In their present form, humans have existed for about 300,000 generations; that is, about six million years. By far during the largest part of this time, our ancestors lived as hunters and collectors, because only about 500 generations ago did agriculture appear. Genetically the human being of the present differs very little from those of prehistoric times; that is, the physiological and biochemical processes of our bodies are still optimally adapted to the conditions of living and nutrition prevalent in the Stone Age, or Paleolithic era. However, the diet of the Stone Age man differed significantly from that of the present. Our ancestors mainly ate wild animals and harvested fruits, leaves, nuts and seeds. The very high portion of fruits and leaves in particular in the diet -- which we know as fruit, vegetables and salad -- supplied primitive humans with a very large quantity of micronutrients.