Abstract
Although the cellular microorganism is the fundamental unit of biology, the origin of life (OoL) itself is unlikely to have occurred in a microscale environment. The macrobiont (MB) is the macro-scale setting where life originated. Guided by the methodologies of Systems Analysis, we focus on subaerial ponds of scale 3 to 300 m diameter. Within such ponds, there can be substantial heterogeneity, on the vertical, horizontal, and temporal scales, which enable multi-pot prebiotic chemical evolution. Pond size-sensitivities for several figures of merit are mathematically formulated, leading to the expectation that the optimum pond size for the OoL is intermediate, but biased toward smaller sizes. Sensitivities include relative access to nutrients, energy sources, and catalysts, as sourced from geological, atmospheric, hydrospheric, and astronomical contributors. Foreshores, especially with mudcracks, are identified as a favorable component for the success of the macrobiont. To bridge the gap between inanimate matter and a planetary-scale biosphere, five stages of evolution within the macrobiont are hypothesized: prebiotic chemistry → molecular replicator → protocell → macrobiont cell → colonizer cell. Comparison of ponds with other macrobionts, including hydrothermal and meteorite settings, allows a conclusion that more than one possible macrobiont locale could enable an OoL.
Highlights
The concept of the Macrobiont (MB) [1,2,3] is the planetary setting in which the first spark of life was struck from inanimate matter
“Astrobiology seeks to understand the web of interrelationships and feedbacks between time-variable planetary processes—both physical and chemical—and the proto-biological, chemical and organizational dynamics that led to the emergence and persistence of life
Our top-level requirement was for the macrobiont to provide the spatial and dynamic environments of the macrobiont that facilitate the origin of life and further development of cellular organisms for creation of a global biosphere
Summary
The concept of the Macrobiont (MB) [1,2,3] is the planetary setting in which the first spark of life was struck from inanimate matter. Much recent progress has been made in laboratory demonstrations of relatively straight-forward pathways for prebiotic chemical evolution, with good yields of fundamental biomolecules to transition from plausible, simpler geological and atmospheric constituents This progress has spanned various research groups, variously associated with, e.g., Bada, Benner, Carell, Deamer, Joyce, Sutherland, Szostak, Wächtershäuser [12,13,14,15,16,17,18,19], and many others. The recent report of the U.S National Academy of Sciences on “An Astrobiology Strategy for the Search for Life in the Universe” (2019) advocates the greater use of systems analysis in multiple areas of the field of Astrobiology [24] As they state, “Astrobiology seeks to understand the web of interrelationships and feedbacks between time-variable planetary processes—both physical and chemical—and the proto-biological, chemical and organizational dynamics that led to the emergence and persistence of life.
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