Reading the newspapers lately, you might get the impression that the once strident climate-change deniers, doubters and skeptics are slowly becoming extinct. The New York Times recently called Sen. James Inhofe, the most strident of Al Gore's critics, "a dinosaur," and few in the House or Senate even tried to counter Gore's recent testimony on Capitol Hill. Meanwhile, the scientific consensus, as reflected in the latest report by the Intergovernmental Panel on Climate Change, appears to be bulletproof.

Yet, far from fading away, climate-change skeptics seem to be coming in the windows, as prevalent as flu virus in winter. I know I'm accosted by doubters on a daily basis, from the parents of friends at a cocktail party, to the counter patron at a local BBQ joint, to an acquaintance in the ice cream aisle at the supermarket. Last week the “Vox Populi” column in a regional paper asked, "Is global warming a problem?" And more than one response was, "You'd have to believe in it first."

All this begs the question: Why? At some point, doesn't a scientific consensus become accepted fact, like the roundness of the earth, the germ theory of disease, gravity, or Americans landing on the moon? If it doesn't, why not?

One of my favorite explanations comes from a psychologist who was interviewed about the Heaven's Gate Cult. In response to the Hale-Bopp comet, members of this group dressed in black sweat suits and overdosed on phenobarbitol and vodka, each carrying five dollars in quarters for the vending machines on the spaceship that would take them away. The psychologist said: "There are 6 billion people on the planet. At any given time, a lot of people are going to be doing some weird stuff." Which means, I guess, that a lot of people will believe whatever they want to believe, regardless of science, fact or reality.

As with the Heaven's Gate cult, there's a familiar human element to climate-change deniers. Some people just seem hard-wired that way. One of the most famous skeptics about global climate change is Richard Lindzen, a professor of meteorology at MIT, who has also questioned the link between smoking and cancer. He's a contrarian by personality and probably reminds us all of a lovably irascible friend. But why are some people wired like Lindzen? Is it a vagary of personality, or might there be a broader purpose that skeptics play in the world?

One answer comes, ironically, from another still-debated "theory" --evolution. Anthony Westerling, an engineering professor at the University of California, Merced, recently mused that there might be a Darwinian advantage to having skeptics -- even irrational skeptics -- in society. Skeptics could confer some level of check and balance and thereby increase group survival over time. This argument might have made more sense in the past when our grasp of science was weak. It was useful, for example, for society to question the idea that malaria came from bad air in swamps.

Today, though, doubters of global warming aren't serving an evolutionary role; they're threatening group survival. We can think of the skeptic role as an evolutionary vestige that was useful once but harmful now, in the same way that Attention Deficit Disorder might have kept cavemen primed for sneak attacks, but now only makes for distracted cubicle-dwellers.

The problem with the prevalence of climate-change doubters is that we don't have time to humor them. Scientists say we need to substantially clean up the planet's dirty energy infrastructure within 10 years to prevent catastrophic consequences. Yet the persistence of the deniers suggests there is a fatal obstacle to attacking this problem in a timely way.

It must be that reversing climate change really requires a social, not a scientific, evolution. Even though the science behind the earth orbiting the sun has been solid for some time now, Galileo wasn't formally exonerated by the church until 1992, some 350 years after his conviction for daring to say that the sun was the center of our solar system. Similarly, the battle for civil rights, which started over 200 years ago, required the bloodiest war in American history, the heroics of Martin Luther King Jr. and Rosa Parks, and it still isn't over.

The terrifying slowness of social evolution tells us that our challenge is even greater than we thought.

Auden Schendler is a contributor to Writers on the Range, a service of High Country News in Paonia, Colorado (hcn.org). He directs environmental affairs for the Aspen Ski Co. in Colorado.