New Scientist: A Sceptic’s Guide to ID
Creationism special: A sceptic’s guide to intelligent design
Source: New Scientist by subscription only
- 09 July 2005
- From New Scientist Print Edition. Subscribe and get 4 free issues.
- Bob Holmes
- James Randerson
ADVOCATES of intelligent design argue that it deserves to be taken seriously as a rigorous scientific alternative to evolution by natural selection. But just what is it, and is it science at all?
Intelligent design (ID) is more sophisticated than its predecessor, “creation science”, which sought to gather scientific evidence in support of the Christian creation story. By starting from a pre-conceived conclusion and selectively using evidence to back it up, creation science was clearly unscientific.
ID is different. Its supporters argue that we can use science to find evidence of a designer’s handiwork in nature, while claiming to be agnostic about exactly who the designer is. “Often people think the designer is the Big Guy in the Sky. But it doesn’t have to be that at all,” says William Dembski, a mathematician, philosopher and leading ID proponent affiliated with the Discovery Institute, a creationist think tank in Seattle. He describes ID as a scientific programme that leads to an understanding of a generic supernatural intelligence.
Like many creation scientists ID advocates are happy to accept a small role for natural selection, for example, in the evolution of antibiotic resistance. Unlike creation scientists, many of them are also willing to accept that all organisms came from a common ancestor. But that’s where advocates of ID and Darwinism part company.
The difference, says Michael Behe, a biochemist at Lehigh University in Bethlehem, Pennsylvania, and a leading proponent of ID, “is that Darwinism postulates random mutations and natural selection for essentially all aspects of life. ID says that at least some parts of life did not happen randomly but through purposeful design.” Nevertheless, the arguments for the inadequacy of Darwinian evolution are nearly identical to those used unsuccessfully by traditional creationists.
Their case centres on the question of how complex structures originated. Living things are full of multi-component structures that only function if all their parts are present. The bacterial flagellum, a spinning whip-like tail, for example, is made up of 40 or more proteins; blood clotting involves the coordinated interaction of 10 different proteins.
These systems are examples of what Behe calls “irreducible complexity”, meaning that they cannot function properly without all their components. Such systems, he says, could not evolve by the accumulation of chance mutations, since partial assemblies are useless.
Dembski argues that the odds against getting complex structures from chance mutations are insurmountable. For two proteins to interact to perform some new function, for example, their shapes would have to fit together. So in principle, he says, we can calculate the probability that one protein could change by chance to fit perfectly with another. Two such studies have been done. In both cases, Dembski claims the odds were so long as to rule out an explanation based on chance events.
But these calculations are logically flawed because they focus on a single, specified outcome, says Kenneth Miller, a cell biologist at Brown University in Providence, Rhode Island, a leading critic of ID. “It’s what statisticians call a retrospective fallacy.” It is like equating the odds of drawing two pairs in poker with the odds of drawing a particular two-pair hand – say a pair of red queens, a pair of black 10s and the ace of clubs. “By demanding a particular outcome, as opposed to a functional outcome, you stack the odds,” Miller says. What these calculations fail to recognise is that many different protein sequences can be functional. It is not uncommon for proteins in different species to vary by 80 to 90 per cent, yet still perform the same function.
The “improbability argument” also misrepresents natural selection. It is correct to say that a set of simultaneous mutations that form a complex protein structure is so unlikely as to be unfeasible, but that is not what Darwin advocated. His explanation is based on small accumulated changes that take place without a final goal. Each step must be advantageous in its own right, although biologists may not yet understand the reason behind all of them.
There is also evidence that “irreducible complexity” is an illusion. Take, for example, the bacterial flagellum with its 40 proteins. One species, the stomach bacterium Helicobacter pylori, has a flagellum with just 33 proteins – “irreducibility” reduced. More tellingly, a subset of flagellar proteins turns out to serve an entirely different function, forming a mechanism called the type III secretory system, which pathogenic bacteria use to inject toxins into their host’s cells. Similarly, jawless fish accomplish blood clotting with just six proteins instead of the full 10.
So while it is true that no biologist has worked out the precise series of events that resulted in a flagellum, that in itself is not a refutation of natural selection, says Miller. It has long been argued that natural selection works by adapting pre-existing systems for new roles. The evidence so far points to exactly this process for the flagellum.
Crucially, ID does not make testable predictions. Its prediction that we should find evidence of a designer is actually nothing of the kind, say scientists: rather, it is a catch-all that takes up anything that natural selection cannot – so far, at least – explain. Dembski admits as much in his 2004 book The Design Revolution: “To require of ID that it predict specific novel instances of design in nature is to put design in the same boat as natural laws, locating their explanatory power in an extrapolation from past experience.”
Though almost all ID advocates are professed Christians, they avoid spelling out exactly what kind of designer they have in mind. “The reason is they think the designer is God, and if they mention God then the jig is up,” says Nick Matzke, a spokesman for the National Center for Science Education (NCSE), a pro-evolution organisation based in Oakland, California. This helps ID’s supporters argue that it is not subject to the ban on teaching creationism in science classes, he says. But being vague about how the designer is supposed to operate also makes ID impossible to test.
And this is the nub of it. A scientific theory must be falsifiable in principle; it must be possible to imagine evidence that would knock it down. This is not the case for ID. So even if proponents of ID were persuaded that, say, the bacterial flagellum was indeed the product of natural selection, that would not send them packing. ID says that we should be able to find evidence of design in nature, not that every structure has been designed. So ID proponents could simply concede that natural selection operated there, and then shift their ground to another molecular structure.
ID’s appeal to supernatural forces by definition puts it outside the scope of science, says Eugenie Scott head of the NCSE. After all, saying “God did it” can never be disproved.
And that’s the point. Underlying the ID agenda is a challenge to the basis of scientific method. The infamous Wedge Strategy, written in 1999 by fellows at the Discovery Institute, bemoans the “devastating” cultural consequences of scientific materialism. It also details a 20-year plan to defeat it “and its destructive moral, cultural and political legacies”. The strategy aims “to replace materialistic explanations with the theistic understanding that nature and human beings are created by God”.
In response to the controversy that followed the document’s release on the internet, the Discovery Institute says the Wedge Strategy is merely a “fund-raising document”, and should not be portrayed as some kind of sinister master plan. “We are challenging the philosophy of scientific materialism, not science itself,” it states. But far from just redefining science, most scientists would argue that introducing the supernatural will destroy it.
