Among the necessary fats are omega three fatty acids. These are though to be one of the main limiting nutrients in brain growth and development.
These days our food is often fortified with omega three fats. However, in the ancestral environment, good sources of these fats were not so easy to come by. Probably most of our more recent ancestors obtained many of their omega three fats by eating other animals. They hunted them with the assistance of spears, gutted them with the assistance of knives, and cooked them with the assistance of fire. Memes contributed at every stage to feeding those ancestral brains stoked with the fats the memes needed to sustain themselves.
The idea that human evolution was facilitated by lifting nutrient constraints is the theme of the book The Driving Force: Food, Evolution and the Future by Michael Crawford and David Marsh.
Humans are water-friendly apes. They fish and eat seafood. Various explanations have been offered for this, but the most obvious one is that humans acquired memetic adaptations to watery environments - involving swimming, fishing and seafood consumption. No doubt the added seafood helped provide the resources to fuel the development of the brains of our ancestors.