Where does all the war, racism, genocide, terrorism, violence, and cruelty so endemic to human civilization come from? Why do humans exploit and massacre each other so regularly? Why is our species so violence-prone? Could it be that we oppress and kill each other so readily because our abuse and slaughter of animals has desensitized us to the suffering and death of others?

The "domestication" of animals—the exploitation of goats, sheep, cattle, and other animals for their meat, milk, hides, and labor that began in the Near East about eleven thousand years ago—changed human history. In earlier hunter-gatherer societies there had been some sense of kinship between humans and animals, reflected in totemism and myths which portrayed animals, or part-animal/part-human creatures, as creators and progenitors of the human race. However, mankind crossed the Rubicon when Near Eastern herdsmen and farmers started castrating, hobbling, and branding captive animals to control their mobility, diet, growth, and reproductive lives. In the first civilizations that emerged in the river valleys of ancient Egypt, Mesopotamia, India, and China, the exploitation of animals for food, milk, hides, and labor was so firmly established that these civilizations sanctified the notion that animals existed solely for their benefit. This allowed humans to use, abuse, and kill them with total impunity.

This domination, control, and manipulation of animals served as the model for the enslavement/domestication of people. It led humans to place other humans—captives, enemies, strangers, and those who were different or disliked—on the other side of the great divide where they were vilified as "beasts," "pigs," "dogs," and "rats." Calling people animals has always been an ominous sign because it sets them up for humiliation, exploitation, and murder. As Leo Kuper writes in Genocide: Its Political Use in the Twentieth Century, "The animal world has been a particularly fertile source of metaphors of dehumanization."

From Slaughterhouse to Death Camp

In his autobiography, My Life and Work (1922), Henry Ford revealed that his inspiration for assembly-line production came from a visit he made as a young man to a Chicago slaughterhouse. "I believe that this was the first moving line ever installed. The idea [of the assembly line] came in a general way from the overhead trolley that the Chicago packers use in dressing beef." A Swift and Company publication from that time described the division-of-labor principle that so impressed Ford: "The slaughtered animals, suspended head downward from a moving chain, or conveyor, pass from workman to workman, each of whom performs some particular step in the process."

In the early 1920s Ford's weekly newspaper, the Dearborn Independent, published a series of articles based on the text of the Protocols of the Elders of Zion, an anti-Semitic tract that had been circulating in Europe. Ford published a book-length compilation of the articles entitled The International Jew, which was translated into most European languages and widely disseminated by anti-Semites, chief among them the German publisher Theodor Fritsch, an early supporter of Hitler. Thanks to a well-financed publicity campaign and the prestige of the Ford name, The International Jew was hugely successful both domestically and internationally.

The selective breeding of animals and plants prompted delegates to ask why such techniques could not be applied to human beings.

The International Jew, or The Eternal Jew as it became known in Germany, quickly became the country's number one bestseller in the 1920s. After it came to the attention of Hitler in Munich, he used a shortened version of it in the Nazi propaganda war against the Jews. Baldur von Schirach, the leader of the Hitler Youth movement, said at the postwar Nuremberg war crimes trial that he became a convinced anti-Semite at age seventeen after reading The Eternal Jew. "You have no idea what a great influence this book had on the thinking of German youth. The younger generation looked with envy to symbols of success and prosperity like Henry Ford, and if he said the Jews were to blame, why naturally we believed him."

Ford, who based his automobile assembly line on the model of the American slaughterhouse, exported to Germany both his anti-Semitism that helped make the Holocaust happen and the method the Germans used to kill Jews. Although Ford stopped publishing the Dearborn Independent in late 1927 and agreed to withdraw The International Jew from the book market, copies of it continued to circulate in large numbers throughout Europe and Latin America into the late 1930s.

On January 7, 1942—exactly one month after the Japanese attack on Pearl Harbor that brought the United States into the war—Ford wrote a letter to Sigmund Livingston, national chairman of the Anti-Defamation League, expressing his disapproval of hatred "against the Jew or any other racial or religious group." But by that time, Einsatzgruppen (German mobile killing squads) in the East had already murdered hundreds of thousands of Jewish men, women, and children, and the first German extermination camp at Kulmhof (Chelmno) was already operational.

From Animal Breeding to Genocide

The desire to improve the hereditary qualities of the human population had its beginnings in the 1860s when Francis Galton, an English scientist and cousin of Charles Darwin, turned from meteorology to the study of heredity (he coined the term "Eugenics" in 1881). By the end of the nineteenth century, genetic theories, founded on the assumption that heredity was based on rigid genetic patterns little influenced by social environment, dominated scientific thought.

The Eugenics movement in America began with the creation of the American Breeders' Association (ABA) in 1903. At the second meeting of the ABA in 1905, a series of reports about the great success achieved in the selective breeding of animals and plants prompted delegates to ask why such techniques could not be applied to human beings. The creation of a Committee on Human Heredity (Eugenics) at the third ABA meeting in 1906 launched the American Eugenics movement.

Its leader was poultry researcher Charles B. Davenport, who served as the director of the Eugenics Record Office and described Eugenics as "the science of the improvement of the human race by better breeding." He looked forward to the time when a woman would no more accept a man "without knowing his biological-genealogical history" than a stockbreeder would take "a sire for his colts or calves who was without pedigree."

Sterilization began in America in 1887, when the superintendent of the Cincinnati Sanitarium published the first public recommendation for the sterilization of criminals, both as a punishment and a way to prevent further crime. Authorities used the same method to sterilize male criminals that farmers used on their male animals not selected for breeding—castration. Castration was the preferred method used to sterilize male criminal offenders until 1899, when vasectomy was adopted because it was more practical.

By 1930 more than half of the American states passed laws that authorized the sterilization of criminals and mentally ill people. By then compulsory sterilization had widespread support in the United States, with college presidents, clergymen, mental health workers, and school principals among its strongest supporters. The United States quickly became the model for other countries that wanted to sterilize their "defectives." Denmark was the first European country to pass such a law in 1929, followed in rapid succession by other European nations.

In Germany Eugenics established deep roots in medical and scientific circles after World War I. In 1920 two respected academics—Karl Binding, a widely published legal scholar, and Alfred Hoche, a professor of psychiatry with a specialty in neuropathology—published Die Freigabe der Vernichtung lebensunwerten Lebens (Authorization for the Destruction of Life Unworthy of Life). In it they argued that German law should permit the mercy killing of institutionalized patients who were lebensunwert ("unworthy of life") because their lives were "without purpose" and a burden to their relatives and society. Beginning in the 1920s, the Rockefeller Foundation and other American foundations provided extensive financial support for eugenics research in Germany. By the time the Nazis came to power, more than twenty institutes for "racial hygiene" had already been established at German universities.

The Law on Preventing Hereditarily Ill Progeny, which the Nazi government issued on July 14, 1933, required the sterilization of patients suffering from mental and physical disorders in state hospitals and nursing homes. By then, the United States had already sterilized more than fifteen thousand people, most of them while they were incarcerated in prisons or homes for the mentally ill. America's sterilization laws made such a favorable impression on Hitler that he looked to the United States for racial leadership. "I have studied with great interest the laws of several American states concerning prevention of reproduction by people whose progeny would, in all probability, be of no value or be injurious to the racial stock." Nazi Germany's sterilization efforts quickly surpassed those of the United States, reaching between 300,000 to 400,000 people.

Germany's eugenics campaign entered a new, deadly phase in 1939 when Hitler issued a secret order for the systematic murder of mentally retarded, emotionally disturbed, and physically infirm Germans who were an embarrassment to the myth of Aryan supremacy.

Once "defective" children were identified and institutionalized, doctors and nurses either starved them to death, or gave them lethal doses of luminal (a sedative), veronal (sleeping pills), morphine, or scopolamine. The "euthanasia" program—named Operation T4, or simply T4—transported adults to special killing centers outfitted with gas chambers. T4 killed between seventy and ninety thousand Germans before it was officially stopped in August 1941. In 1942, not long after German psychiatrists had sent the last of their patients to the gas chambers, the Journal of the American Psychiatric Association published an article that called for the killing of retarded children ("nature's mistakes").

Like the American Charles Davenport, Heinrich Himmler, head of the Nazi S.S. and a main architect of the Final Solution, began his Eugenics education with animal breeding. His agricultural studies and experience breeding chickens convinced him that since all behavioral characteristics are hereditary, the most effective way to shape the future of a population—human or otherwise—was to institute breeding projects that favored the desirable and eliminated the undesirable.

Rudolf Höss, the commandant of Auschwitz who also had a farming background, wrote in his autobiography after the war that the original plan for Auschwitz had been to make it into a major agricultural research station. "All kinds of stockbreeding was to be pursued there." However, in the summer of 1941 Himmler summoned him to Berlin to inform him of the fateful order for the mass extermination of the Jews of Europe, an order that soon turned Auschwitz into "the largest human slaughterhouse that history had ever known." By the summer of 1942, Auschwitz was a vast, full-service Eugenics center for the improvement of animal and human populations, complete with stockbreeding centers and the Birkenau extermination camp for the culling of Jews, Gypsies, and other "sub-humans."

The breeding and killing of animals that was the centerpiece of American and German eugenics produced a number of key T4 personnel, including those sent to Poland to operate the death camps. Victor Brack, T4's chief manager, received a diploma in agriculture from the Technical University in Munich, while Hans Hefelmann, who headed the office that coordinated the killing of handicapped children, had a doctorate in agricultural economics. Before spending more than two years at the Hartheim euthanasia center in Austria, Bruno Bruckner had worked as a porter in a Linz slaughterhouse. Willi Mentz, an especially sadistic guard at Treblinka, had been in charge of cows and pigs at two T4 killing centers, Grafeneck and Hadamar. Treblinka's last commandant, Kurt Franz, trained with a master butcher before joining the S.S. Karl Frenzel, who worked as a stoker at Hadamar before being posted to the Sobibor death camp, had also been a butcher. For German personnel sent to Poland to exterminate Jews, experience in the exploitation and slaughter of animals proved to be excellent training.

The German Jewish philosopher Theodor Adorno once said: "Auschwitz begins whenever someone looks at a slaughterhouse and thinks: they're only animals." The exploitation and slaughter of animals instills in us the habit of withholding our compassion from those we define as Other and hardens our hearts to their suffering and death. Our detachment and indifference toward their fate makes us more inclined to commit atrocities against each other. What we do to animals, we sooner or later do to members of our own species. As the Yiddish writer Isaac Bashevis Singer observed, "There is only one little step from killing animals to creating gas chambers a la Hitler."

We need to eradicate the notion that there exist in the world groups of sentient beings not entitled to our empathy and protection. Extending the circle of our compassion to include all living beings will make the world a safer and more humane place. It's the only thing that will.