THE EVOLUTIVE PROCESS
Selective retention accumulates success, a little more, on average, in each feature in each cycle. It accelerates even minute advantages, so that in the next cycle the most advantageous features in the previous cycle will become the basis for new recombinations. If the selection pressures remain relatively stable, success compounds, and although the process has no forethought it can rapidly arrive at highly effective design. Eyes, a decided advantage in negotiating the world, have evolved independently perhaps over sixty times. Their complexity and efficiency often seem a trump to those who think the cards are stacked against evolution: “What use is half an eye?” In his brilliant rejoinder, Dawkins not only shows how even the feeblest capacity to register light could have been of benefit, but also describes a computer simulation demonstrating that a fish-eye lens could evolve from a simple structure of three cell layers, transparent over photosensitive over opaque, in as little as 364,000 generations, less than half a million years for organisms that reproduce at a year old.
© Brian Boyd – On The Origin of Stories (excerto) – Belknap Harvard