When I first arrived at the Ronald Reagan Federal Building and Courthouse in Harrisburg, Pa., for what was billed as the second coming of the Scopes “monkey trial,” a man mingling with the media gaggle handed me an invitation to a lecture titled “Why Evolution Is Stupid.” The fellow advised me to come hear the truth about Charles Darwin’s dangerous idea. Then he jerked a thumb toward the courtroom and said, “You’re sure not going to hear it in there.”

I had gone to Harrisburg just more than a year ago to research a book, expecting cutting-edge arguments for the theory of evolution pitted against an upstart movement called “intelligent design,” which claims there is evidence of a master designer inside living cells. And hear them I did, in frequently riveting (and occasionally stupefying) detail, as the judge considered whether teaching intelligent design in public schools breached the wall separating church and state.

And yet that invitation and the angry, volatile town meeting it led me to that week proved even more enlightening. It showed me an essential truth of the culture wars in the United States: There are really two theories of evolution. There is the genuine scientific theory, and there is the talk-radio pretend version, designed not to enlighten but to deceive and enrage.

The talk-radio version had a packed town hall up in arms at the “Why Evolution Is Stupid” lecture. In this version of the theory, scientists supposedly believe that all life is accidental, a random crash of molecules that magically produced flowers, horses and humans – a scenario as unlikely as a tornado in a junkyard assembling a 747. Humans come from monkeys in this theory, just popping into existence one day. The evidence against Darwin is overwhelming, the purveyors of talk-radio evolution rail, yet scientists embrace his ideas because they want to promote atheism.

These are just a few highlights of the awful and pervasive straw-man image of evolution that pundits harp about in books and editorials and, yes, on talk radio, and this cartoon version really is stupid. No wonder most Americans reject evolution in poll after poll.

But then there is the real theory of evolution, the one that was on display in that Harrisburg courtroom, for which there is overwhelming evidence in labs, fossils, computer simulations and DNA studies. Most Americans have not heard of it. Teachers give it short shrift in schools because the subject upsets too many parents who only know the talk-radio version. But real evolution isn’t random; it doesn’t say man came from monkeys. Those claims are made up by critics to get people riled up – paving the way for pleasing alternatives such as intelligent design.

Real evolutionary theory explains how life forms change across generations by passing on helpful traits to their offspring, a process that, after millions of years, gradually transforms one species into another. This does not happen randomly but through nature’s tendency to reward the most successful organisms and kill the rest. This is why germs grow resistant to antibiotics and why some turtles are sea animals and others survive quite nicely in the desert, and why dinosaurs – and more than 99 percent of all other species that have ever lived on Earth – are extinct.

The environment changes. The recipe for survival changes with it. And life changes to keep up – or it dies. Darwin’s signature insight is both brilliant and elegantly, brutally simple.

The real theory of evolution does not try to explain how life originated – that remains a mystery. The truth is that many scientists accept evolution and believe in God – and in a natural world so complete that it strives toward perfection all on its own, without need of a supernatural designer to keep it going.

The judge in Pennsylvania eventually found that real evolution was not stupid; that intelligent design was religion, not science, and that the school board in Dover, Pa., whose actions had precipitated this replay of Scopes, was out of line. Judge John E. Jones III was rewarded for his sensible and well-documented ruling with death threats. Such is the power of talk-radio evolution.

Judge Jones has since told me that his only regret in the case is that he did not bend the rules to allow live TV coverage so more people could see the powerful evidence supporting his decision. Because the one thing the prophets of talk-radio evolution have, it seems, is the loudest megaphone.