Abstract
Earth's 4.5-billion-year history has witnessed a complex sequence of high-probability chemical and physical processes, as well as 'frozen accidents'. Most models of life's origins similarly invoke a sequence of chemical reactions and molecular self-assemblies in which both necessity and chance play important roles. Recent research adds two important insights into this discussion. First, in the context of chemical reactions, chance versus necessity is an inherently false dichotomy-a range of probabilities exists for many natural events. Second, given the combinatorial richness of early Earth's chemical and physical environments, events in molecular evolution that are unlikely at limited laboratory scales of space and time may, nevertheless, be inevitable on an Earth-like planet at time scales of a billion years.This article is part of the themed issue 'Reconceptualizing the origins of life'.
Highlights
Chance or necessity? Are profound cosmic transitions reducible to this stark choice, or is such a polarized rsta.royalsocietypublishing.org Phil
Most mineral species are extremely rare, identified from five or fewer localities worldwide. These seldom-seen mineral species are rare for a variety of reasons [18], but most of them arise only in a restricted environment with an improbable combination of physical and geochemical conditions—environments that may occur on only a small fraction of all terrestrial planets
We suggest that terrestrial planets, owing to their vast spatial and temporal scales, as well as their stunning diversity of near-surface physical and chemical environments, have the potential to sample immense ranges of chemical reaction ‘space’
Summary
Chance or necessity? Are profound cosmic transitions reducible to this stark choice, or is such a polarized. Others countered with the view that life is a cosmic imperative—an inevitable consequence of the chemical and physical environments of warm, wet terrestrial planets [3,4]. Two quantitative concepts, both inspired by consideration of the origins of life from a physical sciences perspective, may help to inform this discussion. Life’s origin was a sequence of steps—chemical reactions and molecular self-assembly—each of which added structure and complexity to Earth’s near-surface environment. Some physico-chemical conditions necessary for mineral-forming reactions to occur are more probable than others; a stark division of such natural processes into chance versus necessity is an inherently false dichotomy. Again, that framing life’s origins in the polarizing context of ‘chance versus necessity’ creates a false dichotomy
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