Teaching evolution was never illegal everywhere, but several U.S. states did criminalize it in public schools during the 1920s. These laws were driven by a collision between rising Protestant fundamentalism and the growing presence of evolutionary science in American classrooms. Tennessee’s 1925 Butler Act was the most famous example, making it a misdemeanor to “teach any theory that denies the story of the Divine Creation of man as taught in the Bible, and to teach instead that man has descended from a lower order of animals.” Violating the law carried a fine of $100 to $500 per offense. These bans remained on the books for decades before courts and legislatures finally dismantled them.
The Religious Movement Behind the Bans
The anti-evolution laws grew out of a broader conflict within American Christianity known as the Fundamentalist-Modernist controversy. Starting around 1910, conservative Protestants organized around a set of core beliefs they considered non-negotiable: the authority of Scripture, the virgin birth of Christ, the reality of biblical miracles, and the bodily resurrection. A widely circulated series of pamphlets called “The Fundamentals: A Testimony to the Truth” helped galvanize this movement into a political force. Modernist Christians, by contrast, embraced science and philosophy as tools for interpreting faith and meeting contemporary needs.
Evolution sat at the center of this divide. Fundamentalists saw Darwin’s theory as a direct assault on the Bible’s account of human origins. By the early 1920s, their alarm had shifted from theological debate to political action. Public schools were expanding rapidly, and the idea that children were being taught they descended from animals struck many parents and church leaders as an attack on their faith funded by their own tax dollars. Three states passed outright bans on teaching evolution during this period, and several others passed resolutions condemning it.
The Arguments for Banning Evolution
William Jennings Bryan, a three-time presidential candidate and the era’s most prominent anti-evolution crusader, framed the issue not just as religious but as democratic. His core argument was about who controls public education. A teacher in a public school, Bryan insisted, was a state employee paid with public money and therefore “under instructions from the State.” Freedom of speech still applied to the teacher as a private citizen, but not in the classroom. Bryan asked: “What right has a little irresponsible oligarchy of self-styled ‘intellectuals’ to demand control of the schools of the United States, in which twenty-five millions of children are being educated at an annual expense of nearly two billions of dollars?”
Bryan also argued the bans were defensive rather than offensive. “The majority is not trying to establish a religion or to teach it,” he said. “It is trying to protect itself from the effort of an insolent minority to force irreligion upon the children under the guise of teaching science.” He maintained that evolution was still a “hypothesis,” not proven fact, and that teaching unproven guesses to children “who are not yet able to think” was irresponsible. These arguments resonated with millions of Americans who saw their local schools as extensions of community values, not laboratories for scientific inquiry.
The Scopes Trial of 1925
Tennessee’s Butler Act became the subject of the most famous courtroom drama of the decade. Shortly after the law passed in 1925, a high school teacher named John Scopes agreed to serve as the defendant in a test case organized by the American Civil Liberties Union. The resulting trial, quickly dubbed the “Scopes Monkey Trial,” drew national attention largely because of the lawyers involved: Bryan argued for the prosecution, while the celebrated attorney Clarence Darrow defended Scopes.
Scopes was found guilty and fined $100. But the case didn’t resolve anything legally. On appeal, the Tennessee Supreme Court overturned his conviction on a technicality: the judge, not the jury, had imposed the fine, which violated state law for fines exceeding $50. The court found the Butler Act itself constitutional but recommended dropping the case to avoid further controversy. The law stayed on the books, and the broader legal question of whether states could ban evolution from classrooms went unanswered for another four decades.
How the Bans Finally Fell
Anti-evolution laws lingered far longer than most people assume. Tennessee didn’t repeal the Butler Act until 1967, more than 40 years after it was enacted. Arkansas kept its own ban even longer, setting the stage for the legal showdown that would settle the issue nationwide.
In 1968, the Supreme Court unanimously struck down Arkansas’s anti-evolution law in Epperson v. Arkansas. Justice Abe Fortas, writing for the majority, focused on the First Amendment’s establishment clause, which prohibits the government from promoting one religion over another. The Court found that the Arkansas law had both the purpose and the effect of advancing religious beliefs. Government, Fortas wrote, “may not be hostile to any religion or to the advocacy of nonreligion; and it may not aid, foster, or promote one religion or religious theory against another.” Banning evolution from public schools solely because it conflicted with a particular reading of the Bible crossed that line.
The Creationism Workaround and Its Defeat
After Epperson made outright bans unconstitutional, opponents of evolution shifted strategies. Rather than prohibiting evolution, states like Louisiana tried requiring that “creation science” be taught alongside it. Louisiana’s Balanced Treatment Act mandated that whenever evolution appeared in a classroom, creation science had to receive equal time.
The Supreme Court struck this down too, in the 1987 case Edwards v. Aguillard. The Court found that the Louisiana law had no legitimate secular purpose. It did not protect “academic freedom,” as legislators claimed, because it actually restricted what teachers could cover. The law required curriculum guides and resource panels for creation science but provided nothing equivalent for evolution. Most critically, the Court concluded that “creation science” as defined by the legislature was not science at all. It “embraces the religious teaching” that a supernatural being created humankind, and the law’s “primary purpose was to change the public school science curriculum to provide persuasive advantage to a particular religious doctrine that rejects the factual basis of evolution in its entirety.”
With Edwards, the Court closed the most obvious legal paths for removing or undermining evolution in public schools. The ruling established that any law designed to promote a religious alternative to evolution, or to discourage the teaching of evolution for religious reasons, violates the First Amendment. The debate over evolution in American classrooms has continued in subtler forms since then, but the legal question of whether states can ban it was settled decisively across these two Supreme Court cases.