Cenancestor, the Last Universal Common Ancestor

摘要

Darwin suggested that all life on Earth could be phylogenetically related. Modern biology has confirmed Darwin’s extraordinary insight; the existence of a universal genetic code is just one of many evidences of our common ancestry. Based on the three domain phylogeny proposed by Woese and Fox in the early 1970s that all living beings can be classified on one of three main cellular lineages (Archaea, Bacteria, and Eukarya), it is possible to reconstruct some of the characteristics of the Last Universal Common Ancestor or cenancestor. Comparative genomics of organisms from the three domains has shown that the cenancestor was not a direct descendant of the prebiotic soup nor a primitive cellular entity where the genotype and the phenotype had an imprecise relationship (i.e., a progenote), rather it was an organism similar in complexity to extant cells. Due to the process of horizontal gene transfer and secondary gene losses, several questions regarding the nature of the cenancestor remain unsolved. However, attempts to infer its nature have led to the identification of a set of universally conserved genes. The research on the nature of the last universal common ancestor promises to shed light on fundamental aspects of living beings.