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Assembling LifeHow Can Life Begin on Earth and Other Habitable Planets?$
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David W. Deamer

Print publication date: 2019

Print ISBN-13: 9780190646387

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780190646387.001.0001

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Testing Alternative Hypotheses

Testing Alternative Hypotheses

Chapter:
8 Testing Alternative Hypotheses
Source:
Assembling Life
Author(s):

David W. Deamer

Publisher:
Oxford University Press
DOI:10.1093/oso/9780190646387.003.0013

Narratives related to the origin of life all incorporate the assumption that the first living microorganisms emerged in a sterile planetary surface after the ocean condensed over 4 billion years ago. This means that even though global conditions can be deduced from our growing understanding of planetary science and the early solar system, laboratory simulations of localized prebiotic sites remain the only way to guide virtually all of the attempts to reproduce the chemical and physical processes by which life could emerge. Because simulations are used to test the hypotheses described in this book, it seems essential to review representative examples and consider their strengths and limitations. Laboratory simulations of the prebiotic environment incorporate specific sets of factors chosen to reflect what we can deduce about the atmosphere, lithosphere, and hydrosphere of the early Earth and Mars. This chapter attempts to sort out the main factors that are incorporated into simulations. These can be conveniently divided into the drivers—physical and chemical processes—and the emergent complexity that is a product of the drivers. In order to describe a given system, it is helpful to first provide abbreviations for the component factors that define the degree of complexity, then compare that complexity to the complexity that seems to be required for life to begin, as is done in the next section. Questions to be addressed: What factors and assumptions provide a foundation for a given simulation? How do the factors interact to produce increasing complexity? How can the factors guide the design of experimental approaches? What combination of factors would be an adequate simulation of the prebiotic condition? Laboratory investigations related to origin of life research often begin with mixtures of simple organic molecules assumed to be available on the prebiotic Earth. These are then allowed to undergo reactions driven by a source of energy, either impinging on the system such as ultraviolet light or electrical discharge or contained within chemically activated compounds that can undergo spontaneous reactions. The mixture typically becomes more complex in some interesting way, such as the synthesis of polymers described in earlier chapters.

Keywords:   Miller, Stanley, feedback loops, prebiotic simulations

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