Sarah Tuff Dunn

Every Tuesday and Thursday at 9 a.m. at a community center in Palo Alto, Calif., Debby Fife, who’s in her late-70s, gets down with an eclectic cadre of fellow fitness seekers. The beats are up-tempo and funky. The moves are dynamic and fun. Sometimes the class throws jabs and crosses; other times the group gyrates to a salsa beat. Ballet and old-school calisthenics show up as well. Pulses pound, muscles flex, sweat flies, and a joyous, can-do spirit prevails — even among students over 90.

Our ancestors heard it: A constant, echoing drumbeat of threat, sounding a daily reminder to run for their lives. They were wired to leap, climb, and swim to survive. Evolution took its course, and hunters and gatherers transformed into farmers; eventually, many became operators of tools and machines. With the advent of 20th century technology, activity as a necessity almost completely faded away, especially in certain parts of the world. Though we’re meant to move, many of us became sedentary.

Walking is directly linked to increased longevity, and it’s a common method of exercise for the longest-living people. “If you look at the longevity of people who consistently incorporate walking into their routines, even without strength training, it’s a lot better than those who don’t walk,” says Jason Stella, NASM, PES, CES, Life Time national education manager.