Newly popular in health circles, the Paleo diet was created back in the 1970s by gastroenterologist Walter Voegtlin. He was the first to suggest that eating like our Paleolithic ancestors could make modern humans healthier. A return to the diet of our forebears, according to Voegtlin and scores of other doctors and nutritionists after him, could sharply reduce incidences of Crohn’s disease, diabetes, obesity and indigestion, among other ailments. But how does our modern take on the Paleo diet compare to what our ancestors actually ate?

At first glance, the Paleo diet does have a lot of things in common with what the actual Paleolithic man would have eaten. The diet is comprised mainly of meats and fish that could have been hunted by prehistoric man, and plant matter that would have been gathered, including nuts, seeds, vegetables and fruits. All grains and processed flours are avoided, as the prehistoric age predated crop cultivation. Dairy products are off-limits—early man didn’t raise animals for meat or milk. Honey is the only sugar that’s allowed on the diet, as refined sugar as we know it didn’t exist. And salt intake is limited, since our ancestors didn’t exactly have salt shakers at the ready 20,000 years ago. Processed foods in any form are forbidden, and meat is supposed to be grass fed, as that more closely resembles the natural diet of roaming animals.

But critics claim that the Paleo diet dramatically oversimplifies what prehistoric man ate. While the Paleo diet emphasizes meat and fish, it’s not clear that proteins formed the majority of actual prehistoric diets. As with our modern eating habits, diets in the Paleolithic era would have varied wildly according to location. Groups who settled in desert locales would have had no access to fish and probably little meat to eat. Nuts, seeds and even insects would have played a large part in their diets. Groups living in colder areas had little access to fresh vegetables or fruits. Their diet would have been almost exclusively meat-based, and they would eat all parts of the animal to make up for dietary deficiencies caused by the lack of fresh produce. Critics note that modern Paleo diets don’t take these details into account.

The most controversial aspect of the Paleo diet, however, are the claims its proponents make about its ability to improve overall health. While most Americans would certainly benefit from consuming more fruits and vegetables, it’s difficult to prove that prehistoric man was somehow healthier than his modern counterparts. After all, most children died before the age of 15, and only rarely did adults reach past 40. And a recent study in The Lancet revealed alarmingly high rates of atherosclerosis, or hardened arteries, in ancient mummies—47 of the 137 mummies studied were suspected of having the disease, casting doubt on the theory that our forbearers had much healthier diets than we do now.

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