02 Feb 2022
02 Feb 2022
Status: this preprint is currently under review for the journal BG.

Reply to Lars Olof Björn’s Comment on our article “Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum”

Karo Michaelian1 and Aleksandar Simeonov2 Karo Michaelian and Aleksandar Simeonov
  • 1Department of Nuclear Physics and Application of Radiation, Instituto de Física, Universidad Nacional Autónoma de México, Circuito Interior de la Investigación Científica, Cuidad Universitaria, Cuidad de México, C.P. 04510
  • 2Faculty of Natural Sciences and Mathematics, Ss. Cyril and Methodius University in Skopje, North Macedonia

Abstract. Lars Björn, in his critique of our article, doubts our assertion that at the origin of life the fundamental molecules of life (those in the three domains) were UVC pigments, dissipatively structured under a thermodynamic imperative to absorb and dissipate this UVC light into heat. Björn bases his critique on the suggestion that non-living material can be more photon absorbing than living material. He gives a number of examples in which he shows that the albedo of material devoid of life is lower than that of biotic material and concludes that these examples counter our assertion. However, Björn makes the erroneous assumption that albedo (reflection) is the only important factor related to photon dissipation (entropy production) occurring in the light-pigment interaction in living systems. He ignores the other contributions to entropy production due to the photon interaction which were listed in our article; 1) the shift towards the infrared of the emitted spectrum, 2) the diffuse emission and reflection of light into a greater outgoing solid angle, 3) the coupling of photon-induced evapotranspiration in the pigmented leaf to further photon dissipating processes such as the water cycle, which further allows dissipating biopigments to flourish over all of Earth’s surface. His assumption is therefore incorrect and his analysis does not provide legitimate reason for doubting our assertion that the fundamental molecules of life arose as pigments as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum.

In the following, we respond to each critique using the same section headings of Björn’s Comment.

Karo Michaelian and Aleksandar Simeonov

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-199', Anonymous Referee #1, 29 Apr 2022 reply

Karo Michaelian and Aleksandar Simeonov

Karo Michaelian and Aleksandar Simeonov


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Short summary
We reply to Lars Björn's critique of our article concerned with the importance of photon dissipation to the origin and evolution of the biosphere. Björn doubts our assertion that organic pigments, ecosystems, and the biosphere arose out of a thermodynamic imperative to increase the entropy production of Earth. He shows that the albedo of some non-living material is less than that of living material. We point out, however, that photon dissipation involves many other factors besides albedo.