Food is essential to life. Its main role is to nourish the body. That's how important it is to our health. Food choices depend on many factors: culture, social environment, income, food availability and personal taste, as well as our natural and original genetic make-up. Food is therefore a subject that touches on many aspects of life. This document does not pretend to cover the whole planet. It does, however, offer a quick overview of WHO EATS WHAT, WHO EATS WHO AND WHY?The aim of this book is to help medical professionals and all our readers understand the concept of the ecosystem, human dietary behaviour in the light of historical evolution from the first primates to modern man, and the advantages and disadvantages of certain diets adopted by humans, in order to make the right choice when it comes to nutrition.