POSTED 27 JAN 2005
Hard questions, hard answers
We hear plenty of misconceptions in the tussle over evolution, so if your school board is thinking about "balancing" the science curriculum with a dose of intelligent design, here are some reality-based responses:
Darwinian
evolution is just a theory.
Yes and no. In common use, a theory is a hunch or an idea, a possible explanation
for some observation. But the National Academy of Sciences offers this scientific definition of theory: 
"A well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and test hypotheses." Science
has many useful theories -- like Einstein's theory of relativity or the germ theory of infectious disease. These are accepted as true, because their predictions come true, but they don't have to be comprehensive or perfect. The recent discovery of mad cow disease, for example, overturned parts of germ theory, but not the core: Microbes can cause disease.
Scientifically, Darwinian evolution is indeed a theory, but it's one of the best-documented theories in science. It could be disproved, but you would need strong evidence before most biologists would question the core: Organisms change over time in response to differential survival in their environment.
If species
are continually evolving, where are the half-birds,
half-dinosaurs?
Although nobody has discovered the definitive fossil of this mid-way creature, the fossil record is littered with intermediate organisms. Whether it's the clams that Darwin studied, or the many primitive human relatives found in Africa in recent decades, the problem is making sense of the welter of intermediate organisms, not finding them.
The "misconception" over intermediate forms, says paleontologist Dale Springer of Bloomsburg University of Pennsylvania, may arise from biology's classification system, which, she notes, was "set up to put things in boxes," or species. By forcing scientists to think in terms of species, these categories became critical for understanding life. And yet the decision over which box best fits a particular organism "is often debated by the experts," Springer says. "We are creating pigeonholes that we have to stick things in, when nature itself does not do that."
The pigeonhole mentality says a bird can't be a reptile, Springer adds, and creationist
and ID arguments "rely heavily on these boundaries." And despite the scientific debate over the true relationship of birds and dinosaurs, scientists won't seek the answer in jettisoning evolution. A more useful tactic would be a smarter evolutionary analysis of a more complete fossil record.
How did angiosperms (flowering plants) split off from their closest relatives, the gymnosperms (seed-bearing plants without flowers, like pines and spruces)? DNA analysis of the water lily suggests that it is intermediate between gymnosperms and angiosperms. The big breakup occurred about 150 million years ago. Photo: Joseph Williams, NSF
It's only
fair to teach intelligent design alongside
evolution in science classes.
Not in science classes: Evolution is science, but "intelligent design," despite the claims of its advocates, is regarded as non-science by nearly all scientists. (As science historian Ronald Numbers notes, the courts will make the final decision about its inclusion in the public schools, and they haven't ruled yet on ID.)
The simplest, and strictest, definition of science, is a field of study that produces hypotheses that can be tested. If living organisms convert grape juice into wine, French microbiologist Louis Pasteur observed, and if heat kills organisms, then heating grape juice should kill the microbes and prevent fermentation. That was one proof for the germ theory of disease.
Not all sciences can be tested so easily: Evolution, like astronomy
and meteorology, relies on observation. But scientists can still test predictions
that emerge from a theory. 
Astronomers, for example, predicted the existence
of black holes decades before they were detected. Such a correct prediction
bolsters the theory.
Intelligent design, on other hand, makes no scientifically useful predictions, and returns directly to its starting point: Life is complicated.
Louis Pasteur used heat to kill decay organisms, helping to prove the germ theory of disease. His discovery, now called pasteurizing, is ubiquitous in the dairy industry. Photo: Kentucky Department of Public Health
Microbes and species may evolve, but evolution
cannot account for major changes in organisms.
No. The footprints of evolution are all over the living realm. While scientists
have not watched a new species being formed, they regularly watch evolution
on a smaller scale, as microbes evolve resistance to antibiotics,
or as fruitflies change in the lab. Plant breeders feed
the world by accelerating evolution.
All these changes start with preferential survival of the better-adapted ("more fit") organisms, and they also apply to the evolution of new species. Even many creationists now concede the truth of what they call "microevolution": The original pair of dogs on Noah's ark, they would agree, gave rise to wolves, coyotes, foxes, even miniature dachshunds.
But creationists draw the line at what they call "macroevolution," changes in the "kinds" of animals mentioned in the Bible. Yet there is massive evidence for that type of change. 
Closely related organisms have more similarities because they share more genes. Humans, apes and monkeys all have hair, backbones, four limbs, opposable thumbs, and three-jointed fingers because we all inherited similar genes from our common ancestor, which lived a few dozen million years ago.
The bones of a killer whale's flipper are eerily similar to those in your hand. Is this due to chance -- or evolution? Photo: Genny Anderson, Santa Barbara City College
The similarities fade, but don't disappear, as the evolutionary relationship becomes more distant. Whales are mammals (but not primates) that live in the sea. The bones in a whale's pectoral fin are strikingly similar to those in our hand, but whales don't have hair, and humans don't have a tail fin. Birds also have backbones, but the wing bones don't look like our hand bones, and birds lack teeth. Conclusion: Birds are more distantly related to primates; our common ancestor lived longer ago.
Evolution reuses useful genes and molecules. In Hawaiian bobtail squid, a molecule called tracheal cytotoxin spurs the development of a light-emitting organ that confuses predators. In people, tracheal cytotoxin, made by different bacteria, causes massive tissue damage in whooping cough and gonorrhea. Photo: Margaret McFall-Ngai UW-Madison
An independent proof of evolution comes from the structure of DNA and proteins. Forget about examining bones: Each living cell contains compelling evidence for evolution.
A random
process like evolution could never produce
something as complicated as an eye.
This is the heart of the intelligent design argument, but it's wrongheaded. Evolution isn't random, even though genetic mutations may happen at random. Evolution is the original game of Survivor, where some genes "outwit, outplay and outlast the others." Organisms that survive and reproduce better become more common with each generation; ditto for the genes that promote their survival. In Survivor, the reality TV show, losers -- and their genes -- get sent home. Ditto for evolution.
Evolution is not accident. Eyes probably began as simple, light-sensitive cells that helped their owner deal with the competition. In fact, eyes were so handy that they evolved several times. Evolution directs change according to one basic standard: Survival of the fittest. And that's not random.
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Darwinism doesn't explain everything.
Evolution does not yet provide a complete picture of life's changes over three billion years. Questions remain: How fast do new species evolve? What conditions favor their development? What are the exact mechanics of genetic change? What are the evolutionary consequences when genes move laterally from one species of bacteria to another?
But evolution science has progressed in the 146 years since "Origin of Species," and evolutionary understanding now encompasses mechanisms that go beyond Darwinism. "Punctuated equilibrium," to name one, is the idea that species do not change gradually, as Darwin proposed, but rather undergo bursts of creativity, followed by long eras of stability. Nonetheless, evolution through natural selection is the grounding principle of relationship and change in biology, and it's the subject of, or background to, countless thousands of scientific studies. In contrast, a mid-1990s survey of hundreds of thousands of science articles found no reference to intelligent design or creation science (see "15 Answers..." in the bibliography).
Intelligent
design is a legitimate, scientific explanation for life that deserves to be taught
in science classes.
No. As we've mentioned, ID makes no predictions. Even more damaging, however, is its appeal to an indefinable force in the form of an all powerful creator. "I'd argue that intelligent design is not scientific because it attempts to re-introduce the supernatural into science," says Numbers. While science cannot rule out intelligent design (you cannot prove a negative) there is little to disprove. ID amounts to throwing up your hands and saying that since evolution cannot explain the biological complexity, a supremely intelligent being must be responsible.
Intelligent design isn't religion.
Don't be too sure. Intelligent design grew from the same source as other evolution-free explanations for the fossil and geological records: "flood geology," sometimes called "creation science." As Numbers notes, "The first mention of intelligent design came in a 1989 book, Of Pandas and People, which was written by two opponents of evolution."
Why don't intelligent design advocates talk about the designer? Because the Supreme Court interprets the First Amendment as banning the teaching of religion in public schools. "Specifically to get into the schoolhouse door [intelligent design] abandoned any reference to the Bible," Numbers says.
Why care about the evolution devolution?
Megan Anderson, project assistant; Terry Devitt, editor; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive