Articles | Volume 12, issue 16
Research article
19 Aug 2015
Research article |  | 19 Aug 2015

Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum

K. Michaelian and A. Simeonov

Abstract. The driving force behind the origin and evolution of life has been the thermodynamic imperative of increasing the entropy production of the biosphere through increasing the global solar photon dissipation rate. In the upper atmosphere of today, oxygen and ozone derived from life processes are performing the short-wavelength UV-C and UV-B dissipation. On Earth's surface, water and organic pigments in water facilitate the near-UV and visible photon dissipation. The first organic pigments probably formed, absorbed, and dissipated at those photochemically active wavelengths in the UV-C and UV-B that could have reached Earth's surface during the Archean. Proliferation of these pigments can be understood as an autocatalytic photochemical process obeying non-equilibrium thermodynamic directives related to increasing solar photon dissipation rate. Under these directives, organic pigments would have evolved over time to increase the global photon dissipation rate by (1) increasing the ratio of their effective photon cross sections to their physical size, (2) decreasing their electronic excited state lifetimes, (3) quenching radiative de-excitation channels (e.g., fluorescence), (4) covering ever more completely the prevailing solar spectrum, and (5) proliferating and dispersing to cover an ever greater surface area of Earth. From knowledge of the evolution of the spectrum of G-type stars, and considering the most probable history of the transparency of Earth's atmosphere, we construct the most probable Earth surface solar spectrum as a function of time and compare this with the history of molecular absorption maxima obtained from the available data in the literature. This comparison supports the conjecture that many fundamental molecules of life are pigments which arose, proliferated, and co-evolved as a response to dissipating the solar spectrum, supports the thermodynamic dissipation theory for the origin of life, constrains models for Earth's early atmosphere, and sheds some new light on the origin of photosynthesis.

Short summary
We show that the fundamental molecules of life (those common to all three domains of life: Archaea, Bacteria, Eukaryota), including nucleotides, amino acids, enzyme cofactors, and porphyrin agglomerates, absorb light strongly from 230 to 280nm (in the UV-C) and have chemical affinity to RNA and DNA. This supports the "thermodynamic dissipation theory for the origin of life", which suggests that life arose and evolved as a response to dissipating the prevailing Archaean UV-C sunlight into heat.
Final-revised paper