A Brief History of Creation (21 page)

Eventually, Cuvier and Geoffroy found themselves running separate wings in the Paris Museum of Natural History, where they used their authority to advance their clashing interpretations of the fossils and bones in their charge. In 1830, the French Academy of Sciences decided to stage a public debate between the two men, to be held at the museum. It ended up lasting nearly two months. Honoré de Balzac, Gustave Flaubert, and George Sand all weighed in with their own presentations at one point or another. By the time it was all over, it seemed as if all of France was following the proceedings. So, too, were many abroad. From Switzerland, the German writer Johann Wolfgang von Goethe followed every twist and turn with interest. In German academic circles, the concept of a wholly
naturalistic origin of life was more firmly held, and spontaneous generation was seldom in dispute. To a friend, Goethe likened the debate to the eruption of a volcano. When the conservative French Academy of Sciences finally declared Cuvier the winner, Goethe was disgusted. He attributed the outcome to nothing more than an assertion of the old guard's power. As France grew ever more conservative, support there for spontaneous generation waned for the next two decades.

O
NLY TEN YEARS OLD
at the time of Cuvier and Geoffroy's famous clash, Pasteur grew up in the politically polarized world of French natural philosophy. It would color his view of science and his own place in it. Politically conservative, Pasteur pitted himself against materialism when it came to the life sciences. Like Cuvier, he stood for tradition and Catholicism.

Pasteur's rise to prominence in the world of French science had been quick, but it was not easy or predictable. He was born in 1822, the son of a poor leather tanner from the small city of Dole in the south. In college, he struggled with chemistry and spent little time working in the life sciences that would dominate his later career. His first university appointment was as a professor of physics at the University of Strasbourg.

Pasteur had an early interest in the nature of crystals, a fascination he shared with Andrew Crosse. At Strasbourg, the study of crystals led Pasteur to confront a puzzle about the nature of life for the first time. Working with a crude polarimeter, a device that measures the ways chemicals interact with light beams, Pasteur set about studying the effects of light when passed through solutions of tartaric acid, a substance commonly found in fruits like grapes and tamarind. Tartaric acid was also made synthetically and sold as a baking agent called racemic acid. Pasteur noticed that tartaric acid and racemic acid, while compositionally identical, had very different effects when he passed polarized light through solutions of them. Tartaric acid neatly rotated the light clockwise, while racemic acid seemed to have no effect on the light at all.

Pasteur was puzzled by this difference, but very close inspection with a magnifying lens revealed that a solution of racemic acid that he'd left to
crystallize in a beaker on a windowsill had produced two types of crystals, seemingly identical in every respect but actually mirror images of each other. Pasteur painstakingly set about separating the two types of crystals into two small piles. When he dissolved the two piles separately, he found that each solution rotated polarized light beams in opposite directions, and that one of the crystal types was identical to natural tartaric acid. Pasteur realized that the synthetic racemic acid was a one-to-one mixture of the natural form of tartaric acid and its mirror-image isomer.

Pasteur had stumbled upon the phenomenon of chirality. Many molecules are what a chemist would call “chiral,” meaning that they come in left- and right-handed forms that are mirror images of each other, like left- and right-handed gloves. These two forms have the same number of atoms, and the atoms are connected in the same way, but the two forms cannot be superimposed on top of each other, just as a right hand cannot be superimposed on a left hand. Most important biological molecules—such as the components of proteins or nucleic acids—are in fact
homochiral
, meaning that the orientation of every molecule is exactly the same, either right-handed or left-handed. The reason for the phenomenon of homochirality in biology would be a topic of debate among biochemists for another century. For Pasteur, the discovery reinforced his notions of a vitalist line separating the worlds of living and nonliving matter.

I
N 1854, PASTEUR WAS NAMED
professor of chemistry and dean of the Faculty of Sciences at the University of Lille. Soon, he found himself turning to a subject that had even more obvious biological implications: the problem of alcohol. More precisely, how did the process of fermentation work to make alcohol? It was a mystery that had fascinated countless observers since ancient times.

Lille was in the heart of French sugar beet country. Back in the Napoleonic era, sugar had been hard to come by in France, owing to the decade-long blockade by Great Britain, so Napoleon, ever the micromanager, had encouraged the growth of a domestic sugar beet industry. French distillers
had tried their hand at concocting a kind of rum from beet juice, but making it palatable was not easy. Its intense acidity was off-putting, and it had an unpleasant smell. By the time Pasteur arrived in Lille, beet liquor distillers were desperate. The father of one of his students, a wealthy industrialist, came to Pasteur to ask if he might look into the problems the local industry was facing. Though he had little experience with biology, Pasteur threw himself into finding a solution. Soon, his wife was writing her father that Pasteur was “up to his neck in beet juice.”

In the cellar of an old sugar factory, Pasteur assembled a makeshift lab equipped with little more than a primitive coal-fired incubator. But he also used something that was surprisingly rare in a chemistry lab of the period: a standard student microscope that he borrowed from the university. Chemists of the time measured and weighed and experimented to arrive at abstract chemical formulas. Biologists and physiologists were the observers, using microscopes to explore the fine structure of their subjects. By actually observing fermentation in progress, Pasteur began to understand it in ways most of his fellow chemists did not.

Everyone knew that the key to making alcohol was the process of fermentation. However, not much concrete was known about what was actually happening during the process. Brewers and vintners knew about the presence of yeast in ferments. Antonie van Leeuwenhoek had been the first to see yeast cells, microscopic ovals that floated aimlessly under the lens of his microscope. But since they didn't appear to move by their own power, he did not consider them to be living organisms. The very word “yeast” was simply a derivation of the Old English word for “foam.” By the time Pasteur began to contemplate fermentation, few scientists suspected that yeast cells, even if alive, were anything more than bystanders in the fermentation process. Antoine Lavoisier, a towering figure in the early history of chemistry, had practically ignored the presence of yeast entirely in his own attempt to describe fermentation. But in the late 1830s, a handful of scientists started to suspect that yeast were actually masses of microorganisms, and that they were key to fermentation.

Using his polarimeter, Pasteur saw that the ferment itself showed signs of asymmetry. From his study of quartz crystals, Pasteur realized that
asymmetry meant the ferment was the product of living organisms, since only they could produce chemicals with purely asymmetric molecules. As the process went along, he also noticed that the yeast cells were changing shape, growing from little ovals into longer ones, then pinching off and dividing into themselves. He began to understand that they were living and, in fact, the
source
of the alcohol produced during fermentation.

Pasteur's hypothesis had all kinds of ramifications beyond distillation. Fermentation was not just a key to making alcohol; it was also suspected to be the chemical process that led to decay in all organic matter. By tracing the root of spoiling to microorganisms, Pasteur had opened the door to a new way to preserve food. In early 1862, another French scientist, Claude Bernard, showed that milk, wine, and beer could be boiled to kill off bacteria and mold, preventing spoilage and drastically increasing the amount of time they could be safely stored. The process came to be known as “pasteurization.”

B
Y THE TIME
Pasteur delivered his address on spontaneous generation at the Sorbonne, the discovery of pasteurization was nearly a year old. Yet Pasteur did not even see fit to mention it. To him, it paled in comparison to the metaphysical importance the French placed on spontaneous generation.

He first turned to the question of spontaneous generation in 1859, the year Darwin's
Origin
made its debut in England. Pasteur wrote to a colleague that he was going to “take a decisive step by resolving the famous question beyond the shadow of a doubt.” The year before, Félix Pouchet had submitted a paper to the French Academy of Sciences claiming that experiments he had conducted proved the existence of spontaneous generation. Pouchet was a brilliant physician and naturalist, and the author of several well-received books on the natural philosophy of Aristotle. He was also a devout Catholic, much more so than Pasteur, who rarely attended church. Pouchet took pains to say that he was not challenging the idea of Christian creation as the original source of life, but merely trying to revive the question in the Augustinian sense. The process, he argued, was just one of the many tools used by God to propagate life. Nonetheless, Pouchet
came under fire from conservative scientists who charged him with reviving materialist ideas discredited by Cuvier in his supposed victory over Geoffroy.

Pouchet couldn't have picked a worse time to submit his paper. Catholicism was growing increasingly politicized and ever more powerful in France. Its interests had become synonymous with the interests of the state. In 1848, the country held its first election by direct popular vote. Napoleon Bonaparte's nephew, Louis-Napoleon Bonaparte, won an overwhelming victory on the backs of a campaign that appealed directly to Catholics, promising to restore Catholic political power, to elevate the place of church in society, and to support the pope in Rome. Three years later, he staged a coup d'état and proclaimed himself Emperor Napoleon III. Censorship was restored, and some six thousand political opponents were sent to prison, some to penal colonies in French colonies abroad. Victor Hugo, who had become a living embodiment of the French national conscience, publicly denounced the emperor as a traitor and fled the country for a self-imposed exile that would last the rest of Napoleon III's reign.

Pouchet also had to deal with the issue of how his ideas played into the publication of Darwin's
Origin
, which dredged up all the old polarization on the issue that had surrounded the debate between Cuvier and Geoffroy. Those tensions grew in 1861 with the first appearance of a French version of
Origin
. The book had been translated by Clémence Royer, a radical who would one day become the first woman appointed to the French Academy of Sciences. Royer's translation included her own preface containing a lengthy diatribe against the Catholic Church. Darwin, who knew nothing of Royer when he agreed to accept her as translator, wrote to his friend, the American botanist Asa Gray, that Royer was “one of the cleverest and oddest women in Europe” who “hates Christianity and declares that natural selection and the struggle for life will explain all morality, the nature of man, politiks.” Darwin added that Royer planned to write her own book on these subjects, “and a strange production it will be.”

In the early part of his career, Pasteur often picked fights with more established scientists as a way of enhancing his own prestige. Pouchet was
sixty-two at the time they began to clash, and he was considered the country's leading expert on spontaneous generation. Pasteur was thirty-seven. Though he had impressed many with his work on fermentation, he had spent little of his career tackling biological questions.

In order to topple Pouchet's results, Pasteur looked for flaws in the older experimenter's methods. Part of the difficulty in studying spontaneous generation was the need to exclude air. At the time, people believed that all organisms needed oxygen to survive, so oxygen inevitably had to be reintroduced to create conditions in which spontaneous generation could occur. Yet his experience with fermentation led Pasteur to wonder whether microorganisms weren't simply being introduced through the air itself, carried by dust. To test his hypothesis, he devised a simple apparatus that would henceforth become an iconic symbol of Pasteur's genius: the swan-necked flask. As beautiful as it was functional, it was round at its base and had a long, thin neck, curved like the neck of a swan. Such a neck would allow air to pass, but not dust or, presumably, airborne microorganisms, which would find themselves trapped in the neck's many curves. He placed broth in his flasks, the same substance once used by John Needham, boiled it in place, and then sealed some flasks with a flame while leaving others exposed to the air. He let them sit for days, then weeks. Those left sealed remained sterile, but more significantly, those left open to the air did too. As a final coffin nail, he broke the seal on the ends of the swan necks of the closed flasks and left them open to the air. They, too, remained sterile.

A commission set up by the Academy of Sciences to judge the contest declared Pasteur the “decisive” winner, which paved the way for his triumphant lecture at the Sorbonne. In reality, the deck had been stacked against Pouchet from the outset. The commission was overwhelmingly composed of conservatives, many of whom had already stated their outright rejection of spontaneous generation on the grounds that it was a materialist doctrine. In their judgment, they wrote, Pasteur not only had demonstrated that “brute matter cannot organize itself in such a way as to form an animal or plant,” but also had proved the theory of vitalism, that a “life force has been passed on successively through an uninterrupted chain of being
since creation.” The outcome secured Pasteur's reputation as a master of the experimental method, and his identification of microorganisms that traveled through the air would lead him closer to one of his most important scientific contributions, the germ theory of disease. But the question of spontaneous generation was not quite dead. A new debate was brewing just across the English Channel, where support for the Darwinist concept of evolution seemed to grow stronger by the day.