The Atheist's Guide to Reality_ Enjoying Life Without Illusions - Alex Rosenberg [28]
The consequence is that there is always at least some variation in hereditary traits. This was the great insight Darwin brought home from his five-year voyage around South America on HMS Beagle. Variation in traits is the rule throughout biology. In chemistry, by contrast, variations within the periodic table of the elements (the isotopes) are rare exceptions. Before Darwin, biologists thought that species were more like the chemical elements, in which individual variations were exceptions, special cases, deformations, defective cases. The Beagle voyage convinced Darwin that in the biological domain, variation is the rule. He was right.
The result of repeated filtering by the environment of the many old and the few new variants in every generation is the emergence and enhancement of adaptive traits, traits that work well enough in their environments for the things that bear them to survive long enough to reproduce again. This was the idea Darwin found in Thomas Malthus’s Essay on Population. He called this filtering by the environment “natural selection.” He should have called it “environmental filtration,” for the process that Darwin envisioned gives nature only a passive role. The local environment allows some organisms to live a little longer and have a few more offspring, while it prevents others from doing either. There is, in Darwin’s view, no active “picking and choosing” or active “selecting” by nature of those variations that meet some preestablished criteria for survival and reproduction.
Most important, in this process there is absolutely no foresight about what variants will be useful to their bearers in the future. The absence of foresight in nature is better captured by the label “blind variation” than the more usual “random variation.” As we’ll see, the lack of foresight that Darwin attributed to nature has always been his theory’s greatest strength. At the same time, it has been the theory’s biggest sticking point for skeptics. The theory suggests that nature is rather like a driver navigating through a frantically busy and complex maze of streets in rush-hour traffic, relying only on a narrow rearview mirror. It seems like it would be a miracle if the driver survived, let alone ever arrived, safe and sound, at home.
The essence of natural selection is nature’s passivity and lack of foresight. Darwin realized that passive processes with no foresight are what build all the incredible adaptations that seem to show such exquisite purpose. He saw clearly that the biological realm is as free of purpose as the physical realm. There is really no alternative but to treat purpose as just an illusion. It turns out to be an anthropomorphic overlay, fostered in large part by our talent for seeing conspiracies—malign and benign—everywhere. The appearance of purpose is a trick. Natural selection is physics faking design.
Physics is so good at faking design that even after Darwin pulled the curtain down and revealed the trickery, people still have had a hard time not reverting to a purposive view of nature. Every spoken language is rife with the images of nature as a cunning agent, knowingly taking a hand in shaping the outcome of biological processes. It is really no surprise that even the most dyed-in-the-wool Darwinian still invokes images of Mother Nature and the design problems she imposes on organisms, groups, and species. This is harmless, perhaps even helpful—a convenient metaphor. We made use of it ourselves in previous chapters. In the chapters to come, we will find even more convenient these and similar shorthand descriptions for processes that combine randomness and filtration to produce the simulacrum of design. Such expressions, which credit purely physical processes with volition, intention, and foresight, not to mention intelligence and wisdom, can always be cashed in for descriptions