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

200 HOW THE MIND WORKSMillions of years before our brains billowed out, some descendants ofthe common ancestor of chimpanzees and humans walked upright. In the1920s that discovery came as a shock to human chauvinists who imaginedthat our glorious brains led us up the ladder, perhaps as our ancestorsdecided at each rung what use to make of their newfound smarts. Butnatural selection could not have worked that way. Why bulk up your brainif you can't put it to use? The history of paleoanthropology is the discoveryof earlier and earlier birthdays for upright posture. The most recent discoveriesput it at four or even four and a half million years ago. Withhands freed, subsequent species ratchet upward, click by click, iri the featuresthat distinguish us: the dexterity of hands, the sophistication oftools, the dependence on hunting, the size of brains, the range of habitats.The teeth and jaw become smaller. The face that opposes it becomes lessmuzzle-like. The brow ridges that anchor the muscles that close the jawshrink and disappear. Our delicate faces differ from the brutes' becausetools and technology have taken over from teeth. We slaughter and skinanimals with blades, and soften plants and meats with fire. That eases themechanical demands on the jaw and skull, allowing us to shave bone fromour already heavy heads. The sexes come to differ less in size, suggestingthat males spent less of their resources beating each other up and perhapsmore on their children and the children's mothers.The stepwise growth of the brain, propelled by hands and feet andmanifested in tools, butchered bones, and increased range, is good evidence,if evidence were needed, that intelligence is a product of naturalselection for exploitation of the cognitive niche. The package was not aninexorable unfolding of hominid potential. Other species, omitted fromthe table, spun off in every epoch to occupy slightly different niches:nutcracking and root-gnawing australopithecines, perhaps one of the twohabiline subtypes, quite possibly the Asian branches of erectus andarchaic sapiens, and probably the Ice Age-adapted Neanderthals. Eachspecies might have been outcompeted when a neighboring, moresapiens-\\ke population had entered far enough into the cognitive nicheto duplicate the species' more specialized feats and do much elsebesides. The package was also not the gift of a macromutation or randomdrift—for how could such luck have held up in one lineage for millionsof years, over hundreds of thousands of generations, in species after bigger-brainedspecies? Moreover, the bigger brains were no mere ornamentsbut allowed their owners to make finer tools and infest more ofthe planet.