Some diets discourage seed consumption. Paleolithic diet followers reason that before agriculture, seeds were not abundant enough to have been a significant food source, and/or for seeds to have been a food source they would have to be ground and cooked. Our human ancestors may not have been grinding and cooking 2.6 million years ago, or even (depending on who you read) 250,000 years ago.
If it's true that our human ancestors did not consume many seeds, or that the seeds they did consume were not ground and cooked, it's also likely that our human ancestors did not consume much extracted seed oil.
Oils are a processed food - not the oils present in food in its natural state, but oils that have been mechanically, chemically, or thermally extracted. Most seed oils are high in polyunsaturated fat (PUFA) and contain relatively high amounts of inflammation-promoting omega-6 PUFA. If our ancestors weren't eating much seed oil, they probably weren't eating much PUFA.
Ironically, one thing the popular meat-based Stone Age diets and the plant-based low-fat diets of Esselstyne and McDougall have in common is their avoidance of oils. Neither of these diets contain concentrated sources of omega-6-rich polyunsaturated oil. And both of these diets claim to defend against "diseases of civilization."