For detailed information on what is the Paleo Diet, there is an abundance of information available on the internet. It is also called the Caveman or Paleolithic Diet. The logic behind it is the fact that our prehistoric ancestors thrived on it.
The Paleolithic Period is a geologic time frame extended from around 2.6 million years ago to the end of the Pleistocene Epoch around 12 thousand years BP (Before Present, also known as Before Physics). In archaeological terms, this Period coincided with the Stone Age. During this time, humans gathered together into units known as bands of roughly thirty to fifty people. They subsisted by scavenging or hunting wild animals and by gathering plants.
Our early ancestors ate fruits, vegetables, seeds, fish, roots, nuts and meat from animals raised on a pasture and fed grass. They did not eat legumes, grains, salt, dairy products, refined sugars or heavily processed foods. The rationale behind this is that the prehistoric diet was feeding a human digestive system that was ideally evolved for it.
Since the end of the Paleolithic Age, our dentition and digestion have remained the same while it is our eating habits that have evolved, some would say deteriorated. There are, however, experts who think it is the fact that cave men ate fewer calories and got a lot more exercise that explains why they may have been so much healthier than the couch potatoes of today.
Dairy foods (milk, cheese, butter, yoghurt) and cereal grains (rye, corn, oats, rice, wheat) were notably absent from paleolithic menus. The end of the Paleolithic saw a dramatic fall in both human health and body mass. There are those who believe this was the result of introducing cereal grains onto the dinner plate.
Another noteworthy omission from the ancestral fridge was dairy. It was not until the Neolithic Revolution (10,000-7,000 BP) that we began drinking milk. The genetic ability to process the milk sugar, lactose, turned up in Northern Europe, a part of the world not known for abundant sunshine, the normal source of Vitamin D. It is thought that this conferred a selective advantage on people living in that gloomy part of the world. Enter lactose tolerance into the general gene pool.
What is the Paleo Diet mimics from our impression of what our early ancestors were eating to stay alive. The few formal studies that have been conducted so far indicate that there is a definite advantage in following this regime. It is recommended for those that are considering trying this to first consult their regular medical professional.