|MadSci Network: General Biology|
Observational science DOES explain the origin of life from non-living substances, in the form of hypothesis and theory (more on that later). Now, if the question were can observational science PROVE that how life derived from non-living substances, that is tougher. Short of a time machine (never say never) to actually go back and observe this may well be impossible. THE THEORY Many scientists have worked for decades and results support the chemosynthetic theory of the origin of living cells from pre-biotic substances. This theory states that under the right circumstances, non-organic molecules can randomly, with addition of energy in the form of UV or electricity, form simple organic molecules such as amino acids (the building blocks of proteins). Experiments done in the lab by Stanley Miller and Harold Urey (Miller, 1959) demonstrated that this is indeed possible. Under the right conditions, these amino acids may combine to form simple peptides. Some of these peptides do have biochemical activity (this is the nature of peptides) and, it is thought, some had a crude capacity to mediate copying of themselves. Thus began pre-biotic evolution. You can see how such peptides would quickly predominate, and how more efficient versions would be able to replace less efficient. The details of pre-biotic evolution are still being worked out and only some of the proposed "steps" have been replicated in the lab, hey but that's a good start! Gradually, nucleic acids, randomly formed from organic precursors that must have been generated much like amino acids, gained from association with peptides and with lipids, and primitive pre-biotic "cells", wherein the nucleic acids could help the peptide synthesis and perhaps vice-versa became prominent. Now, it is just a short leap to life; these pre-biotic organized macromolecules had to develop the ability to grow and convert energy or food into growth (metabolism), the ability to adapt to acute changes in environment, the ability to reproduce and the ability to adapt to chronic changes in environment by natural selection. These abilities separate the living from the non-living, but the living likely "evolved" from the non-living via chemosynthesis. Now, can science prove this? Even if we could duplicate every step in the lab, some people would still not believe this is the proper explanation for the origin of life. Nevertheless, these theories seem the best explanation of the HOW life formed that we have. Science cannot and does not attempt to address the WHO DONE IT aspect of the origin of life. Leave that to your friend. MILLER SL, UREY HC. Organic compound synthesis on the primitive earth. Science. 1959 Jul 31;130(3370):245-51.
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