Jeff Dukes was driving his lab's huge SUV through the red hills of southern Utah when he asked his wife a question that seemed simple at the time, but led to an astonishing answer.
"We're burning a lot of gas," noted Dukes, then a postdoctoral researcher in ecology at the University of Utah. "Where does all that gas come from?" he asked his wife, also an ecologist.
Months later, after extensive research, Dukes has found his answer. And it casts a new light on the precarious hole that modern humans have dug for themselves.
It turns out that it took tons and tons of tiny plants and animals, buried at the bottom of the seas, lakes or river deltas, to produce every gallon of gasoline that poured through the big engine of that SUV.
It took 98 tons, to be exact, or 196,000 pounds. For every gallon.
Lot of Dead Matter
"That's a shocking number," says Dukes, who is now en route to a new post at the University of Massachusetts in Boston.
And of course nobody burns just one gallon of gasoline. That probably barely got the engine started in Dukes' SUV. We burn millions of gallons every day, and we rely on fossil fuel for a wide range of other energy needs. So how much prehistoric plant and animal material do we need to get through a single year?
Dukes zeroed in on the year 1997, and relying on reports from various agencies, including the United Nations, he came up with statistics that are really astonishing.
He found that the total amount of fossil fuel burned that year amounted to 97 million billion pounds of carbon. That's equivalent to more than 400 times the plant material produced by the entire world during a single year.
So every day, the amount of prehistoric biological material needed to produce the fossil fuels that we burn that day is more than the entire world's production over an entire year.
At that rate, it would seem that we should have run out a long time ago, but "fortunately for us, there were huge reserves to begin with,'' Dukes says, thus paving the way for the Industrial Revolution and ultimately, his university's SUV. But his research shows in more graphic terms than most that there are limits to this finite source, and time may well be running out.
The End Matter
Dukes is not your basic alarmist. He didn't set out to scare the daylights out of us. He just wanted to answer a simple question that very few others have tried to answer.
"I decided to try to find out just what goes into a gallon of gas," says Dukes, who first thought that would be a simple task. "I figured I could just do a Web search and find out. That didn't work."
But as a trained scientist with access to all sorts of research, he figured he would just have to dig a little deeper to find a professional paper that answered his basic question.
"I have access to all kinds of great information and searching tools, and I still couldn't find a paper with the answer," he says. "Not even a ballpark estimate."
But he kept digging and soon found himself surrounded by bits and pieces of information. Scientists from various disciplines had looked at different parts of the issue, determining for example how much organic material is lost at each step of the multimillion-year process that turns green organisms into fossil fuel.
There are losses all along the way as the organic material is trapped in a geological formation where it will remain for millions of years while it decays into fossil fuels. The amount of loss at each step in the process is known fairly well because of the extensive research needed to find and develop fuel deposits.
By adding up all the factors, Dukes determined how much organic material was required to produce the oil, coal and gas deposits that are available to us today. Or perhaps more to the point, how much of what was originally there was lost due to erosion or other natural forces and never joined the fossil fuel pool.
And that led to another astonishing figure.
Only one-eleventh of the carbon in plants deposited in peat bogs ends up as coal, according to his calculations. But that's amazingly efficient compared to the process that turns biological material that was deposited in ancient marine environments into oil and natural gas.
And here's the shocker. Only one atom out of every 10,750 carbon atoms ended up as oil or natural gas. The rest washed off, blew away, or was somehow returned to the earth's carbon bank.
It's amazing that the process worked at all because only a tiny percentage of organic material "grew in a place where it could eventually become stored and turned into a fossil fuel that we could reach today," Dukes says.
"And so you would think that we would have run out a long time ago, but fortunately there were millions and millions of years during which this fossil fuel was accumulating in all its various forms."
Nowadays, "we are clearly running through it quite fast," he says. That's why he titled a report on his research, published in the November issue of the journal Climatic Change, "Burning Buried Sunshine: Human Consumption of Ancient Solar Energy."
Many experts believe the world's production of fossil fuels has already peaked. After this, if they are right, it's all downhill.
It will take a while to get there, of course. But along the way the world's political power will shift increasingly toward countries that have it, and away from countries that have already spent it.
The societies that survive will be those that figured out other ways to produce the fuel they needed to power their homes, factories, and transportation devices. It's hard not to wonder why that isn't the No. 1 priority in the world today.
Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.