Perhaps Darwin was feeling a prick of conscience for having torn away the mainstay of human smugness with his documentation of evolution-- after all, we would never again be able to view ourselves as created rulers of a world made expressly for us. But for whatever reason, as he wrote the last paragraphs of his epochal Origin of Species, Darwin felt compelled to summarize the few bastions of traditional hope that evolution might buttress. Life’s long continuity could at least inspire some confidence in an extended future; and the pathway from squishy invertebrate to transcendent human must mean that evolution implies progress. Darwin wrote: Hence we may look with some confidence to a secure future of great length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.
This comforting view still defines our general cultural understanding of evolution and its implications. Two rarely questioned beliefs, however, stand at the center of this vernacular interpretation:
First, that even though evolution has produced an enormously complex tree of branching lineages, life as a whole has moved from a world inhabited only by bacteria to a modern biota now dominated by the paragon of neural advance, Homo sapiens. In this general sense, evolution is inherently and predictably progressive.
Second, that evolution, as Darwin taught us, works by a process called natural selection. This mechanism requires that survivors in the struggle for existence be better adapted to local environments. Thus, each step in an evolutionary sequence must feature a precise and intricate fit of organism to environment. Natural selection tracks environmental change, as organisms remain intricately adapted while gaining in general complexity.
A kind of wonderful irony, both instructive and amusing, permeates this common understanding of evolution as a progressive sequence of creatures, each exquisitely well adapted to local environments. We believe that such an account of evolution makes our own appearance both sensible and predictable. Indeed, our preference for viewing evolution as progressive and strictly adaptational arose largely to validate our own presence as an unsurprising consequence of nature’s intrinsic order. And now, the irony: to produce a creature with our structural and neurological complexity, evolution must be creative in the vernacular sense of this word--that is, evolution must be able to develop novel structures with previously unrealized functions. How else could a process that began with bacteria ever add the number of novelties required to evolve a human being (or any complex multicellular creature)? Yet, if evolution truly worked simply by fashioning exquisitely adapted creatures in an ascending series, humans could never have originated at all.
