The nature of the last universal common ancestor

Cytologically, prokaryotes appear simpler and thus evolutionarily 'older' t han eukaryotes. In terms of RNA processing, however, prokaryotes are sophis ticated and eukaryotes, which retain many features of an RNA-world, appear primitive. The last universal common ancestor may have been mesophilic and could have had many features of the eukaryote genome, but its cytology is u nknown.