Woese (60) proposed the concept of "the universal ancestor
" to look at the rooting of the evolutionary tree.
The surprisingly large extent of gene swapping has researchers asking whether comparisons of genes indicate how closely related different microbes are and if such analyses can truly point the way back to a universal ancestor
. Furthermore, some biologists now argue that gene-transfer events lead to new bacterial species and can help explain why some microbes are harmless while others cause disease.
It appears that, at the time that the universal ancestor
of all life gave rise to the primary lineages, the aminoacyl-tRNA synthetases had not achieved as settled an evolutionary condition as is generally assumed.
The nature of the last universal ancestor
and the root of the tree of life, still open questions.