Even before Darwin, critics attacked the idea of biological evolution with one or another version of, "Evolve this!"
Whether they invoked a human, an eye, or the whip-like flagella that propel bacteria and sperm, the contention that natural processes of mutation and natural selection cannot explain the complexity of living things has been alive and well for 200 years.
Biologists used to just roll their eyes (and sometimes descend to name-calling) at all this. More recently, they've been joining with First Amendment groups to oppose moves to water down the teaching of evolution in classrooms.
But now they are firing back with science. Their target: a line of attack that has promised over the past decade to "smash through the overwhelming weight of scientific evidence to bring Darwin to the canvas once and for all," as cell biologist Kenneth Miller of Brown University, Providence, R.I., puts it.
The latest flaps are over Georgia's proposal (withdrawn last week) to eliminate the word "evolution" from science classes, and a Missouri bill requiring that biology curricula include a creationism off-shoot called "intelligent design."
This new antievolution argument evolved (no irony intended) from the belief that living things are so complex they only could have been designed by an intelligent being.
For years, intelligent-design theory had been bogged down in what one wag calls "the argument from personal incredulity" ("I can't see how natural forces could produce this, so it must be the work of God"). Darwin's new foes, however, are smart enough to realize that just because most of us can't imagine how the sun can burn so hot for so long, it doesn't follow that God, not nuclear fusion, keeps the fires stoked.
In 1996, biochemist Michael Behe of Lehigh University, Bethlehem, Pa., therefore offered a stronger argument against evolution. Complex living structures, he argued in his book "Darwin's Black Box," possess "irreducible complexity." That is, they can't function until all their components are assembled, much as a mousetrap isn't much good until the base, spring, bar and all the rest are connected.
Moreover, the individual parts of complex structures supposedly serve no function. Because evolution selects only the fittest innovations, useless ones vanish. The odds against a bunch of useless parts lying around at the same time and coming together by chance are astronomical, mathematician and evolution-critic William Dembski of Baylor University correctly notes.
But a funny thing happened when biologists started scrutinizing structures said to be irreducibly complex. Take the flagellum. It turns out that its base -- which Darwin's foes assert has no stand-alone function -- is made of the same necklace of proteins that compose a kind of syringe used by primitive microbes.
Called the type III secretory system, this microsyringe enables a bacterium to inject a toxin into its victim (this is how bubonic-plague bacteria kill). This component of the flagellum, then, could have been hanging around a very long time, conferring benefits on any organism that had it, ready to combine with other structures (which also perform functions in primitive living things) into a full-blown, functional flagellum.
"As an icon of antievolution, the flagellum has fallen," says Prof. Miller, a practicing Catholic. "If bits and pieces of a machine are useful for different functions, it means that natural selection could indeed produce elements of a biochemical machine for different purposes."
It's like discovering the mousetrap bar was a fine toothpick long before it got together with the other parts to kill rodents.
Components of other irreducibly complex structures and systems, it turns out, have functions, too. Humans, for instance, have a complex multipart biomachine that plays a key role in how cells produce energy.
Irreducibly complex? Maybe not. Two of the six proteins that make up the proton pump that produces energy are dead ringers for those in ancient bacteria. Evolution could have co-opted them when it was putting together the more complicated biochemical processes inside animals, including people.
Biologists have pinpointed the origins of only a few of the complex structures in humans and other higher organisms. Even in these cases, Prof. Behe argues, they have not explained, step by step, how simple systems could evolve into complex ones. But with discoveries like the microsyringe, Darwinians have cast serious doubt on the claim that it is impossible for evolution to shape any complex system.
In one of those strange-bedfellows moments, theologians are joining biologists in criticizing intelligent design. Biologist and Anglican priest Arthur Peacocke, for instance, argues that evolution is God's way of creating. George Coyne -- astronomer, Jesuit and director of the Vatican Observatory -- goes further. Invoking God to explain what we can't otherwise account for, he says, is "a kind of idolatry," because true faith should come from within and not because we can't fully explain the natural world.
The evolution wars show no sign of ending, but maybe they are starting to generate a little light as well as much heat.
File Date: 2.13.04
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