Intelligent design's doubt: Is evolution the full story?
August 14, 2005
The question posed by intelligent design is not whether evolution is true, but how much it can explain.
Michael Behe, one of the idea's main proponents, is a biologist and accepts that humans are part of an evolutionary tree that dates back billions of years and includes everything from apes to mold. But he has argued, beginning with his 1996 book Darwin's Black Box, that evolution cannot explain all the complexity of life.
Darwinian evolution works by variation and natural selection. DNA encodes the information that serves as the blueprint for an animal. Occasionally there are mutations in this DNA, and sexual reproduction brings the characteristics of parents together in new combinations. From this variation, the individuals that are best suited to their environment prosper and pass their characteristics to their offspring. Over millions of years, small advantages accumulate into dramatic changes -- examples of which fill the scientific literature. For example, there is a detailed fossil record of horses, and they adapted to shifting environments over 55 million years.
Behe, however, argues that Darwinian evolution cannot explain what he terms ''irreducible complexity." There are many systems in the cell that contain multiple parts, but that don't work if any of the parts is removed.
Such systems, he argues, are unlikely to come about through evolution because the pieces would have to appear all at once to give the creature a selective advantage.
Behe cites as one example the flagellum, an elaborate structure that works like a biological motor and that helps some organisms move. Behe uses the analogy of a mousetrap, with a base, a spring, and a hammer. None of the pieces would evolve alone, because they are useless alone. It is thus very hard to imagine how a mousetrap could have evolved through small changes, each of which had conferred some advantage. A mousetrap is thus ''irreducibly complex."
Almost all biologists dismiss intelligent design. Many of its supporters, scientists argue, are using intelligent design to promote a political and religious agenda: undermining the teaching of evolution, despite the overwhelming evidence that supports it.
Intelligent design also does not say what the designer is, making it difficult to test the idea.
Critics of intelligent design say that evolution can produce the kinds of systems that Behe calls irreducibly complex. To use the mousetrap analogy, the spring, hammer, and platform may have each evolved on their own to perform some other, different, function and then been brought together to perform a new one -- catching mice. There is evidence, for example, that parts of the flagellum evolved for other purposes.
Behe said such alternative explanations for irreducible complexity, based in evolutionary theory, are possible. But he has said that nobody has proven, to his satisfaction, that this has ever happened.
Many people misunderstand what intelligent design and evolution have to say about religion. Neither proves or disproves the existence of God.
Even if it were accepted that evolution had been assisted by some designer, intelligent design cannot say who or what the designer is. And for all that Darwin's theory of evolution can explain, it does not explain how the universe began, or describe forces that act outside the material realm that is the domain of science.
GARETH COOK
© Copyright 2005 Globe Newspaper Company.
