Much of the scholarly literature suggests that humans evolved on a diet with a ratio of omega-6 to omega-3 of about 1. However, in the Western diet, it is currently estimated that this ratio sits much closer to 16:1. Meaning that for every 16 grams of Omega 6 people in the Western World consume, they are only consuming about a gram of essential Omega-3s.
Nutrition plays an extremely vital role in the development of the human body, and at the core of our nutritional requirements is our DNA. Scientists estimate that the rate of spontaneous DNA mutation (evolutionary changes) occurs at about 0.5% per 1 million years. However, the Agricultural Revolution occurred during a period of only the last 10,000 years. As a result, our genetic makeup has not yet had the time to adjust to the drastic changes in our nutrition and environment. The simple fact is that our current genes are extremely similar to that of our Paleolithic ancestors living 40,000 years ago. However, our diet is drastically different, and much of these differences are in the areas of essential fatty acids and antioxidant capacity of foods. (Importance of the Ratio of Omega–6/Omega–3 Essential Fatty Acids: Evolutionary Aspects)
Most research now points to the detrimental effect of such a significant dietary change. These effects include the promotion of pathogenesis of many health issues: items like cancer, cardiovascular disease (heart, arteries, etc.), inflammatory diseases and autoimmune diseases.
All this data when combined with the fact that Americans have the greatest proportion of cardiovascular disease in developed countries, really makes you wonder how strong the impact of this ratio could really be.