Glycolysis is an ancient process that developed in the first prokaryotes as their primary means of (energy) production. Evidence of this is shown by its occurrence in the cytoplasm of eukaryotic cells rather than in the mitochondria, signifying that glycolysis was not introduced to eukaryotes with the incorporation of mitochondria but rather developed long before the first eukaryote and simply remained in the eukaryotes after their evolutionary development. This process was important in the first living organisms due to the almost complete absence of oxygen in the ancient atmosphere.
The glycolytic pathway, once thought to be ubiquitous among all organisms, has been found to have variations in different organisms, particularly those belonging to the domain Archaea. This has led to new speculations about the prevalence of glycolysis in both archaea and eukaryotes as well as its importance in the evolution of all living organisms.
The glycolytic pathway, in almost every living organism, involves complex oxidation-reduction reactions that occur as a result of the presence of ten different enzymes. Due to the overwhelming prevalence of this variation of the glycolytic pathway, it was once thought that these ten enzymes were ubiquitous in all organisms. However, with the analysis of the glycolytic pathways in certain thermophilic archaea, it has been found that only two of the common ten enzymes, known as enolase and pyruvate kinase, are present for glycolysis in these organisms. Currently, these are the only two enzymes believed to be ubiquitous in all glycolytic pathways. This suggests that the pathway may have had its origins in certain archaea which conducted glycolysis with the use of only enolase and pyruvate kinase. .
As time progressed, other enzymes may have been included in the pathway and, as the Earth's climate and environment changed, they became present in nearly all organisms through the process of natural selection while the thermophilic archaea were left behind by the process, thereby providing an insight into the distant evolutionary past of glycolysis.
