Karen Garloch / The Charlotte Observer

Seventy percent of U.S. adults are overweight or obese. And today’s children are the first generation of Americans expected to age more quickly and die younger than their parents.

But how much do we know about how we got here?

Scott Gordon, of University of North Carolina, Charlotte, harked back to the Stone Age when describing the journey in his recent lecture, “Fitting Into Your Genes: The New Paradigm for Healthy Aging.”

Back in that hunter-gatherer period, people might have walked miles to find their next meal.

“Our ancestors were pre-programmed to expect and respond to physical activity,” said Gordon, chairman of UNC Charlotte’s kinesiology department.

Those who survived were the ones who could go for days without eating and then, after gorging on a feast, store extra calories for the hard times ahead. They had what Gordon called “thrifty genes.”

“The human genome hasn’t changed for 10,000 years,” he said.

But our habits have.

During the agricultural revolution, people were able to eat more regularly, so they didn’t need those “thrifty genes.” But they were active enough, toiling in the fields, to work off the calories and keep from gaining excess weight.

“Today, technology has us sitting in front of (computer) screens most of the day,” Gordon said. “But we still have this ancestral genetic program that expects physical activity.”

We still have our “thrifty genes,” and we still have the inclination to enjoy a feast, but we’re not burning enough calories.

Gordon encouraged people to exercise and eat more healthy foods to stem the effects of aging.

“Exercise is medicine. It’s truly a magic bullet for dozens of disorders,” from heart disease to diabetes, he said.