Deep Roots of the Human Diet
Most evidence supports the idea that human type beings began branching off from arboreal apes in tropical Africa something like 5,000,000 years ago. Genetically we are most like modern chimpanzees. Chimpanzees have evolved with a diet that is based largely on ripe and unripe fruit, piths from plant stems and leaves, with relatively small amounts of bird eggs, insect larvae and meat from small mammals. Humans expanded somewhat on that diet adding more meat from group hunting and more roots.
For over 99 % of our time on earth humans lived as small bands of opportunistic omnivores hunting and gathering a highly varied diet comprised mainly of hundreds of species of plants, small animals, and insects. Food, the exchanging of life energy among organisms, was likely an intense and intimate experience. We know that our native diet included plenty of fresh fruits and vegetables because we lack the ability to synthesize the critical antioxidant, vitamin C. The few other species that lack this ability, including chimpanzees, guinea pigs and fruit bats, all have diets so rich in fresh vegetables and fruits, that the ability to make this key nutrient internally became redundant. Most paleo-nutrition experts think that we ate far more food from plants than from animals, because plant food sources are almost always more abundant and more easily obtained. This is reflected in estimates that early diets contained roughly 100 grams per day of fiber, compared to 10-20 grams that is typical in the US today.
Around 40,000 years ago the use of controlled fire for cooking led to improved nutrition. We became able to derive more food value from the same foods by detoxifying many plant foods (i.e. phytic acid and trypsin inhibitors in grass and legume seeds), and by reducing the load of intestinal parasites found in meat. Cooking also made many plant foods more useful in our diet because the heat caused the tough cell walls to rupture and allowed us access to the nutritious cellular contents.
Remnant hunter/gatherers living in difficult terrains such as the Kalahari Desert and the Amazon Rainforest are acutely aware of their environment and able to obtain a reasonably adequate diet from it in an hour or two of work each day. There is little motive for hunter/gatherers to intensify their quest for food by working harder because the availability of desirable game and plant food within walking distance is limited. Hunting beyond the carrying capacity of the land would quickly diminish the future food supplies of the area. Although early humans certainly had an impact on our environment and probably hunted a few species to extinction, this basic economic reality allowed us to live for many thousands of years without seriously depleting the ecological capital of our homelands.