A short history of nearly everything - Bill Bryson [196]
Even Darwin's closest friends were troubled by the blitheness of some of his assertions. Adam Sedgwick, who had taught Darwin at Cambridge and taken him on a geological tour of Wales in 1831, said the book gave him “more pain than pleasure.” Louis Agassiz dismissed it as poor conjecture. Even Lyell concluded gloomily: “Darwin goes too far.”
T. H. Huxley disliked Darwin's insistence on huge amounts of geological time because he was a saltationist, which is to say a believer in the idea that evolutionary changes happen not gradually but suddenly. Saltationists (the word comes from the Latin for “leap”) couldn't accept that complicated organs could ever emerge in slow stages. What good, after all, is one-tenth of a wing or half an eye? Such organs, they thought, only made sense if they appeared in a finished state.
The belief was surprising in as radical a spirit as Huxley because it closely recalled a very conservative religious notion first put forward by the English theologian William Paley in 1802 and known as argument from design. Paley contended that if you found a pocket watch on the ground, even if you had never seen such a thing before, you would instantly perceive that it had been made by an intelligent entity. So it was, he believed, with nature: its complexity was proof of its design. The notion was a powerful one in the nineteenth century, and it gave Darwin trouble too. “The eye to this day gives me a cold shudder,” he acknowledged in a letter to a friend. In the Origin he conceded that it “seems, I freely confess, absurd in the highest possible degree” that natural selection could produce such an instrument in gradual steps.
Even so, and to the unending exasperation of his supporters, Darwin not only insisted that all change was gradual, but in nearly every edition of Origin he stepped up the amount of time he supposed necessary to allow evolution to progress, which pushed his ideas increasingly out of favor. “Eventually,” according to the scientist and historian Jeffrey Schwartz, “Darwin lost virtually all the support that still remained among the ranks of fellow natural historians and geologists.”
Ironically, considering that Darwin called his book On the Origin of Species, the one thing he couldn't explain was how species originated. Darwin's theory suggested a mechanism for how a species might become stronger or better or faster—in a word, fitter—but gave no indication of how it might throw up a new species. A Scottish engineer, Fleeming Jenkin, considered the problem and noted an important flaw in Darwin's argument. Darwin believed that any beneficial trait that arose in one generation would be passed on to subsequent generations, thus strengthening the species.
Jenkin pointed out that a favorable trait in one parent wouldn't become dominant in succeeding generations, but in fact would be diluted through blending. If you pour whiskey into a tumbler of water, you don't make the whiskey stronger, you make it weaker. And if you pour that dilute solution into another glass of water, it becomes weaker still. In the same way, any favorable trait introduced by one parent would be successively watered down by subsequent matings until it ceased to be apparent at all. Thus Darwin's theory was not a recipe for change, but for constancy. Lucky flukes might arise from time to time, but they would soon vanish under the general impulse to bring everything back to a stable mediocrity. If natural selection were to work, some alternative, unconsidered mechanism was required.
Unknown to Darwin and everyone else, eight hundred miles away in a tranquil corner of Middle Europe a retiring monk named Gregor Mendel was coming up with the solution.
Mendel was born in 1822 to a humble farming family in a backwater of