On the role of the circadian system in the earliest
evolution of life: The diel hypothesis
Glen D. Brown
Every living organism has a circadian clock. The evolutionary study of circadian rhythms usually begins like other evolutionary studies with questions of adaptation, competition, and natural selection at the organismal level. I argue here that this is in error with reference to the earliest life because in my opinion it was not that living creatures evolved a circadian system so much as that the circadian system evolved us.
Like the great migration of plankton that takes place up and down the water column every day, so it seems likely to me that the primordial soup contained such an oscillation. My primary evidence for this is that so many molecules important for the development of life absorb photons readily, including a couple of my favorites, melatonin and serotonin.
Light as well as heat from the sun probably drove many of the autocatalysis reactions thought to be important for the early evolution of life. The very earliest competition for something we might think of as food but a chemist would call a substrate probably happened near the surface of the ocean during the day.
Timekeeping in nature, the ability to predict the sun’s appearance, likely predates the evolution of life as we think of it. Indeed I’m arguing that life is a manifestation of this timekeeping. I would guess that molecules in the late primordial soup and also the earliest biological organisms used replication as a means of timekeeping, probably to wake up on time.
At the very least, that I can make this proposal reminds us how deeply ingrained the circadian system is in our biology.
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Paranjpe, D.A.;Sharma,V.K., "Evolution of temporal order in living organisms." Journal of Circadian Rhythms, 2005: 3,p.Art. 7. doi: 10.1186/1740-3391-3-7
Hut, R.A., Beersma, D.G.M., "Evolution of time-keeping mechanisms: early emergence and adaptation to photoperiod. Phil. Trans. R. Soc. B, 2011: 366 2141-2154. doi:10.1098/rstb.2010.0409
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This is a very interesting idea. I believe it to be correct and it definately deserves some fleshing out. For example, photochemistry should enable us to establish the "light memory" of individual macromolecules, and compare this with the potential "light memory" of simple autocatalytic sets of such molecules. Is such photo-induced motion of non-cellular biomolecules observable in the ocean of today?
It is surely the case that one of the earliest abilities of living matter should be knowledge of the daily light cycle. Is this something that could happen before the stage of protocells, ie: in a bulk macromolecular aqueous medium. It is an intriguing concept. Solaris comes to mind.
I the author would be interested in this paper https://www.hindawi.com/journals/mbi/2013/987549/ which describes ideas on the early evolutionary quantum interactions of water, light and biomolecules. The referenced Preparata/del Giudice/Vitiello theory of quantum coherent water is probably correct and is widely ignored by the mainstream. This is due to unexamined prejudices that (1) correlations in bio-phase decay as they do in a gas (2) that bulk kinetics are the basis of living biochemistry, as well as a failure to appreciate that low energy states in quantum field theory can be coherent due to vacuum condensation. Ideas such as these and those of the author, surely point to a radically different perspective on biogenesis, contrasting greatly with the depleted ideas of the 'RNA-worlders', and even making Oparin-ists look staid.
One slight criticism is of the final sentence: "At the very least, that I can make this proposal reminds us how deeply ingrained the circadian system is in our biology.". Surely this argument could be made of any theory.
The reviewer declares no conflict of interest with the author.
This Scientific American post may be of interest for background reading:
"The first clock presumably appeared in a unicellular organism." Not any more!
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