There is a haunting familiarity to the arguments defending Planned Parenthood’s sale of body parts from aborted babies for medical research: an echo of another era of medical innovation amid moral ambiguity. Then, as now, the response of cultural leaders — especially religious leaders — is a story about the corruption, and potential renewal, of Western civilization.

Today we’re told there is no other way to achieve the research results we desire, because fetal tissue is a “uniquely rich source” of stem cells, which provide invaluable clues to human development. Second, we’re led to believe that research on aborted babies will heal diseases, eradicate physical defects, and greatly enhance the human condition. And finally, we’re warned that prohibiting medical experimentation of this kind would mean “subordinating science to religion.”

Well, now. It ought to give us pause that each of these claims was enlisted a century ago when it was believed that the tools of evolutionary science could be applied to improve the human species. “What Nature does blindly, slowly, ruthlessly, man may do providently, quickly, and kindly,” English anthropologist Francis Galton told a learned society in London in 1909. “As it lies within his power, so it becomes his duty to work in that direction.”

What “duty” did Galton have in mind? It was the obligation to improve the human gene pool through the scientific methods of selective breeding and sterilization. Galton coined the term eugenics — “good birth” — to promote his social vision. What began as a fringe, pseudo-scientific exercise became, in barely a generation, mainstream thinking among scientific and academic elites. “It must be introduced into the national conscience,” Galton said, “like a new religion.”

And so it was. Beginning in 1912, a series of international conferences were held in London and New York, creating a global venue for a burgeoning class of eugenicists and their supporters. No longer on the margins of respectability, they were affiliated with institutions such as Harvard, Princeton, and Columbia; they became leaders in America’s premier scientific organizations.

Religious authorities, especially those in the liberal wing of the Christian church, did not want to be seen as the “enemies” of science. As Christine Rosen explains in her insightful book Preaching Eugenics, many ministers became zealous evangelists for the new gospel of genetic engineering. Prompted by the American Eugenics Society, hundreds of American clergymen participated in a national “eugenics sermon contest.” The Reverend Kenneth Arthur declared in his winning entry: “If we take seriously the Christian purpose of realizing on earth the ideal divine society, we shall welcome every help which science affords.”

Poverty, crime, family disintegration — there were indeed reasons to worry about the quality of the genetic stock of Western societies, thanks to the social breakdown instigated by the Industrial Revolution. Add to this the psychological trauma of the First World War. The supposedly “Christian” nations of Europe — among the most advanced in human history — had nearly destroyed one another in a global suicide pact. In the postwar years, books with titles like The Twilight of the White Races (1926) and Sterilization of the Unfit (1929) typified the mood.

Meanwhile, many Americans watched with deep anxiety as millions of “undesirable” immigrants from southern Europe (including my Italian grandparents) washed across America’s shores in the aftermath of the Great War. Eugenics advocates got the attention of Congress in 1920, when the House held hearings on the “Biological Aspects of Immigration.” The testimony of eugenicist Harry Laughlin included these chilling lines: “Our failure to sort immigrants on the basis of natural worth is a very serious national menace. By setting up a eugenical standard for admission demanding a high natural excellence of all immigrants . . . we can enhance and improve the national stamina and ability of future Americans.”

What began as a fringe, pseudo-scientific exercise became, in barely a generation, mainstream thinking among scientific and academic elites.

Establishing and enforcing a genetic threshold for immigrants proved implausible. So how to best identify and isolate the biological “defectives” among them? Marriage laws were considered ineffective; immigration restrictions couldn’t stop defective people who were already here from procreating.

Thus the United States — with its passion for technological and scientific advances — earned the noxious distinction of becoming the first nation in the West to legalize compulsory sterilization. Beginning with Indiana in 1907, many states passed sterilization laws “to prevent procreation of confirmed criminals, idiots, imbeciles, and rapists.” Supreme Court Justice Oliver Wendell Holmes, a political progressive and eugenics advocate, authored the 1927 Court decision upholding Virginia’s sterilization laws: “Three generations of imbeciles are enough.”

Not everyone succumbed to the siren song of human perfectionism. For conservative and orthodox Christians, the eugenics movement represented a frontal assault on the Bible’s teaching about human nature: a reduction of the individual to mere biology.

Two of the 20th century’s greatest Christian authors, C. S. Lewis and J. R. R. Tolkien, used their literary imagination to launch a counterattack. Both men began their academic careers at Oxford in the 1920s, when the eugenics movement was in full swing. They came to share a deep distrust of scientific progress — the kind of “progress” that threatened to degrade or enslave human beings.

In their epic works of heroic fiction, Lewis and Tolkien depict their characters as physical and spiritual beings, responsible for their eternal souls even as they are constrained by their earthly nature. The worlds of Narnia and Middle-earth are also filled with non-human races — elves, dwarves, hobbits, centaurs, etc. — who nonetheless share this human attribute. The point must not be missed: No creature — no matter how small or apparently insignificant — deserves to be treated as a means to an end. Like no other authors of their postwar generation, Lewis and Tolkien insisted on the unique moral status of the human person.

At its heart, Tolkien’s War of the Ring is a struggle to preserve the essential freedom and humanity of the inhabitants of Middle-earth. Thus, in The Lord of the Rings, we glimpse the frightful prospect of genetic engineering — the creation of robotic orcs — in an effort to extend the dictatorship of Mordor throughout the world. In Lewis’s Perelandra, the second novel in his Space Trilogy, we meet Professor Weston, a physicist and devotee of “emergent evolution,” a quasi-scientific process by which the human species thrusts its way “upward and ever upward” toward physical and mental perfection. “Man in himself is nothing,” Weston explains. “The forward movement of Life — the growing spirituality — is everything.” Weston becomes an essentially satanic figure.

But, some will ask, isn’t conservative Christianity an enemy of scientific progress if it seems to challenge the authority of the Bible? Isn’t the debate over fetal tissue really just another conflict between reason and revelation?

For people of faith, the problem is not science, but scientism: the belief that science can explain every facet of human existence from Nature itself.

It is true that Christian fundamentalists have sometimes discredited themselves in their approach to scientific controversies. But we shouldn’t blame the traditional teachings of the Bible for bad behavior. It’s worth remembering that the “Bible thumpers” at the Scopes “Monkey” Trial were also some of the most vigorous opponents of human eugenics; they were dead right about the morally debased agenda of the eugenicists. As Rosen points out, it was progressive Christianity that portrayed the eugenics movement as a mandate from heaven. “The evidence yields a clear pattern about who elected to support eugenic-style reforms and who did not,” she writes. “Religious leaders pursued eugenics precisely when they moved away from traditional religious tenets.”

The eugenics agenda eventually fell out of favor: The conscience of the West was quickened by the sight of the ovens at Auschwitz, the ultimate manifestation of the logic of eugenics. Yet the scientific community, with its rising cultural authority, had helped to persuade a generation of an urgent biological necessity. Margaret Sanger, the founder of Planned Parenthood, was among the ranks of the true believers. Speaking at Vassar College in 1926, Sanger warned of a social crisis — “an increasing race of morons” — unless sterilization policies were widely implemented.

For people of faith, the problem is not science, but scientism: the belief that science can explain every facet of human existence from Nature itself.

In that worldview, there are few restraints on what science can do — must do — in order to improve mankind’s physical well-being. This is what C. S. Lewis meant when he warned of “the abolition of man” — the negation of human dignity in the name of progress, or compassion, or humanity, or science itself. Lewis lived long enough to witness firsthand the dreadful progeny of this idea: “For the power of Man to make himself what he pleases means, as we have seen, the power of some men to make other men what they please.”

The passage of time, it seems, has only strengthened this power and the fearsome temptation to use it.

Joseph Loconte is an associate professor of history at the King’s College in New York City and the author of A Hobbit, a Wardrobe, and a Great War: How J.R.R. Tolkien and C.S. Lewis Rediscovered Faith, Friendship, and Heroism in the Cataclysm of 1914-1918.