Shadows of Forgotten Ancestors

Similarly, whales have small, internal, and wholly useless pelvises and leg bones, and snakes have four vestigial internal feet. (In the mambas of Southern Africa a single claw from each rudimentary limb breaks through the scaly skin to plain view.) If you swim or slither and never walk anymore, mutations for the withering away of feet do you no harm. They are not selected against. They might even be selected for (feet can be in the way when you’re pouring down a narrow hole). Or if you’re a bird that finds itself on an island devoid of predators, no penalty is levied for the steady atrophy, generation after generation, of wings (until European sailors arrive and club you all to death).

Mutations are occurring all the time for the loss of all sorts of functions. If there’s no disadvantage attached to these mutations, they can establish themselves in the population. Some will even be helpful—shedding formerly useful machinery, say, that is no longer worth the effort of maintaining. There must also be enormous numbers of mutations for biochemical incompetence and other major dysfunctions which result in beings that never survive their embryonic stages. They die before they’re born. They’re rejected by natural selection before the biologist can examine them. Relentless, draconian winnowing is occurring all around us. Selection is a school of hard knocks.

Evolution is just trial and error—but with the successes encouraged and proliferated, the failures ruthlessly extirpated, and prodigious vistas of time available for the process to work itself out. If you reproduce, mutate, and reproduce your mutations, you must evolve. You have no choice in the matter. You get to keep playing the game of life only if you keep winning; that is, if you keep leaving descendants (or close relatives). One break in the train of generations, and you and your particular, idiosyncratic DNA sequences are condemned without hope of reprieve.

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The English-language edition of this book is printed in letters that trace back to western Asia, and in a language primarily derived from Central Europe. But this is solely a matter of historical accident. The alphabet might not have been invented in the ancient Near East if there had not been a thriving mercantile culture there, if there had been no need for systematic records of commercial transactions. Spanish is spoken in Argentina, Portuguese in Angola, French in Quebec, English in Australia, Chinese in Singapore, a form of Urdu in Fiji, a form of Dutch in South Africa, and Russian in the Kuriles only because of a contingent sequence of historical events, some quite unlikely. Had they run a different course, other languages might be spoken in these places today. The Spanish, French, and Portuguese languages in turn depend on the fact that the Romans had imperial ambitions; English would be very different if Saxons and Normans had not been bent on overseas conquest; and so on. Language depends on history.

That a planet the size of the Earth is a sphere and not a cube, that a star the size of the Sun mainly emits visible light, that water is a solid and a liquid and a gas on any world at the surface temperature and pressure of the Earth—these facts are all readily understood from a few simple principles of physics. They are not contingent truths. They do not depend on a particular sequence of events that could just as well have gone some other way. Physical reality has a permanence and stability, an obsessive regularity to it, while historical reality tends to be fickle and fluid, less predictable, less rigidly determined by those laws of Nature we know. Something like accident or chance seems to play a major role in issuing marching orders to the flow of historical events.