A Milestone For the Understanding of Life at Earth!

On Earth, there are unicellular beings like bacteria, and multicellular ones like humans. On the other hand cells, these basic parts for life, part into two varieties: prokaryotes which are the simplest of cells, and eukaryotes which are most elaborated. Generally, at the exception of some, most unicellular organisms (like bacteria e.g.) are composed of prokaryotes only, as more advanced forms, multicellular, forms of life (like humans, animals, fungi, or plants), are made of eukaryotes. Prokaryotes are lacking a nuclear membrane (the one which is surrounding the nucleus) and other features founds in eukaryotes like the organelles. Functions performed by the latters are performed in prokaryotes by the cell plasma membrane. Bacteria are the best known of prokaryotes. Archaeae are a second group of such cells and are of the extremophile sort. They may thrive in harsh environments. Eukaryotes on the other hand are more advanced cells with compatments performing specific metabolic tasks and having a nucleus where the cell's DNA is protected. Eukaryotic cells brought the life a step further as, although performing the same tasks than prokaryotes -and both working on the basis of DNA- they had a higher level of complexity hence permitting the development of the multicellular forms of life

->The view of how life had evolved was until now that of a "tree of life". Primitive forms of life had worked on the basis of the primitive prokaryotes and progressively let the room for more advanced, multi-cellular, eukaryotic forms of life working with more advanced forms of cells, with advanced functions. Life at Earth is thought to have appeared about 3.5 billion years ago under the form of bacteria as multi-cellular forms of life appeared and improved between 1.5 and 0.5 billion years ago. This tree of life view has now to be revised as the UCLA study is proving that the eukaryotes, these most advanced cells, hence the most advanced forms of life, were born from the encounter between two prokaryotic forms of life. The extremophiles Archaeae did not follow bacteria. They thrived together on the primitive Earth and their two genomes merged to give birth to the first, more advanced, eukaryotic cell, 2 billion years ago! Such a finding was made possible through a genomics study of some microorganisms as a computer simulation led to the best genome match for the ancestor of the modern eukariotic cells. Our cell operating mechanisms would come from the bacterial side of the family as our information-carrying genes would come from the Archaea side. Our far ancestors are one bacterium on one hand, and an extremophile Archaea on the other hand! This collaboration about genomics between microbiologists, evolutionists, and computer modelization, will certainly help shed new light on the relations between living forms and will take the science of evolution a step further as until now classifying living creatures had been essentially based on observable traits. DNA studies are now allowing a more accurate view of how living beings are related. Some scientists already thought that Archaeae were another class of cells -neither prokaryotes nor eukaryotes- and that they had participated to the origins of life