Why intelligent design is weird science

Francisco J. Ayala, a professor of evolutionary biology and philosophy at the University of California-Irvine, is both an expert in the field of evolution and its ardent defender.

From serving as an expert witness in court battles over the teaching of evolution in public schools to writing a letter defending evolution to Pope Benedict XVI just last year, Ayala has been a tireless advocate of what he calls the "fact" of evolution, arguing strongly against the theory of intelligent design, whose advocates claim that evolution leaves no room for God.

But evolution and religion need not be adversaries, says Ayala. "Science can neither endorse nor reject religious beliefs," he writes in his book Darwin and Intelligent Design (Fortress), arguing that "we may accept [evolution] without denying the existence of God or God's presence in the universe." Ayala, winner of a 2001 National Medal of Science, has his work cut out for him: A June USA Today/Gallup survey of 1,003 adults found that two thirds of those polled believe that humans were created by God about 10,000 years ago, while only 52 percent say that humans evolved over millions of years.

When scientists talk about the theory of evolution, what do they mean?
Evolution is the history of living things, the origin and development of life. We used to study it by means of morphology, paleontology, and fossils, but now we also use DNA because it has much more information. With DNA we can now ascertain the evolutionary history of an organism. We can now trace the history of living organisms all the way back to a single universal common ancestor.

Evolutionary theory also includes the mechanisms by which evolution operates. The key process is natural selection, which accounts for adaptation. Natural selection is one of the greatest discoveries in the history of science. It is the process that explains why we have eyes for seeing, hands for grasping, legs for walking.

The evidence for evolution is so strong that we often speak of it as the "fact" of evolution. It is no longer an issue that occupies scientists nowadays, because the fact that evolution has occurred and accounts for the history of organisms is certain, just as science is certain that the Earth revolves around the sun.

When scientists refer to evolution as a theory, does that mean it might not be true?
Theory in science does not mean unsupported opinion but rather a well-established body of knowledge, which includes concepts and explanations that have been tested by scientific method. When scientists refer to what is called a theory in common language, they call it a hypothesis, an assumption or guess that has yet to be fully tested. But the word theory is never used in science to suggest something like a hunch.

How can scientists be so certain about the "fact" of evolution?
As you may have read in the papers or seen on television, we can use DNA to find out the identity of the father of Anna Nicole Smith's daughter. Most people know about convicted prisoners whom DNA has proved innocent.

By looking at DNA we can also reconstruct the history of evolution because DNA carries all the genetic information of living organisms. DNA changes gradually over time through mutations, which are fairly rare. Natural selection determines which of those mutations are beneficial and become established, and which ones are eliminated.

DNA has an enormous amount of information. We inherit 3 billion nucleotides (bits of DNA each signified by one letter) from each one of our parents, what we call one genome. The letters that make up one human genome alone would fill about a thousand volumes the size of a Bible. So there's a lot of information to compare organisms with each other, which allows us to reconstruct their evolutionary history. We can keep studying more DNA until we get greater and greater precision. That is, by comparing the DNA of species we find out how species are related. For example, we now know that chimpanzees are more closely related to humans than chimpanzees are related to gorillas or orangutans. We know that just by looking at the number of differences in the DNA for each of the species.

How is the theory of intelligent design different from evolution?
Proponents of intelligent design say that organisms are so complicated, so complex, that, first, they give evidence of having been designed by an "intelligent designer," a sort of engineer, and, second, they could not have come about by chance.

Now the first part about the engineer is wrong; the second part is actually right. Organisms could not have come about by chance. The components that make up an eye could not have been put together by chance.

Natural selection is not chance. It's a process that selects what is useful to the organism and thus preserves the changes that "make sense" for its survival.

Where does intelligent design come from?
The argument "from design" was the fifth way that Thomas Aquinas used as proof for the existence of God: that there is clearly purpose and direction, a harmonious design all through the universe, that reflects a knowledge and intelligence, which we call God. The argument was developed by the Greeks well before the Christian era. And it was certainly used by some in the early church.

In the context of biology, the argument was articulated by William Paley, a distinguished theologian and clergyman in the second part of the 18th century in England. In an important book called Natural Theology, he develops the argument in great detail. The argument has two parts: first, there is design in nature; and second, only God could have been the designer.

Paley looks at the eye for example, pointing out that it has the only black tissue in the body, the retina, which is placed in the exact position where rays of light can converge and an image can be formed. Paley sees the whole series of precise relationships between the parts of the eye as proof of design.

He goes on to look at all the organs, at the differentiation between the sexes, and so on, giving evidence that everything is designed very precisely.

Paley does admit in one chapter that there are defects in the design of organisms. He says that even if we find defects and imperfections, we should ignore them because of the abundance of perfection and design. But if God has to account for everything, you cannot get away by just saying that the defects are insignificant. Paley was at least honest enough to bring up the point.

How did intelligent design work its way into our public debate?
In terms of recent history, in 1967 the U.S. Supreme Court declared unconstitutional laws that prohibited the teaching of evolution in public schools, at which point something called "creation science" was invented. Some laws then demanded that biology teachers give equal time to creation science and evolutionary theory, even though the six principles of creation science were taken out of Genesis. If teachers didn't want to teach creation science, then by law they could not teach the theory of evolution either. In 1986 the Supreme Court said that creation science is not science but religion, and therefore could not be taught in the schools.

So in the 1990s some began reviving Paley's arguments as "intelligent design," which in terms of modern biology really does not make any sense. There is only one biologist, a professor at Lehigh University named Michael Behe, who has tried to develop this argument by pointing out complex designs like the flagellum of some bacteria, which allows them to swim, or the blood-clotting mechanism in mammals.

But even Behe himself points out that the clotting mechanism is so unnecessarily complicated that it could have been designed better by a human. God is evidently so clumsy that he created something complicated to accomplish something simple.

That's the way evolution works many times, but not God. A human engineer would have done better.

How does Behe account for the inefficiency?
Behe admits that organisms evolve but argues that from time to time God has to intervene to create the parts that are too complex. So God has to fix something from time to time to perfect it. But there is no scientific validity to that.

In science we articulate a hypothesis and develop experiments to test it. How can you test intelligent design? There is nothing that can be tested. There are no experiments, no scientific explanations; nothing has been done to support this theory. Its proponents just assume that the complexity of evolution cannot be explained by natural processes.