River Out of Eden - Do Good By Stealth

Do Good By Stealth

Further information: The Blind Watchmaker, evolution of the eye

The main themes of the third chapter are borrowed from Dawkins' own book, The Blind Watchmaker. This chapter shows how the gradual, continuous and cumulative enhancement to organisms via natural selection is the only mechanism which can explain the complexity we observe all around us in nature. Dawkins adamantly refutes the "I cannot believe so and so could have evolved by natural selection" argument of Creationists, calling it the Argument from Personal Incredulity.

Creationists often claim that some features of organisms (e.g. resemblance of Ophrys (orchid) to female wasp, figure-eight dances of honeybees, mimicry of stick insects, etc.) are too complicated to be a result of evolution. Some say, "half of an X will not work at all." Others say, "in order for X to work, it had to be perfect the first time." Dawkins concludes that these are no more than bold assertions based on ignorance:

... Do you actually know the first thing about orchids, or wasps, or the eyes with which wasps look at females and orchids? What emboldens you to assert that wasps are so hard to fool that the orchid's resemblance would have to be perfect in all dimensions in order to work?

Dawkins goes on to illustrate his point by demonstrating how scientists have been able to fool creatures big and small using seemingly dumb triggers. For instance, stickleback fish treat a pear-shaped as a sex bomb (a supernormal stimulus). Gulls' hard-wired instincts make them reach over and roll back not just their own stray eggs, but also wooden cylinders and cocoa tins. Honeybees push out their live and protesting companion from their hive, when the companion is painted with a drop of oleic acid. Furthermore, a turkey will kill anything which moves in its nest unless it cries like a baby turkey. If the turkey is deaf, it will mercilessly kill its own babies.

As part of this, Dawkins emphasizes the gradual nature of evolution. For example, some creatures such as the stick insects possess the most amazing degree of camouflage, but in fact any sort of camouflage is better than none. There is a gradient from perfect camouflage to zero camouflage. A 100 percent camouflage is better than 99 percent. A 50 percent camouflage is better than 49 percent. A 1 percent camouflage is better than no camouflage. A creature with 1 percent better camouflage than its contemporaries will leave more descendants over time (an evolutionary success), and its good genes will come to dominate the gene pool.

Not only can we classify the degree of insect camouflage using a gradient, we can also study all aspects of the surrounding environment as gradients. For instance, a 1 percent camouflage may not be distinguishable from no camouflage under bright daylight. But as light fades and night sets in, there is a critical moment when the 1 percent camouflage helps an insect escape detection by its predator, while its companion with no camouflage is eaten. The same principle can be applied to the distance between prey and predator, to the angle of view, to the skill or the age of a creature, etc.

In addition to demonstrating how gradual changes can bring about features as complex as the human eye, Dawkins states that computer simulation work by Swedish scientists Dan Nilsson and Susanne Pelger (although it is not a computer simulation but simple mathematical model) shows that the eye could have evolved from scratch a thousand times in succession in any animal lineage. In Dawkins' own words, "the time needed for the evolution of the eye... turned out to be too short for geologists to measure! It is a geological blink." And, "it is no wonder the eye has evolved at least forty times independently around the animal kingdom."