Darwin's published writings, the following quote (from a letter to his botanist friend Joseph Hooker) gives us an inkling of his thoughts on the subject at that time: This allowed the idea that all life, simple and complex, had a single origin in the distant past. Simple organisms can be as evolutionarily successful as complex ones. In Darwin's theory there is not necessarily a ladder of progress from simple to more complex forms. Lamarck's ideas were criticized by scientists such as Cuvier ( see FAMOUS GEOLOGISTS | Cuvier) (in a celebrated debate with Geoffroy Saint-Hilaire in 1830) and later by Pasteur, who carried out his famous ‘swan-necked flask’ experiments to discredit the idea of spontaneous generation.ĭarwin's theory of evolution by natural selection opened the way for the modern view of the origin of life ( see FAMOUS GEOLOGISTS | Darwin). Thus, the ideas of transformism (evolution) and spontaneous generation were closely linked in the early nineteenth century and put Lamarck and his followers in conflict with the religious and scientific establishment, who argued for the immutability of species, which were divinely created in their current forms. The observation that both simple and complex organisms are currently present therefore required that simple organisms are appearing even today from inorganic matter by a process of ‘spontaneous generation’ (a concept that has its origins in antiquity). Early ideas on the evolution of life were most clearly expressed by Lamarck, who described the process as one of progression from simpler to more complex and advanced forms ( see EVOLUTION). The idea that all life on Earth has a common origin became well established only in the twentieth century.
Bailey, in Encyclopedia of Geology, 2005 Development of Ideas on the Origin of Life
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