Steven Pinker -- How the Mind Works - Hampshire High Italian ...

172 [ HOW THE MIND WORKS"Subtle details of engineering and design, which no man-made airfoilcan match, reveal how insect wings are remarkably adapted to the acrobaticsof flight." The evolution of insect wings is an argument for naturalselection, not against it. A change in selection pressure is not the same asno selection pressure.Complex design lies at the heart of all these arguments, and thatoffers a final excuse to dismiss Darwin. Isn't the whole idea a bitsquishy? Since no one knows the number of kinds of possible organisms,how can anyone say that an infinitesimal fraction of them have eyes?Perhaps the idea is circular: the things one calls "adaptively complex" arejust the things that one believes couldn't have evolved any other waythan by natural selection. As Noam Chomsky wrote,So the thesis is that natural selection is the only physical explanation ofdesign that fulfills a function. Taken literally, that cannot be true;. Takemy physical design, including the property that I have positive mass. Thatfulfills some function—namely, it keeps me from drifting into outerspace. Plainly, it has a physical explanation which has nothing to do withnatural selection. The same is true of less trivial properties, which youcan construct at will. So you can't mean what you say literally. I find ithard to impose an interpretation that doesn't turn it into the tautologythat where systems have been selected to satisfy some function, then theprocess is selection.Claims about functional design, because they cannot be stated inexact numbers, do leave an opening for a skeptic, but a little! thoughtabout the magnitudes involved closes it. Selection is not invoked toexplain mere usefulness; it's invoked to explain improbable usefulness.The mass that keeps Chomsky from floating into outer space is not animprobable condition, no matter how you measure the probabilities."Less trivial properties"—to pick an example at random, the vertebrateeye—are improbable conditions, no matter how you measure the probabilities.Take a dip net and scoop up objects from the solar system; goback to life on the planet a billion years ago and sample the organisms;take a collection of molecules and calculate all their physically possibleconfigurations; divide the human body into a grid of one-inch cubes.Calculate the proportion of samples that have positive mass. Now calculatethe proportion of samples that can form an optical image. There willbe a statistically significant difference in the proportions, and itlneeds tobe explained.I