The Gene: An Intimate History - Siddhartha Mukherjee Page 0,28

hybrids. The youngest of the three scientists, von Tschermak had received news of two other parallel studies that fully corroborated his results, then waded back into the scientific literature to discover Mendel. He too had felt that ascending chill of déjà vu as he read the opening salvos of Mendel’s paper. “I too still believed that I had found something new,” he would later write, with more than a tinge of envy and despondency.

Being rediscovered once is proof of a scientist’s prescience. Being rediscovered thrice is an insult. That three papers in the short span of three months in 1900 independently converged on Mendel’s work was a demonstration of the sustained myopia of biologists, who had ignored his work for nearly forty years. Even de Vries, who had so conspicuously forgotten to mention Mendel in his first study, was forced to acknowledge Mendel’s contribution. In the spring of 1900, soon after de Vries had published his paper, Carl Correns suggested that de Vries had appropriated Mendel’s work deliberately—committing something akin to scientific plagiarism (“by a strange coincidence,” Correns wrote mincingly, de Vries had even incorporated “Mendel’s vocabulary” in his paper). Eventually, de Vries caved in. In a subsequent version of his analysis of plant hybrids, he mentioned Mendel glowingly and acknowledged that he had merely “extended” Mendel’s earlier work.

But de Vries also took his experiments further than Mendel. He may have been preempted in the discovery of heritable units—but as de Vries delved more deeply into heredity and evolution, he was struck by a thought that must also have perplexed Mendel: How did variants arise in the first place? What force made tall versus short peas, or purple flowers and white ones?

The answer, again, was in the garden. Wandering through the countryside in one of his collecting expeditions, de Vries stumbled on an enormous, invasive patch of primroses growing in the wild—a species named (ironically, as he would soon discover) after Lamarck: Oenothera lamarckiana. De Vries harvested and planted fifty thousand seeds from the patch. Over the next years, as the vigorous Oenothera multiplied, de Vries found that eight hundred new variants had spontaneously arisen—plants with gigantic leaves, with hairy stems, or with odd-shaped flowers. Nature had spontaneously thrown up rare freaks—precisely the mechanism that Darwin had proposed as evolution’s first step. Darwin had called these variants “sports,” implying a streak of capricious whimsy in the natural world. De Vries chose a more serious-sounding word. He called them mutants—from the Latin word for “change.”I

De Vries quickly realized the importance of his observation: these mutants had to be the missing pieces in Darwin’s puzzle. Indeed, if you coupled the genesis of spontaneous mutants—the giant-leaved Oenothera, say—with natural selection, then Darwin’s relentless engine was automatically set in motion. Mutations created variants in nature: long-necked antelopes, short-beaked finches, and giant-leaved plants arose spontaneously in the vast tribes of normal specimens (contrary to Lamarck, these mutants were not generated purposefully, but by random chance). These variant qualities were hereditary—carried as discrete instructions in sperm and eggs. As animals struggled to survive, the best-adapted variants—the fittest mutations—were serially selected. Their children inherited these mutations and thus generated new species, thereby driving evolution. Natural selection was not operating on organisms but on their units of heredity. A chicken, de Vries realized, was merely an egg’s way of making a better egg.

It had taken two excruciatingly slow decades for Hugo de Vries to become a convert to Mendel’s ideas of heredity. For William Bateson, the English biologist, the conversion took about an hour—the time spent on a speeding train between Cambridge and London in May 1900.II That evening, Bateson was traveling to the city to deliver a lecture on heredity at the Royal Horticultural Society. As the train trundled through the darkening fens, Bateson read a copy of de Vries’s paper—and was instantly transmuted by Mendel’s idea of discrete units of heredity. This was to be Bateson’s fateful journey: by the time he reached the society’s office on Vincent Square, his mind was spinning. “We are in the presence of a new principle of the highest importance,” he told the lecture hall. “To what further conclusions it may lead us cannot yet be foretold.” In August that year, Bateson wrote to his friend Francis Galton: “I am writing to ask you to look up the paper of Mendl [sic] [which] seems to me one of the most remarkable investigations yet made on heredity and it is extraordinary that it should have got forgotten.”

Bateson made it his personal