What is Tree of life (biology)?
The '''tree of life''' is a [[metaphor]] which expresses the idea that all life is related by [[common descent]]. [[Charles Darwin]] was the first to use this [[metaphor]] in modern [[biology]]. It had been used many times before for other purposes. The ''evolutionary tree'' shows the relationships among various biological groups. It includes data from [[DNA]], [[RNA]] and [[protein]] analysis. Tree of life work is a product of traditional [[comparative anatomy]], and modern [[molecular evolution]] and [[molecular clock]] research. Below is a simplified version of present-day understanding. [[File:Simplified tree.png|center|400px|Simplified universal phylogenetic tree]] == Precursors == === Lamarck === Jean-Baptiste [[Lamarck]] (1744–1829) produced the first branching tree of animals in his ''Philosophie Zoologique'' (1809). It was an upside-down tree starting with worms and ending with mammals. However, Lamarck did not believe in common descent of all life. Instead, he believed that life consists of separate parallel lines advancing from simple to complex.<ref>Peter J. Bowler 2003. ''Evolution: the history of an idea''. 3rd ed, University of California Press. 90-91.</ref> === Hitchcock === [[File:Edward Hitchcock Paleontological Chart.jpg|right|thumb|Fold-out paleontological chart of Edward Hitchcock in 'Elementary Geology' (1840)]] The American geologist [[Edward Hitchcock]] (1763–1864) published in 1840 the first tree of life based on [[paleontology]] in his ''Elementary Geology''.<ref>J. David Archibald 2009. Edward Hitchcock’s Pre-Darwinian (1840) Tree of Life. ''Journal of the History of Biology'' '''42''':561–592</ref> On the vertical axis are [[Period (geology)|paleontological periods]]. Hitchcock made a separate tree for plants (left) and animals (right). The plant and animal trees are not connected at the bottom of the chart. Furthermore, each tree starts with multiple origins. However, they were not ''evolutionary'' trees, because Hitchcock believed that a [[deity]] was the agent of change. ==