I’ve been puzzled by people I know to be intelligent who nonetheless find it inconceivable that the earth’s climate could be affected by human activity. Then I saw one of those “cavedude” commercials on television, and a glimmer of insight began to flicker.

In the commercial, a Neandertal in modern dress is talking to a psychiatrist, trying to work through his resentment at the claim that something is “so easy, even a caveman could do it.” The commercial apparently struck a chord with viewers, or at least with the hominids trying to come up with new ways to entertain us: The concept of a button-down caveguy with feelings will now emerge as a sit-com.

This is timely, because it’s something we need to keep in mind about ourselves as we try to face the 21st century: We all still have the brain of a caveman. But as the caveguy in the commercial tries to say: “This is not an insult.”

The human brain evolved over the past two or three million years, a time when proto-humans wandered over the earth in small groups of 30-100 people. Only in the last 1 percent or less of that time -- the 20,000 or 30,000 years since post-glacial population pressures forced us into farming and, ultimately, city-living -- have we had to grapple with the consequences of our growing success as a species. And only in the last 1 percent of that 1 percent of our natural history -- 200-300 years -- have we been faced with the possibility that, as a swarming species, we could make the planet thoroughly unlivable. But physical evolution doesn’t happen that fast, and we confront this possibility with basically the same brain we were working with in those hard but fundamentally irresponsible eons of hunting and gathering the earth’s low-hanging fruit.

In its time and place, our brain was probably a better brain than it is today. Here in Colorado’s Upper Gunnison valley, if we sophisticated modern humans were suddenly to be transported back 10,000 years, minus our technology, and faced with the challenges of surviving on what we could scrounge out of the valley environment, we would all be really glad if the Folsom people, who successfully lived here then, deigned to lend us a hand. To survive year-round in this valley, the way they did, those paleo-humans had to have possessed mental and psychological resources that have probably gone dormant in humans raised in a cocoon of technological convenience and abundance.

But reactions to the climate-change issue show at least one way in which we are operating with the same basic brain. A natural response to living in small groups in the vast, indifferent, randomly beautiful and cruel Pleistocene world, populated with mammals larger, stronger and quicker than we were, would be a kind of inferiority complex that is still evident in our hard-wiring today. Think what we still say when we confront a beautiful mountain or terrible storm: “It makes me feel so small and insignificant!” Or, to cite a recent full-page four-color tourism ad that ran in the Denver Post: “For generations, finding yourself has come right after discovering your insignificance.”

The idea that little-old-us could ever become so large in the world that we could change the earth, or even lay waste to huge portions of it, was unthinkable to the nomadic humans that represent all of our natural history as a species -- except for this most recent 1 percent of 1 percent of our existence. And if we don’t consciously stop and think seriously about the thousand-fold difference between a few million humans and 6.5 billion of us armed with technology that is literally recreating on earth the carbon-heavy environment of the steamy Pennsylvanian period, then the concept of human-induced climate change could remain unthinkable for us today.

But paradoxically, for that caveman brain we still operate on, a grudging willingness to accept the knowledge that we could precipitate – and probably already have -- huge changes in the planet, can lead right into another problem. We could move straight from denial to despair: How can little-old-us possibly do anything to repair our monumental changes – starting now?

Those dormant mental and psychological capabilities of the caveman brain, which enabled hominids to go from a handful of comparatively weak and vulnerable primates scurrying around Africa to the dominant mammal species adapted to every place on earth, could address that question with vigor. But not so long as our caveman’s inferiority complex gets in the way.

George Sibley is a contributor to Writers on the Range, a service of High Country News (hcn.org). He’s writes about energy and water in Gunnison, Colorado.