Our digestive system evolved over many millions of years to match the lifestyle of our ancestors, who hunted for meat or fish, and gathered seeds, fruits, roots and berries.
The change in our ancestors' way of life to an agricultural and then industrial lifestyle has been so quick that the power of evolution to match the way our body works to the way we live has not yet had time to operate. We still have a digestive system designed to match millions of years of a hunter-gatherer existence.
Our bodies are designed to work their best using a variety of different types of food.
Animals like the cow, which evolved to eat only vegetable food, have developed a series of pouches, or extra stomachs, to separate one meal from the next. As digestion progresses food is moved from one to the next, or even brought back to the mouth for a further chew.