Which group of organisms is the oldest on our planet?

Today the archaea are considered the most ancient group of living organisms on our planet. Archaea were identified in a separate domain by Karl Woese (previously they were classified as bacteria) and are considered the main candidates for the role of the last universal ancestor (LUCA). Their study sheds light on the evolution of the emergence of eukaryotes and sexual reproduction. Their habitat is quite wide, including the most extreme conditions with high temperatures, lack of oxygen and high pressures.