'Survival of the fittest' phenomenon is only part of the evolution equation

Darwin’s theory of evolution should be expanded to include consideration of a DNA stability “energy code” – so-called “molecular Darwinism” – to further account for the long-term survival of species’ characteristics on Earth, according to Rutgers scientists. The iconic genetic code can be viewed as an “energy code” that evolved by following the laws of thermodynamics (flow of energy), causing its evolution to culminate in a nearly singular code for all living species, according to the Rutgers co-authored study in the journal Quarterly Reviews of Biophysics.1

Scientists investigated this so-called “universal enigma,” probing the origins of the astounding observation that the genetic code evolved into a nearly uniform blueprint that arose from trillions of possibilities.

  • 1. “These revelations matter because they provide entirely new ways of analyzing the human genome and the genome of any living species, the blueprints of life,” said senior author Kenneth J. Breslauer, Linus C. Pauling Distinguished University Professor in the Department of Chemistry and Chemical Biology in the School of Arts and Sciences at Rutgers University–New Brunswick. He is also affiliated with the Rutgers Cancer Institute of New Jersey. “The origins of the evolution of the DNA genetic code and the evolution of all living species are embedded in the different energy profiles of their molecular DNA blueprints. Under the influence of the laws of thermodynamics, this energy code evolved, out of an astronomical number of alternative possibilities, into a nearly singular code across all living species.”

Horst H. Klump, Jens Völker, Kenneth J. Breslauer. Energy mapping of the genetic code and genomic domains: implications for code evolution and molecular Darwinism. Quarterly Reviews of Biophysics, 2020; 53 DOI: 10.1017/S0033583520000098

When the iconic DNA genetic code is expressed in terms of energy differentials, one observes that information embedded in chemical sequences, including some biological outcomes, correlate with distinctive free energy profiles. Specifically, we find correlations between codon usage and codon free energy, suggestive of a thermodynamic selection for codon usage. We also find correlations between what are considered ancient amino acids and high codon free energy values. Such correlations may be reflective of the sequence-based genetic code fundamentally mapping as an energy code. In such a perspective, one can envision the genetic code as composed of interlocking thermodynamic cycles that allow codons to ‘evolve’ from each other through a series of sequential transitions and transversions, which are influenced by an energy landscape modulated by both thermodynamic and kinetic factors. As such, early evolution of the genetic code may have been driven, in part, by differential energetics, as opposed exclusively by the functionality of any gene product. In such a scenario, evolutionary pressures can, in part, derive from the optimization of biophysical properties (e.g. relative stabilities and relative rates), in addition to the classic perspective of being driven by a phenotypical adaptive advantage (natural selection). Such differential energy mapping of the genetic code, as well as larger genomic domains, may reflect an energetically resolved and evolved genomic landscape, consistent with a type of differential, energy-driven ‘molecular Darwinism’. It should not be surprising that evolution of the code was influenced by differential energetics, as thermodynamics is the most general and universal branch of science that operates over all time and length scales.

Keywords: Codon energy distribution spectrumcodon free energiescodon usage frequencyenergy codeinterlocking thermodynamic cyclesmolecular evolution