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

160 | HOW THE MIND WORKSrummy hand; each beneficial mutation was added to a set of prior onesthat had been selected over the eons.A fourth alternative is random genetic drift. Beneficial traits are beneficialonly on average. Actual creatures suffer the slings and arrows ofoutrageous fortune. When the number of individuals in a generation issmall enough, an advantageous trait can vanish if its bearers are unlucky,and a disadvantageous or neutral one can take over if its bearers arelucky. Genetic drift can, in principle, explain why a population has a simpletrait, like being dark or light, or an inconsequential trait,; like thesequence of DNA bases in a part of the chromosome that doesn't do anything.But because of its very randomness, random drift cannot explainthe appearance of an improbable, useful trait like an ability to see or fly.The required organs need hundreds or thousands of parts to work, andthe odds are astronomically stacked against the required genes accumulatingby sheer chance.Dawkins' argument about extraterrestrial life is a timeless claim aboutthe logic of evolutionary theories, about the power of an explanans tocause the explanandum. And indeed his argument works against twosubsequent challenges. One is a variant of Lamarckism called directed oradaptive mutation. Wouldn't it be nice if an organism could react to anenvironmental challenge with a slew of new mutations, and not wasteful,random ones, but mutations for traits that would allow it to cope? Ofcourse it would be nice, and that's the problem—chemistry has no senseof niceness. The DNA inside the testes and ovaries cannot peer outsideand considerately mutate to make fur when it's cold and fins when it'swet and claws when there are trees around, or to put a lens in front ofthe retina as opposed to between the toes or inside the pancreas. That iswhy a cornerstone of evolutionary theory—indeed, a cornerstone of thescientific worldview—is that mutations are indifferent overall to the benefitsthey confer on the organism. They cannot be adaptive in general,though of course a tiny few can be adaptive by chance. The periodicannouncements of discoveries of "adaptive mutations" inevitably turnout to be laboratory curiosities or artifacts. No mechanism short of aguardian angel can guide mutations to respond to organisms' needs ingeneral, there being billions of kinds of organisms, each with thousandsof needs.The other challenge comes from the fans of a new field called thetheory of complexity. The theory looks for mathematical principles oforder underlying many complex systems: galaxies, crystals, weather sys-