The Atheist's Guide to Reality_ Enjoying Life Without Illusions - Alex Rosenberg [25]
Biologists have a label for the neat tricks that enable living things to take care of the four Fs of survival—feeding, fighting, flight, and . . . reproducing. The label for these traits is “adaptation.” Adaptations are everywhere, apparent in the match between living things and their environments. Think of the nocturnal bat and its echo-locating sonar or the leathery cactus with its waterproof skin optimized for survival in the desert. Adaptation is equally to be found in the coordination and cooperation of the parts that enable living things to exploit their environment. There is no point in birds soaring high above their prey without the visual acuity to see it.
Camouflage often provides the most compelling illustrations of adaptations to the environment. Photos like the one in Figure 1 are all over the Internet. What you see here is an insect, not a leaf, even though it’s green, flat, and broad, with the veins and segments of an oak leaf.
Many adaptations are so perfect, so intricate in their operation, so essential to survival, and so obvious that we take them for granted. The next time you are at a fish market, take a look at the whole flounders. Notice that each one has both eyes on the same side of the body. Why? The flounder is a bottom-dweller. It has no need of an eye looking down at the seafloor right beneath it and a great need to watch for predators and prey above it. Now you see why both eyes are on the same side of its body, the side it keeps facing up.
Job number one for biology is to explain both kinds of adaptations: organ to organism and organism to environment. From Aristotle in the third century bc to Kant in the eighteenth ad, the only way anyone could imagine explaining adaptations was by citing someone or something’s purposes. As noted in Chapter 2, such explanations are teleological.
FIGURE 1. Phyllium giganteum
Over the last 150 years, the eye has certainly been the most overworked example in debates about how to explain the adaptation of parts to the wholes they make up. We know whom to blame for dragging it into the debate. Darwin made it the biggest challenge to his own theory. In On the Origin of Species, he identified the eye as “an organ of extreme perfection.” There Darwin asserted, without qualification, that if natural selection could not explain the origin of its parts, their persistence, improvement, and how they gradually were put together into the complex organ they make up, then his theory of adaptation stood refuted.
It’s obvious that scientism needs to explain adaptation. The supposed impossibility of a purely physical explanation of adaptation is thrown up at us most often and most forcefully by theists. Since time immemorial, the economy of means to ends, vivid everywhere in nature, has been the strongest argument for the existence of their sort of God—the one who made man in his own image, along with making everything else. His design and his execution of that design are the only things that could ever explain adaptations. That was the idea Kant was pushing about blades of grass.
By the same token, nothing more powerfully threatens theism than an explanation of adaptation that meets Kant’s challenge. Nothing more powerfully vindicates scientism than an explanation of adaptation of just the kind Kant said couldn’t be given, one that invokes only physics.
Scientism needs more than an explanation of this or that particular adaptation—white fur in polar bears or the fact that bottom-dwelling fish have both eyes on the side of their bodies facing away from the bottom. We need an explanation of how, starting from zero adaptations, any adaptation at all ever comes about. The explanation we need can’t start with even a tiny amount of adaptation already present. Furthermore, the explanation can’t help itself to anything but physics. We can’t even leave room for “stupid