Thermodynamic Origin of Life (0907.0042v3)

Abstract: Understanding the thermodynamic function of life may shed light on its origin. Life, as are all irreversible processes, is contingent on entropy production. Entropy production is a measure of the rate of the tendency of Nature to explore available microstates. The most important irreversible process generating entropy in the biosphere, and thus facilitating this exploration, is the absorption and transformation of sunlight into heat. Here we hypothesize that life began, and persists today, as a catalyst for the absorption and dissipation of sunlight at the surface of shallow seas. The resulting heat is then efficiently harvested by other irreversible processes such as the water cycle, hurricanes, and ocean and wind currents. RNA and DNA are the most efficient of all known molecules for absorbing the intense ultraviolet light that could have penetrated the dense early atmosphere, and are remarkably rapid in transforming this light into heat in the presence of liquid water. From this perspective, the origin and evolution of life, inseparable from water and the water cycle, can be understood as resulting from the natural thermodynamic imperative of increasing the entropy production of the Earth in its interaction with its solar environment. A mechanism is proposed for the reproduction of RNA and DNA without the need for enzymes, promoted instead through UV light dissipation and the ambient conditions of prebiotic Earth.

Thermodynamic Origin of Life: An Entropy-Centric Perspective

K. Michaelian's paper "Thermodynamic Origin of Life" offers an ambitious hypothesis about the birth and perpetuation of life, focusing on the thermodynamic principles underlying biological processes. The hypothesis is rooted in the concept of entropy production, an irreversible process driving the exploration of microstates by Nature. A pivotal assertion is that life commenced as a catalytic agent for absorbing and dissipating sunlight in the Archean seas, contributing substantially to global entropy production.

Key Thesis and Hypothesis

The paper posits that entropy production, particularly through solar photon absorption and dissipation, is integral to the emergence and persistence of life. This process facilitates energy transfer into Earth systems like the water cycle and atmospheric dynamics. The efficiency with which RNA and DNA absorb ultraviolet light—transforming it into heat—is seen as essential for catalyzing entropic processes. These are interpreted as naturally driven augmentations of entropy production through life's interactions with solar energy.

Mechanism for Life Initiation

Michaelian suggests a mechanism for RNA and DNA reproduction independent of enzyme action, driven instead by UV light dissipation and diurnal temperature fluctuations. This "UltraViolet and Temperature Assisted Reproduction" (UVTAR) relies on conditions prevalent in the Archean era, where high fluxes of UV photons contributed to an environment conducive to the formation and replication of nucleic acids without enzymatic catalysis.

Empirical Evidence and Theoretical Foundations

The hypothesis is buttressed by both historical and contemporary theoretical views on non-equilibrium structuring of matter, particularly through dissipative structures as conceptualized by Boltzmann, Prigogine, and Onsager. The paper brings to light how life, an inherently low-entropy structure, fits within the grand scale of entropy production, ultimately increasing the sampling efficiency of potential microstates in the biosphere.

Implications and Future Directions

The discussion in Michaelian's work encourages a reevaluation of life’s origin scenarios, advancing an entropy-oriented perspective that holds potential implications for understanding life's thermodynamic function. This approach could pave the way for novel interpretations of evolutionary processes, where natural selection is viewed through the lens of entropy production maximization.

In closing, the paper invites speculation on how life's future development might unfold within this entropy-centric framework. Insights could be particularly transformative in the fields of astrobiology and the search for extraterrestrial life. By understanding the conditions life needs to optimize entropy production, researchers can better evaluate the universality and variability of life across different planetary environments.

Michaelian's theory represents a coherent synthesis of thermodynamic concepts applied to biological systems, challenging the prevailing paradigms and offering a compelling lens through which to view the evolution and expansion of life in the universe.