2. The Evolution of Molecules

2.0 Introduction

Organic chemistry is an arduous subject of study. The gigantic investigative effort put by Western civilization into the unraveling of the matrix of life leads to the conclusion that the original building blocks on which life is based are few and simple. Nothing of an apparent great complexity is build de novo, everything is composed of a series of simple and usually very similar subunits. These monomers, through a judicious assembly, may suddenly acquire new and unforeseen properties that favor survival and duplication. Evolution proceeds through a recurring pattern of convergences and divergences. Kuhn developed this concept in 19721.

We observed an embryonic form of this pattern in the evolution of atoms during the expansions and contractions of stars, and in primary stars reconstituting, after explosion, into enriched secondary stars. Such a pattern becomes more conspicuous in the evolution of more complex entities. Under a determined set of physical conditions, several living entities endowed with the same chance to survive in the environment are produced by random mutation from a master plan. When the external conditions change, only those entities that had acquired the hitherto unused capacity to survive the potential challenge (cold, heat, toxic substances, radiations and starvation) will displace more vulnerable entities. From a phase of divergence with the production of many different living forms endowed with the same survival potential, one moves to a phase of convergence where only the best fitted will remain. Once the superior entity has conquered the field, it will start diversifying again at random, occupying all niches available, until a new challenge selects those entities best able to survive it. This produces a new evolutive convergent phase.

Beside this fundamental process concerning the mechanism of evolving progress, there are two enigmas: firstly the scarcity of carbon in the atmosphere and waters of the earth that would justify the reliance on carbon for the evolution of living matter and, secondly, the need to have well defined conditions for the formation and durability of newly synthesized organic compounds, that could not endure under the harsh conditions prevailing initially on the surface of the earth, as we have described them.

Nearly one third of the condensed matter in the inner solar system is composed of oxygen, obtained by the fusion of helium. This oxygen is combined in water to hydrogen and in rocks to carbon under the form of carbonates of calcium and magnesium. Carbon is formed from helium more easily than oxygen and should be available in even greater quantities. The oxygen and carbon within rocks are not easily available for the synthesis of living matter and the availability of carbon in the water and the atmosphere has been consistently deemed scarce, although it is the prime source material from which life depends to blossom.

Nikonov Doklady2 was the first to point out the close association of helium with hydrocarbons in the earth’s crust, and Gold3 pointed out that the availability of carbon under the form of hydrocarbons and methane is vast, provided one looks for its presence within the earth crust, not at its surface. There is a substantial supply of useful carbon at great depths. This is evident from the presence of diamonds and hydrocarbons, whose vast supplies cannot possibly have all been formed from decayed organic plant and animal matter. Gold postulates a biosphere consisting of thermophilic microorganisms living in the earth crust at depths of a maximum 10 km, living at temperatures as high as 150°C. This biosphere would be comparable in mass and volume to all the surface life we know. The microorganisms would feed on hydrocarbons in combination with oxygen derived from iron oxides and sulfates, also present.

The chemistry of early life, taking place in a dry environment at high temperatures and high pressures that would liquefy components originally in solid form, would allow the appearance of complex molecules shielded from the disruptive conditions found on the surface, during primeval times. The chemical energy available inside the planet is then the first energy source that allowed the appearance of life. Surface creatures, which feed directly (plants) or indirectly (herbivores and predators of herbivores) on solar energy are, in this view, a secondary specific adaptation of life to the uniquely favorable circumstances existing on the earth’s surface.

This leads to the third hypothesis; namely that the Earth self-regulates at a state that is tolerated by life. There is a feedback between life and its environment. The Gaia theory elaborated by Lovelock4 proposes that organisms contribute to self-regulating feedback mechanisms that have kept the Earth’s surface environment stable and habitable for life. This Gaia hypothesis, i.e. the regulatory effect of life on its environment, will become conspicuous only when life has established itself.

References

1. Kuhn: Ang. Chem. Intern. Edit. 11: 798-820, 1972

2. Akadem Nauk SSSR, earth sciences Section 188: 199-201, 1969

3. Proc. Nat. Acad. Sc. US, 89: 6045-6049, 1992

4. The Ages of Gaia, 2nd ed., Oxford Univ. Press, Oxford, 1995

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