According to the Encyclopædia Britannica, the tree of knowledge, connecting to heaven and the underworld, and the tree of life, connecting all forms of creation, are both forms of the world tree or cosmic tree.^[1] According to some scholars, the tree of life and the tree of the knowledge of good and evil, portrayed in various religions and philosophies, are the same tree.^[2] According to others, however, the tree of life concept is distinct from the tree of knowledge of good and bad, if only because eating from the latter leads to death and not life, and because it is mentioned in Genesis that there exists a distinct tree of life in the Garden of Eden ( although humans are barred from entry to the Garden by the time it is mentioned). The Abrahamic religions are Semitic in origin, and not Indo-European- which might serve to explain the lack of a cosmological tree idea in any of them, as well as in most Semitic cultures.

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.