Scientists gathered at a Sept. 25 conference took up an age-old challenge laid down by Charles Darwin.

“If it could be demonstrated,” Darwin wrote, “that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.”

“What about light sensitive surfaces like the retina,” said Michael Behe, a professor of biological sciences at Lehigh University said. “If you focus on a complex system like the retina at the molecular level, you see that one of its components is itself made up of a larger number of parts, all of which are interdependent. If someone was born without one of these components, he'd be blind. The chemistry of vision is extremely complex and Darwin didn't have the tools to explain it, so he left the question of it wide open, as a black box that you can't investigate,” Behe told the Register.

In the language of evolution, vision is what is called an “irreducibly complex system.” Behe says there are many others: biological systems that work as a whole, but are useless without every one of their minute parts.

The question Behe asks is “How could a system that lacked a necessary component in one generation ever come to acquire it in a subsequent one?”

“It was easy to assume that evolution could produce biochemical systems like light sensitive surfaces or blood clotting systems when we didn't know how they worked. But now that we see the details, Darwinian evolution is a less plausible explanation than it once was,” Behe said.

For Behe, a more plausible account of complex biological systems would allow for the possibility that they were designed by a complex intelligence. But most scientists, he said, are just too too fearful of the “G” word to even consider appealing to intelligent design as an alternative to Darwinian evolution.

Give Up and Say ‘God Did It’

Critics of Behe say he underestimates the ability of evolutionary theorists to explain irreducibly complex systems. And critics of Dembski say he would have us return to a mingling of the science and revelation that puts limits on the Christian God.

“It's true that we don't understand a lot about evolution,” but that doesn't mean we should give up and say ‘God did it,’” said Jerry Coyne, a professor in the department of ecology and evolution at the University of Chicago. “Behe's major fallacy is that he hasn't demonstrated that these systems are irreducibly complex. For all these systems, he does-n't know what would happen if you removed a part. To conclude that a system would break down is simply conjecture,” Coyne said, adding that, in his view, evolution may gives systems that aren't irreducibly complex the appearance of being so.

Coyne, who said he was not himself “a religious person,” told the Register that the reason we can't explain certain biological systems is that we don't have a fossil record of their history. “What Behe says is that every time we run into a complex problem we should give up and say that God did it. We are not excluding God; we just don't see how he helps us to understand scientific questions like this one. This is a practical matter.” Coyne added.

“I'm very careful to talk about intelligent design and not God,” Behe said, responding to Coyne's criticisms. “Science studies physical systems and one can come to the conclusion that an intelligent designer ordered these complex system based on observing them closely.

“Scientists are now searching for extra-terrestrial intelligence based on radio signals they receive from space. They believe they will be able to determine the presence of intelligent life forms based on the complexity of the waves they receive. They are confident that they can detect the presence of intelligent life forms based solely on the structure of radio systems, on the complexity of the waves they receive. I'm saying the same thing for biochemical systems.”

In response to Coyne's claim that Behe uses God to fill in the blanks, Behe said, “the conclusion for intelligent design is not based on ignorance of what a system looks like, but on our knowledge of how systems interact with each other.”