Unraveling the Tree of Life

This article is a fully referenced research review to overview progress in unraveling the details of the evolutionary Tree of Life, from life's first occurrence in the hypothetical RNA-era, to humanity's own emergence and diversification, through migration and intermarriage, using research diagrams and brief discussion of the current state of the art. The Tree of Life, in biological terms, has come to be identified with the evolutionary tree of biological diversity. It is this tree which represents the climax fruitfulness of the biosphere and the genetic foundation of our existence, embracing not just higher Eucaryotes, plants, animals and fungi, but Protista, Eubacteria and Archaea, the realm, including the extreme heat and salt-loving organisms, which appears to lie almost at the root of life itself. To a certain extent the notion of a tree based on generational evolution has become complicated by a variety of compounding factors. Gene transfer is not just vertical carried down the generations. There is also evidence for promiscuous incidences of horizontal gene transfer, genetic symbiosis, hybridization and even the formation of chimeras. This review will cover all these aspects, from the first life on Earth to