Humans' "remarkable ability" to find and process many types of food is what probably led to the tremendous diversity of healthy diets across the globe, Leonard said.
The flip side is that many people today have shifted to a more sedentary lifestyle than that of our hunter-gatherer ancestors.
We continue to consume many calories, but we don't get nearly as much exercise as early humans.
"We're a victim of our evolutionary successes," Leonard said.
Diet and Exercise
Some studies suggest that a return to ancient lifestyles could clear up "diseases of civilization," Leonard said.
One paper, for example, shows that putting diabetic Australian Aborigines on the diets of their ancestors reverses their diabetes in just seven weeks.
Likewise, researchers have put pedometers on members of hunter-gatherer groups that have maintained the same ranges for thousands of years. Those studies found that these people all walk roughly the same amount a day: about 8 miles (13 kilometers).
That's "remarkably close" to many government initiatives that recommend a daily walking allowance of about 6 miles (9.6 kilometers), Leonard said—lending credence to the idea that an ancient lifestyle could be the healthiest.
That's not to say that popular manifestations of the idea, such as movements touting "paleodiets," are going to be weight-loss miracles.
"Many of the popular books written on the topic are foolish and others are potentially dangerous," Leonard warned.
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