Understanding evolution is critical to confronting the twenty-first century's microbiological challenges. We need to educate the next generation of scientists to give them the tools to develop novel treatments against antibiotic resistant bacteria, emerging viruses, and other deadly microbes. They need to understand how these microbes develop and change, which requires an understanding of evolution. Sadly, ensuring that evolution gets taught in public schools remains an uphill battle--especially since certain segments of society insist that religious doctrine, masquerading as science, be taught instead.
In the nineteenth century, the prevailing dogma was "spontaneous generation." It did nothing to prepare scientists and physicians to develop effective strategies against the infectious diseases that were killing untold numbers of people. Louis Pasteur, the French chemist who developed the rabies vaccine, was instrumental in disproving spontaneous generation and replacing it with the germ theory of disease. He helped to convince the world that invisible microbes caused disease, which led to a revolution in medicine and public health.
Changing people's minds against spontaneous generation was no small feat since it was the accepted theory at the time. The theory proposed that life could emerge from nonliving organic matter and explained why maggots suddenly emerged from rotting meat and how vermin magically appeared in stored grain. While based on observation, it was wrong. Scientists had previously identified microbes, but they were generally viewed as the result rather than the cause of disease.
Pasteur began studying spontaneous generation in 1859, around the same time he began studying fermentation. During this work, he discovered that yeasts were responsible for making wine palatable and bacteria was responsible for turning wine bad. Subsequent work on silkworms showed that microbes caused their illness and death. Pasteur saw the connection between microbes, fermentation, putrefaction, and disease. The challenge was to convince the scientific community, particularly the medical profession, to accept this novel idea. (For more on Pasteur, read Rene Dubos's book Louis Pasteur, Free Lance of Science.)
Almost simultaneously with Pasteur, Felix-Archimede Pouchet, the director of the Museum of Natural History in Rouen, claimed to the Paris Academy of Sciences that he had produced spontaneous generation. He followed this declaration with Heterogenie, a 700-page book in which he claimed to prove that life could originate from inanimate matter.
Pasteur, a devout Catholic, initially believed in spontaneous generation, but his work on fermentation convinced him otherwise. Against the advice of his colleagues, he decided to jump into the debate against Pouchet, carefully planning his experiments to disprove Pouchet's claim.
Spontaneous generation proponents believed that exposure to air was the key factor in the generation of life. Pasteur devised experiments using a novel "swan-neck" flask that would address the issue. The swan neck allowed exposure to air but trapped microbes in the elongated, S-shaped glass neck. Pasteur conducted experiments in cellars, on mountains, and even on Swiss glaciers to show that different concentrations of microbes existed depending on location and elevation.
The controversy began to take on religious overtones as the debate caught the public's attention; people took sides based on prejudiced beliefs rather than factual evidence. Pouchet and his colleagues attempted to duplicate Pasteur's results without success. Pasteur demanded that the Academy of Sciences appoint a commission to repeat the experiments; Pouchet demanded an experimental match be conducted in a laboratory in the Museum of Natural History.
An eloquent debater, Pasteur came prepared with more than 50 flasks, some of which he had previously opened on mountains and had remained sterile. He proceeded to open others throughout the museum amphitheater with many remaining sterile. The academy issued an official announcement that Pasteur had successfully disproved spontaneous generation. But despite his triumph, proponents of spontaneous generation in other countries continued to attack his findings. Time and additional research by other scientists such as the German physician Robert Koch, who proved the bacterial cause of a number of infectious diseases, eventually put spontaneous generation to rest. For the first time in history, the new "germ theory of disease" allowed people to understand the nature of epidemics and to develop effective preventive and control strategies against infectious diseases.
"Creationism," the belief that a deity created the heavens, Earth, and all its living creatures, dates back to antiquity. Indeed, many civilizations have creation stories rooted in religious beliefs. Charles Darwin's "theory of evolution" generated considerable controversy because it threatened religious doctrine. (It still does.) However, unlike spontaneous generation, which was based on observation, creationism is based on belief.
Developing a scientific theory requires collecting data, conducting experiments, and generating hypotheses to explain natural phenomena. Darwin developed his theory after collecting extensive data while on a five-year, round-the-world journey aboard the HMS Beagle; Pasteur disproved spontaneous generation because it was a scientific theory based on observation.
Proponents of creationism insist that it's a scientific theory and that evolution doesn't explain phenomenon such as the development of multi-celled animals like apes, elephants, and horses from single-celled life-forms. (See "Intelligent Design in Biology: The Current Situation and Future Prospects.") They propose that creationism is an alternative scientific theory to evolution, yet they don't provide scientific evidence for the existence of an intelligent deity. Instead, they cite gaps in evolutionary theory.
Indeed, how would someone prove by observation and experimentation the existence of a deity? Or alternatively, how would someone disprove evolution? There's extensive evidence in the fossil record, in the genetic code, and in rapidly evolving microbes. There are also experimental results of thousands of years of human genetic manipulation through selective breeding of domesticated plants and animals. For example, human genetic modification has led to dog breeds that never would have evolved naturally. Yorkshire terriers, chihuahuas, and pugs don't resemble the wolves from which they evolved. And without attentive human care, these animals wouldn't stand a chance of surviving in the wilderness.
The first public debate on creationism versus evolution took place in 1860 at the British Association for the Advancement of Science between Thomas Huxley, who supported evolution, and Bishop Samuel Wilberforce who opposed it. (See "The Evolution-Creationism Controversy: A Chronology.") The Scopes Monkey Trial was the first famous courtroom battle. (Notice none of these discussions included competing experiments or any scientific endeavors.) In 1925, Tennessee passed the Butler Act, which prohibited teaching evolution in public schools. The ACLU subsequently decided to defend any teacher who violated the Tennessee law, eventually recruiting John Scopes, a teacher at the Rhea County High School who discussed evolution with his biology class.
Judge John Raulston didn't allow expert scientific testimony during the trial. William Jennings Bryant served as the lawyer for the prosecution, and Clarence Darrow was the defense lawyer. The trial became a media circus. Ultimately, Scopes was convicted and fined $100. But in 1927, the Tennessee Supreme Court overturned the conviction. Tennessee repealed the Butler Act in 1967, but creationism proponents wouldn't let the issue rest.
In the early 1980s, Louisiana passed a creationism law prohibiting the teaching of evolution in public schools without also teaching creationism. Parents of Louisiana public schoolchildren, religious leaders, and teachers challenged the law. The case went to the U.S. Supreme Court, which ruled in 1989 that the act violated the First Amendment. Despite the ruling, in 1999, the Kansas Board of Education cut evolution from its curriculum. Meanwhile, similar challenges were occurring in other states. In 2004, the Dover Area School Board in Harrisburg, Pennsylvania, adopted a policy that required high school students to be informed of creationism. Eleven parents sued. A judge subsequently ruled (PDF) that teaching creationism was unconstitutional. While this was a victory for the separation of church and state in school science curricula, concern should remain regarding future attacks against teaching evolution in public schools. It's important to note that in the 1989 Supreme Court decision, Antonin Scalia and the late William Rehnquist dissented with the majority opinion. The Supreme Court now has a different composition, and future challenges to teaching evolution in public schools might be ruled differently.
According to a 2005 Harris Poll, a majority of U.S. citizens believe in creationism. Another survey by the Pew Forum on Religion and Public Life found that two-thirds of Americans believe that creationism should be taught alongside evolution. These results demonstrate a failure of the educational system to teach science in public schools. With No Child Left Behind focusing on test results, science is getting even less attention now. This could result in U.S. students graduating from public schools scientifically illiterate. (See "Report Says States Aim Low in Science Classes" and "The State of State Science Standards, 2005.") Today's defenders of evolution should be just as dogged and diligent as Pasteur was in preventing a backslide against scientific progress and understanding.
Similar to how germ theory of disease allows us to understand the causes of infectious disease and the spread of epidemics, evolution allows us to understand the development of antimicrobial resistance, the potential of the avian influenza virus to mutate into a human pandemic influenza virus, and the emergence of novel pathogens that can infect plants, animals, and humans. In the dark ages, people believed that divine wrath caused disease. We have come a long way since, but we need to remain vigilant that our children receive a good science education to further enhance human understanding. And a good science education includes learning about evolution.