Origin of Life

Theories and evidence for chemical biopoieses

In the Beginning was Abiogenesis

In current biological terminology "abiogenesis" refers to the emergence of life as self-replicating assemblages of organic chemicals able to control chemical energy from non-life assemblages of chemicals. This is the hypothesis that primordial life originated within the first billion years of Earth's history as a result of chemical reactions that generated larger and larger organic polymers, which ultimately attained control of bioenergetics and the property of chemical self-replication. This modern conceptualization is reasonable in view of what is now known of the biochemical basis of all life.

The modern conceptualization replaces earlier notions of "spontaneous generation" that viewed life as arising fully formed from non-living matter, or de novo. Such Aristotelian notions of archebiosis probably arose because much of life exists at the microscopic level of prokaryotes and unicellular eukaryotes, and because some organisms living on detritus reach visible proportions after having been of microscopic size.

The term 'life' in relation to abiogenesis embraces the notion of utilization of energy sources and biochemical self-replication. This requires that an assembly of molecules and macromolecules acquired the ability to convert energy into growth and that informational macromolecules directed self-replication.

The processes that led from inorganic chemicals to the panoply of organic, carbon-based chemicals in primordial cells would have been governed by the non-random physical laws of chemistry, specifically those physical properties related to organic molecules. Since the processes involved would be widespread across the primordial planet, enormous numbers of molecules and macromolecules would have been generated in the first 10 billion years of Earth history. Because modern cells contain only L-amino acids, it is believed that a single primitive cell line, the universal cenancestor is the ancestor of all living cells. According to most theorists, conditions on Earth are no longer suitable for abiogenesis to occur. Unfavorable conditions apply because oxygen is 'toxic' to molecules.

The elucidation of abiogenetic mechanisms would be of enormous interest, yet this has not been a particularly active area of research because it has limited applications. The advent of space exploration has infused life into Astrobiology and the search for the Origin of Life.

The lack of a full scientific explication for abiogenesis does not mean that chemical evolution was not the origin of life. Rather, the difficulty in deciding between theoretical scenarios reflects difficulties in recreating conditions and the impossibility of recreating the time frame for biopoiesis. Certainly, biopoiesis is a much better explanation than the God of the Gaps, which is merely simplistic magic-thinking.

From NASA's Astrobiology Institute
Spitzer Telecope Data Suggest that Life's Building Blocks are Abundant
Finding Life in Mars Analog Sites on Earth
More on Astrobiology:
Evolution and Ecology Beyond the Planet of Origin
Evolution and Development Workshop
Evolution and Ecology Beyond the Planet of Origin
Evolution and Development Workshop
New York Center for Studies on the Origins of LifeAd Astra Magazine: Astrobiology Issue (January/February 1999)
The Astrobiology Web
Free audio on WAMC's Origins of Life Segments
Origins on Abiogenesis
Recommended on the Talk Origins Archive:
Lies, Damned Lies, Statistics, and Probability of Abiogenesis Calculations
Borel's Law and the Origin of Many Creationist Probability Assertions
Spontaneous Generation and the Origin of Life

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