JTW's Evolutionary Origins - Author: Wood, John T.

Historical Stages in the Origin of Life

Recent Advances in the theoretical and experimental aspects of OOL research, as well as massive amounts of genomic sequence data, have reinvigorated and sharpened the focus of OOL studies.

The classic vision of heterotrophic organisms emerging from a vast prebiotic soup rich in high-energy organic compounds is giving way to a new vision in which life proceeds thru a series of distinct historical stages.

Each of these stages represents both a historical progression and a consolidation of the chemistry of the primary cellular processes.

Many of these stages have been presented as if they were actually modelling "the" origin event itself.

Careful analysis reveals that they are actually concerned with the origin of the various components that are necessary for the emergence of a functional cellular organism.

These theories provide important contributions to an overall theory of life's origins that should lead from the inorganic chemistry of the Hadean thru to the emergence of modern cells and their respective biochemistries in the early Archean.

The first stage in lifes evolution is represented by the structured formation of the basic organic compounds necessary for the systhesis fo the biological monomers.

These monomers must be derived from either a pre-existing stock (as in heterotrophic soup theories) or from scratch (as in autotrophic theories).

Heterotrophic origins require that a metabolic network, capable of generating monomers, emerge before the original stock of pre-exisiting monomers is depleted.

Autotrophic origins assume that the initiation of a network autocatalytic metabolism leads to a reliable means of producing the monomers from C₁-units such as carbon dioxide (CO₂) or methane (CH₄).

Traditionally heterotrophic origins have been assumed on the basis that heterotrophic metabolic organization is generally much more simple than that of the autotrophs.

When it was thought that the early atmosphere was highly reducing, the heterotrophic assumption was reasonable because these conditions are conducive to the formation of high-energy organic compounds.

With the advent of more recent data, the position has become untenable.

The early atmosphere is now thought to have been mildly reducing, perhaps not reducing at all.

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