Thanks to Stephan Guyenet for bringing the study n-6 Fatty acid-specific and mixed polyunsaturate dietary interventions have different effects on CHD risk: a meta-analysis of randomised controlled trials to my attention in his post Diet-Heart Controlled Trials: a New Literature Review. This shows that diets high in omega-6 (n-6) polyunsaturates but low in omega-3 (n-3) polyunsaturates are heart-unhealthy.
In the West, we are advised to eat lots of "heart-healthy" sunflower oil & spreads. These contain about 70 times more omega-6 than omega-3. Safflower, Grapeseed, Corn & Groundnut Oils also have high omega-6:omega-3 ratios, according to Comparison of Dietary Fats Chart.
I then found the following study also on the British Journal of Nutrition:- Estimated macronutrient and fatty acid intakes from an East African Paleolithic diet.
This shows that traditional hunter-gatherer diets have a short-chain omega-3:omega-6 ratio of 1·12–1·64 and a long-chain omega-3:omega-6 ratio of 0·84–1·92. In other words, there is a moderate balance between omega-6 and omega-3 polyunsaturates.
The diets are also relatively high in protein (25–29% energy) and fat (30–39% energy) but moderate in carbohydrate (39–40% energy).
I thought that followers of a Paleo-type diet would find this interesting.
EDIT: I've just noticed that O Primitivo has already posted about this study!