An analysis of modern genomes and reconstructed ancestral proteins finds a long-term rise in the oxidation state of their carbon. The peer-reviewed study links the pattern with environmental changes across Earth’s history. Its comparisons broadly overlap major oxygenation periods, while uncertain evolutionary dates and the effects of temperature complicate any direct reconstruction of ancient oxygen levels.
Protein carbon became more oxidized across several sets of evolutionary data examined in a peer-reviewed analysis published in Nature Communications. Researchers calculated the average carbon oxidation state from the amino acids making up each protein. The measure describes chemical composition: a larger value represents a different distribution of electrons in bonds, rather than a direct measurement of atmospheric oxygen.[1]
The comparison brings together modern genomes from methane-producing archaea and sulfur-cycling organisms, genes grouped by estimated age, and reconstructed ancestral proteins. Several groups show major steps broadly overlapping the Great Oxidation Event, about 2.4 billion years ago. A later rise appeared in gene-age groups from single-celled eukaryotes, organisms whose cells contain a nucleus, but not in the multicellular groups analysed.[1]
Thermodynamic models explored which protein compositions could be relatively stable under different environmental conditions. Oxygenation and long-term cooling overlap in Earth’s history, while acidity, habitat and biological function can also affect composition. Uncertain evolutionary dates limit precise alignment with geological evidence. The authors therefore treat the widespread chemical pattern as consistent with an environmental explanation while discouraging its use as a direct ancient-oxygen gauge.[1]
