5 - The emergence of life

Summary

The emergence of life is an expected phase transition from a collection of polymers which do not reproduce themselves, to a slightly more complex collection of polymers, which do jointly catalyze their own reproduction.

Stuart A. Kauffman, The Origins of Order, 1993

Evolution toward a growing complexity and organization is the result of fluctuations that lead to a gradual acquisition of autonomy from the environment.

G. Nicolis and I. Prigogine, Self-Organization in Non-equilibrium Systems, 1977

The origin of the biosphere

The biosphere is the ensemble of the life-supporting regions of the terrestrial globe. It is made up of the oceans and fresh waters, plus the atmosphere and the layer of soil (spread over the continents) that contains organic matter. Water is the predominant component of the biosphere, in which the atmosphere plays an important role, and where the many compounds of carbon are essential because they are needed by life. In the outer crust of the Earth, however, inorganic carbon is by far the most abundant component, in the form of carbonates (limestone, dolomite, etc.). Heat easily decomposes carbonates and frees carbon in the form of carbon dioxide (CO₂); thus this process is the principal source of volcanic CO₂.

For a long time, the origin of the biosphere remained a mystery, because no fossil trace exists from the first billion years of the Earth's evolution.