Modern genetics shores up science that sparked celebrated 1925 case

Monday, July 24th 2000, 12:00 am
By: News On 6

Seventy-five years ago, high school teacher John Scopes had just been convicted for teaching that man evolved from a lower form of life. He was fined $100.

Scopes moved from Tennessee to Chicago to study geology. Defense attorney Clarence Darrow prepared to appeal the conviction and would move on to another high-profile defense, in a Detroit murder case. Prosecutor William Jennings Bryan, just five days after the famous evolution trial ended, lay down for a nap and never woke up.

And scientists, already convinced that the case for evolution was sound, continued gathering data. The decades since have turned up new evidence for evolution under countless rocks, in the physical forms of animals and plants, and in the chemical stuff that humans themselves are made of.

"If anybody thought the jury was still out ... [after the trial], boy, the evidence has become so overwhelming," said geneticist Eric Lander.

Outside scientific circles, the jury is in fact out.

Last year the Kansas Board of Education voted to remove certain questions about evolution from standardized state tests. A 1999 Texas Pollfound that 64 percent of Texans think the biblical account of creation should be taught in public schools along with evolution. This year, Oklahoma's state textbook committee tried to require publishers to put a disclaimer in science textbooks saying that evolution is a "controversial theory."

But biologists see no controversy. The case for evolution is virtually indisputable, they say. And modern genetics – a field that has exploded only in the last 25 years – has confirmed and expanded the understanding of how life evolved.

Last month, scientists celebrated the first draft of the human genome, the genetic instruction book for building the human body. That book, scientists say, contains arguments for evolution on practically every page.

"All this evidence just piles up," said Dr. Lander, of the Whitehead Institute for Biomedical Research in Cambridge, Mass.

In 1925, when what many called the trial of the century was held in Dayton, Tenn., biologists' evidence for evolution came in the form of fossils. Many naturalists of the day were convinced that all Earth's life forms, extinct and alive, were descended from simple, one-cell organisms.

But evidence from genetics, the study of inheritance, was limited. Scientists knew genes existed but still couldn't examine them directly.

"We didn't even know what genes were," said Kenneth Miller, a biochemist at Brown University in Providence, R.I.

Now scientists know that genes are made of a spiral molecule called deoxyribonucleic acid, or DNA.

"That knowledge made it possible to test the entire framework of evolution," Dr. Miller said.

Thanks to the discovery of DNA's structure, researchers studying genes have seen just what Charles Darwin deduced when he put forth his theory of evolution. Scientists have seen genes mutate and shuffle as they pass from one generation to the next, providing the natural variations that either persist or die out. Scientists have been able to alter genes to make modern animals look like their primitive ancestors, in effect rewinding the movie of life's evolution.

Moreover, Dr. Miller said, researchers studying genes have discovered gene after gene shared by species as different as fruit flies and people. This historical record left in genes today supports the historical record left by fossils.

If genes were not shared, "you would have had the opportunity to blow Darwinian evolution right out of the water," he said. "The molecular evidence confirmed the entire evolutionary scheme" that all life on Earth is related "in a way that was absolutely astonishing."

In the Scopes trial itself, however, scientific evidence wasn't much of an issue. Although the lawyers defending Scopes brought scientific experts to town to testify, the jury never heard their arguments.

The judge – rightly so, according to Vanderbilt University historian Paul Conkin – declared that the purpose of the trial was not to pit evolutionists against anti-evolutionists. The purpose, Dr. Conkin said, was to determine whether Scopes had violated the law. Tennessee's Butler Act, passed in March 1925, had made it illegal for teachers in the state's public schools 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."

Darwin himself – the British scientist whose name today is synonymous with evolution – was not central to the issue at the time, said Dr. Conkin. Darwin was not the first scientist to propose that people evolved from lower animals, and other theories persisted.

For opponents of evolution, "the issue was not whether Darwin was correct or not," Dr. Conkin said, "but whether evolution took place and whether humans had a genetic connection to other primates."

If evidence for evolution had been allowed in the Scopes trial, and genetic science was where it is today, the trial could have lasted far longer than its eight days. Genetic evidence for evolution appears in scientific journals weekly.

"Evolution is not just a theory," Dr. Lander said. "Evolution is put to work every day in the ... lab."

Cancer researchers, for instance, study genes in yeast, mice and fruit flies to understand tumors in people. Tumors develop when cells divide over and over, breaking out from their normal constraints. Many of the genes that control how cells divide in simple organisms like yeast also control how cells divide in people, and in cancers.

That means, scientists say, that people inherited these important genes from a life form that existed many millions of years ago, one that predates both yeast and people and was an ancestor for both. Some genes shared between people and yeast are still similar enough today that a human gene can perform perfectly when scientists slip it inside a yeast cell.

The argument for evolution strengthens further, geneticists say, with the discovery of certain genetic snippets – which are virtually identical across many species – that don't have any obvious function. They appear to be mere trimmings on the genetic cake. So these snippets aren't likely to be instances of nature reinventing a useful genetic wheel to serve a similar purpose in different species. Rather, scientists say, they are another sign that modern life forms have common ancestors.

For instance, researchers have discovered such a genetic frill in humans, chimps and gorillas, a sort of scar left over from an ancient viral infection. In 1998 in the Journal of Virology, researchers reported on the remnants of a virus whose genetic material is embedded in one of the human chromosomes. The virus's genetic material was in the equivalent spot on equivalent chromosomes from chimps and gorillas.

"The only way that we and our primate relatives could share that is if we shared a common ancestor in which that infection took place," said Dr. Miller, a Roman Catholic who has written and lectured that belief in evolution is compatible with a belief in God.

The virus today is dead, with no apparent function.

Because of such viral remnants, "you can argue that we're not just descended from apes, we're also descended from viruses," said Bryan Cullen, a virologist from Duke University Medical Center in Durham, N.C.

In the 75 years since the Scopes trial, such arguments have not often emerged from the scientific arena into the legal or the political one. Science's case for evolution played no role even in the immediate aftermath of the Tennessee case.

The state's Supreme Court overturned Scopes' conviction only on a technicality: The judge – not the jury, as state law required – had set Scopes' fine. The higher court urged the state attorney general not to retry the case.

In 1967, the Butler Act was finally repealed, but the controversy over evolution did not die.

"At the Scopes trial, there were many people there who believe the biblical account, so what Darwin said could not be true," said Dr. Conkin. "It remains that way today."


Further reading

For more information on the Scopes trial, see:

Summer for the Gods: The Scopes Trial and America's Continuing Debate over Science and Religion, by Edward J. Larson.

When All the Gods Trembled: Darwinism, Scopes and American Intellectuals, by Paul K. Conkin.