If you look to the North you will find the Inuit who until the rest of us came along and "civilised" them ate only what was seasonally available. For most of the year that was seal/walrus/whale meat, organs, and fat/blubber, fish at other times, and at others, greens and berries. Inland they might get Caribou and some greens by eating their stomachs. Food was barely if ever cooked. From what I understand, they had little to no incidence of CVD, or Type 2 Diabetes... both of which genetically they are very prone... as they found out as soon as they started eating from Canada's Food Guide
If I were a scientist looking into the best practices for healthy eating I might be asking the Inuit elders a few questions
