The Dissipative Origin of Photosynthesis

Contemporary photosynthesis relies on the dissipation of visible solar photon energy through chlorophyll. Chlorophyll biosynthesis in modern organisms is a complex pathway involving more than 14 enzymatic steps. Near the origin of life, however, complex enzymes could not have existed, so primordial photosynthesis must have been a simpler, more direct process, but still based on photon dissipation. We have argued that life began around the early Archean through the molecular dissipative structuring of UV-C chromophores (now known as the fundamental molecules of life) under the thermodynamic imperative of dissipating Earth’s surface solar UV-C photons into heat. Here, employing the Granick hypothesis (linking biosynthetic order to evolutionary history), we chart a plausible non-enzymatic route for the UV-C dissipative structuring of chlorophyll. Starting from a likely common Archean precursor, glutamic acid, we show how dissipative structuring under UV-C light could have led to molecules en route to chlorophyll with ever-greater photon absorption cross sections and bandwidths, moving towards the absorption of visible wavelengths of higher photon intensities. Such a process demonstrates all the hallmarks of molecular dissipative structuring and may have been at the foundations of the complex biosynthetic pathway of visible photosynthesis appearing around 3.7 Ga.