THE BERLIN OTTO WARBURG returned to at the end of the war was not the Berlin he had left behind four years earlier. Up until the last days of the fighting, most Germans remained convinced that they would emerge victorious. It was more than self-delusion. As late as the spring of 1918, German forces were winning battles on the Western Front. When the momentum began to shift back to the Allies, the German propaganda operation successfully glossed over the bad news. The denial was so complete that some German troops returned home after their nation’s defeat to celebratory parades.
Kaiser Wilhelm II was no more in touch with the reality of the battlefield than ordinary German citizens. Not until a meeting with his military advisers on November 9, 1918, did he realize that all was lost and his days as emperor were over. A German general recalled that Wilhelm’s expression betrayed “amazement, then piteous appeal, and then—just a curious wondering vagueness.” The general went on: “He said nothing, and we took him—just as if he were a little child—and sent him to Holland.”1
By that point, Germans had been starving for years. The food shortages began early in the war after the British navy cut off supply routes to the Central Powers. As butter and meat grew increasingly scarce, food riots erupted throughout the country—more than 50 in 1916 alone. The government did its best to calm the public. The Germans were encouraged to eat turnips and even young crows, which, according to the Ministry of Agriculture, could make for a “suitably pleasant alternative” to traditional meat dishes. But whatever plan the government proposed, it was never enough. More than 400,000 Germans died from malnutrition or starvation during the war. One foreign visitor in Berlin witnessed a horse die in the street, only to have its flesh ripped off by a descending throng of German housewives.2
The naval blockade remained in place until June 1919, when the Germans signed the Treaty of Versailles. There is no record of Warburg ever going hungry, but he, too, had learned the value of a piece of meat. At one point during the war, Warburg exploited his military privilege to send half a sheep to Emil Fischer, the legendary University of Berlin chemist who had taught him to synthesize polypeptides. Fischer did not respond immediately, but several weeks later Warburg received a congratulatory telegram informing him that he had been made a “professor” at the University of Berlin, a title Warburg had no plausible claim on.3
If the food shortages did not affect Warburg’s meals, they did influence his science. When Emil Warburg had argued that his son should be released from military duty because his photosynthesis research might help feed Germany, he had not been bluffing. Warburg resumed his photosynthesis research upon his return from the war, and the prospect of growing food more efficiently would remain one of his scientific aims for decades.
Warburg was now finally able to work at the Kaiser Wilhelm Society lab that had been promised to him shortly before he rode off to war with the uhlans. The Institute for Biology resembled a small bourgeois Berlin apartment building of the era. Warburg’s lab occupied the top floor. The conditions were not what Warburg had envisioned before the war. Germany was bankrupt, and so, too, were many of the business titans who had promised to fund the new Kaiser Wilhelm institutes. In November 1920, a desperate Warburg sent a request for financial support to his cousin, Paul Warburg, a prominent American banker who had recently helped establish the US Federal Reserve System. Aware that Americans—even German Americans—might not be feeling especially charitable toward Germany after the war, Warburg mentioned that his own lab had played no role in producing gas used on the battlefield and that he didn’t share the reactionary views common at German universities.4
Whatever money his famously wealthy Warburg relatives were able to provide, it wasn’t enough. Warburg requested an additional 10,000 marks from the Kaiser Wilhelm Society, only to be told there was no money to give. He was encouraged to apply to the Emergency Association of German Science, but Warburg pointed out to the administrators that he didn’t have a secretary. An official at the Kaiser Wilhelm Society sent a secretary to Warburg’s lab. Warburg gave her a sheet of paper and instructed her to type a single sentence: “I require 10,000 marks.” He then signed the paper and sent off what might be the most outrageous grant application in the history of science.5
Warburg received the money, but his financial situation remained challenging. “The decline of science in Germany is, as you can imagine, rapid, especially because young scientists do not earn enough to live from,” Warburg wrote to Loeb in 1922. Warburg moved ahead as best he could. In keeping with the Kaiser Wilhelm Society’s emphasis on total freedom for its scientists, Warburg’s cell physiology division of the Institute for Biology was known simply as “the Warburg department.” In control of his own lab for the first time, Warburg ran it like a unit of the kaiser’s army. The employees were expected at the lab six days a week, from 8 a.m. to 6 p.m.—after which they would still have to find time to read and write scientific articles. As one member of Warburg’s lab remembered, there “were no reasonable grounds, apart from death, for not working.” Warburg liked to point out that working hours had been much longer when he was a young scientist.6
At weekly lab meetings on Fridays, there was no discussion. Warburg would announce the latest findings from the institute then declare the meeting over. In his heart, one colleague said, Warburg always remained “a staff officer in plain clothes.”7 “I have been the anvil long enough,” Warburg once told Hans Krebs, referencing a line from Goethe, “now I want to be the hammer.”8
Though young scientists came to Warburg’s lab for brief stints, most of the work was carried out by a small group of highly skilled instrument specialists, several of whom Warburg hired away from the Siemens Company. These technicians arrived with little, if any, training in chemistry, which was exactly how Warburg wanted it. While a number of them became world-class biochemists in their own right, Warburg liked that his technicians, unlike young scientists, had few academic interests of their own. To keep the technicians motivated, Warburg made them coauthors on his papers. He even shared some of his Nobel Prize money with Erwin Negelein, a technician turned biochemist who worked on many of Warburg’s most important experiments.9
In the 1920s, at least, Warburg’s behavior generated more wonder than bitterness. During their 30-minute lunch breaks, the young scientists would gather in a common room and gossip about Warburg’s eccentricities over their boiled eggs and milk. Krebs, who joined the lab in the mid-1920s, sat directly across from Warburg’s laboratory bench and remembered that Warburg would regularly insult whichever scientist he happened to be feuding with at the time. But Krebs saw the softer side of Warburg as well. When Krebs first arrived in Warburg’s lab, he wasn’t yet familiar with the complicated equipment. Warburg took the time to teach him what he needed to know and was ready to listen whenever Krebs had something important to discuss. He was an authoritarian, Krebs recalled, but his brilliant accomplishments and basic integrity had earned him the right to make demands of others.10
Given the relentless work schedule, there was little chance for anyone to maintain a relationship outside of the lab. And it was not obvious to German scientists of the time that love should be allowed to interfere with work. When Krebs, in a letter to his father, mentioned that he hoped to one day meet a girl, his father suggested that he read Rocco’s “Love will not suffice” aria from Fidelio.11
Yet Warburg did now have an important new person in his life. Shortly after the war, he had hired a young man, Jacob Heiss, to serve as a full-time, live-in assistant at his home in the wealthy Berlin suburb of Lichterfelde. Heiss had served in the war and had been recommended to Warburg by his military colleagues. The role was akin to a butler or house boy. For the remaining five decades of Warburg’s life, the two would rarely be apart.
While the precise nature of the relationship between Warburg and Heiss is impossible to know, every sign points to a loving homosexual partnership. Heiss “did everything he could to support and protect Warburg,” Krebs wrote, “and to make his life as congenial as possible.” After Warburg fell off his horse in 1924 and fractured his pelvis, he never rode again unless Heiss rode with him. They went to the opera together and vacationed together. On at least one occasion, Warburg agreed to an overseas invitation on the condition that Heiss be invited as well.12
Heiss, 15 years Warburg’s junior, was the taller and stockier of the two. He was born in the town of Kirn and had a number of siblings, but little else is known about his background. He favored fedoras and checkered sports coats, apparently sharing Warburg’s taste for fine things. By the 1950s, Heiss was bald and doing his best to manage a comb-over that would sometimes fly upward in a gust of wind. Like Warburg, Heiss was a lover of animals and raised his own chickens. In various photos, he can be seen standing by Warburg’s side, stiff and serious, in the manner of a bodyguard.13
Given the norms of the period, Warburg and Heiss were as open as was possible for a homosexual couple. A bachelor with a live-in male attendant wasn’t a particularly common arrangement, and homosexuality could still be punished by imprisonment. In 1907, the revelation that the kaiser’s closest friend was gay had turned into a national scandal.
Though Heiss was responsible for Warburg’s home, over the years he would grow increasingly involved in Warburg’s work life as well. After the war, Warburg made him the institute’s official administrator, meaning that Heiss and Warburg spent nearly every hour together. Peter Ostendorf, a glassblower who worked at the institute, said that Heiss’s role was to prevent anyone or anything from disrupting Warburg’s research. Often that meant yelling angrily at the staff. Heiss once told Ostendorf that if the press showed up at an event honoring Warburg, Ostendorf should knock the cameras out of the photographers’ hands. “I never saw Heiss laugh,” Ostendorf recalled.14
On one occasion, Ostendorf remembered, Heiss appeared at the door of his workshop and shouted, “Are you trying to kill me, Mr. Ostendorf?” Ostendorf didn’t understand. He soon discovered that his crime was failing to alert Heiss that an auditor had arrived at the lab. Heiss directed Ostendorf to chase the man off the property with one of the enormous Great Danes that he and Warburg kept as pets.
Warburg’s cousin, the banker Eric Warburg, recalled that when he visited Heiss and Warburg for lunch in the late 1930s, Heiss—Eric Warburg referred to him as Warburg’s “man-servant”—served the meal. When Otto asked his cousin if he should sell his shares in Deutsche Bank, Eric said that he might as well go ahead, given that the dividends had just been paid out. Otto, hesitant, suggested that they continue the discussion when Heiss was done serving them. After lunch, Heiss took a seat on a chair against the wall, leaving Eric Warburg with the impression that he wasn’t permitted to sit at the table. Warburg now asked Heiss the same question about his Deutsche Bank shares that he had posed to his cousin over their meal, only to receive a more detailed analysis. “Heiss,” Eric Warburg wrote, “was as well-informed in financial matters as our whole investment department.”15
Heiss seems to have had a mind for chemistry as well. After the Second World War, he regularly exchanged letters with Dean Burk, the head of cell chemistry at the National Cancer Institute, who became Warburg’s greatest champion in the 1950s. Despite possessing only a high school education, Heiss was able to discuss Warburg’s research in considerable detail, a skill he likely needed as the institute’s administrator. Krebs wrote that Heiss “did much in calming and appeasing Warburg’s emotions when they were raised by controversy and resentment,” and that may be so. But Heiss’s letters give the impression of a true believer, a Sancho Panza always willing to affirm Warburg in his quixotic battles against the scientific establishment.16
Though Warburg’s friends and relatives came to accept Heiss as a fixture in his life, often ending their letters with “regards to Heiss,” in the early years they expressed their distaste. In a diary entry from 1933, Warburg’s sister Lotte noted that many were saying that Warburg was “a homo and in the hands of Jacob.” “Sometimes I almost believe it,” Lotte continued, “because his nature has changed too much. He is spiteful against all, vicious and absolutely unreliable.”17
Elisabeth Warburg struggled with her son’s lifestyle up until her death in 1935. In a letter to Lotte in 1931, she expressed her concern that Warburg wasn’t living according to “regular family relations” and would never pass on his genius to any offspring. On one occasion, after Elisabeth pressured him to find a wife, Otto said that he did not want to end up with a wealthy woman in a marriage motivated by reason rather than love. Elisabeth, sensing an opening, suggested that a “marriage based on reason” could, in fact, be an excellent idea. “Think about all that you can do with a girl who is that rich,” she wrote. “And you can let go of all the rest—the lectures and exams, and you won’t need to slave away like Papa did.”
Warburg’s sarcastic response might have been accompanied by an eye roll: “From then on it’s just horseback riding and getting dolled up.”18
THE NEW STABILITY in Warburg’s personal life came against the backdrop of a nation in upheaval. After Germany failed to make reparations payments dictated by the terms of Versailles, French and Belgian forces crossed into the Ruhr Valley, the industrial region critical to the German economy. The local Germans went on strike with the support of their government, which now had to cover their wages the only way it could: by printing more and more money. The ensuing inflation left German money worthless. By November 1923, an American dollar was worth 4 billion marks. Some Germans took to hauling wheelbarrows of cash around to buy food. Others joined violent militias. Jacques Loeb, watching Germany crumble from afar, was horrified by “the blind passions of the reactionary forces.” “I feel strongly,” Loeb wrote to Warburg, “that our civilization is seriously threatened.”19
The problems, Loeb grasped, were about far more than money. The reoccupation of the Ruhr Valley had reopened the psychic wounds from World War I that had only just begun to heal. More and more Germans would now treat those wounds with a salve of denial and scapegoating. Germany hadn’t lost the war to other countries, according to this narrative. That was impossible. The German military was too powerful, the German people too racially superior. Germany could only have lost due to sabotage from within. The Germans, as the popular saying went, had been “stabbed in the back” by Jewish Bolshevik traitors.
If preoccupied by his work, Warburg was not unaware of what was happening outside his lab. In 1923, he encouraged Otto Meyerhof to accept an offer in America, telling him that he would be unlikely to find a decent position in Germany given the “prevailing anti-Semitism.” Warburg came to this conclusion even though Meyerhof had won the Nobel Prize only the year before. In a letter to Loeb later that year, Warburg wrote that Germany was still waiting for “a turning point” and that he wasn’t sure it would arrive in time.20
Though Warburg had almost no contact with his famous cousins in banking at the time, he would have felt the weight of his last name. The Protocols of the Elders of Zion, the notorious Russian hoax that detailed a Jewish plan for global domination and influenced countless Nazis, including Hitler, first appeared in German translation in 1920. Among the capitalist “criminals” said to be responsible for the disastrous state of the nation was Otto Warburg’s cousin, Max.
The new German government had urged Max, a famous banker, to take part in the reparations negotiations at Versailles, hoping the presence of a Warburg might inspire better terms from the Americans—Max’s brothers, Paul and Felix, were both influential American bankers. Max resisted at first, aware that it could be disastrous for a Jew to be seen as responsible for the inevitably harsh terms of the treaty. Though Max eventually relented, he would soon regret it: “Whatever one chose, one chose hell,” he later said of the negotiations. “It was simply a question, which hell promised to be of shorter duration.”21
On November 16, 1923, Emil Warburg captured the mood in a letter to Einstein, who was abroad at the time. “You know how much it must mean to me that you stay with us, as you are the only colleague with whom I have a closer personal relationship and productive scientific exchanges,” Emil wrote. Nevertheless, he felt it would be “too irresponsible” to encourage Einstein to return to Berlin, given the “increasingly dire” situation.
In the same letter, Emil told Einstein that he had recently played music with his daughter Käthe, who sang a Schubert song with the line “the world becomes more beautiful day by day.” Added Emil Warburg, “That’s over now.”22
THE YEAR 1923 is significant in German history for another reason. It is the year that Otto Warburg published his first paper on the peculiar manner in which cancer cells eat. In 1908, at the Naples Zoological Station, Warburg had found that a sea urchin egg will consume six to seven times more oxygen after fertilization. The discovery made perfect sense to Warburg. A fertilized egg needs to grow, he reasoned, and so needs more oxygen to react with nutrients and generate energy.
Warburg anticipated that cancer cells would also take up more oxygen to fuel their growth, but there was no way to be certain of this with the tools available to him in 1908. At that time, Warburg had measured the breathing of sea urchin eggs only indirectly, through a chemical analysis of the oxygen in the water surrounding the eggs. He needed a more direct and reliable approach to advance his science, and he knew where to look. Researchers had begun to measure human breathing rates by strapping frightening-looking masks onto people’s faces. The principle was simple. Every breath we take involves an exchange of gases: oxygen flows into the system, carbon dioxide flows out. The mask was connected by tubes to a rubber bag, and the rate of breathing could be measured by the time it took for carbon dioxide to fill the bag. It was an excellent device for measuring the metabolism of an entire body, but it left Warburg with a problem: How could he strap a mask onto the face of a microscopic cell?
Warburg might have given up and moved on to a more feasible experiment. But then he would not have been Otto Warburg. The same self-regard that made him so insufferable also made him a remarkable scientist. When Warburg encountered an obstacle in the lab, the question wasn’t whether he would overcome it, but how.
A turning point came in March 1912, when, on a visit to the lab of an English colleague, Warburg spotted what he later described as a “beautiful blood gas apparatus.” The device was nothing more than a U-shaped tube, known as a manometer. The tube was partially filled with fluid and connected to a small glass vessel containing blood cells. When the oxygen bound to the blood cells was released, the pressure inside the tube would change and cause the fluid to rise on one side of the “U” and fall on the other. Warburg might have been the only person alive who could have looked at the device and seen beauty.23
It wasn’t the first manometer Warburg had observed. Physicists had long used manometers to measure changing gas pressures for the study of inorganic processes. Emil Warburg had himself devised a special manometer for his study of ozone gas. And Otto had already realized that a manometer could be used to measure the breathing of cells. The beauty of the manometer he spotted in England was in the small technical modifications that made it more suitable for the study of life.
Warburg immediately began to use this new manometer in his research on respiration and photosynthesis, along the way introducing a series of his own technical innovations until he had arrived at a device that would become known around the world as the “Warburg manometer” or “Warburg apparatus.” For the rest of his life, the manometer was Warburg’s signature tool in the laboratory.
Even after perfecting the manometer, Warburg had another major hurdle to overcome before he could accurately measure the breathing of cancer cells. The manometer allowed him to put a mask over small slices of a tumor, but cutting these slices inevitably damaged the outer layers of cells. If the slice was too thin, a significant percentage of the cells in the sample might not be able to breath properly. If the slice was too thick, meanwhile, the oxygen would take too long to reach the inner layers of cells and this, too, could lead to errors. A tenth of a millimeter off in either direction and Warburg would not be able to trust his results.
To solve the problem, Warburg devised a complicated mathematical formula that could determine the precise width required for each specific tumor sample. Warburg’s manometer and “tissue slice technique,” as it was known, became critical tools for an entire generation of researchers. In the following years, these innovations made possible countless fundamental discoveries in biochemistry. But first they forever changed our understanding of cancer.
If growing cancer cells were like sea urchin embryos, they could be expected to take up oxygen at an unusually high rate. But when Warburg put the cancer tissue he had sliced from the tumor of a rat into a glass vessel and attached it to his manometer, the drama was not in what happened but in what failed to happen. The fluid in the tube did not rise or fall any faster than it would have with noncancerous cells. Despite their rapid growth, the cancer cells were not taking up more oxygen. Instead, they were gorging themselves on glucose and fermenting it.
Warburg’s research had arrived at a peculiar place. Fermentation was the biochemical process behind beer and bread. It was not supposed to have anything to do with cancer. The development of agriculture, and thus modern civilization itself, can be traced, in part, to a passion for fermenting grains into alcohol. The ancient Sumerians credited fermentation to Ninkasi, goddess of beer, whose “lofty shovel” was said to sprout barley. Jews eat matzah on Passover as a reminder that the Israelites hurrying out of Egypt did not have time to let their bread rise—which happens because some types of fermentation give off carbon dioxide.24
In the nineteenth century, fermentation was among the most important and fiercely debated topics in science. By then it was clear that the process produces alcohol and carbon dioxide in some cases and lactic acid (as in the making of cheese, yogurt, or sauerkraut) in others. But little was known beyond that. Many of the leading chemists of the era were convinced that fermentation was merely a by-product of oxygen reacting with simple sugars, much as rust appears when oxygen reacts with iron. Others insisted that fermentation was the work of living organisms. According to this view, grape juice left to sit in a barrel turned alcoholic not because it was decaying but because tiny, invisible animals were feeding on the juice and leaving behind alcohol as a waste product.
Louis Pasteur proved that the second group was correct, but he did not stop at crediting microbes for fermentation. In 1860, he made the observation that would forever shape Warburg’s thinking on cancer. Hunched over his microscope, gazing at a drop of fluid, Pasteur could see a tiny universe: rodlike specks moving about in a state of silent frenzy. Pasteur had seen similar scenes of microscopic life many times before, and yet, on that particular day, the bacteria weren’t doing what they were supposed to do. Instead of gravitating toward the edge of the slide, where they could find more of the oxygen that every living organism needed to live and breathe, they were moving away from the oxygen, to the slide’s center.
For Pasteur, seeing bacteria turn away from oxygen was akin to watching a group of people in the ocean choosing to drown themselves rather than swim to the shore. But the most shocking part wasn’t that the bacteria were forgoing oxygen; it was that doing so did not seem to bother them in the least. Pasteur, having already proved that fermentation is the work of living organisms, had now found something even more surprising: fermenting organisms could use oxygen, but they didn’t appear to need it. Overturning the most basic assumptions of biologists of the era, Pasteur declared that fermentation was “life without air.”25
Determined to understand why an organism would ever choose fermentation over respiration, Pasteur carried out additional experiments. When he sent a stream of oxygen through the microbe-filled fluid, he saw that the production of alcohol or carbon dioxide would suddenly cease, indicating that the fermentation had stopped. Pasteur concluded that when an organism could use oxygen, it would do so. Fermentation, according to Pasteur’s framework, was a backup process that activated and sustained the life of microbes when oxygen wasn’t readily available. This fundamental relationship between respiration and fermentation is now known as the “Pasteur effect,” and it was Otto Warburg who named it.
By the time Warburg began to study cancer, Otto Meyerhof had arrived at another breakthrough while studying muscle tissue. It wasn’t only microbes that turned to fermentation. Animal cells could ferment glucose into lactic acid just like the invisible organisms that feed on the sugars in milk. It was a remarkable and, at the time, unsettling demonstration of the unity of nature. Humans and single-celled organisms weren’t nearly as different as many wanted to believe.
For Warburg, there was an even more significant lesson in Meyerhof’s discovery. Meyerhof had found that our cells turn to fermentation for the same reason that, according to Pasteur, microbes turn to fermentation. In both cases, fermentation was understood as an act of desperation, a means of generating energy if there is not enough oxygen available. This is what happens during vigorous exercise, when our heaving lungs can’t deliver oxygen to our muscles quickly enough; the soreness we feel after intense exercise is a by-product of the lactic acid our fermenting cells produce.
Warburg’s explanation for why cancer cells ferment even when oxygen is plentiful—the process that would later become known as “the Warburg effect”—was almost tautological: if a cell had access to oxygen and nevertheless chose fermentation, it could only be because something fundamental was broken and preventing the cell from using the oxygen properly. To test this theory, Warburg poisoned growing cells with chemicals that disrupted their use of oxygen. The result was exactly what Pasteur would have predicted: as respiration decreased, fermentation increased.
The more these cells fermented, Warburg reasoned, the more likely cancer became, because the energy of fermentation was “inferior,” a cheap, inefficient substitute for the energy provided by respiration. Fermentation couldn’t support the elaborate microscopic machinery of healthy tissues any more successfully than a small backup generator might keep the lights in a large building on for an extended period. Fermenting cells “have lost all their body functions and retain only the now useless property of growth,” Warburg wrote. “Thus, when respiration disappears, life does not disappear, but the meaning of life disappears.”26
Over the course of the 1920s, Warburg and other researchers would repeat his rat tumor experiments on other cancer cells again and again. They tested human cancers from the skin, throat, intestines, and penis and saw cancer cells overeating and fermenting glucose every time. Evidence of the fermentation was found not only in cancer cells in petri dishes but in the unusual levels of lactic acid in the blood of living animals with cancer. Everywhere Warburg looked, the result was the same: cancer cells were fermenting, sucking up glucose, and spitting out lactic acid—as much as 100 times the lactic acid normal tissue would produce, in some cases.
Fermentation was not merely less efficient than respiration. To the aristocratic Warburg, the process was also less noble, worthy only of “the lowest living forms.” In cancer, Warburg once wrote, oxygen is “dethroned.”27
WARBURG ONCE WARNED another scientist about the hazard of forming theories based on experimental findings. Such interpretations “are always wrong,” Warburg said, insofar as they will inevitably change as new discoveries arise. As Warburg put it, “Good experiments are right forever.” But for all the times he criticized others for arriving at conclusions that went far beyond their experimental findings, he could rarely resist the temptation himself.28
Warburg’s initial studies had not shown that fermenting cancer cells were damaged and using significantly less oxygen than healthy cells. The studies showed only that, in addition to burning glucose with oxygen, the cancer cells were also taking up lots of extra glucose and fermenting it. There was no reason to assume that fermentation arose only in response to a cell’s inability to power itself with oxygen, but Warburg couldn’t set aside his reverence for Pasteur, who died believing that yeast ferment only when normal breathing with oxygen is insufficient. If the backup generator is on, Warburg concluded, then the power station must be damaged.
Had Warburg thought more broadly about respiration and fermentation, he might have wondered whether there was another explanation for his findings. In particular, he might have considered whether the type or quantity of the food available to the cells might be influencing the way they processed energy. The evidence for this possibility was there from the start. In his very first experiments on cancer cells in the 1920s, Warburg had detected an increase in fermentation only after adding extra glucose to the cell culture. And Warburg was likely aware of the latest cancer feeding studies, given that he knew Peyton Rous, a scientist who had picked up that line of investigation where Ehrlich’s institute had left off.
Rous worked at the Rockefeller Institute, placing him within the same international circle of scientists as Loeb and Warburg. He is famous for his 1911 discovery that a particular form of cancer in chickens could be spread by a virus. Not long after wondering about the role of viruses in cancer, Rous moved on to another question: could giving an animal very little food slow a cancer’s growth or prevent cancer altogether? Ehrlich and Moreschi had transplanted tumors into mice and then fed them different diets. Rous took their research one step further. It wasn’t only transplanted tumors that were influenced by an animal’s diet. Tumors that would typically arise spontaneously, Rous found, could be prevented or impaired by limiting the amount of food an animal ate.
Rous was underfeeding animals a full decade before Warburg discovered that cancer cells overeat and ferment glucose. In a letter to Warburg sent in December 1924, Rous practically begged him to investigate the metabolism of the chicken cancers, even offering to cover some of the expenses. Rous did not even give Warburg a chance to say no. “I am sending some tubes of the dried and powdered chicken sarcoma,” he wrote. “If you do not care to have the material, someone else may desire it.”29
Warburg accepted the powdered chicken cancer, but his interest was in how the cancer cells used oxygen, not in how much or how little food the birds might be eating. To most cancer scientists in the 1920s, the feeding studies were already old news. Though still convinced that cancer was a problem of metabolism, Ernst Freund, the Austrian scientist who detected glucose in the blood of cancer patients, had himself moved on to other interests.
WARBURG’S FIRST cancer discoveries occurred as political fires continued to sweep across Germany. These fires burned especially hot in Munich, where Hitler had returned at the end of the war. The information office of the German military, wary of uprisings, hired Hitler to join a group of instructors tasked with instilling a hatred of bolshevism in the troops. It would prove the perfect job for a man who knew nothing but resentment.
The historian Karl Alexander von Müller was in Munich at the time and was among the first to notice Hitler’s talent for public speaking. Years later, he could still remember Hitler’s “light blue, fanatically cold, gleaming eyes” and how his listeners had watched him, transfixed. “I had the strange feeling that he had got them excited” and that their interest had simultaneously “given him his voice.” Hitler’s power over his listeners, Müller wrote, was almost “like a magic trick.”30
Hitler was aware of his newfound power. He once referred to himself as “the greatest actor in Europe.” As a New York Times reporter observed in 1930, Hitler’s followers seemed less interested in the specifics of his speeches than in his delivery. But Hitler did cling to a vaguely coherent set of beliefs until the end of his life. He began with a basic premise: Germany was sick. The signs of this illness, in Hitler’s deranged view, could be found in every aspect of the nation’s social and political life, from the weakness of its military, to its failed educational system, to the poverty of its cultural creations. Germany had become “a slowly rotting world” in which things “seemed to have passed the high point and to be hastening toward the abyss.”31
The cure was to return to forceful and decisive action without fear of consequence. Nature, even its most brutal aspects—especially its most brutal aspects—was the highest ideal. Any departure from the ruthlessness of nature was, in turn, a form of decay. Brutality wasn’t an unfortunate consequence of Hitler’s other beliefs; it was the core idea. Only weak and corrupt Jews quibbled over ethical considerations, as he saw it. “Eternal hunger” and the drive to reproduce, Hitler wrote, “are the rulers of life.”32
Hitler was never an original thinker. Philosophers from Hegel to Nietzsche had called for a world in which decisiveness and bold action were to be freed from moral concerns. And in the 1920s, Darwinian thinking was widespread even among those who did not use it to justify racism. Warburg, in fact, would use the same Darwinian language as Hitler on one occasion. Only, as Warburg expressed in a letter to Loeb in 1922, the villains subverting the natural order were not Jews but his fellow scientists at the Kaiser Wilhelm Society. The “well-fed schoolmarms,” Warburg wrote, left the best, independent-thinking scientists to “perish” while they stuffed the last crumbs from their tables “into their own pockets.”33
After the starvation of the war years and the success of the English naval blockade, Hitler was particularly fixated on Germany’s long-standing quest to produce enough food to feed its population. The problem, Hitler concluded, was that Germany would never have enough fertile land to grow food for its large population. He recognized that it was possible to increase crop yields through scientific innovation—Warburg’s plan to make photosynthesis more efficient was one possible approach—but by the 1920s, Hitler had already rejected all such ideas. “[F]or a certain time,” the need for more food can be counterbalanced “by greater industriousness, more ingenious production methods or special thriftiness,” he wrote, “but one day all of these means will prove inadequate.”34
For Hitler, the deeper problem with growing more food through innovation was that it did not involve dominating and killing off other races. According to the laws of nature, the strong were supposed to eat and thrive, but the weak also had to starve and die. What Germany needed was not merely better agricultural methods, but the will to fight and conquer more Lebensraum, or “living space.” “[F]rom the distress of war grows the bread of freedom,” Hitler wrote. “The sword breaks the path for the plow.”35
Hitler had a specific “living space” in mind. He dreamed of a new “German East” that would be settled by German soldiers. After doing away with the locals, they would plow the fertile Ukrainian grain fields and end German food insecurity forever. “I need the Ukraine,” Hitler once said, “so that they cannot starve us out, as during the last war.”36
The war Hitler longed for was coming. It would be, in part, an attempt to swallow up as much glucose as possible.