Hunter-gatherer diets have long been a topic of interest and speculation (1–3). In this issue of the Journal, Cordain et al (4) attempt to estimate likely macronutrient intakes from plant and animal foods in the diets of “recent” (largely 20th century) hunter-gatherers. They conclude that most such societies likely derived more than half of their subsistence energy from animal foods and that because wild plant foods have a relatively low carbohydrate content, protein intake was elevated at the expense of carbohydrate (4).
Some societies coded as hunter-gatherers in the Atlas probably were not exclusively hunter-gatherers or were displaced agricultural peoples. Data on modern-day hunter-gatherers as well as hunter-gatherer-agriculturalists who consumed traditional diets indicate that such societies are largely free of diseases of civilization regardless of whether a high percentage of dietary energy is supplied by wild animal foods (eg, in Canadian Eskimos), wild plant foods (eg, in the !Kung), or domesticated plant foods taken primarily from a single cultivar (eg, in the Yanomamo) (7–11).
Furthermore, although humans can thrive on a diversity of diets, we know of few specific genetic adaptations to diet in our species. Humans come from a fairly generalized line of higher primates, a lineage able to utilize a wide range of plant and animal foods. Modern human nutritional requirements (eg, the need for a dietary source of vitamin C), features of the modern human gut (haustrated colon), and the modern human pattern of digestive kinetics (similar to that of great apes) suggest an ancestral past in which tropical plant foods formed the basis of the daily diet, with perhaps some opportunistic intake of animal matter.
Because humans initially evolved in Africa, where wild animals generally lack appreciable fat stores (2), it seems clear that they consumed a mixed diet of animal and plant foods, given the apparent limitations of human digestive physiology to secure adequate daily energy from protein sources alone (4).
It does, however, indicate that humans can thrive on extreme diets as long as these diets contribute the full range of essential nutrients.
Hunter-gatherer societies in other environments were doubtless eating very different diets, depending on the season and types of resources available. Animal foods are estimated to contribute 33% and plant foods 67% of their daily energy intakes (1). Similarly, the hunter-gatherer Hazda of Tanzania consume “the bulk of their diet” as wild plants, although they live in an area with an exceptional abundance of game animals and refer to themselves as hunters (18). Some hunter-gatherer societies in Papua New Guinea relied heavily on starch from wild sago palms as an important source of energy (21), whereas most hunter-gatherer societies in California depended heavily on acorn foods from wild oaks (22).
These and similar data indicate that hunter-gatherer societies typically did not rely on many wild plant species specifically for energy. Animal foods typically are hard to capture but food such as tree fruits and grass seeds are relatively reliable, predictable dietary elements. Furthermore, humans come from an ancestral lineage in which plant foods traditionally have served as the primary source of energy (14, 15). Societies consuming a staple cultivar as well as wild foods likewise may have limited energy intakes because most cultivars lack many essential nutrients, necessitating the inclusion of other foods in the diet, and some are high in fiber (eg, cassava).
Because the human gut can hold only a limited amount of food and as the transit time of food through the human gut is protracted (averaging 62 h with low-fiber diets and 40 h with high-fiber diets), there is a clear upper threshold for the amount of such foods the human gut can process per day (14). In the natural environment, energy-dense, highly digestible foods of any type are generally rare.
The best-known hunter-gatherer's diet is called the Paleo Diet.
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The diet disallows all processed foods, cereals, legumes and dairy, notes Bowden. You get fat by eating foods that are not suited to your genes and digestive system, according to the theory behind the diet. The advent of many modern diseases coincides with dietary changes, say diet advocates. The Paleo Diet does have some drawbacks.
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