Do dietary monounsaturated fatty acids play a protective role in carcinogenesis and cardiovascular disease?

Evidence gleaned from epidemiology, nutritional anthropology, and laboratory animal studies is cited to support the hypothesis that the metabolism of 20th century man is poorly adapted to the present day high-fat, high-saturated fat Western diet, and that the emergence of heart disease and cancer as the major killing diseases in modern industrial societies may have resulted, at least in part, from the inability of our ancient metabolic heritage, adapted over eons to a low-fat, high-monounsaturated fat diet, to cope with our modern Western diet--a diet of unusually high caloric density that appeared only recently (approximately 250 years ago) in the 100,000+ year evolutionary history of Homo sapiens.