He pursued his science not as some renegade propelled solely by evil and bizarre impulses but rather in a manner that his mentor and his peers could judge as meeting the highest standards. . . . The notion of Mengele as unhinged, driven by demons, and indulging grotesque and sadistic impulses should be replaced by something even more unsettling. Mengele was, in fact, in the scientific vanguard, enjoying the confidence and mentorship of the leaders in his field. The science he pursued in Auschwitz, to the extent that we can reconstruct it, was not anomalous but rather consistent with research carried out by others in what was considered to be the scientific establishment.

To this, one might add a single footnote: the German “scientific establishment” had long ago sold its soul, and measuring stick, to the Devil. The scientists in Berlin and Graz who readily accepted disembodied heads and eyes and skeletons from Mengele’s institute had been morally corrupted long before the samples arrived. No one suggests that Mengele’s twin or eye-color research was of lasting value, despite its diabolical origins. (This might be said, for instance, of the Nazis’ rocket research: the science was sound, even if the missiles went to the wrong cities.) The genetics of eye color was never going to be cracked by the gruesome business of collecting a lot of eyes. The anthropologists in Berlin and Munich had already convinced themselves that their fanatic inventorying and artifact-collecting impulse was so virtuous that it made questions of morality empty. Mengele was not, it turns out, a mad scientist. It was worse than that. He was participating in a mad science.

Marwell surveys, with a kind of aghast wonder, the comforts of life for Nazi doctors living amid so much death. They had a special “subcamp,” twenty miles from the gas chambers, that served as a rustic retreat. There were regular conjugal visits, and a steady flow of dinner parties among the S.S. officers and their wives. All this as the smoke rose in the camp nearby. Mengele was happy in this world—photographs show him smiling, and even the inmate-slave who drew his baths called him “polite.” Whenever some sense of morality intruded on this tightly enclosed communal sphere, the special unity of the bad actors held the group together. Again and again, the S.S. leaders, from Himmler on down, emphasized to their followers that they had already crossed the bar: if they failed in their task, the children of the survivors would come for them. It is the collective logic of all extremism. Within a group of killers, only acts of sadistic cruelty in which all are made to join can guarantee solidarity. And so we see the omnipresence of hazing rituals among motorcycle gangs and mafiosi: you make your bones by burning your bridges. The fanatic leader convinces his adherents not that this is the only way forward but that there is no way of turning back.

Mengele’s flight from Europe after the war was startlingly slow. Stopping off in Munich, perhaps to collect records of his research which he had sent on from Auschwitz, he spent more than three years under an assumed name as a hired hand at a Bavarian farm. (One of perhaps a hundred bitter ironies in his post-Auschwitz life: most S.S. men, like their victims, had been tattooed, in their case to receive the right blood type if they were wounded and needed a transfusion. This made them easy to identify after the war, but Mengele had managed to evade the marking, probably out of vanity.)

He made his way, in 1949, to South America, with the help of the Red Cross—along with the Catholic clergy’s “ratline,” one of the two most efficient escape routes for ex-Nazis—obtaining a passport more or less on demand. Once he arrived in South America, moving from Argentina to Paraguay and eventually settling in Brazil, he was protected by a makeshift network of German and Austrian expats. Mengele shared a coffee-and-cattle operation for years in Brazil with a Hungarian couple who kept his secret in exchange for a new farm, paid for by his protectors.

The Israelis tried to keep track of him, but never tried to kidnap him. This was, in part, a matter of politics. No doubt Israel had to balance its desire to capture war criminals against the price of alienating potentially helpful South American governments. And, logistically, Mossad, like any government agency, had limited means and many missions. Infuriatingly, Mengele’s life on the run did not include much running: he managed the farm, kept a wary eye on his imagined pursuers, and had plenty of time to get married, go on holidays, and even correspond regularly with his son, Rolf, who lived in Germany. Mengele died in 1979, during one of those holidays; he had a stroke while swimming.

His friends buried him, under his assumed name of Wolfgang Gerhard, and then, pressured by the West German and Brazilian police, disclosed the location of his grave. But the Germans and the Israelis—as well as Americans, who by now had taken up the Mengele hunt, at the political urging of the New York senator Al D’Amato—were unconvinced that they had the right corpse. They gave Mengele and his associates too much credit for fiendish movie-style secrecy—extensive plastic surgeries and faked deaths—when he had mostly been kept safe by lassitude on the part of his pursuers and moral indifference on the part of his protectors.

In June of 1985, teams of pathologists, forensic anthropologists, and other investigators from both Germany and the United States—including Marwell himself, working for the Justice Department’s Office of Special Investigations—descended on São Paulo to determine if the body was indeed Mengele’s. In the strangest irony, the methods used to identify the criminal were essentially versions of the physical anthropology that Mengele had been trained in. Measurements were taken, the pubic symphysis was examined for wear; femurs were cross-sectioned, and ribs were inspected to assess how “cupped” they had become. Finally, the Germans introduced a brand-new technique: two high-resolution videos—one of the corpse’s skull, the other of a photograph of Mengele when alive—were superimposed. It was Mengele, and “closure,” that strange beast, was captured at last. All that microscopic Teutonic precision was now directed not to the malignant fantasy of creating racial categories but to distinguishing one man from all others. What exists is individuals, and what we can capture is their quiddities; the larger collectivities—of nation, class, mind, character—to which they belong are still too manifold for measurement.

Götz Aly, the German historian whose “Hitler’s Beneficiaries” is one of the more highly praised works on the Third Reich published in the past two decades, has just brought out a new book in English, “Europe Against the Jews: 1880-1945” (Metropolitan), and it throws some postscript-like light on the Mengele case. Aly has two motives in writing his book. First, to show just how widespread, pan-European, and ideologically complete European anti-Semitism was. From France through Poland and on into Romania and Hungary, each country had, in the nineteenth century, an anti-Semitic establishment, often anchored in the Catholic right but just as often in the Socialist left, which was, in its language, as virulent as the later, Hitlerian kind. Anti-Semitism that envisioned the removal and, implicitly, the extermination of the Jews was everywhere. Nobody needed encouragement to persecute Jews. The circumstances of war made it possible, but many, throughout Europe, had been eager to do so as soon as they could.

His second line of inquiry is more subtle: Why did they want to persecute the Jews so badly? He distinguishes classic medieval-style anti-Semitism, in which Jews were simply aliens, from a modern strain, in which they had become, unacceptably, betters. A new sort of competition had arisen in which the Jews had seized a first-mover advantage. In the nineteenth century, they arrived, before anyone else, at an understanding that, in the new world of modernity, competitive advancement—doing well on exams—would provide an alternative to advancement through bloodlines. Why the Jews did so well in societies that depended on some form of test-taking is a complicated historical question, though it may be as simple as that the tradition of Talmudic study could easily be “exapted” for the purpose. Paradoxically, only when the “national” groups entered this competition themselves and began to catch up did their hatred of the Jews take on a new ferocity. “As the gap in education closed, the degree of friction between Jews and majority populations increased,” Aly writes. “Envy is born of social proximity, not of the distance between two cleanly separated groups.”

The 1894 Dreyfus case, the original falling domino of what was to come, fits this pattern perfectly, and it makes sense that it happened in France, the first European nation to insure “careers open to talent.” Captain Dreyfus’s great sin was not being a Dreyfus but being a captain. And though Aly doesn’t cite this instance, his scheme maps perfectly onto the lives of the Nazis: Hitler was enraged at the Jews in Vienna not because Jews were practicing the arts instead of agriculture but because they wouldn’t let him into art school. Goebbels was a failed philosophical novelist, not a rabble-rouser. The circles of populist authoritarians, then and now, tended to be filled with embittered B-minus competitors.

And so we come to the last and still the most morally instructive thing about studying the Nazis now: we can see how tightly the elimination of the Jews was bound to a hatred of cosmopolitanism. Although huge numbers of the Jews who perished in the mass killings were poor religious Jews from Eastern Europe, many peasants and peddlers and small merchants, the main enemy, as Mengele understood, had always been the educated Jews of Western Europe. When an S.S. doctor wondered aloud why all the poor Jews of the East had to be killed, he recalled Mengele explaining that “it was precisely from this reservoir of people that the Jews drew new power and refreshed their blood. Without the poor but supposedly harmless Eastern Jews, the civilized West European Jews would not be capable of survival. Therefore, it is necessary to destroy all Jews.” The masses of poor religious Jews in Poland were almost accidental to the effort; the real target was the élite, who brought with them the bacillus of cosmopolitanism.

In Tom Stoppard’s great new play, “Leopoldstadt,” the study of a thoroughly assimilated Jewish family which begins in Vienna’s golden period before the Great War—a Star of David sits atop their Christmas tree—the final, shattering scene is set in the nineteen-fifties. A man whose immediate family escaped in time comes home and asks, happily, about the relatives he had known as a boy. He lists one name after another: Ernst? Auschwitz. Hanna? Auschwitz. All his flawed and idiosyncratic relatives turn out to have been murdered by the Mengeles of the world. The audience, unique in my experience, is silent at the end, almost unable to applaud the actors. But the invocation is exact: it was the destruction of such harmless and happy Viennese cosmopolitan families that Hitler, who discovered anti-Semitism as a cure-all for his frustrations as a young and unsuccessful artist in Vienna, most desired. He was willing to destroy European civilization in order to achieve it, and he did. ♦