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

168 J HOW THE MIND WORKSmuch honour to the creative power of committees. For a camel is nochimera, no odd collection of bits, but an elegant design of the tightestunity. So far as we can judge, every part is contrived to suit the difficultrole of the whole, a large herbivorous animal to live in harsh climateswith much soft going, sparse vegetation and very sparse water. The specificationfor a camel, if it were ever written down, would be a tough one interms of range, fuel economy and adaptation to difficult terrains andextreme temperatures, and we must not be surprised that the design thatmeets it appears extreme. Nevertheless, every feature of the camel is of apiece: the large feet to diffuse load, the knobbly knees that derive fromsome of the design principles of Chapter 7 [bearings and pivots], thehump for storing food and the characteristic profile of the lips have acongruity that derives from function and invests the whole creation witha feeling of style and a certain bizarre elegance, borne out by the beautifulrhythms of its action at a gallop.Obviously, evolution is constrained by the legacies of ancestors andthe kinds of machinery that can be grown out of protein. Birds could nothave evolved propellers, even if that had been advantageous. But manyclaims of biological constraints are howlers. One cognitive scientist hasopined that "many properties of organisms, like symmetry, for example,do not really have anything to do with specific selection but just with theways in which things can exist in the physical world." In fact, most thingsthat exist in the physical world are not symmetrical, for obvious reasonsof probability: among all the possible arrangements of a volume of matter,only a tiny fraction are symmetrical. Even in the living world, themolecules of life are asymmetrical, as are livers, hearts, stomachs, flounders,snails, lobsters, oak trees, and so on. Symmetry has everything to dowith selection. Organisms that move in straight lines have bilaterallysymmetrical external forms because otherwise they would go in circles.Symmetry is so improbable and difficult to achieve that any disease ordefect can disrupt it, and many animals size up the health of prospectivemates by checking for minute asymmetries.Gould has emphasized that natural selection has only limitedfreedom to alter basic body plans. Much of the plumbing, wiring, andarchitecture of the vertebrates, for example, has been unchanged for hundredsof millions of years. Presumably they come from embryologicalrecipes that cannot easily be tinkered with. But the vertebrate body planaccommodates eels, cows, hummingbirds, aardvarks, ostriches, toads,gerbils, seahorses, giraffes, and blue whales. The similarities are impor-