… a 3-billion-year-old testimony …
This is from Physiology and Biochemistry of Extremophiles edited by Charles Gerday and Nicolas Glansdorff (2007):
… At this point we would like to emphasize that even if the LUCA [last universal common ancestor] had been a thermophile, it does not follow that it grew in the very same range of temperatures as the modern extreme and hyperthermophilic organisms which may appear related to it in certain phylogenies.
[line break added] Modern thermophiles are the result of more than 3 billion years of evolution, during which further adaptation has certainly occurred, and as already mentioned above, molecular adaptations to thermophily look rather elaborated in the only living organisms we can investigate.
… The notion of a complex LUCA was considerably enriched by the recent suggestion that viruses may have been active participants in the dynamics of this primeval population: the “three viruses-three domains” (3V3D) hypothesis, which assumes that each cellular domain originated with an RNA-DNA transition engineered by a different DNA virus in a LUCA population with RNA genomes, may explain phylogenetic observations on DNA replication proteins that had remained rather puzzling until now.
… We consider that a colonization by space-traveling prokaryotes, even if it could have led to widespread colonization by their descendants, would not have produced anything fundamentally “more evolved,” because prokaryotes are evolutionary dead ends, a 3-billion-year-old testimony of what reductive evolution and intensive specialization can generate.
My most recent previous post from this book is here.
-Julie
Coloring 