Take a look at Fido: lying on your kitchen floor, fat and arthritic. Then take a look at dogs in the wild: lean, muscular, with healthy teeth, bones and joints. That, basically, is the problem.

Like your faithful companion’s, your body evolved to live, work and eat in the wild. For over 100,000 generations, your ancestors lived as hunters and gatherers. Then, only about 500 generations back, they domesticated themselves, completely changing the way they went about life. Problem is, in evolutionary time, 500 generations is chump change. Your genes are almost identical to your ancestors’ from tens of centuries back. Somewhere along the line, how you use and feed your body, and how your body evolved to be used and fed, got horribly out of whack.

“So what?” I hear you say. Well, for a moment, let’s take a look at the fossil record those way-back Paleolithic ancestors left behind. As Hobbes wrote, lives that were “poor, nasty, brutish and short,” right? Well, no. Certainly, the average life span was shorter. But almost entirely because, research shows, of infectious disease and other now easily curable problems, especially among infants and children. Those Paleo hunter/gatherers who did make it through the perils of childhood (and past the ever-present danger of ending up as a sabre-toothed tiger snack) were remarkably healthy. Many lived surprisingly long lives, and virtually all of them were free from heart disease, cancer and stroke, today’s three leading killers.

Medical records gathered at the turn of the century from the few remaining hunter/gatherer tribes show the same thing: lean, physically fit people almost entirely free from the chronic diseases that plague the civilized world. Interestingly, in every one of those tribes, as their people moved to a modern diet and lifestyle, the health advantages disappeared, the populations quickly rising to obesity, cancer, stroke and heart attack rates on par with any other group’s.

An increasing body of research bears out the obvious conclusion: eating and living the way our bodies were evolved to makes us leaner, fitter, and less susceptible to chronic disease. But what exactly were we evolved to eat and do? Check back for part two, “Eat Like a Caveman” for a look at the food end of the equation.