Furthermore, their dna & ribosomes resemble those of bacteria. (for example, their chromosome is circle of dna. ) All this cellular evolution took place in the world"s oceans, and required about 3 billion years to accomplish. Geologists call the first billion years in the history of life the archean eon during this time it was all about bacterial evolution. The events of the 3rd eon (phanerozoic*) are listed in this diagram. Here"s another way to look at the time scale of evolution: The evolutionary relatedness of all life on earth is manifest at the molecular level. By sequencing the gene for the small subunit (ssu) of ribosomal rna in hundreds of life forms, Carl woese (pronounced woes") clarified our understanding of the family tree . Prior to woese"s work, all life on earth had been classified into 5 kingdoms: Woese found that there are in fact only three domains in the tree of life : bacteria, archaea, and eukarya.