Nature and variability of human food consumption.

The early human diet was characteristically extremely varied, and a wide range of plant species and plant organs were consumed. Foods of animal origin included those taken opportunistically, such as invertebrates, amphibians, reptiles, small mammals, birds and their eggs, and the scavenging and hunting of larger mammals. Each of these types of food have characteristic nutritional compositions. Comparison of these compositional features shows that an adequate diet could be obtained in many different ways. The selection of food providing fat had substantial advantages in reducing the amount of plant foods to be gathered, in the satiety provided and in supplying essential micronutrients. Obtaining adequate water and energy would probably be the main physiological drives. Many plant foods contain natural toxicants, and would only have been suitable as major items in the diet once cooking had been developed, and the preference for sweet tastes would have protected humans from eating bitter, toxic plants.