Abstract
20 years have passed since Woese and Fox proposed the third group of life Archaebacteria in 1977. The presence of the distinct group of Archaebacteria is widely accepted. Although, the principal division of all the living organism has been still a matter of argument. From the analysis of the characteristics of Archaebacteria and from the comparison of that with those of Eukaryotes and Eubacteria, we can speculate the early history of life. The characteristics of a general common ancestor (Commonote) from which all the living organisms have been derived, can be speculated based on the general phylogenetic tree. The general common ancestor has been proposed to be a thermophilic or ultra-thermophilic organism. Although, several other investigators have proposed alternative possibility. Very recently, Doolittle and his coworkers have presented the estimation of the time of major division of life in the history. It may be also possible to get information related to the process evolving the first cell of Eukaryotes from the analysis of Archaebacteria.
