Page from Darwin’s notebooks around July 1837 showing his first sketch of an evolutionary tree
Interpretation of handwriting: “I think case must be that one generation should have as many living as now. To do this and to have as many species in same genus (as is) requires extinction . Thus between A + B the immense gap of relation. C + B the finest gradation. B+D rather greater distinction. Thus genera would be formed. Bearing relation” (next page begins) “to ancient types with several extinct forms”
The tree of life is a metaphor describing the relationship of all life on Earth in an evolutionary context. Charles Darwin talks about envisioning evolution as a “tangled bank” in On the Origin of Species; however, the book’s sole illustration is of a branched diagram that is very tree-like.
“From the first growth of the tree, many a limb and branch has decayed and dropped off; and these fallen branches of various sizes may represent those whole orders, families, and genera which have now no living representatives, and which are known to us only in a fossil state. As we here and there see a thin, straggling branch springing from a fork low down in a tree, and which by some chance has been favoured and is still alive on its summit, so we occasionally see an animal like the Ornithorhynchus (Platypus) or Lepidosiren (South American lungfish), which in some small degree connects by its affinities two large branches of life, and which has apparently been saved from fatal competition by having inhabited a protected station. As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications.”
On the Origin of Species
17th-century depiction of the Tree of Life in Palace of Shaki Khans, Azerbaijan
The concept of a tree of life has been used in science, religion, philosophy, and mythology. A tree of life is a common motif in various world theologies, mythologies, and philosophies. It alludes to the interconnection of all life on our planet and serves as a metaphor for common descent in the evolutionary sense. The term tree of life may also be used as a synonym for sacred tree.
In George Herbert‘s poem The Sacrifice (part of The Temple, 1633), the Tree of Life is the rood on which Jesus Christ was crucified
In C. S. Lewis‘ Chronicles of Narnia, the Tree of Life plays a role, especially in the sixth published book (the first in the in-world chronology) The Magician’s Nephew