We begin, perhaps, with a brain that is much too crowded with pure processing capacity, and therefore the death of the brain cells is part of a planned and necessary winnowing that precedes the move upward to higher levels of intelligence: the weak ones fizzle out, and the gaps they leave as they are reabsorbed stimulate the growth buds of dendrites, which now have more capacious playgrounds, and complex correlational structures come about as a result. (Or perhaps the dendrites' own heightened need for space to grow forces a mating struggle: they lock antlers with feebler outriggers in the search for the informationally rich connections, shortcutting through intermediate territories and causing them to wither and shut down like neighborhoods near a thruway.) With fewer total cells, but more connections between each cell, the quality of your knowledge undergoes a transformation: you begin to have a feel for situations, people fall into types, your past memories link together, and your life begins to seem, as it hadn't when you were younger, an inevitable thing composed of a million small failures and successes dependently intergrown, as opposed to a bright beadlike row of unaffiliated moments. Mathematicians need all those spare neurons, and their careers falter when the neurons do, but the rest of us should be thankful for their disappearance, for it makes room for experience. Depending on where on the range you began, you are shifted as your brain ages toward the richer, more mingled pole: mathematicians become philosophers, philosophers become historians, historians become biographers, biographers become college provosts, college provosts become political consultants, and political consultants run for office.

-from The Mezzanine

by Nicholson Baker.