Reply to Lars Olof Björn's comment on “Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum” by Michaelian and Simeonov (2015)

Abstract

Abstract. Lars Björn doubts our assertion that 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 global solar photon dissipation. Björn bases his critique on the fact that the albedo of non-biological material can sometimes be lower than that of biological material and concludes that such examples counter our assertion. Our reply to Björn, however, is that albedo (reflection) is only one factor involved in the entropy production through photon dissipation occurring in the interaction of light with material. The other contributions to entropy production, which were listed in our article, are (1) the shift towards the infrared of the emitted spectrum (including a wavelength-dependent emissivity), (2) the diffuse reflection and emission of light into a greater outgoing solid angle, and (3) the heat of photon dissipation inducing evapotranspiration in the pigmented leaf, thereby coupling to the abiotic dissipative processes of the water cycle, which, besides shifting the emitted spectrum even further towards the infrared, promotes pigment production over the entire Earth surface. His analysis, therefore, does not provide a legitimate reason for doubting our assertion that life and evolution are driven by photon dissipation. We remain emphatic in our assertion that the fundamental molecules of life were originally dissipatively structured UV-C pigments arising in response to the thermodynamic imperative of dissipating the prevailing Archean solar spectrum. In the following, we respond to Björn's comment using the same section headings.