Origins of Life
(Updated: February 17, 2004)
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How did life arise on planet Earth? There are a number of theories that attempt to explain how life originated. The biggest problem with all origins of life theories is our ignorance of early Earth conditions. For example, what kind of atmosphere was present on early Earth? There are two possibilities: (1) Early Earth had either a highly reducing atmosphere (i.e. it was made of molecules or "reducing agents" that could reduce other molecules by readily donating electrons), or (2) it had a "less" reducing atmosphere (i.e. molecules that were less effective at reducing other molecules). The atmospheric composition must have played an important role in chemical evolution that led to the origin of life on Earth. Once simple chemical reactions reached equilbrium, more complex molecules had to be generated somehow, with an input of energy, for life to arise. What kinds of energy sources were available to drive unfavorable reactions? There must have also been some sort of concentrating mechanism that allowed certain molecules to accumulate and reach critical concentrations in localized areas -- this would have been necessary for early cellular metabolism. How would a barrier (i.e. a lipid membrane) allow cells to take up the necessary molecules for their survival? Many questions remain unanswered, but the quest for knowledge in elucidating the mechanisms that led to the origins of life continues on.
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