A distrust of "the other" seems bred in our bones. It is natural to see ourselves as superior to those around us. A lion may be physically stronger than a man, but a man can use his superior intellect and social skills to devise tools and traps to outfox the lion. Or for that matter, outfox the fox.
Even on the human rungs of the ladder we are -- whoever we are -- the top rung, the chosen people, the shining city on the hill, superior in nationality, race or religion to all others. The great chain flatters our egos, gives us dominion, excuses our transgressions against everyone and everything on a lower rung. (I am mixing my metaphors, the ladder and the chain, but it is really the same metaphor.)
And then there is the matter of immortality, that primal longing that seems to be a corollary of consciousness and dreams. From the top of the earthly chain of being it is only a short leap into eternity and the company of angels.
So the persistence of the great chain of being as a metaphor for existence is no surprise.
But look at the message on the Homo sapiens leaf of yesterday's tree of life, the one green leaf among the "apes and humans": "Conservation status: Least concern. Population increasing." As humans threaten to overrun the planet and exhaust its resources, the great chain of being is a recipe for internecine strife and fatal exploitation. The metaphor suggests a desperate scramble up the ladder, with every created thing pulling and scratching at the creature above.
And then there is the alternate metaphor of the tree of life, a flowering of prodigious proportions, every leaf with its own dignity, no leaf closer to heaven. That leaf there, on the next twig, is my sister, whatever her nationhood, race or religion. We exalt together in the fullness of foliage, a fullness contrived by billions of years of evolution. We are all equidistant from the soil, with equal access to the sun.
This is not to minimize the problems humanity will face on an increasingly crowded planet, but those problems will only be exacerbated by clinging to an outworn metaphor that has no basis in empirical science.
OneZoom. One tree. One future.