Paleolithic Era 100,000 years ago
 

Fish provide an unusually high quality source of essential oils that contain critical nutrients for the development of brain tissue. Because oil has a higher caloric density than carbohydrate or protein it also represents a superior energy source.

Large brains require lots of energy and access to fish allowed prehistoric man to develop and power progressively larger brains. These larger brains allowed more complex thinking and led to the development of large coordinated tribes, language, tools, weapons, etc. All the good stuff that made us what we are today. Scientists are confident this occurred because fish bones are commonly found co-located with all really ancient fossils along the human evolutionary line and all the centers of early human development are close to bodies of water.