The Tree of Life

Abstract

Like the oak tree Walt Whitman saw in Louisiana, the Tree of Life, the community of all living forms on this planet, both extant and extinct, stands alone. There may be trees of life on other planets in the universe and saplings of different trees may once have flourished on this planet; if they did, however, our own Tree of Life must have smothered them all. It soared above them billions of years ago, sank its roots deep into the fertile soil and furcated at an early stage into three beamy limbs, each of which ramified zillions of times over, giving forth to progressively thinner branches that produced a magnificent crown. The extant species are leaves on the terminal branches and like all leaves, they will one day be shed, only to be replaced by new ones on the most recently branched twigs. As on a live oak, every leaf on the Tree of Life is connected to all the other leaves through the pattern of growth — the twigs, the branches, the stem, and the roots. In contrast to a genuine live oak, however, the leaves on the Tree of Life are only connected by imaginary branches. The only real parts of the Tree of Life are the living individuals comprising the species, while the twigs, branches, and so forth are mental constructs conjured up to depict the presumed genealogical relationships among the individual species and groups of species. In other words, the Tree of Life is not a true arbre but a pedigree in the shape of a tree. In a pedigree, only the individuals correspond to reality, while the interconnecting lines designate relationships reconstructed from the historical record.

I saw in Louisiana a live-oak growing, All alone stood it and the moss hung down from the branches, Without any companion it grew there uttering joyous leaves of dark green, And its look, rude, unbending, lusty, made me think of myself. Walt Whitman: Leaves of Grass