The 1926 case Tennessee v. John Thomas Scopes is a favorite liberal American story. On one side, a substitute accused of teaching evolution, the famed progressive attorney Clarence Darrow, and science itself. On the other, the state of Tennessee, creationism, and the populist demagogue William Jennings Bryan, who by the end of the trial was only days from death. Scopes lost the battle, but reason and progress won the war and the film adaptation. The Scopes Monkey Trial, as it was called, is a progressive touchstone, and in the minds of many it continues to describe the difference between the two mainstream American political ideologies.

When one revisits the primary material, however, the mainstream liberal narrative is far too simple. Jennings Bryan railed against evolution, true, but not just evolution as we understand the theory today. His never-delivered closing statement indicted the “dogma of darkness and death” as a danger to the country’s moral fabric. It sounds far out, but at the time evolution came with a social agenda that its proponents taught as fact. Jennings Bryan didn’t use its name; today, we call it eugenics.

Scopes was charged for teaching from a textbook called A Civic Biology: Presented in Problems, published in 1914. The book taught Darwin’s doctrine as fact, but it didn’t leave his conclusions there. The author, George William Hunter, not only asserted the biological difference of races, he insisted on the vital importance of what he called “the science of being well born”—eugenics. Like most progressives of the time, Hunter believed in “the improvement of man” via scientific methods. That meant promoting personal hygiene, proper diet, and reproductive control. A Civic Biology also has suggestions for what to do with “bad-gened” people, in a section called “The Remedy.” “If such people were lower animals,” the books says, “we would probably kill them off to prevent them from spreading. Humanity would not allow this, but we do have the remedy of separating the sexes in asylums or other places and in various ways preventing intermarriage and the possibilities of perpetuating such a low and degenerate race. Remedies of this sort have been tried successfully in Europe.”

The textbook was wrong, both about degenerate genes and humanity’s near-term tolerance for genocide. Read between the twin specters of human engineering, The Holocaust and the American slave-breeding industry—the abolition of which was younger than Jennings Bryan—the warning in his closing argument seems not only warranted, but prophetic:

Science is a magnificent material force, but it is not a teacher of morals. It can perfect machinery, but it adds no moral restraints to protect society from the misuse of the machine. It can also build gigantic intellectual ships, but it constructs no moral rudders for the control of storm-tossed human vessels. It not only fails to supply the spiritual element needed, but some of its unproven hypotheses rob the slip of its compass and thus endanger its cargo.

“Some of its unproven hypotheses rob the slip of its compass and thus endanger its cargo” is a near-perfect criticism of evolutionary theory and the era’s progressive thought as a whole. And if today’s liberals were to revisit their ideological foundations with some attention, they might not like what they see.