How Lifes Asymmetry Originated

Theories on the origin of life's handedness are to a specific degree of a hypothetical character, as the evolution that lead to its formation cannot be repeated in a 1:1 experimental timescale. But in the past few decades our idea of how biomolecular homochirality evolved has advanced from highly speculative musing to a true scientific theory with a firm base in hard facts. Precise environmental conditions able to generate this essential biomolecular parity violation are of particular interest.

Primarily, we are confronted with the alternative between "terrestrial" theories that describe the process resulting in biomolecular asymmetry as evolutionary reactions which took place on early Earth during specific steps of chemical and/or biological evolution and "extraterrestrial" models that use chiral agents from outside Earth to explain the origin of biology's homochirality. Second, homochirality related research distinguishes between random mechanisms (Sect. 1.3.1) on the one side and determinate mechanisms (Sect. 1.3.2) on the other side (Bonner 1991). Furthermore we might ask: was the choice between left and right internally imposed by the system or externally imposed by some peripheral driving force? The main theories that have been developed to explain an abiogenic origin of the biomolecular chiral purity in terms of the physico-chemical processes involved are summarized in Fig. 1.1. They are highly controversial.

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