Final answer:
Glycolysis is the oldest metabolic pathway phylogenetically due to its simplicity and universal presence across animals and plants, following the principle of maximum parsimony.
Step-by-step explanation:
Because of its relative simplicity, it is not surprising that the glycolysis pathway was the earliest to arise phylogenetically. Glycolysis is a metabolic pathway that occurs in the cytosol, is found in all animals and plants, and does not require oxygen. This pathway's universality across organisms suggests its ancient origins, and this is supported by the principle of maximum parsimony, which favors the evolutionary pathway with the fewest major divergences that correlates with available evidence. In the exploration of the phylogenetic tree and evolutionary history, glycolysis is traced back to the Last Universal Common Ancestor (LUCA), making it one of the earliest metabolic pathways to have developed. The pathway's flexibility and prevalence underline its significance in the evolutionary puzzle.