That's the opening statement from Caveman cuisine, an article by nutritionists Mary Enig and Sally Fallon on Weston A Price Foundation website. Dr. Price discovered on his travels back in the 1930s that all healthy indigenous people had a plentiful source of animal fat in their diet.
However the obvious lack of direct evidence about our Paleolithic ancestors allows conjecture about the content of their diets. The low fat school claims that cave men ate lean meat, supplemented by plant foods. Dissenting investigators assert that they imbibed animal fats first and foremost, along with the meat that it was attached, and not too many vegetables.
Dr. Walter L Voegtlin argues for the high fat model in his book The Stone Age Diet, published in 1975. He asserts that the Stone Age diet was that of a carnivore - chiefly fats and protein, with only small amounts of carbohydrates.
In 1988, Dr. S. Boyd Eaton published The Paleolithic Prescription in which he argues that the cave man diet was low in fat (particularly saturated fat), low in salt and rich in dietary fiber from plant foods.
Nowadays a popular endurance sports coach Joe Friel (who co-authored The Paleo Diet for Athletes with like-minded Loren Cordain) translates these suppositions into the following recommendations: select the leanest cuts of meat, trim away all visible fat, include fish and fowl, eat low-fat dairy products and include moderate amounts of monounsaturated fat in the form of nuts, avocado, and olive oil.
Enig and Fallon conclude that eventually the high-fat proponents are the most likely winners of the great Paleolithic fat debate. The amount of plant food in the cave man diet naturally varied greatly according to the climate and locality. In arctic climates plant foods were minimal, but they played a large role in the tropical regions where nuts provided additional fat.